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Network Working Group                                   N. Sakimura, Ed.
Internet-Draft                                 Nomura Research Institute
Intended status: Standards Track                       December 12, 2012
Expires: June 15, 2013


                   JSON Metadata for OAuth Responses
                      draft-sakimura-oauth-meta-00

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 June 15, 2013.

Copyright Notice

   Copyright (c) 2012 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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   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



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   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  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  JSON Meta Object  . . . . . . . . . . . . . . . . . . . . . . . 3
     3.1.  _links Member . . . . . . . . . . . . . . . . . . . . . . . 4
       3.1.1.  href  . . . . . . . . . . . . . . . . . . . . . . . . . 4
       3.1.2.  method  . . . . . . . . . . . . . . . . . . . . . . . . 5
       3.1.3.  params  . . . . . . . . . . . . . . . . . . . . . . . . 5
       3.1.4.  content-type  . . . . . . . . . . . . . . . . . . . . . 5
       3.1.5.  Authorize . . . . . . . . . . . . . . . . . . . . . . . 5
   4.  Application to the OAuth 2.0 Token Endpoint References  . . . . 5
     4.1.  Successful Responses  . . . . . . . . . . . . . . . . . . . 5
       4.1.1.  self  . . . . . . . . . . . . . . . . . . . . . . . . . 6
       4.1.2.  describedby . . . . . . . . . . . . . . . . . . . . . . 6
       4.1.3.  Protected Resources . . . . . . . . . . . . . . . . . . 6
     4.2.  Error Responses . . . . . . . . . . . . . . . . . . . . . . 7
       4.2.1.  self  . . . . . . . . . . . . . . . . . . . . . . . . . 7
       4.2.2.  describedby . . . . . . . . . . . . . . . . . . . . . . 7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
     5.1.  Link Type Registration  . . . . . . . . . . . . . . . . . . 7
       5.1.1.  OAuth 2 Registrations . . . . . . . . . . . . . . . . . 7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
     6.1.  href tampering  . . . . . . . . . . . . . . . . . . . . . . 8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     8.2.  Informational References  . . . . . . . . . . . . . . . . . 9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 9

















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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

   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
   relationships ("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 the following.  (Note: line-wraps are for display
   purpose only.)



















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         {
           "_links":{
             "self":{"href":"https://example.com/token?code=123"},
             "http://openid.net/specs/connect/1.0/#userinfo_ep":[
               {
                 "href":"https://example.com/user/{user_id}",
                 "method":"GET",
                 "Authorize":"{token_type} {access_token}"
               },
               {
                 "href":"https://example.com/user/{user_id}",
                 "method":"POST",
                 "Authorize":"{token_type} {access_token}",
                 "params":[
                   "name","birthday"
                 ]
               }
           },
           "token_type":"Bearer",
           "access_token":"aCeSsToKen"
         }

   Here, we have "_links" member that expresses various "relations" such
   as "self" and "http://openid.net/specs/connect/1.0/#userinfo_ep".
   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 [RFC5988] or a URI that
   describes the relation.

   Each relation member holds exactly one object or one array, whose
   items 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.




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3.1.2.  method

   The value of the "method" member is the HTTP method defined in
   Hypertext Transfer Protocol -- HTTP/1.1 [RFC2616][RFC2616] that can
   be used to the URL described in the "href". e.g., GET, POST, PUT,
   DELETE.

3.1.3.  params

   The "params" member describes the parameters to be sent to the URL
   expressed in "href".  The "value" is an array of "pairs" whose string
   corresponds to the parameter names of the parameters that are to be
   sent to the URL.  The "value" of the "pair" is an "object" with
   following "members" .  All "members" are optional.

   required  Boolean. true of false.  Indicates whether this parameter
      is required to be sent with the request.

   description  Human readable description of the variable.

3.1.4.  content-type

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

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

3.1.5.  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.


4.  Application to the OAuth 2.0 Token Endpoint References

   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
   Section 3.1.




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4.1.1.  self

   An object with the following members.

   href  REQUIRED.  The URI that resulted in this response.

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",
      "http://tools.ietf.org/html/rfc6749#section-4.3.3",
      "http://tools.ietf.org/html/rfc6749#section-4.4.3".

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 section 3.1.1.  (Section 3.1.1).

   method  OPTIONAL.  HTTP request method to be used as described in
      section 3.1.2.  (Section 3.1.2).  Defaults to "GET".  Semantics of
      the HTTP methods in this case SHOULD map as follows: "GET" means
      reading the resource.  "POST" means creating or updating the
      resource with supplied parameters in "params" member below.
      "DELETE" means deleting the corresponding resource.  "PUT" means
      the complete replacement of the resource by the body of the
      request.  The resource MUST support "GET" method.  The support of
      other methods are OPTIONAL.

   params  OPTIONAL.  Parameters to be sent as described in section
      3.1.3.  (Section 3.1.3).

   content-type  OPTIONAL.  As described in section 3.1.4.
      (Section 3.1.4).

   Authorize  OPTIONAL.  HTTP Authorization header to be sent when
      accessing the resource.  This is described in section 3.1.5.
      (Section 3.1.5).  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.



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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.

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


5.  IANA Considerations

   This document makes no request of IANA.

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

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]





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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

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

   [todo]


8.  References

8.1.  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.

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

   [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.

   [RFC6750]  Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
              Framework: Bearer Token Usage", RFC 6750, October 2012.

8.2.  Informational References

   [HAL]      Kelly, M., "JSON Hypermedia API Language", 07 2012.

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


Author's Address

   Nat Sakimura (editor)
   Nomura Research Institute

   Email: sakimura@gmail.com






























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