draft-ietf-acme-star-11.txt   rfc8739.txt 
ACME Working Group Y. Sheffer Internet Engineering Task Force (IETF) Y. Sheffer
Internet-Draft Intuit Request for Comments: 8739 Intuit
Intended status: Standards Track D. Lopez Category: Standards Track D. Lopez
Expires: April 26, 2020 O. Gonzalez de Dios ISSN: 2070-1721 O. Gonzalez de Dios
A. Pastor Perales A. Pastor Perales
Telefonica I+D Telefonica I+D
T. Fossati T. Fossati
ARM ARM
October 24, 2019 March 2020
Support for Short-Term, Automatically-Renewed (STAR) Certificates in Support for Short-Term, Automatically Renewed (STAR) Certificates in the
Automated Certificate Management Environment (ACME) Automated Certificate Management Environment (ACME)
draft-ietf-acme-star-11
Abstract Abstract
Public-key certificates need to be revoked when they are compromised, Public key certificates need to be revoked when they are compromised,
that is, when the associated private key is exposed to an that is, when the associated private key is exposed to an
unauthorized entity. However the revocation process is often unauthorized entity. However, the revocation process is often
unreliable. An alternative to revocation is issuing a sequence of unreliable. An alternative to revocation is issuing a sequence of
certificates, each with a short validity period, and terminating this certificates, each with a short validity period, and terminating the
sequence upon compromise. This memo proposes an ACME extension to sequence upon compromise. This memo proposes an Automated
enable the issuance of short-term and automatically renewed (STAR) Certificate Management Environment (ACME) extension to enable the
X.509 certificates. issuance of Short-Term, Automatically Renewed (STAR) X.509
certificates.
[RFC Editor: please remove before publication]
While the draft is being developed, the editor's version can be found
at https://github.com/yaronf/I-D/tree/master/STAR.
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.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on April 26, 2020. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8739.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
1.1. Name Delegation Use Case . . . . . . . . . . . . . . . . 4 1.1. Name Delegation Use Case
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Terminology
1.3. Conventions used in this document . . . . . . . . . . . . 4 1.3. Conventions Used in This Document
2. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Protocol Flow
2.1. Bootstrap . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Bootstrap
2.2. Refresh . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Auto Renewal
2.3. Termination . . . . . . . . . . . . . . . . . . . . . . . 6 2.3. Termination
3. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 7 3. Protocol Details
3.1. ACME Extensions . . . . . . . . . . . . . . . . . . . . . 7 3.1. ACME Extensions
3.1.1. Extending the Order Resource . . . . . . . . . . . . 7 3.1.1. Extending the Order Resource
3.1.2. Canceling an Auto-renewal Order . . . . . . . . . . . 8 3.1.2. Canceling an Auto-renewal Order
3.2. Capability Discovery . . . . . . . . . . . . . . . . . . 10 3.2. Capability Discovery
3.3. Fetching the Certificates . . . . . . . . . . . . . . . . 11 3.3. Fetching the Certificates
3.4. Negotiating an unauthenticated GET . . . . . . . . . . . 13 3.4. Negotiating an Unauthenticated GET
3.5. Computing notBefore and notAfter of STAR Certificates . . 14 3.5. Computing notBefore and notAfter of STAR Certificates
3.5.1. Example . . . . . . . . . . . . . . . . . . . . . . . 15 3.5.1. Example
4. Operational Considerations . . . . . . . . . . . . . . . . . 15 4. Operational Considerations
4.1. The Meaning of "Short Term" and the Impact of Skewed 4.1. The Meaning of "Short Term" and the Impact of Skewed Clocks
Clocks . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.2. Impact on Certificate Transparency (CT) Logs
4.2. Impact on Certificate Transparency (CT) Logs . . . . . . 16 4.3. HTTP Caching and Dependability
4.3. HTTP Caching and Dependability . . . . . . . . . . . . . 16 5. IANA Considerations
5. Implementation Status . . . . . . . . . . . . . . . . . . . . 17 5.1. New Registries
5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 17 5.2. New Error Types
5.1.1. ACME Server with STAR extension . . . . . . . . . . . 18 5.3. New Fields in Order Objects
5.1.2. STAR Proxy . . . . . . . . . . . . . . . . . . . . . 18 5.4. Fields in the "auto-renewal" Object within an Order Object
5.2. Level of Maturity . . . . . . . . . . . . . . . . . . . . 18 5.5. New Fields in the "meta" Object within a Directory Object
5.3. Coverage . . . . . . . . . . . . . . . . . . . . . . . . 18 5.6. Fields in the "auto-renewal" Object within a Directory
5.4. Version Compatibility . . . . . . . . . . . . . . . . . . 19 Metadata Object
5.5. Licensing . . . . . . . . . . . . . . . . . . . . . . . . 19 5.7. Cert-Not-Before and Cert-Not-After HTTP Headers
5.6. Implementation experience . . . . . . . . . . . . . . . . 19 6. Security Considerations
5.7. Contact Information . . . . . . . . . . . . . . . . . . . 19 6.1. No Revocation
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 6.2. Denial-of-Service Considerations
6.1. New Registries . . . . . . . . . . . . . . . . . . . . . 19 6.3. Privacy Considerations
6.2. New Error Types . . . . . . . . . . . . . . . . . . . . . 20 7. References
6.3. New fields in Order Objects . . . . . . . . . . . . . . . 20 7.1. Normative References
6.4. Fields in the "auto-renewal" Object within an Order 7.2. Informative References
Object . . . . . . . . . . . . . . . . . . . . . . . . . 21 Acknowledgments
6.5. New fields in the "meta" Object within a Directory Object 21 Authors' Addresses
6.6. Fields in the "auto-renewal" Object within a Directory
Metadata Object . . . . . . . . . . . . . . . . . . . . . 22
6.7. Cert-Not-Before and Cert-Not-After HTTP Headers . . . . . 22
7. Security Considerations . . . . . . . . . . . . . . . . . . . 22
7.1. No revocation . . . . . . . . . . . . . . . . . . . . . . 22
7.2. Denial of Service Considerations . . . . . . . . . . . . 23
7.3. Privacy Considerations . . . . . . . . . . . . . . . . . 24
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Normative References . . . . . . . . . . . . . . . . . . 24
9.2. Informative References . . . . . . . . . . . . . . . . . 25
Appendix A. Document History . . . . . . . . . . . . . . . . . . 27
A.1. draft-ietf-acme-star-11 . . . . . . . . . . . . . . . . . 27
A.2. draft-ietf-acme-star-10 . . . . . . . . . . . . . . . . . 27
A.3. draft-ietf-acme-star-09 . . . . . . . . . . . . . . . . . 27
A.4. draft-ietf-acme-star-08 . . . . . . . . . . . . . . . . . 27
A.5. draft-ietf-acme-star-07 . . . . . . . . . . . . . . . . . 27
A.6. draft-ietf-acme-star-06 . . . . . . . . . . . . . . . . . 27
A.7. draft-ietf-acme-star-05 . . . . . . . . . . . . . . . . . 28
A.8. draft-ietf-acme-star-04 . . . . . . . . . . . . . . . . . 28
A.9. draft-ietf-acme-star-03 . . . . . . . . . . . . . . . . . 28
A.10. draft-ietf-acme-star-02 . . . . . . . . . . . . . . . . . 28
A.11. draft-ietf-acme-star-01 . . . . . . . . . . . . . . . . . 28
A.12. draft-ietf-acme-star-00 . . . . . . . . . . . . . . . . . 28
A.13. draft-sheffer-acme-star-02 . . . . . . . . . . . . . . . 29
A.14. draft-sheffer-acme-star-01 . . . . . . . . . . . . . . . 29
A.15. draft-sheffer-acme-star-00 . . . . . . . . . . . . . . . 29
A.16. draft-sheffer-acme-star-lurk-00 . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction 1. Introduction
The ACME protocol [RFC8555] automates the process of issuing a The ACME protocol [RFC8555] automates the process of issuing a
certificate to a named entity (an Identifier Owner or IdO). certificate to a named entity (an Identifier Owner or IdO).
Typically, but not always, the identifier is a domain name. Typically, but not always, the identifier is a domain name.
If the IdO wishes to obtain a string of short-term certificates If the IdO wishes to obtain a string of short-term certificates
originating from the same private key (see [Topalovic] about why originating from the same private key (see [TOPALOVIC] about why
using short-lived certificates might be preferable to explicit using short-lived certificates might be preferable to explicit
revocation), she must go through the whole ACME protocol each time a revocation), she must go through the whole ACME protocol each time a
new short-term certificate is needed - e.g., every 2-3 days. If done new short-term certificate is needed, e.g., every 2-3 days. If done
this way, the process would involve frequent interactions between the this way, the process would involve frequent interactions between the
registration function of the ACME Certification Authority (CA) and registration function of the ACME Certification Authority (CA) and
the identity provider infrastructure (e.g.: DNS, web servers), the identity provider infrastructure (e.g., DNS, web servers),
therefore making the issuance of short-term certificates exceedingly therefore making the issuance of short-term certificates exceedingly
dependent on the reliability of both. dependent on the reliability of both.
This document presents an extension of the ACME protocol that This document presents an extension of the ACME protocol that
optimizes this process by making short-term certificates first class optimizes this process by making short-term certificates first-class
objects in the ACME ecosystem. Once the Order for a string of short- objects in the ACME ecosystem. Once the Order for a string of short-
term certificates is accepted, the CA is responsible for publishing term certificates is accepted, the CA is responsible for publishing
the next certificate at an agreed upon URL before the previous one the next certificate at an agreed upon URL before the previous one
expires. The IdO can terminate the automatic renewal before the expires. The IdO can terminate the automatic renewal before the
negotiated deadline, if needed - e.g., on key compromise. negotiated deadline if needed, e.g., on key compromise.
For a more generic treatment of STAR certificates, readers are For a more generic treatment of STAR certificates, readers are
referred to [I-D.nir-saag-star]. referred to [SHORT-TERM-CERTS].
1.1. Name Delegation Use Case 1.1. Name Delegation Use Case
The proposed mechanism can be used as a building block of an The proposed mechanism can be used as a building block of an
efficient name-delegation protocol, for example one that exists efficient name-delegation protocol, for example, one that exists
between a CDN or a cloud provider and its customers between a Content Distribution Network (CDN) or a cloud provider and
[I-D.ietf-acme-star-delegation]. At any time, the service customer its customers [STAR-DELEGATION]. At any time, the service customer
(i.e., the IdO) can terminate the delegation by simply instructing (i.e., the IdO) can terminate the delegation by simply instructing
the CA to stop the automatic renewal and letting the currently active the CA to stop the automatic renewal and letting the currently active
certificate expire shortly thereafter. certificate expire shortly thereafter.
Note that in the name delegation use case the delegated entity needs Note that in the name delegation use case, the delegated entity needs
to access the auto-renewed certificate without being in possession of to access the auto-renewed certificate without being in possession of
the ACME account key that was used for initiating the STAR issuance. the ACME account key that was used for initiating the STAR issuance.
This leads to the optional use of unauthenticated GET in this This leads to the optional use of unauthenticated GET in this
protocol (Section 3.4). protocol (Section 3.4).
1.2. Terminology 1.2. Terminology
IdO Identifier Owner, the owner of an identifier, e.g.: a domain IdO Identifier Owner, the owner of an identifier, e.g., a domain
name, a telephone number. name, a telephone number, etc.
STAR Short-Term and Automatically Renewed X.509 certificates. STAR Short-Term, Automatically Renewed X.509 certificates.
1.3. Conventions used in this document 1.3. Conventions Used in This Document
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 "OPTIONAL" in this document are to be interpreted as described in
BCP 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.
2. Protocol Flow 2. Protocol Flow
The following subsections describe the three main phases of the The following subsections describe the three main phases of the
protocol: protocol:
o Bootstrap: the IdO asks an ACME CA to create a short-term and * Bootstrap: the IdO asks an ACME CA to create a short-term,
automatically-renewed (STAR) certificate (Section 2.1); automatically renewed (STAR) certificate (Section 2.1);
o Auto-renewal: the ACME CA periodically re-issues the short-term * Auto-renewal: the ACME CA periodically reissues the short-term
certificate and posts it to the star-certificate URL certificate and posts it to the star-certificate URL
(Section 2.2); (Section 2.2);
o Termination: the IdO requests the ACME CA to discontinue the * Termination: the IdO requests the ACME CA to discontinue the
automatic renewal of the certificate (Section 2.3). automatic renewal of the certificate (Section 2.3).
2.1. Bootstrap 2.1. Bootstrap
The IdO, in its role as an ACME client, requests the CA to issue a The IdO, in its role as an ACME client, requests the CA to issue a
STAR certificate, i.e., one that: STAR certificate, i.e., one that:
o Has a short validity, e.g., 24 to 72 hours. Note that the exact * Has a short validity, e.g., 24 to 72 hours. Note that the exact
definition of "short" depends on the use case; definition of "short" depends on the use case;
o Is automatically renewed by the CA for a certain period of time; * Is automatically renewed by the CA for a certain period of time;
o Is downloadable from a (highly available) location. * Is downloadable from a (highly available) location.
Other than that, the ACME protocol flows as usual between IdO and CA. Other than that, the ACME protocol flows as usual between IdO and CA.
In particular, IdO is responsible for satisfying the requested ACME In particular, IdO is responsible for satisfying the requested ACME
challenges until the CA is willing to issue the requested challenges until the CA is willing to issue the requested
certificate. Per normal ACME processing, the IdO is given back an certificate. Per normal ACME processing, the IdO is given back an
Order resource associated with the STAR certificate to be used in Order resource associated with the STAR certificate to be used in
subsequent interaction with the CA (e.g., if the certificate needs to subsequent interaction with the CA (e.g., if the certificate needs to
be terminated.) be terminated.)
The bootstrap phase ends when the ACME CA updates the Order resource The bootstrap phase ends when the ACME CA updates the Order resource
to include the URL for the issued STAR certificate. to include the URL for the issued STAR certificate.
2.2. Refresh 2.2. Auto Renewal
The CA issues the initial certificate after the authorization The CA issues the initial certificate after the authorization
completes successfully. It then automatically re-issues the completes successfully. It then automatically reissues the
certificate using the same CSR (and therefore the same identifier and certificate using the same Certificate Signing Request (CSR) (and
public key) before the previous one expires, and publishes it to the therefore the same identifier and public key) before the previous one
URL that was returned to the IdO at the end of the bootstrap phase. expires and publishes it to the URL that was returned to the IdO at
The certificate user, which could be either the IdO itself or a the end of the bootstrap phase. The certificate user, which could be
delegated third party, as described in either the IdO itself or a delegated third party as described in
[I-D.ietf-acme-star-delegation], obtains the certificate [STAR-DELEGATION], obtains the certificate (Section 3.3) and uses it.
(Section 3.3) and uses it.
The refresh process (Figure 1) goes on until either: The auto-renewal process (Figure 1) goes on until either:
o IdO explicitly terminates the automatic renewal (Section 2.3); or * IdO explicitly terminates the automatic renewal (Section 2.3); or
o Automatic renewal expires. * Automatic renewal expires.
Certificate ACME/STAR Certificate ACME/STAR
User Server User Server
| Retrieve cert | [...] | Retrieve cert | [...]
|---------------------->| | |---------------------->| |
| +------. / | +------. /
| | | / | | | /
| | Automatic renewal : | | Automatic renewal :
| | | \ | | | \
| |<-----' \ | |<-----' \
skipping to change at page 6, line 36 skipping to change at line 234
|---------------------->| short validity period |---------------------->| short validity period
| | | | | |
| +------. / | +------. /
| | | / | | | /
| | Automatic renewal : | | Automatic renewal :
| | | \ | | | \
| |<-----' \ | |<-----' \
| | | | | |
| [...] | [...] | [...] | [...]
Figure 1: Auto renewal Figure 1: Auto-renewal
2.3. Termination 2.3. Termination
The IdO may request early termination of the STAR certificate by The IdO may request early termination of the STAR certificate by
sending a cancellation request to the Order resource, as described in sending a cancellation request to the Order resource as described in
Section 3.1.2. After the CA receives and verifies the request, it Section 3.1.2. After the CA receives and verifies the request, it
shall: shall:
o Cancel the automatic renewal process for the STAR certificate; * Cancel the automatic renewal process for the STAR certificate;
o Change the certificate publication resource to return an error * Change the certificate publication resource to return an error
indicating the termination of the issuance; indicating the termination of the issuance;
o Change the status of the Order to "canceled". * Change the status of the Order to "canceled".
Note that it is not necessary to explicitly revoke the short-term Note that it is not necessary to explicitly revoke the short-term
certificate. certificate.
Certificate ACME/STAR Certificate ACME/STAR
User IdO Server User IdO Server
| | | | | |
| | Cancel Order | | | Cancel Order |
| +---------------------->| | +---------------------->|
| | +-------. | | +-------.
| | | | | | | |
| | | End auto renewal | | | End auto-renewal
| | | Remove cert link | | | Remove cert link
| | | etc. | | | etc.
| | | | | | | |
| | Done |<------' | | Done |<------'
| |<----------------------+ | |<----------------------+
| | | | | |
| | | |
| Retrieve cert | | Retrieve cert |
+---------------------------------------------->| +---------------------------------------------->|
| Error: autoRenewalCanceled | | Error: autoRenewalCanceled |
|<----------------------------------------------+ |<----------------------------------------------+
| | | |
Figure 2: Termination Figure 2: Termination
3. Protocol Details 3. Protocol Details
This section describes the protocol details, namely the extensions to This section describes the protocol details, namely the extensions to
the ACME protocol required to issue STAR certificates. the ACME protocol required to issue STAR certificates.
3.1. ACME Extensions 3.1. ACME Extensions
This protocol extends the ACME protocol, to allow for automatically This protocol extends the ACME protocol to allow for automatically
renewed Orders. renewed Orders.
3.1.1. Extending the Order Resource 3.1.1. Extending the Order Resource
The Order resource is extended with a new "auto-renewal" object that The Order resource is extended with a new "auto-renewal" object that
MUST be present for STAR certificates. The "auto-renewal" object has MUST be present for STAR certificates. The "auto-renewal" object has
the following structure: the following structure:
o start-date (optional, string): the earliest date of validity of * start-date (optional, string): The earliest date of validity of
the first certificate issued, in [RFC3339] format. When omitted, the first certificate issued, in [RFC3339] format. When omitted,
the start date is as soon as authorization is complete. the start date is as soon as authorization is complete.
o end-date (required, string): the latest date of validity of the * end-date (required, string): The latest date of validity of the
last certificate issued, in [RFC3339] format. last certificate issued, in [RFC3339] format.
o lifetime (required, integer): the maximum validity period of each * lifetime (required, integer): The maximum validity period of each
STAR certificate, an integer that denotes a number of seconds. STAR certificate, an integer that denotes a number of seconds.
This is a nominal value which does not include any extra validity This is a nominal value that does not include any extra validity
time due to server or client adjustment (see below). time due to server or client adjustment (see below).
* lifetime-adjust (optional, integer): The amount of "left pad"
o lifetime-adjust (optional, integer): amount of "left pad" added to added to each STAR certificate, an integer that denotes a number
each STAR certificate, an integer that denotes a number of of seconds. The default is 0. If present, the value of the
seconds. The default is 0. If present, the value of the
notBefore field that would otherwise appear in the STAR notBefore field that would otherwise appear in the STAR
certificates is pre-dated by the specified number of seconds. See certificates is pre-dated by the specified number of seconds. See
also Section 4.1 for why a client might want to use this control Section 4.1 for why a client might want to use this control, and
and Section 3.5 for how the effective certificate lifetime is Section 3.5 for how the effective certificate lifetime is
computed. The value reflected by the server, together with the computed. The value reflected by the server, together with the
value of the lifetime attribute, can be used by the client as a value of the lifetime attribute, can be used by the client as a
hint to configure its polling timer. hint to configure its polling timer.
o allow-certificate-get (optional, boolean): see Section 3.4. * allow-certificate-get (optional, boolean): See Section 3.4.
These attributes are included in a POST message when creating the These attributes are included in a POST message when creating the
Order, as part of the "payload" encoded object. They are returned Order as part of the object encoded as "payload". They are returned
when the Order has been created, and the ACME server MAY adjust them when the Order has been created. The ACME server MAY adjust them at
at will, according to its local policy (see also Section 3.2). will according to its local policy (see also Section 3.2).
The optional notBefore and notAfter fields defined in Section 7.1.3 The optional notBefore and notAfter fields defined in Section 7.1.3
of [RFC8555] MUST NOT be present in a STAR Order. If they are of [RFC8555] MUST NOT be present in a STAR Order. If they are
included, the server MUST return an error with status code 400 "Bad included, the server MUST return an error with status code 400 (Bad
Request" and type "malformedRequest". Request) and type "malformedRequest".
Section 7.1.6 of [RFC8555] defines the following values for the Order Section 7.1.6 of [RFC8555] defines the following values for the Order
resource's status: "pending", "ready", "processing", "valid", and resource's status: "pending", "ready", "processing", "valid", and
"invalid". In the case of auto-renewal Orders, the status MUST be "invalid". In the case of auto-renewal Orders, the status MUST be
"valid" as long as STAR certificates are being issued. We add a new "valid" as long as STAR certificates are being issued. This document
status value: "canceled", see Section 3.1.2. adds a new status value: "canceled" (see Section 3.1.2).
A STAR certificate is by definition a dynamic resource, i.e., it A STAR certificate is by definition a dynamic resource, i.e., it
refers to an entity that varies over time. Instead of overloading refers to an entity that varies over time. Instead of overloading
the semantics of the "certificate" attribute, this document defines a the semantics of the "certificate" attribute, this document defines a
new attribute "star-certificate" to be used instead of "certificate". new attribute, "star-certificate", to be used instead of
"certificate".
o star-certificate (optional, string): A URL for the (rolling) STAR * star-certificate (optional, string): A URL for the (rolling) STAR
certificate that has been issued in response to this Order. certificate that has been issued in response to this Order.
3.1.2. Canceling an Auto-renewal Order 3.1.2. Canceling an Auto-renewal Order
An important property of the auto-renewal Order is that it can be An important property of the auto-renewal Order is that it can be
canceled by the IdO, with no need for certificate revocation. To canceled by the IdO with no need for certificate revocation. To
cancel the Order, the ACME client sends a POST to the Order URL as cancel the Order, the ACME client sends a POST to the Order URL as
shown in Figure 3. shown in Figure 3.
POST /acme/order/ogfr8EcolOT HTTP/1.1 POST /acme/order/ogfr8EcolOT HTTP/1.1
Host: example.org Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"kid": "https://example.com/acme/acct/gw06UNhKfOve", "kid": "https://example.com/acme/acct/gw06UNhKfOve",
"nonce": "Alc00Ap6Rt7GMkEl3L1JX5", "nonce": "Alc00Ap6Rt7GMkEl3L1JX5",
"url": "https://example.com/acme/order/ogfr8EcolOT" "url": "https://example.com/acme/order/ogfr8EcolOT"
}), }),
"payload": base64url({ "payload": base64url({
skipping to change at page 9, line 29 skipping to change at line 367
"signature": "g454e3hdBlkT4AEw...nKePnUyZTjGtXZ6H" "signature": "g454e3hdBlkT4AEw...nKePnUyZTjGtXZ6H"
} }
Figure 3: Canceling an Auto-renewal Order Figure 3: Canceling an Auto-renewal Order
After a successful cancellation, the server MUST NOT issue any After a successful cancellation, the server MUST NOT issue any
additional certificates for this Order. additional certificates for this Order.
When the Order is canceled, the server: When the Order is canceled, the server:
o MUST update the status of the Order resource to "canceled" and * MUST update the status of the Order resource to "canceled" and
MUST set an appropriate "expires" date; MUST set an appropriate "expires" date;
o MUST respond with 403 (Forbidden) to any requests to the star- * MUST respond with 403 (Forbidden) to any requests to the star-
certificate endpoint. The response SHOULD provide additional certificate endpoint. The response SHOULD provide additional
information using a problem document [RFC7807] with type information using a problem document [RFC7807] with type
"urn:ietf:params:acme:error:autoRenewalCanceled". "urn:ietf:params:acme:error:autoRenewalCanceled".
Issuing a cancellation for an Order that is not in "valid" state is Issuing a cancellation for an Order that is not in "valid" state is
not allowed. A client MUST NOT send such a request, and a server not allowed. A client MUST NOT send such a request, and a server
MUST return an error response with status code 400 (Bad Request) and MUST return an error response with status code 400 (Bad Request) and
type "urn:ietf:params:acme:error:autoRenewalCancellationInvalid". type "urn:ietf:params:acme:error:autoRenewalCancellationInvalid".
The state machine described in Section 7.1.6 of [RFC8555] is extended The state machine described in Section 7.1.6 of [RFC8555] is extended
as illustrated in Figure 4 (State Transitions for Order Objects). as illustrated in Figure 4.
pending --------------+ pending --------------+
| | | |
| All authz | | All authz |
| "valid" | | "valid" |
V | V |
ready ---------------+ ready ---------------+
| | | |
| Receive | | Receive |
| finalize | | finalize |
| request | | request |
V | V |
processing ------------+ processing ------------+
| | | |
| First | | First |
| certificate | Error or | certificate | Error or
| issued | Authorization failure | issued | Authorization failure
V V | |
valid invalid | V
| | invalid
| STAR
| Certificate
| canceled
V V
canceled valid----------------+
| |
| STAR |
| Certificate | Natural
| canceled | Expiration
V |
canceled ='=
Figure 4 Figure 4: State Transitions for STAR Order Objects
Explicit certificate revocation using the revokeCert interface Explicit certificate revocation using the revokeCert interface
(Section 7.6 of [RFC8555]) is not supported for STAR certificates. A (Section 7.6 of [RFC8555]) is not supported for STAR certificates. A
server receiving a revocation request for a STAR certificate MUST server receiving a revocation request for a STAR certificate MUST
return an error response with status code 403 (Forbidden) and type return an error response with status code 403 (Forbidden) and type
"urn:ietf:params:acme:error:autoRenewalRevocationNotSupported". "urn:ietf:params:acme:error:autoRenewalRevocationNotSupported".
3.2. Capability Discovery 3.2. Capability Discovery
In order to support the discovery of STAR capabilities, the "meta" In order to support the discovery of STAR capabilities, the "meta"
field inside the directory object defined in Section 9.7.6 of field inside the directory object defined in Section 9.7.6 of
[RFC8555] is extended with a new "auto-renewal" object. The "auto- [RFC8555] is extended with a new "auto-renewal" object. The "auto-
renewal" object MUST be present if the server supports STAR. Its renewal" object MUST be present if the server supports STAR. Its
structure is as follows: structure is as follows:
o min-lifetime (required, integer): minimum acceptable value for * min-lifetime (required, integer): Minimum acceptable value for
auto-renewal lifetime, in seconds. auto-renewal lifetime, in seconds.
o max-duration (required, integer): maximum delta between the auto- * max-duration (required, integer): Maximum allowed delta between
renewal end-date and start-date, in seconds. the end-date and start-date attributes of the Order's auto-renewal
o allow-certificate-get (optional, boolean): see Section 3.4. object.
* allow-certificate-get (optional, boolean): See Section 3.4.
An example directory object advertising STAR support with one day An example directory object advertising STAR support with one-day
min-lifetime and one year max-duration, and supporting certificate min-lifetime and one-year max-duration and supporting certificate
fetching with an HTTP GET is shown in Figure 5. fetching with an HTTP GET is shown in Figure 5.
{ {
"new-nonce": "https://example.com/acme/new-nonce", "new-nonce": "https://example.com/acme/new-nonce",
"new-account": "https://example.com/acme/new-account", "new-account": "https://example.com/acme/new-account",
"new-order": "https://example.com/acme/new-order", "new-order": "https://example.com/acme/new-order",
"new-authz": "https://example.com/acme/new-authz", "new-authz": "https://example.com/acme/new-authz",
"revoke-cert": "https://example.com/acme/revoke-cert", "revoke-cert": "https://example.com/acme/revoke-cert",
"key-change": "https://example.com/acme/key-change", "key-change": "https://example.com/acme/key-change",
"meta": { "meta": {
skipping to change at page 11, line 28 skipping to change at line 456
"website": "https://www.example.com/", "website": "https://www.example.com/",
"caa-identities": ["example.com"], "caa-identities": ["example.com"],
"auto-renewal": { "auto-renewal": {
"min-lifetime": 86400, "min-lifetime": 86400,
"max-duration": 31536000, "max-duration": 31536000,
"allow-certificate-get": true "allow-certificate-get": true
} }
} }
} }
Figure 5: Directory object with STAR support Figure 5: Directory Object with STAR Support
3.3. Fetching the Certificates 3.3. Fetching the Certificates
The certificate is fetched from the star-certificate endpoint with The certificate is fetched from the star-certificate endpoint with
POST-as-GET as per [RFC8555] Section 7.4.2, unless client and server POST-as-GET as per Section 7.4.2 of [RFC8555] unless the client and
have successfully negotiated the "unauthenticated GET" option server have successfully negotiated the "unauthenticated GET" option
described in Section 3.4. In such case, the client can simply issue described in Section 3.4. In such case, the client can simply issue
a GET to the star-certificate resource without authenticating itself a GET to the star-certificate resource without authenticating itself
to the server as illustrated in Figure 6. to the server as illustrated in Figure 6.
GET /acme/cert/g7m3ZQeTEqa HTTP/1.1 GET /acme/cert/g7m3ZQeTEqa HTTP/1.1
Host: example.org Host: example.com
Accept: application/pem-certificate-chain Accept: application/pem-certificate-chain
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/pem-certificate-chain Content-Type: application/pem-certificate-chain
Link: <https://example.com/acme/some-directory>;rel="index" Link: <https://example.com/acme/some-directory>;rel="index"
Cert-Not-Before: Thu, 3 Oct 2019 00:00:00 GMT Cert-Not-Before: Thu, 3 Oct 2019 00:00:00 GMT
Cert-Not-After: Thu, 10 Oct 2019 00:00:00 GMT Cert-Not-After: Thu, 10 Oct 2019 00:00:00 GMT
-----BEGIN CERTIFICATE----- -----BEGIN CERTIFICATE-----
[End-entity certificate contents] [End-entity certificate contents]
-----END CERTIFICATE----- -----END CERTIFICATE-----
-----BEGIN CERTIFICATE----- -----BEGIN CERTIFICATE-----
[Issuer certificate contents] [Issuer certificate contents]
-----END CERTIFICATE----- -----END CERTIFICATE-----
-----BEGIN CERTIFICATE----- -----BEGIN CERTIFICATE-----
[Other certificate contents] [Other certificate contents]
-----END CERTIFICATE----- -----END CERTIFICATE-----
Figure 6: Fetching a STAR certificate with unauthenticated GET Figure 6: Fetching a STAR Certificate with Unauthenticated GET
The Server SHOULD include the "Cert-Not-Before" and "Cert-Not-After" The server SHOULD include the "Cert-Not-Before" and "Cert-Not-After"
HTTP header fields in the response. When they exist, they MUST be HTTP header fields in the response. When they exist, they MUST be
equal to the respective fields inside the end-entity certificate. equal to the respective fields inside the end-entity certificate.
Their format is "HTTP-date" as defined in Section 7.1.1.2 of Their format is "HTTP-date" as defined in Section 7.1.1.2 of
[RFC7231]. Their purpose is to enable client implementations that do [RFC7231]. Their purpose is to enable client implementations that do
not parse the certificate. not parse the certificate.
Following are further clarifications regarding usage of these header The following are further clarifications regarding usage of these
fields, as per [RFC7231] Sec. 8.3.1. All apply to both headers. header fields as per Section 8.3.1 of [RFC7231]. All apply to both
headers.
o This header field is a single value, not a list. * This header field is a single value, not a list.
o The header field is used only in responses to GET, HEAD and POST- * The header field is used only in responses to GET, HEAD, and POST-
as-GET requests, and only for MIME types that denote public key as-GET requests, and only for MIME types that denote public key
certificates. certificates.
o Header field semantics are independent of context. * Header field semantics are independent of context.
o The header field is not hop-by-hop. * The header field is not hop-by-hop.
o Intermediaries MAY insert or delete the value; * Intermediaries MAY insert or delete the value;
o If an intermediary inserts the value, it MUST ensure that the * If an intermediary inserts the value, it MUST ensure that the
newly added value matches the corresponding value in the newly added value matches the corresponding value in the
certificate. certificate.
o The header field is not appropriate for a Vary field. * The header field is not appropriate for a Vary field.
o The header field is allowed within message trailers. * The header field is allowed within message trailers.
o The header field is not appropriate within redirects. * The header field is not appropriate within redirects.
o The header field does not introduce additional security * The header field does not introduce additional security
considerations. It discloses in a simpler form information that considerations. It discloses in a simpler form information that
is already available inside the certificate. is already available inside the certificate.
To improve robustness, the next certificate MUST be made available by To improve robustness, the next certificate MUST be made available by
the ACME CA at the URL pointed by "star-certificate" at the latest the ACME CA at the URL indicated by "star-certificate" halfway
halfway through the lifetime of the currently active certificate. It through the lifetime of the currently active certificate at the
is worth noting that this has an implication in case of cancellation: latest. It is worth noting that this has an implication in case of
in fact, from the time the next certificate is made available, the cancellation; in fact, from the time the next certificate is made
cancellation is not completely effective until the "next" certificate available, the cancellation is not completely effective until the
also expires. To avoid the client accidentally entering a broken "next" certificate also expires. To avoid the client accidentally
state, the notBefore of the "next" certificate MUST be set so that entering a broken state, the notBefore of the "next" certificate MUST
the certificate is already valid when it is published at the "star- be set so that the certificate is already valid when it is published
certificate" URL. Note that the server might need to increase the at the "star-certificate" URL. Note that the server might need to
auto-renewal lifetime-adjust value to satisfy the latter requirement. increase the auto-renewal lifetime-adjust value to satisfy the latter
For a detailed description of the renewal scheduling logic, see requirement. For a detailed description of the renewal scheduling
Section 3.5. For further rationale on the need for adjusting the logic, see Section 3.5. For further rationale on the need for
certificate validity, see Section 4.1. adjusting the certificate validity, see Section 4.1.
The server MUST NOT issue any certificates for this Order with The server MUST NOT issue any certificates for this Order with
notAfter after the auto-renewal end-date. notAfter after the auto-renewal end-date.
For expired Orders, the server MUST respond with 403 (Forbidden) to For expired Orders, the server MUST respond with 403 (Forbidden) to
any requests to the star-certificate endpoint. The response SHOULD any requests to the star-certificate endpoint. The response SHOULD
provide additional information using a problem document [RFC7807] provide additional information using a problem document [RFC7807]
with type "urn:ietf:params:acme:error:autoRenewalExpired". Note that with type "urn:ietf:params:acme:error:autoRenewalExpired". Note that
the Order resource's state remains "valid", as per the base protocol. the Order resource's state remains "valid", as per the base protocol.
3.4. Negotiating an unauthenticated GET 3.4. Negotiating an Unauthenticated GET
In order to enable the name delegation workflow defined in In order to enable the name delegation workflow defined in
[I-D.ietf-acme-star-delegation] as well as to increase the [STAR-DELEGATION] and to increase the reliability of the STAR
reliability of the STAR ecosystem (see Section 4.3 for details), this ecosystem (see Section 4.3 for details), this document defines a
document defines a mechanism that allows a server to advertise mechanism that allows a server to advertise support for accessing
support for accessing star-certificate resources via unauthenticated star-certificate resources via unauthenticated GET (in addition to
GET (in addition to POST-as-GET), and a client to enable this service POST-as-GET), and a client to enable this service with per-Order
with per-Order granularity. granularity.
Specifically, a server states its availability to grant Specifically, a server states its availability to grant
unauthenticated access to a client's Order star-certificate by unauthenticated access to a client's Order star-certificate by
setting the allow-certificate-get attribute to true in the auto- setting the allow-certificate-get attribute to "true" in the auto-
renewal object of the meta field inside the Directory object: renewal object of the meta field inside the directory object:
o allow-certificate-get (optional, boolean): If this field is * allow-certificate-get (optional, boolean): If this field is
present and set to true, the server allows GET (and HEAD) requests present and set to "true", the server allows GET (and HEAD)
to star-certificate URLs. requests to star-certificate URLs.
A client states its desire to access the issued star-certificate via A client states its desire to access the issued star-certificate via
unauthenticated GET by adding an allow-certificate-get attribute to unauthenticated GET by adding an allow-certificate-get attribute to
the auto-renewal object of the payload of its newOrder request and the auto-renewal object of the payload of its newOrder request and
setting it to true. setting it to "true".
o allow-certificate-get (optional, boolean): If this field is * allow-certificate-get (optional, boolean): If this field is
present and set to true, the client requests the server to allow present and set to "true", the client requests the server to allow
unauthenticated GET (and HEAD) to the star-certificate associated unauthenticated GET (and HEAD) to the star-certificate associated
with this Order. with this Order.
If the server accepts the request, it MUST reflect the attribute If the server accepts the request, it MUST reflect the attribute
setting in the resulting Order object. setting in the resulting order object.
Note that even when the use of unauthenticated GET has been agreed, Note that even when the use of unauthenticated GET has been agreed
the server MUST also allow POST-as-GET requests to the star- upon, the server MUST also allow POST-as-GET requests to the star-
certificate resource. certificate resource.
3.5. Computing notBefore and notAfter of STAR Certificates 3.5. Computing notBefore and notAfter of STAR Certificates
We define "nominal renewal date" as the point in time when a new We define "nominal renewal date" as the point in time when a new
short-term certificate for a given STAR Order is due. Its cadence is short-term certificate for a given STAR Order is due. Its cadence is
a multiple of the Order's auto-renewal lifetime that starts with the a multiple of the Order's auto-renewal lifetime that starts with the
issuance of the first short-term certificate and is upper-bounded by issuance of the first short-term certificate and is upper-bounded by
the Order's auto-renewal end-date (Figure 7). the Order's auto-renewal end-date (Figure 7).
T - STAR Order's auto-renewal lifetime T - STAR Order's auto-renewal lifetime
end - STAR Order's auto-renewal end-date end - STAR Order's auto-renewal end-date
nrd[i] - nominal renewal date of the i-th STAR certificate nrd[i] - nominal renewal date of the i-th STAR certificate
.- T -. .- T -. .- T -. .__. .- T -. .- T -. .- T -. .__.
/ \ / \ / \ / end / \ / \ / \ / end
-----------o---------o---------o---------o----X-------> t -----------o---------o---------o---------o----X-------> t
nrd[0] nrd[1] nrd[2] nrd[3] nrd[0] nrd[1] nrd[2] nrd[3]
Figure 7: Nominal Renewal Date Figure 7: Nominal Renewal Date
The rules to determine the notBefore and notAfter values of the i-th The rules to determine the notBefore and notAfter values of the i-th
STAR certificate are as follows: STAR certificate are as follows:
notAfter = min(nrd[i] + T, end) notAfter = min(nrd[i] + T, end)
notBefore = nrd[i] - max(adjust_client, adjust_server) notBefore = nrd[i] - max(adjust_client, adjust_server)
Where "adjust_client" is the min between the auto-renewal lifetime- Where "adjust_client" is the minimum value between the auto-renewal
adjust value ("la"), optionally supplied by the client, and the auto- lifetime-adjust value ("la"), optionally supplied by the client, and
renewal lifetime of each short-term certificate ("T"); the auto-renewal lifetime of each short-term certificate ("T");
"adjust_server" is the amount of padding added by the ACME server to "adjust_server" is the amount of padding added by the ACME server to
make sure that all certificates being published are valid at the time make sure that all certificates being published are valid at the time
of publication. The server padding is a fraction f of T (i.e., f * T of publication. The server padding is a fraction (f) of T (i.e., f *
with .5 <= f < 1, see Section 3.3): T with .5 <= f < 1; see Section 3.3):
adjust_client = min(T, la) adjust_client = min(T, la)
adjust_server = f * T adjust_server = f * T
Note that the ACME server MUST NOT set the notBefore of the first Note that the ACME server MUST NOT set the notBefore of the first
STAR certificate to a date prior to the auto-renewal start-date. STAR certificate to a date prior to the auto-renewal start-date.
3.5.1. Example 3.5.1. Example
Given a server that intends to publish the next STAR certificate Given a server that intends to publish the next STAR certificate
skipping to change at page 15, line 22 skipping to change at line 630
with the following attributes: with the following attributes:
"auto-renewal": { "auto-renewal": {
"start-date": "2019-01-10T00:00:00Z", "start-date": "2019-01-10T00:00:00Z",
"end-date": "2019-01-20T00:00:00Z", "end-date": "2019-01-20T00:00:00Z",
"lifetime": 345600, // 4 days "lifetime": 345600, // 4 days
"lifetime-adjust": 259200 // 3 days "lifetime-adjust": 259200 // 3 days
} }
The amount of time that needs to be subtracted from each nominal The amount of time that needs to be subtracted from each nominal
renewal date is 3 days - i.e., max(min(345600, 259200), 345600 * .5). renewal date is 3 days, i.e., max(min(345600, 259200), 345600 * .5).
The notBefore and notAfter of each short-term certificate are: The notBefore and notAfter of each short-term certificate are:
+----------------------+----------------------+ +----------------------+----------------------+
| notBefore | notAfter | | notBefore | notAfter |
+----------------------+----------------------+ +======================+======================+
| 2019-01-10T00:00:00Z | 2019-01-14T00:00:00Z | | 2019-01-10T00:00:00Z | 2019-01-14T00:00:00Z |
+----------------------+----------------------+
| 2019-01-11T00:00:00Z | 2019-01-18T00:00:00Z | | 2019-01-11T00:00:00Z | 2019-01-18T00:00:00Z |
+----------------------+----------------------+
| 2019-01-15T00:00:00Z | 2019-01-20T00:00:00Z | | 2019-01-15T00:00:00Z | 2019-01-20T00:00:00Z |
+----------------------+----------------------+ +----------------------+----------------------+
Table 1
The value of the notBefore is also the time at which the client The value of the notBefore is also the time at which the client
should expect the new certificate to be available from the star- should expect the new certificate to be available from the star-
certificate endpoint. certificate endpoint.
4. Operational Considerations 4. Operational Considerations
4.1. The Meaning of "Short Term" and the Impact of Skewed Clocks 4.1. The Meaning of "Short Term" and the Impact of Skewed Clocks
"Short Term" is a relative concept, therefore trying to define a cut- "Short Term" is a relative concept; therefore, trying to define a
off point that works in all cases would be a useless exercise. In cutoff point that works in all cases would be a useless exercise. In
practice, the expected lifetime of a STAR certificate will be counted practice, the expected lifetime of a STAR certificate will be counted
in minutes, hours or days, depending on different factors: the in minutes, hours, or days, depending on different factors: the
underlying requirements for revocation, how much clock underlying requirements for revocation, how much clock
synchronization is expected among relying parties and the issuing CA, synchronization is expected among relying parties and the issuing CA,
etc. etc.
Nevertheless, this section attempts to provide reasonable suggestions Nevertheless, this section attempts to provide reasonable suggestions
for the Web use case, informed by current operational and research for the Web use case, informed by current operational and research
experience. experience.
Acer et al. [Acer] find that one of the main causes of "HTTPS error" Acer et al. [ACER] find that one of the main causes of "HTTPS error"
warnings in browsers is misconfigured client clocks. In particular, warnings in browsers is misconfigured client clocks. In particular,
they observe that roughly 95% of the "severe" clock skews - the 6.7% they observe that roughly 95% of the "severe" clock skews -- the 6.7%
of clock-related breakage reports which account for clients that are of clock-related breakage reports that account for clients that are
more than 24 hours behind - happen to be within 6-7 days. more than 24 hours behind -- happen to be within 6-7 days.
In order to avoid these spurious warnings about a not (yet) valid In order to avoid these spurious warnings about a not yet valid
server certificate, site owners could use the auto-renewal lifetime- server certificate, site owners could use the auto-renewal lifetime-
adjust attribute to control the effective lifetime of their Web adjust attribute to control the effective lifetime of their Web-
facing certificates. The exact number depends on the percentage of facing certificates. The exact number depends on the percentage of
the "clock-skewed" population that the site owner expects to protect the "clock-skewed" population that the site owner expects to protect
- 5 days cover 97.3%, 7 days cover 99.6% - as well as the nominal -- 5 days cover 97.3%, 7 days cover 99.6% -- as well as the nominal
auto-renewal lifetime of the STAR Order. Note that exact choice is auto-renewal lifetime of the STAR Order. Note that exact choice is
also likely to depend on the kinds of client that is prevalent for a also likely to depend on the kinds of client that are prevalent for a
given site or app - for example, Android and Mac OS clients are known given site or app -- for example, Android and Mac OS clients are
to behave better than Windows clients. These considerations are known to behave better than Windows clients. These considerations
clearly out of scope of the present document. are clearly out of scope of this document.
In terms of security, STAR certificates and certificates with OCSP In terms of security, STAR certificates and certificates with the
must-staple [RFC7633] can be considered roughly equivalent if the Online Certificate Status Protocol (OCSP) "must-staple" flag asserted
STAR certificate's and the OCSP response's lifetimes are the same. [RFC7633] can be considered roughly equivalent if the STAR
Given OCSP responses can be cached on average for 4 days [Stark], it certificate's and the OCSP response's lifetimes are the same. (Here,
is RECOMMENDED that a STAR certificate that is used on the Web has an "must-staple" refers to a certificate carrying a TLS feature
"effective" lifetime (excluding any adjustment to account for clock extension with the "status_request" extension identifier [RFC6066].)
skews) no longer than 4 days. Given OCSP responses can be cached, on average, for 4 days [STARK],
it is RECOMMENDED that a STAR certificate that is used on the Web has
an "effective" lifetime (excluding any adjustment to account for
clock skews) no longer than 4 days.
4.2. Impact on Certificate Transparency (CT) Logs 4.2. Impact on Certificate Transparency (CT) Logs
Even in the highly unlikely case STAR becomes the only certificate Even in the highly unlikely case STAR becomes the only certificate
issuance model, discussion with the IETF TRANS Working Group and issuance model, discussion with the IETF TRANS Working Group and
Certificate Transparency (CT) logs implementers suggests that implementers of Certificate Transparency (CT) logs suggests that
existing CT Log Server implementations are capable of sustaining the existing CT Log server implementations are capable of sustaining the
resulting 100-fold increase in ingestion rate. Additionally, such a resulting 100-fold increase in ingestion rate. Additionally, such a
future, higher load could be managed with a variety of techniques future higher load could be managed with a variety of techniques
(e.g., sharding by modulo of certificate hash, using "smart" load- (e.g., sharding by modulo of certificate hash, using "smart" load-
balancing CT proxies, etc.). With regards to the increase in the log balancing CT proxies, etc.). With regards to the increase in the log
size, current CT log growth is already being managed with schemes size, current CT log growth is already being managed with schemes
like Chrome's Log Policy [OBrien] which allow Operators to define like Chrome's Log Policy [OBRIEN], which allow Operators to define
their log life-cycle; and allowing the CAs, User Agents, Monitors, their log life cycle, as well as allowing the CAs, User Agents,
and any other interested entities to build-in support for that life- Monitors, and any other interested entities to build in support for
cycle ahead of time. that life cycle ahead of time.
4.3. HTTP Caching and Dependability 4.3. HTTP Caching and Dependability
When using authenticated POST-as-GET, the HTTPS endpoint from where When using authenticated POST-as-GET, the HTTPS endpoint from where
the STAR certificate is fetched can't be easily replicated by an on- the STAR certificate is fetched can't be easily replicated by an on-
path HTTP cache. Reducing the caching properties of the protocol path HTTP cache. Reducing the caching properties of the protocol
makes STAR clients increasingly dependent on the ACME server makes STAR clients increasingly dependent on the ACME server
availability. This might be problematic given the relatively high availability. This might be problematic given the relatively high
rate of client-server interactions in a STAR ecosystem and especially rate of client-server interactions in a STAR ecosystem, especially
when multiple endpoints (e.g., a high number of CDN edge nodes) end when multiple endpoints (e.g., a high number of CDN edge nodes) end
up requesting the same certificate. Clients and servers should up requesting the same certificate. Clients and servers should
consider using the mechanism described in Section 3.4 to mitigate the consider using the mechanism described in Section 3.4 to mitigate the
risk. risk.
When using unauthenticated GET to fetch the STAR certificate, the When using unauthenticated GET to fetch the STAR certificate, the
server SHALL use the appropriate cache directives to set the server SHALL use the appropriate cache directives to set the
freshness lifetime of the response (Section 5.2 of [RFC7234]) such freshness lifetime of the response (Section 5.2 of [RFC7234]) such
that on-path caches will consider it stale before or at the time its that on-path caches will consider it stale before or at the time its
effective lifetime is due to expire. effective lifetime is due to expire.
5. Implementation Status 5. IANA Considerations
Note to RFC Editor: please remove this section before publication,
including the reference to [RFC7942] and
[I-D.sheffer-acme-star-request].
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
According to [RFC7942], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
5.1. Overview
The implementation is constructed around 3 elements: STAR Client for
the Name Delegation Client (NDC), STAR Proxy for IdO and ACME Server
for CA. The communication between them is over an IP network and the
HTTPS protocol.
The software of the implementation is available at:
https://github.com/mami-project/lurk
The following subsections offer a basic description, detailed
information is available in https://github.com/mami-
project/lurk/blob/master/proxySTAR_v2/README.md
5.1.1. ACME Server with STAR extension
This is a fork of the Let's Encrypt Boulder project that implements
an ACME compliant CA. It includes modifications to extend the ACME
protocol as it is specified in this draft, to support recurrent
Orders and cancelling Orders.
The implementation understands the new "recurrent" attributes as part
of the Certificate issuance in the POST request for a new resource.
An additional process "renewalManager.go" has been included in
parallel that reads the details of each recurrent request,
automatically produces a "cron" Linux based task that issues the
recurrent certificates, until the lifetime ends or the Order is
canceled. This process is also in charge of maintaining a fixed URI
to enable the NDC to download certificates, unlike Boulder's regular
process of producing a unique URI per certificate.
5.1.2. STAR Proxy
The STAR Proxy has a double role as ACME client and STAR Server. The
former is a fork of the EFF Certbot project that implements an ACME
compliant client with the STAR extension. The latter is a basic HTTP
REST API server.
The STAR Proxy understands the basic API request with a server. The
current implementation of the API is defined in draft-ietf-acme-star-
01. Registration or Order cancellation triggers the modified Certbot
client that requests, or cancels, the recurrent generation of
certificates using the STAR extension over ACME protocol. The URI
with the location of the recurrent certificate is delivered to the
STAR client as a response.
5.2. Level of Maturity
This is a prototype.
5.3. Coverage
A STAR Client is not included in this implementation, but done by
direct HTTP request with any open HTTP REST API tool. This is
expected to be covered as part of the [I-D.sheffer-acme-star-request]
implementation.
This implementation completely covers STAR Proxy and ACME Server with
STAR extension.
5.4. Version Compatibility
The implementation is compatible with version draft-ietf-acme-star-
01. The implementation is based on the Boulder and Certbot code
release from 7-Aug-2017.
5.5. Licensing
This implementation inherits the Boulder license (Mozilla Public
License 2.0) and Certbot license (Apache License Version 2.0 ).
5.6. Implementation experience
To prove the concept all the implementation has been done with a
self-signed CA, to avoid impact on real domains. To be able to do it
we use the FAKE_DNS property of Boulder and static /etc/hosts entries
with domains names. Nonetheless this implementation should run with
real domains.
Most of the implementation has been made to avoid deep changes inside
of Boulder or Certbot, for example, the recurrent certificates
issuance by the CA is based on an external process that auto-
configures the standard Linux "cron" daemon in the ACME CA server.
The reference setup recommended is one physical host with 3 virtual
machines, one for each of the 3 components (client, proxy and server)
and the connectivity based on host bridge.
Network security is not enabled (iptables default policies are
"accept" and all rules removed) in this implementation to simplify
and test the protocol.
5.7. Contact Information
See author details below.
6. IANA Considerations
[[RFC Editor: please replace XXXX below by the RFC number.]]
6.1. New Registries 5.1. New Registries
This document requests that IANA create the following new registries: Per this document, IANA has created the following new registries:
o ACME Order Auto Renewal Fields (Section 6.4) * ACME Order Auto-Renewal Fields (Section 5.4)
o ACME Directory Metadata Auto Renewal Fields (Section 6.6) * ACME Directory Metadata Auto-Renewal Fields (Section 5.6)
All of these registries are administered under a Specification These registries are administered under a Specification Required
Required policy [RFC8126]. policy [RFC8126].
6.2. New Error Types 5.2. New Error Types
This document adds the following entries to the ACME Error Type Per this document, IANA has added the following entries to the "ACME
registry: Error Types" registry:
+-----------------------------------+-------------------+-----------+ +-----------------------------------+-------------------+-----------+
| Type | Description | Reference | | Type | Description | Reference |
+===================================+===================+===========+
| autoRenewalCanceled | The short-term | RFC 8739 |
| | certificate is | |
| | no longer | |
| | available | |
| | because the | |
| | auto-renewal | |
| | Order has been | |
| | explicitly | |
| | canceled by | |
| | the IdO | |
+-----------------------------------+-------------------+-----------+ +-----------------------------------+-------------------+-----------+
| autoRenewalCanceled | The short-term | RFC XXXX | | autoRenewalExpired | The short-term | RFC 8739 |
| | certificate is no | | | | certificate is | |
| | longer available | | | | no longer | |
| | because the auto- | | | | available | |
| | renewal Order has | | | | because the | |
| | been explicitly | | | | auto-renewal | |
| | canceled by the | | | | Order has | |
| | IdO | |
| autoRenewalExpired | The short-term | RFC XXXX |
| | certificate is no | |
| | longer available | |
| | because the auto- | |
| | renewal Order has | |
| | expired | | | | expired | |
| autoRenewalCancellationInvalid | A request to | RFC XXXX | +-----------------------------------+-------------------+-----------+
| | cancel a auto- | | | autoRenewalCancellationInvalid | A request to | RFC 8739 |
| | renewal Order | | | | cancel an | |
| | that is not in | | | | auto-renewal | |
| | state "valid" has | | | | Order that is | |
| | been received | | | | not in state | |
| autoRenewalRevocationNotSupported | A request to | RFC XXXX | | | "valid" has | |
| | revoke a auto- | |
| | renewal Order has | |
| | been received | | | | been received | |
+-----------------------------------+-------------------+-----------+ +-----------------------------------+-------------------+-----------+
| autoRenewalRevocationNotSupported | A request to | RFC 8739 |
| | revoke an | |
| | auto-renewal | |
| | Order has been | |
| | received | |
+-----------------------------------+-------------------+-----------+
6.3. New fields in Order Objects Table 2
This document adds the following entries to the ACME Order Object 5.3. New Fields in Order Objects
Fields registry:
Per this document, IANA has added the following entries to the "ACME
Order Object Fields" registry:
+------------------+------------+--------------+-----------+ +------------------+------------+--------------+-----------+
| Field Name | Field Type | Configurable | Reference | | Field Name | Field Type | Configurable | Reference |
+==================+============+==============+===========+
| auto-renewal | object | true | RFC 8739 |
+------------------+------------+--------------+-----------+ +------------------+------------+--------------+-----------+
| auto-renewal | object | true | RFC XXXX | | star-certificate | string | false | RFC 8739 |
| star-certificate | string | false | RFC XXXX |
+------------------+------------+--------------+-----------+ +------------------+------------+--------------+-----------+
6.4. Fields in the "auto-renewal" Object within an Order Object Table 3
The "ACME Order Auto Renewal Fields" registry lists field names that 5.4. Fields in the "auto-renewal" Object within an Order Object
The "ACME Order Auto-Renewal Fields" registry lists field names that
are defined for use in the JSON object included in the "auto-renewal" are defined for use in the JSON object included in the "auto-renewal"
field of an ACME order object. field of an ACME order object.
Template: Template:
o Field name: The string to be used as a field name in the JSON * Field name: The string to be used as a field name in the JSON
object object
o Field type: The type of value to be provided, e.g., string, * Field type: The type of value to be provided, e.g., string,
boolean, array of string boolean, array of string
o Configurable: Boolean indicating whether the server should accept * Configurable: Boolean indicating whether the server should accept
values provided by the client values provided by the client
o Reference: Where this field is defined * Reference: Where this field is defined
Initial contents: The fields and descriptions defined in Initial contents: The fields and descriptions defined in
Section 3.1.1. Section 3.1.1.
+-----------------------+------------+--------------+-----------+ +-----------------------+------------+--------------+-----------+
| Field Name | Field Type | Configurable | Reference | | Field Name | Field Type | Configurable | Reference |
+=======================+============+==============+===========+
| start-date | string | true | RFC 8739 |
+-----------------------+------------+--------------+-----------+ +-----------------------+------------+--------------+-----------+
| start-date | string | true | RFC XXXX | | end-date | string | true | RFC 8739 |
| end-date | string | true | RFC XXXX | +-----------------------+------------+--------------+-----------+
| lifetime | integer | true | RFC XXXX | | lifetime | integer | true | RFC 8739 |
| lifetime-adjust | integer | true | RFC XXXX | +-----------------------+------------+--------------+-----------+
| allow-certificate-get | boolean | true | RFC XXXX | | lifetime-adjust | integer | true | RFC 8739 |
+-----------------------+------------+--------------+-----------+
| allow-certificate-get | boolean | true | RFC 8739 |
+-----------------------+------------+--------------+-----------+ +-----------------------+------------+--------------+-----------+
6.5. New fields in the "meta" Object within a Directory Object Table 4
This document adds the following entry to the ACME Directory Metadata 5.5. New Fields in the "meta" Object within a Directory Object
Fields:
Per this document, IANA has added the following entry to the "ACME
Directory Metadata Fields":
+--------------+------------+-----------+ +--------------+------------+-----------+
| Field Name | Field Type | Reference | | Field Name | Field Type | Reference |
+--------------+------------+-----------+ +==============+============+===========+
| auto-renewal | object | RFC XXXX | | auto-renewal | object | RFC 8739 |
+--------------+------------+-----------+ +--------------+------------+-----------+
6.6. Fields in the "auto-renewal" Object within a Directory Metadata Table 5
5.6. Fields in the "auto-renewal" Object within a Directory Metadata
Object Object
The "ACME Directory Metadata Auto Renewal Fields" registry lists The "ACME Directory Metadata Auto-Renewal Fields" registry lists
field names that are defined for use in the JSON object included in field names that are defined for use in the JSON object included in
the "auto-renewal" field of an ACME directory "meta" object. the "auto-renewal" field of an ACME directory "meta" object.
Template: Template:
o Field name: The string to be used as a field name in the JSON * Field name: The string to be used as a field name in the JSON
object object
o Field type: The type of value to be provided, e.g., string, * Field type: The type of value to be provided, e.g., string,
boolean, array of string boolean, array of string
o Reference: Where this field is defined * Reference: Where this field is defined
Initial contents: The fields and descriptions defined in Section 3.2. Initial contents: The fields and descriptions defined in Section 3.2.
+-----------------------+------------+-----------+ +-----------------------+------------+-----------+
| Field Name | Field Type | Reference | | Field Name | Field Type | Reference |
+=======================+============+===========+
| min-lifetime | integer | RFC 8739 |
+-----------------------+------------+-----------+ +-----------------------+------------+-----------+
| min-lifetime | integer | RFC XXXX | | max-duration | integer | RFC 8739 |
| max-duration | integer | RFC XXXX | +-----------------------+------------+-----------+
| allow-certificate-get | boolean | RFC XXXX | | allow-certificate-get | boolean | RFC 8739 |
+-----------------------+------------+-----------+ +-----------------------+------------+-----------+
6.7. Cert-Not-Before and Cert-Not-After HTTP Headers Table 6
The "Message Headers" registry should be updated with the following 5.7. Cert-Not-Before and Cert-Not-After HTTP Headers
The "Message Headers" registry has been updated with the following
additional values: additional values:
+-------------------+----------+----------+-----------------------+ +-------------------+----------+----------+-----------------------+
| Header Field Name | Protocol | Status | Reference | | Header Field Name | Protocol | Status | Reference |
+===================+==========+==========+=======================+
| Cert-Not-Before | http | standard | RFC 8739, Section 3.3 |
+-------------------+----------+----------+-----------------------+ +-------------------+----------+----------+-----------------------+
| Cert-Not-Before | http | standard | RFC XXXX, Section 3.3 | | Cert-Not-After | http | standard | RFC 8739, Section 3.3 |
| Cert-Not-After | http | standard | RFC XXXX, Section 3.3 |
+-------------------+----------+----------+-----------------------+ +-------------------+----------+----------+-----------------------+
7. Security Considerations Table 7
7.1. No revocation 6. Security Considerations
STAR certificates eliminate an important security feature of PKI 6.1. No Revocation
STAR certificates eliminate an important security feature of PKI,
which is the ability to revoke certificates. Revocation allows the which is the ability to revoke certificates. Revocation allows the
administrator to limit the damage done by a rogue node or an administrator to limit the damage done by a rogue node or an
adversary who has control of the private key. With STAR adversary who has control of the private key. With STAR
certificates, expiration replaces revocation so there is potential certificates, expiration replaces revocation so there is potential
for lack of timeliness in the revocation taking effect. To that end, for lack of timeliness in the revocation taking effect. To that end,
see also the discussion on clock skew in Section 4.1. see also the discussion on clock skew in Section 4.1.
It should be noted that revocation also has timeliness issues, It should be noted that revocation also has timeliness issues because
because both CRLs and OCSP responses have nextUpdate fields that tell both Certificate Revocation Lists (CRLs) and OCSP responses have
relying parties (RPs) how long they should trust this revocation nextUpdate fields that tell relying parties (RPs) how long they
data. These fields are typically set to hours, days, or even weeks should trust this revocation data. These fields are typically set to
in the future. Any revocation that happens before the time in hours, days, or even weeks in the future. Any revocation that
nextUpdate goes unnoticed by the RP. happens before the time in nextUpdate goes unnoticed by the RP.
One situation where the lack of explicit revocation could create a One situation where the lack of explicit revocation could create a
security risk to the IdO is when the Order is created with start-date security risk to the IdO is when the Order is created with a start-
some appreciable amount of time in the future. Recall that when date of some appreciable amount of time in the future. Recall that
authorizations have been fulfilled, the Order moves to the "valid" when authorizations have been fulfilled, the Order moves to the
state and the star-certificate endpoint is populated with the first "valid" state and the star-certificate endpoint is populated with the
cert (Figure 4). So, if an attacker manages to get hold of the first cert (Figure 4). So, if an attacker manages to get hold of the
private key as well as of the first (post-dated) certificate, there private key as well as the first (post-dated) certificate, there is a
is a time window in the future when they will be able to successfully time window in the future when they will be able to successfully
impersonate the IdO. Note that cancellation is pointless in this impersonate the IdO. Note that cancellation is pointless in this
case. In order to mitigate the described threat, it is RECOMMENDED case. In order to mitigate the described threat, it is RECOMMENDED
that IdO place their Orders at a time that is close to the Order's that IdO place their Orders at a time that is close to the Order's
start-date. start-date.
More discussion of the security of STAR certificates is available in More discussion of the security of STAR certificates is available in
[Topalovic]. [TOPALOVIC].
7.2. Denial of Service Considerations 6.2. Denial-of-Service Considerations
STAR adds a new attack vector that increases the threat of denial of STAR adds a new attack vector that increases the threat of denial-of-
service attacks, caused by the change to the CA's behavior. Each service attacks, caused by the change to the CA's behavior. Each
STAR request amplifies the resource demands upon the CA, where one STAR request amplifies the resource demands upon the CA, where one
Order produces not one, but potentially dozens or hundreds of Order produces not one but potentially dozens or hundreds of
certificates, depending on the auto-renewal "lifetime" parameter. An certificates, depending on the auto-renewal "lifetime" parameter. An
attacker can use this property to aggressively reduce the auto- attacker can use this property to aggressively reduce the auto-
renewal "lifetime" (e.g. 1 sec.) jointly with other ACME attack renewal "lifetime" (e.g., 1 second) jointly with other ACME attack
vectors identified in Sec. 10 of [RFC8555]. Other collateral impact vectors identified in Section 10 of [RFC8555]. Other collateral
is related to the certificate endpoint resource where the client can impact is related to the certificate endpoint resource where the
retrieve the certificates periodically. If this resource is external client can retrieve the certificates periodically. If this resource
to the CA (e.g. a hosted web server), the previous attack will be is external to the CA (e.g., a hosted web server), the previous
reflected to that resource. attack will be reflected to that resource.
Mitigation recommendations from ACME still apply, but some of them Mitigation recommendations from ACME still apply, but some of them
need to be adjusted. For example, applying rate limiting to the need to be adjusted. For example, applying rate limiting to the
initial request, by the nature of the auto-renewal behavior cannot initial request, due to the nature of the auto-renewal behavior,
solve the above problem. The CA server needs complementary cannot solve the above problem. The CA server needs complementary
mitigation and specifically, it SHOULD enforce a minimum value on mitigation, and specifically, it SHOULD enforce a minimum value on
auto-renewal "lifetime". Alternatively, the CA can set an internal auto-renewal "lifetime". Alternatively, the CA can set a rate limit
certificate generation processes rate limit. Note that this limit for internal certificate generation processes. Note that this limit
has to take account of already-scheduled renewal issuances as well as has to take account of already scheduled renewal issuances as well as
new incoming requests. new incoming requests.
7.3. Privacy Considerations 6.3. Privacy Considerations
In order to avoid correlation of certificates by account, if In order to avoid correlation of certificates by account, if
unauthenticated GET is negotiated (Section 3.4) the recommendation in unauthenticated GET is negotiated (Section 3.4), the recommendation
Section 10.5 of [RFC8555] regarding the choice of URL structure in Section 10.5 of [RFC8555] regarding the choice of URL structure
applies, i.e. servers SHOULD choose URLs of certificate resources in applies, i.e., servers SHOULD choose URLs of certificate resources in
a non-guessable way, for example using capability URLs a non-guessable way, for example, using capability URLs
[W3C.WD-capability-urls-20140218]. [W3C.CAPABILITY-URLS].
8. Acknowledgments
This work is partially supported by the European Commission under
Horizon 2020 grant agreement no. 688421 Measurement and Architecture
for a Middleboxed Internet (MAMI). This support does not imply
endorsement.
Thanks to Ben Kaduk, Richard Barnes, Roman Danyliw, Jon Peterson,
Eric Rescorla, Ryan Sleevi, Sean Turner, Alexey Melnikov, Adam Roach,
Martin Thomson and Mehmet Ersue for helpful comments and discussions
that have shaped this document.
9. References 7. References
9.1. Normative References 7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>. <https://www.rfc-editor.org/info/rfc3339>.
skipping to change at page 25, line 19 skipping to change at line 1004
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J. [RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
Kasten, "Automatic Certificate Management Environment Kasten, "Automatic Certificate Management Environment
(ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019, (ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019,
<https://www.rfc-editor.org/info/rfc8555>. <https://www.rfc-editor.org/info/rfc8555>.
9.2. Informative References 7.2. Informative References
[Acer] Acer, M., Stark, E., Felt, A., Fahl, S., Bhargava, R., [ACER] Acer, M.E., Stark, E., Felt, A.P., Fahl, S., Bhargava, R.,
Dev, B., Braithwaite, M., Sleevi, R., and P. Tabriz, Dev, B., Braithwaite, M., Sleevi, R., and P. Tabriz,
"Where the Wild Warnings Are: Root Causes of Chrome HTTPS "Where the Wild Warnings Are: Root Causes of Chrome HTTPS
Certificate Errors", DOI 10.1145/3133956.3134007, 2017, Certificate Errors", DOI 10.1145/3133956.3134007, October
<https://acmccs.github.io/papers/p1407-acerA.pdf>. 2017, <https://acmccs.github.io/papers/p1407-acerA.pdf>.
[I-D.ietf-acme-star-delegation]
Sheffer, Y., Lopez, D., Pastor, A., and T. Fossati, "An
ACME Profile for Generating Delegated STAR Certificates",
draft-ietf-acme-star-delegation-01 (work in progress),
August 2019.
[I-D.nir-saag-star]
Nir, Y., Fossati, T., Sheffer, Y., and T. Eckert,
"Considerations For Using Short Term Certificates", draft-
nir-saag-star-01 (work in progress), March 2018.
[I-D.sheffer-acme-star-request]
Sheffer, Y., Lopez, D., Dios, O., Pastor, A., and T.
Fossati, "Generating Certificate Requests for Short-Term,
Automatically-Renewed (STAR) Certificates", draft-sheffer-
acme-star-request-02 (work in progress), June 2018.
[OBrien] O'Brien, D. and R. Sleevi, "Chromium Certificate [OBRIEN] O'Brien, D. and R. Sleevi, "Chromium Certificate
Transparency Log Policy", 2017, Transparency Policy", April 2017,
<https://github.com/chromium/ct-policy>. <https://github.com/chromium/ct-policy>.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC6066, January 2011,
<https://www.rfc-editor.org/info/rfc6066>.
[RFC7633] Hallam-Baker, P., "X.509v3 Transport Layer Security (TLS) [RFC7633] Hallam-Baker, P., "X.509v3 Transport Layer Security (TLS)
Feature Extension", RFC 7633, DOI 10.17487/RFC7633, Feature Extension", RFC 7633, DOI 10.17487/RFC7633,
October 2015, <https://www.rfc-editor.org/info/rfc7633>. October 2015, <https://www.rfc-editor.org/info/rfc7633>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running [SHORT-TERM-CERTS]
Code: The Implementation Status Section", BCP 205, Nir, Y., Fossati, T., Sheffer, Y., and T. Eckert,
RFC 7942, DOI 10.17487/RFC7942, July 2016, "Considerations For Using Short Term Certificates", Work
<https://www.rfc-editor.org/info/rfc7942>. in Progress, Internet-Draft, draft-nir-saag-star-01, 5
March 2018,
<https://tools.ietf.org/html/draft-nir-saag-star-01>.
[Stark] Stark, E., Huang, L., Israni, D., Jackson, C., and D. [STAR-DELEGATION]
Sheffer, Y., Lopez, D., Pastor, A., and T. Fossati, "An
ACME Profile for Generating Delegated STAR Certificates",
Work in Progress, Internet-Draft, draft-ietf-acme-star-
delegation-03, 8 March 2020, <https://tools.ietf.org/html/
draft-ietf-acme-star-delegation-03>.
[STARK] Stark, E., Huang, L.S., Israni, D., Jackson, C., and D.
Boneh, "The case for prefetching and prevalidating TLS Boneh, "The case for prefetching and prevalidating TLS
server certificates", 2012, server certificates", February 2012,
<http://crypto.stanford.edu/~dabo/pubs/abstracts/ssl- <https://crypto.stanford.edu/~dabo/pubs/abstracts/ssl-
prefetch.html>. prefetch.html>.
[Topalovic] [TOPALOVIC]
Topalovic, E., Saeta, B., Huang, L., Jackson, C., and D. Topalovic, E., Saeta, B., Huang, L.S., Jackson, C., and D.
Boneh, "Towards Short-Lived Certificates", 2012, Boneh, "Towards Short-Lived Certificates", 2012,
<http://www.ieee-security.org/TC/W2SP/2012/papers/ <https://www.ieee-security.org/TC/W2SP/2012/papers/
w2sp12-final9.pdf>. w2sp12-final9.pdf>.
[W3C.WD-capability-urls-20140218] [W3C.CAPABILITY-URLS]
Tennison, J., "Good Practices for Capability URLs", World Tennison, J., "Good Practices for Capability URLs", W3C
Wide Web Consortium WD WD-capability-urls-20140218, First Public Working Draft, Latest version available at
February 2014, <https://www.w3.org/TR/capability-urls/>, February 2014,
<http://www.w3.org/TR/2014/WD-capability-urls-20140218>. <https://www.w3.org/TR/2014/WD-capability-urls-20140218>.
Appendix A. Document History
[[Note to RFC Editor: please remove before publication.]]
A.1. draft-ietf-acme-star-11
o One more nit re: random URL
A.2. draft-ietf-acme-star-10
IESG processing:
o More clarity on IANA registration (Alexey);
o HTTP header requirements adjustments (Adam);
o Misc editorial (Ben)
A.3. draft-ietf-acme-star-09
Richard and Ryan's review resulted in the following updates:
o STAR Order and Directory Meta attributes renamed slightly and
grouped under two brand new "auto-renewal" objects;
o IANA registration updated accordingly (note that two new
registries have been added as a consequence);
o Unbounded pre-dating of certificates removed so that STAR certs
are never issued with their notBefore in the past;
o Changed "recurrent" to "autoRenewal" in error codes;
o Changed "recurrent" to "auto-renewal" in reference to Orders;
o Added operational considerations for HTTP caches.
A.4. draft-ietf-acme-star-08
o Improved text on interaction with CT Logs, responding to Mehmet
Ersue's review.
A.5. draft-ietf-acme-star-07
o Changed the HTTP headers names and clarified the IANA
registration, following feedback from the IANA expert reviewer
A.6. draft-ietf-acme-star-06
o Roman's AD review
A.7. draft-ietf-acme-star-05
o EKR's AD review
o A detailed example of the timing of certificate issuance and
predating
o Added an explicit client-side parameter for predating
o Security considerations around unauthenticated GET
A.8. draft-ietf-acme-star-04
o WG last call comments by Sean Turner
o revokeCert interface handling
o Allow negotiating plain-GET for certs
o In STAR Orders, use star-certificate instead of certificate
A.9. draft-ietf-acme-star-03
o Clock skew considerations
o Recommendations for "short" in the Web use case
o CT log considerations
A.10. draft-ietf-acme-star-02
o Discovery of STAR capabilities via the directory object
o Use the more generic term Identifier Owner (IdO) instead of Domain
Name Owner (DNO)
o More precision about what goes in the order
o Detail server side behavior on cancellation
A.11. draft-ietf-acme-star-01
o Generalized the introduction, separating out the specifics of
CDNs.
o Clean out LURK-specific text.
o Using a POST to ensure cancellation is authenticated.
o First and last date of recurrent cert, as absolute dates.
Validity of certs in seconds.
o Use RFC7807 "Problem Details" in error responses.
o Add IANA considerations.
o Changed the document's title.
A.12. draft-ietf-acme-star-00
o Initial working group version.
o Removed the STAR interface, the protocol between NDC and DNO.
What remains is only the extended ACME protocol.
A.13. draft-sheffer-acme-star-02
o Using a more generic term for the delegation client, NDC.
o Added an additional use case: public cloud services.
o More detail on ACME authorization.
A.14. draft-sheffer-acme-star-01
o A terminology section.
o Some cleanup.
A.15. draft-sheffer-acme-star-00
o Renamed draft to prevent confusion with other work in this space. Acknowledgments
o Added an initial STAR protocol: a REST API.
o Discussion of CDNI use cases.
A.16. draft-sheffer-acme-star-lurk-00 This work is partially supported by the European Commission under
Horizon 2020 grant agreement no. 688421 Measurement and Architecture
for a Middleboxed Internet (MAMI). This support does not imply
endorsement.
o Initial version. Thanks to Ben Kaduk, Richard Barnes, Roman Danyliw, Jon Peterson,
Eric Rescorla, Ryan Sleevi, Sean Turner, Alexey Melnikov, Adam Roach,
Martin Thomson, and Mehmet Ersue for helpful comments and discussions
that have shaped this document.
Authors' Addresses Authors' Addresses
Yaron Sheffer Yaron Sheffer
Intuit Intuit
EMail: yaronf.ietf@gmail.com Email: yaronf.ietf@gmail.com
Diego Lopez Diego Lopez
Telefonica I+D Telefonica I+D
EMail: diego.r.lopez@telefonica.com Email: diego.r.lopez@telefonica.com
Oscar Gonzalez de Dios Oscar Gonzalez de Dios
Telefonica I+D Telefonica I+D
EMail: oscar.gonzalezdedios@telefonica.com Email: oscar.gonzalezdedios@telefonica.com
Antonio Agustin Pastor Perales Antonio Agustin Pastor Perales
Telefonica I+D Telefonica I+D
EMail: antonio.pastorperales@telefonica.com Email: antonio.pastorperales@telefonica.com
Thomas Fossati Thomas Fossati
ARM ARM
EMail: thomas.fossati@arm.com Email: thomas.fossati@arm.com
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