Network Working Group                                           M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                                D. Hardt
Expires: October 2, November 22, 2011                                   independent
                                                             D. Recordon
                                                          March 31,
                                                            May 21, 2011

                 The OAuth 2.0 Protocol: Bearer Tokens


   This specification describes how to use bearer tokens when accessing
   OAuth 2.0 protected resources.

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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   This Internet-Draft will expire on October 2, November 22, 2011.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  3
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
     1.3.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Authenticated Requests . . . . . . . . . . . . . . . . . . . .  4
     2.1.  The Authorization Request Header Field . . . . . . . . . .  5
     2.2.  Form-Encoded Body Parameter  . . . . . . . . . . . . . . .  5
     2.3.  URI Query Parameter  . . . . . . . . . . . . . . . . . . .  6
     2.4.  The WWW-Authenticate Response Header Field . . . . . . . .  7
       2.4.1.  Error Codes  . . . . . . . . . . . . . . . . . . . . .  8
   3.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
     3.1.  Security Threats . . . . . . . . . . . . . . . . . . . . .  9
     3.2.  Threat Mitigation  . . . . . . . . . . . . . . . . . . . .  9
     3.3.  Summary of Recommendations . . . . . . . . . . . . . . . . 11
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
     4.1.  OAuth Access Token Type Registration . . . . . . . . . . . 11
       4.1.1.  The "Bearer" OAuth Access Token Type . . . . . . . . . 12
     4.2.  The OAuth Errors Registry  . . . . . . . . . . . . . . . . 12
       4.2.1.  Registration Template  . . . . . . . . . . . . . . . . 12
       4.2.2.  Initial Registry Contents  . . . . . . . . . . . . . . 13
   5.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 12
     5.1.  Normative References . . . . . . . . . . . . . . . . . . . 14 12
     5.2.  Informative References . . . . . . . . . . . . . . . . . . 15 13
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 15 13
   Appendix B.  Document History  . . . . . . . . . . . . . . . . . . 15 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 16

1.  Introduction

   OAuth enables clients to access protected resources by obtaining an
   access token, which is defined in [I-D.ietf-oauth-v2] as "a string
   representing an access authorization issued to the client", rather
   than using the resource owner's credentials.

   Tokens are issued to clients by an authorization server with the
   approval of the resource owner.  The client uses the access token to
   access the protected resources hosted by the resource server.  This
   specification describes how to make protected resource requests when
   the OAuth access token is a bearer token.

   This specification defines the use of bearer tokens with OAuth over
   HTTP [RFC2616] using TLS [RFC5246].  Other specifications may extend
   it for use with other transport protocols.

1.1.  Notational Conventions

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

   This document uses the Augmented Backus-Naur Form (ABNF) notation of
   [I-D.ietf-httpbis-p1-messaging], which is based upon the Augmented
   Backus-Naur Form (ABNF) notation of [RFC5234].  Additionally, the
   following rules are included from [RFC2617]: auth-param and realm;
   from [RFC3986]: URI-Reference; and from
   [I-D.ietf-httpbis-p1-messaging]: RWS and quoted-string.

   Unless otherwise noted, all the protocol parameter names and values
   are case sensitive.

1.2.  Terminology

   Bearer Token
      A security token with the property that any party in possession of
      the token (a "bearer") can use the token in any way that any other
      party in possession of it can.  Using a bearer token does not
      require a bearer to prove possession of cryptographic key material

   All other terms are as defined in [I-D.ietf-oauth-v2].

1.3.  Overview

   OAuth provides a method for clients to access a protected resource on
   behalf of a resource owner.  Before a client can access a protected
   resource, it must first obtain authorization (access grant) from the
   resource owner and then exchange the access grant for an access token
   (representing the grant's scope, duration, and other attributes).
   The client accesses the protected resource by presenting the access
   token to the resource server.

   The access token provides an abstraction layer, replacing different
   authorization constructs (e.g. username and password, assertion) for
   a single token understood by the resource server.  This abstraction
   enables issuing access tokens valid for a short time period, as well
   as removing the resource server's need to understand a wide range of
   authentication schemes.

   +--------+                               +---------------+
   |        |--(A)- Authorization Request ->|   Resource    |
   |        |                               |     Owner     |
   |        |<-(B)----- Access Grant -------|               |
   |        |                               +---------------+
   |        |
   |        |           Access Grant &      +---------------+
   |        |--(C)--- Client Credentials -->| Authorization |
   | Client |                               |     Server    |
   |        |<-(D)----- Access Token -------|               |
   |        |                               +---------------+
   |        |
   |        |                               +---------------+
   |        |--(E)----- Access Token ------>|    Resource   |
   |        |                               |     Server    |
   |        |<-(F)--- Protected Resource ---|               |
   +--------+                               +---------------+

                     Figure 1: Abstract Protocol Flow

   The abstract flow illustrated in Figure 1 describes the overall OAuth
   2.0 protocol architecture.  The following steps are specified within
   this document:

      E) The client makes a protected resource request to the resource
      server by presenting the access token.

      F) The resource server validates the access token, and if valid,
      serves the request.

2.  Authenticated Requests

   Clients SHOULD make authenticated requests with a bearer token using
   the "Authorization" request header field defined by [RFC2617].

   Resource servers MUST accept authenticated requests using the
   "Bearer" HTTP authorization scheme as described in Section 2.1, and
   MAY support additional methods.

   Alternatively, clients MAY transmit the access token in the HTTP body
   when using the "application/x-www-form-urlencoded" content type as
   described in Section 2.2; or clients MAY transmit the access token in
   the HTTP request URI in the query component as described in
   Section 2.3.  Resource servers MAY support these alternative methods.

   Clients SHOULD NOT use the request body or URI unless the
   "Authorization" request header field is not available, and MUST NOT
   use more than one method to transmit the token in each request.
   Because of the Security Considerations (Section 3) associated with
   the URI method, it SHOULD NOT be used unless no other method is

2.1.  The Authorization Request Header Field

   The "Authorization" request header field is used by clients to make
   authenticated requests with bearer tokens.  The client uses the
   "Bearer" authentication scheme to transmit the access token in the

   For example:

   GET /resource HTTP/1.1
   Authorization: Bearer vF9dft4qmT

   The "Authorization" header field uses the framework defined by
   [RFC2617] as follows:

   credentials     = "Bearer" RWS access-token
   access-token    = 1*( quoted-char / <"> )

   quoted-char     = ALPHA / DIGIT /
                     "!" / "#" / "$" / "%" / "&" / "'" / "(" / ")" /
                     "*" / "+" / "-" / "." / "/" / DIGIT
                    / ":" / "<" / "=" /
                     ">" / "?" / "@" / ALPHA
                    / "[" / "]" / "^" / "_" / "`" /
                     "{" / "|" / "}" / "~" / "\" / "," / ";"

2.2.  Form-Encoded Body Parameter

   When including the access token in the HTTP request entity-body, the
   client adds the access token to the request body using the
   "bearer_token" parameter.  The client MUST NOT use this method unless
   the following conditions are met:

   o  The HTTP request entity-body is single-part.

   o  The entity-body follows the encoding requirements of the
      "application/x-www-form-urlencoded" content-type as defined by

   o  The HTTP request entity-header includes the "Content-Type" header
      field set to "application/x-www-form-urlencoded".

   o  The HTTP request method is one for which a body is permitted to be
      present in the request.  In particular, this means that the "GET"
      method MUST NOT be used.

   The entity-body can include other request-specific parameters, in
   which case, the "bearer_token" parameter MUST be properly separated
   from the request-specific parameters by an "&" character (ASCII code

   For example, the client makes the following HTTP request using
   transport-layer security:

   POST /resource HTTP/1.1
   Content-Type: application/x-www-form-urlencoded


   The "application/x-www-form-urlencoded" method SHOULD NOT be used
   except in application contexts where participating browsers do not
   have access to the "Authorization" request header field.

2.3.  URI Query Parameter

   When including the access token in the HTTP request URI, the client
   adds the access token to the request URI query component as defined
   by [RFC3986] using the "bearer_token" parameter.

   For example, the client makes the following HTTP request using
   transport-layer security:

   GET /resource?bearer_token=vF9dft4qmT HTTP/1.1

   The HTTP request URI query can include other request-specific
   parameters, in which case, the "bearer_token" parameter MUST be
   properly separated from the request-specific parameters by an "&"
   character (ASCII code 38).

   For example:

   Because of the Security Considerations (Section 3) associated with
   the URI method, it SHOULD NOT be used unless no other method is

2.4.  The WWW-Authenticate Response Header Field

   If the protected resource request does not include authentication
   credentials or contains an invalid access token, the resource server
   MUST include the HTTP "WWW-Authenticate" response header field; it
   MAY include it in response to other conditions as well.  The
   "WWW-Authenticate" header field uses the framework defined by
   [RFC2617] as follows:

   challenge       = "Bearer" [ RWS 1#param ]

   param           = realm / scope /
                     error / error-desc / error-uri /
                     ( token "=" ( token / quoted-string ) )

   scope           = "scope" "=" <"> scope-v *( SP scope-v ) <">
   scope-v         = 1*quoted-char

   quoted-char     = ALPHA / DIGIT /
                     "!" / "#" / "$" / "%" / "&" / "'" / "(" / ")" /
                     "*" / "+" / "-" / "." / "/" / ":" / "<" / "=" /
                     ">" / "?" / "@" / "[" / "]" / "^" / "_" / "`" /
                     "{" / "|" / "}" / "~" / "\" / "," / ";"

   error           = "error" "=" quoted-string
   error-desc      = "error_description" "=" quoted-string
   error-uri       = "error_uri" = "=" <"> URI-reference <">

   The "scope" attribute is a space-delimited list of scope values
   indicating the required scope of the access token for accessing the
   requested resource.  The "scope" attribute MUST NOT appear more than

   If the protected resource request included an access token and failed
   authentication, the resource server SHOULD include the "error"
   attribute to provide the client with the reason why the access
   request was declined.  The parameter value is described in
   Section 2.4.1.  In addition, the resource server MAY include the
   "error_description" attribute to provide a human-readable
   explanation, and the "error_uri" attribute with an absolute URI
   identifying a human-readable web page explaining the error.  The
   "error", "error_description", and "error_uri" attribute MUST NOT
   appear more than once. [[ add language and encoding information to
   error_description if the core specification does ]]

   For example, in response to a protected resource request without

   HTTP/1.1 401 Unauthorized
   WWW-Authenticate: Bearer realm="example"

   And in response to a protected resource request with an
   authentication attempt using an expired access token:

   HTTP/1.1 401 Unauthorized
   WWW-Authenticate: Bearer realm="example"
                     error_description="The access token expired"

2.4.1.  Error Codes

   When a request fails, the resource server responds using the
   appropriate HTTP status code (typically, 400, 401, or 403), and
   includes one of the following error codes in the response:

         The request is missing a required parameter, includes an
         unsupported parameter or parameter value, repeats the same
         parameter, uses more than one method for including an access
         token, or is otherwise malformed.  The resource server SHOULD
         respond with the HTTP 400 (Bad Request) 401 (Unauthorized) status code.

         The access token provided is expired, revoked, malformed, or
         invalid for other reasons.  The resource SHOULD respond with
         the HTTP 401 (Unauthorized) status code.  The client MAY
         request a new access token and retry the protected resource

         The request requires higher privileges than provided by the
         access token.  The resource server SHOULD respond with the HTTP
         403 (Forbidden) status code and MAY include the "scope"
         attribute with the scope necessary to access the protected

   New errors MUST be separately registered in the OAuth Errors registry
   as described by Section 4.2.

   If the request lacks any authentication information (i.e. the client
   was unaware authentication is necessary or attempted using an
   unsupported authentication method), the resource server SHOULD NOT
   include an error code or other error information.

   For example:

   HTTP/1.1 401 Unauthorized
   WWW-Authenticate: Bearer realm="example"

3.  Security Considerations

   This section describes the relevant security threats regarding token
   handling when using bearer tokens and describes how to mitigate these

3.1.  Security Threats

   The following list presents several common threats against protocols
   utilizing some form of tokens.  This list of threats is based on NIST
   Special Publication 800-63 [NIST800-63].  Since this document builds
   on the OAuth 2.0 specification, we exclude a discussion of threats
   that are described there or in related documents.

   Token manufacture/modification:  An attacker may generate a bogus
      token or modify the token contents (such as the authentication or
      attribute statements) of an existing token, causing the resource
      server to grant inappropriate access to the client.  For example,
      an attacker may modify the token to extend the validity period; a
      malicious client may modify the assertion to gain access to
      information that they should not be able to view.

   Token disclosure:  Tokens may contain authentication and attribute
      statements that include sensitive information.

   Token redirect:  An attacker uses the token generated for consumption
      by resource server to obtain access to another resource server.

   Token replay:  An attacker attempts to use a token that has already
      been used with that resource server in the past.

3.2.  Threat Mitigation

   A large range of threats can be mitigated by protecting the contents
   of the token by using a digital signature or a Message Authentication
   Code (MAC).  Alternatively, a bearer token can contain a reference to
   authorization information, rather than encoding the information
   directly.  Such references MUST be infeasible for an attacker to
   guess; using a reference may require an extra interaction between a
   server and the token issuer to resolve the reference to the
   authorization information.

   This document does not specify the encoding or the contents of the
   token; hence detailed recommendations for token integrity protection
   are outside the scope of this document.  We assume that the token
   integrity protection is sufficient to prevent the token from being

   To deal with token redirect, it is important for the authorization
   server to include the identity of the intended recipients, namely recipients (the
   audience), typically a single resource server (or a list of resource servers).
   servers), in the token.  Restricting the use of the token to a
   specific scope is also recommended.

   To provide protection against token disclosure, confidentiality
   protection is applied via TLS [RFC5246] with a ciphersuite that
   offers confidentiality protection.  This requires that the
   communication interaction between the client and the authorization
   server, as well as the interaction between the client and the
   resource server, utilize confidentiality protection.  Since TLS is
   mandatory to implement and to use with this specification, it is the
   preferred approach for preventing token disclosure via the
   communication channel.  For those cases where the client is prevented
   from observing the contents of the token, token encryption has to be
   applied in addition to the usage of TLS protection.

   To deal with token capture and replay, the following recommendations
   are made: First, the lifetime of the token has to be limited by
   putting a validity time field inside the protected part of the token.
   Note that using short-lived (one hour or less) tokens significantly
   reduces the impact of one of them being leaked.  Second,
   confidentiality protection of the exchanges between the client and
   the authorization server and between the client and the resource
   server MUST be applied, for instance, through the use of TLS
   [RFC5246].  As a consequence, no eavesdropper along the communication
   path is able to observe the token exchange.  Consequently, such an
   on-path adversary cannot replay the token.  Furthermore, when
   presenting the token to a resource server, the client MUST verify the
   identity of that resource server, as per [RFC2818].  Note that the
   client MUST validate the TLS certificate chain when making these
   requests to protected resources.  Presenting the token to an
   unauthenticated and unauthorized resource server or failing to
   validate the certificate chain will allow adversaries to steal the
   token and gain unauthorized access to protected resources.

3.3.  Summary of Recommendations

   Safeguard bearer tokens  Client implementations MUST ensure that
      bearer tokens are not leaked to unintended parties, as they will
      be able to use them to gain access to protected resources.  This
      is the primary security consideration when using bearer tokens and
      underlies all the more specific recommendations that follow.

   Validate SSL certificate chains  The client must validate the TLS
      certificate chain when making requests to protected resources.
      Failing to do so may enable DNS hijacking attacks to steal the
      token and gain unintended access.

   Always use TLS (https)  Clients MUST always use TLS [RFC5246] (https)
      when making requests with bearer tokens.  Failing to do so exposes
      the token to numerous attacks that could give attackers unintended

   Don't store bearer tokens in cookies  Implementations MUST NOT store
      bearer tokens within cookies that can be sent in the clear (which
      is the default transmission mode for cookies).

   Issue short-lived bearer tokens  Using short-lived (one hour or less)
      bearer tokens can reduce the impact of one of them being leaked.
      In particular, only short-lived bearer tokens should be issued to
      clients that run within a web browser or other environments where
      information leakage may occur.

   Issue scoped bearer tokens  Issue bearer tokens that contain an
      audience restriction, scoping their use to the intended relying
      party or set of relying parties.

   Don't pass bearer tokens in page URLs  Browsers, web servers, and
      other software may not adequately secure URLs in the browser
      history, web server logs, and other data structures.  If bearer
      tokens are passed in page URLs (typically as query string
      parameters), attackers might be able to steal them from the
      history data, logs, or other unsecured locations.  Instead, pass
      bearer tokens in HTTP message headers or message bodies for which
      confidentiality measures are taken.

4.  IANA Considerations

4.1.  OAuth Access Token Type Registration

   This specification registers the following access token type in the
   OAuth Access Token Type Registry.

4.1.1.  The "Bearer" OAuth Access Token Type

   Type name:

   Additional Token Endpoint Response Parameters:

   HTTP Authentication Scheme(s):

   Change controller:

   Specification document(s):
      [[ this document ]]

4.2.  The OAuth Errors Registry

   This specification establishes the OAuth Errors registry.

   Additional errors for inclusion in the authorization endpoint
   response, the token endpoint response, or the resource endpoint
   response are registered on the advice of one or more Designated
   Experts (appointed by the IESG or their delegate), with a
   Specification Required (using terminology from [RFC5226]).  However,
   to allow for the allocation of values prior to publication, the
   Designated Expert(s) may approve registration once they are satisfied
   that such a specification will be published.

   Registration requests should be sent to the [TBD] mailing
   list for review and comment, with an appropriate subject (e.g.,
   "Request for error: example"). [[ Note to RFC-EDITOR: The name of the
   mailing list should be determined in consultation with the IESG and
   IANA.  Suggested name: oauth-ext-review. ]]

   Before a period of 14 days has passed, the Designated Expert(s) will
   either approve or deny the registration request, communicating this
   decision both to the review list and to IANA.  Denials should include
   an explanation and, if applicable, suggestions as to how to make the
   request successful.  Registration requests that are undetermined for
   a period longer than 21 days can be brought to the IESG's attention
   (using the mailing list) for resolution.

4.2.1.  Registration Template
   Error name:
      The name requested (e.g., "example").

   Error usage location:
      The location(s) where the error can be used.  The possible
      locations are: authorization response, token response, resource

   Change controller:
      For standards-track RFCs, state "IETF".  For others, give the name
      of the responsible party.  Other details (e.g., postal address,
      e-mail address, home page URI) may also be included.

   Specification document(s):
      Reference to document that specifies the error, preferably
      including a URI that can be used to retrieve a copy of the
      document.  An indication of the relevant sections may also be
      included, but is not required.

4.2.2.  Initial Registry Contents

   The OAuth Errors Registry's initial contents are:

   o  Error name: invalid_request

   o  Error usage location: resource response

   o  Change controller: IETF

   o  Specification document(s): [[ this document ]]

   o  Error name: invalid_token

   o  Error usage location: resource response

   o  Change controller: IETF

   o  Specification document(s): [[ this document ]]

   o  Error name: insufficient_scope

   o  Error usage location: resource response

   o  Change controller: IETF

   o  Specification document(s): [[ this document ]]

5.  References

5.1.  Normative References

              Fielding, R., Gettys, J., Mogul, J., Nielsen, H.,
              Masinter, L., Leach, P., Berners-Lee, T., and J. Reschke,
              "HTTP/1.1, part 1: URIs, Connections, and Message
              Parsing", draft-ietf-httpbis-p1-messaging-13 draft-ietf-httpbis-p1-messaging-14 (work in
              progress), March April 2011.

              Hammer-Lahav, E., Recordon, D., and D. Hardt, "The OAuth
              2.0 Authorization Protocol", draft-ietf-oauth-v2-13 draft-ietf-oauth-v2-16 (work
              in progress), February May 2011.

   [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.

   [RFC2617]  Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
              Leach, P., Luotonen, A., and L. Stewart, "HTTP
              Authentication: Basic and Digest Access Authentication",
              RFC 2617, June 1999.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC5226]  Narten, T.

   [RFC5234]  Crocker, D. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5226,
              May 5234, January 2008.

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

              Raggett, D.,
              Hors, A., and I. Jacobs, I., and D. Raggett, "HTML 4.01
              Specification", World Wide Web Consortium
              Recommendation REC-html401-19991224, December 1999,

5.2.  Informative References

              Fielding, R., Gettys, J., Mogul, J., Nielsen, H.,
              Masinter, L., Leach, P., Berners-Lee, T., and J. Reschke,
              "HTTP/1.1, part 7: Authentication",
              draft-ietf-httpbis-p7-auth-13 (work in progress),
              March 2011.

              Burr, W., Dodson, D., Perlner, R., Polk, T., Gupta, S.,
              and E. Nabbus, "NIST Special Publication 800-63-1,
              INFORMATION SECURITY", December 2008.

Appendix A.  Acknowledgements

   The following people contributed to preliminary versions of this
   document: Blaine Cook (BT), Brian Eaton (Google), Yaron Goland
   (Microsoft), Brent Goldman (Facebook), Raffi Krikorian (Twitter),
   Luke Shepard (Facebook), and Allen Tom (Yahoo!).  The content and
   concepts within are a product of the OAuth community, the WRAP
   community, and the OAuth Working Group.

   The OAuth Working Group has dozens of very active contributors who
   proposed ideas and wording for this document, including: Michael
   Adams, Andrew Arnott, Dirk Balfanz, Brian Campbell, Leah Culver, Bill
   de hOra, Brian Ellin, Igor Faynberg, George Fletcher, Tim Freeman,
   Evan Gilbert, Justin Hart, John Kemp, Eran Hammer-Lahav, Chasen Le
   Hara, Michael B. Jones, Torsten Lodderstedt, Eve Maler, James Manger,
   Laurence Miao, Chuck Mortimore, Anthony Nadalin, Justin Richer, Peter
   Saint-Andre, Nat Sakimura, Rob Sayre, Marius Scurtescu, Naitik Shah,
   Justin Smith, Jeremy Suriel, Christian Stuebner, Paul Tarjan, and
   Franklin Tse.

Appendix B.  Document History

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


   o  Removed OAuth Errors Registry, per design team input.

   o  Changed HTTP status code for "invalid_request" error code from
      HTTP 400 (Bad Request) to HTTP 401 (Unauthorized) to match HTTP
      usage [[ change pending working group consensus ]].

   o  Added missing quotation marks in error-uri definition.

   o  Added note to add language and encoding information to
      error_description if the core specification does.

   o  Explicitly reference the Augmented Backus-Naur Form (ABNF) defined
      in [RFC5234].

   o  Use auth-param instead of repeating its definition, which is (
      token "=" ( token / quoted-string ) ).

   o  Clarify security considerations about including an audience
      restriction in the token and include a recommendation to issue
      scoped bearer tokens in the summary of recommendations.


   o  Edits responding to working group last call feedback on -03.
      Specific edits enumerated below.

   o  Added Bearer Token definition in Terminology section.

   o  Changed parameter name "oauth_token" to "bearer_token".

   o  Added realm parameter to "WWW-Authenticate" response to comply
      with [RFC2617].

   o  Removed "[ RWS 1#auth-param ]" from "credentials" definition since
      it did not comply with the ABNF in [I-D.ietf-httpbis-p7-auth].

   o  Removed restriction that the "bearer_token" (formerly
      "oauth_token") parameter be the last parameter in the entity-body
      and the HTTP request URI query.

   o  Do not require WWW-Authenticate Response in a reply to a malformed
      request, as an HTTP 400 Bad Request response without a WWW-
      Authenticate header is likely the right response in some cases of
      malformed requests.

   o  Removed OAuth Parameters registry extension.

   o  Numerous editorial improvements suggested by working group


   o  Restored the WWW-Authenticate response header functionality
      deleted from the framework specification in draft 12 based upon
      the specification text from draft 11.

   o  Augmented the OAuth Parameters registry by adding two additional
      parameter usage locations: "resource request" and "resource

   o  Registered the "oauth_token" OAuth parameter with usage location
      "resource request".

   o  Registered the "error" OAuth parameter.

   o  Created the OAuth Error registry and registered errors.

   o  Changed the "OAuth2" OAuth access token type name to "Bearer".


   o  Incorporated feedback received on draft 01.  Most changes were to
      the security considerations section.  No normative changes were
      made.  Specific changes included:

   o  Changed terminology from "token reuse" to "token capture and

   o  Removed sentence "Encrypting the token contents is another
      alternative" from the security considerations since it was
      redundant and potentially confusing.

   o  Corrected some references to "resource server" to be
      "authorization server" in the security considerations.

   o  Generalized security considerations language about obtaining
      consent of the resource owner.

   o  Broadened scope of security considerations description for
      recommendation "Don't pass bearer tokens in page URLs".

   o  Removed unused reference to OAuth 1.0.

   o  Updated reference to framework specification and updated David
      Recordon's e-mail address.

   o  Removed security considerations text on authenticating clients.

   o  Registered the "OAuth2" OAuth access token type and "oauth_token"


   o  First public draft, which incorporates feedback received on -00
      including enhanced Security Considerations content.  This version
      is intended to accompany OAuth 2.0 draft 11.


   o  Initial draft based on preliminary version of OAuth 2.0 draft 11.

Authors' Addresses

   Michael B. Jones


   Dick Hardt

   David Recordon