OAuth Dynamic Client Registration Protocol
draft-ietf-oauth-dyn-reg-06

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OAuth Working Group                                       J. Richer, Ed.
Internet-Draft                                     The MITRE Corporation
Intended status: Standards Track                              J. Bradley
Expires: August 19, 2013                                   Ping Identity
                                                                M. Jones
                                                               Microsoft
                                                             M. Machulak
                                                    Newcastle University
                                                       February 15, 2013

               OAuth Dynamic Client Registration Protocol
                      draft-ietf-oauth-dyn-reg-06

Abstract

   This specification defines an endpoint and protocol for dynamic
   registration of OAuth Clients at an Authorization Server.

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 August 19, 2013.

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
   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
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of

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   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
   2.  Client Metadata  . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Client Registration Endpoint . . . . . . . . . . . . . . . . .  7
     3.1.  Client Registration Request  . . . . . . . . . . . . . . .  8
     3.2.  Client Registration Response . . . . . . . . . . . . . . .  9
   4.  Client Registration Access Endpoint  . . . . . . . . . . . . .  9
     4.1.  Forming the Client Registration Access Endpoint URL  . . .  9
     4.2.  Client Read Request  . . . . . . . . . . . . . . . . . . . 10
     4.3.  Client Update Request  . . . . . . . . . . . . . . . . . . 10
     4.4.  Client Delete Request  . . . . . . . . . . . . . . . . . . 12
   5.  Responses  . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.1.  Client Information Response  . . . . . . . . . . . . . . . 13
     5.2.  Client Registration Error Response . . . . . . . . . . . . 15
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   8.  Normative References . . . . . . . . . . . . . . . . . . . . . 17
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 18
   Appendix B.  Document History  . . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20

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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 requiring the two parties to interact before hand.
   Nevertheless, in order for the authorization server to accurately and
   securely 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 metadata, such as a display name and icon to be presented to
   the user during the authorization step.  This draft also provides a
   mechanism for the Client to read and update this information after
   the initial registration action.

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 [RFC6749].

   This specification defines the following additional terms:

   o  Client Registration Endpoint: The OAuth 2.0 Endpoint through which
      a Client can request new registration.  The means of the Client
      obtaining the URL for this endpoint are out of scope for this
      specification.

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   o  Client Registration Access Endpoint: The OAuth 2.0 Endpoint
      through which a specific Client can manage its registration
      information, provided by the Authorization Server to the Client.
      This URL for this endpoint is communicated to the client by the
      Authorization Server in the Client Information Response.

   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 read,
      update, and delete operations.  This token is associated with a
      particular Client.

2.  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, such as the list of
   valid redirect URIs.

   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.

   [[ Editor's note: normative language in the table below is meant to
   apply to the *client* when sending the request.  The paragraph above
   is meant to say that the server must at least accept all parameters
   and not fail with an error at an unknown parameter, especially if
   it's in the list below.  Also, extensions need to explicitly call out
   if they're not going to do something with one of these basic
   parameters instead of just ignoring their existence.  This is meant
   to be the *minimum set* of parameters for interoperability. ]]

   redirect_uris
      RECOMMENDED.  Array of redirect URIs for use in the Authorization
      Code and Implicit grant types.  An Authorization Server SHOULD
      require registration of valid redirect URIs for all clients that
      use these grant types in order to protect against token and
      credential theft attacks.

   client_name
      RECOMMENDED.  Human-readable name of the Client to be presented to
      the user.  If omitted, the Authorization Server MAY display to the
      user the raw "client_id" value instead.

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   client_url
      RECOMMENDED.  URL of the homepage of the Client.  If present, the
      server SHOULD display this URL to the end user in a clickable
      fashion.

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

   contacts
      OPTIONAL.  Array of email addresses for people responsible for
      this Client.  The Authorization Server MAY make these addresses
      available to end users for support requests for the Client.  An
      Authorization Server MAY use these email addresses as identifiers
      for an administrative page for this client.

   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.  Valid values are:

      *  "none": this is a public client as defined in OAuth 2.0 and
         does not have a client secret

      *  "client_secret_post": the client uses the HTTP POST parameters
         defined in OAuth2.0 section 2.3.1

      *  "client_secret_basic": the client uses HTTP Basic defined in
         OAuth 2.0 section 2.3.1

      *  "client_secret_jwt": the client uses the JWT Assertion profile
         with a symmetric secret issued by the server

      *  "private_key_jwt": the client uses the JWT Assertion profile
         with its own private key

      Other authentication methods may be defined by extension.  If
      unspecified or omitted, the default is "client_secret_basic",
      denoting HTTP Basic Authentication Scheme as specified in Section
      2.3.1 of OAuth 2.0.

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   scope
      OPTIONAL.  Space separated list of scope values (as described in
      OAuth 2.0 Section 3.3 [RFC6749]) that the client is declaring that
      it may use when requesting access tokens.  If omitted, an
      Authorization Server MAY register a Client with a default set of
      scopes.

   grant_type
      OPTIONAL.  Array of grant types that a client may use.  These
      grant types are defined as follows:

      *  "authorization_code": The Authorization Code Grant described in
         OAuth2 Section 4.1.

      *  "implicit": The Implicit Grant described in OAuth2 Section 4.2.

      *  "password": The Resource Owner Password Credentials Grant
         described in OAuth2 Section 4.3

      *  "client_credentials": The Client Credentials Grant described in
         OAuth2 Section 4.4

      *  "refresh_token": The Refresh Token Grant described in OAuth2
         Section 6.

      Authorization Servers MAY allow for other values as defined in
      grant type extensions to OAuth2.  The extension process is
      described in OAuth2 Section 2.5, and the value of this parameter
      MUST be the same as the value of the "grant_type" parameter
      defined in the extension.

   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 requests, such as requests to the Token
      Endpoint using the "private_key_jwt" assertion client credential.
      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 the server
      can use to encrypt responses to the Client.  If the Client
      registers both "jwk_encryption_url" and "x509_encryption_url", the

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      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 requests, such as
      requests to the Token Endpoint using the "private_key_jwt"
      assertion client credential.  If the Client registers both
      "x509_url" and "jwk_url", the keys contained in both formats MUST
      be the same.

   x509_encryption_url
      OPTIONAL.  URL for the Client's PEM encoded X.509 Certificate or
      Certificate chain that the server can use to encrypt 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.

3.  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/json" format.  The Client
   Registration Endpoint MUST be protected by a transport-layer security
   mechanism, and 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 Client Registration Endpoint MAY accept an initial authorization
   credential in the form of an OAuth 2.0 [RFC6749] 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.

   In order to support open registration and facilitate wider
   interoperability, the Client Registration Endpoint SHOULD allow
   initial registration requests with no authentication.  These requests
   MAY be rate-limited or otherwise limited to prevent a denial-of-
   service attack on the Client Registration Endpoint.

   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 to the
   Client Registration Access Endpoint (Section 4).  As such, the Client

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   Registration Access Endpoint MUST accept requests with OAuth 2.0
   Bearer Tokens [RFC6750] for these operations, whether or not the
   initial registration call requires authentication of some form.

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

3.1.  Client Registration 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 any parameters described in Client Metadata
   (Section 2) that the client wishes to specify for itself during the
   registration.  The Authorization Server MAY provision default values
   for any items omitted in the Client Metadata.

   The Client sends an HTTP POST to the Client Registration Endpoint
   with a content type of "application/json".  The HTTP Entity Payload
   is a JSON [RFC4627] document consisting of a JSON object and all
   parameters as top- level members of that JSON object.

   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
   Content-Type: application/json
   Accept: application/json
   Host: server.example.com

   {
    "redirect_uris":["https://client.example.org/callback",
       "https://client.example.org/callback2"]
    "client_name":"My Example Client",
    "token_endpoint_auth_method":"client_secret_basic",
    "scope":"read write dolphin",
    "logo_url":"https://client.example.org/logo.png",
    "jwk_url":"https://client.example.org/my_rsa_public_key.jwk"
   }

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3.2.  Client Registration Response

   Upon successful registration, the Authorization Server generates a
   new Client Identifier for the client.  This Client Identifier MUST be
   unique at the server and MUST NOT be in use by any other client.  The
   server responds with an HTTP 201 Created code and a body of type
   "application/json" with content described in Client Information
   Response (Section 5.1).

   Upon an unsuccessful registration, the Authorization Server responds
   with an error as described in Client Registration Error
   (Section 5.2).

4.  Client Registration Access Endpoint

   The Client Registration Access Endpoint is an OAuth 2.0 protected
   endpoint that is provisioned by the server for a specific client to
   be able to view and update its registered information.  The Client
   MUST include its Registration Access Token in all calls to this
   endpoint as an OAuth 2.0 Bearer Token [RFC6750].

   Operations on this endpoint are switched through the use of different
   HTTP methods [RFC2616].

4.1.  Forming the Client Registration Access Endpoint URL

   The Authorization Server MUST provide the client with the fully
   qualified URL in the "registration_access_url" element of the Client
   Information Response (Section 5.1).  The Authorization Server MUST
   NOT expect the client to construct or discover this URL on its own.
   The Client MUST use the URL as given by the server and MUST NOT
   construct this URL from component pieces.

   Depending on deployment characteristics, the Client Registration
   Access Endpoint URL may take any number of forms.  It is RECOMMENDED
   that this endpoint URL be formed through the use of a server-
   constructed URL string which combines the Client Registration
   Endpoint's URL and the issued client_id for this Client, with the
   latter as either a path parameter
   (https://server.example.com/register/client_id) or a query parameter
   (https://server.example.com/register/?update=client_id).  These
   common patterns can help the Server to more easily determine the
   client to which the request pertains, which MUST be matched against
   the client to which the Registration Access Token was issued.  If
   desired, the server MAY simply return the Client Registration
   Endpoint URL as the Client Registration Access Endpoint URL and
   change behavior based on the authentication context provided by the

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   Registration Access Token.

4.2.  Client Read Request

   In order to read the current configuration of the Client on the
   Authorization Server, the Client makes an HTTP GET request to the
   Client Registration Access Endpoint, authenticating with its
   Registration Access Token.

   Following is a non-normative example request (with line wraps for
   display purposes only):
   GET /register/s6BhdRkqt3 HTTP/1.1
   Accept: application/json
   Host: server.example.com
   Authorization: Bearer reg-23410913-abewfq.123483

   Upon successful read of the information for a currently active
   Client, the Authorization Server responds with an HTTP 200 OK with
   content type of "application/json" and a payload as described in
   Client Information Response (Section 5.1).

   If the client does not exist on this server, the server MUST return
   an HTTP 404 Not Found. [[ Editor's note: If the client doesn't exist,
   then the Refresh Access Token shouldn't be valid, making this kind of
   error a 403 at the auth layer instead.  How best to call this
   inconsistency out? ]]

4.3.  Client Update Request

   This operation updates a previously-registered client with new
   metadata at the Authorization Server.  This request is authenticated
   by the Registration Access Token issued to the client.

   The Client sends an HTTP PUT to the Client Registration Access
   Endpoint with a content type of "application/json".  The HTTP Entity
   Payload is a JSON [RFC4627] document consisting of a JSON object and
   all parameters as top- level members of that JSON object.

   This request MUST include all fields described in Client Metadata
   (Section 2) as returned to the Client from a previous register, read,
   or update operation.  The Client MUST NOT include the
   "registration_access_token", "registration_access_url", "expires_at",
   or "issued_at" fields described in Client Information Response
   (Section 5.1).

   Valid values of Client Metadata fields in this request MUST replace,
   not augment, the values previously associated with this Client.

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   Omitted fields MUST be treated as null or empty values by the server.

   The Client MUST include its client_id field in the request, and it
   MUST be the same as its currently-issued Client Identifier.  If the
   client includes its client_secret in the request, then it MUST match
   the currently-issued client_secret for that Client.  The client MUST
   NOT be allowed to overwrite its existing client_secret with its own
   value.

   For all metadata fields, the Authorization Server MAY replace any
   invalid values with suitable default values, and it MUST return any
   such fields to the Client in the response.

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

   Following is a non-normative example request (with line wraps for
   display purposes only):
   PUT /register/s6BhdRkqt3 HTTP/1.1
   Accept: application/json
   Host: server.example.com
   Authorization: Bearer reg-23410913-abewfq.123483

   {
    "client_id":"s6BhdRkqt3",
    "client_secret": "cf136dc3c1fc93f31185e5885805d",
    "redirect_uri":["https://client.example.org/callback",
       "https://client.example.org/alt"],
    "scope": "read write dolphin",
    "grant_type": ["authorization_code", "refresh_token"]
    "token_endpoint_auth_method": "client_secret_basic",
    "jwk_url": "https://client.example.org/my_rsa_public_key.jwk"
    "client_name":"My New Example",
    "logo_url":"https://client.example.org/newlogo.png"
   }

   Upon successful update, the Authorization Server responds with an
   HTTP 200 OK Message with content type "applicaiton/json" and a
   payload as described in Client Information Response (Section 5.1).
   The Authorization Server MAY include a new Client Secret and/or
   Registration Access Token in its response.  If so, the Client MUST
   immediately discard its previous Client Secret and/or Registration
   Access Token.

   If the Client does not exist on this server, the server MUST return
   an HTTP 404 Not Found. [[ Editor's note: If the client doesn't exist,
   then the Refresh Access Token shouldn't be valid, making this kind of

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   error a 403 at the auth layer instead.  How best to call this
   inconsistency out? ]]

   If the Client is not allowed to update its records, the server MUST
   respond with HTTP 403 Forbidden.

   If the Client attempts to set an invalid metadata field and the
   Authorization Server does not set a default value, the Authorization
   Server responds with an error as described in Client Registration
   Error Response (Section 5.2).

4.4.  Client Delete Request

   [[ Editor's note: The utility and nature of this function are still
   under active discussion.  This is a proposed set of functionality
   that a server MAY choose to implement, else give a 405 response to
   any client that tries, if it can't support it. ]]

   In order to deprovision itself on the Authorization Server, the
   Client makes an HTTP DELETE request to the Client Registration Access
   Endpoint.  This request is authenticated by the Registration Access
   Token issued to the client.

   Following is a non-normative example request (with line wraps for
   display purposes only):
   DELETE /register/s6BhdRkqt3 HTTP/1.1
   Accept: application/json
   Host: server.example.com
   Authorization: Bearer reg-23410913-abewfq.123483

   A successful delete action will invalidate the client_id,
   client_secret, and registration_access_token for this client, thereby
   preventing the client_id from being used at either the Authorization
   Endpoint or Token Endpoint of the Authorization Server.  The
   Authorization Server SHOULD immediately invalidate all existing
   authorization grants and currently-active tokens associated with this
   Client.

   If a Client has been successfully deprovisioned, the Authorization
   Server responds with an HTTP 204 No Content message.

   If there is no such client, the server responds with an HTTP 404 Not
   Found. [[ Editor's note: This is an inconsistent state and shouldn't
   happen.  See discussion about the Registration Access Token validity
   above. ]]

   If the client is not allowed to delete itself, the server responds

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   with HTTP 403 Forbidden.

   If the server does not support the delete method, it responds with an
   HTTP 405 Not Supported.

   Following is a non-normative example response:
   HTTP/1.1 204 No Content
   Cache-Control: no-store

5.  Responses

   In response to certain requests from the Client to either the Client
   Registration Endpoint or the Client Registration Access Endpoint as
   described in this specification, the Authorization Server sends the
   following response bodies.

5.1.  Client Information Response

   The response contains the following fields:

   , as well as a Client Secret if this client is a confidential client.
   The response also contains the fully qualified URL to the Client
   Registration Access Endpoint for this specific client that the client
   may use to obtain and update information about itself.  The response
   also contains a Registration Access Token that is to be used by the
   client to perform subsequent operations at the Client Registration
   Access Endpoint.

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

   client_secret
      OPTIONAL.  The Client secret.  If issued, this MUST be unique for
      each "client_id".  This value is used by confidential clients to
      authenticate to the Token Endpoint as described in OAuth 2.0
      Section 2.3.1.

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

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   issued_at
      OPTIONAL.  Specifies the timestamp when the Client 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.

   registration_access_token
      REQUIRED.  The Access token to be used by the client to perform
      actions on the Client Registration Access Endpoint.

   registration_access_url
      REQUIRED.  The fully qualified URL of the Client Registration
      Access Endpoint for this client.  The Client MUST use this URL as
      given when communicating with the Client Registration Access
      Endpoint. [[ Editor's note: The syntax for this parameter is still
      under active discussion.  There have been several alternative
      proposals to a flat URL here, including a structure based on HAL
      for JSON and a structure based on JSON-LD. ]]

   Additionally, the Authorization Server MUST return all registered
   metadata (Section 2) about this client, including any fields
   provisioned by the Authorization Server itself.  The Authorization
   Server MAY reject or replace any of the client's requested metadata
   values submitted during the registration or update requests and
   substitute them with suitable values.

   The response is an "application/json" document with all parameters as
   top-level members of a JSON object [RFC4627] .

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

   {
    "registration_access_token": "reg-23410913-abewfq.123483",
    "registration_access_url":
          "https://server.example.com/register/s6BhdRkqt3",
    "client_id":"s6BhdRkqt3",
    "client_secret": "cf136dc3c1fc93f31185e5885805d",
    "expires_at":2893276800
    "redirect_uris":["https://client.example.org/callback",
       "https://client.example.org/callback2"]
    "scope": "read write dolphin",
    "grant_type": ["authorization_code", "refresh_token"]
    "token_endpoint_auth_method": "client_secret_basic",
    "logo_url": "https://client.example.org/logo.png",
    "jwk_url": "https://client.example.org/my_rsa_public_key.jwk"
   }

5.2.  Client Registration Error Response

   When an OAuth error condition occurs, such as the client presenting
   an invalid Registration Access Token, the Authorization Server
   returns an Error Response as defined in Section 5.2 of the OAuth 2.0
   specification.

   When a registration error condition occurs, the Authorization Server
   returns an HTTP 400 status code with content type "application/json"
   consisting of a JSON object [RFC4627] describing the error in the
   response body.

   The JSON object contains two members:

   error
      The error code, a single ASCII string.

   error_description
      A human-readable text description of the error for debugging.

   This specification defines the following error codes:

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

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   invalid_client_metadata
      The value of one of the client metadata (Section 2) fields is
      invalid and the server has rejected this request.  Note that an
      Authorization server MAY choose to substitute a valid value for
      any requested parameter of a client's metadata.

   invalid_client_id
      Value of "client_id" is invalid.

   Following is a non-normative example of an error response (with line
   wraps for display purposes only):
   HTTP/1.1 400 Bad Request
   Content-Type: application/json
   Cache-Control: no-store

   {
    "error":"invalid_redirect_uri",
    "error_description":"The redirect URI of http://sketchy.example.com
      is not allowed for this server."
   }

6.  IANA Considerations

   This document makes no requests of IANA.

7.  Security Considerations

   [[ Editor's note: Following are some security considerations taken
   from the UMA and OpenID Connect source drafts.  These need to be
   massaged into a properly generic set of considerations. ]]

   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].

   As this endpoint is an OAuth2 Protected Resource, requests to the
   Registration Endpoint SHOULD have some rate limiting on failures to
   prevent the Registration Access Token from being disclosed though
   repeated access attempts.

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   The authorization server MUST treat all client metadata as self-
   asserted.  A rogue Client might use the name and logo for the
   legitimate Client, which it is trying to impersonate.  An
   Authorization Server needs to take steps to mitigate this phishing
   risk, since the logo could confuse users into thinking they're
   logging in to the legitimate Client.  For instance, an Authorization
   Server could warn if the domain/site of the logo doesn't match the
   domain/site of redirect URIs.  An Authorization Server can also
   present warning messages to end users about untrusted Clients in all
   cases, especially if such clients have been dynamically registered
   and have not been trusted by any users at the Authorization Server
   before.

   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".

   While the Client Secret can expire, the Registration Access Token
   should not expire while a client is still actively registered.  If
   this token were to expire, a Client could be left in a situation
   where it has no means of updating itself and must register itself
   anew.  As the Registration Access Tokens are long-term credentials,
   and since the Registration Access Token is a Bearer token and acts as
   the sole authentication for use at the Client Registration Access
   Endpoint, it MUST be protected by the Client as described in OAuth
   2.0 Bearer [RFC6750].

   If a Client is deprovisioned from a server, any outstanding
   Registration Access Tokens for that client MUST be invalidated at the
   same time.  Otherwise, this can lead to an inconsistent state wherein
   a Client could make requests to the Client Registration Access
   Endpoint where the authentication would succeed but the action would
   fail because the Client is no longer valid.

8.  Normative References

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

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              RFC 2246, January 1999.

   [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.

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

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

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

   [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.

   [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.

Appendix A.  Acknowledgments

   The authors thank the OAuth Working Group, the User-Managed Access
   Working Group, and the OpenID Connect Working Group participants for
   their input to this document.  In particular, the following
   individuals have been instrumental in their review and contribution
   to various versions of this document: Amanda Anganes, Tim Bray,
   Domenico Catalano, George Fletcher, Torsten Lodderstedt, Eve Maler,
   Thomas Hardjono, Nat Sakimura, and Christian Scholz.

Appendix B.  Document History

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

   -06

   o  Removed secret_rotation as a client-initiated action, including
      removing client secret rotation endpoint and parameters.

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   o  Changed _links structure to single value registration_access_url.

   o  Collapsed create/update/read responses into client info response.

   o  Changed return code of create action to 201.

   o  Added section to describe suggested generation and composition of
      Client Registration Access URL.

   o  Added clarifying text to PUT and POST requests to specify JSON in
      the body.

   o  Added Editor's Note to DELETE operation about its inclusion.

   o  Added Editor's Note to registration_access_url about alternate
      syntax proposals.

   -05

   o  changed redirect_uri and contact to lists instead of space
      delimited strings

   o  removed operation parameter

   o  added _links structure

   o  made client update management more RESTful

   o  split endpoint into three parts

   o  changed input to JSON from form-encoded

   o  added READ and DELETE operations

   o  removed Requirements section

   o  changed token_endpoint_auth_type back to
      token_endpoint_auth_method to match OIDC who changed to match us

   -04

   o  removed default_acr, too undefined in the general OAuth2 case

   o  removed default_max_auth_age, since there's no mechanism for
      supplying a non-default max_auth_age in OAuth2

   o  clarified signing and encryption URLs

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   o  changed token_endpoint_auth_method to token_endpoint_auth_type to
      match OIDC

   -03

   o  added scope and grant_type claims

   o  fixed various typos and changed wording for better clarity

   o  endpoint now returns the full set of client information

   o  operations on client_update allow for three actions on metadata:
      leave existing value, clear existing value, replace existing value
      with new value

   -02

   o  Reorganized contributors and references

   o  Moved OAuth references to RFC

   o  Reorganized model/protocol sections for clarity

   o  Changed terminology to "client register" instead of "client
      associate"

   o  Specified that client_id must match across all subsequent requests

   o  Fixed RFC2XML formatting, especially on lists

   -01

   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

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Authors' Addresses

   Justin Richer (editor)
   The MITRE Corporation

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

   John Bradley
   Ping Identity

   Email: ve7jtb@ve7jtb.com

   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com

   Maciej Machulak
   Newcastle University

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

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