rfc9597.original   rfc9597.txt 
COSE T. Looker Internet Engineering Task Force (IETF) T. Looker
Internet-Draft Mattr Request for Comments: 9597 Mattr
Intended status: Standards Track M. Jones Category: Standards Track M.B. Jones
Expires: 1 June 2024 Self-Issued Consulting ISSN: 2070-1721 Self-Issued Consulting
29 November 2023 June 2024
CBOR Web Token (CWT) Claims in COSE Headers CBOR Web Token (CWT) Claims in COSE Headers
draft-ietf-cose-cwt-claims-in-headers-10
Abstract Abstract
This document describes how to include CBOR Web Token (CWT) claims in This document describes how to include CBOR Web Token (CWT) claims in
the header parameters of any COSE structure. This functionality the header parameters of any CBOR Object Signing and Encryption
helps to facilitate applications that wish to make use of CBOR Web (COSE) structure. This functionality helps to facilitate
Token (CWT) claims in encrypted COSE structures and/or COSE applications that wish to make use of CWT claims in encrypted COSE
structures featuring detached signatures, while having some of those structures and/or COSE structures featuring detached signatures,
claims be available before decryption and/or without inspecting the while having some of those claims be available before decryption and/
detached payload. Another use case is using CWT claims with payloads or without inspecting the detached payload. Another use case is
that are not CWT Claims Sets, including payloads that are not CBOR at using CWT claims with payloads that are not CWT Claims Sets,
all. including payloads that are not CBOR at all.
Discussion Venues
This note is to be removed before publishing as an RFC.
Source for this draft and an issue tracker can be found at
https://github.com/tplooker/draft-ietf-cose-cwt-claims-in-headers.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on 1 June 2024. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9597.
Copyright Notice Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
1.1. Requirements Terminology . . . . . . . . . . . . . . . . 3 1.1. Requirements Terminology
2. Representation . . . . . . . . . . . . . . . . . . . . . . . 3 2. Representation
3. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4 3. Privacy Considerations
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. References
6.1. Normative References . . . . . . . . . . . . . . . . . . 5 6.1. Normative References
6.2. Informative References . . . . . . . . . . . . . . . . . 6 6.2. Informative References
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 6 Acknowledgements
Appendix B. Document History . . . . . . . . . . . . . . . . . . 6 Authors' Addresses
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
In some applications of COSE, it is useful to have a standard In some applications of COSE, it is useful to have a standard
representation of CWT claims [RFC8392] available in the header representation of CWT claims [RFC8392] available in the header
parameters. These include encrypted COSE structures, which may or parameters. These include encrypted COSE structures, which may or
may not be an encrypted CWT and/or those featuring a detached may not be an encrypted CWT, and/or those featuring a detached
signature. Another use case is using CWT claims with payloads that signature. Another use case is using CWT claims with payloads that
are not CWT Claims Sets, including payloads that are not CBOR at all. are not CWT Claims Sets, including payloads that are not CBOR at all.
For instance, an application might want to include an "iss" (issuer) For instance, an application might want to include an "iss" (issuer)
claim in a COSE_Sign1 structure when the payload being signed is a claim in a COSE_Sign1 structure when the payload being signed is a
non-CBOR data structure, such as a bitmap image, and the issuer value non-CBOR data structure, such as a bitmap image, and the issuer value
is used for key discovery. is used for key discovery.
Section 5.3 of JSON Web Token (JWT) [RFC7519] defined a similar Section 5.3 of [RFC7519], "JSON Web Token (JWT)", defined a similar
mechanism for expressing selected JWT based claims as JOSE header mechanism for expressing selected JWT-based claims as JSON Object
parameters. This JWT feature was motivated by the desire to have Signing and Encryption (JOSE) header parameters. This JWT feature
certain claims, such as the Issuer value, be visible to software was motivated by the desire to have certain claims, such as the
processing the JWT, even though the JWT is encrypted. No Issuer value, be visible to software processing the JWT, even though
corresponding feature was standardized for CWTs, which was an the JWT is encrypted. No corresponding feature was standardized for
omission that this specification corrects. CWTs, which was an omission that this specification corrects.
Directly including CWT claim values as COSE header parameter values Directly including CWT claim values as COSE header parameter values
would not work, since there are conflicts between the numeric header would not work, since there are conflicts between the numeric header
parameter assignments and the numeric CWT claim assignments. parameter assignments and the numeric CWT claim assignments.
Instead, this specification defines a single header parameter Instead, this specification defines a single header parameter
registered in the IANA "COSE Header Parameters" registry that creates registered in the IANA "COSE Header Parameters" registry that creates
a location to store CWT claims in a COSE header parameter. a location to store CWT claims in a COSE header parameter.
This specification does not define how to use CWT claims and their This specification does not define how to use CWT claims and their
semantics for particular applications, whether they are in the COSE semantics for particular applications, whether they are in the COSE
payload or the CWT Claims header parameter, or both. Therefore, payload or the CWT Claims header parameter, or both. Therefore,
understanding how to process the CWT Claims header parameter requires understanding how to process the CWT Claims header parameter requires
unambiguously knowing the intended interpretation. The necessary unambiguously knowing the intended interpretation. The necessary
information about this MAY come from other header parameters. Unless information about this MAY come from other header parameters. Unless
there already is a natural way of providing this information at an there already is a natural way of providing this information at an
appropriate level of integrity protection and authentication, a appropriate level of integrity protection and authentication, a
RECOMMENDED way to include this information in the COSE structure is RECOMMENDED way to include this information in the COSE structure is
use of the typ (type) Header Parameter use of the "typ" (type) Header Parameter [RFC9596]. Other methods
[I-D.ietf-cose-typ-header-parameter]. Other methods for determining for determining the intended interpretation MAY also be used.
the intended interpretation MAY also be used. Recipients of the CWT Recipients of the CWT Claims header parameter MUST NOT use the
Claims header parameter MUST NOT use the information in the CWT information in the CWT Claims header parameter beyond the integrity
Claims header parameter beyond the integrity protection or protection or authentication afforded to the CWT Claims header and
authentication afforded to the CWT Claims header and the information the information used to derive its intended interpretation.
used to derive its intended interpretation.
1.1. Requirements Terminology 1.1. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Representation 2. Representation
This document defines the following COSE header parameter: This document defines the following COSE header parameter:
+========+================+=======+=============+===================+ +========+=======+=======+=============+===========================+
| Name | Label | Value | Value | Description | | Name | Label | Value | Value | Description |
| | | Type | Registry | | | | | Type | Registry | |
+========+================+=======+=============+===================+ +========+=======+=======+=============+===========================+
| CWT | TBD (requested | map | [IANA.COSE] | Location for | | CWT | 15 | map | [IANA.COSE] | Location for CWT Claims |
| Claims | assignment 15) | | | CWT Claims in | | Claims | | | | in COSE Header Parameters |
| | | | | COSE Header | +--------+-------+-------+-------------+---------------------------+
| | | | | Parameters |
+--------+----------------+-------+-------------+-------------------+
Table 1 Table 1
The following is a non-normative description for the value type of The following is a non-normative description for the value type of
the CWT claim header parameter using CDDL [RFC8610]. the CWT claim header parameter using CDDL [RFC8610].
CWT-Claims = { CWT-Claims = {
* Claim-Label => any * Claim-Label => any
} }
Claim-Label = int / text Claim-Label = int / text
In cases where CWT claims are present both in the payload and the In cases where CWT claims are present both in the payload and the
header of a CWT, an application receiving such a structure MUST header of a CWT, an application receiving such a structure MUST
verify that their values are identical, unless the application verify that their values are identical, unless the application
defines other specific processing rules for these claims. defines other specific processing rules for these claims.
It is RECOMMENDED that the CWT Claims header parameter is used only It is RECOMMENDED that the CWT Claims header parameter only be used
in a protected header to avoid the contents being malleable. The in a protected header to avoid the contents being malleable. The
header parameter MUST only occur once in either the protected or header parameter MUST only occur once in either the protected or
unprotected header of a COSE structure. unprotected header of a COSE structure.
The CWT Claims header parameter MAY be used in any COSE object using The CWT Claims header parameter MAY be used in any COSE object using
header parameters, such as COSE_Sign objects. Its use is not header parameters, such as COSE_Sign objects. Its use is not
restricted to CWTs. restricted to CWTs.
3. Privacy Considerations 3. Privacy Considerations
skipping to change at page 5, line 9 skipping to change at line 172
4. Security Considerations 4. Security Considerations
Implementers should also review the security considerations for CWT, Implementers should also review the security considerations for CWT,
which are documented in Section 8 of [RFC8392]. which are documented in Section 8 of [RFC8392].
As described in [RFC9052], if the COSE payload is transported As described in [RFC9052], if the COSE payload is transported
separately ("detached content"), then it is the responsibility of the separately ("detached content"), then it is the responsibility of the
application to ensure that it will be transported without changes. application to ensure that it will be transported without changes.
The reason for applications to verify that CWT claims that are The reason for applications to verify that CWT claims present in both
present both in the payload and the header of a CWT are identical, the payload and the header of a CWT are identical, unless it defines
unless it defines other specific processing rules for these claims, other specific processing rules for these claims, is to eliminate
is to eliminate potential confusion that might arise by having potential confusion that might arise by having different values for
different values for the same claim, which could result in the same claim, which could result in inconsistent processing of such
inconsistent processing of such claims. claims.
Processing information in claims prior to validating that their Processing information in claims prior to validating that their
integrity is cryptographically secured can pose security risks. This integrity is cryptographically secure can pose security risks. This
is true whether the claims are in the payload or a header parameter. is true whether the claims are in the payload or a header parameter.
Implementers must ensure that any tentative decisions made based on Implementers must ensure that any tentative decisions made based on
previously unverified information are confirmed once the previously unverified information are confirmed once the
cryptographic processing has been completed. This includes any cryptographic processing has been completed. This includes any
information that was used to derive the intended interpretation of information that was used to derive the intended interpretation of
the CWT claims parameter. the CWT claims parameter.
5. IANA Considerations 5. IANA Considerations
IANA is requested to register the new COSE header parameter "CWT IANA has registered the new COSE header parameter "CWT Claims"
Claims" in the table in Section 2 in the "COSE Header Parameters" defined in Table 1 in the "COSE Header Parameters" registry
registry [IANA.COSE]. [IANA.COSE].
6. References 6. References
6.1. Normative References 6.1. Normative References
[I-D.ietf-cose-typ-header-parameter]
Jones, M. B. and O. Steele, "COSE "typ" (type) Header
Parameter", Work in Progress, Internet-Draft, draft-ietf-
cose-typ-header-parameter-01, 7 November 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-cose-
typ-header-parameter-01>.
[IANA.COSE] [IANA.COSE]
IANA, "COSE Header Parameters", IANA, "COSE Header Parameters",
<https://www.iana.org/assignments/cose/cose.xhtml#header- <https://www.iana.org/assignments/cose/>.
parameters>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, [RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/info/rfc8392>. May 2018, <https://www.rfc-editor.org/info/rfc8392>.
[RFC9596] Jones, M. and O. Steele, "CBOR Object Signing and
Encryption (COSE) "typ" (type) Header Parameter",
RFC 9596, DOI 10.17487/RFC9596, June 2024,
<https://www.rfc-editor.org/info/rfc9596>.
6.2. Informative References 6.2. Informative References
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>. <https://www.rfc-editor.org/info/rfc7519>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/info/rfc8610>. June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE): [RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052, Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022, DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/info/rfc9052>. <https://www.rfc-editor.org/info/rfc9052>.
Appendix A. Acknowledgements Acknowledgements
We would like to thank Daisuke Ajitomi, Claudio Allocchio, Carsten We would like to thank Daisuke Ajitomi, Claudio Allocchio, Carsten
Bormann, Laurence Lundblade, Ivaylo Petrov, Ines Robles, Orie Steele, Bormann, Laurence Lundblade, Ivaylo Petrov, Ines Robles, Orie Steele,
Hannes Tschofenig, Paul Wouters, and Peter Yee for their valuable Hannes Tschofenig, Paul Wouters, and Peter Yee for their valuable
contributions to this specification. contributions to this specification.
Appendix B. Document History
-09
* Described use cases where CWT claims can't be put in the payload
in response to Hannes Tschofenig's IotDir review.
* Said that profiles specify the semantics of the CWT claims in
response to Carsten Bormann's feedback.
-08
* Added Security Consideration about profiles and processing CWT
claims.
-07
* Added Privacy Consideration about unencrypted claims in header
parameters.
* Added Security Consideration about detached content.
* Added Security Consideration about claims that are present both in
the payload and the header of a CWT.
* Changed requested IANA COSE Header Parameter assignment number
from 13 to 15 due to subsequent assignments of 13 and 14.
* Acknowledged last call reviewers.
-06
* Changed requested IANA COSE Header Parameter assignment number
from 11 to 13 due to Countersignature being allocated 11.
* Reference correct registry IANA COSE Header Parameters.
-05
* Added Acknowledgements section.
* Addressed WGLC feedback. Specifically...
* Added statement about being able to use the header parameter in
any COSE object.
* Moved statment about verifing that claim values present in both
the header and payload are identical from the Security
Considerations to the body of the specification.
-04
* Update author affiliation.
* Add standard reference to RFC terminology.
* Added reference to security considerations from RFC8392.
-03
* Added recommendation around header treatment in protected vs
unprotected.
-02
* Added CDDL description for CWT claim value.
-01
* Changed example from Key ID to Issuer.
-00
* Created draft-ietf-cose-cwt-claims-in-headers-00 from draft-
looker-cose-cwt-claims-in-headers-00 following working group
adoption.
Authors' Addresses Authors' Addresses
Tobias Looker Tobias Looker
Mattr Mattr
Email: tobias.looker@mattr.global Email: tobias.looker@mattr.global
Michael B. Jones Michael B. Jones
Self-Issued Consulting Self-Issued Consulting
Email: michael_b_jones@hotmail.com Email: michael_b_jones@hotmail.com
URI: https://self-issued.info/ URI: https://self-issued.info/
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