Web Authentication Protocol
OAuth Working Group                                  T. Lodderstedt, Ed.
Internet-Draft                                       Deutsche Telekom AG
Intended status: Standards Track                               S. Dronia
Expires: November 27, 2012 April 9, 2013
                                                           M. Scurtescu
                                                            May 26,
                                                         October 6, 2012

                            Token Revocation


   This draft proposes an additional endpoint for OAuth authorization
   servers for revoking tokens.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Token Revocation  . . . . . . . . . . . . . . . . . . . . . . . 3
     2.1.  JSONP  Cross-Origin Support  . . . . . . . . . . . . . . . . . . . . . . . 5
   3.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6

1.  Introduction

   The OAuth 2.0 core specification [I-D.ietf-oauth-v2] defines several
   ways for a client to obtain refresh and access tokens.  This
   specification supplements the core specification with a mechanism to
   revoke both types of tokens.  A token is the external representation
   of an access grant issued by a resource owner to a particular client.
   A revocation request may discard the actual token as well as other
   tokens based on the same access grant and the access grant itself.

   This mechanism facilitates the following use cases:

   o  The end-user triggers revocation from within the client that sends
      the appropriate revocation request to the autorization server.
      From the end-user's perspective, this looks like a "logout" or
      "reset" function.
      The request causes the removal of the client
      permissions associated with client's access grant the
      particular token to access refers to.  From the end-user's protected resources. perspective, this
      looks like a "logout" or "reset" function.  This use case makes it
      even more comfortable to the end-user to revoke his access grant
      immediately via the client.

   o  In contrast to revocation by a client, the authorization server
      (or a related entity) may offer its end-users a self-care portal
      to delete access grants given to clients independent of any token
      storing devices.  Such a portal offers the possibility to an end-
      user to look at and revoke all access grants he once authorized.
      In cases the token storing device is not available, e.g. it is
      lost or stolen, revocation by a self-care portal is the only
      possibility to limit or avoid abuse.

   In the end, security, usability, and ease of use are increased by
   token revocation.

   By using an additional endpoint, the token revocation endpoint,
   clients can request the revocation of a particular token.  Compliant
   implementation MUST support the revocation of refresh tokens, access
   token revocation MAY be supported.

2.  Token Revocation

   The client requests the revocation of a particular token by making an
   HTTP POST request to the token revocation endpoint.  The location of
   the token revocation endpoint can be found in the authorization
   server's documentation.  The token endpoint URI MAY include a query

   Since requests to the token revocation endpoint result in the
   transmission of plain text credentials in the HTTP request, the
   authorization server MUST require the use of a transport-layer
   security mechanism when sending requests to the token revocation
   endpoints.  The authorization server MUST support TLS 1.0
   ([RFC2246]), SHOULD support TLS 1.2 ([RFC5246]) and its future
   replacements, and MAY support additional transport-layer mechanisms
   meeting its security requirements.

   The client constructs the request by including the following
   parameters using the "application/x-www-form-urlencoded" format in
   the HTTP request entity-body:

   token   REQUIRED.  The token that the client wants to get revoked.
           Note: the authorization server is supposed to detect the
           token type automatically.

   The client also includes its authentication credentials as described
   in Section 2.3. of [I-D.ietf-oauth-v2].

   For example, a client may request the revocation of a refresh token
   with the following request (line breaks are for display purposes

        POST /revoke HTTP/1.1
        Host: server.example.com
        Content-Type: application/x-www-form-urlencoded
        Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW


   The authorization server first validates the client credentials (if
   present) (in
   case of a confidential client) and verifies whether the client is
   authorized to revoke the particular token based on the client
   identity and its policy.  For example, only the client the token has
   been issued for might be allowed to revoke it.  It is also
   conceivable to allow a dedicated user self-care portal to revoke all
   kinds of tokens.

   In the next step, the authorization server invalidates the token. token and
   the respective access grant.  If the particular token is a refresh
   token and the authorization server supports the revocation of access
   tokens, then the authorization server SHOULD also invalidate all
   access tokens based on the same access grant.

   Whether the revocation takes effect instantly or with some delay
   depends on the architecture of the particular deployment.  The client
   MUST NOT make any assumptions about the timing and MUST NOT use the
   token again.

   If the processed token is a refresh token and the authorization
   server supports the revocation of access tokens, then the
   authorization server SHOULD also invalidate all access tokens issued
   for that refresh token.

   The authorization server indicates a successful processing of the
   request by a HTTP status code 200.  Status code 401 indicates a
   failed client authentication, whereas a status code 403 is used if
   the client is not authorized to revoke the particular token.  For all
   other error conditions, a status code 400 is used along with an error
   response as defined in section 5.2. of [I-D.ietf-oauth-v2].  The
   following error codes are defined for the token revocation endpoint:

   unsupported_token_type  The authorization server does not support the
           revocation of the presented token type.  I.e. the client
           tried to revoke an access token on a server not supporting
           this feature.

   invalid_token  The presented token is invalid.

2.1.  JSONP  Cross-Origin Support

   The revocation endpoint MAY revokation end-point SHOULD support CORS [W3C.WD-cors-20120403]
   if it is aimed at use in combination with user-agent-based
   applications.  In addition, for interoperability with legacy user-
   agents, it MAY offer JSONP [jsonp] by allowing GET requests with an
   additional parameter:

   callback  The qualified name of a JavaScript function.

   Example request:


   Successful response:


   Error response:


   Clients should be aware that when relying on JSONP, a malicious
   revokation end-point may attempt to inject malicious code into the

3.  Acknowledgements

   We would like to thank Michiel de Jong, Doug Foiles, Paul Madsen,
   George Fletcher, Sebastian Ebling, Christian Stuebner, Brian
   Campbell, Igor Faynberg, Lukas Rosenstock, and Justin P. Richer for
   their valuable feedback.

4.  IANA Considerations

   This draft includes no request to IANA.

5.  Security Considerations

   All relevant security considerations have been given in the
   functional specification.

6.  References

6.1.  Normative References

              Hammer-Lahav, E., Recordon, D., and D.
              Hardt, D., "The OAuth 2.0 Authorization Framework", draft-ietf-oauth-v2-26
              draft-ietf-oauth-v2-31 (work in progress), May August 2012.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, January 1999.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

6.2.  Informative References

              Kesteren, A., "Cross-Origin Resource Sharing", World Wide
              Web Consortium LastCall WD-cors-20120403, April 2012,

   [jsonp]    Ippolito, B., "Remote JSON - JSONP", December 2005.

Authors' Addresses

   Torsten Lodderstedt (editor)
   Deutsche Telekom AG

   Email: torsten@lodderstedt.net
   Stefanie Dronia

   Email: sdronia@gmx.de

   Marius Scurtescu

   Email: mscurtescu@google.com