OAuth Dynamic Client Registration Protocol
draft-ietf-oauth-dyn-reg-01

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Network Working Group                                     J. Richer, Ed.
Internet-Draft                                     The MITRE Corporation
Intended status: Standards Track                             T. Hardjono
Expires: May 9, 2013                                                 MIT
                                                             M. Machulak
                                                    Newcastle University
                                                                E. Maler
                                                             XMLgrrl.com
                                                               C. Scholz
                                                         COM.lounge GmbH
                                                             N. Sakimura
                                                                     NRI
                                                              J. Bradley
                                                           Ping Identity
                                                                M. Jones
                                                               Microsoft
                                                        November 5, 2012

               OAuth Dynamic Client Registration Protocol
                      draft-ietf-oauth-dyn-reg-01

Abstract

   This specification proposes an OAuth Dynamic Client Registration
   protocol.

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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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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 May 9, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (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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   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
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  3
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
     1.3.  Requirements . . . . . . . . . . . . . . . . . . . . . . .  4
       1.3.1.  The client needs to be uniquely identifiable by
               the authorization server . . . . . . . . . . . . . . .  4
       1.3.2.  The authorization server must collect metadata
               about a client for later user interaction  . . . . . .  4
       1.3.3.  The authorization server should have the option of
               strongly authenticating the client and its metadata  .  4
       1.3.4.  Dynamic client registration must be possible from
               both web-server applications and applications with
               other capabilities and limitations, such as native
               applications . . . . . . . . . . . . . . . . . . . . .  4
       1.3.5.  Transaction integrity must be ensured  . . . . . . . .  5
   2.  Client Registration Endpoint . . . . . . . . . . . . . . . . .  5
     2.1.  Client Association Request . . . . . . . . . . . . . . . .  6
     2.2.  Client Association Response  . . . . . . . . . . . . . . .  8
     2.3.  Client Update Request  . . . . . . . . . . . . . . . . . .  9
     2.4.  Client Update Response . . . . . . . . . . . . . . . . . . 10
     2.5.  Rotate Secret Request  . . . . . . . . . . . . . . . . . . 11
     2.6.  Rotate Secret Response . . . . . . . . . . . . . . . . . . 11
     2.7.  Client Registration Error Response . . . . . . . . . . . . 12
   3.  Client Metadata  . . . . . . . . . . . . . . . . . . . . . . . 13
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   6.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 16
   7.  Document History . . . . . . . . . . . . . . . . . . . . . . . 16
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 17
     8.2.  Non-Normative References . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19

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1.  Introduction

   In some use-case scenarios, it is desirable or necessary to allow
   OAuth clients to obtain authorization from an OAuth authorization
   server without the two parties having previously interacted.
   Nevertheless, in order for the authorization server to accurately
   represent to end-users which client is seeking authorization to
   access the end-user's resources, a method for automatic and unique
   registration of clients is needed.  The OAuth2 authorization
   framework does not define how the relationship between the Client and
   the Authorization Server is initialized, or how a given client is
   assigned a unique Client Identifier.  Historically, this has happened
   out-of-band from the OAuth protocol.  This draft provides a mechanism
   for a client to register itself with the Authorization Server, which
   can be used to dynamically provision a Client Identifier, and
   optionally a Client Secret.

   As part of the registration process, this specification also defines
   a mechanism for the client to present the Authorization Server with a
   set of meta information, such as a display name and icon to be
   presented to the user during the authorization step.  This draft
   provides a method for the client to register and update this
   information over time.

1.1.  Notational Conventions

   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 [RFC2119].

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

1.2.  Terminology

   This specification uses the terms "Access Token", "Refresh Token",
   "Authorization Code", "Authorization Grant", "Authorization Server",
   "Authorization Endpoint", "Client", "Client Identifier", "Client
   Secret", "Protected Resource", "Resource Owner", "Resource Server",
   and "Token Endpoint" defined by OAuth 2.0 [OAuth2.0].

   This specification defines the following additional terms:

   o  Client Registration Endpoint: The OAuth 2.0 Endpoint through which
      a Client can request new registration and manage the metadata
      associated with it.

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   o  Registration Access Token: An OAuth 2.0 Bearer Token issued by the
      Authorization Server through the Client Registration Endpoint
      which is used by the Client to authenticate itself during update
      and secret rotation operations.

1.3.  Requirements

   [[ Following are proposed requirements for dynamic client
   registration.  This section is intended for discussion and will
   likely be removed in the final draft. ]]

1.3.1.  The client needs to be uniquely identifiable by the
        authorization server

   In order for an authorization server to do proper user-delegated
   authorization and prevent unauthorized access it must be able to
   identify clients uniquely.  As is done today in OAuth, the client
   identifier (and optional secret) should thus be issued by the
   authorization server and not simply accepted as proposed by the
   client.

1.3.2.  The authorization server must collect metadata about a client
        for later user interaction

   In order for the authorization server to describe a client to an end-
   user in an authorization step it needs information about the client.
   This can be the client name at a minimum, but today servers usually
   request at least a description, a homepage URL, and an icon when
   doing manual registration.

1.3.3.  The authorization server should have the option of strongly
        authenticating the client and its metadata

   In order to prevent spoofing of clients and enable dynamic building
   of strong trust relationships, the authorization server should have
   the option to verify the provided information.  This might be solved
   using message signature verification.

1.3.4.  Dynamic client registration must be possible from both web-
        server applications and applications with other capabilities and
        limitations, such as native applications

   Each instance of a native application (that is, the specific instance
   running on each device) that is installed and run by the same user
   may need the option of getting a unique client identifier.  In this
   case, there are implications around gathering and displaying enough
   information to ensure that the end-user is delegating authorization
   to the intended application.  The registration protocol should be

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   simple and flexible enough to allow for multiple types of
   applications.

1.3.5.  Transaction integrity must be ensured

   When a client sends information to a server endpoint, it might take
   time for this data to propagate through big server installations that
   spread across various data centers.  Care needs to be taken that
   subsequent interactions with the user after the registration process,
   such as an authorization request, show the correct data.

2.  Client Registration Endpoint

   The Client Registration Endpoint is an OAuth 2.0 Endpoint defined in
   this document that is designed to allow a Client to register itself
   with the Authorization Server.  The Client Registration Endpoint MUST
   accept HTTP POST messages with request parameters encoded in the
   entity body using the "application/x-www-form-urlencoded" format.
   The Client Registration Endpoint MUST be protected by a transport-
   layer security mechanism when sending requests to the Registration
   Endpoint.  The server MUST support TLS 1.2 RFC 5246 [RFC5246] and/or
   TLS 1.0 [RFC2246] and MAY support additional transport-layer
   mechanisms meeting its security requirements.  When using TLS, the
   Client MUST perform a TLS/SSL server certificate check, per RFC 6125
   [RFC6125].

   The Endpoint defines three operations that a client can take on it,
   switched by the "operation" parameter:

   o  client_associate: generate a new Client Identifier (and optionally
      a Client Secret) and associate it with the set of presented
      metadata (Section 3)

   o  client_update: update the metadata (Section 3) associated with a
      Client Identifier

   o  rotate_secret: issue a new Registration Access Token and, if
      applicable, a Client Secret for a Client

   In order to facilitate registered clients updating their information,
   the Client Registration Endpoint issues a request_access_token for
   clients to securely identify themselves in future connections.  As
   such, the Endpoint MUST accept requests with OAuth 2.0 Bearer Tokens
   [OAuth.Bearer] for these operations.

   In order to support open registration and facilitate wider
   interoperability, the Client Registration Endpoint SHOULD allow

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   client_associate requests with no further authentication.  These
   requests MAY be rate-limited to prevent a denial-of-service attack on
   the Client Registration Endpoint.

   In addition, the Client Registration Endpoint MAY accept an initial
   authorization credential in the form of an OAuth 2.0 [OAuth2.0]
   access token in order to limit registration to only previously
   authorized parties.  The method by which this access token is
   obtained by the registrant is generally out-of-band and is out of
   scope of this specification.

   These two aspects, operation selection and client authentication, are
   represented by two parameters common to all operations:

   operation  REQUIRED.  Values are "client_associate" (for new
      registrations), "rotate_secret" to request rotation of the
      "client_secret", and "client_update" (for updating parameters of
      an existing "client_id").

   access_token  OPTIONAL.  An OAuth2 Bearer token used to access the
      Client Registration Endpoint, as defined in OAuth2 Bearer.  This
      parameter MUST NOT be sent if the Access Token is sent in the HTTP
      Authorization header as described in Section 7.1 of OAuth 2.0
      [OAuth2.0].  Access Tokens sent in the authorization header must
      be OAuth 2.0 Bearer Tokens [OAuth.Bearer].

   Each operation takes a different parameter set, and all operations
   are described below.

   The Client Registration Endpoint MUST ignore all parameters it does
   not understand.

2.1.  Client Association Request

   This operation registers a new client to the Authorization Server.
   The Authorization Server assigns this client a unique Client
   Identifier, optionally assigns a Client Secret, and associates the
   metadata given in the request with the issued Client Identifier.  The
   request includes the two parameters described above as well as any
   parameters described in Client Metadata (Section 3).

   operation  REQUIRED, MUST have the value "client_associate"

   access_token  OPTIONAL, used to restrict new client registration

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   redirect_uris
      REQUIRED

   client_name  RECOMMENDED

   client_url
      RECOMMENDED

   logo_url  OPTIONAL

   contacts  OPTIONAL

   tos_url  OPTIONAL

   token_endpoint_auth_method  OPTIONAL

   policy_url  OPTIONAL

   jwk_url  OPTIONAL

   jwk_encryption_url  OPTIONAL

   x509_url  OPTIONAL

   x509_encryption_url  OPTIONAL

   require_signed_request_object  OPTIONAL

   default_max_age  OPTIONAL

   default_acr  OPTIONAL

   For example, a client could send the following registration request
   to the Client Registration Endpoint:

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   Following is a non-normative example request (with line wraps for
   display purposes only):
   POST /register HTTP/1.1
   Accept: application/x-www-form-urlencoded
   Host: server.example.com
   Authorization: Bearer eyJhbGciOiJSUzI1NiJ9.eyJ ... fQ.8Gj_-sj ... _X

   operation=client_associate
   &redirect_uris=https://client.example.org/callback
       %20https://client.example.org/callback2
   &client_name=My%20Example%20
   &logo_url=https://client.example.org/logo.png
   &token_endpoint_auth_type=client_secret_basic
   &jwk_url=https://client.example.org/my_rsa_public_key.jwk

2.2.  Client Association Response

   Upon successful association, the Client Registration Endpoint returns
   the newly-created Client Identifier and, optionally, a Client Secret.
   The response also contains a Registration Access Token that is to be
   used by the client to perform subsequent operations at this endpoint.
   These items are returned as a JSON document with the following fields
   as top-level members of the root JSON object.

   client_id  REQUIRED.  The unique Client identifier, MUST NOT be
      currently valid for any other registered Client.

   client_secret  OPTIONAL.  The Client secret.  This MUST be unique for
      each "client_id".  This value us used by confidential clients.  It
      is not required for clients selecting a token_endpoint_auth_type
      of "private_key_jwt"

   registration_access_token  REQUIRED The Access token to be used by
      the client to perform "client_update" and "rotate_secret"
      requests.

   issued_at
      OPTIONAL.  Specifies the timestamp when the identifier was issued.
      The timestamp value MUST be a positive integer.  The value is
      expressed in the number of seconds since January 1, 1970 00:00:00
      GMT.

   expires_at  OPTIONAL.  The number of seconds from 1970-01-01T0:0:0Z
      as measured in UTC that the "client_secret" will expire or "0" if
      they do not expire.  See RFC 3339 [RFC3339] for details regarding
      date/times in general and UTC in particular.

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   Following is a non-normative example response:
   HTTP/1.1 200 OK
   Content-Type: application/json
   Cache-Control: no-store

   {
    "client_id":"s6BhdRkqt3",
    "client_secret":
     "cf136dc3c1fd9153029bb9c6cc9ecead918bad9887fce6c93f31185e5885805d",
     "registration_access_token": "this.is.a.access.token.value.ffx83",
    "expires_at":2893276800
   }

2.3.  Client Update Request

   This operation updates a previously-registered client with new
   metadata at the Authorization Server.  This request MUST be protected
   by the Registration Authorization Token associated with the Client
   Identifier.  This request MAY include any fields described in Client
   Metadata (Section 3).  The values of Client Metadata fields in this
   request MUST replace (not augment) the values previously associated
   with this client_identifier.  Empty values in Client Metadata SHOULD
   be taken as a request to clear any existing value of that field.

   operation  REQUIRED, MUST have the value "client_update"

   access_token  REQUIRED, unless presented in the Authorization Header
      as in OAuth2 Bearer [OAuth.Bearer].  The Registration Access Token
      that was issued during the client_associate step, or previous
      client_update or rotate_secret calls.

   redirect_uris
      REQUIRED

   client_name  RECOMMENDED

   client_url
      RECOMMENDED

   logo_url  OPTIONAL

   contacts  OPTIONAL

   tos_url  OPTIONAL

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   token_endpoint_auth_method  OPTIONAL

   policy_url  OPTIONAL

   jwk_url  OPTIONAL

   jwk_encryption_url  OPTIONAL

   x509_url  OPTIONAL

   x509_encryption_url  OPTIONAL

   require_signed_request_object  OPTIONAL

   default_max_age  OPTIONAL

   default_acr  OPTIONAL

   For example, a client could send the following registration request
   to the Client Registration Endpoint:

   Following is a non-normative example request (with line wraps for
   display purposes only):
   POST /register HTTP/1.1
   Accept: application/x-www-form-urlencoded
   Host: server.example.com
   Authorization: Bearer eyJhbGciOiJSUzI1NiJ9.eyJ ... fQ.8Gj_-sj ... _X

   operation=client_update
   &redirect_uris=https://client.example.org/callback
       %20https://client.example.org/callback2
   &client_name=My%20Example%20
   &logo_url=https://client.example.org/logo.png
   &token_endpoint_auth_type=client_secret_basic
   &jwk_url=https://client.example.org/my_rsa_public_key.jwk

2.4.  Client Update Response

   Upon successful update, the Client Registration Endpoint returns a
   JSON document with the following fields as top-level members of the
   root JSON object.

   client_id  REQUIRED.  The unique Client identifier, MUST NOT be
      currently valid for any other registered Client.

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   Following is a non-normative example response:
   HTTP/1.1 200 OK
   Content-Type: application/json
   Cache-Control: no-store

   {
    "client_id":"s6BhdRkqt3",
   }

   [[ Editor's note: should this return the entire client data object,
   for confirmation and review, including any fields that may have been
   asserted by the AS? ]]

2.5.  Rotate Secret Request

   This operation allows the client to rotate its current Client Secret,
   if it has one.  If the client has not been issued a Client Secret,
   this operation is an error. [[ Editor's note: could this request be
   used to rotate the Registration Access Token, even when there's not a
   client_secret?  Should something else be used to rotate the token
   independently?  This is an open issue. ]]

   operation  REQUIRED.  MUST have the value rotate_secret

   access_token  REQUIRED.  The Registration Access Token that was
      issued during the client_associate step, or previous client_update
      or rotate_secret calls.

   Following is a non-normative example request (with line wraps for
   display purposes only):
   POST /register HTTP/1.1
   Accept: application/x-www-form-urlencoded
   Host: server.example.com
   Authorization: Bearer eyJhbGciOiJSUzI1NiJ9.eyJ ... fQ.8Gj_-sj ... _X

   operation=rotate_secret

2.6.  Rotate Secret Response

   Upon successful rotation of the client secret, the Client
   Registration Endpoint returns a JSON document with the following
   fields as top-level members of the root JSON object.

   client_id  REQUIRED.  The unique Client identifier, MUST NOT be
      currently valid for any other registered Client.

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   client_secret  REQUIRED.  The Client secret.  This MUST be unique for
      each "client_id".

   registration_access_token  REQUIRED The Access token to be used by
      the client to perform subsequent "client_update" and
      "rotate_secret" requests.

   issued_at
      OPTIONAL.  Specifies the timestamp when the identifier was issued.
      The timestamp value MUST be a positive integer.  The value is
      expressed in the number of seconds since January 1, 1970 00:00:00
      GMT.

   expires_at  OPTIONAL.  The number of seconds from 1970-01-01T0:0:0Z
      as measured in UTC that the "client_secret" will expire or "0" if
      they do not expire.  See RFC 3339 [RFC3339] for details regarding
      date/times in general and UTC in particular.

   Following is a non-normative example response:
   HTTP/1.1 200 OK
   Content-Type: application/json
   Cache-Control: no-store

   {
    "client_id":"s6BhdRkqt3",
    "client_secret":
     "cf136dc3c1fd9153029bb9c6cc9ecead918bad9887fce6c93f31185e5885805d",
     "registration_access_token": "this.is.a.access.token.value.ffx83",
    "expires_at":2893276800
   }

2.7.  Client Registration Error Response

   When an OAuth error condition occurs, the Client Registration
   Endpoint returns an Error Response as defined in Section 5.2 of the
   OAuth 2.0 specification.

   When a registration error condition occurs, the Client Registration
   Endpoint returns a HTTP 400 status code including a JSON object
   describing the error in the response body.

   The JSON object contains two members:

   error  The error code, a single ASCII string.

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   error_description  The additional text description of the error for
      debugging.

   This specification defines the following error codes:

   invalid_operation  The value of "operation" is invalid or not
      supported.

   invalid_redirect_uri  The value of one or more "redirect_uris" is
      invalid.

   invalid_client_metadata  The value of one of the client metadata
      (Section 3) fields is invalid.

   Following is a non-normative example of an error response:
HTTP/1.1 400 Bad Request
Content-Type: application/json
Cache-Control: no-store

{
 "error":"invalid_operation",
 "error_description":"The value of the operation parameter must be one of client_associate, rotate_secret or client_update."
}

3.  Client Metadata

   Clients generally have an array of metadata associated with their
   unique Client Identifier at the Authorization Server.  These can
   range from human-facing display strings, such as a client name, to
   items that impact the security of the protocol,

   Extensions and profiles of this specification MAY expand this list,
   but MUST at least accept all parameters on this list.  The
   Authorization Server MUST ignore any additional parameters sent by
   the Client that it does not understand.

   redirect_uris
      REQUIRED A space-delimited list of redirect URIs.

   client_name  RECOMMENDED.  Human-readable name of the Client to be
      presented to the user.

   client_url
      RECOMMENDED.  This field contains the URL of the homepage of the
      client.

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   logo_url  OPTIONAL.  A URL that references a logo for the Client
      application.  If present, the server SHOULD display this image to
      the end user during approval.

   contacts  OPTIONAL.  Space delimited list of email addresses for
      people allowed to administer the information for this Client.
      This is used by some providers to enable a web UI to modify the
      Client information.

   tos_url  OPTIONAL.  URL that points to a human-readable Terms of
      Service for the Client.  The Authorization Server SHOULD display
      this URL to the End-User if it is given.

   token_endpoint_auth_method  OPTIONAL.  The requested authentication
      type for the Token Endpoint.  The options are
      "client_secret_post", "client_secret_basic", "client_secret_jwt",
      and "private_key_jwt".  Other Authentication methods may be
      defined by extension.  If unspecified or omitted, the default is
      "client_secret_basic" HTTP Basic Authentication Scheme as
      specified in Section 2.3.1 of OAuth 2.0 [OAuth2.0]. [[ this list
      of terms needs to be expanded and fully defined, especially in
      reference to signed-jwt client authentication ]]

   policy_url  OPTIONAL.  A URL location that the Client provides to the
      End-User to read about the how the profile data will be used.  The
      Authorization Server SHOULD display this URL to the End-User if it
      is given.

   jwk_url  OPTIONAL.  URL for the Client's JSON Web Key [JWK] document
      that is used for signing Token Endpoint Requests.  If
      jwk_encryption_url is not provided, the key at jwk_url is also
      used as the key to encrypt responses to the Client.  If the Client
      registers both "x509_url" and "jwk_url", the keys contained in
      both formats MUST be the same.

   jwk_encryption_url  OPTIONAL.  URL for the Client's JSON Web Key
      [JWK] that is used to encrypt any responses to the Client.  If the
      Client registers both "jwk_encryption_url" and
      "x509_encryption_url", the keys contained in both formats MUST be
      the same.

   x509_url  OPTIONAL.  URL for the Client's PEM encoded X.509
      Certificate or Certificate chain that is used for signing Token
      Endpoint Requests.  If "x509_encryption_url" is not provided,
      "x509_url" it is also used to encrypt responses to the Client.  If
      the Client registers both "x509_url" and "jwk_url", the keys
      contained in both formats MUST be the same.

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   x509_encryption_url  OPTIONAL.  URL for the Client's PEM encoded
      X.509 Certificate or Certificate chain that is used to encrypt the
      ID Token and User Info Endpoint Responses to the Client.  If the
      Client registers both "jwk_encryption_url" and
      "x509_encryption_url", the keys contained in both formats SHOULD
      be the same.

   require_signed_request_object  OPTIONAL.  The JWS [JWS] "alg"
      algorithm [JWA] that MUST be required by the Authorization Server.
      The valid values are listed in Section 3.1 of JWA [JWA].  Servers
      SHOULD support "RS256".

   default_max_age  OPTIONAL. (default max authentication age): Type:
      Integer - Specifies that the End-User must be actively
      authenticated if any present authentication is older than the
      specified number of seconds.  (The "max_age" request parameter
      corresponds to the OpenID 2.0 PAPE "max_auth_age" request
      parameter.)  The "max_age" claim in the request object overrides
      this default value.

   default_acr  OPTIONAL. (default authentication context class
      reference): Type: String - Specifies the default value that the
      Authorization server must use for processing requests from this
      client.  The "acrs_supported" element of discovery contains a list
      of the supported "acr" values for this server.  The "acr" claim in
      the request object overrides this default value.

4.  IANA Considerations

   This document makes no requests of IANA.

5.  Security Considerations

   [[ Editor's note: Following are some security considerations taken
   whole from the UMA and OpenID Connect source drafts. ]]

   o  No client authentication: The server should treat unsigned pushed
      client metadata as self-asserted.

   o  Weak client authentication: The server should treat unsigned
      pulled client metadata as self-asserted unless the domain of the
      client matches the client metadata URL and the URL is well-known
      and trusted.

   o  Strong client authentication: The server should treat signed
      client metadata (pushed or pulled) and a signed metadata URL as

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      self-asserted unless it can verify the signature as being from a
      trusted source.

   Since requests to the Client Registration Endpoint result in the
   transmission of clear-text credentials (in the HTTP request and
   response), the server MUST require the use of a transport-layer
   security mechanism when sending requests to the Registration
   Endpoint.  The server MUST support TLS 1.2 RFC 5246 [RFC5246] and/or
   TLS 1.0 [RFC2246] and MAY support additional transport-layer
   mechanisms meeting its security requirements.  When using TLS, the
   Client MUST perform a TLS/SSL server certificate check, per RFC 6125
   [RFC6125].

   Requests to the Registration Endpoint for "client_update" MUST have
   some rate limiting on failures to prevent the Client secret from
   being disclosed though repeated access attempts.

   A rogue RP might use the logo for the legitimate RP, which it is
   trying to impersonate.  An IdP needs to take steps to mitigate this
   phishing risk, since the logo could confuse users into thinking
   they're logging in to the legitimate RP.  An IdP could also warn if
   the domain/site of the logo doesn't match the domain/site of redirect
   URIs.  An IdP can also make warnings against untrusted RPs in all
   cases, especially if they're dynamically registered, have not been
   trusted by any users at the IdP before, and want to use the logo
   feature.

   In a situation where the Authorization Server is supporting open
   Client registration, it must be extremely careful with any URL
   provided by the Client that will be displayed to the user (e.g.
   "logo_url" and "policy_url").  A rogue Client could specify a
   registration request with a reference to a drive-by download in the
   "policy_url".  The Authorization Server should check to see if the
   "logo_url" and "policy_url" have the same host as the hosts defined
   in the array of "redirect_uris".

6.  Acknowledgments

   The authors thank the User-Managed Access Work Group and the OpenID
   Connect Working Group participants for their input to this document.

7.  Document History

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

   - 01

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   o  Merged UMA and OpenID Connect registrations into a single document

   o  Changed to form-paramter inputs to endpoint

   o  Removed pull-based registration

   - 00

   o  Imported original UMA draft specification

8.  References

8.1.  Normative References

   [JSON]     Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", 2006,
              <http://tools.ietf.org/html/rfc4627>.

   [JWA]      Jones, M., "JSON Web Algorithms", May 2012.

   [JWE]      Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
              Encryption (JWE)", May 2012.

   [JWK]      Jones, M., "JSON Web Key (JWK)", May 2012.

   [JWS]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature", May 2012.

   [JWT]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token",
              May 2012.

   [OAuth-Sig]
              Balfanz, D., "OAuth Signature proposals", 2010, <http://
              www.ietf.org/mail-archive/web/oauth/current/
              msg03893.html>.

   [OAuth.Bearer]
              Jones, M. and D. Hardt, "OAuth 2.0 Protocol: Bearer
              Tokens", Aug 2012.

   [OAuth2.0]
              Hardt, D., "OAuth 2.0 Authorization Protocol", July 2012.

   [OpenID.Messages]
              Sakimura, N., Bradley, J., Jones, M., de Medeiros, B.,
              Mortimore, C., and E. Jay, "OpenID Connect Messages 1.0",
              May 2012.

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   [OpenID.Session]
              Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
              N. Agarwal, "OpenID Connect Session Management 1.0",
              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.

   [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.

   [RFC3339]  Klyne, G., Ed. and C. Newman, "Date and Time on the
              Internet: Timestamps", RFC 3339, July 2002.

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

   [RFC5785]  Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
              Uniform Resource Identifiers (URIs)", RFC 5785,
              April 2010.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, March 2011.

   [USA15]    Davis, M., Whistler, K., and M. Duerst, "Unicode
              Normalization Forms", Unicode Standard Annex 15, 09 2009.

   [hostmeta]
              Hammer-Lahav, E., "Web Host Metadata", 2010, <http://
              xml.resource.org/public/rfc/bibxml3/
              reference.I-D.draft-hammer-hostmeta-13.xml>.

8.2.  Non-Normative References

   [UMA-Core]
              Scholz, C., "UMA Requirements", 2010, <http://
              tools.ietf.org/id/draft-hardjono-oauth-umacore-04.txt>.

   [UMA-Reqs]
              Maler, E., "UMA Requirements", 2010, <http://

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              kantarainitiative.org/confluence/display/uma/
              UMA+Requirements>.

   [UMA-UC]   Akram, H., "UMA Explained", 2010, <http://
              kantarainitiative.org/confluence/display/uma/
              UMA+Scenarios+and+Use+Cases>.

Authors' Addresses

   Justin Richer (editor)
   The MITRE Corporation

   Phone:
   Fax:
   Email: jricher@mitre.org
   URI:

   Thomas Hardjono
   MIT

   Phone:
   Fax:
   Email: hardjono@mit.edu
   URI:

   Maciej Machulak
   Newcastle University

   Email: m.p.machulak@ncl.ac.uk
   URI:   http://ncl.ac.uk/

   Eve Maler
   XMLgrrl.com

   Email: eve@xmlgrrl.com
   URI:   http://www.xmlgrrl.com

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   Christian Scholz
   COM.lounge GmbH

   Phone:
   Fax:
   Email:
   URI:

   Nat Sakimura
   Nomura Research Institute, Ltd.

   Email: n-sakimura@nri.co.jp

   John Bradley
   Ping Identity

   Email: ve7jtb@ve7jtb.com

   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com

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