Short Distribution Chain (SDC) Workflow and New OAuth Parameters for the Authentication and Authorization for Constrained Environments (ACE) Framework
draft-ietf-ace-workflow-and-params-07
| Document | Type | Active Internet-Draft (ace WG) | |
|---|---|---|---|
| Authors | Marco Tiloca , Göran Selander | ||
| Last updated | 2026-03-02 | ||
| Replaces | draft-tiloca-ace-workflow-and-params | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
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draft-ietf-ace-workflow-and-params-07
ACE Working Group M. Tiloca
Internet-Draft RISE AB
Updates: 9200, 9201, 9202, 9203, 9431 (if G. Selander
approved) Ericsson AB
Intended status: Standards Track 2 March 2026
Expires: 3 September 2026
Short Distribution Chain (SDC) Workflow and New OAuth Parameters for the
Authentication and Authorization for Constrained Environments (ACE)
Framework
draft-ietf-ace-workflow-and-params-07
Abstract
This document updates the Authentication and Authorization for
Constrained Environments framework (ACE, RFC 9200) as follows. (1) It
defines the Short Distribution Chain (SDC) workflow that the
authorization server (AS) can use for uploading an access token to a
resource server on behalf of the client. (2) For the OAuth 2.0 token
endpoint, it defines new parameters and encodings and it extends the
semantics of the "ace_profile" parameter. (3) For the OAuth 2.0
authz-info endpoint, it defines a new parameter and its encoding. (4)
It defines how the client and the AS can coordinate on the exchange
of the client's and resource server's public authentication
credentials, when those can be transported by value or identified by
reference; this extends the semantics of the "rs_cnf" parameter for
the OAuth 2.0 token endpoint, thus updating RFC 9201. (5) It extends
the error handling at the AS, for which it defines a new error code.
(6) It deprecates the original payload format of error responses
conveying an error code, when CBOR is used to encode message
payloads. For those responses, it defines a new payload format
aligned with RFC 9290, thus updating in this respect also the
profiles defined in RFC 9202, RFC 9203, and RFC 9431. (7) It amends
two of the requirements on profiles of the framework.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-ace-workflow-and-params/.
Discussion of this document takes place on the Authentication and
Authorization for Constrained Environments (ace) Working Group
mailing list (mailto:ace@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/ace/. Subscribe at
https://www.ietf.org/mailman/listinfo/ace/.
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Source for this draft and an issue tracker can be found at
https://github.com/ace-wg/ace-workflow-and-params.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 3 September 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
2. The Short Distribution Chain (SDC) Workflow . . . . . . . . . 7
2.1. Token Upload . . . . . . . . . . . . . . . . . . . . . . 11
3. New Parameters . . . . . . . . . . . . . . . . . . . . . . . 12
3.1. token_upload . . . . . . . . . . . . . . . . . . . . . . 12
3.1.1. Examples . . . . . . . . . . . . . . . . . . . . . . 14
3.2. token_hash . . . . . . . . . . . . . . . . . . . . . . . 18
3.2.1. Computing the Token Hash . . . . . . . . . . . . . . 19
3.2.2. Example . . . . . . . . . . . . . . . . . . . . . . . 20
3.3. to_rs and from_rs . . . . . . . . . . . . . . . . . . . . 22
3.3.1. to_rs . . . . . . . . . . . . . . . . . . . . . . . . 22
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3.3.2. from_rs . . . . . . . . . . . . . . . . . . . . . . . 25
3.3.3. Use with the OSCORE Profile . . . . . . . . . . . . . 26
3.4. rs_cnf2 and audience2 . . . . . . . . . . . . . . . . . . 29
3.4.1. Example . . . . . . . . . . . . . . . . . . . . . . . 31
3.5. anchor_cnf . . . . . . . . . . . . . . . . . . . . . . . 32
3.5.1. Example . . . . . . . . . . . . . . . . . . . . . . . 33
3.6. token_series_id . . . . . . . . . . . . . . . . . . . . . 34
3.7. updated_rights . . . . . . . . . . . . . . . . . . . . . 37
4. Updated "ace_profile" Parameter . . . . . . . . . . . . . . . 40
5. Coordinating on the Exchange of Public Authentication
Credentials . . . . . . . . . . . . . . . . . . . . . . . 41
5.1. Instructing C on How to Provide its Authentication
Credential . . . . . . . . . . . . . . . . . . . . . . . 42
5.2. Instructing the AS on How to Provide the RS's
Authentication Credential . . . . . . . . . . . . . . . . 42
6. Failed Verification of Proof of Possession at the AS . . . . 44
7. Updated Payload Format of Error Responses . . . . . . . . . . 45
8. Updated Requirements on Profiles of ACE . . . . . . . . . . . 47
9. Security Considerations . . . . . . . . . . . . . . . . . . . 47
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 48
10.1. OAuth Parameters Registry . . . . . . . . . . . . . . . 48
10.2. OAuth Parameters CBOR Mappings Registry . . . . . . . . 51
10.3. JSON Web Token Claims Registry . . . . . . . . . . . . . 54
10.4. CBOR Web Token (CWT) Claims Registry . . . . . . . . . . 54
10.5. OAuth Extensions Error Registry . . . . . . . . . . . . 54
10.6. OAuth Error Code CBOR Mappings Registry . . . . . . . . 55
10.7. Custom Problem Detail Keys Registry . . . . . . . . . . 55
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 56
11.1. Normative References . . . . . . . . . . . . . . . . . . 56
11.2. Informative References . . . . . . . . . . . . . . . . . 59
Appendix A. Benefits for ACE Profiles . . . . . . . . . . . . . 60
A.1. DTLS Profile . . . . . . . . . . . . . . . . . . . . . . 60
A.2. EDHOC and OSCORE Profile . . . . . . . . . . . . . . . . 61
Appendix B. CDDL Model . . . . . . . . . . . . . . . . . . . . . 61
Appendix C. Document Updates . . . . . . . . . . . . . . . . . . 61
C.1. Version -06 to -07 . . . . . . . . . . . . . . . . . . . 62
C.2. Version -05 to -06 . . . . . . . . . . . . . . . . . . . 62
C.3. Version -04 to -05 . . . . . . . . . . . . . . . . . . . 63
C.4. Version -03 to -04 . . . . . . . . . . . . . . . . . . . 63
C.5. Version -02 to -03 . . . . . . . . . . . . . . . . . . . 63
C.6. Version -01 to -02 . . . . . . . . . . . . . . . . . . . 64
C.7. Version -00 to -01 . . . . . . . . . . . . . . . . . . . 64
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 65
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 65
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1. Introduction
The Authentication and Authorization for Constrained Environments
(ACE) framework [RFC9200] defines an architecture to enforce access
control for constrained devices. A client (C) requests an assertion
of granted permissions from an authorization server (AS) in the form
of an access token, then uploads the access token to the target
resource server (RS), and finally accesses protected resources at the
RS according to the permissions specified in the access token.
The framework has as main building blocks the OAuth 2.0 framework
[RFC6749], the Constrained Application Protocol (CoAP) [RFC7252] for
message transfer, Concise Binary Object Representation (CBOR)
[RFC8949] for compact encoding, and CBOR Object Signing and
Encryption (COSE) [RFC9052][RFC9053] for self-contained protection of
access tokens. In addition, separate profile documents define in
detail how the participants in the ACE architecture communicate,
especially as to the security protocols that they use.
The present document updates [RFC9200] as follows.
* It defines the Short Distribution Chain (SDC) workflow for the ACE
framework (see Section 2 of the present document), according to
which the AS uploads the access token to the RS on behalf of C and
then informs C about the outcome. The SDC workflow is especially
convenient in deployments where the communication leg between C
and the RS is constrained, but the communication leg between the
AS and the RS is not.
The SDC workflow has no ambition to replace the original workflow
defined in [RFC9200]. The AS can use one workflow or the other,
depending, for example, on the specific RS for which an access
token has been issued and the nature of the communication leg with
that RS.
* It defines new parameters and encodings for the OAuth 2.0 token
endpoint at the AS (see Section 3 of the present document). These
include:
- "token_upload", used by C to inform the AS that it opts in to
use the SDC workflow and by the AS to inform C about the
outcome of the token uploading to the RS per the SDC workflow.
- "token_hash", used by the AS to provide C with a token hash,
which corresponds to an access token that the AS has issued for
C and has successfully uploaded to the RS on behalf of C per
the SDC workflow.
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- "to_rs", used by C to provide the AS with information to relay
to the RS, upon asking the AS to upload the access token to the
RS per the SDC workflow. Its specific use with the OSCORE
profile [RFC9203] is also described, as effectively enabling
the use of the SDC workflow for that profile.
- "from_rs", used by the AS to provide C with information to
relay from the RS, after the AS has successfully uploaded the
access token to the RS per the SDC workflow. Its specific use
with the OSCORE profile [RFC9203] is also described, as
effectively enabling the use of the SDC workflow for that
profile.
- "rs_cnf2", used by the AS to provide C with the public keys of
the RSs in the group-audience for which the access token is
issued (see Section 6.9 of [RFC9200]).
- "audience2", used by the AS to provide C with the identifiers
of the RSs in the group-audience for which the access token is
issued.
- "anchor_cnf", used by the AS to provide C with the public keys
of trust anchors, which C can use to validate the public key of
an RS (e.g., as provided in the "rs_cnf" parameter defined in
[RFC9201] or in the "rs_cnf2" parameter defined in the present
document).
- "token_series_id", used by the AS to provide C with the binary
identifier of a token series and by C to ask the AS for a new
access token in the same token series that dynamically updates
access rights. A corresponding access token claim, namely
"token_series_id", is also defined.
- "updated_rights", used by the AS to provide the RS with an
indication that an access token uploaded per the SDC workflow
is not the first one of a new token series, i.e., that the AS
has issued the access token for dynamically updating the access
rights of C.
* It extends the semantics of the "ace_profile" parameter for the
OAuth 2.0 token endpoint at the authorization server defined in
[RFC9200] (see Section 4 of the present document).
* It defines how C and the AS can coordinate on the exchange of the
client's and resource server's public authentication credentials,
when those can be transported by value or identified by reference
in the access token request and response (see Section 5 of the
present document).
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This extends the semantics of the "rs_cnf" parameter for the OAuth
2.0 token endpoint defined in Section 3.2 of [RFC9201].
Therefore, it updates [RFC9201].
* It extends the error handling at the AS, for which it defines a
new error code that the AS can use for error responses sent to the
client, after failing to verify the proof of possession of the
client's private key when processing an access token request (see
Section 6 of the present document).
* It deprecates the original payload format of error responses that
convey an error code, when CBOR is used to encode message payloads
in the ACE framework. For such error responses, it defines a new
payload format according to the problem-details format specified
in [RFC9290] (see Section 7 of the present document).
In this respect, it also updates the profiles of the ACE framework
defined in [RFC9202], [RFC9203], and [RFC9431].
* It amends two of the requirements on profiles of the ACE framework
originally compiled in Appendix C of [RFC9200] (see Section 8 of
the present document).
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Readers are expected to be familiar with the terms and concepts
related to the ACE framework for Authentication and Authorization
[RFC9200][RFC9201], as well as with terms and concepts related to
CBOR Web Tokens (CWTs) [RFC8392] and CWT Confirmation Methods
[RFC8747].
The terminology for entities in the considered architecture is
defined in OAuth 2.0 [RFC6749]. In particular, this includes client
(C), resource server (RS), and authorization server (AS).
Readers are also expected to be familiar with the terms and concepts
related to CoAP [RFC7252], Concise Data Definition Language (CDDL)
[RFC8610], CBOR [RFC8949], JavaScript Object Notation (JSON)
[RFC8259], and COSE [RFC9052][RFC9053].
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Note that the term "endpoint" is used here following its OAuth
definition [RFC6749], aimed at denoting resources such as /token and
/introspect at the AS, and /authz-info at the RS. The CoAP
definition, which is "[a]n entity participating in the CoAP protocol"
[RFC7252], is not used in this document.
Furthermore, this document uses the following terms.
* Token series: a set of access tokens, all of which are bound to
the same proof-of-possession (PoP) key and are sequentially issued
by the same AS for the same pair (client, audience) per the same
profile of ACE. A token series ends when the latest access token
of that token series becomes invalid (e.g., when it expires or
gets revoked).
Profiles of ACE can provide their extended and specialized
definition, e.g., by further taking into account the public
authentication credentials of C and the RS.
* Token hash: identifier of an access token, in binary format
encoding. The token hash has no relation with other access token
identifiers possibly used, such as the 'cti' (CWT ID) claim of
CWTs [RFC8392].
CBOR [RFC8949] and CDDL [RFC8610] are used in this document. CDDL
predefined type names, especially bstr for CBOR byte strings and tstr
for CBOR text strings, are used extensively in this document.
Examples throughout this document are expressed in CBOR diagnostic
notation as defined in Section 8 of [RFC8949] and Appendix G of
[RFC8610]. Diagnostic notation comments are often used to provide a
textual representation of the parameters' keys and values.
In the CBOR diagnostic notation used in this document, constructs of
the form e'SOME_NAME' are replaced by the value assigned to SOME_NAME
in the CDDL model shown in Figure 11 of Appendix B. For example,
{e'audience2' : ["rs1", "rs2"]} stands for {54 : ["rs1", "rs2"]}.
Note to RFC Editor: Please delete the paragraph immediately preceding
this note. Also, in the CBOR diagnostic notation used in this
document, please replace the constructs of the form e'SOME_NAME' with
the value assigned to SOME_NAME in the CDDL model shown in Figure 11
of Appendix B. Finally, please delete this note.
2. The Short Distribution Chain (SDC) Workflow
As defined in Section 4 of [RFC9200], the ACE framework relies on its
basic protocol workflow shown in Figure 1.
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That is, the client first sends an access token request to the token
endpoint at the AS (Step A), specifying permissions that it seeks to
obtain for accessing protected resources at the RS, possibly together
with information on its own public authentication credential.
Then, if the request is successfully verified, authenticated, and
authorized, the AS replies to the client with an access token
response (Step B), providing an access token and possibly additional
parameters as access information including the actually granted
permissions.
Finally, the client uploads the access token to the RS and,
consistently with the permissions granted according to the access
token, accesses a resource at the RS (Step C), which replies with the
result of the resource access (Step F). Details about what protocol
the client and the RS use to establish a secure association, mutually
authenticate, and secure their communications are defined in the
specific profile of ACE used, e.g., [RFC9202][RFC9203][RFC9431][I-D.i
etf-ace-edhoc-oscore-profile][I-D.ietf-ace-group-oscore-profile].
Further interactions are possible between the AS and the RS, i.e.,
the exchange of an introspection request and response where the AS
validates a previously issued access token for the RS (Steps D and
E).
+--------+ +---------------+
| |---(A)-- Token Request ------->| |
| | | Authorization |
| |<--(B)-- Access Token ---------| Server |
| | + Access Information | |
| | + Refresh Token (optional) +---------------+
| | ^ |
| | Introspection Request (D)| |
| Client | Response | |(E)
| | (optional exchange) | |
| | | v
| | +--------------+
| |---(C)-- Token + Request ----->| |
| | | Resource |
| |<--(F)-- Protected Resource ---| Server |
| | | |
+--------+ +--------------+
Figure 1: ACE Basic Protocol Workflow.
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This section defines the alternative Short Distribution Chain (SDC)
workflow shown in Figure 2, which MAY be supported by the AS. Unlike
in the original workflow defined in [RFC9200], the AS uploads the
access token to the RS on behalf of the client and then informs the
client about the outcome.
If the token uploading has been successfully completed, the client
typically does not need to obtain the access token from the AS
altogether. That is, the client simply establishes a secure
association with the RS (if that has not happened already) and then
accesses protected resources at the RS, according to the permissions
granted per the access token and specified by the AS as access
information.
+--------+ +----------------------------+
| |---(A)-- Token Request ------->| |
| | | Authorization |
| |<--(B)-- Token Response -------| Server |
| | + Access Information | |
| | + Access Token (optional) +----------------------------+
| | + Refresh Token (optional) ^ | | ^
| | | | | | Token-Upload
| | Introspection Request (D)| | (A1)| | Request
| Client | Response | |(E) | |(A2) Response
| | (optional exchange) | | | |
| | | v v |
| | +----------------------------+
| |---(C1)-- Token (Optional) --->| |
| | | |
| |---(C2)-- Protected Request -->| Resource |
| | | Server |
| |<--(F)--- Protected Resource --| |
| | | |
+--------+ +----------------------------+
Figure 2: ACE Short Distribution Chain (SDC) Workflow.
More specifically, the SDC workflow consists of the following steps.
* Step A - Like in the original workflow, the client sends an access
token request to the token endpoint at the AS, with the additional
indication that it opts in to use the SDC workflow.
As defined in Section 3.1, this indication is provided to the AS
by means of the "token_upload" parameter included in the access
token request. The parameter also specifies what the AS has to
return in the access token response at Step B, following a
successful uploading of the access token from the AS to the RS.
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* Step A1 - This new step consists of the AS uploading the access
token to the RS, typically at the authz-info endpoint, just like
the client does in the original workflow.
* Step A2 - This new step consists of the RS replying to the AS,
following the uploading of the access token at Step A1.
* Step B - In the access token response, the AS informs the client
that it has attempted to upload the access token to the RS,
specifying the outcome of the token uploading based on the reply
received from the RS at Step A2.
As defined in Section 3.1, this information is provided to the
client by means of the "token_upload" parameter included in the
access token response. If the token uploading has failed, the
access token response also includes the access token. Otherwise,
the access token response includes information consistent with
what was specified by the "token_upload" parameter of the access
token request at Step A.
* Step C1 - This step occurs only if the token uploading from the AS
has failed, and the AS has provided the client with the access
token at Step B. In such a case, the client uploads the access
token to the RS just like at Step C of the original workflow.
* Step C2 - The client attempts to access a protected resource at
the RS, according to the permissions granted per the access token
and specified by the AS as access information at Step B.
* Steps D, E, and F are like in the original workflow.
The SDC workflow has no ambition to replace the original workflow
defined in [RFC9200]. The AS can use one workflow or the other,
depending, for example, on the specific RS for which the access token
has been issued and the nature of the communication leg with that RS.
When using the SDC workflow, all the communications between the AS
and the RS MUST be protected, consistent with Sections 5.8.4.3 and
6.5 of [RFC9200]. Unlike in the original workflow, this results in
protecting also the uploading of the first access token in a token
series, i.e., in addition to the uploading of the following access
tokens in the token series for dynamically updating the access rights
of the client.
The SDC workflow is also suitable for deployments where clients are
not aware of details such as the need for access tokens to be issued
by the AS and uploaded at the RS. Consistent with the intended
access policies, the AS can be configured to automatically issue
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access tokens for such clients and upload those access tokens to the
RS. This means that such clients do not have to request for an
access token to be issued in the first place. That is, they can
immediately send requests to the RS for accessing its protected
resources, in accordance with the access tokens already issued and
uploaded by the AS.
2.1. Token Upload
When using the original workflow defined in [RFC9200], there are two
typical cases concerning the upload of the access token to the RS
from C.
* The first case consists in the upload of the first access token in
a token series. While details depend on the specific profile of
ACE used, such an access token is typically uploaded through an
unprotected POST request to the authz-info endpoint.
* The second case consists in the upload of an access token that is
not the first in its token series, i.e., the AS has issued the
access token for dynamically updating the access rights of C.
The intent is also for C and the RS to preserve the same secure
communication association that they currently share and that is
associated with the token series in question.
Such an access token is uploaded through a POST request to the
authz-info endpoint, which is protected by means of the secure
communication association that is shared between C and the RS. If
the new access token is accepted by the RS, the new access token
supersedes the one currently stored for the token series in
question, and it becomes associated with the corresponding secure
communication association that is shared between C and the RS.
However, if the AS uploads the access token to the RS on behalf of C
as per the SDC workflow, the upload of the access token always rely
on a protected POST request from the AS to the authz-info endpoint.
In particular, the request is protected with the secure communication
association shared between the AS and the RS.
When receiving a POST request to the authz-info endpoint that is
specifically protected through the secure communication association
shared with the AS, the RS proceeds as follows. In particular, the
RS leverages the explicit indication provided by the AS through the
"updated_rights" parameter defined in Section 3.7, which is included
in the request in the case of dynamic update of access rights.
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* If the POST request does not include the "updated_rights"
parameter, the access token in question is the first one in a
token series. Consequently, the RS processes the request and the
access token therein like it would when receiving the request from
C and according to the specific profile of ACE used.
* If the POST request includes the "updated_rights" parameter
encoding a specific value, the access token in question is not the
first one in a token series, i.e., it is meant to dynamically
update the access rights of C, while preserving the same secure
communication association that is shared between C and the RS.
The processing of the POST request at the RS in this case is
defined in Section 3.7.
3. New Parameters
The rest of this section defines a number of additional parameters
and encodings for the OAuth 2.0 token endpoint at the AS (see
Section 5.8 of [RFC9200]) and for the OAuth 2.0 authz-info endpoint
at the RS (see Section 5.10.1 of [RFC9200]).
3.1. token_upload
This section defines the additional "token_upload" parameter. The
parameter can be used in an access token request sent by C to the
token endpoint at the AS (see Section 5.8.1 of [RFC9200]), as well as
in the access token response sent as a reply by the AS (see
Section 5.8.2 of [RFC9200]).
* The "token_upload" parameter is OPTIONAL to include in an access
token request. The presence of this parameter indicates that C
opts in to use the SDC workflow defined in Section 2, whose actual
use for uploading the issued access token to the RS is an
exclusive prerogative of the AS.
This parameter can take one of the following integer values. When
the access token request is encoded in CBOR, those values are
encoded as CBOR unsigned integers. The value of the parameter
determines whether the follow-up access token response will have
to include certain information, in case the AS has successfully
uploaded the access token to the RS.
- 0: The access token response will have to include neither the
access token nor its corresponding token hash.
- 1: The access token response will have to include the token
hash corresponding to the access token, but not the access
token.
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- 2: The access token response will have to include the access
token, but not the corresponding token hash.
If the AS supports the SDC workflow and the access token request
includes the "token_upload" parameter with value 0, 1, or 2, then
the AS MAY use the SDC workflow to upload the access token to the
RS on behalf of C. Otherwise, following that access token
request, the AS MUST NOT use the SDC workflow.
* The "token_upload" parameter MUST be included in an access token
response, if both the following conditions apply. Otherwise, the
"token_upload" parameter MUST NOT be included.
- The corresponding access token request included the
"token_upload" parameter, with value 0, 1, or 2.
- The AS has attempted to upload the issued access token to the
RS as per the SDC workflow, irrespective of the result of the
token upload.
When the "token_upload" parameter is included in the access token
response, it can take one of the following integer values. When
the access token response is encoded in CBOR, those values are
encoded as CBOR unsigned integers.
- If the token upload to the RS was not successful, then the
"token_upload" parameter MUST encode the value 1.
In this case, the access token response MUST include the
"access_token" parameter specifying the issued access token.
- If the token upload at the RS was successful, then the
"token_upload" parameter MUST encode the value 0.
In this case, the access token response can include additional
parameters as defined below, depending on the value of the
"token_upload" parameter in the corresponding access token
request.
o If the "token_upload" parameter in the access token request
specified the value 0, then the access token response MUST
NOT include the "access_token" parameter and MUST NOT
include the "token_hash" parameter defined in Section 3.2.
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o If the "token_upload" parameter in the access token request
specified the value 1, then the access token response MUST
NOT include the "access_token" parameter and MUST include
the "token_hash" parameter defined in Section 3.2,
specifying the hash corresponding to the issued access token
and computed as defined in Section 3.2.
o If the "token_upload" parameter in the access token request
specified the value 2, then the access token response MUST
include the "access_token" parameter specifying the issued
access token and MUST NOT include the "token_hash" parameter
defined in Section 3.2.
3.1.1. Examples
Figure 3 shows an example, with first an access token request from C
to the AS and then an access token response from the AS to C,
following the issue of an access token bound to a symmetric PoP key.
The access token request specifies the "token_upload" parameter with
value 0. That is, C indicates that it requires neither the access
token nor the corresponding token hash from the AS, in case the AS
successfully uploads the access token to the RS.
The access token response specifies the "token_upload" parameter with
value 0, which indicates that the AS has successfully uploaded the
access token to the RS on behalf of C.
Consistent with the value of the "token_upload" parameter in the
access token request, the access token response includes neither the
access token nor its corresponding token hash. The access token
response also includes the "cnf" parameter specifying the symmetric
PoP key bound to the access token.
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Access token request
Header: POST (Code=0.02)
Uri-Host: "as.example.com"
Uri-Path: "token"
Content-Format: 19 (application/ace+cbor)
Payload:
{
/ audience / 5 : "tempSensor4711",
/ scope / 9 : "read",
e'token_upload' : 0
}
Access token response
Header: Created (Code=2.01)
Content-Format: 19 (application/ace+cbor)
Max-Age: 3560
Payload:
{
e'token_upload' : 0,
/ expires_in / 2 : 3600,
/ cnf / 8 : {
/ COSE_Key / 1 : {
/ kty / 1 : 4 / Symmetric /,
/ kid / 2 : h'3d027833fc6267ce',
/ k / -1 : h'73657373696f6e6b6579'
}
}
}
Figure 3: Example of Access Token Request-Response Exchange.
Following a successful uploading of the access token from the AS
to the RS, the access token response includes the "token_upload"
parameter but not the access token, which is bound to a symmetric
key and was uploaded to the RS by the AS.
Figure 4 shows another example, with first an access token request
from C to the AS and then an access token response from the AS to C,
also following the issue of an access token bound to a symmetric PoP
key.
The access token request specifies the "token_upload" parameter with
value 2. That is, C indicates that it requires the access token from
the AS, even in case the AS successfully uploads the access token to
the RS.
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The access token response specifies the "token_upload" parameter with
value 0, which indicates that the AS has successfully uploaded the
access token to the RS on behalf of C.
Consistent with the value of the "token_upload" parameter in the
access token request, the access token response includes the
"access_token" parameter specifying the issued access token. The
access token response also includes the "cnf" parameter specifying
the symmetric PoP key bound to the access token.
Access token request
Header: POST (Code=0.02)
Uri-Host: "as.example.com"
Uri-Path: "token"
Content-Format: 19 (application/ace+cbor)
Payload:
{
/ audience / 5 : "tempSensor4711",
/ scope / 9 : "read",
e'token_upload' : 2
}
Access token response
Header: Created (Code=2.01)
Content-Format: 19 (application/ace+cbor)
Max-Age: 3560
Payload:
{
e'token_upload' : 0,
/ access_token / 1 : h'd08343a1...4819',
/ (full CWT elided for brevity;
CWT contains the symmetric PoP key in the "cnf" claim) /
/ expires_in / 2 : 3600,
/ cnf / 8 : {
/ COSE_Key / 1 : {
/ kty / 1 : 4 / Symmetric /,
/ kid / 2 : h'3d027833fc6267ce',
/ k / -1 : h'73657373696f6e6b6579'
}
}
}
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Figure 4: Example of Access Token Request-Response Exchange.
Following a successful uploading of the access token from the AS
to the RS, the access token response includes the "token_upload"
parameter as well as the "access_token" parameter conveying the
access token, which is bound to a symmetric key and was uploaded
to the RS by the AS.
Figure 5 shows another example, with first an access token request
from C to the AS and then an access token response from the AS to C,
also following the issue of an access token bound to a symmetric PoP
key.
The access token request specifies the "token_upload" parameter with
value 0. That is, C indicates that it requires neither the access
token nor the corresponding token hash from the AS, in case the AS
successfully uploads the access token to the RS.
In this example, the access token response includes the
"token_upload" parameter with value 1, which indicates that the AS
has attempted and failed to upload the access token to the RS on
behalf of C. The access token response also includes the
"access_token" parameter specifying the issued access token, together
with the "cnf" parameter specifying the symmetric PoP key bound to
the access token.
Note that, even though the AS has failed to upload the access token
to the RS, the response code 2.01 (Created) is used when replying to
C, since the access token request as such has been successfully
processed at the AS, with the following issue of the access token.
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Access token request
Header: POST (Code=0.02)
Uri-Host: "as.example.com"
Uri-Path: "token"
Content-Format: 19 (application/ace+cbor)
Payload:
{
/ audience / 5 : "tempSensor4711",
/ scope / 9 : "read",
e'token_upload' : 0
}
Access token response
Header: Created (Code=2.01)
Content-Format: 19 (application/ace+cbor)
Max-Age: 3560
Payload:
{
e'token_upload' : 1,
/ access_token / 1 : h'd08343a1...4819',
/ (full CWT elided for brevity;
CWT contains the symmetric PoP key in the "cnf" claim) /
/ expires_in / 2 : 3600,
/ cnf / 8 : {
/ COSE_Key / 1 : {
/ kty / 1 : 4 / Symmetric /,
/ kid / 2 : h'3d027833fc6267ce',
/ k / -1 : h'73657373696f6e6b6579'
}
}
}
Figure 5: Example of Access Token Request-Response Exchange.
Following a failed uploading of the access token from the AS to
the RS, the access token response includes the "token_upload"
parameter with value 1 as well the "access_token" parameter
conveying the access token bound to a symmetric key.
3.2. token_hash
This section defines the additional "token_hash" parameter. The
parameter can be used in an access token response sent by the AS (see
Section 5.8.2 of [RFC9200]), in reply to an access token request sent
to the token endpoint by C.
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The following refers to the base64url encoding without padding (see
Section 5 of [RFC4648]) and denotes as "binary representation" of a
text string the corresponding UTF-8 encoding [RFC3629], which is the
implied charset used in JSON (see Section 8.1 of [RFC8259]).
The "token_hash" parameter MUST be included in an access token
response, if both the following conditions apply. Otherwise, it MUST
NOT be included.
* The corresponding access token request included the "token_upload"
parameter with value 1 (see Section 3.1).
* The access token response includes the "token_upload" parameter
with value 0. That is, the AS has successfully uploaded the
issued access token to the RS, as per the SDC workflow.
This parameter specifies the token hash corresponding to the access
token issued by the AS and successfully uploaded to the RS on behalf
of C. In particular:
* If the access token response is encoded in CBOR, then the
"token_hash" parameter is a CBOR byte string, with value the token
hash.
* If the access token response is encoded in JSON, then the
"token_hash" parameter has as value the base64url-encoded text
string that encodes the token hash.
The AS computes the token hash as defined in Section 3.2.1.
3.2.1. Computing the Token Hash
The AS computes the token hash over the value that the "access_token"
parameter would have had in the same access token response, if it was
included therein and specifying the access token.
In particular, the input HASH_INPUT over which the token hash is
computed is determined as follows.
* If the access token response is encoded in CBOR, then:
- BYTES denotes the value of the CBOR byte string that would be
conveyed by the "access_token" parameter, if this was included
in the access token response.
- HASH_INPUT_TEXT is the base64url-encoded text string that
encodes BYTES.
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- HASH_INPUT is the binary representation of HASH_INPUT_TEXT.
* If the access token response is encoded in JSON, then HASH_INPUT
is the binary representation of the text string conveyed by the
"access_token" parameter, if this was included in the access token
response.
Once determined HASH_INPUT as defined above, a hash value of
HASH_INPUT is generated as per Section 6 of [RFC6920]. The resulting
output in binary format is used as the token hash. Note that the
used binary format embeds the identifier of the used hash function in
the first byte of the computed token hash.
The specific hash function used MUST be collision resistant on byte
strings and MUST be selected from the "Named Information Hash
Algorithm Registry" [IANA.Hash.Algorithms]. Consistent with the
compliance requirements in Section 2 of [RFC6920], the hash function
sha-256 as specified in [SHA-256] is mandatory to implement.
The computation of token hashes defined above is aligned with that
specified for the computation of token hashes in Section 4 of
[RFC9770], where they are used as identifiers of revoked access
tokens. Therefore, given a hash algorithm and an access token, the
AS computes the same corresponding token hash in either case.
If the AS supports the method specified in [RFC9770], then the AS
MUST use the same hash algorithm for computing both the token hashes
to include in the "token_hash" parameter and the token hashes
computed per that method to identify revoked access tokens.
3.2.2. Example
Figure 6 shows an example, with first an access token request from C
to the AS and then an access token response from the AS to C,
following the issue of an access token bound to a symmetric PoP key.
The access token request specifies the "token_upload" parameter with
value 1. That is, C indicates that it requires the token hash
corresponding to the access token from the AS, in case the AS
successfully uploads the access token to the RS.
The access token response specifies the "token_upload" parameter with
value 0, which indicates that the AS has successfully uploaded the
access token to the RS on behalf of C.
Consistent with the value of the "token_upload" parameter in the
access token request, the access token response includes the
"token_hash" parameter, which specifies the token hash corresponding
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to the issued access token. The access token response also includes
the "cnf" parameter specifying the symmetric PoP key bound to the
access token.
Access token request
Header: POST (Code=0.02)
Uri-Host: "as.example.com"
Uri-Path: "token"
Content-Format: 19 (application/ace+cbor)
Payload:
{
/ audience / 5 : "tempSensor4711",
/ scope / 9 : "read",
e'token_upload' : 1
}
Access token response
Header: Created (Code=2.01)
Content-Format: 19 (application/ace+cbor)
Max-Age: 3560
Payload:
{
e'token_upload' : 0,
e'token_hash' : h'0153269057e12fe2b74ba07c892560a2d7
53877eb62ff44d5a19002530ed97ffe4',
/ expires_in / 2 : 3600,
/ cnf / 8 : {
/ COSE_Key / 1 : {
/ kty / 1 : 4 / Symmetric /,
/ kid / 2 : h'3d027833fc6267ce',
/ k / -1 : h'73657373696f6e6b6579'
}
}
}
Figure 6: Example of Access Token Request-Response Exchange.
Following a successful uploading of the access token from the AS
to the RS, the access token response includes the "token_upload"
parameter as well as the "token_hash" parameter. The
"token_hash" parameter conveys the token hash corresponding to
the issued access token, which is bound to a symmetric key and
was uploaded to the RS by the AS.
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3.3. to_rs and from_rs
The rest of this section defines the additional parameters "to_rs"
(see Section 3.3.1) and "from_rs" (see Section 3.3.2).
The "to_rs" parameter can be used in an access token request sent by
C to the token endpoint at the AS (see Section 5.8.1 of [RFC9200]).
The "from_rs" parameter can be used in an access token response sent
by the AS (see Section 5.8.2 of [RFC9200]), in reply to an access
token request sent to the token endpoint by C.
The semantics and encoding of the information specified in the two
parameters depend on the specific profile of ACE and application
used.
For instance, when using the OSCORE profile [RFC9203], C and RS can
use the two parameters to exchange the expected nonces and
identifiers via the AS. Section 3.3.3 describes how the two
parameters are used when the OSCORE profile is used, thereby
effectively enabling the use of the SDC workflow for that profile.
3.3.1. to_rs
The "to_rs" parameter is OPTIONAL to include in an access token
request. The presence of this parameter indicates that:
* C wishes the AS to relay the information specified therein to the
RS, when the AS uploads the issued access token to the RS per the
SDC workflow defined in Section 2; and
* C wishes the AS to relay information received from the RS to C,
after having successfully uploaded the access token to the RS per
the SDC workflow defined in Section 2.
The "to_rs" parameter MUST NOT be included if the "token_upload"
parameter defined in Section 3.1 is not included in the access token
request. Also, this parameter MUST NOT be included if the requested
access token is not the first one of a new token series, i.e., if C
is asking the AS for a new access token in the same token series that
dynamically updates access rights.
If C wishes that the AS relays information from the RS after
successfully uploading the access token, but C does not have any
information to be relayed to the RS, then the following applies:
* When the access token request is encoded in CBOR, then the "to_rs"
parameter MUST encode the CBOR simple value null (0xf6).
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* When the access token request is encoded in JSON, then the "to_rs"
parameter MUST have value null.
Otherwise, this parameter specifies the information that C wishes the
AS to relay to the RS, when uploading the access token to the RS on
behalf of C.
Such information consists in what C would provide to the RS in
addition to the access token, if the original workflow was used and a
POST request encoded in CBOR was sent to the authz-info endpoint at
the RS.
When composing the parameter "to_rs", C considers the same
information and MUST wrap it in a data structure STRUCT, by using the
same method that it employs when using the original workflow. For
example, with reference to the OSCORE profile of ACE [RFC9203], such
a method composes STRUCT as a CBOR map, which has to be sent as
payload of a request with Content-Format "application/ace+cbor".
After that, C builds a CBOR byte string STR, whose value is the
binary representation of STRUCT.
If and only if the request to the authz-info endpoint has to be sent
with a Content-Format ct different from the one employed in the
profile of ACE used, then C MUST tag the CBOR byte string STR (see
Section 3.4 of [RFC8949]). The tag number TN MUST be the one
associated with the Content-Format ct and is determined according to
the technique described in Appendix B of [RFC9277]. For example, the
Content-Format "application/ace+cbor" has Content-Format ID 19 and
therefore has 1668546836 as its associated tag number.
When the access token request is encoded in CBOR, the value of the
"to_rs" parameter is the (tagged) CBOR byte string STR.
When the access token request is encoded in JSON, the value of the
"to_rs" parameter is a text string, which encodes the binary
representation of the (tagged) CBOR byte string STR in base64url
without padding (see Section 5 of [RFC4648]).
If the "to_rs" parameter is included, and it specifies a value
different from the CBOR simple value null (0xf6) when the access
token request is encoded in CBOR or from null when the access token
request is encoded in JSON, then the AS proceeds as follows when
composing the POST request to send to the authz-info endpoint on
behalf of C:
1. The AS sets the Content-Format of the request to be either:
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* the one employed in the profile of ACE used, if the CBOR byte
string STR conveyed by the "to_rs" parameter is not tagged;
or, otherwise,
* the one associated with the tag number TN of the tagged CBOR
byte string STR conveyed by the "to_rs" parameter.
2. The AS retrieves the structure STRUCT from STR and extends STRUCT
by adding the issued access token, consistently with the profile
of ACE used and the Content-Format determined at the previous
step.
For example, when using the OSCORE profile of ACE [RFC9203] and
thus the Content-Format to use is "application/ace+cbor", STRUCT
is a CBOR map and the access token is included therein as an
entry that has: as map key, 1 encoded as a CBOR integer; as map
value, a CBOR byte string whose value is the binary
representation of the access token.
Clearly, performing the two steps above requires the AS to understand
the structure STRUCT and its semantics. In turn, such an
understanding builds on the AS supporting the profile of ACE used and
the Content-Format to use as determined at Step 1. In the expected
cases, the AS is realistically able to perform the two steps. If the
AS finds itself unable to perform the two steps, then the AS would
simply not upload the access token to the RS on behalf of C. In such
a case, the AS replies to C with an access token response, which
includes the "access_token" parameter specifying the issued access
token and does not include the "token_upload" parameter (see
Section 3.1).
Tagging the CBOR byte string as defined above ensures that the AS can
relay the information specified in the "to_rs" parameter as intended
by C, i.e., by sending to the authz-info endpoint a POST request that
has the correct Content-Format and conveys the correct payload.
As a case in point, using the DTLS profile of ACE [RFC9202] typically
results in a POST request to the authz-info endpoint with Content-
Format "application/cwt", as per Section 5.10 of [RFC9200]. However,
the DTLS profile of ACE can be combined with application profiles of
[RFC9594]. In such a case, the POST request might convey both the
access token and additional parameters from C (e.g., "sign_info"
defined in Section 3.3 of [RFC9594]), which requires the request to
have Content-Format "application/ace+cbor" (see Section 3.3 of
[RFC9594]).
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3.3.2. from_rs
The "from_rs" parameter is OPTIONAL to include in an access token
response. The presence of this parameter indicates that the AS is
relaying the information specified therein to C, which the AS has
received from the RS after having successfully uploaded the access
token to the RS per the SDC workflow defined in Section 2.
The "from_rs" parameter MUST be included in an access token response
if both the following conditions apply. Otherwise, it MUST NOT be
included.
* The corresponding access token request included the "to_rs"
parameter (see Section 3.3.1).
* The access token response includes the "token_upload" parameter
with value 0 (see Section 3.1). That is, the AS has successfully
uploaded the issued access token to the RS, as per the SDC
workflow.
This parameter specifies the information that the AS is relaying to C
from the RS, following the successful upload of the access token to
the RS on behalf of C.
Such information consists in what C would receive from the RS, if the
original workflow was used and the RS sent a successful response
encoded in CBOR, in reply to a POST request to the authz-info
endpoint.
When composing the parameter "from_rs", the AS builds a CBOR byte
string STR as follows:
* If the successful response from the authz-info endpoint does not
include a payload, then STR is the empty CBOR byte string (0x40);
otherwise,
* The value of STR is the payload of the successful response from
the authz-info endpoint.
If and only if the response specifies a given Content-Format ct
(i.e., by means of the CoAP Content-Format Option), then the AS
MUST tag the CBOR byte string STR (see Section 3.4 of [RFC8949]).
The tag number TN MUST be the one associated with the Content-
Format ct and is determined according to the technique described
in Appendix B of [RFC9277].
When the access token response is encoded in CBOR, the value of the
"from_rs" parameter is the (tagged) CBOR byte string STR.
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When the access token response is encoded in JSON, the value of the
"from_rs" parameter is a text string, which encodes the binary
representation of the (tagged) CBOR byte string STR in base64url
without padding (see Section 5 of [RFC4648]).
When C receives from the AS the access token response specifying the
"token_upload" parameter with value 0, C retrieves from the "from_rs"
parameter the information relayed by the AS, just like when
retrieving that information from a successful response with Content-
Format ct that C receives from the RS when using the original
workflow.
In particular, if the CBOR byte string STR is not the empty CBOR byte
string (0x40), C considers as the Content-Format ct either:
* the one employed in the profile of ACE used, if the CBOR byte
string STR conveyed by the "from_rs" parameter is not tagged; or,
otherwise,
* the one associated with the tag number TN of the tagged CBOR byte
string STR conveyed by the "from_rs" parameter.
3.3.3. Use with the OSCORE Profile
This section describes how to use the parameters "to_rs" and
"from_rs" when the OSCORE profile of ACE [RFC9203] is used.
Within the access token request from C to the AS, the value of the
"to_rs" parameter is a CBOR byte string, whose value is the binary
representation of a CBOR map C_MAP composed of two fields:
* A field with the CBOR integer 40 as map key and with value the
nonce N1 generated by C, encoded a CBOR byte string (see
Section 4.1 of [RFC9203]).
* A field with the CBOR integer 43 as map key and with value the
Recipient ID ID1 generated by C, encoded as a CBOR byte string
(see Section 4.1 of [RFC9203]).
When building the POST request for uploading the access token to the
authz-info endpoint at the RS, the AS sets the Content-Format of the
request to "application/ace+cbor" and composes the request payload as
specified in Section 4.1 of [RFC9203]. In particular, the CBOR map
specified as payload includes:
* The "access_token" field, with value the access token to upload
encoded as a CBOR byte string and with the CBOR integer 1 as map
key.
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* The "nonce1" field, with value the same CBOR byte string specified
by the field of C_MAP that has the CBOR integer 40 as map key.
* The "ace_client_recipientid" field, with value the same CBOR byte
string specified by the field of C_MAP that has the CBOR integer
43 as map key.
If the upload of the access token to the RS from the AS is
successful, the RS replies to the AS with a 2.01 (Created) response,
which has Content-Format "application/ace+cbor" and whose payload is
a CBOR map RS_MAP that includes:
* The "nonce2" field, with value the nonce N2 generated by the RS,
encoded as a CBOR byte string (see Section 4.2 of [RFC9203]).
* The "ace_server_recipientid" field, with value the Recipient ID
ID2 generated by the RS, encoded as a CBOR byte string (see
Section 4.2 of [RFC9203]).
Within the access token response from the AS to C, the value of the
"from_rs" parameter is a CBOR byte string, whose value is the binary
representation of a CBOR map composed of two elements:
* A field with the CBOR integer 42 as map key and with value the
same CBOR byte string specified by the "nonce2" field of RS_MAP.
* A field with the CBOR integer 44 as map key and with value the
same CBOR byte string specified by the "ace_server_recipientid"
field of RS_MAP.
When C receives from the AS the access token response specifying the
"token_upload" parameter with value 0, C retrieves the nonce N2 and
the Recipient ID ID2 from the "from_rs" parameter, just like when
retrieving those from a 2.01 (Created) response received from the RS
when using the original workflow.
Figure 7 shows an example where the OSCORE profile is used, with
first an access token request from C to the AS and then an access
token response from the AS to C, following the issue of an access
token bound to a symmetric PoP key.
The access token request specifies the "token_upload" parameter with
value 0. That is, C indicates that it requires neither the access
token nor the corresponding token hash from the AS, in case the AS
successfully uploads the access token to the RS. Also, the access
token request includes the "to_rs" parameter, specifying the values
of N1 = 0x018a278f7faab55a and ID1 = 0x1645 intended to the RS.
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The access token response specifies the "token_upload" parameter with
value 0, which indicates that the AS has successfully uploaded the
access token to the RS on behalf of C.
Consistent with the value of the "token_upload" parameter in the
access token request, the access token response includes neither the
access token nor its corresponding token hash. The access token
response also includes the "cnf" parameter specifying the symmetric
PoP key bound to the access token, as an OSCORE_Input_Material object
(see Section 3.2.1 of [RFC9203]). Also, the access token response
includes the "from_rs" parameter, specifying the values of N2 =
0x25a8991cd700ac01 and ID2 = 0x0000 received from the RS and intended
to C.
Access token request
Header: POST (Code=0.02)
Uri-Host: "as.example.com"
Uri-Path: "token"
Content-Format: 19 (application/ace+cbor)
Payload:
{
/ audience / 5 : "tempSensor4711",
/ scope / 9 : "read",
e'token_upload' : 0,
e'to_rs' : h'a2182848018a278f7faab55a182b421645'
}
Access token response
Header: Created (Code=2.01)
Content-Format: 19 (application/ace+cbor)
Max-Age: 3560
Payload:
{
e'token_upload' : 0,
e'from_rs' : h'a2182a4825a8991cd700ac01182c420000',
/ ace_profile / 38 : 2 / coap_oscore /,
/ expires_in / 2 : 3600,
/ cnf / 8 : {
/ osc / 4 : {
/ id / 0 : h'01',
/ ms / 2 : h'f9af838368e353e78888e1426bd94e6f'
}
}
}
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Figure 7: Example of Access Token Request-Response Exchange where
the OSCORE Profile is Used. Following a successful uploading of
the access token from the AS to the RS, the access token response
includes the "token_upload" parameter but not the access token,
which is bound to a symmetric key and was uploaded to the RS by
the AS. C and the RS exchange N1, ID1, N2, and ID2 via the AS by
means of the parameters "to_rs" and "from_rs".
3.4. rs_cnf2 and audience2
This section defines the additional parameters "rs_cnf2" and
"audience2". The two parameters can be used in an access token
response sent by the AS (see Section 5.8.2 of [RFC9200]), in reply to
an access token request sent to the token endpoint by C.
* The "rs_cnf2" parameter is OPTIONAL to include in an access token
response, if the token type is "pop", asymmetric keys are used,
and the access token is issued for an audience that includes
multiple RSs (i.e., a group-audience, see Section 6.9 of
[RFC9200]). Otherwise, the "rs_cnf2" parameter MUST NOT be
included.
Also, the "rs_cnf2" parameter MUST NOT be included if the issued
access token is not the first one of a new token series.
This parameter specifies information about the public keys used by
the RSs of the group-audience for authenticating themselves to C.
It is used in case the binding between the public keys and the
corresponding RS identities are not established through other
means. If this parameter is absent, either the RSs in the group-
audience do not use a public key, or the AS knows that the RSs can
authenticate themselves to C without additional information.
If included, this parameter MUST encode a non-empty array of N
elements, where N is the number of RSs in the group-audience for
which the access token is issued. The array is encoded as a CBOR
array or a JSON array, depending on whether the access token
response is encoded in CBOR or JSON, respectively.
Each element of the array specifies the public key of an RS in the
group-audience, and MUST follow the syntax and semantics of the
"cnf" claim either from Section 3.1 of [RFC8747] for CBOR-based
interactions, or from Section 3.1 of [RFC7800] for JSON-based
interactions. It is not required that all the elements of the
array rely on the same confirmation method.
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Any of the public keys may be provided together with information
such as the public key algorithm and use (e.g., specified by means
of the parameters "alg" and "key_ops" in a COSE_Key structure).
If such information is specified, a client MUST NOT use a public
key that is incompatible with the profile of ACE used or with the
PoP algorithm according to that information. An RS MUST reject a
proof of possession that relies on such a key and MUST reply with
a response code equivalent to the CoAP code 4.00 (Bad Request).
* The "audience2" parameter is OPTIONAL to include in an access
token response, and it specifies the identifiers of the RSs in the
group-audience for which the access token is issued.
The "audience2" parameter MUST NOT be included if the issued
access token is not the first one of a new token series.
If included, this parameter MUST encode a non-empty array of N
elements, where N is the number of RSs in the group-audience for
which the access token is issued. The array is encoded as a CBOR
array or a JSON array, depending on whether the access token
response is encoded in CBOR or JSON, respectively.
Each element of the array in the "audience2" parameter specifies
the identifier of an RS in the group-audience. The value of each
element of the array is encoded as a CBOR text string or a JSON
string, depending on whether the access token response is encoded
in CBOR or JSON, respectively.
The element of the array referring to an RS in the group-audience
SHOULD have the same value that would be used to identify that RS
through the "audience" parameter of an access token request to the
AS (see Section 5.8.1 of [RFC9200]) and of an access token
response from the AS (see Section 5.8.2 of [RFC9200]), when
requesting and issuing an access token for that individual RS.
The "audience2" parameter MUST be included if the "rs_cnf2"
parameter is included. In such a case, the i-th element of the
array in the "audience2" parameter MUST be the identifier of the
RS whose public key is specified by the i-th element of the array
in the "rs_cnf2" parameter.
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3.4.1. Example
Figure 8 shows an example of access token response from the AS to C,
following the issue of an access token for a group-audience composed
of two RSs, namely "rs1" and "rs2", and bound to C's public key as an
asymmetric PoP key. The access token response includes the access
token as well as the parameters "audience2" and "rs_cnf2". These
parameters specify the public key of the two RSs as the intended
recipients of the access token and the identifiers of those two RSs,
respectively.
Access token response
Header: Created (Code=2.01)
Content-Format: 19 (application/ace+cbor)
Max-Age: 3600
Payload:
{
/ access_token / 1 : b64'SlAV32hk...12',
/ (full CWT elided for brevity;
CWT contains the client's RPK in the "cnf" claim) /
/ expires_in / 2 : 3600,
e'audience2' : ["rs1", "rs2"],
e'rs_cnf2' : [
{
/ COSE_Key / 1 : {
/ kty / 1 : 2 / EC2 /,
/ crv / -1 : 1 / P-256 /,
/ x / -2 : h'bbc34960526ea4d32e940cad2a234148
ddc21791a12afbcbac93622046dd44f0',
/ y / -3 : h'4519e257236b2a0ce2023f0931f1f386
ca7afda64fcde0108c224c51eabf6072'
}
},
{
/ COSE_Key / 1 : {
/ kty / 1 : 2 / EC2 /,
/ crv / -1 : 1 / P-256 /,
/ x / -2 : h'ac75e9ece3e50bfc8ed6039988952240
5c47bf16df96660a41298cb4307f7eb6',
/ y / -3 : h'6e5de611388a4b8a8211334ac7d37ecb
52a387d257e6db3c2a93df21ff3affc8'
}
}
]
}
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Figure 8: Example of access token response with an access token
bound to an asymmetric key, using the parameters "audience2" and
"rs_cnf2".
3.5. anchor_cnf
This section defines the additional "anchor_cnf" parameter. The
parameter can be used in an access token response sent by the AS (see
Section 5.8.2 of [RFC9200]), in reply to an access token request sent
to the token endpoint by C.
The "anchor_cnf" parameter is OPTIONAL to include in an access token
response, if the token type is "pop" and asymmetric keys are used.
Otherwise, the "anchor_cnf" parameter MUST NOT be included.
Also, the "anchor_cnf" parameter MUST NOT be included if the issued
access token is not the first one of a new token series.
This parameter specifies information about the public keys of trust
anchors, which C can use to validate the public key of the RS/RSs
included in the audience for which the access token is issued. This
parameter can be used when the access token is issued for an audience
including one RS or multiple RSs.
If this parameter is absent, either the RS/RSs in the audience do not
use a public key, or the AS knows that C can validate the public key
of such RS/RSs without additional information (e.g., C has already
obtained the required public keys of the involved trust anchors from
the AS or through other means).
If included, this parameter MUST encode a non-empty array that MUST
be treated as a set, i.e., the order of its elements has no meaning.
Each element of the array specifies the public key of one trust
anchor, which can be used to validate the public key of at least one
RS included in the audience for which the access token is issued.
The array is encoded as a CBOR array or a JSON array, depending on
whether the access token response is encoded in CBOR or JSON,
respectively.
Each element of the array MUST follow the syntax and semantics of the
"cnf" claim either from Section 3.1 of [RFC8747] for CBOR-based
interactions, or from Section 3.1 of [RFC7800] for JSON-based
interactions. It is not required that all the elements of the array
rely on the same confirmation method.
Any of the public keys conveyed in the "anchor_cnf" parameter may be
provided together with information such as the public key algorithm
and use (e.g., specified by means of the parameters "alg" and
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"key_ops" in a COSE_Key structure). If such information is
specified, a client MUST NOT use a public key that is incompatible
with the profile of ACE used or with the public keys to validate and
the way to validate those.
The presence of this parameter does not require that the access token
response also includes the "rs_cnf" parameter defined in [RFC9201] or
the "rs_cnf2" parameter defined in Section 3.4 of the present
document. That is, C may be able to obtain the public keys of the
RS/RSs for which the access token is issued through other means.
When the access token response includes both the "anchor_cnf"
parameter and the "audience2" parameter defined in Section 3.4, then
C MUST make sure that a public key PK_RS is associated with an RS
identified by an element of "audience2", before using any of the
public keys specified in "anchor_cnf" to validate PK_RS.
When the access token response includes the "anchor_cnf" parameter
but not the "audience2" parameter, then C can use any of the public
keys specified in "anchor_cnf" to validate the public key PK_RS of
any RS in the targeted audience. This allows C to use the access
token with an RS that is deployed later on as part of the same
audience, which is particularly useful in the case of a group-
audience.
3.5.1. Example
Figure 9 shows an example of access token response from the AS to C,
following the issue of an access token for a group-audience and bound
to C's public key as an asymmetric PoP key.
The identifier of the group-audience was specified by the "audience"
parameter of the access token request to the AS, is specified by the
"aud" claim of the issued access token, and is not repeated in the
access token response from the AS.
The access token response includes the "anchor_cnf" parameter. This
specifies the public key of a trust anchor that C can use to validate
the public keys of any RS with which the access token is going to be
used. By means of the CWT confirmation method "x5chain" defined in
[I-D.ietf-ace-edhoc-oscore-profile], the public key of the trust
anchor is here conveyed within an X.509 certificate [RFC5280] used as
the public authentication credential for that trust anchor.
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Access token response
Header: Created (Code=2.01)
Content-Format: 19 (application/ace+cbor)
Max-Age: 3600
Payload:
{
/ access_token / 1 : b64'SlAV32hk...12',
/ (full CWT elided for brevity;
CWT contains the client's RPK in the "cnf" claim) /
/ expires_in / 2 : 3600,
e'anchor_cnf' : [
{
e'x5chain' : h'308201363081dea003020102020301f50d30
0a06082a8648ce3d04030230163114301206
035504030c0b524643207465737420434130
1e170d3230303130313030303030305a170d
3231303230323030303030305a3022312030
1e06035504030c1730312d32332d34352d46
462d46452d36372d38392d41423059301306
072a8648ce3d020106082a8648ce3d030107
03420004b1216ab96e5b3b3340f5bdf02e69
3f16213a04525ed44450b1019c2dfd3838ab
ac4e14d86c0983ed5e9eef2448c6861cc406
547177e6026030d051f7792ac206a30f300d
300b0603551d0f040403020780300a06082a
8648ce3d04030203470030440220445d798c
90e7f500dc747a654cec6cfa6f037276e14e
52ed07fc16294c84660d02205a33985dfbd4
bfdd6d4acf3804c3d46ebf3b7fa62640674f
c0354fa056dbaea6'
}
]
}
Figure 9: Example of Access Token Response with an access token
bound to an asymmetric key, using the "anchor_cnf" parameter.
3.6. token_series_id
This section defines the additional "token_series_id" parameter. The
parameter can be used in an access token request sent by C to the
token endpoint at the AS (see Section 5.8.1 of [RFC9200]), as well as
in the access token response sent as a reply by the AS (see
Section 5.8.2 of [RFC9200]).
The following refers to the base64url encoding without padding (see
Section 5 of [RFC4648]).
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* The "token_series_id" parameter is OPTIONAL to include in an
access token request. The presence of this parameter indicates
that C wishes to obtain a new access token for dynamically
updating its access rights. That is, the new access token is
intended to be the next one in an active token series and to
supersede the latest access token in that token series.
The "token_series_id" parameter MUST NOT be included in an access
token request, if the requested access token is the first one of a
new token series.
If included, this parameter specifies the binary identifier of the
token series that the new access token is intended to extend. The
identifier does not change throughout the lifetime of the token
series and was provided to C in the access token response that the
AS sent when issuing the first access token in that token series.
When the access token request is encoded in CBOR, this parameter
is a CBOR byte string, with value the identifier of the token
series. When the access token request is encoded in JSON, this
parameter has as value the base64url-encoded text string that
encodes the identifier of the token series.
* The "token_series_id" parameter is OPTIONAL to include in an
access token response.
The "token_series_id" parameter MUST NOT be included in an access
token response, if the issued access token is not the first one of
a new token series.
If included, this parameter specifies the binary identifier of the
token series to which the issued access token belongs.
When the access token response is encoded in CBOR, this parameter
is a CBOR byte string, with value the identifier of the token
series. When the access token request is encoded in JSON, this
parameter has as value the base64url-encoded text string that
encodes the identifier of the token series.
If the AS relies on the "token_series_id" parameter to exchange the
identifier of token series with clients, then the following applies.
* The value assigned to the identifier of a token series MUST be
associated with all the access tokens issued by the AS for that
token series and MUST be selected from a pool that the AS
exclusively controls.
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In particular, the triple (TS_ID, C, AUD) MUST uniquely identify a
token series and its corresponding access tokens, where TS_ID is
the identifier of the token series, while C and AUD are the client
and the audience for which the access token is issued,
respectively. The AS MUST take into account both ongoing and
ended token series for selecting a new TS_ID that complies with
the above requirements.
Note that the ACE profile is not part of the triple, hence the
requirement spans across all the ACE profiles that the AS and its
registered clients/RSs support.
* An issued access token that belongs to a token series MUST include
the identifier of that token series. This allows the RS to
identify the latest access token in the token series to be
superseded by the issued access token.
In particular, each of such access tokens MUST include a claim
specifying the identifier of the token series to which the access
token belongs.
When CWTs are used as access tokens, this information MUST be
transported in the "token_series_id" claim registered in
Section 10.4, which has the same semantics as the
"token_series_id" parameter of an access token response encoded in
CBOR.
When JWTs are used as access tokens, this information MUST be
transported in the "token_series_id" claim registered in
Section 10.3, which has the same semantics as the
"token_series_id" parameter of an access token response encoded in
JSON.
If a profile of ACE relies on a construct that uses different
parameters/claims to transport the identifier of a token series, then
the new "token_series_id" parameter and "token_series_id" claim MUST
NOT be used when using that profile.
For example, a number of parameters/claims are already used to
transport information that acts as de facto identifier of token
series, in the PSK mode of the DTLS profile [RFC9202], in the OSCORE
profile [RFC9203], and in the EDHOC and OSCORE profile
[I-D.ietf-ace-edhoc-oscore-profile].
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3.7. updated_rights
This section defines the additional "updated_rights" parameter. The
parameter can be used in a POST request sent by the AS to the authz-
info endpoint at the RS (see Section 5.10.1 of [RFC9200]), when the
AS uploads an access token to the RS per the SDC workflow defined in
Section 2 of the present document. The "updated_rights" parameter
MUST NOT be included in the POST request to the authz-info endpoint
sent by C per the original workflow defined in [RFC9200].
The "updated_rights" parameter MUST be included in the POST request
sent by the AS to the authz-info endpoint at the RS, if the uploaded
access token is not the first one of a new token series, i.e., if the
AS has issued the access token for dynamically updating the access
rights of C. Otherwise, the "updated_rights" parameter MUST NOT be
included.
When including the "updated_rights" parameter, the following applies:
* If the POST request is encoded in CBOR, the request MUST have
media type "application/ace+cbor" and its payload MUST be
formatted as a CBOR map. In particular, the CBOR map MUST include
the "updated_rights" parameter encoding the CBOR simple value true
(0xf5), together with the "access_token" parameter specifying the
access token. The CBOR map MAY include additional parameters,
according to the specific profile of ACE used.
* If the POST request is encoded in JSON, the request MUST have
media type "application/ace+json" and its payload MUST be
formatted as a JSON object. In particular, the JSON object MUST
include the "updated_rights" parameter with value true, together
with the "access_token" parameter specifying the access token.
The JSON object MAY include additional parameters, according to
the specific profile of ACE used.
Note that this request deviates from the POST request defined in
[RFC9200], although such a deviation can already occur in some
profiles of ACE (e.g., see Section 4.1 of [RFC9203]) or in
application profiles of [RFC9594].
The rest of this section focuses on interactions with the authz-info
endpoint at the RS where messages are encoded in CBOR. The same as
described below holds in case such messages are encoded in JSON and
have media type "application/ace+json", with the difference that the
"updated_rights" parameter with value true can be present within a
JSON object conveyed by a POST request to the authz-info endpoint.
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When the RS receives a protected POST request to the authz-info
endpoint from the AS and the request does not convey the
"updated_rights" parameter, the RS is ensured that the access token
conveyed in the request is the first one of a new token series, and
processes it accordingly (see Section 2.1).
When the RS receives a protected POST request to the authz-info
endpoint from the AS and the request conveys the "updated_rights"
parameter encoding the CBOR simple value true (0xf5), the RS is
ensured that the access token conveyed in the request is not the
first one of a new token series.
Taking advantage of such explicit indication requires the RS to
support the Content-Format "application/ace+cbor" and the
"updated_rights" parameter.
If the RS does not support the Content-Format "application/ace+cbor",
the RS rejects the POST request from the AS and replies with an error
response that has a response code equivalent to the CoAP code 4.15
(Unsupported Content-Format). Note that, irrespective of the profile
of ACE used, the RS supports the Content-Format "application/
ace+cbor" if it implements token introspection as defined in
Section 5.9 of [RFC9200].
If the RS supports the Content-Format "application/ace+cbor" but does
not support the "updated_rights" parameter, the RS rejects the POST
request from the AS and replies with an error response that has a
response code equivalent to the CoAP code 4.00 (Bad Request).
In case a POST request to the authz-info endpoint includes the
"updated_rights" parameter, the RS supports the parameter, and any of
the following conditions applies, the RS MUST reject the request and
MUST reply with an error response that has a response code equivalent
to the CoAP code 4.00 (Bad Request):
* The request is not protected.
* The AS is not successfully verified as the originator of the
request.
* The "updated_rights" parameter does not encode the CBOR simple
value true (0xf5).
If none of the error conditions above applies and the request is
valid, then the RS leverages the "updated_rights" parameter encoding
the CBOR simple value true (0xf5) as an indication from the AS that
the access token conveyed in the POST request, namely T_NEW, is not
the first one in its token series. That is, the access token is
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meant to dynamically update the access rights of C, while preserving
the same secure communication association that is shared between C
and the RS.
In this case, the RS uses lookup information specified within T_NEW
to determine whether it stores an access token T_OLD associated with
C and belonging to the same token series of T_NEW. Such lookup
information includes an identifier of the token series to which both
T_NEW and T_OLD belong, and it can further comprise additional
information elements pertaining to the specific profile of ACE used
(e.g., the authentication credential of C that is bound to the access
tokens of the token series).
By leveraging such lookup information, the RS checks whether it
stores an access token T_OLD that belongs to the same token series of
T_NEW, like it would when receiving the request from C and according
to the specific profile of ACE used.
If the RS is currently storing such an old access token T_OLD and
successfully validates the access token T_NEW, then the RS MUST
supersede T_OLD by replacing the corresponding authorization
information with the one specified in the new access token T_NEW.
After that, the RS MUST associate T_NEW with the same secure
communication association with which T_OLD was associated.
If the RS is not currently storing such an old access token T_OLD,
then the RS MUST reject the POST request from the AS and MUST reply
with an error response that has a response code equivalent to the
CoAP code 5.00 (Internal Server Error).
The explicit indication provided by the "updated_rights" parameter
prevents possible ambiguous situations, where the RS might
erroneously believe that the access token conveyed in the POST
request is the first one in a new token series (e.g., following the
deletion of stored access tokens due to memory limitations). ---
Editor's note: elaborate more in the "Security Considerations"
section.
If the AS receives an error response from the RS, the AS replies to C
with an access token response, which includes the "access_token"
parameter specifying the access token T_NEW and the "token_upload"
parameter encoding the value 1 (see Section 3.1).
In case the RS replied to the AS with an error response and could not
find the old access token T_OLD to supersede with T_NEW, the RS does
not have anymore the secure communication association that was
previously shared with C and associated with T_OLD. After receiving
from the AS the access token response including the access token
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T_NEW, C will send a protected POST request including T_NEW to the
authz-info endpoint at the RS, according to the original workflow.
Since the RS does not store T_OLD and does not have the corresponding
secure communication association used by C to protect the POST
request, the RS replies to C with an unprotected error response.
After that, C can send a new access token request to the token
endpoint at the AS, asking for a new access token in a new token
series.
4. Updated "ace_profile" Parameter
This section extends the semantics of the "ace_profile" parameter
defined in [RFC9200] for the OAuth 2.0 token endpoint at the AS.
In addition to what is specified in Sections 5.8.1, 5.8.2, and
5.8.4.3 of [RFC9200], the following applies.
* When sending an access token request to the token endpoint at the
AS (see Section 5.8.1 of [RFC9200]), C MAY include the
"ace_profile" parameter, specifying the identifier of the profile
that C wishes to use towards the RS.
The "ace_profile" parameter MUST NOT be included in an access
token request, if the requested access token is not the first one
of a new token series.
* If the AS receives an access token request for requesting the
first access token in a new token series and the request includes
the "ace_profile" parameter specifying the identifier of a
profile, then the AS proceeds as follows.
In case the AS does not issue access tokens per the profile
specified in the access token request, or C and the RS do not
share that profile, then the AS MUST reject the request and MUST
reply with an error response (see Section 5.8.3 of [RFC9200]).
The error response MUST have a response code equivalent to the
CoAP code 4.00 (Bad Request) and MUST include the error code
"incompatible_ace_profiles".
In case the AS issues an access token to C, the access token MUST
be per the profile whose identifier was specified by the
"ace_profile" parameter in the access token request.
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In case the AS replies to C with an access token response (see
Section 5.8.2 of [RFC9200]), then the response MAY include the
"ace_profile" parameter. If it is included in the access token
response, the "ace_profile" parameter MUST encode the same profile
identifier that was specified by the "ace_profile" parameter of
the corresponding access token request.
The "ace_profile" parameter MUST NOT be included in the access
token response, if the issued access token is not the first one of
a new token series.
5. Coordinating on the Exchange of Public Authentication Credentials
In some profiles of ACE, it is possible for C and the RS to use
public authentication credentials. Depending on the specific
profile, the access token request and response exchanged between C
and the AS can specify those authentication credentials as
transported by value or instead identified by reference. For
instance, this is the case in the EDHOC and OSCORE profile
[I-D.ietf-ace-edhoc-oscore-profile] and in the DTLS profile [RFC9202]
as extended in [I-D.ietf-ace-authcred-dtls-profile].
At some point, the AS (C) might become unable to use a credential
identifier as a reference for accessing the authentication credential
of C (of the RS) obtained earlier, e.g., due to having deleted the
credential from its local storage. This can prevent the AS (C) from
successfully processing an incoming access token request (response)
that specifies the authentication credential of C (of the RS) as
identified by reference. Ultimately, this can prevent the AS from
issuing an access token and C from securely accessing protected
resources at the RS.
Conversely, unbeknown to the AS, C might already be storing the
authentication credential of the RS when sending the access token
request. In such a situation, the AS would specify the
authentication credential of the RS by value in the access token
response. However, it would be sufficient for C that the response
specified the credential of the RS as identified by reference, or
even that the response omitted the credential altogether.
In order to allow C and the AS to coordinate on the exchange of the
authentication credentials of C and the RS, the rest of this section
defines:
* How the AS can instruct C to specify its public authentication
credential by value in the "req_cnf" parameter of an access token
request (see Section 5.1).
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* How C can instruct the AS to specify the public authentication
credential(s) of the RS(s) by value or by reference in the
"rs_cnf" or "rs_cnf2" parameter of an access token response (see
Section 5.2), or instead to omit the credential(s) from the access
token response.
5.1. Instructing C on How to Provide its Authentication Credential
When the AS receives an access token request and this includes the
"req_cnf" parameter identifying the public authentication credential
of C by reference, it might happen that the AS is not able to access
the credential by using the specified reference.
In such a case, the AS MUST reject the request and MUST reply with an
error response (see Section 5.8.3 of [RFC9200]). The error response
MUST have a response code equivalent to the CoAP code 5.00 (Internal
Server Error) and MUST include the error code
"unknown_credential_referenced". The error code and its CBOR
abbreviation are registered in Section 10.5 and Section 10.6,
respectively.
After receiving such an error response, C can send a new access token
request, where the "req_cnf" parameter specifies the authentication
credential of C by value.
5.2. Instructing the AS on How to Provide the RS's Authentication
Credential
When C receives an access token response and this includes the
"req_cnf" or "req_cnf2" parameter identifying the authentication
credential(s) of the RS(s) by reference, it might happen that C is
not able to access the authentication credential(s) by using the
specified reference(s).
Conversely, if the response includes the "rs_cnf" or "rs_cnf2"
parameter specifying the authentication credential(s) of the RS(s) by
value, it might happen that C has already been storing those
credential(s), unbeknown to the AS. In fact, it would have been
sufficient that the "rs_cnf" or "rs_cnf2" parameter identified the
credential(s) by reference, or that neither parameter was included in
the response.
The following extends the semantics of the "rs_cnf" parameter defined
in Section 3.2 of [RFC9201], so that C can include the "rs_cnf"
parameter in an access token request. When doing so, C instructs the
AS about whether and how the access token response should specify the
authentication credential(s) of the RS(s) belonging to the targeted
audience.
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Per its extended semantics, the "rs_cnf" parameter is also OPTIONAL
to include in an access token request when requesting the first
access token in a token series, if the token type is "pop" and
asymmetric keys are used. In any other case, the parameter MUST NOT
be included in an access token request.
When C includes the "rs_cnf" parameter in an access token request
encoded in CBOR, the parameter MUST have one of the following
encodings.
* If the parameter specifies the CBOR simple value true (0xf5), then
it instructs the AS to include in the access token response the
"rs_cnf" or "rs_cnf2" parameter, specifying the authentication
credential(s) of the RS(s) by value.
In the access token response, each pertaining authentication
credential MUST be specified by value.
* If the parameter specifies the CBOR simple value false (0xf4),
then it instructs the AS to include in the access token response
the "rs_cnf" or "rs_cnf2" parameter, specifying the authentication
credential(s) of the RS(s) by reference.
In the access token response, each pertaining authentication
credential MUST be specified by reference, or alternatively by
value only in case that was not possible for the AS to attain.
* If the parameter specifies the CBOR simple value null (0xf6), then
it instructs the AS to omit the "rs_cnf" and "rs_cnf2" parameters
from the access token response.
In the access token response, the "rs_cnf" and "rs_cnf2"
parameters MUST NOT be included.
If the access token request is encoded in JSON, the same as above
applies, with the difference that the "rs_cnf" parameter specifies as
appropriate the corresponding JSON values true, false, or null.
If the AS is not able to comply in the first two cases above, then
the AS MUST reject the request and MUST reply with an error response.
The error response MUST have a response code equivalent to the CoAP
code 5.00 (Internal Server Error).
Irrespective of what "rs_cnf" specifies in the access token request,
C MUST rely on the authentication credential(s) specified by the
parameter "rs_cnf" or "rs_cnf2" in the access token response, as
those that are used by the RS(s) to authenticate.
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If C does not currently store the authentication credential(s) of the
RS(s), then the following applies:
* C MUST NOT include the "rs_cnf" parameter specifying the CBOR
simple value null (0xf6) in an access token request encoded in
CBOR, or the value null in an access token request encoded in
JSON.
* C SHOULD NOT include the "rs_cnf" parameter specifying the CBOR
simple value false (0xf4) in an access token request encoded in
CBOR, or the value false in an access token request encoded in
JSON. Exceptions apply if C is confident that it can later
acquire and validate the authentication credential(s) of the RS(s)
by other means, e.g., by using the references provided by the AS
for retrieval from a trusted repository.
6. Failed Verification of Proof of Possession at the AS
When sending an access token request to the AS (see Section 5.8.1 of
[RFC9200]), a client can include the "req_cnf" parameter defined in
Section 3.1 of [RFC9201] in order to provide the AS with a specific
PoP key to bind to the requested access token.
Typically, the PoP key in question is the client's public key. In
such a case, as per Section 3.1 of [RFC9201], the AS has to verify
proof of possession of the client's private key, i.e., that the
client is indeed in possession of the private key corresponding to
the public key conveyed in the "req_cnf" parameter.
The AS might have previously achieved proof of possession of the
private key in question, e.g., from previous interactions with the
client or through out-of-band means. Alternatively, a profile of ACE
might define how the AS verifies a PoP evidence that the client
computes and provides to the AS by means of a parameter included in
the access token request (e.g., see
[I-D.ietf-ace-group-oscore-profile]).
Irrespective of the method used, if the AS fails to verify the proof
of possession of the client's private key, then the AS MUST reject
the access token request and MUST reply with an error response (see
Section 5.8.3 of [RFC9200]). The error response MUST have a response
code equivalent to the CoAP code 4.00 (Bad Request) and MUST include
the error code "failed_pop_verification". The error code and its
CBOR abbreviation are registered in Section 10.5 and Section 10.6,
respectively.
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7. Updated Payload Format of Error Responses
This section deprecates the original payload format of error
responses conveying an error code, when CBOR is used to encode
message payloads in the ACE framework. That format is referred to,
e.g., when defining the error responses of Sections 5.8.3 and 5.9.3
of [RFC9200].
Also, this section defines a new payload format that allows such
error responses to convey an error code together with further error-
specific information, according to the problem-details format
specified in [RFC9290].
Such error responses MUST have Content-Format set to "application/
concise-problem-details+cbor". The payload of these error responses
MUST be a CBOR map specifying a Concise Problem Details data item
(see Section 2 of [RFC9290]). The CBOR map is formatted as follows:
* It MUST include the Custom Problem Detail entry "ace-error"
registered in Section 10.7 of this document.
This entry is formatted as a CBOR map including only one field,
namely "error-code". The map key for the "error-code" field is
the CBOR integer with value 0. The value of the "error-code"
field is a CBOR integer specifying the error code associated with
the occurred error. This value is taken from the "CBOR Value"
column of the "OAuth Error Code CBOR Mappings" registry
[ACE.OAuth.Error.Code.CBOR.Mappings].
The "error-code" field conveys the same information that the
original payload format conveys through the "error" parameter
(see, e.g., Sections 5.8.3 and 5.9.3 of [RFC9200]).
The CDDL notation [RFC8610] of the "ace-error" entry is given
below.
ace-error = {
&(error-code: 0) => int
}
* It MAY include further Standard Problem Detail entries or Custom
Problem Detail entries (see [RFC9290]). The following Standard
Problem Detail entries are of particular relevance for the ACE
framework.
- "detail" (map key -2): its value is a CBOR text string that
specifies a human-readable diagnostic description of the
occurred error (see Section 2 of [RFC9290]).
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The diagnostic text is intended for software engineers as well
as for device and network operators in order to aid in
debugging and provide context for possible intervention. The
diagnostic message SHOULD be logged by the sender of the error
response. The "detail" entry is unlikely to be relevant in an
unattended setup where human intervention is not expected.
When the Standard Problem Detail entry "detail" is included, it
conveys the same information that the original payload format
conveys through the "error_description" parameter (see, e.g.,
Sections 5.8.3 and 5.9.3 of [RFC9200]).
- "instance" (map key -3): its value is a URI reference
identifying the specific occurrence of the error (see Section 2
of [RFC9290]).
When the Standard Problem Detail entry "instance" is included,
it conveys the same information that the original payload
format conveys through the "error_uri" parameter (see, e.g.,
Sections 5.8.3 and 5.9.3 of [RFC9200]).
An example of an error response using the problem-details format is
shown in Figure 10.
Header: Bad Request (Code=4.00)
Content-Format: 257 (application/concise-problem-details+cbor)
Payload:
{
/ title / -1 : "Incompatible ACE profile",
/ detail / -2 : "The RS supports only the OSCORE profile",
e'ace-error': {
/ error_code / 0: 8 / incompatible_ace_profiles /
}
}
Figure 10: Example of Error Response with Problem Details.
When the ACE framework is used with CBOR for encoding message
payloads, the following applies.
* It is RECOMMENDED that authorization servers, clients, and
resource servers support the payload format defined in this
section.
* Authorization servers, clients, and resource servers that support
the payload format defined in this section MUST use it when
composing an outgoing error response that conveys an error code.
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8. Updated Requirements on Profiles of ACE
Appendix C of [RFC9200] compiles a list of requirements on the
profiles of ACE. This document amends two of those requirements as
follows.
The text of the fifth requirement
| Specify the security protocol the client and RS must use to
| protect their communication (e.g., OSCORE or DTLS). This must
| provide encryption and integrity and replay protection
| (Section 5.8.4.3).
is replaced by the following text:
| Specify the security protocol the client and RS must use to
| protect their communication (e.g., OSCORE or DTLS). In
| combination with the used communication protocol, this must
| provide encryption, integrity and replay protection, and a binding
| between requests and responses (Section 5.8.4.3 and Section 6.5).
The text of the tenth requirement
| Specify the communication and security protocol for interactions
| between the client and AS. This must provide encryption,
| integrity protection, replay protection, and a binding between
| requests and responses (Sections 5 and 5.8).
is replaced by the following text:
| Specify the communication and security protocol for interactions
| between the client and AS. The combined use of those protocols
| must provide encryption, integrity protection, replay protection,
| and a binding between requests and responses (Sections 5 and 5.8).
At the time of writing, all the profiles of ACE that are published as
RFC (i.e., [RFC9202][RFC9203][RFC9431]) already comply with the two
updated requirements as formulated above.
9. Security Considerations
The same security considerations from the ACE framework for
Authentication and Authorization [RFC9200] apply to this document,
together with those from the specific profile of ACE used, e.g., [RFC
9202][RFC9203][RFC9431][I-D.ietf-ace-edhoc-oscore-profile][I-D.ietf-a
ce-group-oscore-profile][RFC9431].
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When using the problem-details format defined in [RFC9290] for error
responses, then the privacy and security considerations from Sections
4 and 5 of [RFC9290] also apply.
Editor's note: add more security considerations.
10. IANA Considerations
This document has the following actions for IANA.
Note to RFC Editor: Please replace all occurrences of "[RFC-XXXX]"
with the RFC number of this specification and delete this paragraph.
10.1. OAuth Parameters Registry
IANA is asked to add the following entries to the "OAuth Parameters"
registry within the "OAuth Parameters" registry group.
* Name: token_upload
* Parameter Usage Location: token request, token response
* Change Controller: IETF
* Reference: [RFC-XXXX]
* Name: token_hash
* Parameter Usage Location: token response
* Change Controller: IETF
* Reference: [RFC-XXXX]
* Name: to_rs
* Parameter Usage Location: token request
* Change Controller: IETF
* Reference: [RFC-XXXX]
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* Name: from_rs
* Parameter Usage Location: token response
* Change Controller: IETF
* Reference: [RFC-XXXX]
* Name: rs_cnf2
* Parameter Usage Location: token response
* Change Controller: IETF
* Reference: [RFC-XXXX]
* Name: audience2
* Parameter Usage Location: token response
* Change Controller: IETF
* Reference: [RFC-XXXX]
* Name: anchor_cnf
* Parameter Usage Location: token response
* Change Controller: IETF
* Reference: [RFC-XXXX]
* Name: token_series_id
* Parameter Usage Location: token request, token response
* Change Controller: IETF
* Reference: [RFC-XXXX]
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* Name: updated_rights
* Parameter Usage Location: as-rs request
* Change Controller: IETF
* Reference: [RFC-XXXX]
In the same registry, IANA is asked to update the entries for the
following OAuth parameters identified by their name, so that the
content of the "Parameter Usage Location" column and of the
"Reference" column is as below:
* access_token
- Parameter Usage Location: authorization response, token
response, as-rs request
- Reference: [RFC6749][RFC-XXXX]
* rs_cnf
- Parameter Usage Location: token request, token response
- Reference: [RFC9201, Section 5][RFC-XXXX, Section 5.2]
* nonce1
- Parameter Usage Location: client-rs request, as-rs request
- Reference: [RFC9203][RFC-XXXX]
* nonce2
- Parameter Usage Location: rs-client response, rs-as response
- Reference: [RFC9203][RFC-XXXX]
* ace_client_recipientid
- Parameter Usage Location: client-rs request, as-rs request
- Reference: [RFC9203][RFC-XXXX]
* ace_server_recipientid
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- Parameter Usage Location: rs-client response, rs-as response
- Reference: [RFC9203][RFC-XXXX]
* sign_info
- Parameter Usage Location: client-rs request, rs-client
response, as-rs request, rs-as response
- Reference: [RFC9594][RFC-XXXX]
* kdcchallenge
- Parameter Usage Location: rs-client response, rs-as response
- Reference: [RFC9594][RFC-XXXX]
10.2. OAuth Parameters CBOR Mappings Registry
IANA is asked to add the following entries to the "OAuth Parameters
CBOR Mappings" registry within the "Authentication and Authorization
for Constrained Environments (ACE)" registry group, following the
procedure specified in [RFC9200].
* Name: token_upload
* CBOR Key: TBD (value between 1 and 255)
* Value Type: unsigned integer
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
* Name: token_hash
* CBOR Key: TBD (value between 1 and 255)
* Value Type: unsigned integer
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
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* Name: to_rs
* CBOR Key: TBD (value between 1 and 255)
* Value Type: Null or byte string or #6.<uint>(bstr)
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
* Name: from_rs
* CBOR Key: TBD (value between 1 and 255)
* Value Type: byte string or #6.<uint>(bstr)
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
* Name: rs_cnf2
* CBOR Key: TBD (value between 1 and 255)
* Value Type: array
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
* Name: audience2
* CBOR Key: TBD (value between 1 and 255)
* Value Type: array
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
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* Name: anchor_cnf
* CBOR Key: TBD (value between 1 and 255)
* Value Type: array
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
* Name: token_series_id
* CBOR Key: TBD (value between 1 and 255)
* Value Type: byte string
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
* Name: updated_rights
* CBOR Key: TBD (value between 1 and 255)
* Value Type: True
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
In the same registry, IANA is asked to update the entry for the OAuth
parameter with name "rs_cnf", so that the content of the "Value Type"
column and of the "Reference" column is as below:
* Value Type: True or False or Null or map
* Reference: [RFC9201, Section 3.2][RFC-XXXX, Section 5.2]
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10.3. JSON Web Token Claims Registry
IANA is asked to add the following entry to the "JSON Web Token
Claims" registry within the "JSON Web Token (JWT)" registry group,
following the procedure specified in [RFC7519].
* Claim Name: token_series_id
* Claim Description: The identifier of a token series
* Change Controller: IETF
* Reference: [RFC-XXXX]
10.4. CBOR Web Token (CWT) Claims Registry
IANA is asked to add the following entry to the "CBOR Web Token (CWT)
Claims" registry within the "CBOR Web Token (CWT) Claims" registry
group, following the procedure specified in [RFC8392].
* Claim Name: token_series_id
* Claim Description: The identifier of a token series
* JWT Claim Name: token_series_id
* Claim Key: TBD (value between 1 and 255)
* Claim Value Type: byte string
* Change Controller: IETF
* Reference: [RFC-XXXX, Section 3.6]
10.5. OAuth Extensions Error Registry
IANA is asked to add the following entries to the "OAuth Extensions
Error Registry" within the "OAuth Parameters" registry group.
* Name: unknown_credential_referenced
* Usage Location: token error response
* Protocol Extension: [RFC-XXXX]
* Change Controller: IETF
* Reference: [RFC-XXXX, Section 5]
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* Name: failed_pop_verification
* Usage Location: token error response
* Protocol Extension: [RFC-XXXX]
* Change Controller: IETF
* Reference: [RFC-XXXX, Section 6]
10.6. OAuth Error Code CBOR Mappings Registry
IANA is asked to add the following entries to the "OAuth Error Code
CBOR Mappings" registry within the "Authentication and Authorization
for Constrained Environments (ACE)" registry group.
* Name: unknown_credential_referenced
* CBOR Value: TBD (value between 1 and 255)
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
* Name: failed_pop_verification
* CBOR Value: TBD (value between 1 and 255)
* Reference: [RFC-XXXX]
* Original Specification: [RFC-XXXX]
10.7. Custom Problem Detail Keys Registry
IANA is asked to register the following entry in the "Custom Problem
Detail Keys" registry within the "Constrained RESTful Environments
(CoRE) Parameters" registry group.
* Key Value: TBD (value between 0 and 23)
* Name: ace-error
* Brief Description: Carry ACE [RFC9200] problem details in a
Concise Problem Details data item.
* Change Controller: IETF
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* Reference: [RFC-XXXX, Section 7]
11. References
11.1. Normative References
[ACE.OAuth.Error.Code.CBOR.Mappings]
IANA, "OAuth Error Code CBOR Mappings",
<https://www.iana.org/assignments/ace/ace.xhtml#oauth-
error-code-cbor-mappings>.
[I-D.ietf-ace-edhoc-oscore-profile]
Selander, G., Mattsson, J. P., Tiloca, M., and R. Höglund,
"Ephemeral Diffie-Hellman Over COSE (EDHOC) and Object
Security for Constrained Environments (OSCORE) Profile for
Authentication and Authorization for Constrained
Environments (ACE)", Work in Progress, Internet-Draft,
draft-ietf-ace-edhoc-oscore-profile-10, 1 March 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-ace-
edhoc-oscore-profile-10>.
[IANA.Hash.Algorithms]
IANA, "Named Information Hash Algorithm Registry",
<https://www.iana.org/assignments/named-information/named-
information.xhtml>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/rfc/rfc3629>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/rfc/rfc4648>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/rfc/rfc5280>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/rfc/rfc6749>.
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[RFC6920] Farrell, S., Kutscher, D., Dannewitz, C., Ohlman, B.,
Keranen, A., and P. Hallam-Baker, "Naming Things with
Hashes", RFC 6920, DOI 10.17487/RFC6920, April 2013,
<https://www.rfc-editor.org/rfc/rfc6920>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/rfc/rfc7252>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/rfc/rfc7519>.
[RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of-
Possession Key Semantics for JSON Web Tokens (JWTs)",
RFC 7800, DOI 10.17487/RFC7800, April 2016,
<https://www.rfc-editor.org/rfc/rfc7800>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/rfc/rfc8259>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/rfc/rfc8392>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/rfc/rfc8446>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.
[RFC8747] Jones, M., Seitz, L., Selander, G., Erdtman, S., and H.
Tschofenig, "Proof-of-Possession Key Semantics for CBOR
Web Tokens (CWTs)", RFC 8747, DOI 10.17487/RFC8747, March
2020, <https://www.rfc-editor.org/rfc/rfc8747>.
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[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>.
[RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/rfc/rfc9052>.
[RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053,
August 2022, <https://www.rfc-editor.org/rfc/rfc9053>.
[RFC9200] Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
H. Tschofenig, "Authentication and Authorization for
Constrained Environments Using the OAuth 2.0 Framework
(ACE-OAuth)", RFC 9200, DOI 10.17487/RFC9200, August 2022,
<https://www.rfc-editor.org/rfc/rfc9200>.
[RFC9201] Seitz, L., "Additional OAuth Parameters for Authentication
and Authorization for Constrained Environments (ACE)",
RFC 9201, DOI 10.17487/RFC9201, August 2022,
<https://www.rfc-editor.org/rfc/rfc9201>.
[RFC9202] Gerdes, S., Bergmann, O., Bormann, C., Selander, G., and
L. Seitz, "Datagram Transport Layer Security (DTLS)
Profile for Authentication and Authorization for
Constrained Environments (ACE)", RFC 9202,
DOI 10.17487/RFC9202, August 2022,
<https://www.rfc-editor.org/rfc/rfc9202>.
[RFC9203] Palombini, F., Seitz, L., Selander, G., and M. Gunnarsson,
"The Object Security for Constrained RESTful Environments
(OSCORE) Profile of the Authentication and Authorization
for Constrained Environments (ACE) Framework", RFC 9203,
DOI 10.17487/RFC9203, August 2022,
<https://www.rfc-editor.org/rfc/rfc9203>.
[RFC9277] Richardson, M. and C. Bormann, "On Stable Storage for
Items in Concise Binary Object Representation (CBOR)",
RFC 9277, DOI 10.17487/RFC9277, August 2022,
<https://www.rfc-editor.org/rfc/rfc9277>.
[RFC9290] Fossati, T. and C. Bormann, "Concise Problem Details for
Constrained Application Protocol (CoAP) APIs", RFC 9290,
DOI 10.17487/RFC9290, October 2022,
<https://www.rfc-editor.org/rfc/rfc9290>.
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[RFC9430] Bergmann, O., Preuß Mattsson, J., and G. Selander,
"Extension of the Datagram Transport Layer Security (DTLS)
Profile for Authentication and Authorization for
Constrained Environments (ACE) to Transport Layer Security
(TLS)", RFC 9430, DOI 10.17487/RFC9430, July 2023,
<https://www.rfc-editor.org/rfc/rfc9430>.
[RFC9431] Sengul, C. and A. Kirby, "Message Queuing Telemetry
Transport (MQTT) and Transport Layer Security (TLS)
Profile of Authentication and Authorization for
Constrained Environments (ACE) Framework", RFC 9431,
DOI 10.17487/RFC9431, July 2023,
<https://www.rfc-editor.org/rfc/rfc9431>.
[RFC9770] Tiloca, M., Palombini, F., Echeverria, S., and G. Lewis,
"Notification of Revoked Access Tokens in the
Authentication and Authorization for Constrained
Environments (ACE) Framework", RFC 9770,
DOI 10.17487/RFC9770, June 2025,
<https://www.rfc-editor.org/rfc/rfc9770>.
[SHA-256] NIST, "Secure Hash Standard", NIST FIPS PUB 180-4, DOI
10.6028/NIST.FIPS.180-4 , August 2015,
<https://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.180-4.pdf>.
11.2. Informative References
[I-D.ietf-ace-authcred-dtls-profile]
Tiloca, M. and J. P. Mattsson, "Additional Formats of
Authentication Credentials for the Datagram Transport
Layer Security (DTLS) Profile for Authentication and
Authorization for Constrained Environments (ACE)", Work in
Progress, Internet-Draft, draft-ietf-ace-authcred-dtls-
profile-03, 7 January 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-ace-
authcred-dtls-profile-03>.
[I-D.ietf-ace-group-oscore-profile]
Tiloca, M., Höglund, R., and F. Palombini, "The Group
Object Security for Constrained RESTful Environments
(Group OSCORE) Profile of the Authentication and
Authorization for Constrained Environments (ACE)
Framework", Work in Progress, Internet-Draft, draft-ietf-
ace-group-oscore-profile-05, 3 September 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-ace-
group-oscore-profile-05>.
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[RFC9594] Palombini, F. and M. Tiloca, "Key Provisioning for Group
Communication Using Authentication and Authorization for
Constrained Environments (ACE)", RFC 9594,
DOI 10.17487/RFC9594, September 2024,
<https://www.rfc-editor.org/rfc/rfc9594>.
Appendix A. Benefits for ACE Profiles
For any profile of ACE, the following holds.
* The SDC workflow defined in Section 2 is effectively possible to
use. This is beneficial for deployments where the communication
leg between C and the RS is constrained, but the communication leg
between the AS and RS is not.
* When the SDC workflow is used, the "token_upload" parameter
defined in Section 3.1 is used:
- To inform the AS about C opting in to use the SDC workflow.
- To request the AS that the follow-up access token response
includes certain information, if the AS has successfully
uploaded the access token to the RS.
- To inform C that the AS has attempted to upload the issued
access token to the RS, specifying whether the uploading has
succeeded or failed.
* When the SDC workflow is used, it remains possible for C to always
obtain the issued access token from the AS.
That is, by specifying the value 2 for the "token_upload"
parameter in the access token request, C will ensure to receive
the access token from the AS, even if the AS successfully uploads
the access token to the RS on behalf of C.
This is useful in profiles of ACE where C can re-upload the same
access token to the RS by itself, e.g., in order to perform a key
update like defined for the OSCORE profile [RFC9203].
A.1. DTLS Profile
When the RPK mode of the DTLS profile is used (see Section 3.2 of
[RFC9202]), it becomes possible for the AS to effectively issue an
access token intended to an audience that includes multiple RSs.
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This is enabled by the parameters "rs_cnf2" and "audience2" defined
in Section 3.4, as well as by the "anchor_cnf" parameter defined in
Section 3.5. This seamlessly applies also if the profile uses
Transport Layer Security (TLS) [RFC8446] as defined in [RFC9430].
A.2. EDHOC and OSCORE Profile
When the EDHOC and OSCORE profile is used
[I-D.ietf-ace-edhoc-oscore-profile], it becomes possible for the AS
to effectively issue an access token intended to an audience that
includes multiple RSs.
This is enabled by the parameters "rs_cnf2" and "audience2" defined
in Section 3.4, as well as by the "anchor_cnf" parameter defined in
Section 3.5.
Appendix B. CDDL Model
This section is to be removed before publishing as an RFC.
; OAuth Parameters CBOR Mappings
token_upload = 49
token_hash = 50
to_rs = 51
from_rs = 52
rs_cnf2 = 53
audience2 = 54
anchor_cnf = 55
token_series_id_param = 56
; CBOR Web Token (CWT) Claims
token_series_id_claim = 42
; CWT Confirmation Methods
x5chain = 24
; Custom Problem Detail Keys Registry
ace-error = 2
Figure 11: CDDL model
Appendix C. Document Updates
This section is to be removed before publishing as an RFC.
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C.1. Version -06 to -07
* Updated requirements for using "rs_cnf" in an access token
request.
* More precise requirements on including/omitting parameters in
access token request and response.
* Specified parameter encoding when messages are encoded in JSON.
* Moved content on dynamic update of access rights to the section
about the "updated_rights" parameter.
* Clarifications:
- Access token responses are successful by definition.
- Successful response in general vs. response with 2.01 code.
- Explained the case where the RS has forgotten the access token
to supersede.
* IANA considerations: update entry for "access_token" in the "OAuth
Parameters" registry.
* Editorial fixes and improvements.
C.2. Version -05 to -06
* Defined dynamic update of access rights in the SDC workflow.
* Defined the new "updated_rights" parameter.
* Clarified practical requirements at the AS for processing the
"to_rs" parameter.
* IANA considerations: update in the "Parameter Usage Location"
column for some entries of the "OAuth Parameters" registry.
* Adjusted abbreviations in the CDDL model to avoid collisions.
* Removed appendix with placeholder ideas.
* Editorial fixes and improvements.
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C.3. Version -04 to -05
* Error handling and error code for failed PoP verification at the
AS.
* Extended definition of the parameters "to_rs" and "from_rs".
* Fixes and presentation improvements in the IANA considerations.
* Updated references.
* Revised order of some sections.
* Editorial fixes and improvements.
C.4. Version -03 to -04
* Updated document title.
* Defined name for the new workflow.
* Improved definition of "token series".
* Revised note on the new workflow suitable for "unaware" clients.
* Revised criterion for the AS to choose a token series identifier.
* Extended semantics of the "ace_profile" parameter.
* Specified means for C and the AS to coordinate on the exchange of
public authentication credentials.
* Removed content on bidirectional access control.
* Suggested value ranges for codepoints to register.
* Editorial fixes and improvements.
C.5. Version -02 to -03
* Defined parameter and claim "token_series_id".
* Defined parameters "to_rs" and "from_rs".
* Defined use of "to_rs" and "from_rs" in the OSCORE profile.
* Lowercase use of "client", "resource server", and "authorization
server".
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* Fixed naming of parameters/claims for audience.
* Split elision and comments in the examples in CBOR Diagnostic
Notation.
* SHA-256 is mandatory to implement for computing token hashes.
* Fixes in the IANA considerations.
* Removed (parts of) appendices that are not needed anymore.
* Clarifications and editorial improvements.
C.6. Version -01 to -02
* CBOR diagnostic notation uses placeholders from a CDDL model.
* Note on the new workflow supporting also non-ACE clients.
* Revised semantics of the "token_upload" parameter.
* Defined the new "token_hash" parameter.
* First definition of bidirectional access control through a single
access token.
* Revised and extended considerations and next steps in appendices.
* Clarifications and editorial improvements.
C.7. Version -00 to -01
* Definition of the "token series" moved to the "Terminology"
section.
* Clarifications and fixes on using parameters in messages.
* Amended two of the requirements on profiles of the framework.
* The client has to opt-in for using the new workflow.
* Parameter "token_uploaded" renamed to "token_upload".
* Updated format of error response payload to use RFC 9290.
* Security considerations inherited from other documents.
* Editorial fixes and improvements.
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Acknowledgments
The authors sincerely thank Christian Amsüss, Rikard Höglund, and
Dave Robin for their comments and feedback.
This work was supported by the Sweden's Innovation Agency VINNOVA
within the EUREKA CELTIC-NEXT project CYPRESS; and by the H2020
project SIFIS-Home (Grant agreement 952652).
Authors' Addresses
Marco Tiloca
RISE AB
Isafjordsgatan 22
SE-16440 Kista
Sweden
Email: marco.tiloca@ri.se
Göran Selander
Ericsson AB
Torshamnsgatan 23
SE-16440 Stockholm Kista
Sweden
Email: goran.selander@ericsson.com
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