draft-ietf-ace-oauth-authz-02.txt   draft-ietf-ace-oauth-authz-03.txt 
ACE Working Group L. Seitz ACE Working Group L. Seitz
Internet-Draft SICS Internet-Draft SICS
Intended status: Standards Track G. Selander Intended status: Standards Track G. Selander
Expires: December 12, 2016 Ericsson Expires: April 15, 2017 Ericsson
E. Wahlstroem E. Wahlstroem
Nexus Technology
S. Erdtman S. Erdtman
Spotify AB Spotify AB
H. Tschofenig H. Tschofenig
ARM Ltd. ARM Ltd.
June 10, 2016 October 12, 2016
Authentication and Authorization for Constrained Environments (ACE) Authentication and Authorization for Constrained Environments (ACE)
draft-ietf-ace-oauth-authz-02 draft-ietf-ace-oauth-authz-03
Abstract Abstract
This specification defines the ACE framework for authentication and This specification defines a framework for authentication and
authorization in Internet of Things (IoT) deployments. The ACE authorization in Internet of Things (IoT) environments. The
framework is based on a set of building blocks including OAuth 2.0 framework is based on a set of building blocks including OAuth 2.0
and CoAP, thus making a well-known and widely used authorization and CoAP, thus making a well-known and widely used authorization
solution suitable for IoT devices. Existing specifications are used solution suitable for IoT devices. Existing specifications are used
where possible, but where the limitations of IoT devices require it, where possible, but where the constraints of IoT devices require it,
profiles and extensions are provided. extensions are added and profiles are defined.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 12, 2016. This Internet-Draft will expire on April 15, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 24 skipping to change at page 2, line 24
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. OAuth 2.0 . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. OAuth 2.0 . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. CoAP . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2. CoAP . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Protocol Interactions . . . . . . . . . . . . . . . . . . . . 9 4. Protocol Interactions . . . . . . . . . . . . . . . . . . . . 9
5. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6. The 'Token' Resource . . . . . . . . . . . . . . . . . . . . 14 6. The 'Token' Endpoint . . . . . . . . . . . . . . . . . . . . 14
6.1. Client-to-AS Request . . . . . . . . . . . . . . . . . . 14 6.1. Client-to-AS Request . . . . . . . . . . . . . . . . . . 14
6.2. AS-to-Client Response . . . . . . . . . . . . . . . . . . 17 6.2. AS-to-Client Response . . . . . . . . . . . . . . . . . . 17
6.3. Error Response . . . . . . . . . . . . . . . . . . . . . 18 6.3. Error Response . . . . . . . . . . . . . . . . . . . . . 18
6.4. New Request and Response Parameters . . . . . . . . . . . 18 6.4. New Request and Response Parameters . . . . . . . . . . . 18
6.4.1. Grant Type . . . . . . . . . . . . . . . . . . . . . 19 6.4.1. Audience . . . . . . . . . . . . . . . . . . . . . . 18
6.4.2. Token Type and Algorithms . . . . . . . . . . . . . . 19 6.4.2. Grant Type . . . . . . . . . . . . . . . . . . . . . 19
6.4.3. Profile . . . . . . . . . . . . . . . . . . . . . . . 20 6.4.3. Token Type . . . . . . . . . . . . . . . . . . . . . 19
6.4.4. Confirmation . . . . . . . . . . . . . . . . . . . . 20 6.4.4. Profile . . . . . . . . . . . . . . . . . . . . . . . 19
6.5. Mapping parameters to CBOR . . . . . . . . . . . . . . . 22 6.4.5. Confirmation . . . . . . . . . . . . . . . . . . . . 20
7. The 'Introspect' Resource . . . . . . . . . . . . . . . . . . 22 6.5. Mapping parameters to CBOR . . . . . . . . . . . . . . . 21
7. The 'Introspect' Endpoint . . . . . . . . . . . . . . . . . . 22
7.1. RS-to-AS Request . . . . . . . . . . . . . . . . . . . . 23 7.1. RS-to-AS Request . . . . . . . . . . . . . . . . . . . . 23
7.2. AS-to-RS Response . . . . . . . . . . . . . . . . . . . . 23 7.2. AS-to-RS Response . . . . . . . . . . . . . . . . . . . . 23
7.3. Error Response . . . . . . . . . . . . . . . . . . . . . 24 7.3. Error Response . . . . . . . . . . . . . . . . . . . . . 24
7.4. Client Token . . . . . . . . . . . . . . . . . . . . . . 25 7.4. Client Token . . . . . . . . . . . . . . . . . . . . . . 25
7.5. Mapping Introspection parameters to CBOR . . . . . . . . 26 7.5. Mapping Introspection parameters to CBOR . . . . . . . . 26
8. The Access Token . . . . . . . . . . . . . . . . . . . . . . 27 8. The Access Token . . . . . . . . . . . . . . . . . . . . . . 27
8.1. The 'Authorization Information' Resource . . . . . . . . 27 8.1. The 'Authorization Information' Endpoint . . . . . . . . 28
8.2. Token Expiration . . . . . . . . . . . . . . . . . . . . 28 8.2. Token Expiration . . . . . . . . . . . . . . . . . . . . 28
9. Security Considerations . . . . . . . . . . . . . . . . . . . 28 9. Security Considerations . . . . . . . . . . . . . . . . . . . 29
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
10.1. OAuth Introspection Response Parameter Registration . . 29 10.1. OAuth Introspection Response Parameter Registration . . 30
10.2. OAuth Parameter Registration . . . . . . . . . . . . . . 30 10.2. OAuth Parameter Registration . . . . . . . . . . . . . . 31
10.3. OAuth Access Token Types . . . . . . . . . . . . . . . . 30 10.3. OAuth Access Token Types . . . . . . . . . . . . . . . . 31
10.4. Token Type Mappings . . . . . . . . . . . . . . . . . . 30 10.4. Token Type Mappings . . . . . . . . . . . . . . . . . . 32
10.4.1. Registration Template . . . . . . . . . . . . . . . 30 10.4.1. Registration Template . . . . . . . . . . . . . . . 32
10.4.2. Initial Registry Contents . . . . . . . . . . . . . 31 10.4.2. Initial Registry Contents . . . . . . . . . . . . . 32
10.5. JSON Web Token Claims . . . . . . . . . . . . . . . . . 31 10.5. CBOR Web Token Claims . . . . . . . . . . . . . . . . . 32
10.6. ACE Profile Registry . . . . . . . . . . . . . . . . . . 31 10.6. ACE Profile Registry . . . . . . . . . . . . . . . . . . 33
10.6.1. Registration Template . . . . . . . . . . . . . . . 31 10.6.1. Registration Template . . . . . . . . . . . . . . . 33
10.7. OAuth Parameter Mappings Registry . . . . . . . . . . . 32 10.7. OAuth Parameter Mappings Registry . . . . . . . . . . . 33
10.7.1. Registration Template . . . . . . . . . . . . . . . 32 10.7.1. Registration Template . . . . . . . . . . . . . . . 33
10.7.2. Initial Registry Contents . . . . . . . . . . . . . 32 10.7.2. Initial Registry Contents . . . . . . . . . . . . . 34
10.8. Introspection Resource CBOR Mappings Registry . . . . . 34 10.8. Introspection Endpoint CBOR Mappings Registry . . . . . 36
10.8.1. Registration Template . . . . . . . . . . . . . . . 35 10.8.1. Registration Template . . . . . . . . . . . . . . . 36
10.8.2. Initial Registry Contents . . . . . . . . . . . . . 35 10.8.2. Initial Registry Contents . . . . . . . . . . . . . 36
10.9. CoAP Option Number Registration . . . . . . . . . . . . 37 10.9. CoAP Option Number Registration . . . . . . . . . . . . 38
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 37 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 39
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 38 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 39
12.1. Normative References . . . . . . . . . . . . . . . . . . 38 12.1. Normative References . . . . . . . . . . . . . . . . . . 39
12.2. Informative References . . . . . . . . . . . . . . . . . 38 12.2. Informative References . . . . . . . . . . . . . . . . . 40
Appendix A. Design Justification . . . . . . . . . . . . . . . . 40 Appendix A. Design Justification . . . . . . . . . . . . . . . . 42
Appendix B. Roles and Responsibilites . . . . . . . . . . . . . 42 Appendix B. Roles and Responsibilites . . . . . . . . . . . . . 44
Appendix C. Deployment Examples . . . . . . . . . . . . . . . . 44 Appendix C. Requirements on Profiles . . . . . . . . . . . . . . 46
C.1. Local Token Validation . . . . . . . . . . . . . . . . . 44 Appendix D. Deployment Examples . . . . . . . . . . . . . . . . 46
C.2. Introspection Aided Token Validation . . . . . . . . . . 48 D.1. Local Token Validation . . . . . . . . . . . . . . . . . 47
Appendix D. Document Updates . . . . . . . . . . . . . . . . . . 51 D.2. Introspection Aided Token Validation . . . . . . . . . . 50
D.1. Version -01 to -02 . . . . . . . . . . . . . . . . . . . 52 Appendix E. Document Updates . . . . . . . . . . . . . . . . . . 54
D.2. Version -00 to -01 . . . . . . . . . . . . . . . . . . . 52 E.1. Version -02 to -03 . . . . . . . . . . . . . . . . . . . 54
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 53 E.2. Version -01 to -02 . . . . . . . . . . . . . . . . . . . 54
E.3. Version -00 to -01 . . . . . . . . . . . . . . . . . . . 55
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 56
1. Introduction 1. Introduction
Authorization is the process for granting approval to an entity to Authorization is the process for granting approval to an entity to
access a resource [RFC4949]. The authorization task itself can best access a resource [RFC4949]. The authorization task itself can best
be described as granting access to a requesting client, for a be described as granting access to a requesting client, for a
resource hosted on a device, the resource server (RS). This exchange resource hosted on a device, the resource server (RS). This exchange
is mediated by one or multiple authorization servers (AS). Managing is mediated by one or multiple authorization servers (AS). Managing
authorization for a large number of devices and users is a complex authorization for a large number of devices and users is a complex
task. task.
We envision that end consumers and enterprises will manage access to
resources on, or produced by, Internet of Things (IoT) devices in the
same style as they do today with data, services and applications on
the Web or with their mobile devices. This desire will increase with
the number of exposed services and capabilities provided by
applications hosted on the IoT devices.
While prior work on authorization solutions for the Web and for the While prior work on authorization solutions for the Web and for the
mobile environment also applies to the IoT environment many IoT mobile environment also applies to the IoT environment many IoT
devices are constrained, for example in terms of processing devices are constrained, for example in terms of processing
capabilities, available memory, etc. For web applications on capabilities, available memory, etc. For web applications on
constrained nodes this specification makes use of CoAP [RFC7252]. constrained nodes this specification makes use of CoAP [RFC7252].
A detailed treatment of constraints can be found in [RFC7228], and A detailed treatment of constraints can be found in [RFC7228], and
the different IoT deployments present a continuous range of device the different IoT deployments present a continuous range of device
and network capabilities. Taking energy consumption as an example: and network capabilities. Taking energy consumption as an example:
At one end there are energy-harvesting or battery powered devices At one end there are energy-harvesting or battery powered devices
which have a tight power budget, on the other end there are mains- which have a tight power budget, on the other end there are mains-
powered devices, and all levels in between. powered devices, and all levels in between.
Hence, IoT devices may be very different in terms of available Hence, IoT devices may be very different in terms of available
processing and message exchange capabilities and there is a need to processing and message exchange capabilities and there is a need to
support many different authorization use cases [RFC7744]. support many different authorization use cases [RFC7744].
This specification describes a framework for authentication and This specification describes a framework for authentication and
authorization in constrained environments (ACE) built on re-use of authorization in constrained environments (ACE) built on re-use of
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is not used in this memo. is not used in this memo.
Since this specification focuses on the problem of access control to Since this specification focuses on the problem of access control to
resources, we simplify the actors by assuming that the client resources, we simplify the actors by assuming that the client
authorization server (CAS) functionality is not stand-alone but authorization server (CAS) functionality is not stand-alone but
subsumed by either the authorization server or the client (see subsumed by either the authorization server or the client (see
section 2.2 in [I-D.ietf-ace-actors]). section 2.2 in [I-D.ietf-ace-actors]).
3. Overview 3. Overview
This specification describes the ACE framework for authorization in This specification defines the ACE framework for authorization in the
the Internet of Things consisting of a set of building blocks. Internet of Things environment. It consists of a set of building
blocks.
The basic block is the OAuth 2.0 [RFC6749] framework, which enjoys The basic block is the OAuth 2.0 [RFC6749] framework, which enjoys
widespread deployment. Many IoT devices can support OAuth 2.0 widespread deployment. Many IoT devices can support OAuth 2.0
without any additional extensions, but for certain constrained without any additional extensions, but for certain constrained
settings additional profiling is needed. settings additional profiling is needed.
Another building block is the lightweight web transfer protocol CoAP Another building block is the lightweight web transfer protocol CoAP
[RFC7252] for those communication environments where HTTP is not [RFC7252] for those communication environments where HTTP is not
appropriate. CoAP typically runs on top of UDP which further reduces appropriate. CoAP typically runs on top of UDP which further reduces
overhead and message exchanges. While this specification defines overhead and message exchanges. While this specification defines
extensions for the use of OAuth over CoAP, we do envision further extensions for the use of OAuth over CoAP, we do envision further
underlying protocols to be supported in the future, such as MQTT or underlying protocols to be supported in the future, such as HTTP/2,
QUIC. MQTT and QUIC.
A third building block is CBOR [RFC7049] for encodings where JSON A third building block is CBOR [RFC7049] for encodings where JSON
[RFC7159] is not sufficiently compact. CBOR is a binary encoding [RFC7159] is not sufficiently compact. CBOR is a binary encoding
designed for small code and message size, which may be used for designed for small code and message size, which may be used for
encoding of self contained tokens, and also for encoding CoAP POST encoding of self contained tokens, and also for encoding CoAP POST
parameters and CoAP responses. parameters and CoAP responses.
A fourth building block is the compact CBOR-based secure message A fourth building block is the compact CBOR-based secure message
format COSE [I-D.ietf-cose-msg], which enables application layer format COSE [I-D.ietf-cose-msg], which enables application layer
security as an alternative or complement to transport layer security security as an alternative or complement to transport layer security
(DTLS [RFC6347] or TLS [RFC5246]). COSE is used to secure self (DTLS [RFC6347] or TLS [RFC5246]). COSE is used to secure self
contained tokens such as proof-of-possession (PoP) tokens contained tokens such as proof-of-possession (PoP) tokens, which is
[I-D.ietf-oauth-pop-architecture], which is an extension to the OAuth an extension to the OAuth access tokens, and "client tokens" which
access tokens, and "client tokens" which are defined in this are defined in this framework (see Section 7.4). The default access
framework (see Section 7.4). The default access token format is token format is defined in CBOR web token (CWT)
defined in CBOR web token (CWT) [I-D.ietf-ace-cbor-web-token]. [I-D.ietf-ace-cbor-web-token]. Application layer security for CoAP
Application layer security for CoAP using COSE can be provided with using COSE can be provided with OSCOAP
OSCOAP [I-D.selander-ace-object-security]. [I-D.selander-ace-object-security].
With the building blocks listed above, solutions satisfying various With the building blocks listed above, solutions satisfying various
IoT device and network constraints are possible. A list of IoT device and network constraints are possible. A list of
constraints is described in detail in RFC 7228 [RFC7228] and a constraints is described in detail in RFC 7228 [RFC7228] and a
description of how the building blocks mentioned above relate to the description of how the building blocks mentioned above relate to the
various constraints can be found in Appendix A. various constraints can be found in Appendix A.
Luckily, not every IoT device suffers from all constraints. The ACE Luckily, not every IoT device suffers from all constraints. The ACE
framework nevertheless takes all these aspects into account and framework nevertheless takes all these aspects into account and
allows several different deployment variants to co-exist rather than allows several different deployment variants to co-exist rather than
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client. client.
Access tokens can have different formats, and various methods of Access tokens can have different formats, and various methods of
utilization (e.g., cryptographic properties) based on the security utilization (e.g., cryptographic properties) based on the security
requirements of the given deployment. requirements of the given deployment.
Proof of Possession Tokens: Proof of Possession Tokens:
An access token may be bound to a cryptographic key, which is then An access token may be bound to a cryptographic key, which is then
used by an RS to authenticate requests from a client. Such tokens used by an RS to authenticate requests from a client. Such tokens
are called proof-of-possession tokens (or PoP tokens) are called proof-of-possession tokens (or PoP tokens).
[I-D.ietf-oauth-pop-architecture].
The proof-of-possession (PoP) security concept assumes that the AS The proof-of-possession (PoP) security concept assumes that the AS
acts as a trusted third party that binds keys to access tokens. acts as a trusted third party that binds keys to access tokens.
These so called PoP keys are then used by the client to These so called PoP keys are then used by the client to
demonstrate the possession of the secret to the RS when accessing demonstrate the possession of the secret to the RS when accessing
the resource. The RS, when receiving an access token, needs to the resource. The RS, when receiving an access token, needs to
verify that the key used by the client matches the one included in verify that the key used by the client matches the one bound to
the access token. When this specification uses the term "access the access token. When this specification uses the term "access
token" it is assumed to be a PoP token unless specifically stated token" it is assumed to be a PoP token unless specifically stated
otherwise. otherwise.
The key bound to the access token (aka PoP key) may be based on The key bound to the access token (aka PoP key) may be based on
symmetric as well as on asymmetric cryptography. The appropriate symmetric as well as on asymmetric cryptography. The appropriate
choice of security depends on the constraints of the IoT devices choice of security depends on the constraints of the IoT devices
as well as on the security requirements of the use case. as well as on the security requirements of the use case.
Symmetric PoP key: The AS generates a random symmetric PoP key, Symmetric PoP key: The AS generates a random symmetric PoP key.
encrypts it for the RS and includes it inside an access token. The key is either stored to be returned on introspection calls
The PoP key is also encrypted for the client and sent together or encrypted and included in the access token. The PoP key is
with the access token to the client.> also encrypted for the client and sent together with the access
token to the client.
Asymmetric PoP key: An asymmetric key pair is generated on the Asymmetric PoP key: An asymmetric key pair is generated on the
client and the public key is sent to the AS (if it does not client and the public key is sent to the AS (if it does not
already have knowledge of the client's public key). already have knowledge of the client's public key).
Information about the public key, which is the PoP key in this Information about the public key, which is the PoP key in this
case, is then included inside the access token and sent back to case, is either stored to be returned on introspection calls or
the requesting client. The RS can identify the client's public included inside the access token and sent back to the
key from the information in the token, which allows the client requesting client. The RS can identify the client's public key
to use the corresponding private key for the proof of from the information in the token, which allows the client to
possession. use the corresponding private key for the proof of possession.
The access token is protected against modifications using a MAC or The access token is protected against modifications using a MAC or
a digital signature, which is added by the AS. The choice of PoP a digital signature, which is added by the AS. The choice of PoP
key does not necessarily imply a specific credential type for the key does not necessarily imply a specific credential type for the
integrity protection of the token. More information about PoP integrity protection of the token.
tokens can be found in [I-D.ietf-oauth-pop-architecture].
Scopes and Permissions: Scopes and Permissions:
In OAuth 2.0, the client specifies the type of permissions it is In OAuth 2.0, the client specifies the type of permissions it is
seeking to obtain (via the scope parameter) in the access request. seeking to obtain (via the scope parameter) in the access token
In turn, the AS may use the scope response parameter to inform the request. In turn, the AS may use the scope response parameter to
client of the scope of the access token issued. As the client inform the client of the scope of the access token issued. As the
could be a constrained device as well, this specification uses client could be a constrained device as well, this specification
CBOR encoded messages for CoAP, defined in Section 5, to request uses CBOR encoded messages for CoAP, defined in Section 5, to
scopes and to be informed what scopes the access token was request scopes and to be informed what scopes the access token was
actually authorized for by the AS. actually authorized for by the AS.
The values of the scope parameter are expressed as a list of The values of the scope parameter are expressed as a list of
space- delimited, case-sensitive strings, with a semantic that is space- delimited, case-sensitive strings, with a semantic that is
well-known to the AS and the RS. More details about the concept well-known to the AS and the RS. More details about the concept
of scopes is found under Section 3.3 in [RFC6749]. of scopes is found under Section 3.3 in [RFC6749].
Claims: Claims:
Information carried in the access token, called claims, is in the Information carried in the access token or returned from
form of type-value pairs. An access token may, for example, introspection, called claims, is in the form of type-value pairs.
include a claim identifying the AS that issued the token (via the An access token may, for example, include a claim identifying the
"iss" claim) and what audience the access token is intended for AS that issued the token (via the "iss" claim) and what audience
(via the "aud" claim). The audience of an access token can be a the access token is intended for (via the "aud" claim). The
specific resource or one or many resource servers. The resource audience of an access token can be a specific resource or one or
owner policies influence what claims are put into the access token many resource servers. The resource owner policies influence what
by the authorization server. claims are put into the access token by the authorization server.
While the structure and encoding of the access token varies While the structure and encoding of the access token varies
throughout deployments, a standardized format has been defined throughout deployments, a standardized format has been defined
with the JSON Web Token (JWT) [RFC7519] where claims are encoded with the JSON Web Token (JWT) [RFC7519] where claims are encoded
as a JSON object. In [I-D.ietf-ace-cbor-web-token] an equivalent as a JSON object. In [I-D.ietf-ace-cbor-web-token] an equivalent
format using CBOR encoding (CWT) has been defined. format using CBOR encoding (CWT) has been defined.
Introspection: Introspection:
Introspection is a method for a resource server to query the Introspection is a method for a resource server to query the
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specifically designed for constrained environments. CoAP typically specifically designed for constrained environments. CoAP typically
uses datagram-oriented transport, such as UDP, where reordering and uses datagram-oriented transport, such as UDP, where reordering and
loss of packets can occur. A security solution need to take the loss of packets can occur. A security solution need to take the
latter aspects into account. latter aspects into account.
While HTTP uses headers and query-strings to convey additional While HTTP uses headers and query-strings to convey additional
information about a request, CoAP encodes such information in so- information about a request, CoAP encodes such information in so-
called 'options'. called 'options'.
CoAP supports application-layer fragmentation of the CoAP payloads CoAP supports application-layer fragmentation of the CoAP payloads
through blockwise transfers [I-D.ietf-core-block]. However, block- through blockwise transfers [RFC7959]. However, block-wise transfer
wise transfer does not increase the size limits of CoAP options, does not increase the size limits of CoAP options, therefore data
therefore data encoded in options has to be kept small. encoded in options has to be kept small.
Transport layer security for CoAP can be provided by DTLS 1.2 Transport layer security for CoAP can be provided by DTLS 1.2
[RFC6347] or TLS 1.2 [RFC5246]. CoAP defines a number of proxy [RFC6347] or TLS 1.2 [RFC5246]. CoAP defines a number of proxy
operations which requires transport layer security to be terminated operations which requires transport layer security to be terminated
at the proxy. One approach for protecting CoAP communication end-to- at the proxy. One approach for protecting CoAP communication end-to-
end through proxies, and also to support security for CoAP over end through proxies, and also to support security for CoAP over
different transport in a uniform way, is to provide security on different transport in a uniform way, is to provide security on
application layer using an object-based security mechanism such as application layer using an object-based security mechanism such as
CBOR Encoded Message Syntax [I-D.ietf-cose-msg]. COSE [I-D.ietf-cose-msg].
One application of COSE is OSCOAP [I-D.selander-ace-object-security], One application of COSE is OSCOAP [I-D.selander-ace-object-security],
which provides end-to-end confidentiality, integrity and replay which provides end-to-end confidentiality, integrity and replay
protection, and a secure binding between CoAP request and response protection, and a secure binding between CoAP request and response
messages. In OSCOAP, the CoAP messages are wrapped in COSE objects messages. In OSCOAP, the CoAP messages are wrapped in COSE objects
and sent using CoAP. and sent using CoAP.
4. Protocol Interactions 4. Protocol Interactions
The ACE framework is based on the OAuth 2.0 protocol interactions The ACE framework is based on the OAuth 2.0 protocol interactions
using the /token and /introspect endpoints. A client obtains an using the /token and /introspect endpoints. A client obtains an
access token from an AS using the /token endpoint and subsequently access token from an AS using the /token endpoint and subsequently
presents the access token to a RS to gain access to a protected presents the access token to a RS to gain access to a protected
resource. The RS, after receiving an access token, may present it to resource. The RS, after receiving an access token, may present it to
the AS via the /introspect endpoint to get information about the the AS via the /introspect endpoint to get information about the
access token. In other deployments the RS may process the access access token. In other deployments the RS may process the access
token locally without the need to contact an AS. These interactions token locally without the need to contact an AS. These interactions
are shown in Figure 1. An overview of various OAuth concepts is are shown in Figure 1. An overview of various OAuth concepts is
provided in Section 3.1. provided in Section 3.1.
The OAuth 2.0 framework defines a number of "protocol flows" via
grant types, which have been extended further with extensions to
OAuth 2.0 (such as RFC 7521 [RFC7521] and
[I-D.ietf-oauth-device-flow]). What grant types works best depends
on the usage scenario and RFC 7744 [RFC7744] describes many different
IoT use cases but there two preferred grant types, namely the
Authorization Code Grant (described in Section 4.1 of RFC 7521) and
the Client Credentials Grant (described in Section 4.4 of RFC 7521).
The Authorization Code Grant is a good fit for use with apps running
on smart phones and tablets that request access to IoT devices, a
common scenario in the smart home environment, where users need to go
through an authentication and authorization phase (at least during
the initial setup phase). The native apps guidelines described in
[I-D.ietf-oauth-native-apps] are applicable to this use case. The
Client Credential Grant is a good fit for use with IoT devices where
the OAuth client itself is constraint. In such a case the resource
owner or another person on his or her behalf have arranged with the
authorization server out-of-band, which is often accomplished using
an commissioning tool.
The consent of the resource owner, for giving a client access to a The consent of the resource owner, for giving a client access to a
protected resource, can be pre-configured authorization policies or protected resource, can be provided dynamically as in the traditional
dynamically at the time when the request is sent. The resource owner OAuth flows, or it could be pre-configured by the resource owner as
and the requesting party (i.e. client owner) are not shown in authorization policies at the AS, which the AS evaluates when a token
Figure 1. request arrives. The resource owner and the requesting party (i.e.
client owner) are not shown in Figure 1.
This framework supports a wide variety of communication security This framework supports a wide variety of communication security
mechanisms between the ACE entities, such as client, AS, and RS. We mechanisms between the ACE entities, such as client, AS, and RS. We
assume that the client has been registered (also called enrolled or assume that the client has been registered (also called enrolled or
onboarded) to an AS using a mechanism defined outside the scope of onboarded) to an AS using a mechanism defined outside the scope of
this document. In practice, various techniques for onboarding have this document. In practice, various techniques for onboarding have
been used, such as factory-based provisioning or the use of been used, such as factory-based provisioning or the use of
commissioning tools. Regardless of the onboarding technique, this commissioning tools. Regardless of the onboarding technique, this
registration procedure implies that the client and the AS share registration procedure implies that the client and the AS share
credentials, and configuration parameters. These credentials are credentials, and configuration parameters. These credentials are
skipping to change at page 10, line 32 skipping to change at page 10, line 49
At the start of the protocol there is an optional discovery step At the start of the protocol there is an optional discovery step
where the client discovers the resource server and the resources this where the client discovers the resource server and the resources this
server hosts. In this step the client might also determine what server hosts. In this step the client might also determine what
permissions are needed to access the protected resource. The permissions are needed to access the protected resource. The
detailed procedures for this discovery process may be defined in an detailed procedures for this discovery process may be defined in an
ACE profile and depend on the protocols being used and the specific ACE profile and depend on the protocols being used and the specific
deployment environment. deployment environment.
In Bluetooth Low Energy, for example, advertisements are broadcasted In Bluetooth Low Energy, for example, advertisements are broadcasted
by a peripheral, including information about the primary services. by a peripheral, including information about the primary services.
In CoAP, as a second example, a client can makes a request to In CoAP, as a second example, a client can make a request to "/.well-
"/.well-known/core" to obtain information about available resources, known/core" to obtain information about available resources, which
which are returned in a standardized format as described in are returned in a standardized format as described in [RFC6690].
[RFC6690].
+--------+ +---------------+ +--------+ +---------------+
| |---(A)-- Token Request ------->| | | |---(A)-- Token Request ------->| |
| | | Authorization | | | | Authorization |
| |<--(B)-- Access Token ---------| Server | | |<--(B)-- Access Token ---------| Server |
| | + Client Information | | | | + RS Information | |
| | +---------------+ | | +---------------+
| | ^ | | | ^ |
| | Introspection Request (D)| | | | Introspection Request (D)| |
| Client | | | | Client | | |
| | Response + Client Token | |(E) | | Response + Client Token | |(E)
| | | v | | | v
| | +--------------+ | | +--------------+
| |---(C)-- Token + Request ----->| | | |---(C)-- Token + Request ----->| |
| | | Resource | | | | Resource |
| |<--(F)-- Protected Resource ---| Server | | |<--(F)-- Protected Resource ---| Server |
skipping to change at page 11, line 39 skipping to change at page 11, line 39
Section 3.1 for a short description) wherein the AS binds a key to Section 3.1 for a short description) wherein the AS binds a key to
an access token. The client may include permissions it seeks to an access token. The client may include permissions it seeks to
obtain, and information about the credentials it wants to use obtain, and information about the credentials it wants to use
(e.g., symmetric/asymmetric cryptography or a reference to a (e.g., symmetric/asymmetric cryptography or a reference to a
specific credential). specific credential).
Access Token Response (B): Access Token Response (B):
If the AS successfully processes the request from the client, it If the AS successfully processes the request from the client, it
returns an access token. It also returns various parameters, returns an access token. It also returns various parameters,
referred as "Client Information". In addition to the response referred as "RS Information". In addition to the response
parameters defined by OAuth 2.0 and the PoP token extension, parameters defined by OAuth 2.0 and the PoP token extension,
further response parameters, such as information on which profile further response parameters, such as information on which profile
the client should use with the resource server(s). More the client should use with the resource server(s). More
information about these parameters can be found in in Section 6.4. information about these parameters can be found in in Section 6.4.
Resource Request (C): Resource Request (C):
The client interacts with the RS to request access to the The client interacts with the RS to request access to the
protected resource and provides the access token. The protocol to protected resource and provides the access token. The protocol to
use between the client and the RS is not restricted to CoAP. use between the client and the RS is not restricted to CoAP.
HTTP, HTTP/2, QUIC, MQTT, Bluetooth Low Energy, etc., are also HTTP, HTTP/2, QUIC, MQTT, Bluetooth Low Energy, etc., are also
viable candidates. viable candidates.
Depending on the device limitations and the selected protocol this Depending on the device limitations and the selected protocol this
exchange may be split up into two parts: exchange may be split up into two parts:
(1) the client sends the access token containing, or (1) the client sends the access token containing, or
referencing, the authorization information to the RS, that may referencing, the authorization information to the RS, that may
be used for subsequent resource requests by the client, and be used for subsequent resource requests by the client, and
(2) the client makes the resource access request, using the (2) the client makes the resource access request, using the
communication security protocol and other client information communication security protocol and other RS Information
obtained from the AS. obtained from the AS.
The Client and the RS mutually authenticate using the security The Client and the RS mutually authenticate using the security
protocol specified in the profile (see step B) and the keys protocol specified in the profile (see step B) and the keys
obtained in the access token or the client information or the obtained in the access token or the RS Information or the client
client token. The RS verifies that the token is integrity token. The RS verifies that the token is integrity protected by
protected by the AS and compares the claims contained in the the AS and compares the claims contained in the access token with
access token with the resource request. If the RS is online, the resource request. If the RS is online, validation can be
validation can be handed over to the AS using token introspection handed over to the AS using token introspection (see messages D
(see messages D and E) over HTTP or CoAP, in which case the and E) over HTTP or CoAP, in which case the different parts of
different parts of step C may be interleaved with introspection. step C may be interleaved with introspection.
Token Introspection Request (D): Token Introspection Request (D):
A resource server may be configured to introspect the access token A resource server may be configured to introspect the access token
by including it in a request to the /introspect endpoint at that by including it in a request to the /introspect endpoint at that
AS. Token introspection over CoAP is defined in Section 7 and for AS. Token introspection over CoAP is defined in Section 7 and for
HTTP in [RFC7662]. HTTP in [RFC7662].
Note that token introspection is an optional step and can be Note that token introspection is an optional step and can be
omitted if the token is self-contained and the resource server is omitted if the token is self-contained and the resource server is
skipping to change at page 13, line 22 skipping to change at page 13, line 22
For IoT we cannot generally assume that the client and RS are part For IoT we cannot generally assume that the client and RS are part
of a common key infrastructure, so the AS provisions credentials of a common key infrastructure, so the AS provisions credentials
or associated information to allow mutual authentication. These or associated information to allow mutual authentication. These
credentials need to be provided to the parties before or during credentials need to be provided to the parties before or during
the authentication protocol is executed, and may be re-used for the authentication protocol is executed, and may be re-used for
subsequent token requests. subsequent token requests.
Proof-of-Possession Proof-of-Possession
The ACE framework by default implements proof-of-possession for The ACE framework by default implements proof-of-possession for
access tokens, i.e. that the authenticated token holder is bound access tokens, i.e. that the token holder can prove being a holder
to the token. The binding is provided by the "cnf" claim of the key bound to the token. The binding is provided by the
indicating what key is used for mutual authentication. If clients "cnf" claim indicating what key is used for mutual authentication.
need to update a token, e.g. to get additional rights, they can If clients need to update a token, e.g. to get additional rights,
request that the AS binds the new access token to the same they can request that the AS binds the new access token to the
credential as the previous token. same credential as the previous token.
ACE Profile Negotiation ACE Profiles
The client or RS may be limited in the encodings or protocols it The client or RS may be limited in the encodings or protocols it
supports. To support a variety of different deployment settings, supports. To support a variety of different deployment settings,
specific interactions between client and RS are defined in an ACE specific interactions between client and RS are defined in an ACE
profile. The ACE framework supports the negotiation of different profile. In ACE framework the AS is expected to manage the
ACE profiles between client and AS using the "profile" parameter matching of compatible profile choices between a client and an RS.
in the token request and token response. The AS informs the client of the selected profile using the
"profile" parameter in the token request and token response.
OAuth 2.0 requires the use of TLS both to protect the communication OAuth 2.0 requires the use of TLS both to protect the communication
between AS and client when requesting an access token and between AS between AS and client when requesting an access token; between client
and RS for introspection. In constrained settings TLS is not always and RS when accessing a resource and between AS and RS for
feasible, or desirable. Nevertheless it is REQUIRED that the data introspection. In constrained settings TLS is not always feasible,
exchanged with the AS is encrypted and integrity protected. It is or desirable. Nevertheless it is REQUIRED that the data exchanged
furthermore REQUIRED that the AS and the endpoint communicating with with the AS is encrypted and integrity protected. It is furthermore
it (client or RS) perform mutual authentication. REQUIRED that the AS and the endpoint communicating with it (client
or RS) perform mutual authentication.
Profiles are expected to specify the details of how this is done, Profiles are expected to specify the details of how this is done,
depending e.g. on the communication protocol and the credentials used depending e.g. on the communication protocol and the credentials used
by the client or the RS. by the client or the RS.
In OAuth 2.0 the communication with the Token and the Introspection In OAuth 2.0 the communication with the Token and the Introspection
resources at the AS is assumed to be via HTTP and may use Uri-query endpoints at the AS is assumed to be via HTTP and may use Uri-query
parameters. This framework RECOMMENDS to use CoAP instead and parameters. This framework RECOMMENDS to use CoAP instead and
RECOMMENDS the use of the following alternative instead of Uri-query RECOMMENDS the use of the following alternative instead of Uri-query
parameters: The sender (client or RS) encodes the parameters of its parameters: The sender (client or RS) encodes the parameters of its
request as a CBOR map and submits that map as the payload of the POST request as a CBOR map and submits that map as the payload of the POST
request. The Content-format MUST be "application/cbor" in that case. request. The Content-format depends on the security applied to the
content and must be specified by the corresponding profile.
The OAuth 2.0 AS uses a JSON structure in the payload of its The OAuth 2.0 AS uses a JSON structure in the payload of its
responses both to client and RS. This framework RECOMMENDS the use responses both to client and RS. This framework RECOMMENDS the use
of CBOR [RFC7049] instead. The requesting device can explicitly of CBOR [RFC7049] instead. The requesting device can explicitly
request this encoding by setting the CoAP Accept option in the request this encoding by setting the CoAP Accept option in the
request to "application/cbor". request to "application/cbor". Depending on the profile, the content
may arrive in a different format wrapping a CBOR payload.
6. The 'Token' Resource 6. The 'Token' Endpoint
In plain OAuth 2.0 the AS provides the /token resource for submitting In plain OAuth 2.0 the AS provides the /token endpoint for submitting
access token requests. This framework extends the functionality of access token requests. This framework extends the functionality of
the /token resource, giving the AS the possibility to help client and the /token endpoint, giving the AS the possibility to help client and
RS to establish shared keys or to exchange their public keys. RS to establish shared keys or to exchange their public keys.
Furthermore this framework defines encodings using CoAP and CBOR,
instead of HTTP and JSON.
Communication between the client and the token resource at the AS Communication between the client and the /token endpoint at the AS
MUST be integrity protected and encrypted. Furthermore AS and client MUST be integrity protected and encrypted. Furthermore AS and client
MUST perform mutual authentication. Profiles of this framework are MUST perform mutual authentication. Profiles of this framework are
expected to specify how authentication and communication security is expected to specify how authentication and communication security is
implemented. implemented.
The figures of this section uses CBOR diagnostic notation without the The figures of this section uses CBOR diagnostic notation without the
integer abbreviations for the parameters or their values for better integer abbreviations for the parameters or their values for better
readability. readability.
6.1. Client-to-AS Request 6.1. Client-to-AS Request
When requesting an access token from the AS, the client MAY include The client sends a CoAP POST request to the token endpoint at the AS,
the following parameters in the request in addition to the ones the profile is expected to specify the Content-Type and wrapping of
required or optional according to the OAuth 2.0 specification the payload. The content of the request consists of the parameters
[RFC6749]: specified in section 4 of the OAuth 2.0 specification [RFC6749]
encoded as a CBOR map.
token_type
OPTIONAL. See Section 6.4 for more details.
alg In addition to these parameters, this framework defines the following
OPTIONAL. See Section 6.4 for more details. parameters for requesting an access token from a /token endpoint:
profile aud
OPTIONAL. This indicates the profile that the client would like OPTIONAL. Specifies the audience for which the client is
to use with the RS. See Section 6.4 for more details on the requesting an access token. If this parameter is missing it is
formatting of this parameter. If the RS cannot support the assumed that the client and the AS have a pre-established
requested profile, the AS MUST reply with an error message. understanding of the audience that an access token should address.
If a client submits a request for an access token without
specifying an "aud" parameter, and the AS does not have a default
"aud" value for this client, then the AS MUST respond with an
error message with the CoAP response code 4.00 (Bad Request).
cnf cnf
OPTIONAL. This field contains information about a public key the OPTIONAL. This field contains information about the key the
client would like to bind to the access token. If the client client would like to bind to the access token for proof-of-
requests an asymmetric proof-of-possession algorithm, but does not possession. It is NOT RECOMMENDED that a client submits a
provide a public key, the AS MUST respond with an error message. symmetric key value to the AS using this parameter. See
See Section 6.4 for more details on the formatting of the 'cnf' Section 6.4.5 for more details on the formatting of the 'cnf'
parameter. parameter.
These new parameters are optional in the case where the AS has prior
knowledge of the capabilities of the client, otherwise these
parameters are required. This prior knowledge may, for example, be
set by the use of a dynamic client registration protocol exchange
[RFC7591].
The following examples illustrate different types of requests for The following examples illustrate different types of requests for
proof-of-possession tokens. proof-of-possession tokens.
Figure 2 shows a request for a token with a symmetric proof-of- Figure 2 shows a request for a token with a symmetric proof-of-
possession key. possession key. Note that in this example we assume a DTLS-based
communication security profile, therefore the Content-Type is
"application/cbor".
Header: POST (Code=0.02) Header: POST (Code=0.02)
Uri-Host: "server.example.com" Uri-Host: "server.example.com"
Uri-Path: "token" Uri-Path: "token"
Content-Type: "application/cbor" Content-Type: "application/cbor"
Payload: Payload:
{ {
"grant_type" : "client_credentials", "grant_type" : "client_credentials",
"aud" : "tempSensor4711", "aud" : "tempSensor4711",
"client_id" : "myclient", }
"client_secret" : b64'FWRUVGZUZmZFRkWSRlVGhA',
"token_type" : "pop",
"alg" : "HS256",
"profile" : "coap_dtls"
}
Figure 2: Example request for an access token bound to a symmetric Figure 2: Example request for an access token bound to a symmetric
key. key.
Figure 3 shows a request for a token with an asymmetric proof-of- Figure 3 shows a request for a token with an asymmetric proof-of-
possession key. possession key. Note that in this example we assume an object
security-based profile, therefore the Content-Type is "application/
cose+cbor".
Header: POST (Code=0.02) Header: POST (Code=0.02)
Uri-Host: "server.example.com" Uri-Host: "server.example.com"
Uri-Path: "token" Uri-Path: "token"
Content-Type: "application/cbor" Content-Type: "application/cose+cbor"
Payload: Payload:
{ {
"grant_type" : "token", "grant_type" : "client_credentials",
"aud" : "lockOfDoor0815",
"client_id" : "myclient",
"token_type" : "pop",
"alg" : "ES256",
"profile" : "coap_oscoap"
"cnf" : { "cnf" : {
"COSE_Key" : { "COSE_Key" : {
"kty" : "EC", "kty" : "EC",
"kid" : h'11', "kid" : h'11',
"crv" : "P-256", "crv" : "P-256",
"x" : b64'usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8', "x" : b64'usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8',
"y" : b64'IBOL+C3BttVivg+lSreASjpkttcsz+1rb7btKLv8EX4' "y" : b64'IBOL+C3BttVivg+lSreASjpkttcsz+1rb7btKLv8EX4'
} }
} }
} }
Figure 3: Example request for an access token bound to an asymmetric Figure 3: Example request for an access token bound to an asymmetric
key. key.
Figure 4 shows a request for a token where a previously communicated Figure 4 shows a request for a token where a previously communicated
proof-of-possession key is only referenced. proof-of-possession key is only referenced. Note that we assume a
DTLS-based communication security profile for this example, therefore
the Content-Type is "application/cbor". Also note that the client
performs a password based authentication in this example by
submitting its client_secret.
Header: POST (Code=0.02) Header: POST (Code=0.02)
Uri-Host: "server.example.com" Uri-Host: "server.example.com"
Uri-Path: "token" Uri-Path: "token"
Content-Type: "application/cbor" Content-Type: "application/cbor"
Payload: Payload:
{ {
"grant_type" : "client_credentials", "grant_type" : "client_credentials",
"client_id" : "myclient",
"client_secret" : "mysecret234",
"aud" : "valve424", "aud" : "valve424",
"scope" : "read", "scope" : "read",
"client_id" : "myclient",
"token_type" : "pop",
"alg" : "ES256",
"profile" : "coap_oscoap"
"cnf" : { "cnf" : {
"kid" : b64'6kg0dXJM13U' "kid" : b64'6kg0dXJM13U'
} }
} }
Figure 4: Example request for an access token bound to a key Figure 4: Example request for an access token bound to a key
reference. reference.
6.2. AS-to-Client Response 6.2. AS-to-Client Response
If the access token request has been successfully verified by the AS If the access token request has been successfully verified by the AS
and the client is authorized to obtain a PoP token for the indicated and the client is authorized to obtain an access token corresponding
audience and scopes (if any), the AS issues an access token. If to its access token request, the AS sends a response with the CoAP
client authentication failed or is invalid, the authorization server response code 2.01 (Created). If client request was invalid, or not
returns an error response as described in Section 6.3. authorized, the AS returns an error response as described in
Section 6.3.
The following parameters may also be part of a successful response in Note that the AS decides which token type and profile to use when
addition to those defined in section 5.1 of [RFC6749]: issuing a successful response. It is assumed that the AS has prior
knowledge of the capabilities of the client, and the RS. This prior
knowledge may, for example, be set by the use of a dynamic client
registration protocol exchange [RFC7591].
The content of the successful reply MUST be encoded as CBOR map,
containing paramters as speficied in section 5.1 of [RFC6749]. In
addition to these parameters, the following parameters are also part
of a successful response:
profile profile
REQUIRED. This indicates the profile that the client MUST use REQUIRED. This indicates the profile that the client MUST use
towards the RS. See Section 6.4 for the formatting of this towards the RS. See Section 6.4.4 for the formatting of this
parameter. parameter.
cnf cnf
REQUIRED. This field contains information about the proof-of REQUIRED if the token type is 'pop'. OPTIONAL otherwise. If a
possession key for this access token. See Section 6.4 for the symmetric proof-of-possession algorithms was selected, this field
contains the proof-of-possession key. If an asymmetric algorithm
was selected, this field contains information about the public key
used by the RS to authenticate. See Section 6.4.5 for the
formatting of this parameter. formatting of this parameter.
token_type
OPTIONAL. By default implementations of this framework SHOULD
assume that the token_type is 'pop'. If a specific use case
requires another token_type (e.g. 'Bearer') to be used then this
parameter is REQUIRED.
Note that the access token can also contains a 'cnf' claim, however, Note that if CBOR Web Tokens [I-D.ietf-ace-cbor-web-token] are used,
these two values are consumed by different parties. The access token the access token can also contain a 'cnf' claim. This claim is
is created by the AS and processed by the RS (and opaque to the however consumed by a different party. The access token is created
client) whereas the Client Information is created by the AS and by the AS and processed by the RS (and opaque to the client) whereas
processed by the client; it is never forwarded to the resource the RS Information is created by the AS and processed by the client;
server. it is never forwarded to the resource server.
The following examples illustrate different types of responses for The following examples illustrate different types of responses for
proof-of-possession tokens. proof-of-possession tokens.
Figure 5 shows a response containing a token and a 'cnf' parameter Figure 5 shows a response containing a token and a 'cnf' parameter
with a symmetric proof-of-possession key. with a symmetric proof-of-possession key. Note that we assume a
DTLS-based communication security profile for this example, therefore
the Content-Type is "application/cbor".
Header: Created (Code=2.01) Header: Created (Code=2.01)
Content-Type: "application/cbor" Content-Type: "application/cbor"
Payload: Payload:
{ {
"access_token" : b64'SlAV32hkKG ... "access_token" : b64'SlAV32hkKG ...
(remainder of CWT omitted for brevity; (remainder of CWT omitted for brevity;
CWT contains COSE_Key in the 'cnf' claim)', CWT contains COSE_Key in the 'cnf' claim)',
"token_type" : "pop",
"alg" : "HS256",
"expires_in" : "3600", "expires_in" : "3600",
"profile" : "coap_dtls"
"cnf" : { "cnf" : {
"COSE_Key" : { "COSE_Key" : {
"kty" : "Symmetric", "kty" : "Symmetric",
"kid" : b64'39Gqlw', "kid" : b64'39Gqlw',
"k" : b64'hJtXhkV8FJG+Onbc6mxCcQh' "k" : b64'hJtXhkV8FJG+Onbc6mxCcQh'
} }
} }
} }
Figure 5: Example AS response with an access token bound to a Figure 5: Example AS response with an access token bound to a
symmetric key. symmetric key.
6.3. Error Response 6.3. Error Response
The error responses for CoAP-based interactions with the AS are The error responses for CoAP-based interactions with the AS are
equivalent to the ones for HTTP-based interactions as defined in equivalent to the ones for HTTP-based interactions as defined in
section 5.2 of [RFC6749], with the following differences: The section 5.2 of [RFC6749], with the following differences: The
Content-Type MUST be set to "application/cbor", the payload MUST be Content-Type is specified by the communication security profile used
encoded in a CBOR map and the CoAP response code 4.00 Bad Request between client and AS. The raw payload before being processed by the
MUST be used unless specified otherwise. communication security protocol MUST be encoded as a CBOR map and the
CoAP response code 4.00 (Bad Request) MUST be used unless specified
otherwise.
6.4. New Request and Response Parameters 6.4. New Request and Response Parameters
This section defines parameters that can be used in access token This section provides more detail about the new parameters that can
requests and responses, as well as abbreviations for more compact be used in access token requests and responses, as well as
encoding of existing parameters and common values. abbreviations for more compact encoding of existing parameters and
common parameter values.
6.4.1. Grant Type 6.4.1. Audience
This parameter specifies for which audience the client is requesting
a token. It should be encoded as CBOR text string (major type 3).
The formatting and semantics of these strings are application
specific.
6.4.2. Grant Type
The abbreviations in Figure 6 MAY be used in CBOR encodings instead The abbreviations in Figure 6 MAY be used in CBOR encodings instead
of the string values defined in [RFC6749]. of the string values defined in [RFC6749].
/--------------------+----------+--------------\ /--------------------+----------+--------------\
| grant_type | CBOR Key | Major Type | | grant_type | CBOR Key | Major Type |
|--------------------+----------+--------------| |--------------------+----------+--------------|
| password | 0 | 0 (uint) | | password | 0 | 0 (uint) |
| authorization_code | 1 | 0 | | authorization_code | 1 | 0 |
| client_credentials | 2 | 0 | | client_credentials | 2 | 0 |
| refresh_token | 3 | 0 | | refresh_token | 3 | 0 |
\--------------------+----------+--------------/ \--------------------+----------+--------------/
Figure 6: CBOR abbreviations for common grant types Figure 6: CBOR abbreviations for common grant types
6.4.2. Token Type and Algorithms 6.4.3. Token Type
To allow clients to indicate support for specific token types and
respective algorithms they need to interact with the AS. They can
either provide this information out-of-band or via the 'token_type'
and 'alg' parameter in the client request.
The value in the 'alg' parameter together with value from the The 'token_type' parameter allows the AS to indicate to the client
'token_type' parameter allow the client to indicate the supported which type of access token it is receiving (e.g. a bearer token).
algorithms for a given token type. The token type refers to the The 'pop' token type MUST be assumed by default if the AS does not
specification used by the client to interact with the resource server provide a different value.
to demonstrate possession of the key. The 'alg' parameter provides
further information about the algorithm, such as whether a symmetric
or an asymmetric crypto-system is used. Hence, a client supporting a
specific token type also knows how to populate the values to the
'alg' parameter.
This document registers the new value "pop" for the OAuth Access This document registers the new value "pop" for the OAuth Access
Token Types registry, specifying a Proof-of-Possession token. How Token Types registry, specifying a Proof-of-Possession token. How
the proof-of-possession is performed is specified by the 'alg' the proof-of-possession is performed is specified by the profiles.
parameter. Profiles of this framework are responsible for defining
values for the 'alg' parameter together with the corresponding proof-
of-possession mechanisms.
The values in the 'alg' parameter are case-sensitive. If the client
supports more than one algorithm then each individual value MUST be
separated by a space.
6.4.3. Profile
The "profile" parameter identifies the communication protocol and the The values in the 'token_type' parameter are CBOR text strings (major
communication security protocol between the client and the RS. type 3).
An initial set of profile identifiers and their CBOR encodings are 6.4.4. Profile
specified in Figure 7. Profiles using other combinations of
protocols are expected to define their own profile identifiers.
/--------------------+----------+--------------\ Profiles of this framework are expected to define the communication
| Profile identifier | CBOR Key | Major Type | protocol and the communication security protocol between the client
|--------------------+----------+--------------| and the RS. Furthermore profiles are expected to define proof-of-
| http_tls | 0 | 0 (uint) | possession methods, if they support proof-of-possession tokens.
| coap_dtls | 1 | 0 |
| coap_oscoap | 2 | 0 |
\--------------------+----------+--------------/
Figure 7: Profile identifiers and their CBOR mappings A profile should specify an identifier that is used to uniquely
identify itself in the 'profile' parameter.
Profiles MAY define additional parameters for both the token request Profiles MAY define additional parameters for both the token request
and the client information in the access token response in order to and the RS Information in the access token response in order to
support negotioation or signalling of profile specific parameters. support negotioation or signalling of profile specific parameters.
6.4.4. Confirmation 6.4.5. Confirmation
The "cnf" parameter identifies or provides the key used for proof-of- The "cnf" parameter identifies or provides the key used for proof-of-
possession. This framework extends the definition of 'cnf' from possession or for authenticating the RS depending on the proof-of-
[RFC7800] by defining CBOR/COSE encodings and the use of 'cnf' for possession algorithm and the context cnf is used in. This framework
transporting keys in the client information. extends the definition of 'cnf' from [RFC7800] by adding CBOR/COSE
encodings and the use of 'cnf' for transporting keys in the RS
Information.
A CBOR encoded payload MAY contain the 'cnf' parameter with the A CBOR encoded payload MAY contain the 'cnf' parameter with the
following contents: following contents:
COSE_Key In this case the 'cnf' parameter contains the proof-of- COSE_Key In this case the 'cnf' parameter contains the proof-of-
possession key to be used by the client. An example is shown in possession key to be used by the client. An example is shown in
Figure 8. Figure 7.
"cnf" : { "cnf" : {
"COSE_Key" : { "COSE_Key" : {
"kty" : "EC", "kty" : "EC",
"kid" : h'11', "kid" : h'11',
"crv" : "P-256", "crv" : "P-256",
"x" : b64'usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8', "x" : b64'usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8',
"y" : b64'IBOL+C3BttVivg+lSreASjpkttcsz+1rb7btKLv8EX4' "y" : b64'IBOL+C3BttVivg+lSreASjpkttcsz+1rb7btKLv8EX4'
} }
} }
Figure 8: Confirmation parameter containing a public key Figure 7: Confirmation parameter containing a public key
Note that the COSE_Key structure may contain an "alg" or "key_ops"
parameter. If such parameters are present, a client MUST NOT use
a key that is not compatible with the profile or proof-of-
possession algorithm according to those parameters.
COSE_Encrypted In this case the 'cnf' parameter contains an COSE_Encrypted In this case the 'cnf' parameter contains an
encrypted symmetriic key destined for the client. The client is encrypted symmetric key destined for the client. The client is
assumed to be able to decrypt the cihpertext of this parameter. assumed to be able to decrypt the cihpertext of this parameter.
The parameter is encoded as COSE_Encrypted object wrapping a The parameter is encoded as COSE_Encrypted object wrapping a
COSE_Key object. Figure 9 shows an example of this type of COSE_Key object. Figure 8 shows an example of this type of
encoding. encoding.
"cnf" : { "cnf" : {
"COSE_Encrypted" : { "COSE_Encrypted" : {
993( 993(
[ h'a1010a' # protected header : {"alg" : "AES-CCM-16-64-128"} [ h'a1010a' # protected header : {"alg" : "AES-CCM-16-64-128"}
"iv" : b64'ifUvZaHFgJM7UmGnjA', # unprotected header "iv" : b64'ifUvZaHFgJM7UmGnjA', # unprotected header
b64'WXThuZo6TMCaZZqi6ef/8WHTjOdGk8kNzaIhIQ' # ciphertext b64'WXThuZo6TMCaZZqi6ef/8WHTjOdGk8kNzaIhIQ' # ciphertext
] ]
) )
} }
} }
Figure 9: Confirmation paramter containing an encrypted symmetric key Figure 8: Confirmation paramter containing an encrypted symmetric key
The ciphertext here could e.g. contain a symmetric key as in The ciphertext here could e.g. contain a symmetric key as in
Figure 10. Figure 9.
{ {
"kty" : "Symmetric", "kty" : "Symmetric",
"kid" : b64'39Gqlw', "kid" : b64'39Gqlw',
"k" : b64'hJtXhkV8FJG+Onbc6mxCcQh' "k" : b64'hJtXhkV8FJG+Onbc6mxCcQh'
} }
Figure 10: Example plaintext of an encrypted cnf parameter Figure 9: Example plaintext of an encrypted cnf parameter
Key Identifier In this case the 'cnf' parameter references a key Key Identifier In this case the 'cnf' parameter references a key
that is assumed to be previously known by the recipient. This that is assumed to be previously known by the recipient. This
allows clients that perform repeated requests for an access token allows clients that perform repeated requests for an access token
for the same audience but e.g. with different scopes to omit key for the same audience but e.g. with different scopes to omit key
transport in the access token, token request and token response. transport in the access token, token request and token response.
Figure 11 shows such an example. Figure 10 shows such an example.
"cnf" : { "cnf" : {
"kid" : b64'39Gqlw' "kid" : b64'39Gqlw'
} }
Figure 11: A Confirmation parameter with just a key identifier Figure 10: A Confirmation parameter with just a key identifier
6.5. Mapping parameters to CBOR 6.5. Mapping parameters to CBOR
All OAuth parameters in access token requests and responses are All OAuth parameters in access token requests and responses are
mapped to CBOR types as follows and are given an integer key value to mapped to CBOR types as follows and are given an integer key value to
save space. save space.
/-------------------+----------+-----------------\ /-------------------+----------+-----------------\
| Parameter name | CBOR Key | Major Type | | Parameter name | CBOR Key | Major Type |
|-------------------+----------+-----------------| |-------------------+----------+-----------------|
| client_id | 1 | 3 (text string) | | aud | 3 | 3 |
| client_secret | 2 | 2 (byte string) | | client_id | 8 | 3 (text string) |
| response_type | 3 | 3 | | client_secret | 9 | 2 (byte string) |
| redirect_uri | 4 | 3 | | response_type | 10 | 3 |
| scope | 5 | 3 | | redirect_uri | 11 | 3 |
| state | 6 | 3 | | scope | 12 | 3 |
| code | 7 | 2 | | state | 13 | 3 |
| error_description | 8 | 3 | | code | 14 | 2 |
| error_uri | 9 | 3 | | error_description | 15 | 3 |
| grant_type | 10 | 0 (unit) | | error_uri | 16 | 3 |
| access_token | 11 | 3 | | grant_type | 17 | 0 (unit) |
| token_type | 12 | 0 | | access_token | 18 | 3 |
| expires_in | 13 | 0 | | token_type | 19 | 0 |
| username | 14 | 3 | | expires_in | 20 | 0 |
| password | 15 | 3 | | username | 21 | 3 |
| refresh_token | 16 | 3 | | password | 22 | 3 |
| alg | 17 | 3 | | refresh_token | 23 | 3 |
| cnf | 18 | 5 (map) | | cnf | 24 | 5 (map) |
| aud | 19 | 3 | | profile | 25 | 3 |
| profile | 20 | 0 | \-------------------+----------+-----------------/
\---------------+--------------+-----------------/
Figure 12: CBOR mappings used in token requests Figure 11: CBOR mappings used in token requests
7. The 'Introspect' Resource 7. The 'Introspect' Endpoint
Token introspection [RFC7662] is used by the RS and potentially the Token introspection [RFC7662] is used by the RS and potentially the
client to query the AS for metadata about a given token e.g. validity client to query the AS for metadata about a given token e.g. validity
or scope. Analogous to the protocol defined in RFC 7662 [RFC7662] or scope. Analogous to the protocol defined in RFC 7662 [RFC7662]
for HTTP and JSON, this section defines adaptations to more for HTTP and JSON, this section defines adaptations to more
constrained environments using CoAP and CBOR. constrained environments using CoAP and CBOR.
Communication between the RS and the introspection resource at the AS Communication between the RS and the introspection endpoint at the AS
MUST be integrity protected and encrypted. Furthermore AS and RS MUST be integrity protected and encrypted. Furthermore AS and RS
MUST perform mutual authentication. Finally the AS SHOULD to verify MUST perform mutual authentication. Finally the AS SHOULD verify
that the RS has the right to access introspection information about that the RS has the right to access introspection information about
the provided token. Profiles of this framework are expected to the provided token. Profiles of this framework are expected to
specify how authentication and communication security is implemented. specify how authentication and communication security is implemented.
The figures of this section uses CBOR diagnostic notation without the The figures of this section uses CBOR diagnostic notation without the
integer abbreviations for the parameters or their values for better integer abbreviations for the parameters or their values for better
readability. readability.
7.1. RS-to-AS Request 7.1. RS-to-AS Request
The RS sends a CoAP POST request to the introspection resource at the The RS sends a CoAP POST request to the introspection endpoint at the
AS, with payload sent as "application/cbor" data. The payload is a AS, the profile is expected to specify the Content-Type and wrapping
CBOR map with a 'token' parameter containing the access token along of the payload. The payload MUST be encoded as a CBOR map with a
with optional parameters representing additional context that is 'token' parameter containing the access token along with optional
known by the RS to aid the AS in its response. parameters representing additional context that is known by the RS to
aid the AS in its response.
The same parameters are required and optional as in section 2.1 of The same parameters are required and optional as in section 2.1 of
RFC 7662 [RFC7662]. RFC 7662 [RFC7662].
For example, Figure 13 shows a RS calling the token introspection For example, Figure 12 shows a RS calling the token introspection
resource at the AS to query about an OAuth 2.0 proof-of-possession endpoint at the AS to query about an OAuth 2.0 proof-of-possession
token. token. Note that we assume a object security-based communication
security profile for this example, therefore the Content-Type is
"application/cose+cbor".
Header: POST (Code=0.02) Header: POST (Code=0.02)
Uri-Host: "server.example.com" Uri-Host: "server.example.com"
Uri-Path: "introspect" Uri-Path: "introspect"
Content-Type: "application/cbor" Content-Type: "application/cose+cbor"
Payload: Payload:
{ {
"token" : b64'7gj0dXJQ43U', "token" : b64'7gj0dXJQ43U',
"token_type_hint" : "pop" "token_type_hint" : "pop"
} }
Figure 13: Example introspection request. Figure 12: Example introspection request.
7.2. AS-to-RS Response 7.2. AS-to-RS Response
The AS responds with a CBOR object in "application/cbor" format with If the introspection request is authorized and successfully
the same required and optional parameters as in section 2.2. of RFC processed, the AS sends a response with the CoAP response code 2.01
7662 [RFC7662] with the following additions: (Created). If the introspection request was invalid, not authorized
or couldn't be processed the AS returns an error response as
described in Section 7.3.
alg In a successful response, the AS encodes the response parameters in a
OPTIONAL. See Section 6.4 for more details. CBOR map including with the same required and optional parameters as
in section 2.2. of RFC 7662 [RFC7662] with the following additions:
cnf cnf
OPTIONAL. This field contains information about the proof-of- OPTIONAL. This field contains information about the proof-of-
possession key that binds the client to the access token. See possession key that binds the client to the access token. See
Section 6.4 for more details on the formatting of the 'cnf' Section 6.4.5 for more details on the formatting of the 'cnf'
parameter. parameter.
profile profile
OPTIONAL. This indicates the profile that the RS MUST use with OPTIONAL. This indicates the profile that the RS MUST use with
the client. See Section 6.4 for more details on the formatting of the client. See Section 6.4.4 for more details on the formatting
this parameter. of this parameter.
client_token client_token
OPTIONAL. This parameter contains information that the RS MUST OPTIONAL. This parameter contains information that the RS MUST
pass on to the client. See Section 7.4 for more details. pass on to the client. See Section 7.4 for more details.
For example, Figure 14 shows an AS response to the introspection For example, Figure 13 shows an AS response to the introspection
request in Figure 13. request in Figure 12. Note that we assume a DTLS-based communication
security profile for this example, therefore the Content-Type is
"application/cbor".
Header: Created Code=2.01) Header: Created Code=2.01)
Content-Type: "application/cbor" Content-Type: "application/cbor"
Payload: Payload:
{ {
"active" : true, "active" : true,
"scope" : "read", "scope" : "read",
"token_type" : "pop",
"alg" : "HS256",
"profile" : "coap_dtls", "profile" : "coap_dtls",
"client_token" : b64'2QPhg0OhAQo ... "client_token" : b64'2QPhg0OhAQo ...
(remainder of client token omitted for brevity)', (remainder of client token omitted for brevity)',
"cnf" : { "cnf" : {
"COSE_Key" : { "COSE_Key" : {
"kty" : "Symmetric", "kty" : "Symmetric",
"kid" : b64'39Gqlw', "kid" : b64'39Gqlw',
"k" : b64'hJtXhkV8FJG+Onbc6mxCcQh' "k" : b64'hJtXhkV8FJG+Onbc6mxCcQh'
} }
} }
} }
Figure 14: Example introspection response. Figure 13: Example introspection response.
7.3. Error Response 7.3. Error Response
The error responses for CoAP-based interactions with the AS are The error responses for CoAP-based interactions with the AS are
equivalent to the ones for HTTP-based interactions as defined in equivalent to the ones for HTTP-based interactions as defined in
section 2.3 of [RFC7662], with the following differences: section 2.3 of [RFC7662], with the following differences:
o If content is sent, the Content-Type MUST be set to "application/ o If content is sent, the Content-Type MUST be set according to the
cbor", and the payload MUST be encoded in a CBOR map. specification of the communication security profile, and the
content payload MUST be encoded as a CBOR map.
o If the credentials used by the RS are invalid the AS MUST respond o If the credentials used by the RS are invalid the AS MUST respond
with the CoAP response code code 4.01 (Unauthorized) and use the with the CoAP response code 4.01 (Unauthorized) and use the
required and optional parameters from section 5.2 in RFC 6749 required and optional parameters from section 5.2 in RFC 6749
[RFC6749]. [RFC6749].
o If the RS does not have the right to perform this introspection o If the RS does not have the right to perform this introspection
request, the AS MUST respond with the CoAP response code 4.03 request, the AS MUST respond with the CoAP response code 4.03
(Forbidden). In this case no payload is returned. (Forbidden). In this case no payload is returned.
Note that a properly formed and authorized query for an inactive or Note that a properly formed and authorized query for an inactive or
otherwise invalid token does not warrant an error response by this otherwise invalid token does not warrant an error response by this
specification. In these cases, the authorization server MUST instead specification. In these cases, the authorization server MUST instead
respond with an introspection response with the "active" field set to respond with an introspection response with the "active" field set to
"false". "false".
skipping to change at page 25, line 23 skipping to change at page 25, line 27
EDITORIAL NOTE: We have tentatively introduced this concept and would EDITORIAL NOTE: We have tentatively introduced this concept and would
specifically like feedback if this is viewed as a useful addition to specifically like feedback if this is viewed as a useful addition to
the framework. the framework.
In cases where the client has limited connectivity and is requesting In cases where the client has limited connectivity and is requesting
access to a previously unknown resource servers, using a long term access to a previously unknown resource servers, using a long term
token, there are situations where it would be beneficial to relay the token, there are situations where it would be beneficial to relay the
proof-of-possession key and other relevant information from the AS to proof-of-possession key and other relevant information from the AS to
the client through the RS. The client_token parameter is designed to the client through the RS. The client_token parameter is designed to
carry such information, and is intended to be used as described in carry such information, and is intended to be used as described in
Figure 15. Figure 14.
Resource Authorization Resource Authorization
Client Server Server Client Server Server
| | | | | |
| | | | | |
A: +--------------->| | C: +--------------->| |
| POST | | | POST | |
| Access Token | | | Access Token | |
| B: +--------------->| | D: +--------------->|
| | Introspection | | | Introspection |
| | Request | | | Request |
| | | | | |
| C: +<---------------+ | E: +<---------------+
| | Introspection | | | Introspection |
| | Response | | | Response |
| | + Client Token | | | + Client Token |
D: |<---------------+ | |<---------------+ |
| 2.01 Created | | | 2.01 Created | |
| + Client Token | | + Client Token |
Figure 15: Use of the client_token parameter. Figure 14: Use of the client_token parameter.
The client token is a COSE_Encrytped object, containing as payload a The client token is a COSE_Encrytped object, containing as payload a
CBOR map with the following claims: CBOR map with the following claims:
cnf cnf
REQUIRED. Contains information about the proof-of-possession key REQUIRED if the token type is 'pop', OPTIONAL otherwise. Contains
the client is to use with its access token. See Section 6.4.4. information about the proof-of-possession key the client is to use
with its access token. See Section 6.4.5.
token_type token_type
OPTIONAL. See Section 6.4.2. OPTIONAL. See Section 6.4.3.
alg
OPTIONAL. See Section 6.4.2.
profile profile
REQUIRED. See Section 6.4.3. REQUIRED. See Section 6.4.4.
rs_cnf rs_cnf
OPTIONAL. Contains information about the key that the RS uses to OPTIONAL. Contains information about the key that the RS uses to
authenticate towards the client. If the key is symmetric then authenticate towards the client. If the key is symmetric then
this claim MUST NOT be part of the Client Token, since this is the this claim MUST NOT be part of the Client Token, since this is the
same key as the one specified through the 'cnf' claim. This claim same key as the one specified through the 'cnf' claim. This claim
uses the same encoding as the 'cnf' parameter. See Section 6.4.3. uses the same encoding as the 'cnf' parameter. See Section 6.4.4.
The AS encrypts this token using a key shared between the AS and the The AS encrypts this token using a key shared between the AS and the
client, so that only the client can decrypt it and access its client, so that only the client can decrypt it and access its
payload. How this key is established is out of scope of this payload. How this key is established is out of scope of this
framework. framework.
7.5. Mapping Introspection parameters to CBOR 7.5. Mapping Introspection parameters to CBOR
The introspection request and response parameters are mapped to CBOR The introspection request and response parameters are mapped to CBOR
types as follows and are given an integer key value to save space. types as follows and are given an integer key value to save space.
/----------------+----------+-----------------\ /-----------------+----------+-----------------\
| Parameter name | CBOR Key | Major Type | | Parameter name | CBOR Key | Major Type |
|----------------+----------+-----------------| |-----------------+----------+-----------------|
| active | 1 | 0 (uint) | | iss | 1 | 3 (text string) |
| username | 2 | 3 (text string) | | sub | 2 | 3 |
| client_id | 3 | 3 | | aud | 3 | 3 |
| scope | 4 | 3 | | exp | 4 | 6 tag value 1 |
| token_type | 5 | 3 | | nbf | 5 | 6 tag value 1 |
| exp | 6 | 6 tag value 1 | | iat | 6 | 6 tag value 1 |
| iat | 7 | 6 tag value 1 | | cti | 7 | 2 (byte string) |
| nbf | 8 | 6 tag value 1 | | client_id | 8 | 3 |
| sub | 9 | 3 | | scope | 12 | 3 |
| aud | 10 | 3 | | token_type | 19 | 3 |
| iss | 11 | 3 | | username | 21 | 3 |
| jti | 12 | 3 | | cnf | 24 | 5 (map) |
| alg | 13 | 3 | | profile | 25 | 0 (uint) |
| cnf | 14 | 5 (map) | | token | 26 | 3 |
| aud | 15 | 3 | | token_type_hint | 27 | 3 |
| client_token | 16 | 3 | | active | 28 | 0 |
| rs_cnf | 17 | 5 | | client_token | 29 | 3 |
\----------------+----------+-----------------/ | rs_cnf | 30 | 5 |
\-----------------+----------+-----------------/
Figure 16: CBOR Mappings to Token Introspection Parameters. Figure 15: CBOR Mappings to Token Introspection Parameters.
8. The Access Token 8. The Access Token
This framework RECOMMENDS the use of CBOR web token (CWT) as This framework RECOMMENDS the use of CBOR web token (CWT) as
specified in [I-D.ietf-ace-cbor-web-token]. specified in [I-D.ietf-ace-cbor-web-token].
In order to facilitate offline processing of access tokens, this In order to facilitate offline processing of access tokens, this
draft specfifies the "scope" claim for access tokens that explicitly draft specifies the "cnf" and "scope" claims for CBOR web tokens.
encodes the scope of a given access token. This claim follows the
same encoding rules as defined in section 3.3 of [RFC6749]. The
meaning of a specific scope value is application specific and
expected to be known to the RS running that application.
8.1. The 'Authorization Information' Resource The "scope" claim explicitly encodes the scope of a given access
token. This claim follows the same encoding rules as defined in
section 3.3 of [RFC6749]. The meaning of a specific scope value is
application specific and expected to be known to the RS running that
application.
The "cnf" claim follows the same rules as specified for JSON web
token in RFC7800 [RFC7800], except that it is encoded in CBOR in the
same way as specified for the "cnf" parameter in section
Section 6.4.5.
8.1. The 'Authorization Information' Endpoint
The access token, containing authorization information and The access token, containing authorization information and
information of the key used by the client, is transported to the RS information of the key used by the client, needs to be transported to
so that the RS can authenticate and authorize the client request. the RS so that the RS can authenticate and authorize the client
request.
This section defines a method for transporting the access token to This section defines a method for transporting the access token to
the RS using CoAP that MAY be used. An ACE profile MAY define other the RS using CoAP. Profiles of this framework MAY define other
methods for token transport. methods for token transport. Implementations conforming to this
framework MUST implement this method of token transportation.
This method REQUIRES the RS to implement an /authz-info resource. A The method consists of a /authz-info endpoint, implemented by the RS.
client using this method MUST make a POST request to /authz-info on A client using this method MUST make a POST request to /authz-info at
the RS with the access token in the payload. The RS receiving the the RS with the access token in the payload. The RS receiving the
token MUST verify the validity of the token. If the token is valid, token MUST verify the validity of the token. If the token is valid,
the RS MUST respond to the POST request with 2.04 (Changed). the RS MUST respond to the POST request with 2.04 (Changed).
If the token is not valid, the RS MUST respond with error code 4.01 If the token is not valid, the RS MUST respond with the CoAP response
(Unauthorized). If the token is valid but the audience of the token code 4.01 (Unauthorized). If the token is valid but the audience of
does not match the RS, the RS MUST respond with error code 4.03 the token does not match the RS, the RS MUST respond with the CoAP
(Forbidden). response code 4.03 (Forbidden).
The RS MAY make an introspection request to validate the token before The RS MAY make an introspection request to validate the token before
responding to the POST /authz-info request. If the introspection responding to the POST /authz-info request. If the introspection
response contains a client token (Section 7.4) then this token SHALL response contains a client token (Section 7.4) then this token SHALL
be included in the payload of the 2.04 (Changed) response. be included in the payload of the 2.04 (Changed) response.
Profiles are expected to specify how the /authz-info endpoint is
protected. Note that since the token contains information that allow
the client and the RS to establish a security context in the first
place, mutual authentication may not be possible at this point.
8.2. Token Expiration 8.2. Token Expiration
Depending on the capabilities of the RS, there are various ways in Depending on the capabilities of the RS, there are various ways in
which it can verify the validity of a received access token. We list which it can verify the validity of a received access token. We list
the possibilities here including what functionality they require of the possibilities here including what functionality they require of
the RS. the RS.
o The token is a CWT/JWT and includes a 'exp' claim and possibly the o The token is a CWT/JWT and includes a 'exp' claim and possibly the
'nbf' claim. The RS verifies these by comparing them to values 'nbf' claim. The RS verifies these by comparing them to values
from its internal clock as defined in [RFC7519]. In this case the from its internal clock as defined in [RFC7519]. In this case the
RS must have a real time chip (RTC) or some other way of reliably RS's internal clock must reflect the current date and time, or at
measuring time. least be synchronized with the AS's clock. How this clock
synchronization would be performed is out of scope for this memo.
o The RS verifies the validity of the token by performing an o The RS verifies the validity of the token by performing an
introspection request as specified in Section 7. This requires introspection request as specified in Section 7. This requires
the RS to have a reliable network connection to the AS and to be the RS to have a reliable network connection to the AS and to be
able to handle two secure sessions in parallel (C to RS and AS to able to handle two secure sessions in parallel (C to RS and AS to
RS). RS).
o The RS and the AS both store a sequence number linked to their o The RS and the AS both store a sequence number linked to their
common security association. The AS increments this number for common security association. The AS increments this number for
each access token it issues and includes it in the access token, each access token it issues and includes it in the access token,
which is a CWT/JWT. The RS keeps track of the most recently which is a CWT/JWT. The RS keeps track of the most recently
received sequence number, and only accepts tokens as valid, that received sequence number, and only accepts tokens as valid, that
skipping to change at page 29, line 6 skipping to change at page 29, line 27
means of reliably measuring time, this is the best that can be means of reliably measuring time, this is the best that can be
achieved. achieved.
9. Security Considerations 9. Security Considerations
The entire document is about security. Security considerations The entire document is about security. Security considerations
applicable to authentication and authorization in RESTful applicable to authentication and authorization in RESTful
environments provided in OAuth 2.0 [RFC6749] apply to this work, as environments provided in OAuth 2.0 [RFC6749] apply to this work, as
well as the security considerations from [I-D.ietf-ace-actors]. well as the security considerations from [I-D.ietf-ace-actors].
Furthermore [RFC6819] provides additional security considerations for Furthermore [RFC6819] provides additional security considerations for
OAuth which apply to IoT deployments as well. Finally OAuth which apply to IoT deployments as well.
[I-D.ietf-oauth-pop-architecture] discusses security and privacy
threats as well as mitigation measures for Proof-of-Possession A large range of threats can be mitigated by protecting the contents
tokens. of the access token by using a digital signature or a keyed message
digest. Consequently, the token integrity protection MUST be applied
to prevent the token from being modified, particularly since it
contains a reference to the symmetric key or the asymmetric key. If
the access token contains the symmetric key, this symmetric key MUST
be encrypted by the authorization server with a long-term key shared
with the resource server.
It is important for the authorization server to include the identity
of the intended recipient (the audience), typically a single resource
server (or a list of resource servers), in the token. Using a single
shared secret with multiple authorization server to simplify key
management is NOT RECOMMENDED since the benefit from using the proof-
of-possession concept is significantly reduced.
Token replay is also not possible since an eavesdropper will also
have to obtain the corresponding private key or shared secret that is
bound to the access token. Nevertheless, it is good practice to
limit the lifetime of the access token and therefore the lifetime of
associated key.
The authorization server MUST offer confidentiality protection for
any interactions with the client. This step is extremely important
since the client will obtain the session key from the authorization
server for use with a specific access token. Not using
confidentiality protection exposes this secret (and the access token)
to an eavesdropper thereby making the proof-of-possession security
model completely insecure. This framework relies on profiles to
define how confidentiality protection is provided, and additional
protection can be applied by encrypting the CWT as specified in
section 5.1 of [I-D.ietf-ace-cbor-web-token] to provide an additional
layer of protection for cases where keying material is conveyed, for
example, to a hardware security module.
Developers MUST ensure that the ephemeral credentials (i.e., the
private key or the session key) is not leaked to third parties. An
adversary in possession of the ephemeral credentials bound to the
access token will be able to impersonate the client. Be aware that
this is a real risk with many constrained environments, since
adversaries can often easily get physical access to the devices.
Clients can at any time request a new proof-of-possession capable
access token. Using a refresh token to regularly request new access
tokens that are bound to fresh and unique keys is important if the
client has this capability. Keeping the lifetime of the access token
short allows the authorization server to use shorter key sizes, which
translate to a performance benefit for the client and for the
resource server. Shorter keys also lead to shorter messages
(particularly with asymmetric keying material).
When authorization servers bind symmetric keys to access tokens then
they SHOULD scope these access tokens to a specific permissions.
10. IANA Considerations 10. IANA Considerations
This specification registers new parameters for OAuth and establishes This specification registers new parameters for OAuth and establishes
registries for mappings to CBOR. registries for mappings to CBOR.
10.1. OAuth Introspection Response Parameter Registration 10.1. OAuth Introspection Response Parameter Registration
This specification registers the following parameters in the OAuth This specification registers the following parameters in the OAuth
introspection response parameters introspection response parameters
o Name: "alg"
o Description: Algorithm to use with PoP key, as defined in PoP
token specification,
o Change Controller: IESG
o Specification Document(s): this document
o Name: "cnf" o Name: "cnf"
o Description: Key to use to prove the right to use an access token, o Description: Key to use to prove the right to use an access token,
as defined in [RFC7800]. as defined in [RFC7800].
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Name: "aud" o Name: "aud"
o Description: reference to intended receiving RS, as defined in PoP o Description: reference to intended receiving RS, as defined in PoP
token specification. token specification.
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Name: "profile" o Name: "profile"
o Description: The communication and communication security profile o Description: The communication and communication security profile
used between client and RS, as defined in ACE profiles. used between client and RS, as defined in ACE profiles.
o Change Controller: IESG o Change Controller: IESG
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used between client and RS, as defined in ACE profiles. used between client and RS, as defined in ACE profiles.
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Name: "client_token" o Name: "client_token"
o Description: Information that the RS MUST pass to the client e.g. o Description: Information that the RS MUST pass to the client e.g.
about the proof-of-possession keys. about the proof-of-possession keys.
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Name: "rs_cnf"
o Description: Describes the public key the RS uses to authenticate.
o Change Controller: IESG
o Specification Document(s): this document
10.2. OAuth Parameter Registration 10.2. OAuth Parameter Registration
This specification registers the following parameters in the OAuth This specification registers the following parameters in the OAuth
Parameters Registry Parameters Registry
o Name: "alg"
o Description: Algorithm to use with PoP key, as defined in PoP
token specification,
o Change Controller: IESG
o Specification Document(s): this document
o Parameter name: "profile" o Parameter name: "profile"
o Parameter usage location: token request, and token response o Parameter usage location: token request, and token response
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Name: "cnf" o Name: "cnf"
o Description: Key to use to prove the right to use an access token, o Description: Key to use to prove the right to use an access token,
as defined in [RFC7800]. as defined in [RFC7800].
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
skipping to change at page 31, line 26 skipping to change at page 32, line 40
o Parameter name: "Bearer" o Parameter name: "Bearer"
o Mapped value: 1 o Mapped value: 1
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "pop" o Parameter name: "pop"
o Mapped value: 2 o Mapped value: 2
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
10.5. JSON Web Token Claims 10.5. CBOR Web Token Claims
This specification registers the following new claim in the JSON Web This specification registers the following new claims in the CBOR Web
Token (JWT) registry. Token (CWT) registry:
o Claim Name: "scope" o Claim Name: "scope"
o Claim Description: The scope of an access token as defined in o Claim Description: The scope of an access token as defined in
[RFC6749]. [RFC6749].
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Claim Name: "cnf"
o Claim Description: The proof-of-possession key of an access token
as defined in [RFC7800].
o Change Controller: IESG
o Specification Document(s): this document
10.6. ACE Profile Registry 10.6. ACE Profile Registry
A new registry will be requested from IANA, entitled "ACE Profile A new registry will be requested from IANA, entitled "ACE Profile
Registry". The registry is to be created as Expert Review Required. Registry". The registry is to be created as Expert Review Required.
10.6.1. Registration Template 10.6.1. Registration Template
Profile name: Profile name:
Name of the profile to be included in the profile attribute. Name of the profile to be included in the profile attribute.
Profile description: Profile description:
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name of the responsible party. Other details (e.g., postal name of the responsible party. Other details (e.g., postal
address, email address, home page URI) may also be included. address, email address, home page URI) may also be included.
Specification Document(s): Specification Document(s):
Reference to the document or documents that specify the Reference to the document or documents that specify the
parameter,preferably including URIs that can be used to retrieve parameter,preferably including URIs that can be used to retrieve
copies of the documents. An indication of the relevant sections copies of the documents. An indication of the relevant sections
may also be included but is not required. may also be included but is not required.
10.7. OAuth Parameter Mappings Registry 10.7. OAuth Parameter Mappings Registry
A new registry will be requested from IANA, entitled "Token Resource A new registry will be requested from IANA, entitled "Token Endpoint
CBOR Mappings Registry". The registry is to be created as Expert CBOR Mappings Registry". The registry is to be created as Expert
Review Required. Review Required.
10.7.1. Registration Template 10.7.1. Registration Template
Parameter name: Parameter name:
OAuth Parameter name, refers to the name in the OAuth parameter OAuth Parameter name, refers to the name in the OAuth parameter
registry e.g. "client_id". registry e.g. "client_id".
CBOR key value: CBOR key value:
Key value for the claim. The key value MUST be an integer in the Key value for the claim. The key value MUST be an integer in the
skipping to change at page 32, line 32 skipping to change at page 34, line 4
Parameter name: Parameter name:
OAuth Parameter name, refers to the name in the OAuth parameter OAuth Parameter name, refers to the name in the OAuth parameter
registry e.g. "client_id". registry e.g. "client_id".
CBOR key value: CBOR key value:
Key value for the claim. The key value MUST be an integer in the Key value for the claim. The key value MUST be an integer in the
range of 1 to 65536. range of 1 to 65536.
Change Controller: Change Controller:
For Standards Track RFCs, list the "IESG". For others, give the For Standards Track RFCs, list the "IESG". For others, give the
name of the responsible party. Other details (e.g., postal name of the responsible party. Other details (e.g., postal
address, email address, home page URI) may also be included. address, email address, home page URI) may also be included.
Specification Document(s): Specification Document(s):
Reference to the document or documents that specify the Reference to the document or documents that specify the
parameter,preferably including URIs that can be used to retrieve parameter,preferably including URIs that can be used to retrieve
copies of the documents. An indication of the relevant sections copies of the documents. An indication of the relevant sections
may also be included but is not required. may also be included but is not required.
10.7.2. Initial Registry Contents 10.7.2. Initial Registry Contents
o Parameter name: "aud"
o CBOR key value: 3
o Change Controller: IESG
o Specification Document(s): this document
o Parameter name: "client_id" o Parameter name: "client_id"
o CBOR key value: 1 o CBOR key value: 8
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "client_secret" o Parameter name: "client_secret"
o CBOR key value: 2 o CBOR key value: 9
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "response_type" o Parameter name: "response_type"
o CBOR key value: 3 o CBOR key value: 10
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "redirect_uri" o Parameter name: "redirect_uri"
o CBOR key value: 4 o CBOR key value: 11
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "scope" o Parameter name: "scope"
o CBOR key value: 5 o CBOR key value: 12
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "state" o Parameter name: "state"
o CBOR key value: 6 o CBOR key value: 13
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "code" o Parameter name: "code"
o CBOR key value: 7 o CBOR key value: 14
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "error_description" o Parameter name: "error_description"
o CBOR key value: 8 o CBOR key value: 15
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "error_uri" o Parameter name: "error_uri"
o CBOR key value: 9 o CBOR key value: 16
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "grant_type" o Parameter name: "grant_type"
o CBOR key value: 10 o CBOR key value: 17
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "access_token" o Parameter name: "access_token"
o CBOR key value: 11 o CBOR key value: 18
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "token_type" o Parameter name: "token_type"
o CBOR key value: 12 o CBOR key value: 19
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "expires_in" o Parameter name: "expires_in"
o CBOR key value: 13 o CBOR key value: 20
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "username" o Parameter name: "username"
o CBOR key value: 14 o CBOR key value: 21
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "password" o Parameter name: "password"
o CBOR key value: 15 o CBOR key value: 22
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "refresh_token" o Parameter name: "refresh_token"
o CBOR key value: 16 o CBOR key value: 23
o Change Controller: IESG
o Specification Document(s): this document
o Parameter name: "alg"
o CBOR key value: 17
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "cnf" o Parameter name: "cnf"
o CBOR key value: 18 o CBOR key value: 24
o Change Controller: IESG
o Specification Document(s): this document
o Parameter name: "aud"
o CBOR key value: 19
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "profile" o Parameter name: "profile"
o CBOR key value: 20 o CBOR key value: 25
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
10.8. Introspection Resource CBOR Mappings Registry 10.8. Introspection Endpoint CBOR Mappings Registry
A new registry will be requested from IANA, entitled "Introspection A new registry will be requested from IANA, entitled "Introspection
Resource CBOR Mappings Registry". The registry is to be created as Endpoint CBOR Mappings Registry". The registry is to be created as
Expert Review Required. Expert Review Required.
10.8.1. Registration Template 10.8.1. Registration Template
Response parameter name: Response parameter name:
Name of the response parameter as defined in the "OAuth Token Name of the response parameter as defined in the "OAuth Token
Introspection Response" registry e.g. "active". Introspection Response" registry e.g. "active".
CBOR key value: CBOR key value:
Key value for the claim. The key value MUST be an integer in the Key value for the claim. The key value MUST be an integer in the
range of 1 to 65536. range of 1 to 65536.
skipping to change at page 35, line 25 skipping to change at page 36, line 37
name of the responsible party. Other details (e.g., postal name of the responsible party. Other details (e.g., postal
address, email address, home page URI) may also be included. address, email address, home page URI) may also be included.
Specification Document(s): Specification Document(s):
Reference to the document or documents that specify the Reference to the document or documents that specify the
parameter,preferably including URIs that can be used to retrieve parameter,preferably including URIs that can be used to retrieve
copies of the documents. An indication of the relevant sections copies of the documents. An indication of the relevant sections
may also be included but is not required. may also be included but is not required.
10.8.2. Initial Registry Contents 10.8.2. Initial Registry Contents
o Response parameter name: "active" o Response parameter name: "iss"
o CBOR key value: 1 o CBOR key value: 1
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "username" o Response parameter name: "sub"
o CBOR key value: 2 o CBOR key value: 2
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "client_id" o Response parameter name: "aud"
o CBOR key value: 3 o CBOR key value: 3
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "exp"
o Response parameter name: "scope"
o CBOR key value: 4 o CBOR key value: 4
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "token_type" o Response parameter name: "nbf"
o CBOR key value: 5 o CBOR key value: 5
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "exp" o Response parameter name: "iat"
o CBOR key value: 6 o CBOR key value: 6
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "iat" o Response parameter name: "cti"
o CBOR key value: 7 o CBOR key value: 7
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "nbf" o Response parameter name: "client_id"
o CBOR key value: 8 o CBOR key value: 8
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "sub" o Response parameter name: "scope"
o CBOR key value: 9 o CBOR key value: 12
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "aud" o Response parameter name: "token_type"
o CBOR key value: 10 o CBOR key value: 19
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "iss" o Response parameter name: "username"
o CBOR key value: 11 o CBOR key value: 21
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Response parameter name: "jti" o Parameter name: "cnf"
o CBOR key value: 12 o CBOR key value: 24
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "alg" o Parameter name: "profile"
o CBOR key value: 13 o CBOR key value: 25
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "cnf" o Response parameter name: "token"
o CBOR key value: 14 o CBOR key value: 26
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
o Parameter name: "aud" o Response parameter name: "token_type_hint"
o CBOR key value: 15 o CBOR key value: 27
o Change Controller: IESG
o Specification Document(s): this document
o Response parameter name: "active"
o CBOR key value: 28
o Change Controller: IESG
o Specification Document(s): this document
o Response parameter name: "client_token"
o CBOR key value: 29
o Change Controller: IESG
o Specification Document(s): this document
o Response parameter name: "rs_cnf"
o CBOR key value: 30
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): this document o Specification Document(s): this document
10.9. CoAP Option Number Registration 10.9. CoAP Option Number Registration
This section registers the "Access-Token" CoAP Option Number in the This section registers the "Access-Token" CoAP Option Number in the
"CoRE Parameters" sub-registry "CoAP Option Numbers" in the manner "CoRE Parameters" sub-registry "CoAP Option Numbers" in the manner
described in [RFC7252]. described in [RFC7252].
Name Name
skipping to change at page 37, line 25 skipping to change at page 39, line 4
TBD TBD
Reference Reference
[This document]. [This document].
Meaning in Request Meaning in Request
Contains an Access Token according to [This document] containing Contains an Access Token according to [This document] containing
access permissions of the client. access permissions of the client.
Meaning in Response Meaning in Response
Not used in response Not used in response
Safe-to-Forward Safe-to-Forward
TBD Yes
Format Format
Based on the observer the format is perceived differently. Opaque Based on the observer the format is perceived differently. Opaque
data to the client and CWT or reference token to the RS. data to the client and CWT or reference token to the RS.
Length Length
Less then 255 bytes Less then 255 bytes
11. Acknowledgments 11. Acknowledgments
We would like to thank Eve Maler for her contributions to the use of We would like to thank Eve Maler for her contributions to the use of
OAuth 2.0 and UMA in IoT scenarios, Robert Taylor for his discussion OAuth 2.0 and UMA in IoT scenarios, Robert Taylor for his discussion
input, and Malisa Vucinic for his input on the ACRE proposal input, and Malisa Vucinic for his input on the ACRE proposal
[I-D.seitz-ace-core-authz] which was one source of inspiration for [I-D.seitz-ace-core-authz] which was one source of inspiration for
this work. Finally, we would like to thank the ACE working group in this work. Finally, we would like to thank the ACE working group in
general for their feedback. general for their feedback.
We would like to thank the authors of draft-ietf-oauth-pop-key-
distribution, from where we copied large parts of our security
considerations.
Ludwig Seitz and Goeran Selander worked on this document as part of Ludwig Seitz and Goeran Selander worked on this document as part of
the CelticPlus project CyberWI, with funding from Vinnova. the CelticPlus project CyberWI, with funding from Vinnova.
12. References 12. References
12.1. Normative References 12.1. Normative References
[I-D.ietf-ace-cbor-web-token] [I-D.ietf-ace-cbor-web-token]
Wahlstroem, E., Jones, M., and H. Tschofenig, "CBOR Web Wahlstroem, E., Jones, M., Tschofenig, H., and S. Erdtman,
Token (CWT)", draft-ietf-ace-cbor-web-token-00 (work in "CBOR Web Token (CWT)", draft-ietf-ace-cbor-web-token-01
progress), May 2016. (work in progress), July 2016.
[I-D.ietf-cose-msg] [I-D.ietf-cose-msg]
Schaad, J., "CBOR Encoded Message Syntax", draft-ietf- Schaad, J., "CBOR Object Signing and Encryption (COSE)",
cose-msg-12 (work in progress), May 2016. draft-ietf-cose-msg-19 (work in progress), September 2016.
[I-D.selander-ace-object-security]
Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security of CoAP (OSCOAP)", draft-selander-ace-
object-security-04 (work in progress), March 2016.
[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,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <http://www.rfc-editor.org/info/rfc6347>. January 2012, <http://www.rfc-editor.org/info/rfc6347>.
skipping to change at page 38, line 51 skipping to change at page 40, line 28
[RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of- [RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of-
Possession Key Semantics for JSON Web Tokens (JWTs)", Possession Key Semantics for JSON Web Tokens (JWTs)",
RFC 7800, DOI 10.17487/RFC7800, April 2016, RFC 7800, DOI 10.17487/RFC7800, April 2016,
<http://www.rfc-editor.org/info/rfc7800>. <http://www.rfc-editor.org/info/rfc7800>.
12.2. Informative References 12.2. Informative References
[I-D.ietf-ace-actors] [I-D.ietf-ace-actors]
Gerdes, S., Seitz, L., Selander, G., and C. Bormann, "An Gerdes, S., Seitz, L., Selander, G., and C. Bormann, "An
architecture for authorization in constrained architecture for authorization in constrained
environments", draft-ietf-ace-actors-03 (work in environments", draft-ietf-ace-actors-04 (work in
progress), March 2016. progress), September 2016.
[I-D.ietf-core-block] [I-D.ietf-oauth-device-flow]
Bormann, C. and Z. Shelby, "Block-wise transfers in CoAP", Denniss, W., Myrseth, S., Bradley, J., Jones, M., and H.
draft-ietf-core-block-20 (work in progress), April 2016. Tschofenig, "OAuth 2.0 Device Flow", draft-ietf-oauth-
device-flow-03 (work in progress), July 2016.
[I-D.ietf-oauth-pop-architecture] [I-D.ietf-oauth-native-apps]
Hunt, P., Richer, J., Mills, W., Mishra, P., and H. Denniss, W. and J. Bradley, "OAuth 2.0 for Native Apps",
Tschofenig, "OAuth 2.0 Proof-of-Possession (PoP) Security draft-ietf-oauth-native-apps-03 (work in progress), July
Architecture", draft-ietf-oauth-pop-architecture-07 (work 2016.
in progress), December 2015.
[I-D.seitz-ace-core-authz] [I-D.seitz-ace-core-authz]
Seitz, L., Selander, G., and M. Vucinic, "Authorization Seitz, L., Selander, G., and M. Vucinic, "Authorization
for Constrained RESTful Environments", draft-seitz-ace- for Constrained RESTful Environments", draft-seitz-ace-
core-authz-00 (work in progress), June 2015. core-authz-00 (work in progress), June 2015.
[I-D.selander-ace-object-security]
Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security of CoAP (OSCOAP)", draft-selander-ace-
object-security-05 (work in progress), July 2016.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", [RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007, FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<http://www.rfc-editor.org/info/rfc4949>. <http://www.rfc-editor.org/info/rfc4949>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>. <http://www.rfc-editor.org/info/rfc5246>.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
skipping to change at page 40, line 19 skipping to change at page 41, line 49
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231, Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014, DOI 10.17487/RFC7231, June 2014,
<http://www.rfc-editor.org/info/rfc7231>. <http://www.rfc-editor.org/info/rfc7231>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<http://www.rfc-editor.org/info/rfc7519>. <http://www.rfc-editor.org/info/rfc7519>.
[RFC7521] Campbell, B., Mortimore, C., Jones, M., and Y. Goland,
"Assertion Framework for OAuth 2.0 Client Authentication
and Authorization Grants", RFC 7521, DOI 10.17487/RFC7521,
May 2015, <http://www.rfc-editor.org/info/rfc7521>.
[RFC7591] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and [RFC7591] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol", P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
RFC 7591, DOI 10.17487/RFC7591, July 2015, RFC 7591, DOI 10.17487/RFC7591, July 2015,
<http://www.rfc-editor.org/info/rfc7591>. <http://www.rfc-editor.org/info/rfc7591>.
[RFC7744] Seitz, L., Ed., Gerdes, S., Ed., Selander, G., Mani, M., [RFC7744] Seitz, L., Ed., Gerdes, S., Ed., Selander, G., Mani, M.,
and S. Kumar, "Use Cases for Authentication and and S. Kumar, "Use Cases for Authentication and
Authorization in Constrained Environments", RFC 7744, Authorization in Constrained Environments", RFC 7744,
DOI 10.17487/RFC7744, January 2016, DOI 10.17487/RFC7744, January 2016,
<http://www.rfc-editor.org/info/rfc7744>. <http://www.rfc-editor.org/info/rfc7744>.
[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016,
<http://www.rfc-editor.org/info/rfc7959>.
Appendix A. Design Justification Appendix A. Design Justification
This section provides further insight into the design decisions of This section provides further insight into the design decisions of
the solution documented in this document. Section 3 lists several the solution documented in this document. Section 3 lists several
building blocks and briefly summarizes their importance. The building blocks and briefly summarizes their importance. The
justification for offering some of those building blocks, as opposed justification for offering some of those building blocks, as opposed
to using OAuth 2.0 as is, is given below. to using OAuth 2.0 as is, is given below.
Common IoT constraints are: Common IoT constraints are:
skipping to change at page 42, line 14 skipping to change at page 44, line 4
security reasons, e.g. to avoid an entry point for Denial-of- security reasons, e.g. to avoid an entry point for Denial-of-
Service attacks. Service attacks.
The communication interactions this framework builds upon (as The communication interactions this framework builds upon (as
shown graphically in Figure 1) may be accomplished using a variety shown graphically in Figure 1) may be accomplished using a variety
of different protocols, and not all parts of the message flow are of different protocols, and not all parts of the message flow are
used in all applications due to the communication constraints. used in all applications due to the communication constraints.
While we envision deployments to make use of CoAP we explicitly While we envision deployments to make use of CoAP we explicitly
want to support HTTP, HTTP/2 or specific protocols, such as want to support HTTP, HTTP/2 or specific protocols, such as
Bluetooth Smart communication, which does not necessarily use IP. Bluetooth Smart communication, which does not necessarily use IP.
The latter raises the need for application layer security over the The latter raises the need for application layer security over the
various interfaces. various interfaces.
Appendix B. Roles and Responsibilites Appendix B. Roles and Responsibilites
Resource Owner Resource Owner
* Make sure that the RS is registered at the AS. * Make sure that the RS is registered at the AS. This includes
making known to the AS which profiles, token_types, scopes, and
key types (symmetric/asymmetric) the RS supports. Also making
it known to the AS which audience(s) the RS identifies itself
with.
* Make sure that clients can discover the AS which is in charge * Make sure that clients can discover the AS which is in charge
of the RS. of the RS.
* Make sure that the AS has the necessary, up-to-date, access * Make sure that the AS has the necessary, up-to-date, access
control policies for the RS. control policies for the RS.
Requesting Party Requesting Party
* Make sure that the client is provisioned the necessary * Make sure that the client is provisioned the necessary
credentials to authenticate to the AS. credentials to authenticate to the AS.
* Make sure that the client is configured to follow the security * Make sure that the client is configured to follow the security
requirements of the Requesting Party, when issuing requests requirements of the Requesting Party, when issuing requests
(e.g. minimum communication security requirements, trust (e.g. minimum communication security requirements, trust
anchors). anchors).
* Register the client at the AS. * Register the client at the AS. This includes making known to
the AS which profiles, token_types, and key types (symmetric/
asymmetric) the client.
Authorization Server Authorization Server
* Register RS and manage corresponding security contexts. * Register RS and manage corresponding security contexts.
* Register clients and including authentication credentials. * Register clients and including authentication credentials.
* Allow Resource Owners to configure and update access control * Allow Resource Owners to configure and update access control
policies related to their registered RS' policies related to their registered RS'
* Expose a service that allows clients to request tokens. * Expose the /token endpoint to allow clients to request tokens.
* Authenticate clients that wishes to request a token. * Authenticate clients that wish to request a token.
* Process a token requests against the authorization policies * Process a token request against the authorization policies
configured for the RS. configured for the RS.
* Expose a service that allows RS's to submit token introspection * Expose the /introspection endpoint that allows RS's to submit
requests. token introspection requests.
* Authenticate RS's that wishes to get an introspection response. * Authenticate RS's that wish to get an introspection response.
* Process token introspection requests. * Process token introspection requests.
* Optionally: Handle token revocation. * Optionally: Handle token revocation.
Client Client
* Discover the AS in charge of the RS that is to be targeted with * Discover the AS in charge of the RS that is to be targeted with
a request. a request.
* Submit the token request (A). * Submit the token request (A).
+ Authenticate towards the AS. + Authenticate towards the AS.
+ Specify which RS, which resource(s), and which action(s) the + Optionally (if not pre-configured): Specify which RS, which
request(s) will target. resource(s), and which action(s) the request(s) will target.
+ Specify preferences for communication security
+ If raw public key (rpk) or certificate is used, make sure + If raw public key (rpk) or certificate is used, make sure
the AS has the right rpk or certificate for this client. the AS has the right rpk or certificate for this client.
* Process the access token and client information (B) * Process the access token and RS Information (B)
+ Check that the token has the right format (e.g. CWT). + Check that the RS Information provides the necessary
+ Check that the client information provides the necessary
security parameters (e.g. PoP key, information on security parameters (e.g. PoP key, information on
communication security protocols supported by the RS). communication security protocols supported by the RS).
* Send the token and request to the RS (C) * Send the token and request to the RS (C)
+ Authenticate towards the RS (this could coincide with the + Authenticate towards the RS (this could coincide with the
proof of possession process). proof of possession process).
+ Transmit the token as specified by the AS (default is to an + Transmit the token as specified by the AS (default is to the
authorization information resource, alternative options are /authz-info endpoint, alternative options are specified by
as a CoAP option or in the DTLS handshake). profiles).
+ Perform the proof-of-possession procedure as specified for + Perform the proof-of-possession procedure as specified by
the type of used token (this may already have been taken the profile in use (this may already have been taken care of
care of through the authentication procedure). through the authentication procedure).
* Process the RS response (F) requirements of the Requesting * Process the RS response (F) requirements of the Requesting
Party, when issuing requests (e.g. minimum communication Party, when issuing requests (e.g. minimum communication
security requirements, trust anchors). security requirements, trust anchors).
* Register the client at the AS. * Register the client at the AS.
Resource Server Resource Server
* Expose a way to submit access tokens. * Expose a way to submit access tokens. By default this is the
/authz-info endpoint.
* Process an access token. * Process an access token.
+ Verify the token is from the right AS. + Verify the token is from the right AS.
+ Verify that the token applies to this RS. + Verify that the token applies to this RS.
+ Check that the token has not expired (if the token provides + Check that the token has not expired (if the token provides
expiration information). expiration information).
+ Check the token's integrity. + Check the token's integrity.
+ Store the token so that it can be retrieved in the context + Store the token so that it can be retrieved in the context
of a matching request. of a matching request.
* Process a request. * Process a request.
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+ Verify the token is from the right AS. + Verify the token is from the right AS.
+ Verify that the token applies to this RS. + Verify that the token applies to this RS.
+ Check that the token has not expired (if the token provides + Check that the token has not expired (if the token provides
expiration information). expiration information).
+ Check the token's integrity. + Check the token's integrity.
+ Store the token so that it can be retrieved in the context + Store the token so that it can be retrieved in the context
of a matching request. of a matching request.
* Process a request. * Process a request.
+ Set up communication security with the client. + Set up communication security with the client.
+ Authenticate the client. + Authenticate the client.
+ Match the client against existing tokens. + Match the client against existing tokens.
+ Check that tokens belonging to the client actually authorize + Check that tokens belonging to the client actually authorize
the requested action. the requested action.
+ Optionally: Check that the matching tokens are still valid + Optionally: Check that the matching tokens are still valid
(if this is possible. (if this is possible.)
* Send a response following the agreed upon communication * Send a response following the agreed upon communication
security. security.
Appendix C. Deployment Examples Appendix C. Requirements on Profiles
This section lists the requirements on profiles of this framework,
for the convenience of a profile designer. All this information is
also given in the appropriate sections of the main document, this is
just meant as a checklist, to make it more easy to spot parts one
might have missed.
o Specify the discovery process of how the client finds the right AS
for an RS it wants to send a request to.
o Specify the communication protocol the client and RS the must use
(e.g. CoAP).
o Specify the security protocol the client and RS must use to
protect their communication (e.g. OSCOAP or DTLS over CoAP).
This must provide encryption and integrity protection.
o Specify how the client and the RS mutually authenticate
o Specify the Content-format of the protocol messages (e.g.
"application/cbor" or "application/cose+cbor").
o Specify the proof-of-possession protocol(s) and how to select one,
if several are available. Also specify which key types (e.g.
symmetric/asymmetric) are supported by a specific proof-of-
possession protocol.
o Specify a unique profile identifier.
o Optionally specify how the RS talks to the AS for introspection.
o Optionally specify how the client talks to the AS for requesting a
token.
o Specify how/if the /authz-info endpoint is protected.
o Optionally define other methods of token transport than the
/authz-info endpoint.
Appendix D. Deployment Examples
There is a large variety of IoT deployments, as is indicated in There is a large variety of IoT deployments, as is indicated in
Appendix A, and this section highlights a few common variants. This Appendix A, and this section highlights a few common variants. This
section is not normative but illustrates how the framework can be section is not normative but illustrates how the framework can be
applied. applied.
For each of the deployment variants there are a number of possible For each of the deployment variants there are a number of possible
security setups between clients, resource servers and authorization security setups between clients, resource servers and authorization
servers. The main focus in the following subsections is on how servers. The main focus in the following subsections is on how
authorization of a client request for a resource hosted by a RS is authorization of a client request for a resource hosted by a RS is
performed. This requires the the security of the requests and performed. This requires the the security of the requests and
responses between the clients and the RS to consider. responses between the clients and the RS to consider.
Note: CBOR diagnostic notation is used for examples of requests and Note: CBOR diagnostic notation is used for examples of requests and
responses. responses.
C.1. Local Token Validation D.1. Local Token Validation
In this scenario we consider the case where the resource server is In this scenario we consider the case where the resource server is
offline, i.e. it is not connected to the AS at the time of the access offline, i.e. it is not connected to the AS at the time of the access
request. This access procedure involves steps A, B, C, and F of request. This access procedure involves steps A, B, C, and F of
Figure 1. Figure 1.
Since the resource server must be able to verify the access token Since the resource server must be able to verify the access token
locally, self-contained access tokens must be used. locally, self-contained access tokens must be used.
This example shows the interactions between a client, the This example shows the interactions between a client, the
authorization server and a temperature sensor acting as a resource authorization server and a temperature sensor acting as a resource
server. Message exchanges A and B are shown in Figure 17. server. Message exchanges A and B are shown in Figure 16.
A: The client first generates a public-private key pair used for A: The client first generates a public-private key pair used for
communication security with the RS. communication security with the RS.
The client sends the POST request to /token at the AS. The The client sends the POST request to /token at the AS. The
request contains the public key of the client and the Audience security of this request can be transport or application layer, it
parameter set to "tempSensorInLivingRoom", a value that the is up the the comunication security profile to define. In the
temperature sensor identifies itself with. The AS evaluates the example trasport layer identification of the AS is done and the
request and authorizes the client to access the resource. client identifies with client_id and client_secret as in classic
OAuth. The request contains the public key of the client and the
B: The AS responds with a PoP token and client information. The Audience parameter set to "tempSensorInLivingRoom", a value that
PoP token contains the public key of the client, and the client the temperature sensor identifies itself with. The AS evaluates
information contains the public key of the RS. For communication the request and authorizes the client to access the resource.
B: The AS responds with a PoP token and RS Information. The PoP
token contains the public key of the client, and the RS
Information contains the public key of the RS. For communication
security this example uses DTLS RawPublicKey between the client security this example uses DTLS RawPublicKey between the client
and the RS. The issued token will have a short validity time, and the RS. The issued token will have a short validity time,
i.e. 'exp' close to 'iat', to protect the RS from replay attacks i.e. 'exp' close to 'iat', to protect the RS from replay attacks.
since it, that cannot do introspection to check the tokens current The token includes the claim such as "scope" with the authorized
validity. The token includes the claim "aif" with the authorized access that an owner of the temperature device can enjoy. In this
access that an owner of the temperature device can enjoy. The example, the 'scope' claim, issued by the AS, informs the RS that
'aif' claim, issued by the AS, informs the RS that the owner of the owner of the token, that can prove the possession of a key is
the token, that can prove the possession of a key is authorized to authorized to make a GET request against the /temperature resource
make a GET request against the /temperature resource and a POST and a POST request on the /firmware resource. Note that the
request on the /firmware resource. syntax and semantics of the scope claim are application specific.
Note: In this example we assume that the client knows what Note: In this example we assume that the client knows what
resource it wants to access, and is therefore able to request resource it wants to access, and is therefore able to request
specific audience and scope claims for the access token. specific audience and scope claims for the access token.
Authorization Authorization
Client Server Client Server
| | | |
|<=======>| DTLS Connection Establishment
| | to identify the AS
| | | |
A: +-------->| Header: POST (Code=0.02) A: +-------->| Header: POST (Code=0.02)
| POST | Uri-Path:"token" | POST | Uri-Path:"token"
| | Content-Type: application/cbor | | Content-Type: application/cbor
| | Payload: <Request-Payload> | | Payload: <Request-Payload>
| | | |
B: |<--------+ Header: 2.05 Content B: |<--------+ Header: 2.05 Content
| 2.05 | Content-Type: application/cbor | 2.05 | Content-Type: application/cbor
| | Payload: <Response-Payload> | | Payload: <Response-Payload>
| | | |
Figure 17: Token Request and Response Using Client Credentials. Figure 16: Token Request and Response Using Client Credentials.
The information contained in the Request-Payload and the Response- The information contained in the Request-Payload and the Response-
Payload is shown in Figure 18. Payload is shown in Figure 17. Note that we assume a DTLS-based
communication security profile for this example, therefore the
Content-Type is "application/cbor".
Request-Payload : Request-Payload :
{ {
"grant_type" : "client_credentials", "grant_type" : "client_credentials",
"aud" : "tempSensorInLivingRoom", "aud" : "tempSensorInLivingRoom",
"client_id" : "myclient", "client_id" : "myclient",
"client_secret" : "qwerty" "client_secret" : "qwerty"
} }
Response-Payload : Response-Payload :
skipping to change at page 46, line 29 skipping to change at page 48, line 52
"COSE_Key" : { "COSE_Key" : {
"kid" : b64'c29tZSBwdWJsaWMga2V5IGlk', "kid" : b64'c29tZSBwdWJsaWMga2V5IGlk',
"kty" : "EC", "kty" : "EC",
"crv" : "P-256", "crv" : "P-256",
"x" : b64'MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4', "x" : b64'MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4',
"y" : b64'4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM' "y" : b64'4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM'
} }
} }
} }
Figure 18: Request and Response Payload Details. Figure 17: Request and Response Payload Details.
The content of the access token is shown in Figure 19. The content of the access token is shown in Figure 18.
{ {
"aud" : "tempSensorInLivingRoom", "aud" : "tempSensorInLivingRoom",
"iat" : "1360189224", "iat" : "1360189224",
"exp" : "1360289224", "exp" : "1360289224",
"aif" : [["/temperature", 0], ["/firmware", 2]], "scope" : "temperature_g firmware_p",
"cnf" : { "cnf" : {
"jwk" : { "jwk" : {
"kid" : b64'1Bg8vub9tLe1gHMzV76e8', "kid" : b64'1Bg8vub9tLe1gHMzV76e8',
"kty" : "EC", "kty" : "EC",
"crv" : "P-256", "crv" : "P-256",
"x" : b64'f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU', "x" : b64'f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU',
"y" : b64'x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0' "y" : b64'x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0'
} }
} }
} }
Figure 19: Access Token including Public Key of the Client. Figure 18: Access Token including Public Key of the Client.
Messages C and F are shown in Figure 20 - Figure 21. Messages C and F are shown in Figure 19 - Figure 20.
C: The client then sends the PoP token to the /authz-info resource C: The client then sends the PoP token to the /authz-info endpoint
at the RS. This is a plain CoAP request, i.e. no transport or at the RS. This is a plain CoAP request, i.e. no transport or
application layer security between client and RS, since the token application layer security between client and RS, since the token
is integrity protected between AS and RS. The RS verifies that is integrity protected between AS and RS. The RS verifies that
the PoP token was created by a known and trusted AS, is valid, and the PoP token was created by a known and trusted AS, is valid, and
responds to the client. The RS caches the security context responds to the client. The RS caches the security context
together with authorization information about this client together with authorization information about this client
contained in the PoP token. contained in the PoP token.
Resource Resource
Client Server Client Server
| | | |
C: +-------->| Header: POST (Code=0.02) C: +-------->| Header: POST (Code=0.02)
| POST | Uri-Path:"authz-info" | POST | Uri-Path:"authz-info"
| | Payload: SlAV32hkKG ... | | Payload: SlAV32hkKG ...
| | | |
|<--------+ Header: 2.01 Created |<--------+ Header: 2.04 Changed
| 2.01 | | 2.04 |
| | | |
Figure 20: Access Token provisioning to RS Figure 19: Access Token provisioning to RS
The client and the RS runs the DTLS handshake using the raw public The client and the RS runs the DTLS handshake using the raw public
keys established in step B and C. keys established in step B and C.
The client sends the CoAP request GET to /temperature on RS over The client sends the CoAP request GET to /temperature on RS over
DTLS. The RS verifies that the request is authorized, based on DTLS. The RS verifies that the request is authorized, based on
previously established security context. previously established security context.
F: The RS responds with a resource representation over DTLS. F: The RS responds with a resource representation over DTLS.
Resource Resource
Client Server Client Server
| | | |
|<=======>| DTLS Connection Establishment |<=======>| DTLS Connection Establishment
| | using Raw Public Keys | | using Raw Public Keys
skipping to change at page 47, line 48 skipping to change at page 50, line 25
| | | |
+-------->| Header: GET (Code=0.01) +-------->| Header: GET (Code=0.01)
| GET | Uri-Path: "temperature" | GET | Uri-Path: "temperature"
| | | |
| | | |
| | | |
F: |<--------+ Header: 2.05 Content F: |<--------+ Header: 2.05 Content
| 2.05 | Payload: <sensor value> | 2.05 | Payload: <sensor value>
| | | |
Figure 21: Resource Request and Response protected by DTLS. Figure 20: Resource Request and Response protected by DTLS.
C.2. Introspection Aided Token Validation D.2. Introspection Aided Token Validation
In this deployment scenario we assume that a client is not be able to In this deployment scenario we assume that a client is not able to
access the AS at the time of the access request. Since the RS is, access the AS at the time of the access request. Since the RS is,
however, connected to the back-end infrastructure it can make use of however, connected to the back-end infrastructure it can make use of
token introspection. This access procedure involves steps A-F of token introspection. This access procedure involves steps A-F of
Figure 1, but assumes steps A and B have been carried out during a Figure 1, but assumes steps A and B have been carried out during a
phase when the client had connectivity to AS. phase when the client had connectivity to AS.
Since the client is assumed to be offline, at least for a certain Since the client is assumed to be offline, at least for a certain
period of time, a pre-provisioned access token has to be long-lived. period of time, a pre-provisioned access token has to be long-lived.
The resource server may use its online connectivity to validate the The resource server may use its online connectivity to validate the
access token with the authorization server, which is shown in the access token with the authorization server, which is shown in the
example below. example below.
In the example we show the interactions between an offline client In the example interactions between an offline client (key fob), a RS
(key fob), a resource server (online lock), and an authorization (online lock), and an AS is shown. We assume that there is a
server. We assume that there is a provisioning step where the client provisioning step where the client has access to the AS. This
has access to the AS. This corresponds to message exchanges A and B corresponds to message exchanges A and B which are shown in
which are shown in Figure 22. Figure 21.
Authorization consent from the resource owner can be pre-configured, Authorization consent from the resource owner can be pre-configured,
but it can also be provided via an interactive flow with the resource but it can also be provided via an interactive flow with the resource
owner. An example of this for the key fob case could be that the owner. An example of this for the key fob case could be that the
resource owner has a connected car, he buys a generic key that he resource owner has a connected car, he buys a generic key that he
wants to use with the car. To authorize the key fob he connects it wants to use with the car. To authorize the key fob he connects it
to his computer that then provides the UI for the device. After that to his computer that then provides the UI for the device. After that
OAuth 2.0 implicit flow can used to authorize the key for his car at OAuth 2.0 implicit flow can used to authorize the key for his car at
the the car manufacturers AS. the the car manufacturers AS.
skipping to change at page 48, line 46 skipping to change at page 51, line 19
be used to access since the token request is not send at the time of be used to access since the token request is not send at the time of
access. So the scope and audience parameters is set quite wide to access. So the scope and audience parameters is set quite wide to
start with and new values different form the original once can be start with and new values different form the original once can be
returned from introspection later on. returned from introspection later on.
A: The client sends the request using POST to /token at AS. The A: The client sends the request using POST to /token at AS. The
request contains the Audience parameter set to "PACS1337" (PACS, request contains the Audience parameter set to "PACS1337" (PACS,
Physical Access System), a value the that the online door in Physical Access System), a value the that the online door in
question identifies itself with. The AS generates an access token question identifies itself with. The AS generates an access token
as on opaque string, which it can match to the specific client, a as on opaque string, which it can match to the specific client, a
targeted audience and a symmetric key. targeted audience and a symmetric key. The security is provided
B: The AS responds with the an access token and client by identifying the AS on transport layer using a pre shared
information, the latter containing a symmetric key. Communication security context (psk, rpk or certificate) and then the client is
security between C and RS will be DTLS and PreSharedKey. The PoP identified using client_id and client_secret as in classic OAuth
key being used as the PreSharedKey. B: The AS responds with the an access token and RS Information,
the latter containing a symmetric key. Communication security
between C and RS will be DTLS and PreSharedKey. The PoP key being
used as the PreSharedKey.
Authorization Authorization
Client Server Client Server
| | | |
| | | |
A: +-------->| Header: POST (Code=0.02) A: +-------->| Header: POST (Code=0.02)
| POST | Uri-Path:"token" | POST | Uri-Path:"token"
| | Content-Type: application/cbor | | Content-Type: application/cbor
| | Payload: <Request-Payload> | | Payload: <Request-Payload>
| | | |
B: |<--------+ Header: 2.05 Content B: |<--------+ Header: 2.05 Content
| | Content-Type: application/cbor | | Content-Type: application/cbor
| 2.05 | Payload: <Response-Payload> | 2.05 | Payload: <Response-Payload>
| | | |
Figure 22: Token Request and Response using Client Credentials. Figure 21: Token Request and Response using Client Credentials.
The information contained in the Request-Payload and the Response- The information contained in the Request-Payload and the Response-
Payload is shown in Figure 23. Payload is shown in Figure 22.
Request-Payload: Request-Payload:
{ {
"grant_type" : "client_credentials", "grant_type" : "client_credentials",
"aud" : "lockOfDoor4711", "aud" : "lockOfDoor4711",
"client_id" : "keyfob", "client_id" : "keyfob",
"client_secret" : "qwerty" "client_secret" : "qwerty"
} }
Response-Payload: Response-Payload:
skipping to change at page 49, line 47 skipping to change at page 52, line 28
"cnf" : { "cnf" : {
"COSE_Key" : { "COSE_Key" : {
"kid" : b64'c29tZSBwdWJsaWMga2V5IGlk', "kid" : b64'c29tZSBwdWJsaWMga2V5IGlk',
"kty" : "oct", "kty" : "oct",
"alg" : "HS256", "alg" : "HS256",
"k": b64'ZoRSOrFzN_FzUA5XKMYoVHyzff5oRJxl-IXRtztJ6uE' "k": b64'ZoRSOrFzN_FzUA5XKMYoVHyzff5oRJxl-IXRtztJ6uE'
} }
} }
} }
Figure 23: Request and Response Payload for C offline Figure 22: Request and Response Payload for C offline
The access token in this case is just an opaque string referencing The access token in this case is just an opaque string referencing
the authorization information at the AS. the authorization information at the AS.
C: Next, the client POSTs the access token to the /authz-info C: Next, the client POSTs the access token to the /authz-info
resource in the RS. This is a plain CoAP request, i.e. no DTLS endpoint in the RS. This is a plain CoAP request, i.e. no DTLS
between client and RS. Since the token is an opaque string, the between client and RS. Since the token is an opaque string, the
RS cannot verify it on its own, and thus defers to respond the RS cannot verify it on its own, and thus defers to respond the
client with a status code until after step E. client with a status code until after step E.
D: The RS forwards the token to the /introspect resource on the D: The RS forwards the token to the /introspect endpoint on the
AS. Introspection assumes a secure connection between the AS and AS. Introspection assumes a secure connection between the AS and
the RS, e.g. using transport of application layer security, which the RS, e.g. using transport of application layer security. In
is not detailed in this example. the example AS is identified using pre shared security context
(psk, rpk or certificate) while RS is acting as client and is
identified with client_id and client_secret.
E: The AS provides the introspection response containing E: The AS provides the introspection response containing
parameters about the token. This includes the confirmation key parameters about the token. This includes the confirmation key
(cnf) parameter that allows the RS to verify the client's proof of (cnf) parameter that allows the RS to verify the client's proof of
possession in step F. possession in step F.
After receiving message E, the RS responds to the client's POST in After receiving message E, the RS responds to the client's POST in
step C with Code 2.01 Created. step C with the CoAP response code 2.01 (Created).
Resource Resource
Client Server Client Server
| | | |
C: +-------->| Header: POST (T=CON, Code=0.02) C: +-------->| Header: POST (T=CON, Code=0.02)
| POST | Uri-Path:"authz-info" | POST | Uri-Path:"authz-info"
| | Content-Type: "application/cbor" | | Content-Type: "application/cbor"
| | Payload: b64'SlAV32hkKG ...'' | | Payload: b64'SlAV32hkKG ...''
| | | |
| | Authorization | | Authorization
| | Server | | Server
| | | | | |
D: | +--------->| Header: POST (Code=0.02) | D: +--------->| Header: POST (Code=0.02)
| | POST | Uri-Path: "introspect" | | POST | Uri-Path: "introspect"
| | | Content-Type: "application/cbor" | | | Content-Type: "application/cbor"
| | | Payload: <Request-Payload> | | | Payload: <Request-Payload>
| | | | | |
E: | |<---------+ Header: 2.05 Content | E: |<---------+ Header: 2.05 Content
| | 2.05 | Content-Type: "application/cbor" | | 2.05 | Content-Type: "application/cbor"
| | | Payload: <Response-Payload> | | | Payload: <Response-Payload>
| | | | | |
| | | |
C: |<--------+ Header: 2.01 Created |<--------+ Header: 2.01 Created
| 2.01 | | 2.01 |
| | | |
Figure 24: Token Introspection for C offline Figure 23: Token Introspection for C offline
The information contained in the Request-Payload and the Response- The information contained in the Request-Payload and the Response-
Payload is shown in Figure 25. Payload is shown in Figure 24.
Request-Payload: Request-Payload:
{ {
"token" : b64'SlAV32hkKG...', "token" : b64'SlAV32hkKG...',
"client_id" : "FrontDoor", "client_id" : "FrontDoor",
"client_secret" : "ytrewq" "client_secret" : "ytrewq"
} }
Response-Payload: Response-Payload:
{ {
"active" : true, "active" : true,
"aud" : "lockOfDoor4711", "aud" : "lockOfDoor4711",
"scope" : "open, close", "scope" : "open, close",
"iat" : 1311280970, "iat" : 1311280970,
"cnf" : { "cnf" : {
"kid" : b64'JDLUhTMjU2IiwiY3R5Ijoi ...' "kid" : b64'JDLUhTMjU2IiwiY3R5Ijoi ...'
} }
} }
Figure 25: Request and Response Payload for Introspection Figure 24: Request and Response Payload for Introspection
The client uses the symmetric PoP key to establish a DTLS The client uses the symmetric PoP key to establish a DTLS
PreSharedKey secure connection to the RS. The CoAP request PUT is PreSharedKey secure connection to the RS. The CoAP request PUT is
sent to the uri-path /state on RS changing state of the door to sent to the uri-path /state on RS changing state of the door to
locked. locked.
F: The RS responds with a appropriate over the secure DTLS F: The RS responds with a appropriate over the secure DTLS
channel. channel.
Resource Resource
Client Server Client Server
skipping to change at page 51, line 46 skipping to change at page 54, line 26
| | using Pre Shared Key | | using Pre Shared Key
| | | |
+-------->| Header: PUT (Code=0.03) +-------->| Header: PUT (Code=0.03)
| PUT | Uri-Path: "state" | PUT | Uri-Path: "state"
| | Payload: <new state for the lock> | | Payload: <new state for the lock>
| | | |
F: |<--------+ Header: 2.04 Changed F: |<--------+ Header: 2.04 Changed
| 2.04 | Payload: <new state for the lock> | 2.04 | Payload: <new state for the lock>
| | | |
Figure 26: Resource request and response protected by OSCOAP Figure 25: Resource request and response protected by OSCOAP
Appendix D. Document Updates Appendix E. Document Updates
D.1. Version -01 to -02
E.1. Version -02 to -03
o Removed references to draft-ietf-oauth-pop-key-distribution since
the status of this draft is unclear.
o Copied and adapted security considerations from draft-ietf-oauth-
pop-key-distribution.
o Renamed "client information" to "RS information" since it is
information about the RS.
o Clarified the requirements on profiles of this framework.
o Clarified the token endpoint protocol and removed negotiation of
'profile' and 'alg' (section 6).
o Renumbered the abbreviations for claims and parameters to get a
consistent numbering across different endpoints.
o Clarified the introspection endpoint.
o Renamed token, introspection and authz-info to 'endpoint' instead
of 'resource' to mirror the OAuth 2.0 terminology.
o Updated the examples in the appendices.
E.2. Version -01 to -02
o Restructured to remove communication security parts. These shall o Restructured to remove communication security parts. These shall
now be defined in profiles. now be defined in profiles.
o Restructured section 5 to create new sections on the OAuth o Restructured section 5 to create new sections on the OAuth
endpoints /token, /introspect and /authz-info. endpoints /token, /introspect and /authz-info.
o Pulled in material from draft-ietf-oauth-pop-key-distribution in o Pulled in material from draft-ietf-oauth-pop-key-distribution in
order to define proof-of-possession key distribution. order to define proof-of-possession key distribution.
o Introduced the 'cnf' parameter as defined in RFC7800 to reference o Introduced the 'cnf' parameter as defined in RFC7800 to reference
or transport keys used for proof of posession. or transport keys used for proof of posession.
o Introduced the 'client-token' to transport client information from o Introduced the 'client-token' to transport client information from
the AS to the client via the RS in conjunction with introspection. the AS to the client via the RS in conjunction with introspection.
o Expanded the IANA section to define parameters for token request, o Expanded the IANA section to define parameters for token request,
introspection and CWT claims. introspection and CWT claims.
skipping to change at page 52, line 20 skipping to change at page 55, line 17
o Pulled in material from draft-ietf-oauth-pop-key-distribution in o Pulled in material from draft-ietf-oauth-pop-key-distribution in
order to define proof-of-possession key distribution. order to define proof-of-possession key distribution.
o Introduced the 'cnf' parameter as defined in RFC7800 to reference o Introduced the 'cnf' parameter as defined in RFC7800 to reference
or transport keys used for proof of posession. or transport keys used for proof of posession.
o Introduced the 'client-token' to transport client information from o Introduced the 'client-token' to transport client information from
the AS to the client via the RS in conjunction with introspection. the AS to the client via the RS in conjunction with introspection.
o Expanded the IANA section to define parameters for token request, o Expanded the IANA section to define parameters for token request,
introspection and CWT claims. introspection and CWT claims.
o Moved deployment scenarios to the appendix as examples. o Moved deployment scenarios to the appendix as examples.
D.2. Version -00 to -01 E.3. Version -00 to -01
o Changed 5.1. from "Communication Security Protocol" to "Client o Changed 5.1. from "Communication Security Protocol" to "Client
Information". Information".
o Major rewrite of 5.1 to clarify the information exchanged between o Major rewrite of 5.1 to clarify the information exchanged between
C and AS in the PoP token request profile for IoT. C and AS in the PoP token request profile for IoT.
* Allow the client to indicate preferences for the communication * Allow the client to indicate preferences for the communication
security protocol. security protocol.
* Defined the term "Client Information" for the additional * Defined the term "Client Information" for the additional
information returned to the client in addition to the access information returned to the client in addition to the access
skipping to change at page 53, line 24 skipping to change at page 56, line 24
Goeran Selander Goeran Selander
Ericsson Ericsson
Faroegatan 6 Faroegatan 6
Kista 164 80 Kista 164 80
SWEDEN SWEDEN
Email: goran.selander@ericsson.com Email: goran.selander@ericsson.com
Erik Wahlstroem Erik Wahlstroem
Nexus Technology
Telefonvagen 26
Hagersten 126 26
Sweden Sweden
Email: erik.wahlstrom@nexusgroup.com Email: erik@wahlstromtekniska.se
Samuel Erdtman Samuel Erdtman
Spotify AB Spotify AB
Birger Jarlsgatan 61, 4tr Birger Jarlsgatan 61, 4tr
Stockholm 113 56 Stockholm 113 56
Sweden Sweden
Email: erdtman@spotify.com Email: erdtman@spotify.com
Hannes Tschofenig Hannes Tschofenig
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