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Network Working Group                                    J. Bradley, Ed.
Internet-Draft                                                    Yubico
Intended status: Experimental                                  J. Richer
Expires: July 11, 2018                                  January 07, 2018


                Stateless Client Identifier for OAuth 2
               draft-bradley-oauth-stateless-client-id-05

Abstract

   This draft provides a method for communicating information about an
   OAuth client through its client identifier allowing for fully
   stateless operation.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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 July 11, 2018.

Copyright Notice

   Copyright (c) 2018 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



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Stateless Client Identifier . . . . . . . . . . . . . . . . .   2
   3.  Validating the Stateless Client Identifier  . . . . . . . . .   3
   4.  Obtaining a Stateless Client Identifier . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Appendix A.  Document History . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   In the OAuth 2.0 Authorization protocol, the Client must provide a
   Client Identifier that the Authorization Server recognizes.
   Additionally, an Autorization Server needs to know about a client's
   details, such as its name and redirect URIs.  Traditionally, this is
   handled through a registration process, which may be either manual or
   automated, where the authorization server maintains a stateful
   relationship between the Client Identifier and its associated
   metadata.  This draft proposes a mechanism whereby the essential
   metadata can be encoded into the Client Identifier itself, signed by
   the issuer, and validated by the authorization server, thus allowing
   the authorization server to be stateless in regard to client
   information.

2.  Stateless Client Identifier

   The stateless client identifier consists of a JWT [RFC7519],
   optionally signed with JWS [RFC7515], whose payload contains claims
   as defined here.

   iss  REQUIRED.  URL identifying the party that issued this client
      identifier.

   sub  REQUIRED.  Identifier of the client, locally unique to the
      issuer.

   iat  OPTIONAL.  Timestamp of when this client identifier was issued.

   exp  OPTIONAL.  Timestamp of when this client identifier will expire.



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   kid  RECOMMENDED if signed.  Identifier of the key used to sign this
      client identifier at the issuer.

   reg  REQUIRED.  JSON Object containing a set of metadata claims of
      client information such as its redirect URIs, display name, and
      other items as defined in Dynamic Client Registration [RFC7591]
      and its extensions.

   The issuer SHOULD sign the JWT with JWS in such a way that the
   signature can be verified by the authorization server.

   The issuer MAY encrypt the JWT with JWE [RFC7516].

3.  Validating the Stateless Client Identifier

   Upon receiving a stateless client identifier at either the
   authorization endpoint or the token endpoint, the authorization
   server parses it as a JWT.  It first checks the iss field to
   determine if it trusts identifiers issued by the party represented.
   It then verifies the signature if the JWT (if signed) using JWS.  The
   key used to sign the JWT MAY be indicated by the kid field.  The
   authorization server MAY use other means to validate the JWT and
   determine its authenticity.

   The authorization server then reads the fields inside the reg claim
   and uses these to configure the user experience and security
   parameters of the authorization.

4.  Obtaining a Stateless Client Identifier

   The client identifier is intended to be opaque to the client, and as
   such a stateless client identifier is intended to be obtained and
   used in exactly the same way as a stateful client identifer would be
   for any OAuth client.

   o  Manual registration: a developer uses an out-of-band adminstrative
      process to generate the client identifier and related credentials.

   o  Dynamic registration: a developer or client uses the process
      described in [Dyn Reg] to generate the client identifier and
      related credentials.

   o  Self assertion: a developer or client generates the client
      identifier on their own, often signing it with their own public
      key.






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   It is completely up to the purview of particular authorization
   servers which generation methods, and which client identifiers, they
   will accept.

5.  IANA Considerations

   [ maybe we register the "reg" claim above? ]

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

6.  Security Considerations

   Since many OAuth systems assume that a change in the client
   identifier indicates a change in the client itself, systems using
   stateless client identifiers SHOULD NOT allow clients to update their
   information post registration.

   Since the client identifier is passed through the browser to the
   authorization endpoint, it MUST NOT contain any sensitive
   information.  Additionally, as in standard OAuth, posession of the
   client identifier itself MUST NOT be assumed to be sufficient
   authentication [in many cases? except implicit mode?].

7.  Acknowledgements

8.  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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <https://www.rfc-editor.org/info/rfc7515>.

   [RFC7516]  Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
              RFC 7516, DOI 10.17487/RFC7516, May 2015,
              <https://www.rfc-editor.org/info/rfc7516>.

   [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/info/rfc7519>.





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   [RFC7591]  Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
              P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
              RFC 7591, DOI 10.17487/RFC7591, July 2015,
              <https://www.rfc-editor.org/info/rfc7591>.

Appendix A.  Document History

   [[ to be removed by the RFC Editor before publication as an RFC ]]

   -02

   o  Added reference to RFC7591

   -01

   o  Added reference to RFC for JOSE

   -00

   o  Wrote the first draft.

Authors' Addresses

   John Bradley (editor)
   Yubico

   Email: ve7jtb@ve7jtb.com
   URI:   http://www.thread-safe.com/


   Justin Richer




















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