OAuth Working Group                                             M. Kelly
Internet-Draft                                                 Stateless
Intended status: Standards Track                        N. Sakimura, Ed.
Expires: May 07, 2014                          Nomura Research Institute
                                                       November 03, 2013


                 JSON Metadata for OAuth Responses 1.0
                      draft-sakimura-oauth-meta-03

Abstract

   This specification defines an extensible metadata member that may be
   inserted into the OAuth 2.0 responses to assist the clients to
   process those responses.  It is expressed as a member called "_links"
   that is inserted as the top level member in the responses.  It will
   allow the client to learn where the members in the response could be
   used and how, etc.  Since it is just a member, any client that does
   not understand this extension should not break and work normally
   while supporting clients can utilize the metadata to its advantage.

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 http://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 May 07, 2014.

Copyright Notice

   Copyright (c) 2013 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
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   (http://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.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  JSON Meta Object  . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  _links Member . . . . . . . . . . . . . . . . . . . . . .   3
       3.1.1.  href  . . . . . . . . . . . . . . . . . . . . . . . .   4
       3.1.2.  Authorize . . . . . . . . . . . . . . . . . . . . . .   4
       3.1.3.  content-type  . . . . . . . . . . . . . . . . . . . .   4
   4.  Application to the OAuth 2.0 Token Endpoint Responses . . . .   4
     4.1.  Successful Responses  . . . . . . . . . . . . . . . . . .   4
       4.1.1.  self  . . . . . . . . . . . . . . . . . . . . . . . .   4
       4.1.2.  describedby . . . . . . . . . . . . . . . . . . . . .   5
       4.1.3.  Protected Resources . . . . . . . . . . . . . . . . .   5
     4.2.  Error Responses . . . . . . . . . . . . . . . . . . . . .   5
       4.2.1.  self  . . . . . . . . . . . . . . . . . . . . . . . .   5
       4.2.2.  describedby . . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Link Type Registration  . . . . . . . . . . . . . . . . .   6
       5.1.1.  OAuth 2 Registrations . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
     6.1.  href tampering  . . . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  Document History  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     9.2.  Informational References  . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Although OAuth 2.0 [RFC6749] has been known for its REST
   friendliness, OAuth itself is not RESTful, as it heavily relies on
   out-of-band information to drive the interactions.  This situation
   can be eased by hypertext-enabling the JSON responses through the
   introduction of a member that represents such hypertext and other
   metadata.  To achieve this, this specification introduces a top level
   member "_links" that represents various link relationships and other
   metadata.

2.  Requirements





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   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].

3.  JSON Meta Object

   A JSON Meta Object uses the format described in [RFC4627] and is
   intended to be inserted into a JSON document to express some of the
   metadata associated with it as "_links" member.

   The value of the "_links" member is a JSON object that expresses link
   relations ("rel"), which in turn holds an object with "href" and
   other members or an array of such objects.

   Following non-normative schematic example should help envisage what
   it would look like.  (Note: line-wraps are for display purpose only.)

      {
        "_links":{
          "self":{"href":"https://example.com/token?code=123"},
          "userinfo":
            {
              "href":"https://example.com/user/{user_id}",
              "Authorize":"{token_type} {access_token}"
            }
        },
        "token_type":"Bearer",
        "access_token":"aCeSsToKen"
      }


   Here, we have "_links" member that expresses various "relations" such
   as "self" and "userinfo", which is a resource type of OpenID
   Connect's Userinfo endpoint.  Each relationships has either a link
   relations object or an array of link relations objects as its value.
   The link relations objects holds various members such as "href".
   They are explained in the next section.

3.1.  _links Member

   "_links" member holds exactly one object that contains the following
   members with relation as the "string" defined in [RFC4627].  The
   "string" SHOULD be a link relation type that is either defined in the
   IANA registry defined in Web Linking (Web Linking) or a URI that
   describes the relation.






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   Each relation member holds exactly one object or one array, whose
   elements are objects.  Each object has following members, which are
   all optional.

3.1.1.  href

   The value of the "href" member is a URI Template [RFC6570] that the
   relation points to.  The values for template parameters SHOULD be
   taken from the value of the top-level members in the including JSON
   object whose "string" matches the template variable name.

3.1.2.  Authorize

   The HTTP Authorize header defined in Hypertext Transfer Protocol --
   HTTP/1.1 [RFC2616] to be used when accessing the resource identified
   by href.  It is templated in exactly the same syntax as in URI
   Template [RFC6570] except that it is applied to the Authorization
   request header than the URI.

3.1.3.  content-type

   The content-type to be used when the parameters are sent to the URL.

   [todo] Locate the proper reference and name for content transfer
   encodings.

   e.g., "application/x-www-form-urlencoded", "multipart/form-data",
   "application/json".

4.  Application to the OAuth 2.0 Token Endpoint Responses

   To create the Section 3 should be used in the token endpoint
   responses of the OAuth 2.0 Authorization Framework [RFC6749],
   following relations SHOULD be included.

4.1.  Successful Responses

   In the case of the Successful Response described in section 5.1. of
   [RFC6749], the following member SHOULD be present in the value of the
   "_links" member described in _links Member (Section 3.1) of this
   specification.

4.1.1.  self

   An object with the following members.

   href  REQUIRED.  The URI that resulted in this response.




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4.1.2.  describedby

   An object with the following members.

   href  REQUIRED.  The value is one of the following URIs: "http://
      tools.ietf.org/html/rfc6749#section-4.1.4" (Access Token Response
      of Authorization Code Grant), "http://tools.ietf.org/html/
      rfc6749#section-4.3.3" (Access Token Response of Resource Owner
      Password Credentials Grant), "http://tools.ietf.org/html/
      rfc6749#section-4.4.3" (Access Token Response of Client
      Credentials Grant ). [[editor's note.  Add Assertion Flows as
      well.]]

4.1.3.  Protected Resources

   Each protected resources MUST provide a unique Relation Name by
   either registering to the Link Relation Type Registry defined in
   section 6.2 of [RFC5988]or providing an absolute URI that provides a
   collision registant name.  The value is an array of objects that has
   the following members.

   href  REQUIRED.  The URI template that describes the request to the
      resource as described in href (Section 3.1.1).

   content-type  OPTIONAL.  As described in content-type
      (Section 3.1.3).

   Authorize  OPTIONAL.  HTTP Authorization header to be sent when
      accessing the resource.  This is described in Authorize
      (Section 3.1.2).  If this member is not available, then the client
      SHOULD access the expanded "href" value to obtain the
      Authorization header response to learn what authorization scheme
      it should use.

4.2.  Error Responses

   In the case of the Error Response described in section 5.2. of
   [RFC6749], the folloing member SHOULD be present.

4.2.1.  self

   An object with the following members.

   href  REQUIRED.  The URI that resulted in this response.

4.2.2.  describedby

   An object with the following members.



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   href  REQUIRED.  The value is "http://tools.ietf.org/html/
      rfc6749#section-5.2".

5.  IANA Considerations

5.1.  Link Type Registration

   Pursuant to [RFC5988], the following link type registrations [[will
   be]] registered by mail to link-relations@ietf.org.

5.1.1.  OAuth 2 Registrations

   The secition 3 of the OAuth 2.0 Authorization Framework [RFC6749]
   defines two endpoints that may be discovered through this
   specification.  These are the user Authorization Endpoint and the
   Token Endpoint.

5.1.1.1.  Authorization Endpoint

   o  Relation Name: oauth2-authorize

   o  Descritpion: An OAuth 2.0 Authorization Endpoint specified in
      section 3.1 of [RFC6749]

   o  Reference: [RFC6749]

5.1.1.2.  Token Endpoint

   o  Relation Name: oauth2-token

   o  Description: An OAuth 2.0 Token Endpoint specified in section 3.2
      of [RFC6749].

   o  Refeence: [RFC6749]

6.  Security Considerations

6.1.  href tampering

   Unless integrity protected channel is used, an attacker may be able
   to tamper the value of the href thereby causing the receiver of the
   JSON response to send a request to the URL under the attacker's
   control with potentially confidential information contained in the
   parameters.  To mitigate this risk, an integrity protected channel
   such as TLS protected channel should be used.

7.  Acknowledgements




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   This specification borrows heavily from [HAL].  The Link type
   registration is taken from [oauth-lrdd].

   [todo]

8.  Document History

   -02

   o  Added Mike Kelly as an author.

   o  xref fix.

   o  Introduced "operations" as in draft-ietf-scim-api-00#section-3.5.

   o  Updated the informative reference to HAL.

   o  Added description to OAuth Token Endpoint hrefs.

   o  Added content-type to the example.

   o  Added Area and Working Group.

   -01

   o  Some format changes, reference fix, and typo fixes.

   o  Changed 'items' to 'elements' to match the JSON terminology.

   -00

   o  Initial Draft

9.  References

9.1.  Normative References

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

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC5988]  Nottingham, M., "Web Linking", RFC 5988, October 2010.

   [RFC6570]  Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
              and D. Orchard, "URI Template", RFC 6570, March 2012.



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   [RFC6749]  Hardt, D., "The OAuth 2.0 Authorization Framework", RFC
              6749, October 2012.

9.2.  Informational References

   [HAL]      Kelly, M., "JSON Hypermedia API Language", February 2013.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

   [oauth-lrdd]
              Mills, W., "Link Type Registrations for OAuth 2", October
              2012.

Authors' Addresses

   Mike Kelly
   Stateless

   Email: mike@stateless.co


   Nat Sakimura (editor)
   Nomura Research Institute

   Email: sakimura@gmail.com

























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