draft-ietf-anima-bootstrapping-keyinfra-45.txt   rfc8995.txt 
ANIMA WG M. Pritikin Internet Engineering Task Force (IETF) M. Pritikin
Internet-Draft Cisco Request for Comments: 8995 Cisco
Intended status: Standards Track M. Richardson Category: Standards Track M. Richardson
Expires: 15 May 2021 Sandelman ISSN: 2070-1721 Sandelman Software Works
T.T.E. Eckert T. Eckert
Futurewei USA Futurewei USA
M.H. Behringer M. Behringer
K.W. Watsen K. Watsen
Watsen Networks Watsen Networks
11 November 2020 May 2021
Bootstrapping Remote Secure Key Infrastructures (BRSKI) Bootstrapping Remote Secure Key Infrastructure (BRSKI)
draft-ietf-anima-bootstrapping-keyinfra-45
Abstract Abstract
This document specifies automated bootstrapping of an Autonomic This document specifies automated bootstrapping of an Autonomic
Control Plane. To do this a Secure Key Infrastructure is Control Plane. To do this, a Secure Key Infrastructure is
bootstrapped. This is done using manufacturer-installed X.509 bootstrapped. This is done using manufacturer-installed X.509
certificates, in combination with a manufacturer's authorizing certificates, in combination with a manufacturer's authorizing
service, both online and offline. We call this process the service, both online and offline. We call this process the
Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol. Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol.
Bootstrapping a new device can occur using a routable address and a Bootstrapping a new device can occur when using a routable address
cloud service, or using only link-local connectivity, or on limited/ and a cloud service, only link-local connectivity, or limited/
disconnected networks. Support for deployment models with less disconnected networks. Support for deployment models with less
stringent security requirements is included. Bootstrapping is stringent security requirements is included. Bootstrapping is
complete when the cryptographic identity of the new key complete when the cryptographic identity of the new key
infrastructure is successfully deployed to the device. The infrastructure is successfully deployed to the device. The
established secure connection can be used to deploy a locally issued established secure connection can be used to deploy a locally issued
certificate to the device as well. certificate to the device as well.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 15 May 2021.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction
1.1. Prior Bootstrapping Approaches . . . . . . . . . . . . . 6 1.1. Prior Bootstrapping Approaches
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 8 1.2. Terminology
1.3. Scope of solution . . . . . . . . . . . . . . . . . . . . 11 1.3. Scope of Solution
1.3.1. Support environment . . . . . . . . . . . . . . . . . 11 1.3.1. Support Environment
1.3.2. Constrained environments . . . . . . . . . . . . . . 11 1.3.2. Constrained Environments
1.3.3. Network Access Controls . . . . . . . . . . . . . . . 12 1.3.3. Network Access Controls
1.3.4. Bootstrapping is not Booting . . . . . . . . . . . . 12 1.3.4. Bootstrapping is Not Booting
1.4. Leveraging the new key infrastructure / next steps . . . 12 1.4. Leveraging the New Key Infrastructure / Next Steps
1.5. Requirements for Autonomic Network Infrastructure (ANI) 1.5. Requirements for Autonomic Networking Infrastructure (ANI)
devices . . . . . . . . . . . . . . . . . . . . . . . . . 13 Devices
2. Architectural Overview . . . . . . . . . . . . . . . . . . . 13 2. Architectural Overview
2.1. Behavior of a Pledge . . . . . . . . . . . . . . . . . . 15 2.1. Behavior of a Pledge
2.2. Secure Imprinting using Vouchers . . . . . . . . . . . . 16 2.2. Secure Imprinting Using Vouchers
2.3. Initial Device Identifier . . . . . . . . . . . . . . . . 17 2.3. Initial Device Identifier
2.3.1. Identification of the Pledge . . . . . . . . . . . . 18 2.3.1. Identification of the Pledge
2.3.2. MASA URI extension . . . . . . . . . . . . . . . . . 19 2.3.2. MASA URI Extension
2.4. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . 20 2.4. Protocol Flow
2.5. Architectural Components . . . . . . . . . . . . . . . . 23 2.5. Architectural Components
2.5.1. Pledge . . . . . . . . . . . . . . . . . . . . . . . 23 2.5.1. Pledge
2.5.2. Join Proxy . . . . . . . . . . . . . . . . . . . . . 23 2.5.2. Join Proxy
2.5.3. Domain Registrar . . . . . . . . . . . . . . . . . . 23 2.5.3. Domain Registrar
2.5.4. Manufacturer Service . . . . . . . . . . . . . . . . 23 2.5.4. Manufacturer Service
2.5.5. Public Key Infrastructure (PKI) . . . . . . . . . . . 24 2.5.5. Public Key Infrastructure (PKI)
2.6. Certificate Time Validation . . . . . . . . . . . . . . . 24 2.6. Certificate Time Validation
2.6.1. Lack of realtime clock . . . . . . . . . . . . . . . 24 2.6.1. Lack of Real-Time Clock
2.6.2. Infinite Lifetime of IDevID . . . . . . . . . . . . . 24 2.6.2. Infinite Lifetime of IDevID
2.7. Cloud Registrar . . . . . . . . . . . . . . . . . . . . . 25 2.7. Cloud Registrar
2.8. Determining the MASA to contact . . . . . . . . . . . . . 25 2.8. Determining the MASA to Contact
3. Voucher-Request artifact . . . . . . . . . . . . . . . . . . 26 3. Voucher-Request Artifact
3.1. Nonceless Voucher Requests . . . . . . . . . . . . . . . 27 3.1. Nonceless Voucher-Requests
3.2. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 27 3.2. Tree Diagram
3.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . 27 3.3. Examples
3.4. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 29 3.4. YANG Module
4. Proxying details (Pledge - Proxy - Registrar) . . . . . . . . 33 4. Proxying Details (Pledge -- Proxy -- Registrar)
4.1. Pledge discovery of Proxy . . . . . . . . . . . . . . . . 34 4.1. Pledge Discovery of Proxy
4.1.1. Proxy GRASP announcements . . . . . . . . . . . . . . 35 4.1.1. Proxy GRASP Announcements
4.2. CoAP connection to Registrar . . . . . . . . . . . . . . 37 4.2. CoAP Connection to Registrar
4.3. Proxy discovery and communication of Registrar . . . . . 37 4.3. Proxy Discovery and Communication of Registrar
5. Protocol Details (Pledge - Registrar - MASA) . . . . . . . . 38 5. Protocol Details (Pledge -- Registrar -- MASA)
5.1. BRSKI-EST TLS establishment details . . . . . . . . . . . 40 5.1. BRSKI-EST TLS Establishment Details
5.2. Pledge Requests Voucher from the Registrar . . . . . . . 41 5.2. Pledge Requests Voucher from the Registrar
5.3. Registrar Authorization of Pledge . . . . . . . . . . . . 43 5.3. Registrar Authorization of Pledge
5.4. BRSKI-MASA TLS establishment details . . . . . . . . . . 43 5.4. BRSKI-MASA TLS Establishment Details
5.4.1. MASA authentication of customer Registrar . . . . . . 44 5.4.1. MASA Authentication of Customer Registrar
5.5. Registrar Requests Voucher from MASA . . . . . . . . . . 45 5.5. Registrar Requests Voucher from MASA
5.5.1. MASA renewal of expired vouchers . . . . . . . . . . 47 5.5.1. MASA Renewal of Expired Vouchers
5.5.2. MASA pinning of registrar . . . . . . . . . . . . . . 48 5.5.2. MASA Pinning of Registrar
5.5.3. MASA checking of voucher request signature . . . . . 48 5.5.3. MASA Check of the Voucher-Request Signature
5.5.4. MASA verification of domain registrar . . . . . . . . 49 5.5.4. MASA Verification of the Domain Registrar
5.5.5. MASA verification of pledge 5.5.5. MASA Verification of the Pledge
prior-signed-voucher-request . . . . . . . . . . . . 50 'prior-signed-voucher-request'
5.5.6. MASA nonce handling . . . . . . . . . . . . . . . . . 50 5.5.6. MASA Nonce Handling
5.6. MASA and Registrar Voucher Response . . . . . . . . . . . 50 5.6. MASA and Registrar Voucher Response
5.6.1. Pledge voucher verification . . . . . . . . . . . . . 53 5.6.1. Pledge Voucher Verification
5.6.2. Pledge authentication of provisional TLS 5.6.2. Pledge Authentication of Provisional TLS Connection
connection . . . . . . . . . . . . . . . . . . . . . 54 5.7. Pledge BRSKI Status Telemetry
5.7. Pledge BRSKI Status Telemetry . . . . . . . . . . . . . . 55 5.8. Registrar Audit-Log Request
5.8. Registrar audit-log request . . . . . . . . . . . . . . . 56 5.8.1. MASA Audit-Log Response
5.8.1. MASA audit log response . . . . . . . . . . . . . . . 58 5.8.2. Calculation of domainID
5.8.2. Calculation of domainID . . . . . . . . . . . . . . . 60 5.8.3. Registrar Audit-Log Verification
5.8.3. Registrar audit log verification . . . . . . . . . . 61 5.9. EST Integration for PKI Bootstrapping
5.9. EST Integration for PKI bootstrapping . . . . . . . . . . 62 5.9.1. EST Distribution of CA Certificates
5.9.1. EST Distribution of CA Certificates . . . . . . . . . 63 5.9.2. EST CSR Attributes
5.9.2. EST CSR Attributes . . . . . . . . . . . . . . . . . 63 5.9.3. EST Client Certificate Request
5.9.3. EST Client Certificate Request . . . . . . . . . . . 64 5.9.4. Enrollment Status Telemetry
5.9.4. Enrollment Status Telemetry . . . . . . . . . . . . . 64 5.9.5. Multiple Certificates
5.9.5. Multiple certificates . . . . . . . . . . . . . . . . 65 5.9.6. EST over CoAP
5.9.6. EST over CoAP . . . . . . . . . . . . . . . . . . . . 66 6. Clarification of Transfer-Encoding
6. Clarification of transfer-encoding . . . . . . . . . . . . . 66 7. Reduced Security Operational Modes
7. Reduced security operational modes . . . . . . . . . . . . . 66 7.1. Trust Model
7.1. Trust Model . . . . . . . . . . . . . . . . . . . . . . . 66 7.2. Pledge Security Reductions
7.2. Pledge security reductions . . . . . . . . . . . . . . . 67 7.3. Registrar Security Reductions
7.3. Registrar security reductions . . . . . . . . . . . . . . 68 7.4. MASA Security Reductions
7.4. MASA security reductions . . . . . . . . . . . . . . . . 69 7.4.1. Issuing Nonceless Vouchers
7.4.1. Issuing Nonceless vouchers . . . . . . . . . . . . . 69 7.4.2. Trusting Owners on First Use
7.4.2. Trusting Owners on First Use . . . . . . . . . . . . 70 7.4.3. Updating or Extending Voucher Trust Anchors
7.4.3. Updating or extending voucher trust anchors . . . . . 71 8. IANA Considerations
8.1. The IETF XML Registry
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 72 8.2. YANG Module Names Registry
8.1. The IETF XML Registry . . . . . . . . . . . . . . . . . . 72 8.3. BRSKI Well-Known Considerations
8.2. YANG Module Names Registry . . . . . . . . . . . . . . . 72 8.3.1. BRSKI .well-known Registration
8.3. BRSKI well-known considerations . . . . . . . . . . . . . 72 8.3.2. BRSKI .well-known Registry
8.3.1. BRSKI .well-known registration . . . . . . . . . . . 72 8.4. PKIX Registry
8.3.2. BRSKI .well-known registry . . . . . . . . . . . . . 73 8.5. Pledge BRSKI Status Telemetry
8.4. PKIX Registry . . . . . . . . . . . . . . . . . . . . . . 73 8.6. DNS Service Names
8.5. Pledge BRSKI Status Telemetry . . . . . . . . . . . . . . 73 8.7. GRASP Objective Names
8.6. DNS Service Names . . . . . . . . . . . . . . . . . . . . 74 9. Applicability to the Autonomic Control Plane (ACP)
8.7. GRASP Objective Names . . . . . . . . . . . . . . . . . . 74 9.1. Operational Requirements
9. Applicability to the Autonomic Control Plane (ACP) . . . . . 74 9.1.1. MASA Operational Requirements
9.1. Operational Requirements . . . . . . . . . . . . . . . . 76 9.1.2. Domain Owner Operational Requirements
9.1.1. MASA Operational Requirements . . . . . . . . . . . . 76 9.1.3. Device Operational Requirements
9.1.2. Domain Owner Operational Requirements . . . . . . . . 77 10. Privacy Considerations
9.1.3. Device Operational Requirements . . . . . . . . . . . 77 10.1. MASA Audit-Log
10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 78 10.2. What BRSKI-EST Reveals
10.1. MASA audit log . . . . . . . . . . . . . . . . . . . . . 78 10.3. What BRSKI-MASA Reveals to the Manufacturer
10.2. What BRSKI-EST reveals . . . . . . . . . . . . . . . . . 78 10.4. Manufacturers and Used or Stolen Equipment
10.3. What BRSKI-MASA reveals to the manufacturer . . . . . . 79 10.5. Manufacturers and Grey Market Equipment
10.4. Manufacturers and Used or Stolen Equipment . . . . . . . 81 10.6. Some Mitigations for Meddling by Manufacturers
10.5. Manufacturers and Grey market equipment . . . . . . . . 83 10.7. Death of a Manufacturer
10.6. Some mitigations for meddling by manufacturers . . . . . 83 11. Security Considerations
10.7. Death of a manufacturer . . . . . . . . . . . . . . . . 84 11.1. Denial of Service (DoS) against MASA
11. Security Considerations . . . . . . . . . . . . . . . . . . . 85 11.2. DomainID Must Be Resistant to Second-Preimage Attacks
11.1. Denial of Service (DoS) against MASA . . . . . . . . . . 86 11.3. Availability of Good Random Numbers
11.2. DomainID must be resistant to second-preimage attacks . 86 11.4. Freshness in Voucher-Requests
11.3. Availability of good random numbers . . . . . . . . . . 87 11.5. Trusting Manufacturers
11.4. Freshness in Voucher-Requests . . . . . . . . . . . . . 87 11.6. Manufacturer Maintenance of Trust Anchors
11.5. Trusting manufacturers . . . . . . . . . . . . . . . . . 88 11.6.1. Compromise of Manufacturer IDevID Signing Keys
11.6. Manufacturer Maintenance of trust anchors . . . . . . . 89 11.6.2. Compromise of MASA Signing Keys
11.6.1. Compromise of Manufacturer IDevID signing keys . . . 91 11.6.3. Compromise of MASA Web Service
11.6.2. Compromise of MASA signing keys . . . . . . . . . . 91 11.7. YANG Module Security Considerations
11.6.3. Compromise of MASA web service . . . . . . . . . . . 93 12. References
11.7. YANG Module Security Considerations . . . . . . . . . . 94 12.1. Normative References
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 94 12.2. Informative References
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 94 Appendix A. IPv4 and Non-ANI Operations
13.1. Normative References . . . . . . . . . . . . . . . . . . 94 A.1. IPv4 Link-Local Addresses
13.2. Informative References . . . . . . . . . . . . . . . . . 98 A.2. Use of DHCPv4
Appendix A. IPv4 and non-ANI operations . . . . . . . . . . . . 102 Appendix B. mDNS / DNS-SD Proxy Discovery Options
A.1. IPv4 Link Local addresses . . . . . . . . . . . . . . . . 102 Appendix C. Example Vouchers
A.2. Use of DHCPv4 . . . . . . . . . . . . . . . . . . . . . . 102 C.1. Keys Involved
Appendix B. mDNS / DNSSD proxy discovery options . . . . . . . . 102 C.1.1. Manufacturer Certification Authority for IDevID
Appendix C. Example Vouchers . . . . . . . . . . . . . . . . . . 103 Signatures
C.1. Keys involved . . . . . . . . . . . . . . . . . . . . . . 103 C.1.2. MASA Key Pair for Voucher Signatures
C.1.1. Manufacturer Certificate Authority for IDevID C.1.3. Registrar Certification Authority
signatures . . . . . . . . . . . . . . . . . . . . . 104 C.1.4. Registrar Key Pair
C.1.2. MASA key pair for voucher signatures . . . . . . . . 105 C.1.5. Pledge Key Pair
C.1.3. Registrar Certificate Authority . . . . . . . . . . . 107 C.2. Example Process
C.1.4. Registrar key pair . . . . . . . . . . . . . . . . . 108 C.2.1. Pledge to Registrar
C.1.5. Pledge key pair . . . . . . . . . . . . . . . . . . . 110 C.2.2. Registrar to MASA
C.2. Example process . . . . . . . . . . . . . . . . . . . . . 111 C.2.3. MASA to Registrar
C.2.1. Pledge to Registrar . . . . . . . . . . . . . . . . . 111 Acknowledgements
C.2.2. Registrar to MASA . . . . . . . . . . . . . . . . . . 115 Authors' Addresses
C.2.3. MASA to Registrar . . . . . . . . . . . . . . . . . . 121
Appendix D. Additional References . . . . . . . . . . . . . . . 125
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 125
1. Introduction 1. Introduction
The Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol The Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol
provides a solution for secure zero-touch (automated) bootstrap of provides a solution for secure zero-touch (automated) bootstrap of
new (unconfigured) devices that are called pledges in this document. new (unconfigured) devices that are called "pledges" in this
Pledges have an IDevID installed in them at the factory. document. Pledges have an Initial Device Identifier (IDevID)
installed in them at the factory.
"BRSKI" is pronounced like "brewski", a colloquial term for beer in "BRSKI", pronounced like "brewski", is a colloquial term for beer in
Canada and parts of the US-midwest. [brewski] Canada and parts of the Midwestern United States [brewski].
This document primarily provides for the needs of the ISP and This document primarily provides for the needs of the ISP and
Enterprise focused ANIMA Autonomic Control Plane (ACP) enterprise-focused Autonomic Networking Integrated Model and Approach
[I-D.ietf-anima-autonomic-control-plane]. This bootstrap process (ANIMA) Autonomic Control Plane (ACP) [RFC8994]. This bootstrap
satisfies the [RFC7575] requirements of section 3.3 of making all process satisfies the requirement of making all operations secure by
operations secure by default. Other users of the BRSKI protocol will default per Section 3.3 of [RFC7575]. Other users of the BRSKI
need to provide separate applicability statements that include protocol will need to provide separate applicability statements that
privacy and security considerations appropriate to that deployment. include privacy and security considerations appropriate to that
Section 9 explains the detailed applicability for this the ACP usage. deployment. Section 9 explains the detailed applicability for this
ACP usage.
The BRSKI protocol requires a significant amount of communication The BRSKI protocol requires a significant amount of communication
between manufacturer and owner: in its default modes it provides a between manufacturer and owner: in its default modes, it provides a
cryptographic transfer of control to the initial owner. In its cryptographic transfer of control to the initial owner. In its
strongest modes, it leverages sales channel information to identify strongest modes, it leverages sales channel information to identify
the owner in advance. Resale of devices is possible, provided that the owner in advance. Resale of devices is possible, provided that
the manufacturer is willing to authorize the transfer. Mechanisms to the manufacturer is willing to authorize the transfer. Mechanisms to
enable transfers of ownership without manufacturer authorization are enable transfers of ownership without manufacturer authorization are
not included in this version of the protocol, but could be designed not included in this version of the protocol, but it could be
into future versions. designed into future versions.
This document describes how pledges discover (or are discovered by) This document describes how a pledge discovers (or are discovered by)
an element of the network domain to which the pledge belongs that an element of the network domain that it will belong to and that will
will perform the bootstrap. This element (device) is called the perform its bootstrap. This element (device) is called the
registrar. Before any other operation, pledge and registrar need to "registrar". Before any other operation, the pledge and registrar
establish mutual trust: need to establish mutual trust:
1. Registrar authenticating the pledge: "Who is this device? What 1. Registrar authenticating the pledge: "Who is this device? What
is its identity?" is its identity?"
2. Registrar authorizing the pledge: "Is it mine? Do I want it? 2. Registrar authorizing the pledge: "Is it mine? Do I want it?
What are the chances it has been compromised?" What are the chances it has been compromised?"
3. Pledge authenticating the registrar: "What is this registrar's 3. Pledge authenticating the registrar: "What is this registrar's
identity?" identity?"
4. Pledge authorizing the registrar: "Should I join this network?" 4. Pledge authorizing the registrar: "Should I join this network?"
This document details protocols and messages to answer the above This document details protocols and messages to answer the above
questions. It uses a TLS connection and an PKIX-shaped (X.509v3) questions. It uses a TLS connection and a PKIX-shaped (X.509v3)
certificate (an IEEE 802.1AR [IDevID] IDevID) of the pledge to answer certificate (an IEEE 802.1AR IDevID [IDevID]) of the pledge to answer
points 1 and 2. It uses a new artifact called a "voucher" that the points 1 and 2. It uses a new artifact called a "voucher" that the
registrar receives from a "Manufacturer Authorized Signing Authority" registrar receives from a Manufacturer Authorized Signing Authority
(MASA) and passes to the pledge to answer points 3 and 4. (MASA) and passes it to the pledge to answer points 3 and 4.
A proxy provides very limited connectivity between the pledge and the A proxy provides very limited connectivity between the pledge and the
registrar. registrar.
The syntactic details of vouchers are described in detail in The syntactic details of vouchers are described in detail in
[RFC8366]. This document details automated protocol mechanisms to [RFC8366]. This document details automated protocol mechanisms to
obtain vouchers, including the definition of a 'voucher-request' obtain vouchers, including the definition of a "voucher-request"
message that is a minor extension to the voucher format (see message that is a minor extension to the voucher format (see
Section 3) defined by [RFC8366]. Section 3) as defined by [RFC8366].
BRSKI results in the pledge storing an X.509 root certificate BRSKI results in the pledge storing an X.509 root certificate
sufficient for verifying the registrar identity. In the process a sufficient for verifying the registrar identity. In the process, a
TLS connection is established that can be directly used for TLS connection is established that can be directly used for
Enrollment over Secure Transport (EST). In effect BRSKI provides an Enrollment over Secure Transport (EST). In effect, BRSKI provides an
automated mechanism for the "Bootstrap Distribution of CA automated mechanism for "Bootstrap Distribution of CA Certificates"
Certificates" described in [RFC7030] Section 4.1.1 wherein the pledge described in [RFC7030], Section 4.1.1, wherein the pledge "MUST [...]
"MUST [...] engage a human user to authorize the CA certificate using engage a human user to authorize the CA certificate using out-of-band
out-of-band" information. With BRSKI the pledge now can automate data". With BRSKI, the pledge now can automate this process using
this process using the voucher. Integration with a complete EST the voucher. Integration with a complete EST enrollment is optional
enrollment is optional but trivial. but trivial.
BRSKI is agile enough to support bootstrapping alternative key BRSKI is agile enough to support bootstrapping alternative key
infrastructures, such as a symmetric key solutions, but no such infrastructures, such as a symmetric key solution, but no such system
system is described in this document. is described in this document.
1.1. Prior Bootstrapping Approaches 1.1. Prior Bootstrapping Approaches
To literally "pull yourself up by the bootstraps" is an impossible To literally "pull yourself up by the bootstraps" is an impossible
action. Similarly the secure establishment of a key infrastructure action. Similarly, the secure establishment of a key infrastructure
without external help is also an impossibility. Today it is commonly without external help is also an impossibility. Today, it is
accepted that the initial connections between nodes are insecure, commonly accepted that the initial connections between nodes are
until key distribution is complete, or that domain-specific keying insecure, until key distribution is complete, or that domain-specific
material (often pre-shared keys, including mechanisms like SIM cards) keying material (often pre-shared keys, including mechanisms like
is pre-provisioned on each new device in a costly and non-scalable Subscriber Identification Module (SIM) cards) is pre-provisioned on
manner. Existing automated mechanisms are known as non-secured each new device in a costly and non-scalable manner. Existing
'Trust on First Use' (TOFU) [RFC7435], 'resurrecting duckling' automated mechanisms are known as non-secured "Trust on First Use
[Stajano99theresurrecting] or 'pre-staging'. (TOFU)" [RFC7435], "resurrecting duckling"
[Stajano99theresurrecting], or "pre-staging".
Another prior approach has been to try and minimize user actions Another prior approach has been to try and minimize user actions
during bootstrapping, but not eliminate all user-actions. The during bootstrapping, but not eliminate all user actions. The
original EST protocol [RFC7030] does reduce user actions during original EST protocol [RFC7030] does reduce user actions during
bootstrap but does not provide solutions for how the following bootstrapping but does not provide solutions for how the following
protocol steps can be made autonomic (not involving user actions): protocol steps can be made autonomic (not involving user actions):
* using the Implicit Trust Anchor [RFC7030] database to authenticate * using the Implicit Trust Anchor (TA) [RFC7030] database to
an owner specific service (not an autonomic solution because the authenticate an owner-specific service (not an autonomic solution
URL must be securely distributed), because the URL must be securely distributed),
* engaging a human user to authorize the CA certificate using out- * engaging a human user to authorize the CA certificate using out-
of-band data (not an autonomic solution because the human user is of-band data (not an autonomic solution because the human user is
involved), involved),
* using a configured Explicit TA database (not an autonomic solution * using a configured Explicit TA database (not an autonomic solution
because the distribution of an explicit TA database is not because the distribution of an explicit TA database is not
autonomic), autonomic), and
* and using a Certificate-Less TLS mutual authentication method (not * using a certificate-less TLS mutual authentication method (not an
an autonomic solution because the distribution of symmetric key autonomic solution because the distribution of symmetric key
material is not autonomic). material is not autonomic).
These "touch" methods do not meet the requirements for zero-touch. These "touch" methods do not meet the requirements for zero-touch.
There are "call home" technologies where the pledge first establishes There are "call home" technologies where the pledge first establishes
a connection to a well known manufacturer service using a common a connection to a well-known manufacturer service using a common
client-server authentication model. After mutual authentication, client-server authentication model. After mutual authentication,
appropriate credentials to authenticate the target domain are appropriate credentials to authenticate the target domain are
transferred to the pledge. This creates several problems and transferred to the pledge. This creates several problems and
limitations: limitations:
* the pledge requires realtime connectivity to the manufacturer * the pledge requires real-time connectivity to the manufacturer
service, service,
* the domain identity is exposed to the manufacturer service (this * the domain identity is exposed to the manufacturer service (this
is a privacy concern), is a privacy concern), and
* the manufacturer is responsible for making the authorization * the manufacturer is responsible for making the authorization
decisions (this is a liability concern), decisions (this is a liability concern).
BRSKI addresses these issues by defining extensions to the EST BRSKI addresses these issues by defining extensions to the EST
protocol for the automated distribution of vouchers. protocol for the automated distribution of vouchers.
1.2. Terminology 1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
The following terms are defined for clarity: The following terms are defined for clarity:
ANI: The Autonomic Network Infrastructure as defined by ANI: The Autonomic Networking Infrastructure as defined by
[I-D.ietf-anima-reference-model]. Section 9 details specific [RFC8993]. Section 9 details specific requirements for pledges,
requirements for pledges, proxies and registrars when they are proxies, and registrars when they are part of an ANI.
part of an ANI.
Circuit Proxy: A stateful implementation of the join proxy. This is Circuit Proxy: A stateful implementation of the Join Proxy. This is
the assumed type of proxy. the assumed type of proxy.
drop-ship: The physical distribution of equipment containing the drop-ship: The physical distribution of equipment containing the
"factory default" configuration to a final destination. In zero- "factory default" configuration to a final destination. In zero-
touch scenarios there is no staging or pre-configuration during touch scenarios, there is no staging or preconfiguration during
drop-ship. drop-ship.
Domain: The set of entities that share a common local trust anchor. Domain: The set of entities that share a common local trust anchor.
This includes the proxy, registrar, Domain Certificate Authority, This includes the proxy, registrar, domain CA, management
Management components and any existing entity that is already a components, and any existing entity that is already a member of
member of the domain. the domain.
domainID: The domain IDentity is a unique value based upon the
Registrar CA's certificate. Section 5.8.2 specifies how it is
calculated.
Domain CA: The domain Certification Authority (CA) provides Domain CA: The domain Certification Authority (CA) provides
certification functionalities to the domain. At a minimum it certification functionalities to the domain. At a minimum, it
provides certification functionalities to a registrar and manages provides certification functionalities to a registrar and manages
the private key that defines the domain. Optionally, it certifies the private key that defines the domain. Optionally, it certifies
all elements. all elements.
domainID: The domain IDentity is a unique value based upon the
registrar's CA certificate. Section 5.8.2 specifies how it is
calculated.
enrollment: The process where a device presents key material to a enrollment: The process where a device presents key material to a
network and acquires a network-specific identity. For example network and acquires a network-specific identity. For example,
when a certificate signing request is presented to a certification when a certificate signing request is presented to a CA, and a
authority and a certificate is obtained in response. certificate is obtained in response.
IDevID: An Initial Device Identifier X.509 certificate installed by
the vendor on new equipment. This is a term from 802.1AR
[IDevID].
imprint: The process where a device obtains the cryptographic key imprint: The process where a device obtains the cryptographic key
material to identify and trust future interactions with a network. material to identify and trust future interactions with a network.
This term is taken from Konrad Lorenz's work in biology with new This term is taken from Konrad Lorenz's work in biology with new
ducklings: during a critical period, the duckling would assume ducklings: during a critical period, the duckling would assume
that anything that looks like a mother duck is in fact their that anything that looks like a mother duck is in fact their
mother. An equivalent for a device is to obtain the fingerprint mother. An equivalent for a device is to obtain the fingerprint
of the network's root certification authority certificate. A of the network's root CA certificate. A device that imprints on
device that imprints on an attacker suffers a similar fate to a an attacker suffers a similar fate to a duckling that imprints on
duckling that imprints on a hungry wolf. Securely imprinting is a a hungry wolf. Securely imprinting is a primary focus of this
primary focus of this document [imprinting]. The analogy to document [imprinting]. The analogy to Lorenz's work was first
Lorenz's work was first noted in [Stajano99theresurrecting]. noted in [Stajano99theresurrecting].
IDevID: An Initial Device Identity X.509 certificate installed by
the vendor on new equipment. This is a term from 802.1AR [IDevID]
IPIP Proxy: A stateless proxy alternative. IPIP Proxy: A stateless proxy alternative.
Join Proxy: A domain entity that helps the pledge join the domain. Join Proxy: A domain entity that helps the pledge join the domain.
A join proxy facilitates communication for devices that find A Join Proxy facilitates communication for devices that find
themselves in an environment where they are not provided themselves in an environment where they are not provided
connectivity until after they are validated as members of the connectivity until after they are validated as members of the
domain. For simplicity this document sometimes uses the term of domain. For simplicity, this document sometimes uses the term of
'proxy' to indicate the join proxy. The pledge is unaware that "proxy" to indicate the Join Proxy. The pledge is unaware that
they are communicating with a proxy rather than directly with a they are communicating with a proxy rather than directly with a
registrar. registrar.
Join Registrar (and Coordinator): A representative of the domain Join Registrar (and Coordinator): A representative of the domain
that is configured, perhaps autonomically, to decide whether a new that is configured, perhaps autonomically, to decide whether a new
device is allowed to join the domain. The administrator of the device is allowed to join the domain. The administrator of the
domain interfaces with a "join registrar (and coordinator)" to domain interfaces with a "Join Registrar (and Coordinator)" to
control this process. Typically a join registrar is "inside" its control this process. Typically, a Join Registrar is "inside" its
domain. For simplicity this document often refers to this as just domain. For simplicity, this document often refers to this as
"registrar". Within [I-D.ietf-anima-reference-model] this is just "registrar". Within [RFC8993], it is referred to as the
referred to as the "join registrar autonomic service agent". "Join Registrar Autonomic Service Agent (ASA)". Other communities
Other communities use the abbreviation "JRC". use the abbreviation "JRC".
LDevID: A Local Device Identity X.509 certificate installed by the LDevID: A Local Device Identifier X.509 certificate installed by the
owner of the equipment. This is a term from 802.1AR [IDevID] owner of the equipment. This is a term from 802.1AR [IDevID].
manufacturer: the term manufacturer is used throughout this document manufacturer: The term manufacturer is used throughout this document
to be the entity that created the device. This is typically the as the entity that created the device. This is typically the
"original equipment manufacturer" or OEM, but in more complex original equipment manufacturer (OEM), but in more complex
situations it could be a "value added retailer" (VAR), or possibly situations, it could be a value added retailer (VAR), or possibly
even a systems integrator. In general, it a goal of BRSKI to even a systems integrator. In general, a goal of BRSKI is to
eliminate small distinctions between different sales channels. eliminate small distinctions between different sales channels.
The reason for this is that it permits a single device, with a The reason for this is that it permits a single device, with a
uniform firmware load, to be shipped directly to all customers. uniform firmware load, to be shipped directly to all customers.
This eliminates costs for the manufacturer. This also reduces the This eliminates costs for the manufacturer. This also reduces the
number of products supported in the field increasing the chance number of products supported in the field, increasing the chance
that firmware will be more up to date. that firmware will be more up to date.
MASA Audit-Log: An anonymized list of previous owners maintained by MASA Audit-Log: An anonymized list of previous owners maintained by
the MASA on a per device (per pledge) basis. Described in the MASA on a per-device (per-pledge) basis, as described in
Section 5.8.1. Section 5.8.1.
MASA Service: A third-party Manufacturer Authorized Signing MASA Service: A third-party MASA service on the global Internet.
Authority (MASA) service on the global Internet. The MASA signs The MASA signs vouchers. It also provides a repository for audit-
vouchers. It also provides a repository for audit-log information log information of privacy-protected bootstrapping events. It
of privacy protected bootstrapping events. It does not track does not track ownership.
ownership.
nonced: a voucher (or request) that contains a nonce (the normal nonced: A voucher (or request) that contains a nonce (the normal
case). case).
nonceless: a voucher (or request) that does not contain a nonce, nonceless: A voucher (or request) that does not contain a nonce and
relying upon accurate clocks for expiration, or which does not either relies upon accurate clocks for expiration or does not
expire. expire.
offline: When an architectural component cannot perform realtime offline: When an architectural component cannot perform real-time
communications with a peer, either due to network connectivity or communications with a peer, due to either network connectivity or
because the peer is turned off, the operation is said to be the peer being turned off, the operation is said to be occurring
occurring offline. offline.
Ownership Tracker: An Ownership Tracker service on the global Ownership Tracker: An Ownership Tracker service on the global
Internet. The Ownership Tracker uses business processes to Internet. The Ownership Tracker uses business processes to
accurately track ownership of all devices shipped against domains accurately track ownership of all devices shipped against domains
that have purchased them. Although optional, this component that have purchased them. Although optional, this component
allows vendors to provide additional value in cases where their allows vendors to provide additional value in cases where their
sales and distribution channels allow for accurate tracking of sales and distribution channels allow for accurate tracking of
such ownership. Ownership tracking information is indicated in such ownership. Tracking information about ownership is indicated
vouchers as described in [RFC8366] in vouchers, as described in [RFC8366].
Pledge: The prospective (unconfigured) device, which has an identity Pledge: The prospective (unconfigured) device, which has an identity
installed at the factory. installed at the factory.
(Public) Key Infrastructure: The collection of systems and processes (Public) Key Infrastructure: The collection of systems and processes
that sustain the activities of a public key system. The registrar that sustains the activities of a public key system. The
acts as an [RFC5280] and [RFC5272] (see section 7) "Registration registrar acts as a "Registration Authority"; see [RFC5280] and
Authority". Section 7 of [RFC5272].
TOFU: Trust on First Use. Used similarly to [RFC7435]. This is TOFU: Trust on First Use. Used similarly to how it is described in
where a pledge device makes no security decisions but rather [RFC7435]. This is where a pledge device makes no security
simply trusts the first registrar it is contacted by. This is decisions but rather simply trusts the first registrar it is
also known as the "resurrecting duckling" model. contacted by. This is also known as the "resurrecting duckling"
model.
Voucher: A signed artifact from the MASA that indicates to a pledge Voucher: A signed artifact from the MASA that indicates the
the cryptographic identity of the registrar it should trust. cryptographic identity of the registrar it should trust to a
There are different types of vouchers depending on how that trust pledge. There are different types of vouchers depending on how
is asserted. Multiple voucher types are defined in [RFC8366] that trust is asserted. Multiple voucher types are defined in
[RFC8366].
1.3. Scope of solution 1.3. Scope of Solution
1.3.1. Support environment 1.3.1. Support Environment
This solution (BRSKI) can support large router platforms with multi- This solution (BRSKI) can support large router platforms with multi-
gigabit inter-connections, mounted in controlled access data centers. gigabit inter-connections, mounted in controlled access data centers.
But this solution is not exclusive to large equipment: it is intended But this solution is not exclusive to large equipment: it is intended
to scale to thousands of devices located in hostile environments, to scale to thousands of devices located in hostile environments,
such as ISP provided CPE devices which are drop-shipped to the end such as ISP-provided Customer Premises Equipment (CPE) devices that
user. The situation where an order is fulfilled from distributed are drop-shipped to the end user. The situation where an order is
warehouse from a common stock and shipped directly to the target fulfilled from a distributed warehouse from a common stock and
location at the request of a domain owner is explicitly supported. shipped directly to the target location at the request of a domain
That stock ("SKU") could be provided to a number of potential domain owner is explicitly supported. That stock ("SKU") could be provided
owners, and the eventual domain owner will not know a-priori which to a number of potential domain owners, and the eventual domain owner
device will go to which location. will not know a priori which device will go to which location.
The bootstrapping process can take minutes to complete depending on The bootstrapping process can take minutes to complete depending on
the network infrastructure and device processing speed. The network the network infrastructure and device processing speed. The network
communication itself is not optimized for speed; for privacy reasons, communication itself is not optimized for speed; for privacy reasons,
the discovery process allows for the pledge to avoid announcing its the discovery process allows for the pledge to avoid announcing its
presence through broadcasting. presence through broadcasting.
Nomadic or mobile devices often need to acquire credentials to access Nomadic or mobile devices often need to acquire credentials to access
the network at the new location. An example of this is mobile phone the network at the new location. An example of this is mobile phone
roaming among network operators, or even between cell towers. This roaming among network operators, or even between cell towers. This
is usually called handoff. BRSKI does not provide a low-latency is usually called "handoff". BRSKI does not provide a low-latency
handoff which is usually a requirement in such situations. For these handoff, which is usually a requirement in such situations. For
solutions BRSKI can be used to create a relationship (an LDevID) with these solutions, BRSKI can be used to create a relationship (an
the "home" domain owner. The resulting credentials are then used to LDevID) with the "home" domain owner. The resulting credentials are
provide credentials more appropriate for a low-latency handoff. then used to provide credentials more appropriate for a low-latency
handoff.
1.3.2. Constrained environments 1.3.2. Constrained Environments
Questions have been posed as to whether this solution is suitable in Questions have been posed as to whether this solution is suitable in
general for Internet of Things (IoT) networks. This depends on the general for Internet of Things (IoT) networks. This depends on the
capabilities of the devices in question. The terminology of capabilities of the devices in question. The terminology of
[RFC7228] is best used to describe the boundaries. [RFC7228] is best used to describe the boundaries.
The solution described in this document is aimed in general at non- The solution described in this document is aimed in general at non-
constrained (i.e., class 2+ [RFC7228]) devices operating on a non- constrained (i.e., Class 2+ [RFC7228]) devices operating on a non-
Challenged network. The entire solution as described here is not challenged network. The entire solution as described here is not
intended to be useable as-is by constrained devices operating on intended to be usable as is by constrained devices operating on
challenged networks (such as 802.15.4 Low-power Lossy Networks challenged networks (such as 802.15.4 Low-Power and Lossy Networks
(LLN)s). (LLNs)).
Specifically, there are protocol aspects described here that might Specifically, there are protocol aspects described here that might
result in congestion collapse or energy-exhaustion of intermediate result in congestion collapse or energy exhaustion of intermediate
battery powered routers in an LLN. Those types of networks should battery-powered routers in an LLN. Those types of networks should
not use this solution. These limitations are predominately related not use this solution. These limitations are predominately related
to the large credential and key sizes required for device to the large credential and key sizes required for device
authentication. Defining symmetric key techniques that meet the authentication. Defining symmetric key techniques that meet the
operational requirements is out-of-scope but the underlying protocol operational requirements is out of scope, but the underlying protocol
operations (TLS handshake and signing structures) have sufficient operations (TLS handshake and signing structures) have sufficient
algorithm agility to support such techniques when defined. algorithm agility to support such techniques when defined.
The imprint protocol described here could, however, be used by non- The imprint protocol described here could, however, be used by non-
energy constrained devices joining a non-constrained network (for energy constrained devices joining a non-constrained network (for
instance, smart light bulbs are usually mains powered, and speak instance, smart light bulbs are usually mains powered and use 802.11
802.11). It could also be used by non-constrained devices across a wireless technology). It could also be used by non-constrained
non-energy constrained, but challenged network (such as 802.15.4). devices across a non-energy constrained, but challenged, network
The certificate contents, and the process by which the four questions (such as 802.15.4). The certificate contents, and the process by
above are resolved do apply to constrained devices. It is simply the which the four questions above are resolved, do apply to constrained
actual on-the-wire imprint protocol that could be inappropriate. devices. It is simply the actual on-the-wire imprint protocol that
could be inappropriate.
1.3.3. Network Access Controls 1.3.3. Network Access Controls
This document presumes that network access control has either already This document presumes that network access control has already
occurred, is not required, or is integrated by the proxy and occurred, is not required, or is integrated by the proxy and
registrar in such a way that the device itself does not need to be registrar in such a way that the device itself does not need to be
aware of the details. Although the use of an X.509 Initial Device aware of the details. Although the use of an X.509 IDevID is
Identity is consistent with IEEE 802.1AR [IDevID], and allows for consistent with IEEE 802.1AR [IDevID], and allows for alignment with
alignment with 802.1X network access control methods, its use here is 802.1X network access control methods, its use here is for pledge
for pledge authentication rather than network access control. authentication rather than network access control. Integrating this
Integrating this protocol with network access control, perhaps as an protocol with network access control, perhaps as an Extensible
Extensible Authentication Protocol (EAP) method (see [RFC3748]), is Authentication Protocol (EAP) method (see [RFC3748]), is out of scope
out-of-scope. for this document.
1.3.4. Bootstrapping is not Booting 1.3.4. Bootstrapping is Not Booting
This document describes "bootstrapping" as the protocol used to This document describes "bootstrapping" as the protocol used to
obtain a local trust anchor. It is expected that this trust anchor, obtain a local trust anchor. It is expected that this trust anchor,
along with any additional configuration information subsequently along with any additional configuration information subsequently
installed, is persisted on the device across system restarts installed, is persisted on the device across system restarts
("booting"). Bootstrapping occurs only infrequently such as when a ("booting"). Bootstrapping occurs only infrequently such as when a
device is transferred to a new owner or has been reset to factory device is transferred to a new owner or has been reset to factory
default settings. default settings.
1.4. Leveraging the new key infrastructure / next steps 1.4. Leveraging the New Key Infrastructure / Next Steps
As a result of the protocol described herein, the bootstrapped As a result of the protocol described herein, bootstrapped devices
devices have the Domain CA trust anchor in common. An end entity have the domain CA trust anchor in common. An end-entity (EE)
certificate has optionally been issued from the Domain CA. This certificate has optionally been issued from the domain CA. This
makes it possible to securely deploy functionalities across the makes it possible to securely deploy functionalities across the
domain, e.g: domain; for example:
* Device management. * Device management
* Routing authentication. * Routing authentication
* Service discovery. * Service discovery
The major intended benefit is that it possible to use the credentials The major intended benefit is the ability to use the credentials
deployed by this protocol to secure the Autonomic Control Plane (ACP) deployed by this protocol to secure the Autonomic Control Plane (ACP)
([I-D.ietf-anima-autonomic-control-plane]). [RFC8994].
1.5. Requirements for Autonomic Network Infrastructure (ANI) devices 1.5. Requirements for Autonomic Networking Infrastructure (ANI) Devices
The BRSKI protocol can be used in a number of environments. Some of The BRSKI protocol can be used in a number of environments. Some of
the options in this document are the result of requirements that are the options in this document are the result of requirements that are
out of the ANI scope. This section defines the base requirements for out of the ANI scope. This section defines the base requirements for
ANI devices. ANI devices.
For devices that intend to become part of an Autonomic Network For devices that intend to become part of an ANI [RFC8993] that
Infrastructure (ANI) ([I-D.ietf-anima-reference-model]) that includes includes an Autonomic Control Plane [RFC8994], the BRSKI protocol
an Autonomic Control Plane MUST be implemented.
([I-D.ietf-anima-autonomic-control-plane]), the BRSKI protocol MUST
be implemented.
The pledge must perform discovery of the proxy as described in The pledge must perform discovery of the proxy as described in
Section 4.1 using Generic Autonomic Signaling Protocol (GRASP)'s DULL Section 4.1 using the Discovery Unsolicited Link-Local (DULL)
[I-D.ietf-anima-grasp] M_FLOOD announcements. [RFC8990] M_FLOOD announcements of the GeneRic Autonomic Signaling
Protocol (GRASP).
Upon successfully validating a voucher artifact, a status telemetry Upon successfully validating a voucher artifact, a status telemetry
MUST be returned. See Section 5.7. MUST be returned; see Section 5.7.
An ANIMA ANI pledge MUST implement the EST automation extensions An ANIMA ANI pledge MUST implement the EST automation extensions
described in Section 5.9. They supplement the [RFC7030] EST to described in Section 5.9. They supplement the EST [RFC7030] to
better support automated devices that do not have an end user. better support automated devices that do not have an end user.
The ANI Join Registrar Autonomic Service Agent (ASA) MUST support all The ANI Join Registrar ASA MUST support all the BRSKI and above-
the BRSKI and above listed EST operations. listed EST operations.
All ANI devices SHOULD support the BRSKI proxy function, using All ANI devices SHOULD support the BRSKI proxy function, using
circuit proxies over the ACP. (See Section 4.3) Circuit Proxies over the Autonomic Control Plane (ACP) (see
Section 4.3).
2. Architectural Overview 2. Architectural Overview
The logical elements of the bootstrapping framework are described in The logical elements of the bootstrapping framework are described in
this section. Figure 1 provides a simplified overview of the this section. Figure 1 provides a simplified overview of the
components. components.
+------------------------+ +------------------------+
+--------------Drop Ship----------------| Vendor Service | +--------------Drop-Ship----------------| Vendor Service |
| +------------------------+ | +------------------------+
| | M anufacturer| | | | M anufacturer| |
| | A uthorized |Ownership| | | A uthorized |Ownership|
| | S igning |Tracker | | | S igning |Tracker |
| | A uthority | | | | A uthority | |
| +--------------+---------+ | +--------------+---------+
| ^ | ^
| | BRSKI- | | BRSKI-
V | MASA V | MASA
+-------+ ............................................|... +-------+ ............................................|...
| | . | . | | . | .
| | . +------------+ +-----------+ | . | | . +------------+ +-----------+ | .
| | . | | | | | . | | . | | | | | .
|Pledge | . | Join | | Domain <-------+ . |Pledge | . | Join | | Domain <-------+ .
| | . | Proxy | | Registrar | . | | . | Proxy | | Registrar | .
| <-------->............<-------> (PKI RA) | . | <-------->............<-------> (PKI RA) | .
| | | BRSKI-EST | | . | | | BRSKI-EST | | .
| | . | | +-----+-----+ . | | . | | +-----+-----+ .
|IDevID | . +------------+ | e.g. RFC7030 . |IDevID | . +------------+ | e.g., RFC 7030 .
| | . +-----------------+----------+ . | | . +-----------------+----------+ .
| | . | Key Infrastructure | . | | . | Key Infrastructure | .
| | . | (e.g., PKI Certificate | . | | . | (e.g., PKI CA) | .
+-------+ . | Authority) | . +-------+ . | | .
. +----------------------------+ . . +----------------------------+ .
. . . .
................................................ ................................................
"Domain" components "Domain" Components
Figure 1: Architecture Overview Figure 1: Architecture Overview
We assume a multi-vendor network. In such an environment there could We assume a multivendor network. In such an environment, there could
be a Manufacturer Service for each manufacturer that supports devices be a manufacturer service for each manufacturer that supports devices
following this document's specification, or an integrator could following this document's specification, or an integrator could
provide a generic service authorized by multiple manufacturers. It provide a generic service authorized by multiple manufacturers. It
is unlikely that an integrator could provide Ownership Tracking is unlikely that an integrator could provide ownership tracking
services for multiple manufacturers due to the required sales channel services for multiple manufacturers due to the required sales channel
integrations necessary to track ownership. integrations necessary to track ownership.
The domain is the managed network infrastructure with a Key The domain is the managed network infrastructure with a key
Infrastructure the pledge is joining. The domain provides initial infrastructure that the pledge is joining. The domain provides
device connectivity sufficient for bootstrapping through a proxy. initial device connectivity sufficient for bootstrapping through a
The domain registrar authenticates the pledge, makes authorization proxy. The domain registrar authenticates the pledge, makes
decisions, and distributes vouchers obtained from the Manufacturer authorization decisions, and distributes vouchers obtained from the
Service. Optionally the registrar also acts as a PKI Certification manufacturer service. Optionally, the registrar also acts as a PKI
Authority. CA.
2.1. Behavior of a Pledge 2.1. Behavior of a Pledge
The pledge goes through a series of steps, which are outlined here at The pledge goes through a series of steps, which are outlined here at
a high level. a high level.
------------ ------------
/ Factory \ / Factory \
\ default / \ default /
-----+------ -----+------
skipping to change at page 15, line 36 skipping to change at line 699
| | (3) Request | | | (3) Request |
| | Join | | | Join |
| +------+-------+ | +------+-------+
| | | |
| +------v-------+ | +------v-------+
| | (4) Imprint | | | (4) Imprint |
^------------+ | ^------------+ |
| Bad MASA +------+-------+ | Bad MASA +------+-------+
| response | send Voucher Status Telemetry | response | send Voucher Status Telemetry
| +------v-------+ | +------v-------+
| | (5) Enroll |<---+ (non-error HTTP codes ) | | (5) Enroll |<---+ (non-error HTTP codes)
^------------+ |\___/ (e.g. 202 'Retry-After') ^------------+ |\___/ (e.g., 202 "Retry-After")
| Enroll +------+-------+ | Enroll +------+-------+
| Failure | | failure |
| -----v------ | -----v------
| / Enrolled \ | / Enrolled \
^------------+ | ^------------+ |
Factory \------------/ Factory \------------/
reset reset
Figure 2: Pledge State Diagram Figure 2: Pledge State Diagram
State descriptions for the pledge are as follows: State descriptions for the pledge are as follows:
1. Discover a communication channel to a registrar. 1. Discover a communication channel to a registrar.
2. Identify itself. This is done by presenting an X.509 IDevID 2. Identify itself. This is done by presenting an X.509 IDevID
credential to the discovered registrar (via the proxy) in a TLS credential to the discovered registrar (via the proxy) in a TLS
handshake. (The registrar credentials are only provisionally handshake. (The registrar credentials are only provisionally
accepted at this time). accepted at this time.)
3. Request to join the discovered registrar. A unique nonce is 3. Request to join the discovered registrar. A unique nonce is
included ensuring that any responses can be associated with this included, ensuring that any responses can be associated with this
particular bootstrapping attempt. particular bootstrapping attempt.
4. Imprint on the registrar. This requires verification of the 4. Imprint on the registrar. This requires verification of the
manufacturer-service-provided voucher. A voucher contains manufacturer-service-provided voucher. A voucher contains
sufficient information for the pledge to complete authentication sufficient information for the pledge to complete authentication
of a registrar. This document details this step in depth. of a registrar. This document details this step in depth.
5. Enroll. After imprint an authenticated TLS (HTTPS) connection 5. Enroll. After imprint, an authenticated TLS (HTTPS) connection
exists between pledge and registrar. Enrollment over Secure exists between the pledge and registrar. EST [RFC7030] can then
Transport (EST) [RFC7030] can then be used to obtain a domain be used to obtain a domain certificate from a registrar.
certificate from a registrar.
The pledge is now a member of, and can be managed by, the domain and The pledge is now a member of, and can be managed by, the domain and
will only repeat the discovery aspects of bootstrapping if it is will only repeat the discovery aspects of bootstrapping if it is
returned to factory default settings. returned to factory default settings.
This specification details integration with EST enrollment so that This specification details integration with EST enrollment so that
pledges can optionally obtain a locally issued certificate, although pledges can optionally obtain a locally issued certificate, although
any Representational State Transfer (REST) (see [REST]) interface any Representational State Transfer (REST) (see [REST]) interface
could be integrated in future work. could be integrated in future work.
2.2. Secure Imprinting using Vouchers 2.2. Secure Imprinting Using Vouchers
A voucher is a cryptographically protected artifact (using a digital A voucher is a cryptographically protected artifact (using a digital
signature) to the pledge device authorizing a zero-touch imprint on signature) to the pledge device authorizing a zero-touch imprint on
the registrar domain. the registrar domain.
The format and cryptographic mechanism of vouchers is described in The format and cryptographic mechanism of vouchers is described in
detail in [RFC8366]. detail in [RFC8366].
Vouchers provide a flexible mechanism to secure imprinting: the Vouchers provide a flexible mechanism to secure imprinting: the
pledge device only imprints when a voucher can be validated. At the pledge device only imprints when a voucher can be validated. At the
lowest security levels the MASA can indiscriminately issue vouchers lowest security levels, the MASA can indiscriminately issue vouchers
and log claims of ownership by domains. At the highest security and log claims of ownership by domains. At the highest security
levels issuance of vouchers can be integrated with complex sales levels, issuance of vouchers can be integrated with complex sales
channel integrations that are beyond the scope of this document. The channel integrations that are beyond the scope of this document. The
sales channel integration would verify actual (legal) ownership of sales channel integration would verify actual (legal) ownership of
the pledge by the domain. This provides the flexibility for a number the pledge by the domain. This provides the flexibility for a number
of use cases via a single common protocol mechanism on the pledge and of use cases via a single common protocol mechanism on the pledge and
registrar devices that are to be widely deployed in the field. The registrar devices that are to be widely deployed in the field. The
MASA services have the flexibility to leverage either the currently MASA services have the flexibility to either leverage the currently
defined claim mechanisms or to experiment with higher or lower defined claim mechanisms or experiment with higher or lower security
security levels. levels.
Vouchers provide a signed but non-encrypted communication channel Vouchers provide a signed but non-encrypted communication channel
among the pledge, the MASA, and the registrar. The registrar among the pledge, the MASA, and the registrar. The registrar
maintains control over the transport and policy decisions, allowing maintains control over the transport and policy decisions, allowing
the local security policy of the domain network to be enforced. the local security policy of the domain network to be enforced.
2.3. Initial Device Identifier 2.3. Initial Device Identifier
Pledge authentication and pledge voucher-request signing is via a Pledge authentication and pledge voucher-request signing is via a
PKIX-shaped certificate installed during the manufacturing process. PKIX-shaped certificate installed during the manufacturing process.
This is the 802.1AR Initial Device Identifier (IDevID), and it This is the 802.1AR IDevID, and it provides a basis for
provides a basis for authenticating the pledge during the protocol authenticating the pledge during the protocol exchanges described
exchanges described here. There is no requirement for a common root here. There is no requirement for a common root PKI hierarchy. Each
PKI hierarchy. Each device manufacturer can generate its own root device manufacturer can generate its own root certificate.
certificate. Specifically, the IDevID enables: Specifically, the IDevID enables:
1. Uniquely identifying the pledge by the Distinguished Name (DN) * Uniquely identifying the pledge by the Distinguished Name (DN) and
and subjectAltName (SAN) parameters in the IDevID. The unique subjectAltName (SAN) parameters in the IDevID. The unique
identification of a pledge in the voucher objects are derived identification of a pledge in the voucher objects are derived from
from those parameters as described below. Section 10.3 discusses those parameters as described below. Section 10.3 discusses
privacy implications of the identifier. privacy implications of the identifier.
2. Provides a cryptographic authentication of the pledge to the * Providing a cryptographic authentication of the pledge to the
Registrar (see Section 5.3). registrar (see Section 5.3).
3. Secure auto-discovery of the pledge's MASA by the registrar (see * Securing auto-discovery of the pledge's MASA by the registrar (see
Section 2.8). Section 2.8).
4. Signing of voucher-request by the pledge's IDevID (see * Signing of a voucher-request by the pledge's IDevID (see
Section 3). Section 3).
5. Provides a cryptographic authentication of the pledge to the MASA * Providing a cryptographic authentication of the pledge to the MASA
(see Section 5.5.5). (see Section 5.5.5).
Section 7.2.13 (2009 edition) and section 8.10.3 (2018 edition) of Sections 7.2.13 (2009 edition) and 8.10.3 (2018 edition) of [IDevID]
[IDevID] discusses keyUsage and extendedKeyUsage extensions in the discuss keyUsage and extendedKeyUsage extensions in the IDevID
IDevID certificate. [IDevID] acknowledges that adding restrictions certificate. [IDevID] acknowledges that adding restrictions in the
in the certificate limits applicability of these long-lived certificate limits applicability of these long-lived certificates.
certificates. This specification emphasizes this point, and This specification emphasizes this point and therefore RECOMMENDS
therefore RECOMMENDS that no key usage restrictions be included. that no key usage restrictions be included. This is consistent with
This is consistent with [RFC5280] section 4.2.1.3, which does not [RFC5280], Section 4.2.1.3, which does not require key usage
require key usage restrictions for end entity certificates. restrictions for end-entity certificates.
2.3.1. Identification of the Pledge 2.3.1. Identification of the Pledge
In the context of BRSKI, pledges have a 1:1 relationship with a In the context of BRSKI, pledges have a 1:1 relationship with a
"serial-number". This serial-number is used both in the "serial- "serial-number". This serial-number is used both in the serial-
number" field of voucher or voucher-requests (see Section 3) and in number field of a voucher or voucher-requests (see Section 3) and in
local policies on registrar or MASA (see Section 5). local policies on the registrar or MASA (see Section 5).
There is a (certificate) serialNumber field is defined in [RFC5280] There is a (certificate) serialNumber field defined in [RFC5280],
section 4.1.2.2. In the ASN.1, this is referred to as the Section 4.1.2.2. In ASN.1, this is referred to as the
CertificateSerialNumber. This field is NOT relevant to this CertificateSerialNumber. This field is NOT relevant to this
specification. Do not confuse this field with the "serial-number" specification. Do not confuse this field with the serial-number
defined by this document, or by [IDevID] and [RFC4519] section 2.31. defined by this document, or by [IDevID] and [RFC4519], Section 2.31.
The device serial number is defined in [RFC5280] section A.1 and A.2 The device serial number is defined in Appendix A.1 of [RFC5280] as
as the X520SerialNumber, with the OID tag id-at-serialNumber. the X520SerialNumber, with the OID tag id-at-serialNumber.
The device serial number field (X520SerialNumber) is used as follows The device _serialNumber_ field (X520SerialNumber) is used as follows
by the pledge to build the "serial-number" that is placed in the by the pledge to build the *serial-number* that is placed in the
voucher-request. In order to build it, the fields need to be voucher-request. In order to build it, the fields need to be
converted into a serial-number of "type string". converted into a serial-number of "type string".
An example of a printable form of the "serialNumber" field is An example of a printable form of the serialNumber field is provided
provided in [RFC4519] section 2.31 ("WI-3005"). That section further in [RFC4519], Section 2.31 ("WI-3005"). That section further
provides equality and syntax attributes. provides equality and syntax attributes.
Due to the reality of existing device identity provisioning Due to the reality of existing device identity provisioning
processes, some manufacturers have stored serial-numbers in other processes, some manufacturers have stored serial-numbers in other
fields. Registrar's SHOULD be configurable, on a per-manufacturer fields. Registrars SHOULD be configurable, on a per-manufacturer
basis, to look for serial-number equivalents in other fields. basis, to look for serial-number equivalents in other fields.
As explained in Section 5.5 the Registrar MUST extract the serial- As explained in Section 5.5, the registrar MUST again extract the
number again itself from the pledge's TLS certificate. It can serialNumber itself from the pledge's TLS certificate. It can
consult the serial-number in the pledge-request if there are any consult the serial-number in the pledge request if there is any
possible confusion about the source of the serial-number. possible confusion about the source of the serial-number.
2.3.2. MASA URI extension 2.3.2. MASA URI Extension
This document defines a new PKIX non-critical certificate extension This document defines a new PKIX non-critical certificate extension
to carry the MASA URI. This extension is intended to be used in the to carry the MASA URI. This extension is intended to be used in the
IDevID certificate. The URI is represented as described in IDevID certificate. The URI is represented as described in
Section 7.4 of [RFC5280]. Section 7.4 of [RFC5280].
The URI provides the authority information. The BRSKI "/.well-known" The URI provides the authority information. The BRSKI "/.well-known"
tree ([RFC5785]) is described in Section 5. tree [RFC8615] is described in Section 5.
A complete URI MAY be in this extension, including the 'scheme', A complete URI MAY be in this extension, including the "scheme",
'authority', and 'path', The complete URI will typically be used in "authority", and "path". The complete URI will typically be used in
diagnostic or experimental situations. Typically, (and in diagnostic or experimental situations. Typically (and in
consideration to constrained systems), this SHOULD be reduced to only consideration to constrained systems), this SHOULD be reduced to only
the 'authority', in which case a scheme of "https://" ([RFC7230] the "authority", in which case a scheme of "https://" (see [RFC7230],
section 2.7.3) and 'path' of "/.well-known/brski" is to be assumed. Section 2.7.3) and a "path" of "/.well-known/brski" is to be assumed.
The registrar can assume that only the 'authority' is present in the The registrar can assume that only the "authority" is present in the
extension, if there are no slash ("/") characters in the extension. extension, if there are no slash ("/") characters in the extension.
Section 7.4 of [RFC5280] calls out various schemes that MUST be Section 7.4 of [RFC5280] calls out various schemes that MUST be
supported, including LDAP, HTTP and FTP. However, the registrar MUST supported, including the Lightweight Directory Access Protocol
use HTTPS for the BRSKI-MASA connection. (LDAP), HTTP, and FTP. However, the registrar MUST use HTTPS for the
BRSKI-MASA connection.
The new extension is identified as follows: The new extension is identified as follows:
<CODE BEGINS> <CODE BEGINS>
MASAURLExtnModule-2016 { iso(1) identified-organization(3) dod(6) MASAURLExtnModule-2016 { iso(1) identified-organization(3) dod(6)
internet(1) security(5) mechanisms(5) pkix(7) internet(1) security(5) mechanisms(5) pkix(7)
id-mod(0) id-mod-MASAURLExtn2016(TBD) } id-mod(0) id-mod-MASAURLExtn2016(96) }
DEFINITIONS IMPLICIT TAGS ::= BEGIN DEFINITIONS IMPLICIT TAGS ::= BEGIN
-- EXPORTS ALL -- -- EXPORTS ALL --
IMPORTS IMPORTS
EXTENSION EXTENSION
FROM PKIX-CommonTypes-2009 FROM PKIX-CommonTypes-2009
{ iso(1) identified-organization(3) dod(6) internet(1) { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) security(5) mechanisms(5) pkix(7) id-mod(0)
skipping to change at page 20, line 30 skipping to change at line 894
id-pe FROM PKIX1Explicit-2009 id-pe FROM PKIX1Explicit-2009
{ iso(1) identified-organization(3) dod(6) internet(1) { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkix1-explicit-02(51) } ; id-mod-pkix1-explicit-02(51) } ;
MASACertExtensions EXTENSION ::= { ext-MASAURL, ... } MASACertExtensions EXTENSION ::= { ext-MASAURL, ... }
ext-MASAURL EXTENSION ::= { SYNTAX MASAURLSyntax ext-MASAURL EXTENSION ::= { SYNTAX MASAURLSyntax
IDENTIFIED BY id-pe-masa-url } IDENTIFIED BY id-pe-masa-url }
id-pe-masa-url OBJECT IDENTIFIER ::= { id-pe TBD } id-pe-masa-url OBJECT IDENTIFIER ::= { id-pe 32 }
MASAURLSyntax ::= IA5String MASAURLSyntax ::= IA5String
END END
<CODE ENDS> <CODE ENDS>
Figure 3: MASAURL ASN.1 Module Figure 3: MASAURL ASN.1 Module
The choice of id-pe is based on guidance found in Section 4.2.2 of The choice of id-pe is based on guidance found in Section 4.2.2 of
[RFC5280], "These extensions may be used to direct applications to [RFC5280]: "These extensions may be used to direct applications to
on-line information about the issuer or the subject". The MASA URL on-line information about the issuer or the subject". The MASA URL
is precisely that: online information about the particular subject. is precisely that: online information about the particular subject.
2.4. Protocol Flow 2.4. Protocol Flow
A representative flow is shown in Figure 4 A representative flow is shown in Figure 4.
+--------+ +---------+ +------------+ +------------+ +--------+ +---------+ +------------+ +------------+
| Pledge | | Circuit | | Domain | | Vendor | | Pledge | | Circuit | | Domain | | Vendor |
| | | Join | | Registrar | | Service | | | | Join | | Registrar | | Service |
| | | Proxy | | (JRC) | | (MASA) | | | | Proxy | | (JRC) | | (MASA) |
+--------+ +---------+ +------------+ +------------+ +--------+ +---------+ +------------+ +------------+
| | | Internet | | | | Internet |
[discover] | | | [discover] | | |
|<-RFC4862 IPv6 addr | | | |<-RFC 4862 IPv6 addr | | |
|<-RFC3927 IPv4 addr | Appendix A | Legend | |<-RFC 3927 IPv4 addr | Appendix A | Legend |
|-++++++++++++++++++->| | C - circuit | |-++++++++++++++++++->| | C - Circuit |
| optional: mDNS query| Appendix B | join proxy | | optional: mDNS query| Appendix B | Join Proxy |
| RFC6763/RFC6762 (+) | | P - provisional | | RFCs 6763/6762 (+) | | P - Provisional TLS|
|<-++++++++++++++++++-| | TLS connection | |<-++++++++++++++++++-| | Connection |
| GRASP M_FLOOD | | | | GRASP M_FLOOD | | |
| periodic broadcast| | | | periodic broadcast| | |
[identity] | | | [identity] | | |
|<------------------->C<----------------->| | |<------------------->C<----------------->| |
| TLS via the Join Proxy | | | TLS via the Join Proxy | |
|<--Registrar TLS server authentication---| | |<--Registrar TLS server authentication---| |
[PROVISIONAL accept of server cert] | | [PROVISIONAL accept of server cert] | |
P---X.509 client authentication---------->| | P---X.509 client authentication---------->| |
[request join] | | [request join] | |
P---Voucher Request(w/nonce for voucher)->| | P---Voucher-Request(w/nonce for voucher)->| |
P /------------------- | | P /------------------- | |
P | [accept device?] | P | [accept device?] |
P | [contact Vendor] | P | [contact vendor] |
P | |--Pledge ID-------->| P | |--Pledge ID-------->|
P | |--Domain ID-------->| P | |--Domain ID-------->|
P | |--optional:nonce--->| P | |--optional:nonce--->|
P optional: | [extract DomainID] P optional: | [extract DomainID]
P can occur in advance | [update audit log] P can occur in advance | [update audit-log]
P if nonceleess | | P if nonceless | |
P | |<- voucher ---------| P | |<- voucher ---------|
P \------------------- | w/nonce if provided| P \------------------- | w/nonce if provided|
P<------voucher---------------------------| | P<------voucher---------------------------| |
[imprint] | | [imprint] | |
|-------voucher status telemetry--------->| | |-------voucher status telemetry--------->| |
| |<-device audit log--| | |<-device audit-log--|
| [verify audit log and voucher] | | [verify audit-log and voucher] |
|<--------------------------------------->| | |<--------------------------------------->| |
[enroll] | | [enroll] | |
| Continue with RFC7030 enrollment | | | Continue with enrollment using now | |
| using now bidirectionally authenticated | | | bidirectionally authenticated TLS | |
| TLS session. | | | session per RFC 7030. | |
[enrolled] | | [enrolled] | |
Figure 4: Protocol Time Sequence Diagram Figure 4: Protocol Time Sequence Diagram
On initial bootstrap, a new device (the pledge) uses a local service On initial bootstrap, a new device (the pledge) uses a local service
autodiscovery (GRASP or mDNS) to locate a join proxy. The join proxy auto-discovery (the GeneRic Autonomic Signaling Protocol (GRASP) or
Multicast DNS (mDNS)) to locate a Join Proxy. The Join Proxy
connects the pledge to a local registrar (the JRC). connects the pledge to a local registrar (the JRC).
Having found a candidate registrar, the fledgling pledge sends some Having found a candidate registrar, the fledgling pledge sends some
information about itself to the registrar, including its serial information about itself to the registrar, including its serial
number in the form of a voucher request and its device identity number in the form of a voucher-request and its IDevID certificate as
certificate (IDevID) as part of the TLS session. part of the TLS session.
The registrar can determine whether it expected such a device to The registrar can determine whether it expected such a device to
appear, and locates a MASA. The location of the MASA is usually appear and locates a MASA. The location of the MASA is usually found
found in an extension in the IDevID. Having determined that the MASA in an extension in the IDevID. Having determined that the MASA is
is suitable, the entire information from the initial voucher request suitable, the entire information from the initial voucher-request
(including device serial number) is transmitted over the internet in (including the device's serial number) is transmitted over the
a TLS protected channel to the manufacturer, along with information Internet in a TLS-protected channel to the manufacturer, along with
about the registrar/owner. information about the registrar/owner.
The manufacturer can then apply policy based on the provided The manufacturer can then apply policy based on the provided
information, as well as other sources of information (such as sales information, as well as other sources of information (such as sales
records), to decide whether to approve the claim by the registrar to records), to decide whether to approve the claim by the registrar to
own the device; if the claim is accepted, a voucher is issued that own the device; if the claim is accepted, a voucher is issued that
directs the device to accept its new owner. directs the device to accept its new owner.
The voucher is returned to the registrar, but not immediately to the The voucher is returned to the registrar, but not immediately to the
device -- the registrar has an opportunity to examine the voucher, device -- the registrar has an opportunity to examine the voucher,
the MASA's audit-logs, and other sources of information to determine the MASA's audit-logs, and other sources of information to determine
whether the device has been tampered with, and whether the bootstrap whether the device has been tampered with and whether the bootstrap
should be accepted. should be accepted.
No filtering of information is possible in the signed voucher, so No filtering of information is possible in the signed voucher, so
this is a binary yes-or-no decision. If the registrar accepts the this is a binary yes-or-no decision. After the registrar has applied
voucher as a proper one for its device, the voucher is returned to any local policy to the voucher, if it accepts the voucher, then the
the pledge for imprinting. voucher is returned to the pledge for imprinting.
The voucher also includes a trust anchor that the pledge uses as The voucher also includes a trust anchor that the pledge uses to
representing the owner. This is used to successfully bootstrap from represent the owner. This is used to successfully bootstrap from an
an environment where only the manufacturer has built-in trust by the environment where only the manufacturer has built-in trust by the
device into an environment where the owner now has a PKI footprint on device to an environment where the owner now has a PKI footprint on
the device. the device.
When BRSKI is followed with EST this single footprint is further When BRSKI is followed with EST, this single footprint is further
leveraged into the full owner's PKI and a LDevID for the device. leveraged into the full owner's PKI and an LDevID for the device.
Subsequent reporting steps provide flows of information to indicate Subsequent reporting steps provide flows of information to indicate
success/failure of the process. success/failure of the process.
2.5. Architectural Components 2.5. Architectural Components
2.5.1. Pledge 2.5.1. Pledge
The pledge is the device that is attempting to join. The pledge is The pledge is the device that is attempting to join. It is assumed
assumed to talk to the Join Proxy using link-local network that the pledge talks to the Join Proxy using link-local network
connectivity. In most cases, the pledge has no other connectivity connectivity. In most cases, the pledge has no other connectivity
until the pledge completes the enrollment process and receives some until the pledge completes the enrollment process and receives some
kind of network credential. kind of network credential.
2.5.2. Join Proxy 2.5.2. Join Proxy
The join proxy provides HTTPS connectivity between the pledge and the The Join Proxy provides HTTPS connectivity between the pledge and the
registrar. A circuit proxy mechanism is described in Section 4. registrar. A Circuit Proxy mechanism is described in Section 4.
Additional mechanisms, including a CoAP mechanism and a stateless Additional mechanisms, including a Constrained Application Protocol
IPIP mechanism are the subject of future work. (CoAP) mechanism and a stateless IP in IP (IPIP) mechanism, are the
subject of future work.
2.5.3. Domain Registrar 2.5.3. Domain Registrar
The domain's registrar operates as the BRSKI-MASA client when The domain's registrar operates as the BRSKI-MASA client when
requesting vouchers from the MASA (see Section 5.4). The registrar requesting vouchers from the MASA (see Section 5.4). The registrar
operates as the BRSKI-EST server when pledges request vouchers (see operates as the BRSKI-EST server when pledges request vouchers (see
Section 5.1). The registrar operates as the BRSKI-EST server Section 5.1). The registrar operates as the BRSKI-EST server
"Registration Authority" if the pledge requests an end entity "Registration Authority" if the pledge requests an end-entity
certificate over the BRSKI-EST connection (see Section 5.9). certificate over the BRSKI-EST connection (see Section 5.9).
The registrar uses an Implicit Trust Anchor database for The registrar uses an Implicit Trust Anchor database for
authenticating the BRSKI-MASA connection's MASA TLS Server authenticating the BRSKI-MASA connection's MASA TLS server
Certificate. Configuration or distribution of trust anchors is out- certificate. Configuration or distribution of trust anchors is out
of-scope for this specification. of scope for this specification.
The registrar uses a different Implicit Trust Anchor database for The registrar uses a different Implicit Trust Anchor database for
authenticating the BRSKI-EST connection's Pledge TLS Client authenticating the BRSKI-EST connection's pledge TLS Client
Certificate. Configuration or distribution of the BRSKI-EST client Certificate. Configuration or distribution of the BRSKI-EST client
trust anchors is out-of-scope of this specification. Note that the trust anchors is out of scope of this specification. Note that the
trust anchors in/excluded from the database will affect which trust anchors in / excluded from the database will affect which
manufacturers' devices are acceptable to the registrar as pledges, manufacturers' devices are acceptable to the registrar as pledges,
and can also be used to limit the set of MASAs that are trusted for and they can also be used to limit the set of MASAs that are trusted
enrollment. for enrollment.
2.5.4. Manufacturer Service 2.5.4. Manufacturer Service
The Manufacturer Service provides two logically separate functions: The manufacturer service provides two logically separate functions:
the Manufacturer Authorized Signing Authority (MASA) described in the MASA as described in Sections 5.5 and 5.6 and an ownership
Section 5.5 and Section 5.6, and an ownership tracking/auditing tracking/auditing function as described in Sections 5.7 and 5.8.
function described in Section 5.7 and Section 5.8.
2.5.5. Public Key Infrastructure (PKI) 2.5.5. Public Key Infrastructure (PKI)
The Public Key Infrastructure (PKI) administers certificates for the The Public Key Infrastructure (PKI) administers certificates for the
domain of concern, providing the trust anchor(s) for it and allowing domain of concern, providing the trust anchor(s) for it and allowing
enrollment of pledges with domain certificates. enrollment of pledges with domain certificates.
The voucher provides a method for the distribution of a single PKI The voucher provides a method for the distribution of a single PKI
trust anchor (as the "pinned-domain-cert"). A distribution of the trust anchor (as the "pinned-domain-cert"). A distribution of the
full set of current trust anchors is possible using the optional EST full set of current trust anchors is possible using the optional EST
integration. integration.
The domain's registrar acts as an [RFC5272] Registration Authority, The domain's registrar acts as a Registration Authority [RFC5272],
requesting certificates for pledges from the Key Infrastructure. requesting certificates for pledges from the PKI.
The expectations of the PKI are unchanged from EST [RFC7030]. This The expectations of the PKI are unchanged from EST [RFC7030]. This
document does not place any additional architectural requirements on document does not place any additional architectural requirements on
the Public Key Infrastructure. the PKI.
2.6. Certificate Time Validation 2.6. Certificate Time Validation
2.6.1. Lack of realtime clock 2.6.1. Lack of Real-Time Clock
Many devices when bootstrapping do not have knowledge of the current When bootstrapping, many devices do not have knowledge of the current
time. Mechanisms such as Network Time Protocols cannot be secured time. Mechanisms such as Network Time Protocols cannot be secured
until bootstrapping is complete. Therefore bootstrapping is defined until bootstrapping is complete. Therefore, bootstrapping is defined
with a framework that does not require knowledge of the current time. with a framework that does not require knowledge of the current time.
A pledge MAY ignore all time stamps in the voucher and in the A pledge MAY ignore all time stamps in the voucher and in the
certificate validity periods if it does not know the current time. certificate validity periods if it does not know the current time.
The pledge is exposed to dates in the following five places: The pledge is exposed to dates in the following five places:
registrar certificate notBefore, registrar certificate notAfter, registrar certificate notBefore, registrar certificate notAfter,
voucher created-on, and voucher expires-on. Additionally, CMS voucher created-on, and voucher expires-on. Additionally,
signatures contain a signingTime. Cryptographic Message Syntax (CMS) signatures contain a signingTime.
A pledge with a real time clock in which it has confidence, MUST A pledge with a real-time clock in which it has confidence MUST check
check the above time fields in all certificates and signatures that the above time fields in all certificates and signatures that it
it processes. processes.
If the voucher contains a nonce then the pledge MUST confirm the If the voucher contains a nonce, then the pledge MUST confirm the
nonce matches the original pledge voucher-request. This ensures the nonce matches the original pledge voucher-request. This ensures the
voucher is fresh. See Section 5.2. voucher is fresh. See Section 5.2.
2.6.2. Infinite Lifetime of IDevID 2.6.2. Infinite Lifetime of IDevID
[RFC5280] explains that long lived pledge certificates "SHOULD be Long-lived pledge certificates "SHOULD be assigned the
assigned the GeneralizedTime value of 99991231235959Z" for the GeneralizedTime value of 99991231235959Z" for the notAfter field as
notAfter field. explained in [RFC5280].
Some deployed IDevID management systems are not compliant with the Some deployed IDevID management systems are not compliant with the
802.1AR requirement for infinite lifetimes, and put in typical <= 3 802.1AR requirement for infinite lifetimes and are put in typical <=
year certificate lifetimes. Registrars SHOULD be configurable on a 3 year certificate lifetimes. Registrars SHOULD be configurable on a
per-manufacturer basis to ignore pledge lifetimes when the pledge did per-manufacturer basis to ignore pledge lifetimes when the pledge
not follow the RFC5280 recommendations. does not follow the recommendations in [RFC5280].
2.7. Cloud Registrar 2.7. Cloud Registrar
There exist operationally open networks wherein devices gain There exist operationally open networks wherein devices gain
unauthenticated access to the Internet at large. In these use cases unauthenticated access to the Internet at large. In these use cases,
the management domain for the device needs to be discovered within the management domain for the device needs to be discovered within
the larger Internet. The case where a device can boot and get access the larger Internet. The case where a device can boot and get access
to larger Internet are less likely within the ANIMA ACP scope but may to a larger Internet is less likely within the ANIMA ACP scope but
be more important in the future. In the ANIMA ACP scope, new devices may be more important in the future. In the ANIMA ACP scope, new
will be quarantined behind a Join Proxy. devices will be quarantined behind a Join Proxy.
There are additionally some greenfield situations involving an Additionally, there are some greenfield situations involving an
entirely new installation where a device may have some kind of entirely new installation where a device may have some kind of
management uplink that it can use (such as via 3G network for management uplink that it can use (such as via a 3G network, for
instance). In such a future situation, the device might use this instance). In such a future situation, the device might use this
management interface to learn that it should configure itself to management interface to learn that it should configure itself to
become the local registrar. become the local registrar.
In order to support these scenarios, the pledge MAY contact a well In order to support these scenarios, the pledge MAY contact a well-
known URI of a cloud registrar if a local registrar cannot be known URI of a cloud registrar if a local registrar cannot be
discovered or if the pledge's target use cases do not include a local discovered or if the pledge's target use cases do not include a local
registrar. registrar.
If the pledge uses a well known URI for contacting a cloud registrar If the pledge uses a well-known URI for contacting a cloud registrar,
a manufacturer-assigned Implicit Trust Anchor database (see a manufacturer-assigned Implicit Trust Anchor database (see
[RFC7030]) MUST be used to authenticate that service as described in [RFC7030]) MUST be used to authenticate that service as described in
[RFC6125]. The use of a DNS-ID for validation is appropriate, and it [RFC6125]. The use of a DNS-ID for validation is appropriate, and it
may include wildcard components on the left-mode side. This is may include wildcard components on the left-mode side. This is
consistent with the human user configuration of an EST server URI in consistent with the human-user configuration of an EST server URI in
[RFC7030] which also depends on RFC6125. [RFC7030], which also depends on [RFC6125].
2.8. Determining the MASA to contact 2.8. Determining the MASA to Contact
The registrar needs to be able to contact a MASA that is trusted by The registrar needs to be able to contact a MASA that is trusted by
the pledge in order to obtain vouchers. There are three mechanisms the pledge in order to obtain vouchers.
described:
The device's Initial Device Identifier (IDevID) will normally contain The device's IDevID will normally contain the MASA URL as detailed in
the MASA URL as detailed in Section 2.3. This is the RECOMMENDED Section 2.3. This is the RECOMMENDED mechanism.
mechanism.
It can be operationally difficult to ensure the necessary X.509 In some cases, it can be operationally difficult to ensure the
extensions are in the pledge's IDevID due to the difficulty of necessary X.509 extensions are in the pledge's IDevID due to the
aligning current pledge manufacturing with software releases and difficulty of aligning current pledge manufacturing with software
development. As a final fallback the registrar MAY be manually releases and development; thus, as a final fallback, the registrar
configured or distributed with a MASA URL for each manufacturer. MAY be manually configured or distributed with a MASA URL for each
Note that the registrar can only select the configured MASA URL based manufacturer. Note that the registrar can only select the configured
on the trust anchor -- so manufacturers can only leverage this MASA URL based on the trust anchor -- so manufacturers can only
approach if they ensure a single MASA URL works for all pledges leverage this approach if they ensure a single MASA URL works for all
associated with each trust anchor. pledges associated with each trust anchor.
3. Voucher-Request artifact 3. Voucher-Request Artifact
Voucher-requests are how vouchers are requested. The semantics of Voucher-requests are how vouchers are requested. The semantics of
the voucher-request are described below, in the YANG model. the voucher-request are described below, in the YANG module.
A pledge forms the "pledge voucher-request", signs it with it's A pledge forms the "pledge voucher-request", signs it with its
IDevID and submits it to the registrar. IDevID, and submits it to the registrar.
The registrar in turn forms the "registrar voucher-request", signs it In turn, the registrar forms the "registrar voucher-request", signs
with it's Registrar keypair and submits it to the MASA. it with its registrar key pair, and submits it to the MASA.
The "proximity-registrar-cert" leaf is used in the pledge voucher- The "proximity-registrar-cert" leaf is used in the pledge voucher-
requests. This provides a method for the pledge to assert the requests. This provides a method for the pledge to assert the
registrar's proximity. registrar's proximity.
This network proximity results from the following properties in the This network proximity results from the following properties in the
ACP context: the pledge is connected to the Join Proxy (Section 4) ACP context: the pledge is connected to the Join Proxy (Section 4)
using a Link-Local IPv6 connection. While the Join Proxy does not using a link-local IPv6 connection. While the Join Proxy does not
participate in any meaningful sense in the cryptography of the TLS participate in any meaningful sense in the cryptography of the TLS
connection (such as via a Channel Binding), the Registrar can observe connection (such as via a Channel Binding), the registrar can observe
that the connection is via the private ACP (ULA) address of the join that the connection is via the private ACP (ULA) address of the Join
proxy, and could not come from outside the ACP. The Pledge must Proxy, and it cannot come from outside the ACP. The pledge must
therefore be at most one IPv6 Link-Local hop away from an existing therefore be at most one IPv6 link-local hop away from an existing
node on the ACP. node on the ACP.
Other users of BRSKI will need to define other kinds of assertions if Other users of BRSKI will need to define other kinds of assertions if
the network proximity described above does not match their needs. the network proximity described above does not match their needs.
The "prior-signed-voucher-request" leaf is used in registrar voucher- The "prior-signed-voucher-request" leaf is used in registrar voucher-
requests. If present, it is the signed pledge voucher-request requests. If present, it is the signed pledge voucher-request
artifact. This provides a method for the registrar to forward the artifact. This provides a method for the registrar to forward the
pledge's signed request to the MASA. This completes transmission of pledge's signed request to the MASA. This completes transmission of
the signed "proximity-registrar-cert" leaf. the signed proximity-registrar-cert leaf.
Unless otherwise signaled (outside the voucher-request artifact), the Unless otherwise signaled (outside the voucher-request artifact), the
signing structure is as defined for vouchers, see [RFC8366]. signing structure is as defined for vouchers; see [RFC8366].
3.1. Nonceless Voucher Requests 3.1. Nonceless Voucher-Requests
A registrar MAY also retrieve nonceless vouchers by sending nonceless A registrar MAY also retrieve nonceless vouchers by sending nonceless
voucher-requests to the MASA in order to obtain vouchers for use when voucher-requests to the MASA in order to obtain vouchers for use when
the registrar does not have connectivity to the MASA. No "prior- the registrar does not have connectivity to the MASA. No prior-
signed-voucher-request" leaf would be included. The registrar will signed-voucher-request leaf would be included. The registrar will
also need to know the serial number of the pledge. This document also need to know the serial number of the pledge. This document
does not provide a mechanism for the registrar to learn that in an does not provide a mechanism for the registrar to learn that in an
automated fashion. Typically this will be done via scanning of bar- automated fashion. Typically, this will be done via the scanning of
code or QR-code on packaging, or via some sales channel integration. a bar code or QR code on packaging, or via some sales channel
integration.
3.2. Tree Diagram 3.2. Tree Diagram
The following tree diagram illustrates a high-level view of a The following tree diagram illustrates a high-level view of a
voucher-request document. The voucher-request builds upon the voucher-request document. The voucher-request builds upon the
voucher artifact described in [RFC8366]. The tree diagram is voucher artifact described in [RFC8366]. The tree diagram is
described in [RFC8340]. Each node in the diagram is fully described described in [RFC8340]. Each node in the diagram is fully described
by the YANG module in Section 3.4. Please review the YANG module for by the YANG module in Section 3.4. Please review the YANG module for
a detailed description of the voucher-request format. a detailed description of the voucher-request format.
module: ietf-voucher-request module: ietf-voucher-request
grouping voucher-request-grouping grouping voucher-request-grouping
+-- voucher +-- voucher
+-- created-on? yang:date-and-time +-- created-on? yang:date-and-time
+-- expires-on? yang:date-and-time +-- expires-on? yang:date-and-time
+-- assertion? enumeration +-- assertion? enumeration
+-- serial-number string +-- serial-number string
+-- idevid-issuer? binary +-- idevid-issuer? binary
+-- pinned-domain-cert? binary +-- pinned-domain-cert? binary
+-- domain-cert-revocation-checks? boolean +-- domain-cert-revocation-checks? boolean
+-- nonce? binary +-- nonce? binary
+-- last-renewal-date? yang:date-and-time +-- last-renewal-date? yang:date-and-time
+-- prior-signed-voucher-request? binary +-- prior-signed-voucher-request? binary
+-- proximity-registrar-cert? binary +-- proximity-registrar-cert? binary
Figure 5: YANG Tree diagram for Voucher-Request Figure 5: YANG Tree Diagram for a Voucher-Request
3.3. Examples 3.3. Examples
This section provides voucher-request examples for illustration This section provides voucher-request examples for illustration
purposes. These examples show the JSON prior to CMS wrapping. JSON purposes. These examples show JSON prior to CMS wrapping. JSON
encoding rules specify that any binary content be base64 encoded encoding rules specify that any binary content be base64 encoded
([RFC4648] section 4). The contents of the (base64) encoded ([RFC4648], Section 4). The contents of the (base64) encoded
certificates have been elided to save space. For detailed examples, certificates have been elided to save space. For detailed examples,
see Appendix C.2. These examples conform to the encoding rules see Appendix C.2. These examples conform to the encoding rules
defined in [RFC7951]. defined in [RFC7951].
Example (1) The following example illustrates a pledge voucher- Example (1): The following example illustrates a pledge voucher-
request. The assertion leaf is indicated as 'proximity' request. The assertion leaf is indicated as
and the registrar's TLS server certificate is included "proximity", and the registrar's TLS server certificate
in the 'proximity-registrar-cert' leaf. See is included in the proximity-registrar-cert leaf. See
Section 5.2. Section 5.2.
{ {
"ietf-voucher-request:voucher": { "ietf-voucher-request:voucher": {
"assertion": "proximity", "assertion": "proximity",
"nonce": "62a2e7693d82fcda2624de58fb6722e5", "nonce": "62a2e7693d82fcda2624de58fb6722e5",
"serial-number" : "JADA123456789", "serial-number" : "JADA123456789",
"created-on": "2017-01-01T00:00:00.000Z", "created-on": "2017-01-01T00:00:00.000Z",
"proximity-registrar-cert": "base64encodedvalue==" "proximity-registrar-cert": "base64encodedvalue=="
} }
} }
Figure 6: JSON representation of example Voucher-Request Figure 6: JSON Representation of an Example Voucher-Request
Example (2) The following example illustrates a registrar voucher- Example (2): The following example illustrates a registrar voucher-
request. The 'prior-signed-voucher-request' leaf is request. The prior-signed-voucher-request leaf is
populated with the pledge's voucher-request (such as the populated with the pledge's voucher-request (such as
prior example). The pledge's voucher-request is a the prior example). The pledge's voucher-request is a
binary CMS signed object. In the JSON encoding used binary CMS-signed object. In the JSON encoding used
here it must be base64 encoded. The nonce and assertion here, it must be base64 encoded. The nonce and
have been carried forward from the pledge request to the assertion have been carried forward from the pledge
registrar request. The serial-number is extracted from request to the registrar request. The serial-number is
the pledge's Client Certificate from the TLS connection. extracted from the pledge's Client Certificate from the
See Section 5.5. TLS connection. See Section 5.5.
{ {
"ietf-voucher-request:voucher": { "ietf-voucher-request:voucher": {
"assertion" : "proximity", "assertion" : "proximity",
"nonce": "62a2e7693d82fcda2624de58fb6722e5", "nonce": "62a2e7693d82fcda2624de58fb6722e5",
"created-on": "2017-01-01T00:00:02.000Z", "created-on": "2017-01-01T00:00:02.000Z",
"idevid-issuer": "base64encodedvalue==", "idevid-issuer": "base64encodedvalue==",
"serial-number": "JADA123456789", "serial-number": "JADA123456789",
"prior-signed-voucher-request": "base64encodedvalue==" "prior-signed-voucher-request": "base64encodedvalue=="
} }
} }
Figure 7: JSON representation of example Prior-Signed Voucher-Request Figure 7: JSON Representation of an Example Prior-Signed Voucher-
Request
Example (3) The following example illustrates a registrar voucher- Example (3): The following example illustrates a registrar voucher-
request. The 'prior-signed-voucher-request' leaf is not request. The prior-signed-voucher-request leaf is not
populated with the pledge's voucher-request nor is the populated with the pledge's voucher-request nor is the
nonce leaf. This form might be used by a registrar nonce leaf. This form might be used by a registrar
requesting a voucher when the pledge can not communicate requesting a voucher when the pledge cannot communicate
with the registrar (such as when it is powered down, or with the registrar (such as when it is powered down or
still in packaging), and therefore could not submit a still in packaging) and therefore cannot submit a
nonce. This scenario is most useful when the registrar nonce. This scenario is most useful when the registrar
is aware that it will not be able to reach the MASA is aware that it will not be able to reach the MASA
during deployment. See Section 5.5. during deployment. See Section 5.5.
{ {
"ietf-voucher-request:voucher": { "ietf-voucher-request:voucher": {
"created-on": "2017-01-01T00:00:02.000Z", "created-on": "2017-01-01T00:00:02.000Z",
"idevid-issuer": "base64encodedvalue==", "idevid-issuer": "base64encodedvalue==",
"serial-number": "JADA123456789" "serial-number": "JADA123456789"
} }
} }
Figure 8: JSON representation of Offline Voucher-Request Figure 8: JSON Representation of an Offline Voucher-Request
3.4. YANG Module 3.4. YANG Module
Following is a YANG [RFC7950] module formally extending the [RFC8366] Following is a YANG module [RFC7950] that formally extends a voucher
voucher into a voucher-request. [RFC8366] into a voucher-request. This YANG module references
[ITU.X690].
<CODE BEGINS> file "ietf-voucher-request@2018-02-14.yang" <CODE BEGINS> file "ietf-voucher-request@2021-05-20.yang"
module ietf-voucher-request { module ietf-voucher-request {
yang-version 1.1; yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-voucher-request";
namespace prefix vcr;
"urn:ietf:params:xml:ns:yang:ietf-voucher-request";
prefix "vcr";
import ietf-restconf { import ietf-restconf {
prefix rc; prefix rc;
description "This import statement is only present to access description
"This import statement is only present to access
the yang-data extension defined in RFC 8040."; the yang-data extension defined in RFC 8040.";
reference "RFC 8040: RESTCONF Protocol"; reference
"RFC 8040: RESTCONF Protocol";
} }
import ietf-voucher { import ietf-voucher {
prefix vch; prefix vch;
description "This module defines the format for a voucher, description
which is produced by a pledge's manufacturer or "This module defines the format for a voucher,
delegate (MASA) to securely assign a pledge to which is produced by a pledge's manufacturer or
an 'owner', so that the pledge may establish a secure delegate (MASA) to securely assign a pledge to
connection to the owner's network infrastructure"; an 'owner', so that the pledge may establish a secure
connection to the owner's network infrastructure.";
reference "RFC 8366: Voucher Artifact for reference
Bootstrapping Protocols"; "RFC 8366: A Voucher Artifact for
Bootstrapping Protocols";
} }
organization organization
"IETF ANIMA Working Group"; "IETF ANIMA Working Group";
contact contact
"WG Web: <https://datatracker.ietf.org/wg/anima/> "WG Web: <https://datatracker.ietf.org/wg/anima/>
WG List: <mailto:anima@ietf.org> WG List: <mailto:anima@ietf.org>
Author: Kent Watsen Author: Kent Watsen
<mailto:kent+ietf@watsen.net> <mailto:kent+ietf@watsen.net>
Author: Michael H. Behringer Author: Michael H. Behringer
<mailto:Michael.H.Behringer@gmail.com> <mailto:Michael.H.Behringer@gmail.com>
Author: Toerless Eckert Author: Toerless Eckert
<mailto:tte+ietf@cs.fau.de> <mailto:tte+ietf@cs.fau.de>
Author: Max Pritikin Author: Max Pritikin
<mailto:pritikin@cisco.com> <mailto:pritikin@cisco.com>
Author: Michael Richardson Author: Michael Richardson
<mailto:mcr+ietf@sandelman.ca>"; <mailto:mcr+ietf@sandelman.ca>";
description description
"This module defines the format for a voucher request. "This module defines the format for a voucher-request.
It is a superset of the voucher itself. It is a superset of the voucher itself.
It provides content to the MASA for consideration It provides content to the MASA for consideration
during a voucher request. during a voucher-request.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as 'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here. they appear in all capitals, as shown here.
Copyright (c) 2019 IETF Trust and the persons identified as Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved. authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents Relating to IETF Documents
(http://trustee.ietf.org/license-info). (https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see the RFC This version of this YANG module is part of RFC 8995; see the
itself for full legal notices."; RFC itself for full legal notices.";
revision "2018-02-14" { revision 2021-05-20 {
description description
"Initial version"; "Initial version";
reference reference
"RFC XXXX: Bootstrapping Remote Secure Key Infrastructure"; "RFC 8995: Bootstrapping Remote Secure Key Infrastructure
(BRSKI)";
} }
// Top-level statement // Top-level statement
rc:yang-data voucher-request-artifact { rc:yang-data voucher-request-artifact {
uses voucher-request-grouping; uses voucher-request-grouping;
} }
// Grouping defined for future usage // Grouping defined for future usage
grouping voucher-request-grouping { grouping voucher-request-grouping {
description description
"Grouping to allow reuse/extensions in future work."; "Grouping to allow reuse/extensions in future work.";
uses vch:voucher-artifact-grouping { uses vch:voucher-artifact-grouping {
refine "voucher/created-on" { refine "voucher/created-on" {
mandatory false; mandatory false;
} }
refine "voucher/pinned-domain-cert" { refine "voucher/pinned-domain-cert" {
mandatory false; mandatory false;
description "A pinned-domain-cert field description
is not valid in a voucher request, and "A pinned-domain-cert field is not valid in a
any occurrence MUST be ignored"; voucher-request, and any occurrence MUST be ignored.";
} }
refine "voucher/last-renewal-date" { refine "voucher/last-renewal-date" {
description "A last-renewal-date field description
is not valid in a voucher request, and "A last-renewal-date field is not valid in a
any occurrence MUST be ignored"; voucher-request, and any occurrence MUST be ignored.";
} }
refine "voucher/domain-cert-revocation-checks" { refine "voucher/domain-cert-revocation-checks" {
description "The domain-cert-revocation-checks field description
is not valid in a voucher request, and "The domain-cert-revocation-checks field is not valid in a
any occurrence MUST be ignored"; voucher-request, and any occurrence MUST be ignored.";
} }
refine "voucher/assertion" { refine "voucher/assertion" {
mandatory false; mandatory false;
description "Any assertion included in registrar voucher description
requests SHOULD be ignored by the MASA."; "Any assertion included in registrar voucher-requests
SHOULD be ignored by the MASA.";
} }
augment "voucher" {
augment "voucher" {
description description
"Adds leaf nodes appropriate for requesting vouchers."; "Adds leaf nodes appropriate for requesting vouchers.";
leaf prior-signed-voucher-request { leaf prior-signed-voucher-request {
type binary; type binary;
description description
"If it is necessary to change a voucher, or re-sign and "If it is necessary to change a voucher, or re-sign and
forward a voucher that was previously provided along a forward a voucher that was previously provided along a
protocol path, then the previously signed voucher SHOULD protocol path, then the previously signed voucher SHOULD
be included in this field. be included in this field.
For example, a pledge might sign a voucher request For example, a pledge might sign a voucher-request
with a proximity-registrar-cert, and the registrar with a proximity-registrar-cert, and the registrar
then includes it as the prior-signed-voucher-request then includes it as the prior-signed-voucher-request
field. This is a simple mechanism for a chain of field. This is a simple mechanism for a chain of
trusted parties to change a voucher request, while trusted parties to change a voucher-request, while
maintaining the prior signature information. maintaining the prior signature information.
The Registrar and MASA MAY examine the prior signed The registrar and MASA MAY examine the prior-signed
voucher information for the voucher information for the
purposes of policy decisions. For example this purposes of policy decisions. For example, this
information could be useful to a MASA to determine information could be useful to a MASA to determine
that both pledge and registrar agree on proximity that both the pledge and registrar agree on proximity
assertions. The MASA SHOULD remove all assertions. The MASA SHOULD remove all
prior-signed-voucher-request information when prior-signed-voucher-request information when
signing a voucher for imprinting so as to minimize signing a voucher for imprinting so as to minimize
the final voucher size."; the final voucher size.";
} }
leaf proximity-registrar-cert { leaf proximity-registrar-cert {
type binary; type binary;
description description
"An X.509 v3 certificate structure as specified by "An X.509 v3 certificate structure, as specified by
RFC 5280, Section 4 encoded using the ASN.1 RFC 5280, Section 4, encoded using the ASN.1
distinguished encoding rules (DER), as specified distinguished encoding rules (DER), as specified
in [ITU.X690.1994]. in ITU X.690.
The first certificate in the Registrar TLS server The first certificate in the registrar TLS server
certificate_list sequence (the end-entity TLS certificate_list sequence (the end-entity TLS
certificate, see [RFC8446]) presented by the Registrar certificate; see RFC 8446) presented by the registrar
to the Pledge. to the pledge. This MUST be populated in a pledge's
This MUST be populated in a Pledge's voucher request voucher-request when a proximity assertion is
when a proximity assertion is requested."; requested.";
reference
"ITU X.690: Information Technology - ASN.1 encoding
rules: Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER)
RFC 5280: Internet X.509 Public Key Infrastructure
Certificate and Certificate Revocation List (CRL)
Profile
RFC 8446: The Transport Layer Security (TLS)
Protocol Version 1.3";
} }
} }
} }
} }
} }
<CODE ENDS> <CODE ENDS>
Figure 9: YANG module for Voucher-Request Figure 9: YANG Module for Voucher-Request
4. Proxying details (Pledge - Proxy - Registrar) 4. Proxying Details (Pledge -- Proxy -- Registrar)
This section is normative for uses with an ANIMA ACP. The use of the This section is normative for uses with an ANIMA ACP. The use of the
GRASP mechanism is part of the ACP. Other users of BRSKI will need GRASP mechanism is part of the ACP. Other users of BRSKI will need
to define an equivalent proxy mechanism, and an equivalent mechanism to define an equivalent proxy mechanism and an equivalent mechanism
to configure the proxy. to configure the proxy.
The role of the proxy is to facilitate communications. The proxy The role of the proxy is to facilitate communications. The proxy
forwards packets between the pledge and a registrar that has been forwards packets between the pledge and a registrar that has been
provisioned to the proxy via full GRASP ACP discovery. provisioned to the proxy via full GRASP ACP discovery.
This section defines a stateful proxy mechanism which is referred to This section defines a stateful proxy mechanism that is referred to
as a "circuit" proxy. This is a form of Application Level Gateway as a "circuit" proxy. This is a form of Application Level Gateway
([RFC2663] section 2.9). (see [RFC2663], Section 2.9).
The proxy does not terminate the TLS handshake: it passes streams of The proxy does not terminate the TLS handshake: it passes streams of
bytes onward without examination. A proxy MUST NOT assume any bytes onward without examination. A proxy MUST NOT assume any
specific TLS version. Please see [RFC8446] section 9.3 for details specific TLS version. Please see [RFC8446], Section 9.3 for details
on TLS invariants. on TLS invariants.
A Registrar can directly provide the proxy announcements described A registrar can directly provide the proxy announcements described
below, in which case the announced port can point directly to the below, in which case the announced port can point directly to the
Registrar itself. In this scenario the pledge is unaware that there registrar itself. In this scenario, the pledge is unaware that there
is no proxying occurring. This is useful for Registrars which are is no proxying occurring. This is useful for registrars that are
servicing pledges on directly connected networks. servicing pledges on directly connected networks.
As a result of the proxy Discovery process in Section 4.1.1, the port As a result of the proxy discovery process in Section 4.1.1, the port
number exposed by the proxy does not need to be well known, or number exposed by the proxy does not need to be well known or require
require an IANA allocation. an IANA allocation.
During the discovery of the Registrar by the Join Proxy, the Join During the discovery of the registrar by the Join Proxy, the Join
Proxy will also learn which kinds of proxy mechanisms are available. Proxy will also learn which kinds of proxy mechanisms are available.
This will allow the Join Proxy to use the lowest impact mechanism This will allow the Join Proxy to use the lowest impact mechanism
which the Join Proxy and Registrar have in common. that the Join Proxy and registrar have in common.
In order to permit the proxy functionality to be implemented on the In order to permit the proxy functionality to be implemented on the
maximum variety of devices the chosen mechanism should use the maximum variety of devices, the chosen mechanism should use the
minimum amount of state on the proxy device. While many devices in minimum amount of state on the proxy device. While many devices in
the ANIMA target space will be rather large routers, the proxy the ANIMA target space will be rather large routers, the proxy
function is likely to be implemented in the control plane CPU of such function is likely to be implemented in the control-plane CPU of such
a device, with available capabilities for the proxy function similar a device, with available capabilities for the proxy function similar
to many class 2 IoT devices. to many class 2 IoT devices.
The document [I-D.richardson-anima-state-for-joinrouter] provides a The document [ANIMA-STATE] provides a more extensive analysis and
more extensive analysis and background of the alternative proxy background of the alternative proxy methods.
methods.
4.1. Pledge discovery of Proxy 4.1. Pledge Discovery of Proxy
The result of discovery is a logical communication with a registrar, The result of discovery is a logical communication with a registrar,
through a proxy. The proxy is transparent to the pledge. The through a proxy. The proxy is transparent to the pledge. The
communication between the pledge and Join Proxy is over IPv6 Link- communication between the pledge and Join Proxy is over IPv6 link-
Local addresses. local addresses.
To discover the proxy the pledge performs the following actions: To discover the proxy, the pledge performs the following actions:
1. MUST: Obtains a local address using IPv6 methods as described in 1. MUST: Obtain a local address using IPv6 methods as described in
[RFC4862] IPv6 Stateless Address AutoConfiguration. Use of "IPv6 Stateless Address Autoconfiguration" [RFC4862]. Use of
[RFC4941] temporary addresses is encouraged. To limit pervasive temporary addresses [RFC8981] is encouraged. To limit pervasive
monitoring ( [RFC7258]), a new temporary address MAY use a short monitoring [RFC7258], a new temporary address MAY use a short
lifetime (that is, set TEMP_PREFERRED_LIFETIME to be short). lifetime (that is, set TEMP_PREFERRED_LIFETIME to be short).
Pledges will generally prefer use of IPv6 Link-Local addresses, Pledges will generally prefer use of IPv6 link-local addresses,
and discovery of proxy will be by Link-Local mechanisms. IPv4 and discovery of the proxy will be by link-local mechanisms.
methods are described in Appendix A IPv4 methods are described in Appendix A.
2. MUST: Listen for GRASP M_FLOOD ([I-D.ietf-anima-grasp]) 2. MUST: Listen for GRASP M_FLOOD [RFC8990] announcements of the
announcements of the objective: "AN_Proxy". See section objective: "AN_Proxy". See Section 4.1.1 for the details of the
Section 4.1.1 for the details of the objective. The pledge MAY objective. The pledge MAY listen concurrently for other sources
listen concurrently for other sources of information, see of information; see Appendix B.
Appendix B.
Once a proxy is discovered the pledge communicates with a registrar Once a proxy is discovered, the pledge communicates with a registrar
through the proxy using the bootstrapping protocol defined in through the proxy using the bootstrapping protocol defined in
Section 5. Section 5.
While the GRASP M_FLOOD mechanism is passive for the pledge, the non- While the GRASP M_FLOOD mechanism is passive for the pledge, the non-
normative other methods (mDNS, and IPv4 methods) described in normative other methods (mDNS and IPv4 methods) described in
Appendix B are active. The pledge SHOULD run those methods in Appendix B are active. The pledge SHOULD run those methods in
parallel with listening to for the M_FLOOD. The active methods parallel with listening for the M_FLOOD. The active methods SHOULD
SHOULD back-off by doubling to a maximum of one hour to avoid back off by doubling to a maximum of one hour to avoid overloading
overloading the network with discovery attempts. Detection of change the network with discovery attempts. Detection of physical link
of physical link status (Ethernet carrier for instance) SHOULD reset status change (Ethernet carrier, for instance) SHOULD reset the back-
the back off timers. off timers.
The pledge could discover more than one proxy on a given physical The pledge could discover more than one proxy on a given physical
interface. The pledge can have a multitude of physical interfaces as interface. The pledge can have a multitude of physical interfaces as
well: a layer-2/3 Ethernet switch may have hundreds of physical well: a Layer 2/3 Ethernet switch may have hundreds of physical
ports. ports.
Each possible proxy offer SHOULD be attempted up to the point where a Each possible proxy offer SHOULD be attempted up to the point where a
valid voucher is received: while there are many ways in which the valid voucher is received: while there are many ways in which the
attempt may fail, it does not succeed until the voucher has been attempt may fail, it does not succeed until the voucher has been
validated. validated.
The connection attempts via a single proxy SHOULD exponentially back- The connection attempts via a single proxy SHOULD exponentially back
off to a maximum of one hour to avoid overloading the network off to a maximum of one hour to avoid overloading the network
infrastructure. The back-off timer for each MUST be independent of infrastructure. The back-off timer for each MUST be independent of
other connection attempts. other connection attempts.
Connection attempts SHOULD be run in parallel to avoid head of queue Connection attempts SHOULD be run in parallel to avoid head-of-queue
problems wherein an attacker running a fake proxy or registrar could problems wherein an attacker running a fake proxy or registrar could
perform protocol actions intentionally slowly. Connection attempts intentionally perform protocol actions slowly. Connection attempts
to different proxies SHOULD be sent with an interval of 3 to 5s. The to different proxies SHOULD be sent with an interval of 3 to 5s. The
pledge SHOULD continue to listen to for additional GRASP M_FLOOD pledge SHOULD continue to listen for additional GRASP M_FLOOD
messages during the connection attempts. messages during the connection attempts.
Each connection attempt through a distinct Join Proxy MUST have a Each connection attempt through a distinct Join Proxy MUST have a
unique nonce in the voucher-request. unique nonce in the voucher-request.
Once a connection to a registrar is established (e.g. establishment Once a connection to a registrar is established (e.g., establishment
of a TLS session key) there are expectations of more timely of a TLS session key), there are expectations of more timely
responses, see Section 5.2. responses; see Section 5.2.
Once all discovered services are attempted (assuming that none Once all discovered services are attempted (assuming that none
succeeded) the device MUST return to listening for GRASP M_FLOOD. It succeeded), the device MUST return to listening for GRASP M_FLOOD.
SHOULD periodically retry any manufacturer-specific mechanisms. The It SHOULD periodically retry any manufacturer-specific mechanisms.
pledge MAY prioritize selection order as appropriate for the The pledge MAY prioritize selection order as appropriate for the
anticipated environment. anticipated environment.
4.1.1. Proxy GRASP announcements 4.1.1. Proxy GRASP Announcements
A proxy uses the DULL GRASP M_FLOOD mechanism to announce itself. A proxy uses the DULL GRASP M_FLOOD mechanism to announce itself.
This announcement can be within the same message as the ACP This announcement can be within the same message as the ACP
announcement detailed in [I-D.ietf-anima-autonomic-control-plane]. announcement detailed in [RFC8994].
The formal Concise Data Definition Language (CDDL) [RFC8610] The formal Concise Data Definition Language (CDDL) [RFC8610]
definition is: definition is:
<CODE BEGINS> file "proxygrasp.cddl" <CODE BEGINS> file "proxygrasp.cddl"
flood-message = [M_FLOOD, session-id, initiator, ttl, flood-message = [M_FLOOD, session-id, initiator, ttl,
+[objective, (locator-option / [])]] +[objective, (locator-option / [])]]
objective = ["AN_Proxy", objective-flags, loop-count, objective = ["AN_Proxy", objective-flags, loop-count,
objective-value] objective-value]
ttl = 180000 ; 180,000 ms (3 minutes) ttl = 180000 ; 180,000 ms (3 minutes)
initiator = ACP address to contact Registrar initiator = ACP address to contact registrar
objective-flags = sync-only ; as in GRASP spec objective-flags = sync-only ; as in the GRASP spec
sync-only = 4 ; M_FLOOD only requires synchronization sync-only = 4 ; M_FLOOD only requires
; synchronization
loop-count = 1 ; one hop only loop-count = 1 ; one hop only
objective-value = any ; none objective-value = any ; none
locator-option = [ O_IPv6_LOCATOR, ipv6-address, locator-option = [ O_IPv6_LOCATOR, ipv6-address,
transport-proto, port-number ] transport-proto, port-number ]
ipv6-address = the v6 LL of the Proxy ipv6-address = the v6 LL of the Proxy
$transport-proto /= IPPROTO_TCP ; note this can be any value from the $transport-proto /= IPPROTO_TCP ; note that this can be any value
; IANA protocol registry, as per ; from the IANA protocol registry,
; [GRASP] section 2.9.5.1, note 3. ; as per RFC 8990, Section 2.9.5.1,
; Note 3.
port-number = selected by Proxy port-number = selected by Proxy
<CODE ENDS> <CODE ENDS>
Figure 10: CDDL definition of Proxy Discovery message Figure 10: CDDL Definition of Proxy Discovery Message
Here is an example M_FLOOD announcing a proxy at fe80::1, on TCP port Here is an example M_FLOOD announcing a proxy at fe80::1, on TCP port
4443. 4443.
[M_FLOOD, 12340815, h'fe800000000000000000000000000001', 180000, [M_FLOOD, 12340815, h'fe800000000000000000000000000001', 180000,
[["AN_Proxy", 4, 1, ""], [["AN_Proxy", 4, 1, ""],
[O_IPv6_LOCATOR, [O_IPv6_LOCATOR,
h'fe800000000000000000000000000001', IPPROTO_TCP, 4443]]] h'fe800000000000000000000000000001', IPPROTO_TCP, 4443]]]
Figure 11: Example of Proxy Discovery message Figure 11: Example of Proxy Discovery Message
On a small network the Registrar MAY include the GRASP M_FLOOD On a small network, the registrar MAY include the GRASP M_FLOOD
announcements to locally connected networks. announcements to locally connected networks.
The $transport-proto above indicates the method that the pledge- The $transport-proto above indicates the method that the pledge-
proxy-registrar will use. The TCP method described here is proxy-registrar will use. The TCP method described here is
mandatory, and other proxy methods, such as CoAP methods not defined mandatory, and other proxy methods, such as CoAP methods not defined
in this document are optional. Other methods MUST NOT be enabled in this document, are optional. Other methods MUST NOT be enabled
unless the Join Registrar ASA indicates support for them in it's own unless the Join Registrar ASA indicates support for them in its own
announcement. announcement.
4.2. CoAP connection to Registrar 4.2. CoAP Connection to Registrar
The use of CoAP to connect from pledge to registrar is out of scope The use of CoAP to connect from pledge to registrar is out of scope
for this document, and is described in future work. See for this document and is described in future work. See
[I-D.ietf-anima-constrained-voucher]. [ANIMA-CONSTRAINED-VOUCHER].
4.3. Proxy discovery and communication of Registrar 4.3. Proxy Discovery and Communication of Registrar
The registrar SHOULD announce itself so that proxies can find it and The registrar SHOULD announce itself so that proxies can find it and
determine what kind of connections can be terminated. determine what kind of connections can be terminated.
The registrar announces itself using ACP instance of GRASP using The registrar announces itself using GRASP M_FLOOD messages, with the
M_FLOOD messages, with the "AN_join_registrar" objective. A "AN_join_registrar" objective, within the ACP instance. A registrar
registrar may announce any convenient port number, including using a may announce any convenient port number, including use of stock port
stock port 443. ANI proxies MUST support GRASP discovery of 443. ANI proxies MUST support GRASP discovery of registrars.
registrars.
The M_FLOOD is formatted as follows: The M_FLOOD is formatted as follows:
[M_FLOOD, 51804321, h'fda379a6f6ee00000200000064000001', 180000, [M_FLOOD, 51804321, h'fda379a6f6ee00000200000064000001', 180000,
[["AN_join_registrar", 4, 255, "EST-TLS"], [["AN_join_registrar", 4, 255, "EST-TLS"],
[O_IPv6_LOCATOR, [O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_TCP, 8443]]] h'fda379a6f6ee00000200000064000001', IPPROTO_TCP, 8443]]]
Figure 12: An example of a Registrar announcement message Figure 12: An Example of a Registrar Announcement Message
The formal CDDL definition is: The formal CDDL definition is:
<CODE BEGINS> file "jrcgrasp.cddl" <CODE BEGINS> file "jrcgrasp.cddl"
flood-message = [M_FLOOD, session-id, initiator, ttl, flood-message = [M_FLOOD, session-id, initiator, ttl,
+[objective, (locator-option / [])]] +[objective, (locator-option / [])]]
objective = ["AN_join_registrar", objective-flags, loop-count, objective = ["AN_join_registrar", objective-flags, loop-count,
objective-value] objective-value]
initiator = ACP address to contact Registrar initiator = ACP address to contact registrar
objective-flags = sync-only ; as in GRASP spec objective-flags = sync-only ; as in the GRASP spec
sync-only = 4 ; M_FLOOD only requires synchronization sync-only = 4 ; M_FLOOD only requires
; synchronization
loop-count = 255 ; mandatory maximum loop-count = 255 ; mandatory maximum
objective-value = text ; name of the (list of) of supported objective-value = text ; name of the (list of) supported
; protocols: "EST-TLS" for RFC7030. ; protocols: "EST-TLS" for RFC 7030.
<CODE ENDS> <CODE ENDS>
Figure 13: CDDL definition for Registrar announcement message Figure 13: CDDL Definition for Registrar Announcement Message
The M_FLOOD message MUST be sent periodically. The default period The M_FLOOD message MUST be sent periodically. The default period
SHOULD be 60 seconds, the value SHOULD be operator configurable but SHOULD be 60 seconds, and the value SHOULD be operator configurable
SHOULD NOT be smaller than 60 seconds. The frequency of sending MUST but SHOULD NOT be smaller than 60 seconds. The frequency of sending
be such that the aggregate amount of periodic M_FLOODs from all MUST be such that the aggregate amount of periodic M_FLOODs from all
flooding sources cause only negligible traffic across the ACP. flooding sources causes only negligible traffic across the ACP.
Here are some examples of locators for illustrative purposes. Only Here are some examples of locators for illustrative purposes. Only
the first one ($transport-protocol = 6, TCP) is defined in this the first one ($transport-protocol = 6, TCP) is defined in this
document and is mandatory to implement. document and is mandatory to implement.
locator1 = [O_IPv6_LOCATOR, fd45:1345::6789, 6, 443] locator1 = [O_IPv6_LOCATOR, fd45:1345::6789, 6, 443]
locator2 = [O_IPv6_LOCATOR, fd45:1345::6789, 17, 5683] locator2 = [O_IPv6_LOCATOR, fd45:1345::6789, 17, 5683]
locator3 = [O_IPv6_LOCATOR, fe80::1234, 41, nil] locator3 = [O_IPv6_LOCATOR, fe80::1234, 41, nil]
A protocol of 6 indicates that TCP proxying on the indicated port is A protocol of 6 indicates that TCP proxying on the indicated port is
desired. desired.
Registrars MUST announce the set of protocols that they support. Registrars MUST announce the set of protocols that they support, and
They MUST support TCP traffic. they MUST support TCP traffic.
Registrars MUST accept HTTPS/EST traffic on the TCP ports indicated. Registrars MUST accept HTTPS/EST traffic on the TCP ports indicated.
Registrars MUST support ANI TLS circuit proxy and therefore BRSKI Registrars MUST support the ANI TLS Circuit Proxy and therefore BRSKI
across HTTPS/TLS native across the ACP. across HTTPS/TLS native across the ACP.
In the ANI, the Autonomic Control Plane (ACP) secured instance of In the ANI, the ACP-secured instance of GRASP [RFC8990] MUST be used
GRASP ([I-D.ietf-anima-grasp]) MUST be used for discovery of ANI for discovery of ANI registrar ACP addresses and ports by ANI
registrar ACP addresses and ports by ANI proxies. The TCP leg of the proxies. Therefore, the TCP leg of the proxy connection between the
proxy connection between ANI proxy and ANI registrar therefore also ANI proxy and ANI registrar also runs across the ACP.
runs across the ACP.
5. Protocol Details (Pledge - Registrar - MASA) 5. Protocol Details (Pledge -- Registrar -- MASA)
The pledge MUST initiate BRSKI after boot if it is unconfigured. The The pledge MUST initiate BRSKI after boot if it is unconfigured. The
pledge MUST NOT automatically initiate BRSKI if it has been pledge MUST NOT automatically initiate BRSKI if it has been
configured or is in the process of being configured. configured or is in the process of being configured.
BRSKI is described as extensions to EST [RFC7030]. The goal of these BRSKI is described as extensions to EST [RFC7030]. The goal of these
extensions is to reduce the number of TLS connections and crypto extensions is to reduce the number of TLS connections and crypto
operations required on the pledge. The registrar implements the operations required on the pledge. The registrar implements the
BRSKI REST interface within the "/.well-known/brski" URI tree, as BRSKI REST interface within the "/.well-known/brski" URI tree and
well as implementing the existing EST URIs as described in EST implements the existing EST URIs as described in EST [RFC7030],
[RFC7030] section 3.2.2. The communication channel between the Section 3.2.2. The communication channel between the pledge and the
pledge and the registrar is referred to as "BRSKI-EST" (see registrar is referred to as "BRSKI-EST" (see Figure 1).
Figure 1).
The communication channel between the registrar and MASA is a new The communication channel between the registrar and MASA is a new
communication channel, similar to EST, within the newly registred communication channel, similar to EST, within the newly registered
"/.well-known/brski" tree. For clarity this channel is referred to "/.well-known/brski" tree. For clarity, this channel is referred to
as "BRSKI-MASA". (See Figure 1). as "BRSKI-MASA" (see Figure 1).
The MASA URI is "https://" authority "/.well-known/brski". The MASA URI is "https://" authority "/.well-known/brski".
BRSKI uses existing CMS message formats for existing EST operations. BRSKI uses existing CMS message formats for existing EST operations.
BRSKI uses JSON [RFC8259] for all new operations defined here, and BRSKI uses JSON [RFC8259] for all new operations defined here and for
voucher formats. In all places where a binary value must be carried voucher formats. In all places where a binary value must be carried
in a JSON string, the use of base64 format ([RFC4648] section 4) is in a JSON string, a base64 format ([RFC4648], Section 4) is to be
to be used, as per [RFC7951] section 6.6. used, as per [RFC7951], Section 6.6.
While EST section 3.2 does not insist upon use of HTTP persistent While EST ([RFC7030], Section 3.2) does not insist upon use of HTTP
connections ([RFC7230] section 6.3), BRSKI-EST connections SHOULD use persistent connections ([RFC7230], Section 6.3), BRSKI-EST
persistent connections. The intention of this guidance is to ensure connections SHOULD use persistent connections. The intention of this
the provisional TLS state occurs only once, and that the subsequent guidance is to ensure the provisional TLS state occurs only once, and
resolution of the provision state is not subject to a MITM attack that the subsequent resolution of the provision state is not subject
during a critical phase. to a Man-in-the-Middle (MITM) attack during a critical phase.
If non-persistent connections are used, then both the pledge and the If non-persistent connections are used, then both the pledge and the
registrar MUST remember the certificates seen, and also sent for the registrar MUST remember the certificates that have been seen and also
first connection. They MUST check each subsequent connections for sent for the first connection. They MUST check each subsequent
the same certificates, and each end MUST use the same certificates as connection for the same certificates, and each end MUST use the same
well. This places a difficult restriction on rolling certificates on certificates as well. This places a difficult restriction on rolling
the Registrar. certificates on the registrar.
Summarized automation extensions for the BRSKI-EST flow are: Summarized automation extensions for the BRSKI-EST flow are:
* The pledge either attempts concurrent connections via each * The pledge either attempts concurrent connections via each
discovered proxy, or it times out quickly and tries connections in discovered proxy or times out quickly and tries connections in
series, as explained at the end of Section 5.1. series, as explained at the end of Section 5.1.
* The pledge provisionally accepts the registrar certificate during * The pledge provisionally accepts the registrar certificate during
the TLS handshake as detailed in Section 5.1. the TLS handshake as detailed in Section 5.1.
* The pledge requests a voucher using the new REST calls described * The pledge requests a voucher using the new REST calls described
below. This voucher is then validated. below. This voucher is then validated.
* The pledge completes authentication of the server certificate as * The pledge completes authentication of the server certificate as
detailed in Section 5.6.1. This moves the BRSKI-EST TLS detailed in Section 5.6.1. This moves the BRSKI-EST TLS
connection out of the provisional state. connection out of the provisional state.
* Mandatory bootstrap steps conclude with voucher status telemetry * Mandatory bootstrap steps conclude with voucher status telemetry
(see Section 5.7). (see Section 5.7).
The BRSKI-EST TLS connection can now be used for EST enrollment. The BRSKI-EST TLS connection can now be used for EST enrollment.
The extensions for a registrar (equivalent to EST server) are: The extensions for a registrar (equivalent to an EST server) are:
* Client authentication is automated using Initial Device Identity * Client authentication is automated using IDevID as per the EST
(IDevID) as per the EST certificate based client authentication. certificate-based client authentication. The subject field's DN
The subject field's DN encoding MUST include the "serialNumber" encoding MUST include the "serialNumber" attribute with the
attribute with the device's unique serial number as explained in device's unique serial number as explained in Section 2.3.1.
Section 2.3.1
* The registrar requests and validates the voucher from the MASA. * The registrar requests and validates the voucher from the MASA.
* The registrar forwards the voucher to the pledge when requested. * The registrar forwards the voucher to the pledge when requested.
* The registrar performs log verifications (described in * The registrar performs log verifications (described in
Section 5.8.3) in addition to local authorization checks before Section 5.8.3) in addition to local authorization checks before
accepting optional pledge device enrollment requests. accepting optional pledge device enrollment requests.
5.1. BRSKI-EST TLS establishment details 5.1. BRSKI-EST TLS Establishment Details
The pledge establishes the TLS connection with the registrar through The pledge establishes the TLS connection with the registrar through
the circuit proxy (see Section 4) but the TLS handshake is with the the Circuit Proxy (see Section 4), but the TLS handshake is with the
registrar. The BRSKI-EST pledge is the TLS client and the BRSKI-EST registrar. The BRSKI-EST pledge is the TLS client, and the BRSKI-EST
registrar is the TLS server. All security associations established registrar is the TLS server. All security associations established
are between the pledge and the registrar regardless of proxy are between the pledge and the registrar regardless of proxy
operations. operations.
Use of TLS 1.3 (or newer) is encouraged. TLS 1.2 or newer is Use of TLS 1.3 (or newer) is encouraged. TLS 1.2 or newer is
REQUIRED on the Pledge side. TLS 1.3 (or newer) SHOULD be available REQUIRED on the pledge side. TLS 1.3 (or newer) SHOULD be available
on the Registrar server interface, and the Registrar client on the registrar server interface, and the registrar client
interface, but TLS 1.2 MAY be used. TLS 1.3 (or newer) SHOULD be interface, but TLS 1.2 MAY be used. TLS 1.3 (or newer) SHOULD be
available on the MASA server interface, but TLS 1.2 MAY be used. available on the MASA server interface, but TLS 1.2 MAY be used.
Establishment of the BRSKI-EST TLS connection is as specified in EST Establishment of the BRSKI-EST TLS connection is as specified in
[RFC7030] section 4.1.1 "Bootstrap Distribution of CA Certificates" "Bootstrap Distribution of CA Certificates" (Section 4.1.1) of
[RFC7030] wherein the client is authenticated with the IDevID [RFC7030], wherein the client is authenticated with the IDevID
certificate, and the EST server (the registrar) is provisionally certificate, and the EST server (the registrar) is provisionally
authenticated with an unverified server certificate. Configuration authenticated with an unverified server certificate. Configuration
or distribution of the trust anchor database used for validating the or distribution of the trust anchor database used for validating the
IDevID certificate is out-of-scope of this specification. Note that IDevID certificate is out of scope of this specification. Note that
the trust anchors in/excluded from the database will affect which the trust anchors in / excluded from the database will affect which
manufacturers' devices are acceptable to the registrar as pledges, manufacturers' devices are acceptable to the registrar as pledges and
and can also be used to limit the set of MASAs that are trusted for can also be used to limit the set of MASAs that are trusted for
enrollment. enrollment.
The signature in the certificate MUST be validated even if a signing The signature in the certificate MUST be validated even if a signing
key can not (yet) be validated. The certificate (or chain) MUST be key cannot (yet) be validated. The certificate (or chain) MUST be
retained for later validation. retained for later validation.
A self-signed certificate for the Registrar is acceptable as the A self-signed certificate for the registrar is acceptable as the
voucher can validate it upon successful enrollment. voucher can validate it upon successful enrollment.
The pledge performs input validation of all data received until a The pledge performs input validation of all data received until a
voucher is verified as specified in Section 5.6.1 and the TLS voucher is verified as specified in Section 5.6.1 and the TLS
connection leaves the provisional state. Until these operations are connection leaves the provisional state. Until these operations are
complete the pledge could be communicating with an attacker. complete, the pledge could be communicating with an attacker.
The pledge code needs to be written with the assumption that all data The pledge code needs to be written with the assumption that all data
is being transmitted at this point to an unauthenticated peer, and is being transmitted at this point to an unauthenticated peer, and
that received data, while inside a TLS connection, MUST be considered that received data, while inside a TLS connection, MUST be considered
untrusted. This particularly applies to HTTP headers and CMS untrusted. This particularly applies to HTTP headers and CMS
structures that make up the voucher. structures that make up the voucher.
A pledge that can connect to multiple Registrars concurrently SHOULD A pledge that can connect to multiple registrars concurrently SHOULD
do so. Some devices may be unable to do so for lack of threading, or do so. Some devices may be unable to do so for lack of threading, or
resource issues. Concurrent connections defeat attempts by a resource issues. Concurrent connections defeat attempts by a
malicious proxy from causing a TCP Slowloris-like attack (see malicious proxy from causing a TCP Slowloris-like attack (see
[slowloris]). [slowloris]).
A pledge that can not maintain as many connections as there are A pledge that cannot maintain as many connections as there are
eligible proxies will need to rotate among the various choices, eligible proxies will need to rotate among the various choices,
terminating connections that do not appear to be making progress. If terminating connections that do not appear to be making progress. If
no connection is making progress after 5 seconds then the pledge no connection is making progress after 5 seconds, then the pledge
SHOULD drop the oldest connection and go on to a different proxy: the SHOULD drop the oldest connection and go on to a different proxy: the
proxy that has been communicated with least recently. If there were proxy that has been communicated with least recently. If there were
no other proxies discovered, the pledge MAY continue to wait, as long no other proxies discovered, the pledge MAY continue to wait, as long
as it is concurrently listening for new proxy announcements. as it is concurrently listening for new proxy announcements.
5.2. Pledge Requests Voucher from the Registrar 5.2. Pledge Requests Voucher from the Registrar
When the pledge bootstraps it makes a request for a voucher from a When the pledge bootstraps, it makes a request for a voucher from a
registrar. registrar.
This is done with an HTTPS POST using the operation path value of This is done with an HTTPS POST using the operation path value of
"/.well-known/brski/requestvoucher". "/.well-known/brski/requestvoucher".
The pledge voucher-request Content-Type is: The pledge voucher-request Content-Type is as follows.
application/voucher-cms+json [RFC8366] defines a "YANG-defined JSON application/voucher-cms+json: [RFC8366] defines a "YANG-defined JSON
document that has been signed using a CMS structure", and the document that has been signed using a Cryptographic Message Syntax
voucher-request described in Section 3 is created in the same way. (CMS) structure", and the voucher-request described in Section 3
The media type is the same as defined in [RFC8366]. This is also is created in the same way. The media type is the same as defined
used for the pledge voucher-request. The pledge MUST sign the in [RFC8366]. This is also used for the pledge voucher-request.
request using the Section 2.3 credential. The pledge MUST sign the request using the credentials in
Section 2.3.
Registrar implementations SHOULD anticipate future media types but of Registrar implementations SHOULD anticipate future media types but,
course will simply fail the request if those types are not yet known. of course, will simply fail the request if those types are not yet
known.
The pledge SHOULD include an [RFC7231] section 5.3.2 "Accept" header The pledge SHOULD include an "Accept" header field (see [RFC7231],
field indicating the acceptable media type for the voucher response. Section 5.3.2) indicating the acceptable media type for the voucher
The "application/voucher-cms+json" media type is defined in [RFC8366] response. The "application/voucher-cms+json" media type is defined
but constrained voucher formats are expected in the future. in [RFC8366], but constrained voucher formats are expected in the
Registrars and MASA are expected to be flexible in what they accept. future. Registrars and MASA are expected to be flexible in what they
accept.
The pledge populates the voucher-request fields as follows: The pledge populates the voucher-request fields as follows:
created-on: Pledges that have a realtime clock are RECOMMENDED to created-on: Pledges that have a real-time clock are RECOMMENDED to
populate this field with the current date and time in yang:date- populate this field with the current date and time in yang:date-
and-time format. This provides additional information to the and-time format. This provides additional information to the
MASA. Pledges that have no real-time clocks MAY omit this field. MASA. Pledges that have no real-time clocks MAY omit this field.
nonce: The pledge voucher-request MUST contain a cryptographically nonce: The pledge voucher-request MUST contain a cryptographically
strong random or pseudo-random number nonce (see [RFC4086] section strong random or pseudo-random number nonce (see [RFC4086],
6.2). As the nonce is usually generated very early in the boot Section 6.2). As the nonce is usually generated very early in the
sequence there is a concern that the same nonce might generated boot sequence, there is a concern that the same nonce might be
across multiple boots, or after a factory reset. Different nonces generated across multiple boots, or after a factory reset.
MUST be generated for each bootstrapping attempt, whether in Different nonces MUST be generated for each bootstrapping attempt,
series or concurrently. The freshness of this nonce mitigates whether in series or concurrently. The freshness of this nonce
against the lack of real-time clock as explained in Section 2.6.1. mitigates against the lack of a real-time clock as explained in
Section 2.6.1.
assertion: The pledge indicates support for the mechanism described assertion: The pledge indicates support for the mechanism described
in this document, by putting the value "proximity" in the voucher- in this document, by putting the value "proximity" in the voucher-
request, MUST include the "proximity-registrar-cert" field request, and MUST include the proximity-registrar-cert field
(below). (below).
proximity-registrar-cert: In a pledge voucher-request this is the proximity-registrar-cert: In a pledge voucher-request, this is the
first certificate in the TLS server 'certificate_list' sequence first certificate in the TLS server "certificate_list" sequence
(see [RFC5246]) presented by the registrar to the pledge. That (see [RFC8446], Section 4.4.2) presented by the registrar to the
is, it is the end-entity certificate. This MUST be populated in a pledge. That is, it is the end-entity certificate. This MUST be
pledge voucher-request. populated in a pledge voucher-request.
serial-number The serial number of the pledge is included in the serial-number: The serial number of the pledge is included in the
voucher-request from the Pledge. This value is included as a voucher-request from the pledge. This value is included as a
sanity check only, but it is not to be forwarded by the Registrar sanity check only, but it is not to be forwarded by the registrar
as described in Section 5.5. as described in Section 5.5.
All other fields MAY be omitted in the pledge voucher-request. All other fields MAY be omitted in the pledge voucher-request.
An example JSON payload of a pledge voucher-request is in Section 3.3 See an example JSON payload of a pledge voucher-request in
Example 1. Section 3.3, Example 1.
The registrar confirms that the assertion is 'proximity' and that The registrar confirms that the assertion is "proximity" and that
pinned 'proximity-registrar-cert' is the Registrar's certificate. If pinned proximity-registrar-cert is the registrar's certificate. If
this validation fails, then there is an On-Path Attacker (MITM), and this validation fails, then there is an on-path attacker (MITM), and
the connection MUST be closed after the returning an HTTP 401 error the connection MUST be closed after the returning of an HTTP 401
code. error code.
5.3. Registrar Authorization of Pledge 5.3. Registrar Authorization of Pledge
In a fully automated network all devices must be securely identified In a fully automated network, all devices must be securely identified
and authorized to join the domain. and authorized to join the domain.
A Registrar accepts or declines a request to join the domain, based A registrar accepts or declines a request to join the domain, based
on the authenticated identity presented. For different networks, on the authenticated identity presented. For different networks,
examples of automated acceptance may include: examples of automated acceptance may include the allowance of:
* allow any device of a specific type (as determined by the X.509 * any device of a specific type (as determined by the X.509 IDevID),
IDevID),
* allow any device from a specific vendor (as determined by the * any device from a specific vendor (as determined by the X.509
X.509 IDevID), IDevID),
* allow a specific device from a vendor (as determined by the X.509 * a specific device from a vendor (as determined by the X.509
IDevID) against a domain white list. (The mechanism for checking IDevID) against a domain acceptlist. (The mechanism for checking
a shared white list potentially used by multiple Registrars is out a shared acceptlist potentially used by multiple registrars is out
of scope). of scope.)
If validation fails the registrar SHOULD respond with the HTTP 404 If validation fails, the registrar SHOULD respond with the HTTP 404
error code. If the voucher-request is in an unknown format, then an error code. If the voucher-request is in an unknown format, then an
HTTP 406 error code is more appropriate. A situation that could be HTTP 406 error code is more appropriate. A situation that could be
resolved with administrative action (such as adding a vendor to a resolved with administrative action (such as adding a vendor to an
whitelist) MAY be responded with an 403 HTTP error code. acceptlist) MAY be responded to with a 403 HTTP error code.
If authorization is successful the registrar obtains a voucher from If authorization is successful, the registrar obtains a voucher from
the MASA service (see Section 5.5) and returns that MASA signed the MASA service (see Section 5.5) and returns that MASA-signed
voucher to the pledge as described in Section 5.6. voucher to the pledge as described in Section 5.6.
5.4. BRSKI-MASA TLS establishment details 5.4. BRSKI-MASA TLS Establishment Details
The BRSKI-MASA TLS connection is a 'normal' TLS connection The BRSKI-MASA TLS connection is a "normal" TLS connection
appropriate for HTTPS REST interfaces. The registrar initiates the appropriate for HTTPS REST interfaces. The registrar initiates the
connection and uses the MASA URL obtained as described in connection and uses the MASA URL that is obtained as described in
Section 2.8. The mechanisms in [RFC6125] SHOULD be used in Section 2.8. The mechanisms in [RFC6125] SHOULD be used in
authentication of the MASA using a DNS-ID that matches that which is authentication of the MASA using a DNS-ID that matches that which is
found in the IDevID. Registrars MAY include a mechanism to override found in the IDevID. Registrars MAY include a mechanism to override
the MASA URL on a manufacturer-by-manufacturer basis, and within that the MASA URL on a manufacturer-by-manufacturer basis, and within that
override it is appropriate to provide alternate anchors. This will override, it is appropriate to provide alternate anchors. This will
typically used by some vendors to establish explicit (or private) typically be used by some vendors to establish explicit (or private)
trust anchors for validating their MASA that is part of a sales trust anchors for validating their MASA that is part of a sales
channel integration. channel integration.
Use of TLS 1.3 (or newer) is encouraged. TLS 1.2 or newer is Use of TLS 1.3 (or newer) is encouraged. TLS 1.2 or newer is
REQUIRED. TLS 1.3 (or newer) SHOULD be available. REQUIRED. TLS 1.3 (or newer) SHOULD be available.
As described in [RFC7030], the MASA and the registrars SHOULD be As described in [RFC7030], the MASA and the registrars SHOULD be
prepared to support TLS client certificate authentication and/or HTTP prepared to support TLS Client Certificate authentication and/or HTTP
Basic, Digest, or SCRAM authentication. This connection MAY also Basic, Digest, or Salted Challenge Response Authentication Mechanism
have no client authentication at all. (SCRAM) authentication. This connection MAY also have no client
authentication at all.
Registrars SHOULD permit trust anchors to be pre-configured on a per- Registrars SHOULD permit trust anchors to be preconfigured on a per-
vendor(MASA) basis. Registrars SHOULD include the ability to vendor (MASA) basis. Registrars SHOULD include the ability to
configure a TLS ClientCertificate on a per-MASA basis, or to use no configure a TLS Client Certificate on a per-MASA basis, or to use no
client certificate. Registrars SHOULD also permit HTTP Basic and Client Certificate. Registrars SHOULD also permit HTTP Basic and
Digest authentication to be configured. Digest authentication to be configured.
The authentication of the BRSKI-MASA connection does not change the The authentication of the BRSKI-MASA connection does not change the
voucher-request process, as voucher-requests are already signed by voucher-request process, as voucher-requests are already signed by
the registrar. Instead, this authentication provides access control the registrar. Instead, this authentication provides access control
to the audit-log as described in Section 5.8. to the audit-log as described in Section 5.8.
Implementors are advised that contacting the MASA is to establish a Implementers are advised that contacting the MASA establishes a
secured API connection with a web service and that there are a number secured API connection with a web service, and that there are a
of authentication models being explored within the industry. number of authentication models being explored within the industry.
Registrars are RECOMMENDED to fail gracefully and generate useful Registrars are RECOMMENDED to fail gracefully and generate useful
administrative notifications or logs in the advent of unexpected HTTP administrative notifications or logs in the advent of unexpected HTTP
401 (Unauthorized) responses from the MASA. 401 (Unauthorized) responses from the MASA.
5.4.1. MASA authentication of customer Registrar 5.4.1. MASA Authentication of Customer Registrar
Providing per-customer options requires that the customer's registrar Providing per-customer options requires the customer's registrar to
be uniquely identified. This can be done by any stateless method be uniquely identified. This can be done by any stateless method
that HTTPS supports such as with HTTP Basic or Digest authentication that HTTPS supports such as HTTP Basic or Digest authentication (that
(that is using a password), but the use of TLS Client Certificate is using a password), but the use of TLS Client Certificate
authentication is RECOMMENDED. authentication is RECOMMENDED.
Stateful methods involving API tokens, or HTTP Cookies, are not Stateful methods involving API tokens, or HTTP Cookies, are not
recommended. recommended.
It is expected that the setup and configuration of per-customer It is expected that the setup and configuration of per-customer
Client Certificates is done as part of a sales ordering process. Client Certificates is done as part of a sales ordering process.
The use of public PKI (i.e. WebPKI) End-Entity Certificates to The use of public PKI (i.e., WebPKI) end-entity certificates to
identify the Registrar is reasonable, and if done universally this identify the registrar is reasonable, and if done universally, this
would permit a MASA to identify a customers' Registrar simply by a would permit a MASA to identify a customer's registrar simply by a
FQDN. Fully Qualified Domain Name (FQDN).
The use of DANE records in DNSSEC signed zones would also permit use The use of DANE records in DNSSEC-signed zones would also permit use
of a FQDN to identify customer Registrars. of a FQDN to identify customer registrars.
A third (and simplest, but least flexible) mechanism would be for the A third (and simplest, but least flexible) mechanism would be for the
MASA to simply store the Registrar's certificate pinned in a MASA to simply store the registrar's certificate pinned in a
database. database.
A MASA without any supply chain integration can simply accept A MASA without any supply-chain integration can simply accept
Registrars without any authentication, or can accept them on a blind registrars without any authentication or on a blind TOFU basis as
Trust-on-First-Use basis as described in Section 7.4.2. described in Section 7.4.2.
This document does not make a specific recommendation on how the MASA This document does not make a specific recommendation on how the MASA
authenticates the Registrar as there are likely different tradeoffs authenticates the registrar as there are likely different tradeoffs
in different environments and product values. Even within the ANIMA in different environments and product values. Even within the ANIMA
ACP applicability, there is a significant difference between supply ACP applicability, there is a significant difference between supply-
chain logistics for $100 CPE devices and $100,000 core routers. chain logistics for $100 CPE devices and $100,000 core routers.
5.5. Registrar Requests Voucher from MASA 5.5. Registrar Requests Voucher from MASA
When a registrar receives a pledge voucher-request it in turn submits When a registrar receives a pledge voucher-request, it in turn
a registrar voucher-request to the MASA service via an HTTPS submits a registrar voucher-request to the MASA service via an HTTPS
interface ([RFC7231]). interface [RFC7231].
This is done with an HTTP POST using the operation path value of This is done with an HTTP POST using the operation path value of
"/.well-known/brski/requestvoucher". "/.well-known/brski/requestvoucher".
The voucher media type "application/voucher-cms+json" is defined in The voucher media type "application/voucher-cms+json" is defined in
[RFC8366] and is also used for the registrar voucher-request. It is [RFC8366] and is also used for the registrar voucher-request. It is
a JSON document that has been signed using a CMS structure. The a JSON document that has been signed using a CMS structure. The
registrar MUST sign the registrar voucher-request. registrar MUST sign the registrar voucher-request.
MASA implementations SHOULD anticipate future media ntypes but of MASA implementations SHOULD anticipate future media ntypes but, of
course will simply fail the request if those types are not yet known. course, will simply fail the request if those types are not yet
known.
The voucher-request CMS object includes some number of certificates The voucher-request CMS object includes some number of certificates
that are input to the MASA as it populates the 'pinned-domain-cert'. that are input to the MASA as it populates the pinned-domain-cert.
As the [RFC8366] is quite flexible in what may be put into the As [RFC8366] is quite flexible in what may be put into the pinned-
'pinned-domain-cert', the MASA needs some signal as to what domain-cert, the MASA needs some signal as to what certificate would
certificate would be effective to populate the field with: it may be effective to populate the field with: it may range from the end-
range from the End Entity (EE) Certificate that the Registrar uses, entity certificate that the registrar uses to the entire private
to the entire private Enterprise CA certificate. More specific Enterprise CA certificate. More-specific certificates result in a
certificates result in a tighter binding of the voucher to the tighter binding of the voucher to the domain, while less-specific
domain, while less specific certificates result in more flexibility certificates result in more flexibility in how the domain is
in how the domain is represented by certificates. represented by certificates.
A Registrar which is seeking a nonceless voucher for later offline A registrar that is seeking a nonceless voucher for later offline use
use benefits from a less specific certificate, as it permits the benefits from a less-specific certificate, as it permits the actual
actual keypair used by a future Registrar to be determined by the key pair used by a future registrar to be determined by the pinned
pinned certificate authority. CA.
In some cases, a less specific certificate, such a public WebPKI In some cases, a less-specific certificate, such as a public WebPKI
certificate authority, could be too open, and could permit any entity CA, could be too open and could permit any entity issued a
issued a certificate by that authority to assume ownership of a certificate by that authority to assume ownership of a device that
device that has a voucher pinned. Future work may provide a solution has a voucher pinned. Future work may provide a solution to pin both
to pin both a certificate and a name that would reduce such risk of a certificate and a name that would reduce such risk of malicious
malicious ownership assertions. ownership assertions.
The Registrar SHOULD request a voucher with the most specificity The registrar SHOULD request a voucher with the most specificity
consistent with the mode that it is operating in. In order to do consistent with the mode that it is operating in. In order to do
this, when the Registrar prepares the CMS structure for the signed this, when the registrar prepares the CMS structure for the signed
voucher-request, it SHOULD include only certificates which are part voucher-request, it SHOULD include only certificates that are a part
of the chain that it wishes the MASA to pin. This MAY be as small as of the chain that it wishes the MASA to pin. This MAY be as small as
only the End-Entity certificate (with id-kp-cmcRA set) that it uses only the end-entity certificate (with id-kp-cmcRA set) that it uses
as it's TLS Server Certificate, or it MAY be the entire chain, as its TLS server certificate, or it MAY be the entire chain,
including the Domain CA. including the domain CA.
The Registrar SHOULD include an [RFC7231] section 5.3.2 "Accept" The registrar SHOULD include an "Accept" header field (see [RFC7231],
header field indicating the response media types that are acceptable. Section 5.3.2) indicating the response media types that are
This list SHOULD be the entire list presented to the Registrar in the acceptable. This list SHOULD be the entire list presented to the
Pledge's original request (see Section 5.2) but MAY be a subset. The registrar in the pledge's original request (see Section 5.2), but it
MASA is expected to be flexible in what it accepts. MAY be a subset. The MASA is expected to be flexible in what it
accepts.
The registrar populates the voucher-request fields as follows: The registrar populates the voucher-request fields as follows:
created-on: The Registrars SHOULD populate this field with the created-on: The registrar SHOULD populate this field with the
current date and time when the Registrar formed this voucher current date and time when the voucher-request is formed. This
request. This field provides additional information to the MASA. field provides additional information to the MASA.
nonce: This value, if present, is copied from the pledge voucher- nonce: This value, if present, is copied from the pledge voucher-
request. The registrar voucher-request MAY omit the nonce as per request. The registrar voucher-request MAY omit the nonce as per
Section 3.1. Section 3.1.
serial-number: The serial number of the pledge the registrar would serial-number: The serial number of the pledge the registrar would
like a voucher for. The registrar determines this value by like a voucher for. The registrar determines this value by
parsing the authenticated pledge IDevID certificate. See parsing the authenticated pledge IDevID certificate; see
Section 2.3. The registrar MUST verify that the serial number Section 2.3. The registrar MUST verify that the serial-number
field it parsed matches the serial number field the pledge field it parsed matches the serial-number field the pledge
provided in its voucher-request. This provides a sanity check provided in its voucher-request. This provides a sanity check
useful for detecting error conditions and logging. The registrar useful for detecting error conditions and logging. The registrar
MUST NOT simply copy the serial number field from a pledge voucher MUST NOT simply copy the serial-number field from a pledge
request as that field is claimed but not certified. voucher-request as that field is claimed but not certified.
idevid-issuer: The Issuer value from the pledge IDevID certificate idevid-issuer: The Issuer value from the pledge IDevID certificate
is included to ensure unique interpretation of the serial-number. is included to ensure unique interpretation of the serial-number.
In the case of nonceless (offline) voucher-request, then an In the case of a nonceless (offline) voucher-request, an
appropriate value needs to be configured from the same out-of-band appropriate value needs to be configured from the same out-of-band
source as the serial-number. source as the serial-number.
prior-signed-voucher-request: The signed pledge voucher-request prior-signed-voucher-request: The signed pledge voucher-request
SHOULD be included in the registrar voucher-request. The entire SHOULD be included in the registrar voucher-request. The entire
CMS signed structure is to be included, base64 encoded for CMS-signed structure is to be included and base64 encoded for
transport in the JSON structure. transport in the JSON structure.
A nonceless registrar voucher-request MAY be submitted to the MASA. A nonceless registrar voucher-request MAY be submitted to the MASA.
Doing so allows the registrar to request a voucher when the pledge is Doing so allows the registrar to request a voucher when the pledge is
offline, or when the registrar anticipates not being able to connect offline, or when the registrar anticipates not being able to connect
to the MASA while the pledge is being deployed. Some use cases to the MASA while the pledge is being deployed. Some use cases
require the registrar to learn the appropriate IDevID SerialNumber require the registrar to learn the appropriate IDevID serialNumber
field and appropriate 'Accept header field' values from the physical field and appropriate "Accept" header field values from the physical
device labeling or from the sales channel (out-of-scope for this device labeling or from the sales channel (which is out of scope for
document). this document).
All other fields MAY be omitted in the registrar voucher-request. All other fields MAY be omitted in the registrar voucher-request.
The "proximity-registrar-cert" field MUST NOT be present in the The proximity-registrar-cert field MUST NOT be present in the
registrar voucher-request. registrar voucher-request.
Example JSON payloads of registrar voucher-requests are in See example JSON payloads of registrar voucher-requests in
Section 3.3 Examples 2 through 4. Section 3.3, Examples 2 through 4.
The MASA verifies that the registrar voucher-request is internally The MASA verifies that the registrar voucher-request is internally
consistent but does not necessarily authenticate the registrar consistent but does not necessarily authenticate the registrar
certificate since the registrar MAY be unknown to the MASA in certificate since the registrar MAY be unknown to the MASA in
advance. The MASA performs the actions and validation checks advance. The MASA performs the actions and validation checks
described in the following sub-sections before issuing a voucher. described in the following subsections before issuing a voucher.
5.5.1. MASA renewal of expired vouchers 5.5.1. MASA Renewal of Expired Vouchers
As described in [RFC8366] vouchers are normally short lived to avoid As described in [RFC8366], vouchers are normally short lived to avoid
revocation issues. If the request is for a previous (expired) revocation issues. If the request is for a previous (expired)
voucher using the same registrar (that is, a Registrar with the same voucher using the same registrar (that is, a registrar with the same
Domain CA) then the request for a renewed voucher SHOULD be domain CA), then the request for a renewed voucher SHOULD be
automatically authorized. The MASA has sufficient information to automatically authorized. The MASA has sufficient information to
determine this by examining the request, the registrar determine this by examining the request, the registrar
authentication, and the existing audit-log. The issuance of a authentication, and the existing audit-log. The issuance of a
renewed voucher is logged as detailed in Section 5.6. renewed voucher is logged as detailed in Section 5.6.
To inform the MASA that existing vouchers are not to be renewed one To inform the MASA that existing vouchers are not to be renewed, one
can update or revoke the registrar credentials used to authorize the can update or revoke the registrar credentials used to authorize the
request (see Section 5.5.4 and Section 5.5.3). More flexible methods request (see Sections 5.5.4 and 5.5.3). More flexible methods will
will likely involve sales channel integration and authorizations likely involve sales channel integration and authorizations (details
(details are out-of-scope of this document). are out of scope of this document).
5.5.2. MASA pinning of registrar 5.5.2. MASA Pinning of Registrar
A certificate chain is extracted from the Registrar's signed CMS A certificate chain is extracted from the registrar's signed CMS
container. This chain may be as short as a single End-Entity container. This chain may be as short as a single end-entity
Certificate, up to the entire registrar certificate chain, including certificate, up to the entire registrar certificate chain, including
the Domain CA certificate, as specified in Section 5.5. the domain CA certificate, as specified in Section 5.5.
If the domain's CA is unknown to the MASA, then it is to be If the domain's CA is unknown to the MASA, then it is considered a
considered a temporary trust anchor for the rest of the steps in this temporary trust anchor for the rest of the steps in this section.
section. The intention is not to authenticate the message as having The intention is not to authenticate the message as having come from
come from a fully validated origin, but to establish the consistency a fully validated origin but to establish the consistency of the
of the domain PKI. domain PKI.
The MASA MAY use the certificate farthest in the chain chain that it The MASA MAY use the certificate in the chain that is farthest from
received from the Registrar from the end-entity, as determined by the end-entity certificate of the registrar, as determined by MASA
MASA policy. A MASA MAY have a local policy that it only pins the policy. A MASA MAY have a local policy in which it only pins the
End-Entity certificate. This is consistent with [RFC8366]. Details end-entity certificate. This is consistent with [RFC8366]. Details
of the policy will typically depend upon the degree of Supply Chain of the policy will typically depend upon the degree of supply-chain
Integration, and the mechanism used by the Registrar to authenticate. integration and the mechanism used by the registrar to authenticate.
Such a policy would also determine how the MASA will respond to a Such a policy would also determine how the MASA will respond to a
request for a nonceless voucher. request for a nonceless voucher.
5.5.3. MASA checking of voucher request signature 5.5.3. MASA Check of the Voucher-Request Signature
As described in Section 5.5.2, the MASA has extracted Registrar's As described in Section 5.5.2, the MASA has extracted the registrar's
domain CA. This is used to validate the CMS signature ([RFC5652]) on domain CA. This is used to validate the CMS signature [RFC5652] on
the voucher-request. the voucher-request.
Normal PKIX revocation checking is assumed during voucher-request Normal PKIX revocation checking is assumed during voucher-request
signature validation. This CA certificate MAY have Certificate signature validation. This CA certificate MAY have Certificate
Revocation List distribution points, or Online Certificate Status Revocation List (CRL) distribution points or Online Certificate
Protocol (OCSP) information ([RFC6960]). If they are present, the Status Protocol (OCSP) information [RFC6960]. If they are present,
MASA MUST be able to reach the relevant servers belonging to the the MASA MUST be able to reach the relevant servers belonging to the
Registrar's domain CA to perform the revocation checks. registrar's domain CA to perform the revocation checks.
The use of OCSP Stapling is preferred. The use of OCSP Stapling is preferred.
5.5.4. MASA verification of domain registrar 5.5.4. MASA Verification of the Domain Registrar
The MASA MUST verify that the registrar voucher-request is signed by The MASA MUST verify that the registrar voucher-request is signed by
a registrar. This is confirmed by verifying that the id-kp-cmcRA a registrar. This is confirmed by verifying that the id-kp-cmcRA
extended key usage extension field (as detailed in EST RFC7030 extended key usage extension field (as detailed in EST [RFC7030],
section 3.6.1) exists in the certificate of the entity that signed Section 3.6.1) exists in the certificate of the entity that signed
the registrar voucher-request. This verification is only a the registrar voucher-request. This verification is only a
consistency check that the unauthenticated domain CA intended the consistency check to ensure that the unauthenticated domain CA
voucher-request signer to be a registrar. Performing this check intended the voucher-request signer to be a registrar. Performing
provides value to the domain PKI by assuring the domain administrator this check provides value to the domain PKI by assuring the domain
that the MASA service will only respect claims from authorized administrator that the MASA service will only respect claims from
Registration Authorities of the domain. authorized registration authorities of the domain.
Even when a domain CA is authenticated to the MASA, and there is Even when a domain CA is authenticated to the MASA, and there is
strong sales channel integration to understand who the legitimate strong sales channel integration to understand who the legitimate
owner is, the above id-kp-cmcRA check prevents arbitrary End-Entity owner is, the above id-kp-cmcRA check prevents arbitrary end-entity
certificates (such as an LDevID certificate) from having vouchers certificates (such as an LDevID certificate) from having vouchers
issued against them. issued against them.
Other cases of inappropriate voucher issuance are detected by Other cases of inappropriate voucher issuance are detected by
examination of the audit log. examination of the audit-log.
If a nonceless voucher-request is submitted the MASA MUST If a nonceless voucher-request is submitted, the MASA MUST
authenticate the registrar as described in either EST [RFC7030] authenticate the registrar either as described in EST (see Sections
section 3.2.3, section 3.3.2, or by validating the registrar's 3.2.3 and 3.3.2 of [RFC7030]) or by validating the registrar's
certificate used to sign the registrar voucher-request using a certificate used to sign the registrar voucher-request using a
configured trust anchor. Any of these methods reduce the risk of configured trust anchor. Any of these methods reduce the risk of
DDoS attacks and provide an authenticated identity as an input to DDoS attacks and provide an authenticated identity as an input to
sales channel integration and authorizations (details are out-of- sales channel integration and authorizations (details are out of
scope of this document). scope of this document).
In the nonced case, validation of the Registrar's identity (via TLS In the nonced case, validation of the registrar's identity (via TLS
Client Certificate or HTTP authentication) MAY be omitted if the Client Certificate or HTTP authentication) MAY be omitted if the MASA
device policy is to accept audit-only vouchers. knows that the device policy is to accept audit-only vouchers.
5.5.5. MASA verification of pledge prior-signed-voucher-request 5.5.5. MASA Verification of the Pledge 'prior-signed-voucher-request'
The MASA MAY verify that the registrar voucher-request includes the The MASA MAY verify that the registrar voucher-request includes the
'prior-signed-voucher-request' field. If so the prior-signed- prior-signed-voucher-request field. If so, the prior-signed-voucher-
voucher-request MUST include a 'proximity-registrar-cert' that is request MUST include a proximity-registrar-cert that is consistent
consistent with the certificate used to sign the registrar voucher- with the certificate used to sign the registrar voucher-request.
request. Additionally the voucher-request serial-number leaf MUST Additionally, the voucher-request serial-number leaf MUST match the
match the pledge serial-number that the MASA extracts from the pledge serial-number that the MASA extracts from the signing
signing certificate of the prior-signed-voucher-request. The certificate of the prior-signed-voucher-request. The consistency
consistency check described above is checking that the 'proximity- check described above entails checking that the proximity-registrar-
registrar-cert' SPKI fingerprint exists within the registrar voucher- cert Subject Public Key Info (SPKI) Fingerprint exists within the
request CMS signature's certificate chain. This is substantially the registrar voucher-request CMS signature's certificate chain. This is
same as the pin validation described in in [RFC7469] section 2.6, substantially the same as the pin validation described in [RFC7469],
paragraph three. Section 2.6.
If these checks succeed the MASA updates the voucher and audit-log If these checks succeed, the MASA updates the voucher and audit-log
assertion leafs with the "proximity" assertion, as defined by assertion leafs with the "proximity" assertion, as defined by
[RFC8366] section 5.3. [RFC8366], Section 5.3.
5.5.6. MASA nonce handling 5.5.6. MASA Nonce Handling
The MASA does not verify the nonce itself. If the registrar voucher- The MASA does not verify the nonce itself. If the registrar voucher-
request contains a nonce, and the prior-signed-voucher-request request contains a nonce, and the prior-signed-voucher-request
exists, then the MASA MUST verify that the nonce is consistent. exists, then the MASA MUST verify that the nonce is consistent.
(Recall from above that the voucher-request might not contain a (Recall from above that the voucher-request might not contain a
nonce, see Section 5.5 and Section 5.5.4). nonce; see Sections 5.5 and 5.5.4.)
The MASA populates the audit-log with the nonce that was verified. The MASA populates the audit-log with the nonce that was verified.
If a nonceless voucher is issued, then the audit-log is to be If a nonceless voucher is issued, then the audit-log is to be
populated with the JSON value "null". populated with the JSON value "null".
5.6. MASA and Registrar Voucher Response 5.6. MASA and Registrar Voucher Response
The MASA voucher response to the registrar is forwarded without The MASA voucher response to the registrar is forwarded without
changes to the pledge; therefore this section applies to both the changes to the pledge; therefore, this section applies to both the
MASA and the registrar. The HTTP signaling described applies to both MASA and the registrar. The HTTP signaling described applies to both
the MASA and registrar responses. the MASA and registrar responses.
When a voucher request arrives at the registrar, if it has a cached When a voucher-request arrives at the registrar, if it has a cached
response from the MASA for the corresponding registrar voucher- response from the MASA for the corresponding registrar voucher-
request, that cached response can be used according to local policy; request, that cached response can be used according to local policy;
otherwise the registrar constructs a new registrar voucher-request otherwise, the registrar constructs a new registrar voucher-request
and sends it to the MASA. and sends it to the MASA.
Registrar evaluation of the voucher itself is purely for transparency Registrar evaluation of the voucher itself is purely for transparency
and audit purposes to further inform log verification (see and audit purposes to further inform log verification (see
Section 5.8.3) and therefore a registrar could accept future voucher Section 5.8.3); therefore, a registrar could accept future voucher
formats that are opaque to the registrar. formats that are opaque to the registrar.
If the voucher-request is successful, the server (MASA responding to If the voucher-request is successful, the server (a MASA responding
registrar or registrar responding to pledge) response MUST contain an to a registrar or a registrar responding to a pledge) response MUST
HTTP 200 response code. The server MUST answer with a suitable 4xx contain an HTTP 200 response code. The server MUST answer with a
or 5xx HTTP [RFC7230] error code when a problem occurs. In this suitable 4xx or 5xx HTTP [RFC7230] error code when a problem occurs.
case, the response data from the MASA MUST be a plaintext human- In this case, the response data from the MASA MUST be a plain text
readable (UTF-8) error message containing explanatory information human-readable (UTF-8) error message containing explanatory
describing why the request was rejected. information describing why the request was rejected.
The registrar MAY respond with an HTTP 202 ("the request has been The registrar MAY respond with an HTTP 202 ("the request has been
accepted for processing, but the processing has not been completed") accepted for processing, but the processing has not been completed")
as described in EST [RFC7030] section 4.2.3 wherein the client "MUST as described in EST [RFC7030], Section 4.2.3, wherein the client
wait at least the specified 'Retry-After' time before repeating the "MUST wait at least the specified "retry-after" time before repeating
same request". (see [RFC7231] section 6.6.4) The pledge is the same request" (also see [RFC7231], Section 6.6.4). The pledge is
RECOMMENDED to provide local feedback (blinked LED etc) during this RECOMMENDED to provide local feedback (blinked LED, etc.) during this
wait cycle if mechanisms for this are available. To prevent an wait cycle if mechanisms for this are available. To prevent an
attacker registrar from significantly delaying bootstrapping the attacker registrar from significantly delaying bootstrapping, the
pledge MUST limit the 'Retry-After' time to 60 seconds. Ideally the pledge MUST limit the Retry-After time to 60 seconds. Ideally, the
pledge would keep track of the appropriate Retry-After header field pledge would keep track of the appropriate Retry-After header field
values for any number of outstanding registrars but this would values for any number of outstanding registrars, but this would
involve a state table on the pledge. Instead the pledge MAY ignore involve a state table on the pledge. Instead, the pledge MAY ignore
the exact Retry-After value in favor of a single hard coded value (a the exact Retry-After value in favor of a single hard-coded value (a
registrar that is unable to complete the transaction after the first registrar that is unable to complete the transaction after the first
60 seconds has another chance a minute later). A pledge SHOULD only 60 seconds has another chance a minute later). A pledge SHOULD be
maintain a 202 retry-state for up to 4 days, which is longer than a willing to maintain a 202 retry-state for up to 4 days, which is
long weekend, after which time the enrollment attempt fails and the longer than a long weekend, after which time the enrollment attempt
pledge returns to discovery state. fails, and the pledge returns to Discovery state. This allows time
for an alert to get from the registrar to a human operator who can
make a decision as to whether or not to proceed with the enrollment.
A pledge that retries a request after receiving a 202 message MUST A pledge that retries a request after receiving a 202 message MUST
resend the same voucher-request. It MUST NOT sign a new voucher- resend the same voucher-request. It MUST NOT sign a new voucher-
request each time, and in particular, it MUST NOT change the nonce request each time, and in particular, it MUST NOT change the nonce
value. value.
In order to avoid infinite redirect loops, which a malicious In order to avoid infinite redirect loops, which a malicious
registrar might do in order to keep the pledge from discovering the registrar might do in order to keep the pledge from discovering the
correct registrar, the pledge MUST NOT follow more than one correct registrar, the pledge MUST NOT follow more than one
redirection (3xx code) to another web origin. EST supports redirection (3xx code) to another web origin. EST supports
redirection but requires user input; this change allows the pledge to redirection but requires user input; this change allows the pledge to
follow a single redirection without a user interaction. follow a single redirection without a user interaction.
A 403 (Forbidden) response is appropriate if the voucher-request is A 403 (Forbidden) response is appropriate if the voucher-request is
not signed correctly, stale, or if the pledge has another outstanding not signed correctly or is stale or if the pledge has another
voucher that cannot be overridden. outstanding voucher that cannot be overridden.
A 404 (Not Found) response is appropriate when the request is for a A 404 (Not Found) response is appropriate when the request is for a
device that is not known to the MASA. device that is not known to the MASA.
A 406 (Not Acceptable) response is appropriate if a voucher of the A 406 (Not Acceptable) response is appropriate if a voucher of the
desired type or using the desired algorithms (as indicated by the desired type or that uses the desired algorithms (as indicated by the
Accept: header fields, and algorithms used in the signature) cannot "Accept" header fields and algorithms used in the signature) cannot
be issued such as because the MASA knows the pledge cannot process be issued as such because the MASA knows the pledge cannot process
that type. The registrar SHOULD use this response if it determines that type. The registrar SHOULD use this response if it determines
the pledge is unacceptable due to inventory control, MASA audit-logs, the pledge is unacceptable due to inventory control, MASA audit-logs,
or any other reason. or any other reason.
A 415 (Unsupported Media Type) response is appropriate for a request A 415 (Unsupported Media Type) response is appropriate for a request
that has a voucher-request or Accept: value that is not understood. that has a voucher-request or "Accept" value that is not understood.
The voucher response format is as indicated in the submitted Accept The voucher response format is as indicated in the submitted "Accept"
header fields or based on the MASA's prior understanding of proper header fields or based on the MASA's prior understanding of proper
format for this Pledge. Only the [RFC8366] "application/voucher- format for this pledge. Only the "application/voucher-cms+json"
cms+json" media type is defined at this time. The syntactic details media type [RFC8366] is defined at this time. The syntactic details
of vouchers are described in detail in [RFC8366]. Figure 14 shows a of vouchers are described in detail in [RFC8366]. Figure 14 shows a
sample of the contents of a voucher. sample of the contents of a voucher.
{ {
"ietf-voucher:voucher": { "ietf-voucher:voucher": {
"nonce": "62a2e7693d82fcda2624de58fb6722e5", "nonce": "62a2e7693d82fcda2624de58fb6722e5",
"assertion": "logged", "assertion": "logged",
"pinned-domain-cert": "base64encodedvalue==", "pinned-domain-cert": "base64encodedvalue==",
"serial-number": "JADA123456789" "serial-number": "JADA123456789"
} }
} }
Figure 14: An example voucher Figure 14: An Example Voucher
The MASA populates the voucher fields as follows: The MASA populates the voucher fields as follows:
nonce: The nonce from the pledge if available. See Section 5.5.6. nonce: The nonce from the pledge if available. See Section 5.5.6.
assertion: The method used to verify the relationship between pledge assertion: The method used to verify the relationship between the
and registrar. See Section 5.5.5. pledge and registrar. See Section 5.5.5.
pinned-domain-cert: A certificate. See Section 5.5.2. This figure pinned-domain-cert: A certificate; see Section 5.5.2. This figure
is illustrative, for an example, see Appendix C.2 where an End is illustrative; for an example, see Appendix C.2 where an end-
Entity certificate is used. entity certificate is used.
serial-number: The serial-number as provided in the voucher-request. serial-number: The serial-number as provided in the voucher-request.
Also see Section 5.5.5. Also see Section 5.5.5.
domain-cert-revocation-checks: Set as appropriate for the pledge's domain-cert-revocation-checks: Set as appropriate for the pledge's
capabilities and as documented in [RFC8366]. The MASA MAY set capabilities and as documented in [RFC8366]. The MASA MAY set
this field to 'false' since setting it to 'true' would require this field to "false" since setting it to "true" would require
that revocation information be available to the pledge and this that revocation information be available to the pledge, and this
document does not make normative requirements for [RFC6961] or document does not make normative requirements for [RFC6961],
equivalent integrations. Section 4.4.2.1 of [RFC8446], or equivalent integrations.
expires-on: This is set for nonceless vouchers. The MASA ensures expires-on: This is set for nonceless vouchers. The MASA ensures
the voucher lifetime is consistent with any revocation or pinned- the voucher lifetime is consistent with any revocation or pinned-
domain-cert consistency checks the pledge might perform. See domain-cert consistency checks the pledge might perform. See
section Section 2.6.1. There are three times to consider: (a) a Section 2.6.1. There are three times to consider: (a) a
configured voucher lifetime in the MASA, (b) the expiry time for configured voucher lifetime in the MASA, (b) the expiry time for
the registrar's certificate, (c) any certificate revocation the registrar's certificate, and (c) any CRL lifetime. The
information (CRL) lifetime. The expires-on field SHOULD be before expires-on field SHOULD be before the earliest of these three
the earliest of these three values. Typically (b) will be some values. Typically, (b) will be some significant time in the
significant time in the future, but (c) will typically be short future, but (c) will typically be short (on the order of a week or
(on the order of a week or less). The RECOMMENDED period for (a) less). The RECOMMENDED period for (a) is on the order of 20
is on the order of 20 minutes, so it will typically determine the minutes, so it will typically determine the life span of the
lifespan of the resulting voucher. 20 minutes is sufficient time resulting voucher. 20 minutes is sufficient time to reach the
to reach the post-provisional state in the pledge, at which point post-provisional state in the pledge, at which point there is an
there is an established trust relationship between pledge and established trust relationship between the pledge and registrar.
registrar. The subsequent operations can take as long as required The subsequent operations can take as long as required from that
from that point onwards. The lifetime of the voucher has no point onwards. The lifetime of the voucher has no impact on the
impact on the lifespan of the ownership relationship. life span of the ownership relationship.
Whenever a voucher is issued the MASA MUST update the audit-log Whenever a voucher is issued, the MASA MUST update the audit-log
sufficiently to generate the response as described in Section 5.8.1. sufficiently to generate the response as described in Section 5.8.1.
The internal state requirements to maintain the audit-log are out-of- The internal state requirements to maintain the audit-log are out of
scope. scope.
5.6.1. Pledge voucher verification 5.6.1. Pledge Voucher Verification
The pledge MUST verify the voucher signature using the manufacturer- The pledge MUST verify the voucher signature using the manufacturer-
installed trust anchor(s) associated with the manufacturer's MASA installed trust anchor(s) associated with the manufacturer's MASA
(this is likely included in the pledge's firmware). Management of (this is likely included in the pledge's firmware). Management of
the manufacturer-installed trust anchor(s) is out-of-scope of this the manufacturer-installed trust anchor(s) is out of scope of this
document; this protocol does not update these trust anchor(s). document; this protocol does not update this trust anchor(s).
The pledge MUST verify the serial-number field of the signed voucher The pledge MUST verify that the serial-number field of the signed
matches the pledge's own serial-number. voucher matches the pledge's own serial-number.
The pledge MUST verify the nonce information in the voucher. If The pledge MUST verify the nonce information in the voucher. If
present, the nonce in the voucher must match the nonce the pledge present, the nonce in the voucher must match the nonce the pledge
submitted to the registrar; vouchers with no nonce can also be submitted to the registrar; vouchers with no nonce can also be
accepted (according to local policy, see Section 7.2) accepted (according to local policy; see Section 7.2).
The pledge MUST be prepared to parse and fail gracefully from a The pledge MUST be prepared to parse and fail gracefully from a
voucher response that does not contain a 'pinned-domain-cert' field. voucher response that does not contain a pinned-domain-cert field.
Such a thing indicates a failure to enroll in this domain, and the Such a thing indicates a failure to enroll in this domain, and the
pledge MUST attempt joining with other available Join Proxy. pledge MUST attempt joining with other available Join Proxies.
The pledge MUST be prepared to ignore additional fields that it does The pledge MUST be prepared to ignore additional fields that it does
not recognize. not recognize.
5.6.2. Pledge authentication of provisional TLS connection 5.6.2. Pledge Authentication of Provisional TLS Connection
Following the process described in [RFC8366], the pledge should Following the process described in [RFC8366], the pledge should
consider the public key from the pinned-domain-cert as the sole consider the public key from the pinned-domain-cert as the sole
temporary trust anchor. temporary trust anchor.
The pledge then evaluates the TLS Server Certificate chain that it The pledge then evaluates the TLS server certificate chain that it
received when the TLS connection was formed using this trust anchor. received when the TLS connection was formed using this trust anchor.
It is possible that the pinned-domain-cert matches the End-Entity It is possible that the public key in the pinned-domain-cert directly
Certificate provided in the TLS Server. matches the public key in the end-entity certificate provided by the
TLS server.
If a registrar's credentials cannot be verified using the pinned- If a registrar's credentials cannot be verified using the pinned-
domain-cert trust anchor from the voucher then the TLS connection is domain-cert trust anchor from the voucher, then the TLS connection is
immediately discarded and the pledge abandons attempts to bootstrap discarded, and the pledge abandons attempts to bootstrap with this
with this discovered registrar. The pledge SHOULD send voucher discovered registrar. The pledge SHOULD send voucher status
status telemetry (described below) before closing the TLS connection. telemetry (described below) before closing the TLS connection. The
The pledge MUST attempt to enroll using any other proxies it has pledge MUST attempt to enroll using any other proxies it has found.
found. It SHOULD return to the same proxy again after unsuccessful It SHOULD return to the same proxy again after unsuccessful attempts
attempts with other proxies. Attempts should be made repeated at with other proxies. Attempts should be made at repeated intervals
intervals according to the backoff timer described earlier. Attempts according to the back-off timer described earlier. Attempts SHOULD
SHOULD be repeated as failure may be the result of a temporary be repeated as failure may be the result of a temporary inconsistency
inconsistency (an inconsistently rolled registrar key, or some other (an inconsistently rolled registrar key, or some other
mis-configuration). The inconsistency could also be the result an misconfiguration). The inconsistency could also be the result of an
active MITM attack on the EST connection. active MITM attack on the EST connection.
The registrar MUST use a certificate that chains to the pinned- The registrar MUST use a certificate that chains to the pinned-
domain-cert as its TLS server certificate. domain-cert as its TLS server certificate.
The pledge's PKIX path validation of a registrar certificate's The pledge's PKIX path validation of a registrar certificate's
validity period information is as described in Section 2.6.1. Once validity period information is as described in Section 2.6.1. Once
the PKIX path validation is successful the TLS connection is no the PKIX path validation is successful, the TLS connection is no
longer provisional. longer provisional.
The pinned-domain-cert MAY be installed as a trust anchor for future The pinned-domain-cert MAY be installed as a trust anchor for future
operations such as enrollment (e.g. [RFC7030] as recommended) or operations such as enrollment (e.g., as recommended per [RFC7030]) or
trust anchor management or raw protocols that do not need full PKI trust anchor management or raw protocols that do not need full PKI-
based key management. It can be used to authenticate any dynamically based key management. It can be used to authenticate any dynamically
discovered EST server that contain the id-kp-cmcRA extended key usage discovered EST server that contains the id-kp-cmcRA extended key
extension as detailed in EST RFC7030 section 3.6.1; but to reduce usage extension as detailed in EST (see [RFC7030], Section 3.6.1);
system complexity the pledge SHOULD avoid additional discovery but to reduce system complexity, the pledge SHOULD avoid additional
operations. Instead the pledge SHOULD communicate directly with the discovery operations. Instead, the pledge SHOULD communicate
registrar as the EST server. The 'pinned-domain-cert' is not a directly with the registrar as the EST server. The pinned-domain-
complete distribution of the [RFC7030] section 4.1.3 CA Certificate cert is not a complete distribution of the CA certificate response,
Response, which is an additional justification for the recommendation as described in [RFC7030], Section 4.1.3, which is an additional
to proceed with EST key management operations. Once a full CA justification for the recommendation to proceed with EST key
Certificate Response is obtained it is more authoritative for the management operations. Once a full CA certificate response is
domain than the limited 'pinned-domain-cert' response. obtained, it is more authoritative for the domain than the limited
pinned-domain-cert response.
5.7. Pledge BRSKI Status Telemetry 5.7. Pledge BRSKI Status Telemetry
The domain is expected to provide indications to the system The domain is expected to provide indications to the system
administrators concerning device lifecycle status. To facilitate administrators concerning device life-cycle status. To facilitate
this it needs telemetry information concerning the device's status. this, it needs telemetry information concerning the device's status.
The pledge MUST indicate its pledge status regarding the voucher. It The pledge MUST indicate its pledge status regarding the voucher. It
does this by sending a status message to the Registrar. does this by sending a status message to the registrar.
The posted data media type: application/json The posted data media type: application/json
The client sends an HTTP POST to the server at the URI ".well- The client sends an HTTP POST to the server at the URI ".well-
known/brski/voucher_status". known/brski/voucher_status".
The format and semantics described below are for version 1. A The format and semantics described below are for version 1. A
version field is included to permit significant changes to this version field is included to permit significant changes to this
feedback in the future. A Registrar that receives a status message feedback in the future. A registrar that receives a status message
with a version larger than it knows about SHOULD log the contents and with a version larger than it knows about SHOULD log the contents and
alert a human. alert a human.
The Status field indicates if the voucher was acceptable. Boolean The status field indicates if the voucher was acceptable. Boolean
values are acceptable, where "true" indicates the voucher was values are acceptable, where "true" indicates the voucher was
acceptable. acceptable.
If the voucher was not acceptable the Reason string indicates why. If the voucher was not acceptable, the Reason string indicates why.
In the failure case this message may be sent to an unauthenticated, In a failure case, this message may be sent to an unauthenticated,
potentially malicious registrar and therefore the Reason string potentially malicious registrar; therefore, the Reason string SHOULD
SHOULD NOT provide information beneficial to an attacker. The NOT provide information beneficial to an attacker. The operational
operational benefit of this telemetry information is balanced against benefit of this telemetry information is balanced against the
the operational costs of not recording that an voucher was ignored by operational costs of not recording that a voucher was ignored by a
a client the registrar expected to continue joining the domain. client that the registrar expected was going to continue joining the
domain.
The reason-context attribute is an arbitrary JSON object (literal The reason-context attribute is an arbitrary JSON object (literal
value or hash of values) which provides additional information value or hash of values) that provides additional information
specific to this pledge. The contents of this field are not subject specific to this pledge. The contents of this field are not subject
to standardization. to standardization.
The version and status fields MUST be present. The Reason field The version and status fields MUST be present. The Reason field
SHOULD be present whenever the status field is false. The Reason- SHOULD be present whenever the status field is false. The Reason-
Context field is optional. In the case of a SUCCESS the Reason Context field is optional. In the case of a SUCCESS, the Reason
string MAY be omitted. string MAY be omitted.
The keys to this JSON object are case-sensitive and MUST be The keys to this JSON object are case sensitive and MUST be
lowercase. Figure 16 shows an example JSON. lowercase. Figure 16 shows an example JSON.
<CODE BEGINS> file "voucherstatus.cddl" <CODE BEGINS> file "voucherstatus.cddl"
voucherstatus-post = { voucherstatus-post = {
"version": uint, "version": uint,
"status": bool, "status": bool,
? "reason": text, ? "reason": text,
? "reason-context" : { $$arbitrary-map } ? "reason-context" : { $$arbitrary-map }
} }
} }
<CODE ENDS> <CODE ENDS>
Figure 15: CDDL for voucher status POST Figure 15: CDDL for Voucher Status POST
{ {
"version": 1, "version": 1,
"status":false, "status":false,
"reason":"Informative human readable message", "reason":"Informative human-readable message",
"reason-context": { "additional" : "JSON" } "reason-context": { "additional" : "JSON" }
} }
Figure 16: Example Status Telemetry Figure 16: Example Status Telemetry
The server SHOULD respond with an HTTP 200 but MAY simply fail with The server SHOULD respond with an HTTP 200 but MAY simply fail with
an HTTP 404 error. The client ignores any response. Within the an HTTP 404 error. The client ignores any response. The server
server logs the server SHOULD capture this telemetry information. SHOULD capture this telemetry information within the server logs.
Additional standard JSON fields in this POST MAY be added, see Additional standard JSON fields in this POST MAY be added; see
Section 8.5. A server that sees unknown fields should log them, but Section 8.5. A server that sees unknown fields should log them, but
otherwise ignore them. otherwise ignore them.
5.8. Registrar audit-log request 5.8. Registrar Audit-Log Request
After receiving the pledge status telemetry Section 5.7, the After receiving the pledge status telemetry (see Section 5.7), the
registrar SHOULD request the MASA audit-log from the MASA service. registrar SHOULD request the MASA audit-log from the MASA service.
This is done with an HTTP POST using the operation path value of This is done with an HTTP POST using the operation path value of
"/.well-known/brski/requestauditlog". "/.well-known/brski/requestauditlog".
The registrar SHOULD HTTP POST the same registrar voucher-request as The registrar SHOULD HTTP POST the same registrar voucher-request as
it did when requesting a voucher (using the same Content-Type). It it did when requesting a voucher (using the same Content-Type). It
is posted to the /requestauditlog URI instead. The "idevid-issuer" is posted to the /requestauditlog URI instead. The idevid-issuer and
and "serial-number" informs the MASA which log is requested so the serial-number informs the MASA which log is requested, so the
appropriate log can be prepared for the response. Using the same appropriate log can be prepared for the response. Using the same
media type and message minimizes cryptographic and message operations media type and message minimizes cryptographic and message
although it results in additional network traffic. The relying MASA operations, although it results in additional network traffic. The
implementation MAY leverage internal state to associate this request relying MASA implementation MAY leverage internal state to associate
with the original, and by now already validated, voucher-request so this request with the original, and by now already validated,
as to avoid an extra crypto validation. voucher-request so as to avoid an extra crypto validation.
A registrar MAY request logs at future times. If the registrar A registrar MAY request logs at future times. If the registrar
generates a new request then the MASA is forced to perform the generates a new request, then the MASA is forced to perform the
additional cryptographic operations to verify the new request. additional cryptographic operations to verify the new request.
A MASA that receives a request for a device that does not exist, or A MASA that receives a request for a device that does not exist, or
for which the requesting owner was never an owner returns an HTTP 404 for which the requesting owner was never an owner, returns an HTTP
("Not found") code. 404 ("Not found") code.
It is reasonable for a Registrar, that the MASA does not believe to It is reasonable for a registrar, that the MASA does not believe to
be the current owner, to request the audit-log. There are probably be the current owner, to request the audit-log. There are probably
reasons for this which are hard to predict in advance. For instance, reasons for this, which are hard to predict in advance. For
such a registrar may not be aware that the device has been resold; it instance, such a registrar may not be aware that the device has been
may be that the device has been resold inappropriately, and this is resold; it may be that the device has been resold inappropriately,
how the original owner will learn of the occurance. It is also and this is how the original owner will learn of the occurrence. It
possible that the device legitimately spends time in two different is also possible that the device legitimately spends time in two
networks. different networks.
Rather than returning the audit-log as a response to the POST (with a Rather than returning the audit-log as a response to the POST (with a
return code 200), the MASA MAY instead return a 201 ("Created") return code 200), the MASA MAY instead return a 201 ("Created")
response ([RFC7231] sections 6.3.2 and 7.1), with the URL to the response ([RFC7231], Sections 6.3.2 and 7.1), with the URL to the
prepared (and idempotent, therefore cachable) audit response in the prepared (and idempotent, therefore cachable) audit response in the
Location: header field. "Location" header field.
In order to avoid enumeration of device audit-logs, MASA that return In order to avoid enumeration of device audit-logs, a MASA that
URLs SHOULD take care to make the returned URL unguessable. returns URLs SHOULD take care to make the returned URL unguessable.
[W3C.WD-capability-urls-20140218] provides very good additional [W3C.capability-urls] provides very good additional guidance. For
guidance. For instance, rather than returning URLs containing a instance, rather than returning URLs containing a database number
database number such as https://example.com/auditlog/1234 or the EUI such as https://example.com/auditlog/1234 or the Extended Unique
of the device such https://example.com/auditlog/10-00-00-11-22-33, Identifier (EUI) of the device such https://example.com/
the MASA SHOULD return a randomly generated value (a "slug" in web auditlog/10-00-00-11-22-33, the MASA SHOULD return a randomly
parlance). The value is used to find the relevant database entry. generated value (a "slug" in web parlance). The value is used to
find the relevant database entry.
A MASA that returns a code 200 MAY also include a Location: header A MASA that returns a code 200 MAY also include a "Location" header
for future reference by the registrar. for future reference by the registrar.
5.8.1. MASA audit log response 5.8.1. MASA Audit-Log Response
A log data file is returned consisting of all log entries associated A log data file is returned consisting of all log entries associated
with the device selected by the IDevID presented in the request. The with the device selected by the IDevID presented in the request. The
audit log may be abridged by removal of old or repeated values as audit-log may be abridged by removal of old or repeated values as
explained below. The returned data is in JSON format ([RFC8259]), explained below. The returned data is in JSON format [RFC8259], and
and the Content-Type SHOULD be "application/json". the Content-Type SHOULD be "application/json".
The following CDDL ([RFC8610]) explains the structure of the JSON The following CDDL [RFC8610] explains the structure of the JSON
format audit-log response: format audit-log response:
<CODE BEGINS> file "auditlog.cddl" <CODE BEGINS> file "auditlog.cddl"
audit-log-response = { audit-log-response = {
"version": uint, "version": uint,
"events": [ + event ] "events": [ + event ]
"truncation": { "truncation": {
? "nonced duplicates": uint, ? "nonced duplicates": uint,
? "nonceless duplicates": uint, ? "nonceless duplicates": uint,
? "arbitrary": uint, ? "arbitrary": uint,
skipping to change at page 58, line 36 skipping to change at line 2652
event = { event = {
"date": text, "date": text,
"domainID": text, "domainID": text,
"nonce": text / null, "nonce": text / null,
"assertion": "verified" / "logged" / "proximity", "assertion": "verified" / "logged" / "proximity",
? "truncated": uint, ? "truncated": uint,
} }
<CODE ENDS> <CODE ENDS>
Figure 17: CDDL for audit-log response Figure 17: CDDL for Audit-Log Response
An example: An example:
{ {
"version":"1", "version":"1",
"events":[ "events":[
{ {
"date":"2019-05-15T17:25:55.644-04:00", "date":"2019-05-15T17:25:55.644-04:00",
"domainID":"BduJhdHPpfhQLyponf48JzXSGZ8=", "domainID":"BduJhdHPpfhQLyponf48JzXSGZ8=",
"nonce":"VOUFT-WwrEv0NuAQEHoV7Q", "nonce":"VOUFT-WwrEv0NuAQEHoV7Q",
skipping to change at page 59, line 29 skipping to change at line 2680
"assertion":"proximity" "assertion":"proximity"
} }
], ],
"truncation": { "truncation": {
"nonced duplicates": "0", "nonced duplicates": "0",
"nonceless duplicates": "1", "nonceless duplicates": "1",
"arbitrary": "2" "arbitrary": "2"
} }
} }
Figure 18: Example of audit-log response Figure 18: Example of an Audit-Log Response
The domainID is a binary SubjectKeyIdentifier value calculated The domainID is a binary SubjectKeyIdentifier value calculated
according to Section 5.8.2. It is encoded once in base64 in order to according to Section 5.8.2. It is encoded once in base64 in order to
be transported in this JSON container. be transported in this JSON container.
The date is in [RFC3339] format, which is consistent with typical The date is formatted per [RFC3339], which is consistent with typical
JavaScript usage of JSON. JavaScript usage of JSON.
The truncation structure MAY be omitted if all values are zero. Any The truncation structure MAY be omitted if all values are zero. Any
counter missing from the truncation structure is the be assumed to be counter missing from the truncation structure is assumed to be zero.
zero.
The nonce is a string, as provided in the voucher-request, and used The nonce is a string, as provided in the voucher-request, and is
in the voucher. If no nonce was placed in the resulting voucher, used in the voucher. If no nonce was placed in the resulting
then a value of null SHOULD be used in preference to omitting the voucher, then a value of null SHOULD be used in preference to
entry. While the nonce is often created as a base64 encoded random omitting the entry. While the nonce is often created as a
series of bytes, this should not be assumed. base64-encoded random series of bytes, this should not be assumed.
Distribution of a large log is less than ideal. This structure can Distribution of a large log is less than ideal. This structure can
be optimized as follows: Nonced or Nonceless entries for the same be optimized as follows: nonced or nonceless entries for the same
domainID MAY be abridged from the log leaving only the single most domainID MAY be abridged from the log leaving only the single most
recent nonced or nonceless entry for that domainID. In the case of recent nonced or nonceless entry for that domainID. In the case of
truncation the 'event' truncation value SHOULD contain a count of the truncation, the "event" truncation value SHOULD contain a count of
number of events for this domainID that were omitted. The log SHOULD the number of events for this domainID that were omitted. The log
NOT be further reduced but there could exist operational situation SHOULD NOT be further reduced, but an operational situation could
where maintaining the full log is not possible. In such situations exist where maintaining the full log is not possible. In such
the log MAY be arbitrarily abridged for length, with the number of situations, the log MAY be arbitrarily abridged for length, with the
removed entries indicated as 'arbitrary'. number of removed entries indicated as "arbitrary".
If the truncation count exceeds 1024 then the MASA MAY use this value If the truncation count exceeds 1024, then the MASA MAY use this
without further incrementing it. value without further incrementing it.
A log where duplicate entries for the same domain have been omitted A log where duplicate entries for the same domain have been omitted
("nonced duplicates" and/or "nonceless duplicates) could still be ("nonced duplicates" and/or "nonceless duplicates") could still be
acceptable for informed decisions. A log that has had "arbitrary" acceptable for informed decisions. A log that has had "arbitrary"
truncations is less acceptable but manufacturer transparency is truncations is less acceptable, but manufacturer transparency is
better than hidden truncations. better than hidden truncations.
A registrar that sees a version value greater than 1 indicates an A registrar that sees a version value greater than 1 indicates an
audit log format that has been enhanced with additional information. audit-log format that has been enhanced with additional information.
No information will be removed in future versions; should an No information will be removed in future versions; should an
incompatible change be desired in the future, then a new HTTP end incompatible change be desired in the future, then a new HTTP
point will be used. endpoint will be used.
This document specifies a simple log format as provided by the MASA This document specifies a simple log format as provided by the MASA
service to the registrar. This format could be improved by service to the registrar. This format could be improved by
distributed consensus technologies that integrate vouchers with distributed consensus technologies that integrate vouchers with
technologies such as block-chain or hash trees or optimized logging technologies such as block-chain or hash trees or optimized logging
approaches. Doing so is out of the scope of this document but is an approaches. Doing so is out of the scope of this document but is an
anticipated improvement for future work. As such, the registrar anticipated improvement for future work. As such, the registrar
SHOULD anticipate new kinds of responses, and SHOULD provide operator SHOULD anticipate new kinds of responses and SHOULD provide operator
controls to indicate how to process unknown responses. controls to indicate how to process unknown responses.
5.8.2. Calculation of domainID 5.8.2. Calculation of domainID
The domainID is a binary value (a BIT STRING) that uniquely The domainID is a binary value (a BIT STRING) that uniquely
identifies a Registrar by the "pinned-domain-cert". identifies a registrar by the pinned-domain-cert.
If the "pinned-domain-cert" certificate includes the If the pinned-domain-cert certificate includes the
SubjectKeyIdentifier (Section 4.2.1.2 [RFC5280]), then it is to be SubjectKeyIdentifier ([RFC5280], Section 4.2.1.2), then it is used as
used as the domainID. If not, the SPKI Fingerprint as described in the domainID. If not, the SPKI Fingerprint as described in
[RFC7469] section 2.4 is to be used. This value needs to be [RFC7469], Section 2.4 is used. This value needs to be calculated by
calculated by both MASA (to populate the audit-log), and by the both the MASA (to populate the audit-log) and the registrar (to
Registrar (to recognize itself in the audit log). recognize itself in the audit-log).
[RFC5280] section 4.2.1.2 does not mandate that the [RFC5280], Section 4.2.1.2 does not mandate that the
SubjectKeyIdentifier extension be present in non-CA certificates. It SubjectKeyIdentifier extension be present in non-CA certificates. It
is RECOMMENDED that Registrar certificates (even if self-signed), is RECOMMENDED that registrar certificates (even if self-signed)
always include the SubjectKeyIdentifier to be used as a domainID. always include the SubjectKeyIdentifier to be used as a domainID.
The domainID is determined from the certificate chain associated with The domainID is determined from the certificate chain associated with
the pinned-domain-cert and is used to update the audit-log. the pinned-domain-cert and is used to update the audit-log.
5.8.3. Registrar audit log verification 5.8.3. Registrar Audit-Log Verification
Each time the Manufacturer Authorized Signing Authority (MASA) issues Each time the MASA issues a voucher, it appends details of the
a voucher, it appends details of the assignment to an internal audit assignment to an internal audit-log for that device. The internal
log for that device. The internal audit log is processed when audit-log is processed when responding to requests for details as
responding to requests for details as described in Section 5.8. The described in Section 5.8. The contents of the audit-log can express
contents of the audit log can express a variety of trust levels, and a variety of trust levels, and this section explains what kind of
this section explains what kind of trust a registrar can derive from trust a registrar can derive from the entries.
the entries.
While the audit log provides a list of vouchers that were issued by While the audit-log provides a list of vouchers that were issued by
the MASA, the vouchers are issued in response to voucher-requests, the MASA, the vouchers are issued in response to voucher-requests,
and it is the contents of the voucher-requests which determines how and it is the content of the voucher-requests that determines how
meaningful the audit log entries are. meaningful the audit-log entries are.
A registrar SHOULD use the log information to make an informed A registrar SHOULD use the log information to make an informed
decision regarding the continued bootstrapping of the pledge. The decision regarding the continued bootstrapping of the pledge. The
exact policy is out of scope of this document as it depends on the exact policy is out of scope of this document as it depends on the
security requirements within the registrar domain. Equipment that is security requirements within the registrar domain. Equipment that is
purchased pre-owned can be expected to have an extensive history. purchased preowned can be expected to have an extensive history. The
The following discussion is provided to help explain the value of following discussion is provided to help explain the value of each
each log element: log element:
date: The date field provides the registrar an opportunity to divide date: The date field provides the registrar an opportunity to divide
the log around known events such as the purchase date. Depending the log around known events such as the purchase date. Depending
on context known to the registrar or administrator events before/ on the context known to the registrar or administrator, events
after certain dates can have different levels of importance. For before/after certain dates can have different levels of
example for equipment that is expected to be new, and thus have no importance. For example, for equipment that is expected to be
history, it would be a surprise to find prior entries. new, and thus has no history, it would be a surprise to find prior
entries.
domainID: If the log includes an unexpected domainID then the pledge domainID: If the log includes an unexpected domainID, then the
could have imprinted on an unexpected domain. The registrar can pledge could have imprinted on an unexpected domain. The
be expected to use a variety of techniques to define "unexpected" registrar can be expected to use a variety of techniques to define
ranging from white lists of prior domains to anomaly detection "unexpected" ranging from acceptlists of prior domains to anomaly
(e.g. "this device was previously bound to a different domain than detection (e.g., "this device was previously bound to a different
any other device deployed"). Log entries can also be compared domain than any other device deployed"). Log entries can also be
against local history logs in search of discrepancies (e.g. "this compared against local history logs in search of discrepancies
device was re-deployed some number of times internally but the (e.g., "this device was re-deployed some number of times
external audit log shows additional re-deployments our internal internally, but the external audit-log shows additional re-
logs are unaware of"). deployments our internal logs are unaware of").
nonce: Nonceless entries mean the logged domainID could nonce: Nonceless entries mean the logged domainID could
theoretically trigger a reset of the pledge and then take over theoretically trigger a reset of the pledge and then take over
management by using the existing nonceless voucher. management by using the existing nonceless voucher.
assertion: The assertion leaf in the voucher and audit log indicates assertion: The assertion leaf in the voucher and audit-log indicates
why the MASA issued the voucher. A "verified" entry means that why the MASA issued the voucher. A "verified" entry means that
the MASA issued the associated voucher as a result of positive the MASA issued the associated voucher as a result of positive
verification of ownership. However, this entry does not indicate verification of ownership. However, this entry does not indicate
whether the pledge was actually deployed in the prior domain, or whether or not the pledge was actually deployed in the prior
not. A "logged" assertion informs the registrar that the prior domain. A "logged" assertion informs the registrar that the prior
vouchers were issued with minimal verification. A "proximity" vouchers were issued with minimal verification. A "proximity"
assertion assures the registrar that the pledge was truly assertion assures the registrar that the pledge was truly
communicating with the prior domain and thus provides assurance communicating with the prior domain and thus provides assurance
that the prior domain really has deployed the pledge. that the prior domain really has deployed the pledge.
A relatively simple policy is to white list known (internal or A relatively simple policy is to acceptlist known (internal or
external) domainIDs, and require all vouchers to have a nonce. An external) domainIDs and require all vouchers to have a nonce. An
alternative is to require that all nonceless vouchers be from a alternative is to require that all nonceless vouchers be from a
subset (e.g. only internal) of domainIDs. If the policy is violated subset (e.g., only internal) of domainIDs. If the policy is
a simple action is to revoke any locally issued credentials for the violated, a simple action is to revoke any locally issued credentials
pledge in question or to refuse to forward the voucher. The for the pledge in question or to refuse to forward the voucher. The
Registrar MUST then refuse any EST actions, and SHOULD inform a human registrar MUST then refuse any EST actions and SHOULD inform a human
via a log. A registrar MAY be configured to ignore (i.e. override via a log. A registrar MAY be configured to ignore (i.e., override
the above policy) the history of the device but it is RECOMMENDED the above policy) the history of the device, but it is RECOMMENDED
that this only be configured if hardware assisted (i.e. TPM that this only be configured if hardware-assisted (i.e., Transport
anchored) Network Endpoint Assessment (NEA) [RFC5209] is supported. Performance Metrics (TPM) anchored) Network Endpoint Assessment (NEA)
[RFC5209] is supported.
5.9. EST Integration for PKI bootstrapping 5.9. EST Integration for PKI Bootstrapping
The pledge SHOULD follow the BRSKI operations with EST enrollment The pledge SHOULD follow the BRSKI operations with EST enrollment
operations including "CA Certificates Request", "CSR Attributes" and operations including "CA Certificates Request", "CSR Attributes
"Client Certificate Request" or "Server-Side Key Generation", etc. Request", and "Client Certificate Request" or "Server-Side Key
This is a relatively seamless integration since BRSKI API calls Generation", etc. This is a relatively seamless integration since
provide an automated alternative to the manual bootstrapping method BRSKI API calls provide an automated alternative to the manual
described in [RFC7030]. As noted above, use of HTTP persistent bootstrapping method described in [RFC7030]. As noted above, use of
connections simplifies the pledge state machine. HTTP-persistent connections simplifies the pledge state machine.
Although EST allows clients to obtain multiple certificates by Although EST allows clients to obtain multiple certificates by
sending multiple Certificate Signing Requests (CSR) requests, BRSKI sending multiple Certificate Signing Requests (CSRs), BRSKI does not
does not support this mechanism directly. This is because BRSKI support this mechanism directly. This is because BRSKI pledges MUST
pledges MUST use the CSR Attributes request ([RFC7030] section 4.5). use the CSR Attributes request ([RFC7030], Section 4.5). The
The registrar MUST validate the CSR against the expected attributes. registrar MUST validate the CSR against the expected attributes.
This implies that client requests will "look the same" and therefore This implies that client requests will "look the same" and therefore
result in a single logical certificate being issued even if the result in a single logical certificate being issued even if the
client were to make multiple requests. Registrars MAY contain more client were to make multiple requests. Registrars MAY contain more
complex logic but doing so is out-of-scope of this specification. complex logic, but doing so is out of scope of this specification.
BRSKI does not signal any enhancement or restriction to this BRSKI does not signal any enhancement or restriction to this
capability. capability.
5.9.1. EST Distribution of CA Certificates 5.9.1. EST Distribution of CA Certificates
The pledge SHOULD request the full EST Distribution of CA The pledge SHOULD request the full EST Distribution of CA certificate
Certificates message. See RFC7030, section 4.1. messages; see [RFC7030], Section 4.1.
This ensures that the pledge has the complete set of current CA This ensures that the pledge has the complete set of current CA
certificates beyond the pinned-domain-cert (see Section 5.6.2 for a certificates beyond the pinned-domain-cert (see Section 5.6.2 for a
discussion of the limitations inherent in having a single certificate discussion of the limitations inherent in having a single certificate
instead of a full CA Certificates response.) Although these instead of a full CA certificate response). Although these
limitations are acceptable during initial bootstrapping, they are not limitations are acceptable during initial bootstrapping, they are not
appropriate for ongoing PKIX end entity certificate validation. appropriate for ongoing PKIX end-entity certificate validation.
5.9.2. EST CSR Attributes 5.9.2. EST CSR Attributes
Automated bootstrapping occurs without local administrative Automated bootstrapping occurs without local administrative
configuration of the pledge. In some deployments it is plausible configuration of the pledge. In some deployments, it is plausible
that the pledge generates a certificate request containing only that the pledge generates a certificate request containing only
identity information known to the pledge (essentially the X.509 identity information known to the pledge (essentially the X.509
IDevID information) and ultimately receives a certificate containing IDevID information) and ultimately receives a certificate containing
domain specific identity information. Conceptually the CA has domain-specific identity information. Conceptually, the CA has
complete control over all fields issued in the end entity complete control over all fields issued in the end-entity
certificate. Realistically this is operationally difficult with the certificate. Realistically, this is operationally difficult with the
current status of PKI certificate authority deployments, where the current status of PKI CA deployments, where the CSR is submitted to
CSR is submitted to the CA via a number of non-standard protocols. the CA via a number of non-standard protocols. Even with all
Even with all standardized protocols used, it could operationally be standardized protocols used, it could operationally be problematic to
problematic to expect that service specific certificate fields can be expect that service-specific certificate fields can be created by a
created by a CA that is likely operated by a group that has no CA that is likely operated by a group that has no insight into
insight into different network services/protocols used. For example, different network services/protocols used. For example, the CA could
the CA could even be outsourced. even be outsourced.
To alleviate these operational difficulties, the pledge MUST request To alleviate these operational difficulties, the pledge MUST request
the EST "CSR Attributes" from the EST server and the EST server needs the EST "CSR Attributes" from the EST server, and the EST server
to be able to reply with the attributes necessary for use of the needs to be able to reply with the attributes necessary for use of
certificate in its intended protocols/services. This approach allows the certificate in its intended protocols/services. This approach
for minimal CA integrations and instead the local infrastructure (EST allows for minimal CA integrations, and instead, the local
server) informs the pledge of the proper fields to include in the infrastructure (EST server) informs the pledge of the proper fields
generated CSR (such as rfc822Name). This approach is beneficial to to include in the generated CSR (such as rfc822Name). This approach
automated bootstrapping in the widest number of environments. is beneficial to automated bootstrapping in the widest number of
environments.
In networks using the BRSKI enrolled certificate to authenticate the In networks using the BRSKI enrolled certificate to authenticate the
ACP (Autonomic Control Plane), the EST CSR attributes MUST include ACP, the EST CSR Attributes MUST include the ACP domain information
the ACP Domain Information Fields defined in fields defined in [RFC8994], Section 6.2.2.
[I-D.ietf-anima-autonomic-control-plane] section 6.1.1.
The registrar MUST also confirm that the resulting CSR is formatted The registrar MUST also confirm that the resulting CSR is formatted
as indicated before forwarding the request to a CA. If the registrar as indicated before forwarding the request to a CA. If the registrar
is communicating with the CA using a protocol such as full CMC, which is communicating with the CA using a protocol such as full
provides mechanisms to override the CSR attributes, then these Certificate Management over CMS (CMC), which provides mechanisms to
mechanisms MAY be used even if the client ignores CSR Attribute override the CSR Attributes, then these mechanisms MAY be used even
guidance. if the client ignores the guidance for the CSR Attributes.
5.9.3. EST Client Certificate Request 5.9.3. EST Client Certificate Request
The pledge MUST request a new client certificate. See RFC7030, The pledge MUST request a new Client Certificate; see [RFC7030],
section 4.2. Section 4.2.
5.9.4. Enrollment Status Telemetry 5.9.4. Enrollment Status Telemetry
For automated bootstrapping of devices, the administrative elements For automated bootstrapping of devices, the administrative elements
providing bootstrapping also provide indications to the system that provide bootstrapping also provide indications to the system
administrators concerning device lifecycle status. This might administrators concerning device life-cycle status. This might
include information concerning attempted bootstrapping messages seen include information concerning attempted bootstrapping messages seen
by the client. The MASA provides logs and status of credential by the client. The MASA provides logs and the status of credential
enrollment. [RFC7030] assumes an end user and therefore does not enrollment. Since an end user is assumed per [RFC7030], a final
include a final success indication back to the server. This is success indication back to the server is not included. This is
insufficient for automated use cases. insufficient for automated use cases.
The client MUST send an indicator to the Registrar about its The client MUST send an indicator to the registrar about its
enrollment status. It does this by using an HTTP POST of a JSON enrollment status. It does this by using an HTTP POST of a JSON
dictionary with the of attributes described below to the new EST dictionary with the attributes described below to the new EST
endpoint at "/.well-known/brski/enrollstatus". (XXX ?) endpoint at "/.well-known/brski/enrollstatus".
When indicating a successful enrollment the client SHOULD first re- When indicating a successful enrollment, the client SHOULD first re-
establish the EST TLS session using the newly obtained credentials. establish the EST TLS session using the newly obtained credentials.
TLS 1.2 supports doing this in-band, but TLS 1.3 does not. The TLS 1.3 supports doing this in-band, but TLS 1.2 does not. The
client SHOULD therefore always close the existing TLS connection, and client SHOULD therefore always close the existing TLS connection and
start a new one. start a new one, using the same Join Proxy.
In the case of a failed enrollment, the client MUST send the In the case of a failed enrollment, the client MUST send the
telemetry information over the same TLS connection that was used for telemetry information over the same TLS connection that was used for
the enrollment attempt, with a Reason string indicating why the most the enrollment attempt, with a Reason string indicating why the most
recent enrollment failed. (For failed attempts, the TLS connection recent enrollment failed. (For failed attempts, the TLS connection
is the most reliable way to correlate server-side information with is the most reliable way to correlate server-side information with
what the client provides.) what the client provides.)
The version and status fields MUST be present. The Reason field The version and status fields MUST be present. The Reason field
SHOULD be present whenever the status field is false. In the case of SHOULD be present whenever the status field is false. In the case of
a SUCCESS the Reason string MAY be omitted. a SUCCESS, the Reason string MAY be omitted.
The reason-context attribute is an arbitrary JSON object (literal The reason-context attribute is an arbitrary JSON object (literal
value or hash of values) which provides additional information value or hash of values) that provides additional information
specific to the failure to unroll from this pledge. The contents of specific to the failure to unroll from this pledge. The contents of
this field are not subject to standardization. This is represented this field are not subject to standardization. This is represented
by the group-socket "$$arbitrary-map" in the CDDL. by the group-socket "$$arbitrary-map" in the CDDL.
In the case of a SUCCESS the Reason string is omitted.
<CODE BEGINS> file "enrollstatus.cddl" <CODE BEGINS> file "enrollstatus.cddl"
enrollstatus-post = { enrollstatus-post = {
"version": uint, "version": uint,
"status": bool, "status": bool,
? "reason": text, ? "reason": text,
? "reason-context" : { $$arbitrary-map } ? "reason-context" : { $$arbitrary-map }
} }
} }
<CODE ENDS> <CODE ENDS>
Figure 19: CDDL for enrollment status POST Figure 19: CDDL for Enrollment Status POST
An example status report can be seen below. It is sent with with the An example status report can be seen below. It is sent with the
media type: application/json media type: application/json
{ {
"version": 1, "version": 1,
"status":true, "status":true,
"reason":"Informative human readable message", "reason":"Informative human readable message",
"reason-context": { "additional" : "JSON" } "reason-context": { "additional" : "JSON" }
} }
Figure 20: Example of enrollment status POST Figure 20: Example of Enrollment Status POST
The server SHOULD respond with an HTTP 200 but MAY simply fail with The server SHOULD respond with an HTTP 200 but MAY simply fail with
an HTTP 404 error. an HTTP 404 error.
Within the server logs the server MUST capture if this message was Within the server logs, the server MUST capture if this message was
received over an TLS session with a matching client certificate. received over a TLS session with a matching Client Certificate.
5.9.5. Multiple certificates 5.9.5. Multiple Certificates
Pledges that require multiple certificates could establish direct EST Pledges that require multiple certificates could establish direct EST
connections to the registrar. connections to the registrar.
5.9.6. EST over CoAP 5.9.6. EST over CoAP
This document describes extensions to EST for the purposes of This document describes extensions to EST for the purpose of
bootstrapping of remote key infrastructures. Bootstrapping is bootstrapping remote key infrastructures. Bootstrapping is relevant
relevant for CoAP enrollment discussions as well. The definition of for CoAP enrollment discussions as well. The definition of EST and
EST and BRSKI over CoAP is not discussed within this document beyond BRSKI over CoAP is not discussed within this document beyond ensuring
ensuring proxy support for CoAP operations. Instead it is proxy support for CoAP operations. Instead, it is anticipated that a
anticipated that a definition of CoAP mappings will occur in definition of CoAP mappings will occur in subsequent documents such
subsequent documents such as [I-D.ietf-ace-coap-est] and that CoAP as [ACE-COAP-EST] and that CoAP mappings for BRSKI will be discussed
mappings for BRSKI will be discussed either there or in future work. either there or in future work.
6. Clarification of transfer-encoding 6. Clarification of Transfer-Encoding
[RFC7030] defines its endpoints to include a "Content-Transfer- [RFC7030] defines endpoints to include a "Content-Transfer-Encoding"
Encoding" heading, and the payloads to be [RFC4648] Base64 encoded heading and payloads to be base64-encoded DER [RFC4648].
DER.
When used within BRSKI, the original RFC7030 EST endpoints remain When used within BRSKI, the original EST endpoints remain base64
Base64 encoded, but the new BRSKI end points which send and receive encoded [RFC7030] (as clarified by [RFC8951]), but the new BRSKI
binary artifacts (specifically, "/.well-known/brski/requestvoucher") endpoints that send and receive binary artifacts (specifically,
are binary. That is, no encoding is used. "/.well-known/brski/requestvoucher") are binary. That is, no
encoding is used.
In the BRSKI context, the EST "Content-Transfer-Encoding" header In the BRSKI context, the EST "Content-Transfer-Encoding" header
field if present, SHOULD be ignored. This header field does not need field SHOULD be ignored if present. This header field does not need
to be included. to be included.
7. Reduced security operational modes 7. Reduced Security Operational Modes
A common requirement of bootstrapping is to support less secure A common requirement of bootstrapping is to support less secure
operational modes for support specific use cases. This section operational modes for support-specific use cases. This section
suggests a range of mechanisms that would alter the security suggests a range of mechanisms that would alter the security
assurance of BRSKI to accommodate alternative deployment assurance of BRSKI to accommodate alternative deployment
architectures and mitigate lifecycle management issues identified in architectures and mitigate life-cycle management issues identified in
Section 10. They are presented here as informative (non-normative) Section 10. They are presented here as informative (non-normative)
design guidance for future standardization activities. Section 9 design guidance for future standardization activities. Section 9
provides standardization applicability statements for the ANIMA ACP. provides standardization applicability statements for the ANIMA ACP.
Other users would be expected that subsets of these mechanisms could Other users would expect that subsets of these mechanisms could be
be profiled with an accompanying applicability statements similar to profiled with accompanying applicability statements similar to the
the one described in Section 9. one described in Section 9.
This section is considered non-normative in the generality of the This section is considered non-normative in the generality of the
protocol. Use of the suggested mechanisms here MUST be detailed in protocol. Use of the suggested mechanisms here MUST be detailed in
specific profiles of BRSKI, such as in Section 9. specific profiles of BRSKI, such as in Section 9.
7.1. Trust Model 7.1. Trust Model
This section explains the trust relationships detailed in This section explains the trust relationships detailed in
Section 2.4: Section 2.4:
+--------+ +---------+ +------------+ +------------+ +--------+ +---------+ +------------+ +------------+
| Pledge | | Join | | Domain | |Manufacturer| | Pledge | | Join | | Domain | |Manufacturer|
| | | Proxy | | Registrar | | Service | | | | Proxy | | Registrar | | Service |
| | | | | | | (Internet) | | | | | | | | (Internet) |
+--------+ +---------+ +------------+ +------------+ +--------+ +---------+ +------------+ +------------+
Figure 10 Figure 21: Elements of BRSKI Trust Model
Pledge: The pledge could be compromised and providing an attack Pledge: The pledge could be compromised and provide an attack vector
vector for malware. The entity is trusted to only imprint using for malware. The entity is trusted to only imprint using secure
secure methods described in this document. Additional endpoint methods described in this document. Additional endpoint
assessment techniques are RECOMMENDED but are out-of-scope of this assessment techniques are RECOMMENDED but are out of scope of this
document. document.
Join Proxy: Provides proxy functionalities but is not involved in Join Proxy: Provides proxy functionalities but is not involved in
security considerations. security considerations.
Registrar: When interacting with a MASA a registrar makes all Registrar: When interacting with a MASA, a registrar makes all
decisions. For Ownership Audit Vouchers (see [RFC8366]) the decisions. For Ownership Audit Vouchers (see [RFC8366]), the
registrar is provided an opportunity to accept MASA decisions. registrar is provided an opportunity to accept MASA decisions.
Vendor Service, MASA: This form of manufacturer service is trusted Vendor Service, MASA: This form of manufacturer service is trusted
to accurately log all claim attempts and to provide authoritative to accurately log all claim attempts and to provide authoritative
log information to registrars. The MASA does not know which log information to registrars. The MASA does not know which
devices are associated with which domains. These claims could be devices are associated with which domains. These claims could be
strengthened by using cryptographic log techniques to provide strengthened by using cryptographic log techniques to provide
append only, cryptographic assured, publicly auditable logs. append only, cryptographic assured, publicly auditable logs.
Vendor Service, Ownership Validation: This form of manufacturer Vendor Service, Ownership Validation: This form of manufacturer
service is trusted to accurately know which device is owned by service is trusted to accurately know which device is owned by
which domain. which domain.
7.2. Pledge security reductions 7.2. Pledge Security Reductions
The following is a list of alternative behaviours that the pledge can The following is a list of alternative behaviors that the pledge can
be programmed to implement. These behaviours are not mutually be programmed to implement. These behaviors are not mutually
exclusive, nor are they dependent upon each other. Some of these exclusive, nor are they dependent upon each other. Some of these
methods enable offline and emergency (touch based) deployment use methods enable offline and emergency (touch-based) deployment use
cases. Normative language is used as these behaviours are referenced cases. Normative language is used as these behaviors are referenced
in later sections in a normative fashion. in later sections in a normative fashion.
1. The pledge MUST accept nonceless vouchers. This allows for a use 1. The pledge MUST accept nonceless vouchers. This allows for a use
case where the registrar can not connect to the MASA at the case where the registrar cannot connect to the MASA at the
deployment time. Logging and validity periods address the deployment time. Logging and validity periods address the
security considerations of supporting these use cases. security considerations of supporting these use cases.
2. Many devices already support "trust on first use" for physical 2. Many devices already support "trust on first use" for physical
interfaces such as console ports. This document does not change interfaces such as console ports. This document does not change
that reality. Devices supporting this protocol MUST NOT support that reality. Devices supporting this protocol MUST NOT support
"trust on first use" on network interfaces. This is because "trust on first use" on network interfaces. This is because
"trust on first use" over network interfaces would undermine the "trust on first use" over network interfaces would undermine the
logging based security protections provided by this logging based security protections provided by this
specification. specification.
3. The pledge MAY have an operational mode where it skips voucher 3. The pledge MAY have an operational mode where it skips voucher
validation one time. For example if a physical button is validation one time, for example, if a physical button is
depressed during the bootstrapping operation. This can be useful depressed during the bootstrapping operation. This can be useful
if the manufacturer service is unavailable. This behavior SHOULD if the manufacturer service is unavailable. This behavior SHOULD
be available via local configuration or physical presence methods be available via local configuration or physical presence methods
(such as use of a serial/craft console) to ensure new entities (such as use of a serial/craft console) to ensure new entities
can always be deployed even when autonomic methods fail. This can always be deployed even when autonomic methods fail. This
allows for unsecured imprint. allows for unsecured imprint.
4. A craft/serial console could include a command such as "est- 4. A craft/serial console could include a command such as "est-
enroll [2001:db8:0:1]:443" that begins the EST process from the enroll [2001:db8:0:1]:443" that begins the EST process from the
point after the voucher is validated. This process SHOULD point after the voucher is validated. This process SHOULD
include server certificate verification using an on-screen include server certificate verification using an on-screen
fingerprint. fingerprint.
It is RECOMMENDED that "trust on first use" or any method of skipping It is RECOMMENDED that "trust on first use" or any method of skipping
voucher validation (including use of craft serial console) only be voucher validation (including use of a craft serial console) only be
available if hardware assisted Network Endpoint Assessment (NEA: available if hardware-assisted Network Endpoint Assessment (NEA)
[RFC5209]) is supported. This recommendation ensures that domain [RFC5209] is supported. This recommendation ensures that domain
network monitoring can detect inappropriate use of offline or network monitoring can detect inappropriate use of offline or
emergency deployment procedures when voucher-based bootstrapping is emergency deployment procedures when voucher-based bootstrapping is
not used. not used.
7.3. Registrar security reductions 7.3. Registrar Security Reductions
A registrar can choose to accept devices using less secure methods. A registrar can choose to accept devices using less secure methods.
They MUST NOT be the default behavior. These methods may be They MUST NOT be the default behavior. These methods may be
acceptable in situations where threat models indicate that low acceptable in situations where threat models indicate that low
security is adequate. This includes situations where security security is adequate. This includes situations where security
decisions are being made by the local administrator: decisions are being made by the local administrator:
1. A registrar MAY choose to accept all devices, or all devices of a 1. A registrar MAY choose to accept all devices, or all devices of a
particular type, at the administrator's discretion. This could particular type. The administrator could make this choice in
occur when informing all registrars of unique identifiers of new cases where it is operationally difficult to configure the
entities might be operationally difficult. registrar with the unique identifier of each new device expected.
2. A registrar MAY choose to accept devices that claim a unique 2. A registrar MAY choose to accept devices that claim a unique
identity without the benefit of authenticating that claimed identity without the benefit of authenticating that claimed
identity. This could occur when the pledge does not include an identity. This could occur when the pledge does not include an
X.509 IDevID factory installed credential. New Entities without X.509 IDevID factory-installed credential. New entities without
an X.509 IDevID credential MAY form the Section 5.2 request using an X.509 IDevID credential MAY form the request per Section 5.2
the Section 5.5 format to ensure the pledge's serial number using the format per Section 5.5 to ensure the pledge's serial
information is provided to the registrar (this includes the number information is provided to the registrar (this includes
IDevID AuthorityKeyIdentifier value, which would be statically the IDevID AuthorityKeyIdentifier value, which would be
configured on the pledge.) The pledge MAY refuse to provide a statically configured on the pledge). The pledge MAY refuse to
TLS client certificate (as one is not available.) The pledge provide a TLS Client Certificate (as one is not available). The
SHOULD support HTTP-based or certificate-less TLS authentication pledge SHOULD support HTTP-based or certificate-less TLS
as described in EST RFC7030 section 3.3.2. A registrar MUST NOT authentication as described in EST [RFC7030], Section 3.3.2. A
accept unauthenticated New Entities unless it has been configured registrar MUST NOT accept unauthenticated new entities unless it
to do so by an administrator that has verified that only expected has been configured to do so by an administrator that has
new entities can communicate with a registrar (presumably via a verified that only expected new entities can communicate with a
physically secured perimeter.) registrar (presumably via a physically secured perimeter.)
3. A registrar MAY submit a nonceless voucher-requests to the MASA 3. A registrar MAY submit a nonceless voucher-request to the MASA
service (by not including a nonce in the voucher-request.) The service (by not including a nonce in the voucher-request). The
resulting vouchers can then be stored by the registrar until they resulting vouchers can then be stored by the registrar until they
are needed during bootstrapping operations. This is for use are needed during bootstrapping operations. This is for use
cases where the target network is protected by an air gap and cases where the target network is protected by an air gap and
therefore cannot contact the MASA service during pledge therefore cannot contact the MASA service during pledge
deployment. deployment.
4. A registrar MAY ignore unrecognized nonceless log entries. This 4. A registrar MAY ignore unrecognized nonceless log entries. This
could occur when used equipment is purchased with a valid history could occur when used equipment is purchased with a valid history
being deployed in air gap networks that required offline of being deployed in air gap networks that required offline
vouchers. vouchers.
5. A registrar MAY accept voucher formats of future types that can 5. A registrar MAY accept voucher formats of future types that
not be parsed by the Registrar. This reduces the Registrar's cannot be parsed by the registrar. This reduces the registrar's
visibility into the exact voucher contents but does not change visibility into the exact voucher contents but does not change
the protocol operations. the protocol operations.
7.4. MASA security reductions 7.4. MASA Security Reductions
Lower security modes chosen by the MASA service affect all device Lower security modes chosen by the MASA service affect all device
deployments unless the lower-security behavior is tied to specific deployments unless the lower security behavior is tied to specific
device identities. The modes described below can be applied to device identities. The modes described below can be applied to
specific devices via knowledge of what devices were sold. They can specific devices via knowledge of what devices were sold. They can
also be bound to specific customers (independent of the device also be bound to specific customers (independent of the device
identity) by authenticating the customer's Registrar. identity) by authenticating the customer's registrar.
7.4.1. Issuing Nonceless vouchers 7.4.1. Issuing Nonceless Vouchers
A MASA has the option of not including a nonce in the voucher, and/or A MASA has the option of not including a nonce in the voucher and/or
not requiring one to be present in the voucher-request. This results not requiring one to be present in the voucher-request. This results
in distribution of a voucher that may never expire and in effect in distribution of a voucher that may never expire and, in effect,
makes the specified Domain an always trusted entity to the pledge makes the specified domain an always trusted entity to the pledge
during any subsequent bootstrapping attempts. That a nonceless during any subsequent bootstrapping attempts. The log information
voucher was issued is captured in the log information so that the captures when a nonceless voucher is issued so that the registrar can
registrar can make appropriate security decisions when a pledge joins make appropriate security decisions when a pledge joins the domain.
the Domain. Nonceless vouchers are useful to support use cases where Nonceless vouchers are useful to support use cases where registrars
registrars might not be online during actual device deployment. might not be online during actual device deployment.
While a nonceless voucher may include an expiry date, a typical use While a nonceless voucher may include an expiry date, a typical use
for a nonceless voucher is for it to be long-lived. If the device for a nonceless voucher is for it to be long lived. If the device
can be trusted to have an accurate clock (the MASA will know), then a can be trusted to have an accurate clock (the MASA will know), then a
nonceless voucher CAN be issued with a limited lifetime. nonceless voucher CAN be issued with a limited lifetime.
A more typical case for a nonceless voucher is for use with offline A more typical case for a nonceless voucher is for use with offline
onboarding scenarios where it is not possible to pass a fresh onboarding scenarios where it is not possible to pass a fresh
voucher-request to the MASA. The use of a long-lived voucher also voucher-request to the MASA. The use of a long-lived voucher also
eliminates concern about the availability of the MASA many years in eliminates concern about the availability of the MASA many years in
the future. Thus many nonceless vouchers will have no expiry dates. the future. Thus, many nonceless vouchers will have no expiry dates.
Thus, the long lived nonceless voucher does not require the proof Thus, the long-lived nonceless voucher does not require proof that
that the device is online. Issuing such a thing is only accepted the device is online. Issuing such a thing is only accepted when the
when the registrar is authenticated by the MASA and the MASA is registrar is authenticated by the MASA and the MASA is authorized to
authorized to provide this functionality to this customer. The MASA provide this functionality to this customer. The MASA is RECOMMENDED
is RECOMMENDED to use this functionality only in concert with an to use this functionality only in concert with an enhanced level of
enhanced level of ownership tracking, the details of which are out of ownership tracking, the details of which are out of scope for this
scope for this document. document.
If the pledge device is known to have a real-time-clock that is set If the pledge device is known to have a real-time clock that is set
from the factory, use of a voucher validity period is RECOMMENDED. from the factory, use of a voucher validity period is RECOMMENDED.
7.4.2. Trusting Owners on First Use 7.4.2. Trusting Owners on First Use
A MASA has the option of not verifying ownership before responding A MASA has the option of not verifying ownership before responding
with a voucher. This is expected to be a common operational model with a voucher. This is expected to be a common operational model
because doing so relieves the manufacturer providing MASA services because doing so relieves the manufacturer providing MASA services
from having to track ownership during shipping and supply chain and from having to track ownership during shipping and throughout the
allows for a very low overhead MASA service. A registrar uses the supply chain, and it allows for a very low overhead MASA service. A
audit log information as a defense in depth strategy to ensure that registrar uses the audit-log information as an in-depth defense
this does not occur unexpectedly (for example when purchasing new strategy to ensure that this does not occur unexpectedly (for
equipment the registrar would throw an error if any audit log example, when purchasing new equipment, the registrar would throw an
information is reported.) The MASA SHOULD verify the 'prior-signed- error if any audit-log information is reported). The MASA SHOULD
voucher-request' information for pledges that support that verify the prior-signed-voucher-request information for pledges that
functionality. This provides a proof-of-proximity check that reduces support that functionality. This provides a proof-of-proximity check
the need for ownership verification. The proof-of-proximity comes that reduces the need for ownership verification. The proof-of-
from the assumption that the pledge and Join Proxy are on the same proximity comes from the assumption that the pledge and Join Proxy
link-local connection. are on the same link-local connection.
A MASA that practices Trust-on-First-Use (TOFU) for Registrar A MASA that practices TOFU for registrar identity may wish to
identity may wish to annotate the origin of the connection by IP annotate the origin of the connection by IP address or netblock and
address or netblock, and restrict future use of that identity from restrict future use of that identity from other locations. A MASA
other locations. A MASA that does this SHOULD take care to not that does this SHOULD take care to not create nuisance situations for
create nuisance situations for itself when a customer has multiple itself when a customer has multiple registrars or uses outgoing IPv4-
registrars, or uses outgoing IPv4 NAT44 connections that change to-IPv4 NAT (NAT44) connections that change frequently.
frequently.
7.4.3. Updating or extending voucher trust anchors 7.4.3. Updating or Extending Voucher Trust Anchors
This section deals with the problem of a MASA that is no longer This section deals with two problems: A MASA that is no longer
available due to a failed business, or the situation where a MASA is available due to a failed business and a MASA that is uncooperative
uncooperative to a secondary sale. to a secondary sale.
A manufacturer could offer a management mechanism that allows the A manufacturer could offer a management mechanism that allows the
list of voucher verification trust anchors to be extended. list of voucher verification trust anchors to be extended.
[I-D.ietf-netconf-keystore] is one such interface that could be [YANG-KEYSTORE] describes one such interface that could be
implemented using YANG. Pretty much any configuration mechanism used implemented using YANG. Pretty much any configuration mechanism used
today could be extended to provide the needed additional update. A today could be extended to provide the needed additional update. A
manufacturer could even decide to install the domain CA trust anchors manufacturer could even decide to install the domain CA trust anchors
received during the EST "cacerts" step as voucher verification received during the EST "cacerts" step as voucher verification
anchors. Some additional signals will be needed to clearly identify anchors. Some additional signals will be needed to clearly identify
which keys have voucher validation authority from among those signed which keys have voucher validation authority from among those signed
by the domain CA. This is future work. by the domain CA. This is future work.
With the above change to the list of anchors, vouchers can be issued With the above change to the list of anchors, vouchers can be issued
by an alternate MASA. This could be the previous owner (the seller), by an alternate MASA. This could be the previous owner (the seller)
or some other trusted third party who is mediating the sale. If it or some other trusted third party who is mediating the sale. If it
was a third party, then the seller would need to have taken steps to is a third party, the seller would need to take steps to introduce
introduce the third party configuration to the device prior the third-party configuration to the device prior to disconnection.
disconnection. The third party (e.g. a wholesaler of used equipment) The third party (e.g., a wholesaler of used equipment) could,
could however use a mechanism described in Section 7.2 to take however, use a mechanism described in Section 7.2 to take control of
control of the device after receiving it physically. This would the device after receiving it physically. This would permit the
permit the third party to act as the MASA for future onboarding third party to act as the MASA for future onboarding actions. As the
actions. As the IDevID certificate probably can not be replaced, the IDevID certificate probably cannot be replaced, the new owner's
new owner's Registrar would have to support an override of the MASA registrar would have to support an override of the MASA URL.
URL.
To be useful for resale or other transfers of ownership one of two To be useful for resale or other transfers of ownership, one of two
situations will need to occur. The simplest is that the device is situations will need to occur. The simplest is that the device is
not put through any kind of factory default/reset before going not put through any kind of factory default/reset before going
through onboarding again. Some other secure, physical signal would through onboarding again. Some other secure, physical signal would
be needed to initiate it. This is most suitable for redeploying a be needed to initiate it. This is most suitable for redeploying a
device within the same Enterprise. This would entail having previous device within the same enterprise. This would entail having previous
configuration in the system until entirely replaced by the new owner, configuration in the system until entirely replaced by the new owner,
and represents some level of risk. and it represents some level of risk.
The second mechanism is that there would need to be two levels of For the second scenario, there would need to be two levels of factory
factory reset. One would take the system back entirely to reset. One would take the system back entirely to manufacturer
manufacturer state, including removing any added trust anchors, and state, including removing any added trust anchors, and the other
the second (more commonly used) one would just restore the (more commonly used) one would just restore the configuration back to
configuration back to a known default without erasing trust anchors. a known default without erasing trust anchors. This weaker factory
This weaker factory reset might leave valuable credentials on the reset might leave valuable credentials on the device, and this may be
device and this may be unacceptable to some owners. unacceptable to some owners.
As a third option, the manufacturer's trust anchors could be entirely As a third option, the manufacturer's trust anchors could be entirely
overwritten with local trust anchors. A factory default would never overwritten with local trust anchors. A factory default would never
restore those anchors. This option comes with a lot of power, but restore those anchors. This option comes with a lot of power but is
also a lot of responsibility: if access to the private part of the also a lot of responsibility: if access to the private part of the
new anchors are lost the manufacturer may be unable to help. new anchors are lost, the manufacturer may be unable to help.
8. IANA Considerations 8. IANA Considerations
This document requires the following IANA actions: Per this document, IANA has completed the following actions.
8.1. The IETF XML Registry 8.1. The IETF XML Registry
This document registers a URI in the "IETF XML Registry" [RFC3688]. This document registers a URI in the "IETF XML Registry" [RFC3688].
IANA is asked to register the following: IANA has registered the following:
URI: urn:ietf:params:xml:ns:yang:ietf-voucher-request URI: urn:ietf:params:xml:ns:yang:ietf-voucher-request
Registrant Contact: The ANIMA WG of the IETF. Registrant Contact: The ANIMA WG of the IETF.
XML: N/A, the requested URI is an XML namespace. XML: N/A; the requested URI is an XML namespace.
8.2. YANG Module Names Registry 8.2. YANG Module Names Registry
This document registers a YANG module in the "YANG Module Names" This document registers a YANG module in the "YANG Module Names"
registry [RFC6020]. IANA is asked to register the following: registry [RFC6020]. IANA has registered the following:
name: ietf-voucher-request Name: ietf-voucher-request
namespace: urn:ietf:params:xml:ns:yang:ietf-voucher-request Namespace: urn:ietf:params:xml:ns:yang:ietf-voucher-request
prefix: vch Prefix: vch
reference: THIS DOCUMENT Reference: RFC 8995
8.3. BRSKI well-known considerations 8.3. BRSKI Well-Known Considerations
8.3.1. BRSKI .well-known registration 8.3.1. BRSKI .well-known Registration
To the Well-Known URIs Registry, at: To the "Well-Known URIs" registry at
"https://www.iana.org/assignments/well-known-uris/well-known- https://www.iana.org/assignments/well-known-uris/, this document
uris.xhtml", this document registers the well-known name "brski" with registers the well-known name "brski" with the following filled-in
the following filled-in template from [RFC5785]: template from [RFC8615]:
URI suffix: brski URI Suffix: brski
Change Controller: IETF Change Controller: IETF
IANA is asked to change the registration of "est" to now only include IANA has changed the registration of "est" to now only include
RFC7030 and no longer this document. Earlier versions of this [RFC7030] and no longer this document. Earlier draft versions of
document used "/.well-known/est" rather than "/.well-known/brski". this document used "/.well-known/est" rather than "/.well-known/
brski".
8.3.2. BRSKI .well-known registry 8.3.2. BRSKI .well-known Registry
IANA is requested to create a new Registry entitled: "BRSKI well- IANA has created a new registry entitled: "BRSKI Well-Known URIs".
known URIs". The registry shall have at least three columns: URI, The registry has three columns: URI, Description, and Reference. New
description, and reference. New items can be added using the items can be added using the Specification Required [RFC8126]
Specification Required process. The initial contents of this process. The initial contents of this registry are:
registry shall be:
URI document description +=================+==========================+===========+
requestvoucher [THISRFC] pledge to registrar, and from registrar to MASA | URI | Description | Reference |
voucher_status [THISRFC] pledge to registrar +=================+==========================+===========+
requestauditlog [THISRFC] registrar to MASA | requestvoucher | pledge to registrar, and | RFC 8995 |
enrollstatus [THISRFC] pledge to registrar | | from registrar to MASA | |
+-----------------+--------------------------+-----------+
| voucher_status | pledge to registrar | RFC 8995 |
+-----------------+--------------------------+-----------+
| requestauditlog | registrar to MASA | RFC 8995 |
+-----------------+--------------------------+-----------+
| enrollstatus | pledge to registrar | RFC 8995 |
+-----------------+--------------------------+-----------+
Table 1: BRSKI Well-Known URIs
8.4. PKIX Registry 8.4. PKIX Registry
IANA is requested to register the following: IANA has registered the following:
This document requests a number for id-mod-MASAURLExtn2016(TBD) from a number for id-mod-MASAURLExtn2016(96) from the pkix(7) id-mod(0)
the pkix(7) id-mod(0) Registry. Registry.
This document has received an early allocation from the id-pe IANA has assigned a number from the id-pe registry (Structure of
registry (SMI Security for PKIX Certificate Extension) for id-pe- Management Information (SMI) Security for PKIX Certificate Extension)
masa-url with the value 32, resulting in an OID of for id-pe-masa-url with the value 32, resulting in an OID of
1.3.6.1.5.5.7.1.32. 1.3.6.1.5.5.7.1.32.
8.5. Pledge BRSKI Status Telemetry 8.5. Pledge BRSKI Status Telemetry
IANA is requested to create a new Registry entitled: "BRSKI IANA has created a new registry entitled "BRSKI Parameters" and has
Parameters", and within that Registry to create a table called: created, within that registry, a table called: "Pledge BRSKI Status
"Pledge BRSKI Status Telemetry Attributes". New items can be added Telemetry Attributes". New items can be added using the
using the Specification Required process. The following items are to Specification Required process. The following items are in the
be in the initial registration, with this document (Section 5.7) as initial registration, with this document (see Section 5.7) as the
the reference: reference:
* version * version
* Status * Status
* Reason * Reason
* reason-context * reason-context
8.6. DNS Service Names 8.6. DNS Service Names
IANA is requested to register the following Service Names: IANA has registered the following service names:
Service Name: brski-proxy Service Name: brski-proxy
Transport Protocol(s): tcp Transport Protocol(s): tcp
Assignee: IESG <iesg@ietf.org>. Assignee: IESG <iesg@ietf.org>
Contact: IESG <iesg@ietf.org> Contact: IESG <iesg@ietf.org>
Description: The Bootstrapping Remote Secure Key Description: The Bootstrapping Remote Secure Key Infrastructure
Infrastructures Proxy Proxy
Reference: [This document] Reference: RFC 8995
Service Name: brski-registrar Service Name: brski-registrar
Transport Protocol(s): tcp Transport Protocol(s): tcp
Assignee: IESG <iesg@ietf.org>. Assignee: IESG <iesg@ietf.org>
Contact: IESG <iesg@ietf.org> Contact: IESG <iesg@ietf.org>
Description: The Bootstrapping Remote Secure Key Description: The Bootstrapping Remote Secure Key Infrastructure
Infrastructures Registrar Registrar
Reference: [This document] Reference: RFC 8995
8.7. GRASP Objective Names 8.7. GRASP Objective Names
IANA is requested to register the following GRASP Objective Names: IANA has registered the following GRASP Objective Names:
The IANA is requested to register the value "AN_Proxy" (without IANA has registered the value "AN_Proxy" (without quotes) to the
quotes) to the GRASP Objectives Names Table in the GRASP Parameter "GRASP Objective Names" table in the GRASP Parameter registry. The
Registry. The specification for this value is this document, specification for this value is Section 4.1.1 of this document.
Section 4.1.1.
The IANA is requested to register the value "AN_join_registrar" The IANA has registered the value "AN_join_registrar" (without
(without quotes) to the GRASP Objectives Names Table in the GRASP quotes) to the "GRASP Objective Names" table in the GRASP Parameter
Parameter Registry. The specification for this value is this registry. The specification for this value is Section 4.3 of this
document, Section 4.3. document.
9. Applicability to the Autonomic Control Plane (ACP) 9. Applicability to the Autonomic Control Plane (ACP)
This document provides a solution to the requirements for secure This document provides a solution to the requirements for secure
bootstrap set out in Using an Autonomic Control Plane for Stable bootstrapping as defined in "Using an Autonomic Control Plane for
Connectivity of Network Operations, Administration, and Maintenance Stable Connectivity of Network Operations, Administration, and
[RFC8368], A Reference Model for Autonomic Networking Maintenance (OAM)" [RFC8368], "A Reference Model for Autonomic
[I-D.ietf-anima-reference-model] and specifically the An Autonomic Networking" [RFC8993], and specifically "An Autonomic Control Plane
Control Plane (ACP) [I-D.ietf-anima-autonomic-control-plane], section (ACP)" [RFC8994]; see Sections 3.2 ("Secure Bootstrap over an
3.2 (Secure Bootstrap), and section 6.1 (ACP Domain, Certificate and Unconfigured Network") and 6.2 ("ACP Domain, Certificate, and
Network). Network").
The protocol described in this document has appeal in a number of The protocol described in this document has appeal in a number of
other non-ANIMA use cases. Such uses of the protocol will be other non-ANIMA use cases. Such uses of the protocol will be
deploying into other environments with different tradeoffs of deployed into other environments with different tradeoffs of privacy,
privacy, security, reliability and autonomy from manufacturers. As security, reliability, and autonomy from manufacturers. As such,
such those use cases will need to provide their own applicability those use cases will need to provide their own applicability
statements, and will need to address unique privacy and security statements and will need to address unique privacy and security
considerations for the environments in which they are used. considerations for the environments in which they are used.
The autonomic control plane (ACP) that is bootstrapped by the BRSKI The ACP that is bootstrapped by the BRSKI protocol is typically used
protocol is typically used in medium to large Internet Service in medium to large Internet service provider organizations.
Provider organizations. Equivalent enterprises that have significant Equivalent enterprises that have significant Layer 3 router
layer-3 router connectivity also will find significant benefit, connectivity also will find significant benefit, particularly if the
particularly if the Enterprise has many sites. (A network consisting enterprise has many sites. (A network consisting of primarily Layer
of primarily layer-2 is not excluded, but the adjacencies that the 2 is not excluded, but the adjacencies that the ACP will create and
ACP will create and maintain will not reflect the topology until all maintain will not reflect the topology until all devices participate
devices participate in the ACP). in the ACP.)
In the ACP, the Join Proxy is found to be proximal because In the ACP, the Join Proxy is found to be proximal because
communication between the pledge and the join proxy is exclusively on communication between the pledge and the Join Proxy is exclusively on
IPv6 Link-Local addresses. The proximity of the Join Proxy to the IPv6 link-local addresses. The proximity of the Join Proxy to the
Registrar is validated by the Registrar using ANI ACP IPv6 Unique registrar is validated by the registrar using ANI ACP IPv6 ULAs.
Local Addresses (ULA). ULAs are not routable over the Internet, so ULAs are not routable over the Internet, so as long as the Join Proxy
as long as the Join Proxy is operating correctly the proximity is operating correctly, the proximity assertion is satisfied. Other
asssertion is satisfied. Other uses of BRSKI will need make similar uses of BRSKI will need similar analysis if they use proximity
analysis if they use proximity assertions. assertions.
As specified in the ANIMA charter, this work "..focuses on As specified in the ANIMA charter, this work "focuses on
professionally-managed networks." Such a network has an operator and professionally-managed networks." Such a network has an operator and
can do things like install, configure and operate the Registrar can do things like install, configure, and operate the registrar
function. The operator makes purchasing decisions and is aware of function. The operator makes purchasing decisions and is aware of
what manufacturers it expects to see on its network. what manufacturers it expects to see on its network.
Such an operator is also capable of performing bootstrapping of a Such an operator is also capable of performing bootstrapping of a
device using a serial-console (craft console). The zero-touch device using a serial console (craft console). The zero-touch
mechanism presented in this and the ACP document mechanism presented in this and the ACP document [RFC8994] represents
[I-D.ietf-anima-autonomic-control-plane] represents a significiant a significant efficiency: in particular, it reduces the need to put
efficiency: in particular it reduces the need to put senior experts senior experts on airplanes to configure devices in person.
on airplanes to configure devices in person.
There is a recognition as the technology evolves that not every As the technology evolves, there is recognition that not every
situation may work out, and occasionally a human may still have to situation may work out, and occasionally a human may still have to
visit. In recognition of this, some mechanisms are presented in visit. Given this, some mechanisms are presented in Section 7.2.
Section 7.2. The manufacturer MUST provide at least one of the one- The manufacturer MUST provide at least one of the one-touch
touch mechanisms described that permit enrollment to be proceed mechanisms described that permit enrollment to proceed without the
without availability of any manufacturer server (such as the MASA). availability of any manufacturer server (such as the MASA).
The BRSKI protocol is going into environments where there have The BRSKI protocol is going into environments where there have
already been quite a number of vendor proprietary management systems. already been quite a number of vendor proprietary management systems.
Those are not expected to go away quickly, but rather to leverage the Those are not expected to go away quickly but rather to leverage the
secure credentials that are provisioned by BRSKI. The connectivity secure credentials that are provisioned by BRSKI. The connectivity
requirements of said management systems are provided by the ACP. requirements of the said management systems are provided by the ACP.
9.1. Operational Requirements 9.1. Operational Requirements
This section collects operational requirements based upon the three This section collects operational requirements based upon the three
roles involved in BRSKI: The Manufacturer Authorized Signing roles involved in BRSKI: the MASA, the (domain) owner, and the
Authority (MASA), the (Domain) Owner and the Device. It should be device. It should be recognized that the manufacturer may be
recognized that the manufacturer may be involved in two roles, as it involved in two roles, as it creates the software/firmware for the
creates the software/firmware for the device, and also may be the device and may also be the operator of the MASA.
operator of the MASA.
The requirements in this section are presented using BCP14 The requirements in this section are presented using BCP 14 language
([RFC2119], [RFC8174]) language. These do not represent new [RFC2119] [RFC8174]. These do not represent new normative
normative statements, just a review of a few such things in one place statements, just a review of a few such things in one place by role.
by role. They also apply specifically to the ANIMA ACP use case. They also apply specifically to the ANIMA ACP use case. Other use
Other use cases likely have similar, but MAY have different cases likely have similar, but MAY have different, requirements.
requirements.
9.1.1. MASA Operational Requirements 9.1.1. MASA Operational Requirements
The manufacturer MUST arrange for an online service to be available The manufacturer MUST arrange for an online service called the MASA
called the MASA. It MUST be available at the URL which is encoded in to be available. It MUST be available at the URL that is encoded in
the IDevID certificate extensions described in Section 2.3.2. the IDevID certificate extensions described in Section 2.3.2.
The online service MUST have access to a private key with which to The online service MUST have access to a private key with which to
sign [RFC8366] format voucher artifacts. The public key, sign voucher artifacts [RFC8366]. The public key, certificate, or
certificate, or certificate chain MUST be built in to the device as certificate chain MUST be built into the device as part of the
part of the firmware. firmware.
It is RECOMMENDED that the manufacturer arrange for this signing key It is RECOMMENDED that the manufacturer arrange for this signing key
(or keys) to be escrowed according to typical software source code (or keys) to be escrowed according to typical software source code
escrow practices [softwareescrow]. escrow practices [softwareescrow].
The MASA accepts voucher requests from Domain Owners according to an The MASA accepts voucher-requests from domain owners according to an
operational practice appropriate for the device. This can range from operational practice appropriate for the device. This can range from
any domain owner (first-come first-served, on a TOFU-like basis), to any domain owner (first-come first-served, on a TOFU-like basis), to
full sales channel integration where Domain Owners need to be full sales channel integration where domain owners need to be
positively identified by TLS Client Certicate pinned, or HTTP positively identified by TLS pinned Client Certificates or an HTTP
Authentication process. The MASA creates signed voucher artifacts authentication process. The MASA creates signed voucher artifacts
according to its internally defined policies. according to its internally defined policies.
The MASA MUST operate an audit log for devices that is accessible. The MASA MUST operate an audit-log for devices that is accessible.
The audit log is designed to be easily cacheable and the MASA MAY The audit-log is designed to be easily cacheable, and the MASA MAY
find it useful to put this content on a CDN. find it useful to put this content on a Content Delivery Network
(CDN).
9.1.2. Domain Owner Operational Requirements 9.1.2. Domain Owner Operational Requirements
The domain owner MUST operate an EST ([RFC7030]) server with the The domain owner MUST operate an EST [RFC7030] server with the
extensions described in this document. This is the JRC or Registrar. extensions described in this document. This is the JRC or registrar.
This JRC/EST server MUST announce itself using GRASP within the ACP. This JRC/EST server MUST announce itself using GRASP within the ACP.
This EST server will typically reside with the Network Operations This EST server will typically reside with the Network Operations
Center for the organization. Center for the organization.
The domain owner MAY operate an internal certificate authority (CA) The domain owner MAY operate an internal CA that is separate from the
that is seperate from the EST server, or it MAY combine all EST server, or it MAY combine all activities into a single device.
activities into a single device. The determination of the The determination of the architecture depends upon the scale and
architecture depends upon the scale and resiliency requirements of resiliency requirements of the organization. Multiple JRC instances
the organization. Multiple JRC instances MAY be announced into the MAY be announced into the ACP from multiple locations to achieve an
ACP from multiple locations to achieve an appropriate level of appropriate level of redundancy.
redundancy.
In order to recognize which devices and which manufacturers are In order to recognize which devices and which manufacturers are
welcome on the domain owner's network, the domain owner SHOULD welcome on the domain owner's network, the domain owner SHOULD
maintain a white list of manufacturers. This MAY extend to maintain an acceptlist of manufacturers. This MAY extend to
integration with purchasing departments to know the serial numbers of integration with purchasing departments to know the serial numbers of
devices. devices.
The domain owner SHOULD use the resulting overlay ACP network to The domain owner SHOULD use the resulting overlay ACP network to
manage devices, replacing legacy out-of-band mechanisms. manage devices, replacing legacy out-of-band mechanisms.
The domain owner SHOULD operate one or more EST servers which can be The domain owner SHOULD operate one or more EST servers that can be
used to renew the domain certificates (LDevIDs) which are deployed to used to renew the domain certificates (LDevIDs), which are deployed
devices. These servers MAY be the same as the JRC, or MAY be a to devices. These servers MAY be the same as the JRC or MAY be a
distinct set of devices, as approriate for resiliency. distinct set of devices, as appropriate for resiliency.
The organization MUST take appropriate precautions against loss of The organization MUST take appropriate precautions against loss of
access to the certificate authority private key. Hardware security access to the CA private key. Hardware security modules and/or
modules and/or secret splitting are appropriate. secret splitting are appropriate.
9.1.3. Device Operational Requirements 9.1.3. Device Operational Requirements
Devices MUST come with built-in trust anchors that permit the device Devices MUST come with built-in trust anchors that permit the device
to validate vouchers from the MASA. to validate vouchers from the MASA.
Device MUST come with (unique, per-device) IDevID certificates that Devices MUST come with (unique, per-device) IDevID certificates that
include their serial numbers, and the MASA URL extension. include their serial numbers and the MASA URL extension.
Devices are expected to find Join Proxies using GRASP, and then Devices are expected to find Join Proxies using GRASP, and then
connect to the JRC using the protocol described in this document. connect to the JRC using the protocol described in this document.
Once a domain owner has been validated with the voucher, devices are Once a domain owner has been validated with the voucher, devices are
expected to enroll into the domain using EST. Devices are then expected to enroll into the domain using EST. Devices are then
expected to form ACPs using IPsec over IPv6 Link-Local addresses as expected to form ACPs using IPsec over IPv6 link-local addresses as
described in [I-D.ietf-anima-autonomic-control-plane]. described in [RFC8994].
Once a device has been enrolled it SHOULD listen for the address of Once a device has been enrolled, it SHOULD listen for the address of
the JRC using GRASP, and it SHOULD enable itself as a Join Proxy, and the JRC using GRASP, and it SHOULD enable itself as a Join Proxy and
announce itself on all links/interfaces using GRASP DULL. announce itself on all links/interfaces using GRASP DULL.
Devices are expected to renew their certificates before they expire. Devices are expected to renew their certificates before they expire.
10. Privacy Considerations 10. Privacy Considerations
10.1. MASA audit log 10.1. MASA Audit-Log
The MASA audit log includes the domainID for each domain a voucher The MASA audit-log includes the domainID for each domain a voucher
has been issued to. This information is closely related to the has been issued to. This information is closely related to the
actual domain identity. A MASA may need additional defenses against actual domain identity. A MASA may need additional defenses against
Denial of Service attacks (Section 11.1), and this may involve Denial-of-Service attacks (Section 11.1), and this may involve
collecting additional (unspecified here) information. This could collecting additional (unspecified here) information. This could
provide sufficient information for the MASA service to build a provide sufficient information for the MASA service to build a
detailed understanding the devices that have been provisioned within detailed understanding of the devices that have been provisioned
a domain. within a domain.
There are a number of design choices that mitigate this risk. The There are a number of design choices that mitigate this risk. The
domain can maintain some privacy since it has not necessarily been domain can maintain some privacy since it has not necessarily been
authenticated and is not authoritatively bound to the supply chain. authenticated and is not authoritatively bound to the supply chain.
Additionally the domainID captures only the unauthenticated subject Additionally, the domainID captures only the unauthenticated subject
key identifier of the domain. A privacy sensitive domain could key identifier of the domain. A privacy-sensitive domain could
theoretically generate a new domainID for each device being deployed. theoretically generate a new domainID for each device being deployed.
Similarly a privacy sensitive domain would likely purchase devices Similarly, a privacy-sensitive domain would likely purchase devices
that support proximity assertions from a manufacturer that does not that support proximity assertions from a manufacturer that does not
require sales channel integrations. This would result in a require sales channel integrations. This would result in a
significant level of privacy while maintaining the security significant level of privacy while maintaining the security
characteristics provided by Registrar based audit log inspection. characteristics provided by the registrar-based audit-log inspection.
10.2. What BRSKI-EST reveals 10.2. What BRSKI-EST Reveals
During the provisional phase of the BRSKI-EST connection between the During the provisional phase of the BRSKI-EST connection between the
Pledge and the Registrar, each party reveals its certificates to each pledge and the registrar, each party reveals its certificates to each
other. For the Pledge, this includes the serialNumber attribute, the other. For the pledge, this includes the serialNumber attribute, the
MASA URL, and the identity that signed the IDevID certificate. MASA URL, and the identity that signed the IDevID certificate.
TLS 1.2 reveals the certificate identities to on-path observers, TLS 1.2 reveals the certificate identities to on-path observers,
including the Join Proxy. including the Join Proxy.
TLS 1.3 reveals the certificate identities only to the end parties, TLS 1.3 reveals the certificate identities only to the end parties,
but as the connection is provisional, an on-path attacker (MTIM) can but as the connection is provisional; an on-path attacker (MITM) can
see the certificates. This includes not just malicious attackers, see the certificates. This includes not just malicious attackers but
but also Registrars that are visible to the Pledge, but which are not also registrars that are visible to the pledge but are not part of
part of the intended domain. the intended domain.
The certificate of the Registrar is rather arbitrary from the point The certificate of the registrar is rather arbitrary from the point
of view of the BRSKI protocol. As no [RFC6125] validations are of view of the BRSKI protocol. As no validations [RFC6125] are
expected to be done, the contents could be easily pseudonymized. Any expected to be done, the contents could be easily pseudonymized. Any
device that can see a join proxy would be able to connect to the device that can see a Join Proxy would be able to connect to the
Registrar and learn the identity of the network in question. Even if registrar and learn the identity of the network in question. Even if
the contents of the certificate are pseudonymized, it would be the contents of the certificate are pseudonymized, it would be
possible to correlate different connections in different locations possible to correlate different connections in different locations
belong to the same entity. This is unlikely to present a significant that belong to the same entity. This is unlikely to present a
privacy concern to ANIMA ACP uses of BRSKI, but may be a concern to significant privacy concern to ANIMA ACP uses of BRSKI, but it may be
other users of BRSKI. a concern to other users of BRSKI.
The certificate of the Pledge could be revealed by a malicious Join The certificate of the pledge could be revealed by a malicious Join
Proxy that performed a MITM attack on the provisional TLS connection. Proxy that performed a MITM attack on the provisional TLS connection.
Such an attacker would be able to reveal the identity of the Pledge Such an attacker would be able to reveal the identity of the pledge
to third parties if it chose to so. to third parties if it chose to do so.
Research into a mechanism to do multi-step, multi-party authenticated Research into a mechanism to do multistep, multiparty authenticated
key agreement, incorporating some kind of zero-knowledge proof would key agreement, incorporating some kind of zero-knowledge proof, would
be valuable. Such a mechanism would ideally avoid disclosing be valuable. Such a mechanism would ideally avoid disclosing
identities until pledge, registrar and MASA agree to the transaction. identities until the pledge, registrar, and MASA agree to the
Such a mechanism would need to discover the location of the MASA transaction. Such a mechanism would need to discover the location of
without knowing the identity of the pledge, or the identity of the the MASA without knowing the identity of the pledge or the identity
MASA. This part of the problem may be unsolveable. of the MASA. This part of the problem may be unsolvable.
10.3. What BRSKI-MASA reveals to the manufacturer 10.3. What BRSKI-MASA Reveals to the Manufacturer
With consumer-oriented devices, the "call-home" mechanism in IoT With consumer-oriented devices, the "call-home" mechanism in IoT
devices raises significant privacy concerns. See [livingwithIoT] and devices raises significant privacy concerns. See [livingwithIoT] and
[IoTstrangeThings] for exemplars. The Autonomic Control Plane (ACP) [IoTstrangeThings] for exemplars. The ACP usage of BRSKI is not
usage of BRSKI is not targeted at individual usage of IoT devices, targeted at individual usage of IoT devices but rather at the
but rather at the Enterprise and ISP creation of networks in a zero- enterprise and ISP creation of networks in a zero-touch fashion where
touch fashion where the "call-home" represents a different class of the "call-home" represents a different class of privacy and life-
privacy and lifecycle management concerns. cycle management concerns.
It needs to be re-iterated that the BRSKI-MASA mechanism only occurs It needs to be reiterated that the BRSKI-MASA mechanism only occurs
once during the commissioning of the device. It is well defined, and once during the commissioning of the device. It is well defined, and
although encrypted with TLS, it could in theory be made auditable as although encrypted with TLS, it could in theory be made auditable as
the contents are well defined. This connection does not occur when the contents are well defined. This connection does not occur when
the device powers on or is restarted for normal routines. (It is the device powers on or is restarted for normal routines. (It is
conceivable, but remarkably unusual, that a device could be forced to conceivable, but remarkably unusual, that a device could be forced to
go through a full factory reset during an exceptional firmware update go through a full factory reset during an exceptional firmware update
situation, after which enrollment would have be repeated, and a new situation, after which enrollment would have to be repeated, and a
connection would occur) new connection would occur.)
The BRSKI call-home mechanism is mediated via the owner's Registrar, The BRSKI call-home mechanism is mediated via the owner's registrar,
and the information that is transmitted is directly auditable by the and the information that is transmitted is directly auditable by the
device owner. This is in stark contrast to many "call-home" device owner. This is in stark contrast to many "call-home"
protocols where the device autonomously calls home and uses an protocols where the device autonomously calls home and uses an
undocumented protocol. undocumented protocol.
While the contents of the signed part of the pledge voucher request While the contents of the signed part of the pledge voucher-request
can not be changed, they are not encrypted at the registrar. The cannot be changed, they are not encrypted at the registrar. The
ability to audit the messages by the owner of the network is a ability to audit the messages by the owner of the network is a
mechanism to defend against exfiltration of data by a nefarious mechanism to defend against exfiltration of data by a nefarious
pledge. Both are, to re-iterate, encrypted by TLS while in transit. pledge. Both are, to reiterate, encrypted by TLS while in transit.
The BRSKI-MASA exchange reveals the following information to the The BRSKI-MASA exchange reveals the following information to the
manufacturer: manufacturer:
* the identity of the device being enrolled. This is revealed by * the identity of the device being enrolled. This is revealed by
transmission of a signed voucher-request containing the serial- transmission of a signed voucher-request containing the serial-
number. The manufacturer can usually link the serial number to a number. The manufacturer can usually link the serial number to a
device model. device model.
* an identity of the domain owner in the form of the domain trust * an identity of the domain owner in the form of the domain trust
anchor. However, this is not a global PKI anchored name within anchor. However, this is not a global PKI-anchored name within
the WebPKI, so this identity could be pseudonymous. If there is the WebPKI, so this identity could be pseudonymous. If there is
sales channel integration, then the MASA will have authenticated sales channel integration, then the MASA will have authenticated
the domain owner, either via pinned certificate, or perhaps the domain owner, via either a pinned certificate or perhaps
another HTTP authentication method, as per Section 5.5.4. another HTTP authentication method, as per Section 5.5.4.
* the time the device is activated, * the time the device is activated.
* the IP address of the domain Owner's Registrar. For ISPs and * the IP address of the domain owner's registrar. For ISPs and
Enterprises, the IP address provides very clear geolocation of the enterprises, the IP address provides very clear geolocation of the
owner. No amount of IP address privacy extensions ([RFC4941]) can owner. No amount of IP address privacy extensions [RFC8981] can
do anything about this, as a simple whois lookup likely identifies do anything about this, as a simple whois lookup likely identifies
the ISP or Enterprise from the upper bits anyway. A passive the ISP or enterprise from the upper bits anyway. A passive
attacker who observes the connection definitely may conclude that attacker who observes the connection definitely may conclude that
the given enterprise/ISP is a customer of the particular equipment the given enterprise/ISP is a customer of the particular equipment
vendor. The precise model that is being enrolled will remain vendor. The precise model that is being enrolled will remain
private. private.
Based upon the above information, the manufacturer is able to track a Based upon the above information, the manufacturer is able to track a
specific device from pseudonymous domain identity to the next specific device from pseudonymous domain identity to the next
pseudonymous domain identity. If there is sales-channel integration, pseudonymous domain identity. If there is sales-channel integration,
then the identities are not pseudonymous. then the identities are not pseudonymous.
The manufacturer knows the IP address of the Registrar, but it can The manufacturer knows the IP address of the registrar, but it cannot
not see the IP address of the device itself. The manufacturer can see the IP address of the device itself. The manufacturer cannot
not track the device to a detailed physical or network location, only track the device to a detailed physical or network location, only to
to the location of the Registrar. That is likely to be at the the location of the registrar. That is likely to be at the
Enterprise or ISPs headquarters. enterprise or ISP's headquarters.
The above situation is to be distinguished from a residential/ The above situation is to be distinguished from a residential/
individual person who registers a device from a manufacturer. individual person who registers a device from a manufacturer.
Individuals do not tend to have multiple offices, and their registrar Individuals do not tend to have multiple offices, and their registrar
is likely on the same network as the device. A manufacturer that is likely on the same network as the device. A manufacturer that
sells switching/routing products to enterprises should hardly be sells switching/routing products to enterprises should hardly be
surprised if additional purchases switching/routing products are surprised if additional purchases of switching/routing products are
made. Deviations from a historical trend or an establish baseline made. Deviations from a historical trend or an established baseline
would, however, be notable. would, however, be notable.
The situation is not improved by the enterprise/ISP using The situation is not improved by the enterprise/ISP using
anonymization services such as ToR [Dingledine2004], as a TLS 1.2 anonymization services such as Tor [Dingledine], as a TLS 1.2
connection will reveal the ClientCertificate used, clearly connection will reveal the ClientCertificate used, clearly
identifying the enterprise/ISP involved. TLS 1.3 is better in this identifying the enterprise/ISP involved. TLS 1.3 is better in this
regard, but an active attacker can still discover the parties regard, but an active attacker can still discover the parties
involved by performing a Man-In-The-Middle-Attack on the first involved by performing a MITM attack on the first attempt (breaking/
attempt (breaking/killing it with a TCP RST), and then letting killing it with a TCP reset (RST)), and then letting subsequent
subsequent connection pass through. connection pass through.
A manufacturer could attempt to mix the BRSKI-MASA traffic in with A manufacturer could attempt to mix the BRSKI-MASA traffic in with
general traffic their site by hosting the MASA behind the same (set) general traffic on their site by hosting the MASA behind the same
of load balancers that the companies normal marketing site is hosted (set) of load balancers that the company's normal marketing site is
behind. This makes lots of sense from a straight capacity planning hosted behind. This makes a lot of sense from a straight capacity
point of view as the same set of services (and the same set of planning point of view as the same set of services (and the same set
Distributed Denial of Service mitigations) may be used. of Distributed Denial-of-Service mitigations) may be used.
Unfortunately, as the BRSKI-MASA connections include TLS Unfortunately, as the BRSKI-MASA connections include TLS
ClientCertificate exchanges, this may easily be observed in TLS 1.2, ClientCertificate exchanges, this may easily be observed in TLS 1.2,
and a traffic analysis may reveal it even in TLS 1.3. This does not and a traffic analysis may reveal it even in TLS 1.3. This does not
make such a plan irrelevant. There may be other organizational make such a plan irrelevant. There may be other organizational
reasons to keep the marketing site (which is often subject to reasons to keep the marketing site (which is often subject to
frequent re-designs, outsourcing, etc.) separate from the MASA, which frequent redesigns, outsourcing, etc.) separate from the MASA, which
may need to operate reliably for decades. may need to operate reliably for decades.
10.4. Manufacturers and Used or Stolen Equipment 10.4. Manufacturers and Used or Stolen Equipment
As explained above, the manufacturer receives information each time As explained above, the manufacturer receives information each time a
that a device which is in factory-default mode does a zero-touch device that is in factory-default mode does a zero-touch bootstrap
bootstrap, and attempts to enroll into a domain owner's registrar. and attempts to enroll into a domain owner's registrar.
The manufacturer is therefore in a position to decline to issue a The manufacturer is therefore in a position to decline to issue a
voucher if it detects that the new owner is not the same as the voucher if it detects that the new owner is not the same as the
previous owner. previous owner.
1. This can be seen as a feature if the equipment is believed to 1. This can be seen as a feature if the equipment is believed to
have been stolen. If the legitimate owner notifies the have been stolen. If the legitimate owner notifies the
manufacturer of the theft, then when the new owner brings the manufacturer of the theft, then when the new owner brings the
device up, if they use the zero-touch mechanism, the new device up, if they use the zero-touch mechanism, the new
(illegitimate) owner reveals their location and identity. (illegitimate) owner reveals their location and identity.
2. In the case of Used equipment, the initial owner could inform the 2. In the case of used equipment, the initial owner could inform the
manufacturer of the sale, or the manufacturer may just permit manufacturer of the sale, or the manufacturer may just permit
resales unless told otherwise. In which case, the transfer of resales unless told otherwise. In which case, the transfer of
ownership simply occurs. ownership simply occurs.
3. A manufacturer could however decide not to issue a new voucher in 3. A manufacturer could, however, decide not to issue a new voucher
response to a transfer of ownership. This is essentially the in response to a transfer of ownership. This is essentially the
same as the stolen case, with the manufacturer having decided same as the stolen case, with the manufacturer having decided
that the sale was not legitimate. that the sale was not legitimate.
4. There is a fourth case, if the manufacturer is providing 4. There is a fourth case, if the manufacturer is providing
protection against stolen devices. The manufacturer then has a protection against stolen devices. The manufacturer then has a
responsibility to protect the legitimate owner against fraudulent responsibility to protect the legitimate owner against fraudulent
claims that the equipment was stolen. In the absence of such claims that the equipment was stolen. In the absence of such
manufacturer protection, such a claim would cause the manufacturer protection, such a claim would cause the
manufacturer to refuse to issue a new voucher. Should the device manufacturer to refuse to issue a new voucher. Should the device
go through a deep factory reset (for instance, replacement of a go through a deep factory reset (for instance, replacement of a
damaged main board component, the device would not bootstrap. damaged main board component), the device would not bootstrap.
5. Finally, there is a fifth case: the manufacturer has decided to 5. Finally, there is a fifth case: the manufacturer has decided to
end-of-line the device, or the owner has not paid a yearly end-of-line the device, or the owner has not paid a yearly
support amount, and the manufacturer refuses to issue new support amount, and the manufacturer refuses to issue new
vouchers at that point. This last case is not new to the vouchers at that point. This last case is not new to the
industry: many license systems are already deployed that have industry: many license systems are already deployed that have a
significantly worse effect. significantly worse effect.
This section has outlined five situations in which a manufacturer This section has outlined five situations in which a manufacturer
could use the voucher system to enforce what are clearly license could use the voucher system to enforce what are clearly license
terms. A manufacturer that attempted to enforce license terms via terms. A manufacturer that attempted to enforce license terms via
vouchers would find it rather ineffective as the terms would only be vouchers would find it rather ineffective as the terms would only be
enforced when the device is enrolled, and this is not (to repeat), a enforced when the device is enrolled, and this is not (to repeat) a
daily or even monthly occurrence. daily or even monthly occurrence.
10.5. Manufacturers and Grey market equipment 10.5. Manufacturers and Grey Market Equipment
Manufacturers of devices often sell different products into different Manufacturers of devices often sell different products into different
regional markets. Which product is available in which market can be regional markets. Which product is available in which market can be
driven by price differentials, support issues (some markets may driven by price differentials, support issues (some markets may
require manuals and tech-support to be done in the local language), require manuals and tech support to be done in the local language),
government export regulation (such as whether strong crypto is and government export regulation (such as whether strong crypto is
permitted to be exported, or permitted to be used in a particular permitted to be exported or permitted to be used in a particular
market). When an domain owner obtains a device from a different market). When a domain owner obtains a device from a different
market (they can be new) and transfers it to a different location, market (they can be new) and transfers it to a different location,
this is called a Grey Market. this is called a Grey Market.
A manufacturer could decide not to issue a voucher to an enterprise/ A manufacturer could decide not to issue a voucher to an enterprise/
ISP based upon their location. There are a number of ways which this ISP based upon their location. There are a number of ways that this
could be determined: from the geolocation of the registrar, from could be determined: from the geolocation of the registrar, from
sales channel knowledge about the customer, and what products are sales channel knowledge about the customer, and from what products
(un-)available in that market. If the device has a GPS the are available or unavailable in that market. If the device has a
coordinates of the device could even be placed into an extension of GPS, the coordinates of the device could even be placed into an
the voucher. extension of the voucher.
The above actions are not illegal, and not new. Many manufacturers The above actions are not illegal, and not new. Many manufacturers
have shipped crypto-weak (exportable) versions of firmware as the have shipped crypto-weak (exportable) versions of firmware as the
default on equipment for decades. The first task of an enterprise/ default on equipment for decades. The first task of an enterprise/
ISP has always been to login to a manufacturer system, show one's ISP has always been to login to a manufacturer system, show one's
"entitlement" (country information, proof that support payments have "entitlement" (country information, proof that support payments have
been made), and receive either a new updated firmware, or a license been made), and receive either a new updated firmware or a license
key that will activate the correct firmware. key that will activate the correct firmware.
BRSKI permits the above process to automated (in an autonomic BRSKI permits the above process to be automated (in an autonomic
fashion), and therefore perhaps encourages this kind of fashion) and therefore perhaps encourages this kind of
differentiation by reducing the cost of doing it. differentiation by reducing the cost of doing it.
An issue that manufacturers will need to deal with in the above An issue that manufacturers will need to deal with in the above
automated process is when a device is shipped to one country with one automated process is when a device is shipped to one country with one
set of rules (or laws or entitlements), but the domain registry is in set of rules (or laws or entitlements), but the domain registry is in
another one. Which rules apply is something will have to be worked another one. Which rules apply is something that will have to be
out: the manufacturer could come to believe they are dealing with worked out: the manufacturer could believe they are dealing with Grey
Grey market equipment, when it is simply dealing with a global Market equipment when they are simply dealing with a global
enterprise. enterprise.
10.6. Some mitigations for meddling by manufacturers 10.6. Some Mitigations for Meddling by Manufacturers
The most obvious mitigation is not to buy the product. Pick The most obvious mitigation is not to buy the product. Pick
manufacturers that are up-front about their policies, who do not manufacturers that are up front about their policies and who do not
change them gratuitously. change them gratuitously.
Section 7.4.3 describes some ways in which a manufacturer could Section 7.4.3 describes some ways in which a manufacturer could
provide a mechanism to manage the trust anchors and built-in provide a mechanism to manage the trust anchors and built-in
certificates (IDevID) as an extension. There are a variety of certificates (IDevID) as an extension. There are a variety of
mechanism, and some may take a substantial amount of work to get mechanisms, and some may take a substantial amount of work to get
exactly correct. These mechanisms do not change the flow of the exactly correct. These mechanisms do not change the flow of the
protocol described here, but rather allow the starting trust protocol described here but rather allow the starting trust
assumptions to be changed. This is an area for future assumptions to be changed. This is an area for future
standardization work. standardization work.
Replacement of the voucher validation anchors (usually pointing to Replacement of the voucher validation anchors (usually pointing to
the original manufacturer's MASA) with those of the new owner permits the original manufacturer's MASA) with those of the new owner permits
the new owner to issue vouchers to subsequent owners. This would be the new owner to issue vouchers to subsequent owners. This would be
done by having the selling (old) owner to run a MASA. done by having the selling (old) owner run a MASA.
The BRSKI protocol depends upon a trust anchor on the device and an The BRSKI protocol depends upon a trust anchor and an identity on the
identity on the device. Management of these entities facilitates a device. Management of these entities facilitates a few new
few new operational modes without making any changes to the BRSKI operational modes without making any changes to the BRSKI protocol.
protocol. Those modes include: offline modes where the domain owner Those modes include: offline modes where the domain owner operates an
operates an internal MASA for all devices, resell modes where the internal MASA for all devices, resell modes where the first domain
first domain owner becomes the MASA for the next (resold-to) domain owner becomes the MASA for the next (resold-to) domain owner, and
owner, and services where an aggregator acquires a large variety of services where an aggregator acquires a large variety of devices and
devices, and then acts as a pseudonymized MASA for a variety of then acts as a pseudonymized MASA for a variety of devices from a
devices from a variety of manufacturers. variety of manufacturers.
Although replacement of the IDevID is not required for all modes Although replacement of the IDevID is not required for all modes
described above, a manufacturers could support such a thing. Some described above, a manufacturer could support such a thing. Some may
may wish to consider replacement of the IDevID as an indication that wish to consider replacement of the IDevID as an indication that the
the device's warrantee is terminated. For others, the privacy device's warranty is terminated. For others, the privacy
requirements of some deployments might consider this a standard requirements of some deployments might consider this a standard
operating practice. operating practice.
As discussed at the end of Section 5.8.1, new work could be done to As discussed at the end of Section 5.8.1, new work could be done to
use a distributed consensus technology for the audit log. This would use a distributed consensus technology for the audit-log. This would
permit the audit log to continue to be useful, even when there is a permit the audit-log to continue to be useful, even when there is a
chain of MASA due to changes of ownership. chain of MASA due to changes of ownership.
10.7. Death of a manufacturer 10.7. Death of a Manufacturer
A common concern has been that a manufacturer could go out of A common concern has been that a manufacturer could go out of
business, leaving owners of devices unable to get new vouchers for business, leaving owners of devices unable to get new vouchers for
existing products. Said products might have been previously existing products. Said products might have been previously deployed
deployed, but need to be re-initialized, they might have been but need to be reinitialized, used, or kept in a warehouse as long-
purchased used, or they might have kept in a warehouse as long-term term spares.
spares.
The MASA was named the Manufacturer *Authorized* Signing Authority to The MASA was named the Manufacturer *Authorized* Signing Authority to
emphasize that it need not be the manufacturer itself that performs emphasize that it need not be the manufacturer itself that performs
this. It is anticipated that specialist service providers will come this. It is anticipated that specialist service providers will come
to exist that deal with the creation of vouchers in much the same way to exist that deal with the creation of vouchers in much the same way
that many companies have outsourced email, advertising and janitorial that many companies have outsourced email, advertising, and
services. janitorial services.
Further, it is expected that as part of any service agreement that Further, it is expected that as part of any service agreement, the
the manufacturer would arrange to escrow appropriate private keys manufacturer would arrange to escrow appropriate private keys such
such that a MASA service could be provided by a third party. This that a MASA service could be provided by a third party. This has
has routinely been done for source code for decades. routinely been done for source code for decades.
11. Security Considerations 11. Security Considerations
This document details a protocol for bootstrapping that balances This document details a protocol for bootstrapping that balances
operational concerns against security concerns. As detailed in the operational concerns against security concerns. As detailed in the
introduction, and touched on again in Section 7, the protocol allows introduction, and touched on again in Section 7, the protocol allows
for reduced security modes. These attempt to deliver additional for reduced security modes. These attempt to deliver additional
control to the local administrator and owner in cases where less control to the local administrator and owner in cases where less
security provides operational benefits. This section goes into more security provides operational benefits. This section goes into more
detail about a variety of specific considerations. detail about a variety of specific considerations.
To facilitate logging and administrative oversight, in addition to To facilitate logging and administrative oversight, in addition to
triggering Registrar verification of MASA logs, the pledge reports on triggering registrar verification of MASA logs, the pledge reports on
voucher parsing status to the registrar. In the case of a failure, the voucher parsing status to the registrar. In the case of a
this information is informative to a potentially malicious registrar. failure, this information is informative to a potentially malicious
This is mandated anyway because of the operational benefits of an registrar. This is mandated anyway because of the operational
informed administrator in cases where the failure is indicative of a benefits of an informed administrator in cases where the failure is
problem. The registrar is RECOMMENDED to verify MASA logs if voucher indicative of a problem. The registrar is RECOMMENDED to verify MASA
status telemetry is not received. logs if voucher status telemetry is not received.
To facilitate truly limited clients EST RFC7030 section 3.3.2 To facilitate truly limited clients, EST requires that the client
requirements that the client MUST support a client authentication MUST support a client authentication model (see [RFC7030],
model have been reduced in Section 7 to a statement that the Section 3.3.2); Section 7 updates these requirements by stating that
registrar "MAY" choose to accept devices that fail cryptographic the registrar MAY choose to accept devices that fail cryptographic
authentication. This reflects current (poor) practices in shipping authentication. This reflects current (poor) practices in shipping
devices without a cryptographic identity that are NOT RECOMMENDED. devices without a cryptographic identity that are NOT RECOMMENDED.
During the provisional period of the connection the pledge MUST treat During the provisional period of the connection, the pledge MUST
all HTTP header and content data as untrusted data. HTTP libraries treat all HTTP header and content data as untrusted data. HTTP
are regularly exposed to non-secured HTTP traffic: mature libraries libraries are regularly exposed to non-secured HTTP traffic: mature
should not have any problems. libraries should not have any problems.
Pledges might chose to engage in protocol operations with multiple Pledges might chose to engage in protocol operations with multiple
discovered registrars in parallel. As noted above they will only do discovered registrars in parallel. As noted above, they will only do
so with distinct nonce values, but the end result could be multiple so with distinct nonce values, but the end result could be multiple
vouchers issued from the MASA if all registrars attempt to claim the vouchers issued from the MASA if all registrars attempt to claim the
device. This is not a failure and the pledge choses whichever device. This is not a failure, and the pledge chooses whichever
voucher to accept based on internal logic. The registrars verifying voucher to accept based on internal logic. The registrars verifying
log information will see multiple entries and take this into account log information will see multiple entries and take this into account
for their analytics purposes. for their analytic purposes.
11.1. Denial of Service (DoS) against MASA 11.1. Denial of Service (DoS) against MASA
There are uses cases where the MASA could be unavailable or There are use cases where the MASA could be unavailable or
uncooperative to the Registrar. They include active DoS attacks, uncooperative to the registrar. They include active DoS attacks,
planned and unplanned network partitions, changes to MASA policy, or planned and unplanned network partitions, changes to MASA policy, or
other instances where MASA policy rejects a claim. These introduce other instances where MASA policy rejects a claim. These introduce
an operational risk to the Registrar owner in that MASA behavior an operational risk to the registrar owner in that MASA behavior
might limit the ability to bootstrap a pledge device. For example might limit the ability to bootstrap a pledge device. For example,
this might be an issue during disaster recovery. This risk can be this might be an issue during disaster recovery. This risk can be
mitigated by Registrars that request and maintain long term copies of mitigated by registrars that request and maintain long-term copies of
"nonceless" vouchers. In that way they are guaranteed to be able to "nonceless" vouchers. In that way, they are guaranteed to be able to
bootstrap their devices. bootstrap their devices.
The issuance of nonceless vouchers themselves creates a security The issuance of nonceless vouchers themselves creates a security
concern. If the Registrar of a previous domain can intercept concern. If the registrar of a previous domain can intercept
protocol communications then it can use a previously issued nonceless protocol communications, then it can use a previously issued
voucher to establish management control of a pledge device even after nonceless voucher to establish management control of a pledge device
having sold it. This risk is mitigated by recording the issuance of even after having sold it. This risk is mitigated by recording the
such vouchers in the MASA audit log that is verified by the issuance of such vouchers in the MASA audit-log that is verified by
subsequent Registrar and by Pledges only bootstrapping when in a the subsequent registrar and by pledges only bootstrapping when in a
factory default state. This reflects a balance between enabling MASA factory default state. This reflects a balance between enabling MASA
independence during future bootstrapping and the security of independence during future bootstrapping and the security of
bootstrapping itself. Registrar control over requesting and auditing bootstrapping itself. Registrar control over requesting and auditing
nonceless vouchers allows device owners to choose an appropriate nonceless vouchers allows device owners to choose an appropriate
balance. balance.
The MASA is exposed to DoS attacks wherein attackers claim an The MASA is exposed to DoS attacks wherein attackers claim an
unbounded number of devices. Ensuring a registrar is representative unbounded number of devices. Ensuring a registrar is representative
of a valid manufacturer customer, even without validating ownership of a valid manufacturer customer, even without validating ownership
of specific pledge devices, helps to mitigate this. Pledge of specific pledge devices, helps to mitigate this. Pledge
signatures on the pledge voucher-request, as forwarded by the signatures on the pledge voucher-request, as forwarded by the
registrar in the prior-signed-voucher-request field of the registrar registrar in the prior-signed-voucher-request field of the registrar
voucher-request, significantly reduce this risk by ensuring the MASA voucher-request, significantly reduce this risk by ensuring the MASA
can confirm proximity between the pledge and the registrar making the can confirm proximity between the pledge and the registrar making the
request. Supply chain integration ("know your customer") is an request. Supply-chain integration ("know your customer") is an
additional step that MASA providers and device vendors can explore. additional step that MASA providers and device vendors can explore.
11.2. DomainID must be resistant to second-preimage attacks 11.2. DomainID Must Be Resistant to Second-Preimage Attacks
The domainID is used as the reference in the audit log to the domain. The domainID is used as the reference in the audit-log to the domain.
The domainID is expected to be calculated by a hash that is resistant The domainID is expected to be calculated by a hash that is resistant
to a second-preimage attack. Such an attack would allow a second to a second-preimage attack. Such an attack would allow a second
registrar to create audit log entries that are fake. registrar to create audit-log entries that are fake.
11.3. Availability of good random numbers 11.3. Availability of Good Random Numbers
The nonce used by the Pledge in the voucher-request SHOULD be The nonce used by the pledge in the voucher-request SHOULD be
generated by a Strong Cryptographic Sequence ([RFC4086] section 6.2). generated by a Strong Cryptographic Sequence ([RFC4086],
TLS has a similar requirement. Section 6.2). TLS has a similar requirement.
In particular implementations should pay attention to the advance in In particular, implementations should pay attention to the advance in
[RFC4086] section 3, particularly section 3.4. The random seed used [RFC4086]; see Sections 3 and, in particular, 3.4. The random seed
by a device at boot MUST be unique across all devices and all used by a device at boot MUST be unique across all devices and all
bootstraps. Resetting a device to factory default state does not bootstraps. Resetting a device to factory default state does not
obviate this requirement. obviate this requirement.
11.4. Freshness in Voucher-Requests 11.4. Freshness in Voucher-Requests
A concern has been raised that the pledge voucher-request should A concern has been raised that the pledge voucher-request should
contain some content (a nonce) provided by the registrar and/or MASA contain some content (a nonce) provided by the registrar and/or MASA
in order for those actors to verify that the pledge voucher-request in order for those actors to verify that the pledge voucher-request
is fresh. is fresh.
There are a number of operational problems with getting a nonce from There are a number of operational problems with getting a nonce from
the MASA to the pledge. It is somewhat easier to collect a random the MASA to the pledge. It is somewhat easier to collect a random
value from the registrar, but as the registrar is not yet vouched value from the registrar, but as the registrar is not yet vouched
for, such a registrar nonce has little value. There are privacy and for, such a registrar nonce has little value. There are privacy and
logistical challenges to addressing these operational issues, so if logistical challenges to addressing these operational issues, so if
such a thing were to be considered, it would have to provide some such a thing were to be considered, it would have to provide some
clear value. This section examines the impacts of not having a fresh clear value. This section examines the impacts of not having a fresh
pledge voucher-request. pledge voucher-request.
Because the registrar authenticates the pledge, a full Man-in-the- Because the registrar authenticates the pledge, a full MITM attack is
Middle attack is not possible, despite the provisional TLS not possible, despite the provisional TLS authentication by the
authentication by the pledge (see Section 5.) Instead we examine the pledge (see Section 5.) Instead, we examine the case of a fake
case of a fake registrar (Rm) that communicates with the pledge in registrar (Rm) that communicates with the pledge in parallel or in
parallel or in close time proximity with the intended registrar. close-time proximity with the intended registrar. (This scenario is
(This scenario is intentionally supported as described in intentionally supported as described in Section 4.1.)
Section 4.1.)
The fake registrar (Rm) can obtain a voucher signed by the MASA The fake registrar (Rm) can obtain a voucher signed by the MASA
either directly or through arbitrary intermediaries. Assuming that either directly or through arbitrary intermediaries. Assuming that
the MASA accepts the registrar voucher-request (either because Rm is the MASA accepts the registrar voucher-request (because either the Rm
collaborating with a legitimate registrar according to supply chain is collaborating with a legitimate registrar according to supply-
information, or because the MASA is in audit-log only mode), then a chain information or the MASA is in audit-log only mode), then a
voucher linking the pledge to the registrar Rm is issued. voucher linking the pledge to the registrar Rm is issued.
Such a voucher, when passed back to the pledge, would link the pledge Such a voucher, when passed back to the pledge, would link the pledge
to registrar Rm, and would permit the pledge to end the provisional to registrar Rm and permit the pledge to end the provisional state.
state. It now trusts Rm and, if it has any security vulnerabilities It now trusts the Rm and, if it has any security vulnerabilities
leveragable by an Rm with full administrative control, can be assumed leverageable by an Rm with full administrative control, can be
to be a threat against the intended registrar. assumed to be a threat against the intended registrar.
This flow is mitigated by the intended registrar verifying the audit This flow is mitigated by the intended registrar verifying the audit-
logs available from the MASA as described in Section 5.8. Rm might logs available from the MASA as described in Section 5.8. The Rm
chose to collect a voucher-request but wait until after the intended might chose to collect a voucher-request but wait until after the
registrar completes the authorization process before submitting it. intended registrar completes the authorization process before
This pledge voucher-request would be 'stale' in that it has a nonce submitting it. This pledge voucher-request would be "stale" in that
that no longer matches the internal state of the pledge. In order to it has a nonce that no longer matches the internal state of the
successfully use any resulting voucher the Rm would need to remove pledge. In order to successfully use any resulting voucher, the Rm
the stale nonce or anticipate the pledge's future nonce state. would need to remove the stale nonce or anticipate the pledge's
Reducing the possibility of this is why the pledge is mandated to future nonce state. Reducing the possibility of this is why the
generate a strong random or pseudo-random number nonce. pledge is mandated to generate a strong random or pseudo-random
number nonce.
Additionally, in order to successfully use the resulting voucher the Additionally, in order to successfully use the resulting voucher, the
Rm would have to attack the pledge and return it to a bootstrapping Rm would have to attack the pledge and return it to a bootstrapping-
enabled state. This would require wiping the pledge of current enabled state. This would require wiping the pledge of current
configuration and triggering a re-bootstrapping of the pledge. This configuration and triggering a rebootstrapping of the pledge. This
is no more likely than simply taking control of the pledge directly is no more likely than simply taking control of the pledge directly,
but if this is a consideration the target network is RECOMMENDED to but if this is a consideration, it is RECOMMENDED that the target
take the following steps: network take the following steps:
* Ongoing network monitoring for unexpected bootstrapping attempts * Ongoing network monitoring for unexpected bootstrapping attempts
by pledges. by pledges.
* Retrieval and examination of MASA log information upon the * Retrieval and examination of MASA log information upon the
occurrence of any such unexpected events. Rm will be listed in occurrence of any such unexpected events. The Rm will be listed
the logs along with nonce information for analysis. in the logs along with nonce information for analysis.
11.5. Trusting manufacturers 11.5. Trusting Manufacturers
The BRSKI extensions to EST permit a new pledge to be completely The BRSKI extensions to EST permit a new pledge to be completely
configured with domain specific trust anchors. The link from built- configured with domain-specific trust anchors. The link from built-
in manufacturer-provided trust anchors to domain-specific trust in manufacturer-provided trust anchors to domain-specific trust
anchors is mediated by the signed voucher artifact. anchors is mediated by the signed voucher artifact.
If the manufacturer's IDevID signing key is not properly validated, If the manufacturer's IDevID signing key is not properly validated,
then there is a risk that the network will accept a pledge that then there is a risk that the network will accept a pledge that
should not be a member of the network. As the address of the should not be a member of the network. As the address of the
manufacturer's MASA is provided in the IDevID using the extension manufacturer's MASA is provided in the IDevID using the extension
from Section 2.3, the malicious pledge will have no problem from Section 2.3, the malicious pledge will have no problem
collaborating with it's MASA to produce a completely valid voucher. collaborating with its MASA to produce a completely valid voucher.
BRSKI does not, however, fundamentally change the trust model from BRSKI does not, however, fundamentally change the trust model from
domain owner to manufacturer. Assuming that the pledge used its domain owner to manufacturer. Assuming that the pledge used its
IDevID with RFC7030 EST and BRSKI, the domain (registrar) still needs IDevID with EST [RFC7030] and BRSKI, the domain (registrar) still
to trust the manufacturer. needs to trust the manufacturer.
Establishing this trust between domain and manufacturer is outside Establishing this trust between domain and manufacturer is outside
the scope of BRSKI. There are a number of mechanisms that can the scope of BRSKI. There are a number of mechanisms that can be
adopted including: adopted including:
* Manually configuring each manufacturer's trust anchor. * Manually configuring each manufacturer's trust anchor.
* A Trust-On-First-Use (TOFU) mechanism. A human would be queried * A TOFU mechanism. A human would be queried upon seeing a
upon seeing a manufacturer's trust anchor for the first time, and manufacturer's trust anchor for the first time, and then the trust
then the trust anchor would be installed to the trusted store. anchor would be installed to the trusted store. There are risks
There are risks with this; even if the key to name mapping is with this; even if the key to name mapping is validated using
validated using something like the WebPKI, there remains the something like the WebPKI, there remains the possibility that the
possibility that the name is a look alike: e.g, dem0.example. vs name is a look alike: e.g., dem0.example. vs. demO.example.
demO.example.
* scanning the trust anchor from a QR code that came with the * scanning the trust anchor from a QR code that came with the
packaging (this is really a manual TOFU mechanism) packaging (this is really a manual TOFU mechanism).
* some sales integration process where trust anchors are provided as * some sales integration processing where trust anchors are provided
part of the sales process, probably included in a digital packing as part of the sales process, probably included in a digital
"slip", or a sales invoice. packing "slip", or a sales invoice.
* consortium membership, where all manufacturers of a particular * consortium membership, where all manufacturers of a particular
device category (e.g, a light bulb, or a cable-modem) are signed device category (e.g, a light bulb or a cable modem) are signed by
by an certificate authority specifically for this. This is done a CA specifically for this. This is done by CableLabs today. It
by CableLabs today. It is used for authentication and is used for authentication and authorization as part of
authorization as part of TR-79: [docsisroot] and [TR069]. [docsisroot] and [TR069].
The existing WebPKI provides a reasonable anchor between manufacturer The existing WebPKI provides a reasonable anchor between manufacturer
name and public key. It authenticates the key. It does not provide name and public key. It authenticates the key. It does not provide
a reasonable authorization for the manufacturer, so it is not a reasonable authorization for the manufacturer, so it is not
directly useable on it's own. directly usable on its own.
11.6. Manufacturer Maintenance of trust anchors 11.6. Manufacturer Maintenance of Trust Anchors
BRSKI depends upon the manufacturer building in trust anchors to the BRSKI depends upon the manufacturer building in trust anchors to the
pledge device. The voucher artifact which is signed by the MASA will pledge device. The voucher artifact that is signed by the MASA will
be validated by the pledge using that anchor. This implies that the be validated by the pledge using that anchor. This implies that the
manufacturer needs to maintain access to a signing key that the manufacturer needs to maintain access to a signing key that the
pledge can validate. pledge can validate.
The manufacturer will need to maintain the ability to make signatures The manufacturer will need to maintain the ability to make signatures
that can be validated for the lifetime that the device could be that can be validated for the lifetime that the device could be
onboarded. Whether this onboarding lifetime is less than the device onboarded. Whether this onboarding lifetime is less than the device
lifetime depends upon how the device is used. An inventory of lifetime depends upon how the device is used. An inventory of
devices kept in a warehouse as spares might not be onboarded for many devices kept in a warehouse as spares might not be onboarded for many
decades. decades.
There are good cryptographic hygiene reasons why a manufacturer would There are good cryptographic hygiene reasons why a manufacturer would
not want to maintain access to a private key for many decades. A not want to maintain access to a private key for many decades. A
manufacturer in that situation can leverage a long-term certificate manufacturer in that situation can leverage a long-term CA anchor,
authority anchor, built-in to the pledge, and then a certificate built-in to the pledge, and then a certificate chain may be
chain may be incorporated using the normal CMS certificate set. This incorporated using the normal CMS certificate set. This may increase
may increase the size of the voucher artifacts, but that is not a the size of the voucher artifacts, but that is not a significant
significant issues in non-constrained environments. issue in non-constrained environments.
There are a few other operational variations that manufacturers could There are a few other operational variations that manufacturers could
consider. For instance, there is no reason that every device need consider. For instance, there is no reason that every device need
have the same set of trust anchors pre-installed. Devices built in have the same set of trust anchors preinstalled. Devices built in
different factories, or on different days, or any other consideration different factories, or on different days, or in any other
could have different trust anchors built in, and the record of which consideration, could have different trust anchors built in, and the
batch the device is in would be recorded in the asset database. The record of which batch the device is in would be recorded in the asset
manufacturer would then know which anchor to sign an artifact database. The manufacturer would then know which anchor to sign an
against. artifact against.
Aside from the concern about long-term access to private keys, a Aside from the concern about long-term access to private keys, a
major limiting factor for the shelf-life of many devices will be the major limiting factor for the shelf life of many devices will be the
age of the cryptographic algorithms included. A device produced in age of the cryptographic algorithms included. A device produced in
2019 will have hardware and software capable of validating algorithms 2019 will have hardware and software capable of validating algorithms
common in 2019, and will have no defense against attacks (both common in 2019 and will have no defense against attacks (both quantum
quantum and von-neuman brute force attacks) which have not yet been and von Neumann brute-force attacks) that have not yet been invented.
invented. This concern is orthogonal to the concern about access to This concern is orthogonal to the concern about access to private
private keys, but this concern likely dominates and limits the keys, but this concern likely dominates and limits the life span of a
lifespan of a device in a warehouse. If any update to firmware to device in a warehouse. If any update to the firmware to support new
support new cryptographic mechanism were possible (while the device cryptographic mechanisms were possible (while the device was in a
was in a warehouse), updates to trust anchors would also be done at warehouse), updates to trust anchors would also be done at the same
the same time. time.
The set of standard operating procedures for maintaining high value The set of standard operating procedures for maintaining high-value
private keys is well documented. For instance, the WebPKI provides a private keys is well documented. For instance, the WebPKI provides a
number of options for audits at [cabforumaudit], and the DNSSEC root number of options for audits in [cabforumaudit], and the DNSSEC root
operations are well documented at [dnssecroot]. operations are well documented in [dnssecroot].
It is not clear if Manufacturers will take this level of precaution, It is not clear if manufacturers will take this level of precaution,
or how strong the economic incentives are to maintain an appropriate or how strong the economic incentives are to maintain an appropriate
level of security. level of security.
This next section examines the risk due to a compromised manufacturer The next section examines the risk due to a compromised manufacturer
IDevID signing key. This is followed by examination of the risk due IDevID signing key. This is followed by examination of the risk due
to a compromised MASA key. The third section sections below examines to a compromised MASA key. The third section below examines the
the situation where MASA web server itself is under attacker control, situation where a MASA web server itself is under attacker control,
but that the MASA signing key itself is safe in a not-directly but the MASA signing key itself is safe in a not-directly connected
connected hardware module. hardware module.
11.6.1. Compromise of Manufacturer IDevID signing keys 11.6.1. Compromise of Manufacturer IDevID Signing Keys
An attacker that has access to the key that the manufacturer uses to An attacker that has access to the key that the manufacturer uses to
sign IDevID certificates can create counterfeit devices. Such sign IDevID certificates can create counterfeit devices. Such
devices can claim to be from a particular manufacturer, but be devices can claim to be from a particular manufacturer but can be
entirely different devices: Trojan horses in effect. entirely different devices: Trojan horses in effect.
As the attacker controls the MASA URL in the certificate, the As the attacker controls the MASA URL in the certificate, the
registrar can be convinced to talk to the attackers' MASA. The registrar can be convinced to talk to the attacker's MASA. The
Registrar does not need to be in any kind of promiscuous mode to be registrar does not need to be in any kind of promiscuous mode to be
vulnerable. vulnerable.
In addition to creating fake devices, the attacker may also be able In addition to creating fake devices, the attacker may also be able
to issue revocations for existing certificates if the IDevID to issue revocations for existing certificates if the IDevID
certificate process relies upon CRL lists that are distributed. certificate process relies upon CRL lists that are distributed.
There does not otherwise seem to be any risk from this compromise to There does not otherwise seem to be any risk from this compromise to
devices which are already deployed, or which are sitting locally in devices that are already deployed or that are sitting locally in
boxes waiting for deployment (local spares). The issue is that boxes waiting for deployment (local spares). The issue is that
operators will be unable to trust devices which have been in an operators will be unable to trust devices that have been in an
uncontrolled warehouse as they do not know if those are real devices. uncontrolled warehouse as they do not know if those are real devices.
11.6.2. Compromise of MASA signing keys 11.6.2. Compromise of MASA Signing Keys
There are two periods of time in which to consider: when the MASA key There are two periods of time in which to consider: when the MASA key
has fallen into the hands of an attacker, and after the MASA has fallen into the hands of an attacker and after the MASA
recognizes that the key has been compromised. recognizes that the key has been compromised.
11.6.2.1. Attacker opportunties with compromised MASA key 11.6.2.1. Attacker Opportunities with a Compromised MASA Key
An attacker that has access to the MASA signing key could create An attacker that has access to the MASA signing key could create
vouchers. These vouchers could be for existing deployed devices, or vouchers. These vouchers could be for existing deployed devices or
for devices which are still in a warehouse. In order to exploit for devices that are still in a warehouse. In order to exploit these
these vouchers two things need to occur: the device has to go through vouchers, two things need to occur: the device has to go through a
a factory default boot cycle, and the registrar has to be convinced factory default boot cycle, and the registrar has to be convinced to
to contact the attacker's MASA. contact the attacker's MASA.
If the attacker controls a Registrar which is visible to the device, If the attacker controls a registrar that is visible to the device,
then there is no difficulty in delivery of the false voucher. A then there is no difficulty in delivery of the false voucher. A
possible practical example of an attack like this would be in a data possible practical example of an attack like this would be in a data
center, at an ISP peering point (whether a public IX, or a private center, at an ISP peering point (whether a public IX or a private
peering point). In such a situation, there are already cables peering point). In such a situation, there are already cables
attached to the equipment that lead to other devices (the peers at attached to the equipment that lead to other devices (the peers at
the IX), and through those links, the false voucher could be the IX), and through those links, the false voucher could be
delivered. The difficult part would be get the device put through a delivered. The difficult part would be to put the device through a
factory reset. This might be accomplished through social engineering factory reset. This might be accomplished through social engineering
of data center staff. Most locked cages have ventilation holes, and of data center staff. Most locked cages have ventilation holes, and
possibly a long "paperclip" could reach through to depress a factory possibly a long "paperclip" could reach through to depress a factory
reset button. Once such a piece of ISP equipment has been reset button. Once such a piece of ISP equipment has been
compromised, it could be used to compromise equipment that was compromised, it could be used to compromise equipment that it was
connected to (through long haul links even), assuming that those connected to (through long haul links even), assuming that those
pieces of equipment could also be forced through a factory reset. pieces of equipment could also be forced through a factory reset.
The above scenario seems rather unlikely as it requires some element The above scenario seems rather unlikely as it requires some element
of physical access; but were there a remote exploit that did not of physical access; but if there was a remote exploit that did not
cause a direct breach, but rather a fault that resulted in a factory cause a direct breach, but rather a fault that resulted in a factory
reset, this could provide a reasonable path. reset, this could provide a reasonable path.
The above deals with ANI uses of BRSKI. For cases where 802.11 or The above deals with ANI uses of BRSKI. For cases where IEEE 802.11
802.15.4 is involved, the need to connect directly to the device is or 802.15.4 is involved, the need to connect directly to the device
eliminated, but the need to do a factory reset is not. Physical is eliminated, but the need to do a factory reset is not. Physical
possession of the device is not required as above, provided that possession of the device is not required as above, provided that
there is some way to force a factory reset. With some consumers there is some way to force a factory reset. With some consumer
devices with low overall implementation quality, the end users might devices that have low overall implementation quality, end users might
be familiar with needing to reset the device regularly. be familiar with the need to reset the device regularly.
The authors are unable to come up with an attack scenario where a The authors are unable to come up with an attack scenario where a
compromised voucher signature enables an attacker to introduce a compromised voucher signature enables an attacker to introduce a
compromised pledge into an existing operator's network. This is the compromised pledge into an existing operator's network. This is the
case because the operator controls the communication between case because the operator controls the communication between
Registrar and MASA, and there is no opportunity to introduce the fake registrar and MASA, and there is no opportunity to introduce the fake
voucher through that conduit. voucher through that conduit.
11.6.2.2. Risks after key compromise is known 11.6.2.2. Risks after Key Compromise is Known
Once the operator of the MASA realizes that the voucher signing key Once the operator of the MASA realizes that the voucher signing key
has been compromised it has to do a few things. has been compromised, it has to do a few things.
First, it MUST issue a firmware update to all devices that had that First, it MUST issue a firmware update to all devices that had that
key as a trust anchor, such that they will no longer trust vouchers key as a trust anchor, such that they will no longer trust vouchers
from that key. This will affect devices in the field which are from that key. This will affect devices in the field that are
operating, but those devices, being in operation, are not performing operating, but those devices, being in operation, are not performing
onboarding operations, so this is not a critical patch. onboarding operations, so this is not a critical patch.
Devices in boxes (in warehouses) are vulnerable, and remain Devices in boxes (in warehouses) are vulnerable and remain vulnerable
vulnerable until patched. An operator would be prudent to unbox the until patched. An operator would be prudent to unbox the devices,
devices, onboard them in a safe environment, and then perform onboard them in a safe environment, and then perform firmware
firmware updates. This does not have to be done by the end-operator; updates. This does not have to be done by the end-operator; it could
it could be done by a distributor that stores the spares. A be done by a distributor that stores the spares. A recommended
recommended practice for high value devices (which typically have a practice for high-value devices (which typically have a <4hr service
<4hr service window) may be to validate the device operation on a window) may be to validate the device operation on a regular basis
regular basis anyway. anyway.
If the onboarding process includes attestations about firmware If the onboarding process includes attestations about firmware
versions, then through that process the operator would be advised to versions, then through that process, the operator would be advised to
upgrade the firmware before going into production. Unfortunately, upgrade the firmware before going into production. Unfortunately,
this does not help against situations where the attacker operates this does not help against situations where the attacker operates
their own Registrar (as listed above). their own registrar (as listed above).
[RFC8366] section 6.1 explains the need for short-lived vouchers. The need for short-lived vouchers is explained in [RFC8366],
The nonce guarantees freshness, and the short-lived nature of the Section 6.1. The nonce guarantees freshness, and the short-lived
voucher means that the window to deliver a fake voucher is very nature of the voucher means that the window to deliver a fake voucher
short. A nonceless, long-lived voucher would be the only option for is very short. A nonceless, long-lived voucher would be the only
the attacker, and devices in the warehouse would be vulnerable to option for the attacker, and devices in the warehouse would be
such a thing. vulnerable to such a thing.
A key operational recommendation is for manufacturers to sign A key operational recommendation is for manufacturers to sign
nonceless, long-lived vouchers with a different key that they sign nonceless, long-lived vouchers with a different key than what is used
short-lived vouchers. That key needs significantly better to sign short-lived vouchers. That key needs significantly better
protection. If both keys come from a common trust-anchor (the protection. If both keys come from a common trust-anchor (the
manufacturer's CA), then a compromise of the manufacturer's CA would manufacturer's CA), then a compromise of the manufacturer's CA would
compromise both keys. Such a compromise of the manufacturer's CA compromise both keys. Such a compromise of the manufacturer's CA
likely compromises all keys outlined in this section. likely compromises all keys outlined in this section.
11.6.3. Compromise of MASA web service 11.6.3. Compromise of MASA Web Service
An attacker that takes over the MASA web service has a number of An attacker that takes over the MASA web service can inflict a number
attacks. The most obvious one is simply to take the database listing of attacks. The most obvious one is simply to take the database
customers and devices and to sell this data to other attackers who listing of customers and devices and sell the data to other attackers
will now know where to find potentially vulnerable devices. who will now know where to find potentially vulnerable devices.
The second most obvious thing that the attacker can do is to kill the The second most obvious thing that the attacker can do is to kill the
service, or make it operate unreliably, making customers frustrated. service, or make it operate unreliably, making customers frustrated.
This could have a serious affect on ability to deploy new services by This could have a serious effect on the ability to deploy new
customers, and would be a significant issue during disaster recovery. services by customers and would be a significant issue during
disaster recovery.
While the compromise of the MASA web service may lead to the While the compromise of the MASA web service may lead to the
comp