path: root/doc/rfc/rfc7592.txt

Internet Engineering Task Force (IETF)                    J. Richer, Ed.
Request for Comments: 7592
Category: Experimental                                          M. Jones
ISSN: 2070-1721                                                Microsoft
                                                              J. Bradley
                                                           Ping Identity
                                                             M. Machulak
                                                    Newcastle University
                                                               July 2015


       OAuth 2.0 Dynamic Client Registration Management Protocol

Abstract

   This specification defines methods for management of OAuth 2.0
   dynamic client registrations for use cases in which the properties of
   a registered client may need to be changed during the lifetime of the
   client.  Not all authorization servers supporting dynamic client
   registration will support these management methods.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This document is a product of the Internet Engineering
   Task Force (IETF).  It represents the consensus of the IETF
   community.  It has received public review and has been approved for
   publication by the Internet Engineering Steering Group (IESG).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7592.













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Copyright Notice

   Copyright (c) 2015 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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Protocol Flow . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Client Configuration Endpoint . . . . . . . . . . . . . . . .   5
     2.1.  Client Read Request . . . . . . . . . . . . . . . . . . .   6
     2.2.  Client Update Request . . . . . . . . . . . . . . . . . .   7
     2.3.  Client Delete Request . . . . . . . . . . . . . . . . . .   9
   3.  Client Information Response . . . . . . . . . . . . . . . . .  10
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   6.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  13
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .  13
   Appendix A.  Registration Tokens and Client Credentials . . . . .  15
     A.1.  Credential Rotation . . . . . . . . . . . . . . . . . . .  16
   Appendix B.  Forming the Client Configuration Endpoint URL  . . .  16
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   In order for an OAuth 2.0 client to utilize an OAuth 2.0
   authorization server, the client needs specific information to
   interact with the server, including an OAuth 2.0 client identifier to
   use with that server.  "OAuth 2.0 Dynamic Client Registration
   Protocol" [RFC7591] describes how an OAuth 2.0 client can be
   dynamically registered with an authorization server to obtain this
   information and how metadata about the client can be registered with
   the server.





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   This specification extends the core registration specification by
   defining a set of methods for management of dynamic OAuth 2.0 client
   registrations beyond those defined in the core registration
   specification.  In some situations, the registered metadata of a
   client can change over time, either by modification at the
   authorization server or by a change in the client software itself.
   This specification provides methods for the current registration
   state of a client to be queried at the authorization server, methods
   for the registration of a client to be updated at the authorization
   server, and methods for the client to be unregistered from the
   authorization server.

   This Experimental RFC is intended to encourage development and
   deployment of interoperable solutions with the intent that feedback
   from this experience will inform a future standard.

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", "authorization
   code", "authorization endpoint", "authorization grant",
   "authorization server", "client", "client identifier", "client
   secret", "grant type", "protected resource", "redirection URI",
   "refresh token", "resource owner", "resource server", "response
   type", and "token endpoint" defined by OAuth 2.0 [RFC6749] and the
   terms defined by "OAuth 2.0 Client Dynamic Registration Protocol"
   [RFC7591].

   This specification defines the following terms:

   Client Configuration Endpoint
      OAuth 2.0 endpoint through which registration information for a
      registered client can be managed.  This URL for this endpoint is
      returned by the authorization server in the client information
      response.








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   Registration Access Token
      OAuth 2.0 Bearer Token issued by the authorization server through
      the client registration endpoint that is used to authenticate the
      caller when accessing the client's registration information at the
      client configuration endpoint.  This access token is associated
      with a particular registered client.

1.3.  Protocol Flow

   This extends the flow in "OAuth 2.0 Dynamic Client Registration
   Protocol" [RFC7591] as follows:

        +--------(A)- Initial Access Token (OPTIONAL)
        |
        |   +----(B)- Software Statement (OPTIONAL)
        |   |
        v   v
    +-----------+                                      +---------------+
    |           |--(C)- Client Registration Request -->|    Client     |
    |           |                                      | Registration  |
    |           |<-(D)- Client Information Response ---|   Endpoint    |
    |           |                                      +---------------+
    |           |
    |           |                                      +---------------+
    | Client or |--(E)- Read or Update Request ------->|               |
    | Developer |                                      |               |
    |           |<-(F)- Client Information Response ---|    Client     |
    |           |                                      | Configuration |
    |           |                                      |   Endpoint    |
    |           |                                      |               |
    |           |--(G)- Delete Request --------------->|               |
    |           |                                      |               |
    |           |<-(H)- Delete Confirmation -----------|               |
    +-----------+                                      +---------------+

   Figure 1: Abstract Extended Dynamic Client Registration Flow

   The abstract OAuth 2.0 client dynamic registration flow illustrated
   in Figure 1 describes the interaction between the client or developer
   and the endpoints defined in this specification and its parent.  This
   figure does not demonstrate error conditions.  This flow includes the
   following steps:

   (A)   Optionally, the client or developer is issued an initial access
         token for use with the client registration endpoint.  The
         method by which the initial access token is issued to the
         client or developer is out of scope for this specification.




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   (B)   Optionally, the client or developer is issued a software
         statement for use with the client registration endpoint.  The
         method by which the software statement is issued to the client
         or developer is out of scope for this specification.

   (C)   The client or developer calls the client registration endpoint
         with its desired registration metadata, optionally including
         the initial access token from (A) if one is required by the
         authorization server.

   (D)   The authorization server registers the client and returns:

         *  the client's registered metadata,

         *  a client identifier that is unique to the server,

         *  a set of client credentials such as a client secret, if
            applicable for this client,

         *  a URI pointing to the client configuration endpoint, and

         *  a registration access token to be used when calling the
            client configuration endpoint.

   (E)   The client or developer optionally calls the client
         configuration endpoint with a read or update request using the
         registration access token issued in (D).  An update request
         contains all of the client's registered metadata.

   (F)   The authorization server responds with the client's current
         configuration, potentially including a new registration access
         token and a new set of client credentials such as a client
         secret if applicable for this client.  If a new registration
         access token is issued, it replaces the token issued in (D) for
         all subsequent calls to the client configuration endpoint.

   (G)   The client or developer optionally calls the client
         configuration endpoint with a delete request using the
         registration access token issued in (D) or (F).

   (H)   The authorization server deprovisions the client and responds
         with a confirmation that the deletion has taken place.

2.  Client Configuration Endpoint

   The client configuration endpoint is an OAuth 2.0 protected resource
   that is provisioned by the server to facilitate viewing, updating,
   and deleting a client's registered information.  The location of this



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   endpoint is communicated to the client through the
   "registration_client_uri" member of the client information response,
   as specified in Section 3.  The client MUST use its registration
   access token in all calls to this endpoint as an OAuth 2.0 Bearer
   Token [RFC6750].

   The client configuration endpoint MUST be protected by a transport-
   layer security mechanism, as described in Section 5.

   Operations on this endpoint are switched through the use of different
   HTTP methods [RFC7231].  If an authorization server does not support
   a particular method on the client configuration endpoint, it MUST
   respond with the appropriate error code.

2.1.  Client Read Request

   To read the current configuration of the client on the authorization
   server, the client makes an HTTP GET request to the client
   configuration endpoint, authenticating with its registration access
   token.

   The following is a non-normative example request:

     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
   Section 3.  Some values in the response, including the
   "client_secret" and "registration_access_token", MAY be different
   from those in the initial registration response.  If the
   authorization server includes a new client secret and/or registration
   access token in its response, the client MUST immediately discard its
   previous client secret and/or registration access token.  The value
   of the "client_id" MUST NOT change from the initial registration
   response.

   If the registration access token used to make this request is not
   valid, the server MUST respond with an error as described in the
   OAuth Bearer Token Usage specification [RFC6750].

   If the client does not exist on this server, the server MUST respond
   with HTTP 401 Unauthorized and the registration access token used to
   make this request SHOULD be immediately revoked.




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   If the client does not have permission to read its record, the server
   MUST return an HTTP 403 Forbidden.

2.2.  Client Update Request

   To update a previously registered client's registration with an
   authorization server, the client makes an HTTP PUT request to the
   client configuration endpoint with a content type of "application/
   json".  The HTTP entity payload is a JSON [RFC7159] document
   consisting of a JSON object and all parameters as top-level members
   of that JSON object.  This request is authenticated by the
   registration access token issued to the client.

   This request MUST include all client metadata fields as returned to
   the client from a previous registration, read, or update operation.
   The updated client metadata fields request MUST NOT include the
   "registration_access_token", "registration_client_uri",
   "client_secret_expires_at", or "client_id_issued_at" fields described
   in Section 3.

   Valid values of client metadata fields in this request MUST replace,
   not augment, the values previously associated with this client.
   Omitted fields MUST be treated as null or empty values by the server,
   indicating the client's request to delete them from the client's
   registration.  The authorization server MAY ignore any null or empty
   value in the request just as any other value.

   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 the "client_secret" field in the request, the value
   of this field 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 chosen 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 with new information.










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   The following is a non-normative example request:

     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_uris": [
        "https://client.example.org/callback",
        "https://client.example.org/alt"],
      "grant_types": ["authorization_code", "refresh_token"],
      "token_endpoint_auth_method": "client_secret_basic",
      "jwks_uri": "https://client.example.org/my_public_keys.jwks",
      "client_name": "My New Example",
      "client_name#fr": "Mon Nouvel Exemple",
      "logo_uri": "https://client.example.org/newlogo.png",
      "logo_uri#fr": "https://client.example.org/fr/newlogo.png"
     }

   This example uses client metadata values defined in [RFC7591].

   Upon successful update, the authorization server responds with an
   HTTP 200 OK message with content type "application/json" and a
   payload as described in Section 3.  Some values in the response,
   including the "client_secret" and "registration_access_token", MAY be
   different from those in the initial registration response.  If the
   authorization server includes a new client secret and/or registration
   access token in its response, the client MUST immediately discard its
   previous client secret and/or registration access token.  The value
   of the "client_id" MUST NOT change from the initial registration
   response.

   If the registration access token used to make this request is not
   valid, the server MUST respond with an error as described in the
   OAuth Bearer Token Usage specification [RFC6750].

   If the client does not exist on this server, the server MUST respond
   with HTTP 401 Unauthorized, and the registration access token used to
   make this request SHOULD be immediately revoked.

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






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   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 [RFC7591].

2.3.  Client Delete Request

   To deprovision itself on the authorization server, the client makes
   an HTTP DELETE request to the client configuration endpoint.  This
   request is authenticated by the registration access token issued to
   the client.

   The following is a non-normative example request:

     DELETE /register/s6BhdRkqt3 HTTP/1.1
     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.
   If possible, the authorization server SHOULD immediately invalidate
   all existing authorization grants and currently active access tokens,
   all refresh tokens, and all other tokens associated with this client.

   If a client has been successfully deprovisioned, the authorization
   server MUST respond with an HTTP 204 No Content message.

   If the server does not support the delete method, the server MUST
   respond with HTTP 405 Not Supported.

   If the registration access token used to make this request is not
   valid, the server MUST respond with an error as described in the
   OAuth Bearer Token Usage specification [RFC6750].

   If the client does not exist on this server, the server MUST respond
   with HTTP 401 Unauthorized and the registration access token used to
   make this request SHOULD be immediately revoked, if possible.

   If the client is not allowed to delete itself, the server MUST
   respond with HTTP 403 Forbidden.

   The following is a non-normative example response:

     HTTP/1.1 204 No Content
     Cache-Control: no-store
     Pragma: no-cache




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3.  Client Information Response

   This specification extends the client information response defined in
   "OAuth 2.0 Client Dynamic Registration" [RFC7591], which states that
   the response contains the client identifier (as well as the client
   secret if the client is a confidential client).  When used with this
   specification, the client information response also contains the
   fully qualified URL of the client configuration endpoint (Section 2)
   for this specific client that the client or developer may use to
   manage the client's registration configuration, as well as a
   registration access token that is to be used by the client or
   developer to perform subsequent operations at the client
   configuration endpoint.

   registration_client_uri
      REQUIRED.  String containing the fully qualified URL of the client
      configuration endpoint for this client.

   registration_access_token
      REQUIRED.  String containing the access token to be used at the
      client configuration endpoint to perform subsequent operations
      upon the client registration.

   Additionally, the authorization server MUST return all registered
   metadata 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 [RFC7159].



















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   The following is a non-normative example response:

     HTTP/1.1 200 OK
     Content-Type: application/json
     Cache-Control: no-store
     Pragma: no-cache

     {
      "registration_access_token": "reg-23410913-abewfq.123483",
      "registration_client_uri":
         "https://server.example.com/register/s6BhdRkqt3",
      "client_id": "s6BhdRkqt3",
      "client_secret": "cf136dc3c1fc93f31185e5885805d",
      "client_id_issued_at": 2893256800,
      "client_secret_expires_at": 2893276800,
      "client_name": "My Example Client",
      "client_name#ja-Jpan-JP":
         "\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D",
      "redirect_uris": [
        "https://client.example.org/callback",
        "https://client.example.org/callback2"],
      "grant_types": ["authorization_code", "refresh_token"],
      "token_endpoint_auth_method": "client_secret_basic",
      "logo_uri": "https://client.example.org/logo.png",
      "jwks_uri": "https://client.example.org/my_public_keys.jwks"
     }

4.  IANA Considerations

   This specification registers the following client metadata names and
   descriptions in the "OAuth Dynamic Client Registration Metadata"
   registry established by [RFC7591]:

   o  Client Metadata Name: "registration_access_token"

   o  Client Metadata Description: OAuth 2.0 Bearer Token used to access
      the client configuration endpoint

   o  Change Controller: IESG

   o  Specification Document(s): RFC 7592

   o  Client Metadata Name: "registration_client_uri"

   o  Client Metadata Description: Fully qualified URI of the client
      registration endpoint

   o  Change Controller: IESG



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   o  Specification Document(s): RFC 7592

5.  Security Considerations

   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 developer or client could be left in a
   situation where they have no means of retrieving, updating, or
   deleting the client's registration information.  Were that the case,
   a new registration would be required, thereby generating a new client
   identifier.  However, to limit the exposure surface of the
   registration access token, the registration access token MAY be
   rotated when the developer or client does a read or update operation
   on the client's client configuration endpoint.  As the registration
   access tokens are relatively long-term credentials, and since the
   registration access token is a Bearer Token and acts as the sole
   authentication for use at the client configuration endpoint, it MUST
   be protected by the developer or client as described in the OAuth 2.0
   Bearer Token Usage specification [RFC6750].

   Since requests to the client configuration endpoint result in the
   transmission of clear-text credentials (in the HTTP request and
   response), the authorization server MUST require the use of a
   transport-layer security mechanism when sending requests to the
   endpoint.  The server MUST support TLS 1.2 [RFC5246] and MAY support
   additional transport-layer security mechanisms meeting its security
   requirements.  When using TLS, the client MUST perform a TLS/SSL
   server certificate check, per RFC 6125 [RFC6125].  Implementation
   security considerations can be found in Recommendations for Secure
   Use of TLS and DTLS [BCP195].

   Since possession of the registration access token authorizes the
   holder to potentially read, modify, or delete a client's registration
   (including its credentials such as a client_secret), the registration
   access token MUST contain sufficient entropy to prevent a random
   guessing attack of this token, such as described in Section 5.2 of
   [RFC6750] and Section 5.1.4.2.2 of [RFC6819].

   If a client is deprovisioned from a server, any outstanding
   registration access token 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 configuration endpoint
   where the authentication would succeed but the action would fail
   because the client is no longer valid.  The authorization server MUST
   treat all such requests as if the registration access token was
   invalid by returning an HTTP 401 Unauthorized error, as described.





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6.  Privacy Considerations

   This specification poses no additional privacy considerations beyond
   those described in the core "OAuth 2.0 Dynamic Client Registration
   Protocol" [RFC7591].

7.  Normative References

   [BCP195]   Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, May 2015,
              <http://www.rfc-editor.org/info/bcp195>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <http://www.rfc-editor.org/info/rfc5246>.

   [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, DOI 10.17487/RFC6125, March
              2011, <http://www.rfc-editor.org/info/rfc6125>.

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <http://www.rfc-editor.org/info/rfc6749>.

   [RFC6750]  Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
              Framework: Bearer Token Usage", RFC 6750,
              DOI 10.17487/RFC6750, October 2012,
              <http://www.rfc-editor.org/info/rfc6750>.

   [RFC6819]  Lodderstedt, T., Ed., McGloin, M., and P. Hunt, "OAuth 2.0
              Threat Model and Security Considerations", RFC 6819,
              DOI 10.17487/RFC6819, January 2013,
              <http://www.rfc-editor.org/info/rfc6819>.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <http://www.rfc-editor.org/info/rfc7159>.



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   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <http://www.rfc-editor.org/info/rfc7231>.

   [RFC7591]  Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
              P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
              RFC 7591, DOI 10.17487/RFC7591, July 2015,
              <http://www.rfc-editor.org/info/rfc7591>.










































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Appendix A.  Registration Tokens and Client Credentials

   Throughout the course of the dynamic registration protocol, there are
   three different classes of credentials in play, each with different
   properties and targets.

   o  The initial access token is optionally used by the client or
      developer at the registration endpoint.  This is an OAuth 2.0
      token that is used to authorize the initial client registration
      request.  The content, structure, generation, and validation of
      this token are out of scope for this specification.  The
      authorization server can use this token to verify that the
      presenter is allowed to dynamically register new clients.  This
      token may be shared among multiple instances of a client to allow
      them to each register separately, thereby letting the
      authorization server use this token to tie multiple instances of
      registered clients (each with their own distinct client
      identifier) back to the party to whom the initial access token was
      issued, usually an application developer.  This token is usually
      intended to be used only at the client registration endpoint.

   o  The registration access token is used by the client or developer
      at the client configuration endpoint and represents the holder's
      authorization to manage the registration of a client.  This is an
      OAuth 2.0 Bearer Token that is issued from the client registration
      endpoint in response to a client registration request and is
      returned in a client information response.  The registration
      access token is uniquely bound to the client identifier and is
      required to be presented with all calls to the client
      configuration endpoint.  The registration access token should be
      protected as described in [RFC6750] and should not be shared
      between instances of a client.  If a registration access token is
      shared between client instances, one instance could change or
      delete registration values for all other instances of the client.
      The registration access token can be rotated through the use of
      the client read or update method on the client configuration
      endpoint.  The registration access token is intended to be used
      only at the client configuration endpoint.













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   o  The client credentials (such as "client_secret") are optional
      depending on the type of client and are used to retrieve OAuth
      tokens.  Client credentials are most often bound to particular
      instances of a client and should not be shared between instances.
      Note that since not all types of clients have client credentials,
      they cannot be used to manage client registrations at the client
      configuration endpoint.  The client credentials can be rotated
      through the use of the client read or update method on the client
      configuration endpoint.  The client credentials are intended to be
      used only at the token endpoint.

A.1.  Credential Rotation

   The authorization server may be configured to issue new registration
   access tokens and/or client credentials (such as a "client_secret")
   throughout the lifetime of the client.  This may help minimize the
   impact of exposed credentials.  The authorization server conveys new
   registration access tokens and client credentials (if applicable) to
   the client in the client information response of either a read or
   update request to the client configuration endpoint.  The client's
   current registration access token and client credentials (if
   applicable) MUST be included in the client information response.

   The registration access token SHOULD be rotated only in response to a
   read or update request to the client configuration endpoint.  At this
   point, the new registration access token is returned to the client,
   the old registration access token MUST be discarded by the client,
   and it SHOULD be discarded by the server, if possible.  If, instead,
   the registration access token were to expire or be invalidated
   outside of such requests, the client or developer might be locked out
   of managing the client's configuration.

   Note that the authorization server decides the frequency of the
   credential rotation and not the client.  Methods by which the client
   can request credential rotation are outside the scope of this
   document.

Appendix B.  Forming the Client Configuration Endpoint URL

   The authorization server MUST provide the client with the fully
   qualified URL in the "registration_client_uri" element of the Client
   Information Response, as specified in Section 3.  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.






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   Depending on deployment characteristics, the client configuration
   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 that combines the client registration endpoint's URL and
   the issued "client_id" for this client, with the latter as either a
   path parameter or a query parameter.  For example, a client with the
   client identifier "s6BhdRkqt3" could be given a client configuration
   endpoint URL of "https://server.example.com/register/s6BhdRkqt3"
   (path parameter) or of "https://server.example.com/
   register?client_id=s6BhdRkqt3" (query parameter).  In both of these
   cases, the client simply uses the URL as given by the authorization
   server.

   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 configuration endpoint URL and change
   behavior based on the authentication context provided by the
   registration access token.

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 draft versions of this document: Amanda Anganes, Derek
   Atkins, Tim Bray, Domenico Catalano, Donald Coffin, Vladimir
   Dzhuvinov, George Fletcher, Thomas Hardjono, Phil Hunt, William Kim,
   Torsten Lodderstedt, Eve Maler, Josh Mandel, Nov Matake, Tony
   Nadalin, Nat Sakimura, Christian Scholz, and Hannes Tschofenig.



















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Authors' Addresses

   Justin Richer (editor)

   Email: ietf@justin.richer.org


   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com
   URI:   http://self-issued.info/


   John Bradley
   Ping Identity

   Email: ve7jtb@ve7jtb.com


   Maciej Machulak
   Newcastle University

   Email: maciej.machulak@gmail.com



























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