Web Authorization Protocol O. Chalk Internet-Draft Government Digital Service, UK Intended status: Standards Track 15 November 2025 Expires: 19 May 2026 OAuth Tokens in HTTP Header draft-chalk-oauth-tokens-in-header-latest Abstract This specification extends OAuth 2.0 [RFC6749] by defining a mechanism for resource servers or authorisation servers to convey inline token updates and related metadata to clients using the Authentication-Info HTTP header. About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://OllieJC.github.io/draft-chalk-oauth-tokens-in-header/draft- chalk-oauth-tokens-in-header.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft- chalk-oauth-tokens-in-header/. Discussion of this document takes place on the Web Authorization Protocol Working Group mailing list (mailto:oauth@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/oauth/. Subscribe at https://www.ietf.org/mailman/listinfo/oauth/. Source for this draft and an issue tracker can be found at https://github.com/OllieJC/draft-chalk-oauth-tokens-in-header. 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 19 May 2026. Copyright Notice Copyright (c) 2025 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 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. Conventions and Definitions 3. Security Considerations 4. IANA Considerations 5. Normative References Acknowledgments Author's Address 1. Introduction OAuth deployments range from simple bearer-only configurations to complex ecosystems with distinct authorisation and resource servers. In some scenarios a resource server holds enough contextual information to advise the client of a refreshed or more suitable token for future use. Existing OAuth flows, however, obligate the client to perform a separate interaction with the authorisation server to obtain such updates, and certain deployments may lack an authorisation server altogether. This document defines a lightweight mechanism that leverages the Authentication-Info header (originally specified in [RFC7615] and incorporated into [RFC9110]) to convey inline token updates and associated metadata within a normal HTTP response. The header can be processed transparently by HTTP implementations, potentially even at a proxy or edge service, and does not alter the client's request semantics. Recipients treat the conveyed values as hints - they may adopt the suggested token but are not required to do so - thereby preserving compatibility with existing OAuth behaviour while offering an optional optimisation for efficiency and flexibility. 2. Conventions and Definitions 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. 3. Security Considerations TODO Security 4. IANA Considerations This document has no IANA actions. 5. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012, . [RFC7615] Reschke, J., "HTTP Authentication-Info and Proxy- Authentication-Info Response Header Fields", RFC 7615, DOI 10.17487/RFC7615, September 2015, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, Ed., "HTTP Semantics", STD 97, RFC 9110, DOI 10.17487/RFC9110, June 2022, . Acknowledgments TODO acknowledge. Author's Address Ollie Chalk Government Digital Service, UK Email: ollie.chalk@dsit.gov.uk