COSE T. Looker Internet-Draft Mattr Intended status: Standards Track M. Jones Expires: 9 January 2023 Microsoft 8 July 2022 CBOR Web Token (CWT) Claims in COSE Headers draft-ietf-cose-cwt-claims-in-headers-00 Abstract This document describes how to include CBOR Web Token (CWT) claims in the header parameters of any COSE structure. This functionality helps to facilitate applications that wish to make use of CBOR Web Token (CWT) claims in encrypted COSE structures and/or COSE structures featuring detached signatures, while having some of those claims be available before decryption and/or without inspecting the detached payload. 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 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 working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any 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 9 January 2023. Copyright Notice Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. Looker & Jones Expires 9 January 2023 [Page 1] Internet-Draft CBOR Web Token (CWT) Claims in COSE Head July 2022 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 extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Representation . . . . . . . . . . . . . . . . . . . . . . . 3 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 3 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 7. Normative References . . . . . . . . . . . . . . . . . . . . 3 8. Informative References . . . . . . . . . . . . . . . . . . . 3 Appendix A. Document History . . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction In some applications of COSE, it is useful to have a standard representation of CWT claims [RFC8392] available in the header parameters. These include encrypted COSE structures, which may or may not be an encrypted CWT and/or those featuring a detached signature. Section 5.3 of the JWT RFC [RFC7519] defined a similar mechanism for expressing selected JWT based claims as JOSE header parameters. This JWT feature was motivated by the desire to have certain claims, such as Key ID values, be visible to software processing the JWT, even though the JWT is encrypted. No corresponding feature was standardized for CWTs, which was an omission that this specification corrects. Directly including CWT claim values as COSE header parameter values would not work, since there are conflicts between the numeric header parameter assignments and the numeric CWT claim assignments. Instead, this specification defines a single header parameter registered in the IANA "COSE Header Parameters" registry that creates a location to store CWT claims in a COSE header parameter. Looker & Jones Expires 9 January 2023 [Page 2] Internet-Draft CBOR Web Token (CWT) Claims in COSE Head July 2022 2. Terminology 3. Representation This document defines the following COSE header parameter: +========+================+=======+============+===============+ | Name | Label | Value | Value | Description | | | | Type | Registry | | +========+================+=======+============+===============+ | cwt | TBD (requested | map | [IANA.CWT] | location for | | claims | assignment 11) | | | CWT claims in | | | | | | COSE headers | +--------+----------------+-------+------------+---------------+ Table 1 4. Privacy Considerations Some of the registered CWT claims may contain privacy-sensitive information. Therefore care must be taken when expressing CWT claims in COSE headers. 5. Security Considerations In cases where CWT claims are both present in the payload and the header, an application receiving such as structure MUST verify that their values are identical, unless the application defines other specific processing rules for these claims. 6. IANA Considerations IANA is requested to register the new COSE Header parameter in the table in Section 3 in the "COSE Header Parameters" registry [IANA.COSE]. 7. Normative References [IANA.COSE] IANA, "COSE Header Parameters", . [IANA.CWT] IANA, "CBOR Web Token (CWT) Claims", . 8. Informative References Looker & Jones Expires 9 January 2023 [Page 3] Internet-Draft CBOR Web Token (CWT) Claims in COSE Head July 2022 [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, . [RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, May 2018, . Appendix A. Document History -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 Tobias Looker Mattr Email: tobias.looker@mattr.global Michael B. Jones Microsoft Email: mbj@microsoft.com URI: https://self-issued.info/ Looker & Jones Expires 9 January 2023 [Page 4]