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Versions: (draft-richer-oauth-dyn-reg-core) 00 01 02 03 04 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 RFC 7591

OAuth Working Group                                            J. Richer
Internet-Draft                                     The MITRE Corporation
Intended status: Standards Track                                M. Jones
Expires: August 10, 2014                                       Microsoft
                                                              J. Bradley
                                                           Ping Identity
                                                             M. Machulak
                                                    Newcastle University
                                                                 P. Hunt
                                                      Oracle Corporation
                                                        February 6, 2014


          OAuth 2.0 Dynamic Client Registration Core Protocol
                      draft-ietf-oauth-dyn-reg-16

Abstract

   This specification defines mechanisms used to dynamically register
   OAuth 2.0 clients at authorization servers.

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 10, 2014.

Copyright Notice

   Copyright (c) 2014 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



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   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.















































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  4
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.3.  Protocol Flow  . . . . . . . . . . . . . . . . . . . . . .  6
   2.  Client Metadata  . . . . . . . . . . . . . . . . . . . . . . .  7
     2.1.  Relationship between Grant Types and Response Types  . . .  9
   3.  Software Statement . . . . . . . . . . . . . . . . . . . . . . 10
   4.  Client Registration Endpoint . . . . . . . . . . . . . . . . . 10
     4.1.  Client Registration Request  . . . . . . . . . . . . . . . 11
     4.2.  Client Registration Response . . . . . . . . . . . . . . . 13
   5.  Responses  . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.1.  Client Information Response  . . . . . . . . . . . . . . . 13
     5.2.  Client Registration Error Response . . . . . . . . . . . . 15
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
     6.1.  OAuth Registration Client Metadata Registry  . . . . . . . 16
       6.1.1.  Registration Template  . . . . . . . . . . . . . . . . 17
       6.1.2.  Initial Registry Contents  . . . . . . . . . . . . . . 17
     6.2.  OAuth Token Endpoint Authentication Methods Registry . . . 18
       6.2.1.  Registration Template  . . . . . . . . . . . . . . . . 18
       6.2.2.  Initial Registry Contents  . . . . . . . . . . . . . . 19
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 20
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 21
   Appendix A.  Use Cases . . . . . . . . . . . . . . . . . . . . . . 22
     A.1.  Open versus Protected Dynamic Client Registration  . . . . 22
       A.1.1.  Open Dynamic Client Registration . . . . . . . . . . . 22
       A.1.2.  Protected Dynamic Client Registration  . . . . . . . . 22
     A.2.  Registration Without or With Software Statements . . . . . 22
       A.2.1.  Registration Without a Software Statement  . . . . . . 22
       A.2.2.  Registration With a Software Statement . . . . . . . . 22
     A.3.  Registration by the Client or the Developer  . . . . . . . 23
       A.3.1.  Registration by the Client . . . . . . . . . . . . . . 23
       A.3.2.  Registration by the Developer  . . . . . . . . . . . . 23
     A.4.  Client ID per Client Instance or per Client Software . . . 23
       A.4.1.  Client ID per Client Software Instance . . . . . . . . 23
       A.4.2.  Client ID Shared between all Instances of Client
               Software . . . . . . . . . . . . . . . . . . . . . . . 23
     A.5.  Stateful or Stateless Registration . . . . . . . . . . . . 23
       A.5.1.  Stateful Client Registration . . . . . . . . . . . . . 24
       A.5.2.  Stateless Client Registration  . . . . . . . . . . . . 24
   Appendix B.  Acknowledgments . . . . . . . . . . . . . . . . . . . 24
   Appendix C.  Document History  . . . . . . . . . . . . . . . . . . 24
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29





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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 ID to use at
   that server.  This specification describes how an OAuth 2.0 client
   can be dynamically registered with an authorization server to obtain
   this information.

   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 set of valid redirection URIs.  This
   metadata can either be communicated in a self-asserted fashion or as
   a set of metadata called a software statement, which can be signed;
   in the case of a signed software statement, the signer is vouching
   for the validity of the data about the client.

   The mechanisms defined in this specification can be used either for a
   client to dynamically register itself with authorization servers or
   for a client developer to programmatically register the client with
   authorization servers.

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",
   "Response Type", and "Token Endpoint" defined by OAuth 2.0 [RFC6749]
   and uses the term "Claim" defined by JSON Web Token (JWT) [JWT].

   This specification defines the following terms:

   Client Developer  The person or organization that builds a client
      software package and prepares it for distribution.  A client
      developer obtains a software statement from a software publisher,
      or self-generates one for the purposes of facilitating client
      registration.




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   Client Instance  A deployed instance of a piece of client software.
      Multiple instances of the same piece of client software MAY use
      the same Client ID value at an authorization server, provided that
      the Redirection URI values and potentially other values dictated
      by authorization server policy are the same for all instances.

   Client Software  Software implementing an OAuth 2.0 client.

   Client Registration Endpoint  OAuth 2.0 endpoint through which a
      client can be registered at an authorization server.  The means by
      which the URL for this endpoint is obtained are out of scope for
      this specification.

   Initial Access Token  OAuth 2.0 access token optionally issued by an
      Authorization Server and used to authorize calls to the client
      registration endpoint.  The type and format of this token are
      likely service-specific and are out of scope for this
      specification.  The means by which the authorization server issues
      this token as well as the means by which the registration endpoint
      validates this token are out of scope for this specification.

   Deployment Organization  An administrative security domain under
      which, a software API is deployed and protected by an OAuth 2.0
      framework.  In simple cloud deployments, the software API
      publisher and the deployment organization may be the same.  In
      other scenarios, a software publisher may be working with many
      different deployment organizations.

   Software API Deployment  A deployment instance of a software API that
      is protected by OAuth 2.0 in a particular deployment organization
      domain.  For any particular software API, there may be one or more
      deployments.  A software API deployment typically has an
      associated OAuth 2.0 authorization server endpoint as well as a
      client registration endpoint.  The means by which endpoints are
      obtained (discovery) are out of scope for this specification.

   Software API Publisher  The organization that defines a particular
      web accessible API that may deployed in one or more deployment
      environments.  A publisher may be any commercial, public, private,
      or open source organization that is responsible for publishing and
      distributing software that may be protected via OAuth 2.0.  A
      software API publisher may issue software statements which client
      developers use to distribute with their software to facilitate
      registration.  In some cases a software API publisher and a client
      developer may be the same organization.






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   Software Statement  A JSON Web Token (JWT) [JWT] that asserts
      metadata values about the client software.  The JWT MUST be signed
      and contain an "iss" (issuer) claim if its metadata values are
      being attested to by the issuer; if the metadata values are not
      being attested to, the JWT MAY be unsigned.  This can be used by
      the registration system to qualify clients for eligibility to
      register.  It may also be accepted by some authorization servers
      directly as a Client ID value, without prior registration.

1.3.  Protocol Flow


        +--------(A)- Initial Access Token (OPTIONAL)
        |
        |   +----(B)- Software Statement (OPTIONAL)
        |   |
        v   v
    +-----------+                                      +---------------+
    |           |--(C)- Client Registration Request -->|    Client     |
    | Client or |                                      | Registration  |
    | Developer |<-(D)- Client Information Response ---|   Endpoint    |
    |           |                                      +---------------+
    +-----------+

   Figure 1: Abstract 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 endpoint defined in this specification.  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 giving access to 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.

   (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.





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   (D)  The authorization server registers the client and returns the
      client's registered metadata, a client identifier that is unique
      at the server, a set of client credentials such as a client secret
      if applicable for this client, and possibly other values.


2.  Client Metadata

   Clients have a set of metadata values associated with their unique
   client identifier at an authorization server, such as the list of
   valid redirect URIs.

   The client metadata values are used in two ways:

   o  as input values to registration requests, and

   o  as output values in registration responses.

   These client metadata values are defined by this specification:

   redirect_uris  Array of redirect URIs for use in redirect-based flows
      such as the authorization code and implicit grant types.  It is
      RECOMMENDED that clients using these flows register this
      parameter, and an authorization server SHOULD require registration
      of valid redirect URIs for all clients that use these grant types
      to protect against token and credential theft attacks.

   token_endpoint_auth_method  The requested authentication method for
      the token endpoint.  Values defined by this specification are:

      *  "none": The client 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 OAuth 2.0 section 2.3.1.

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

      Additional values can be defined via the IANA OAuth Token Endpoint
      Authentication Methods Registry Section 6.2.  Absolute URIs can
      also be used as values for this parameter without being
      registered.  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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   grant_types  Array of OAuth 2.0 grant types that the Client may use.
      These grant types are defined as follows:

      *  "authorization_code": The Authorization Code Grant described in
         OAuth 2.0 Section 4.1

      *  "implicit": The Implicit Grant described in OAuth 2.0 Section
         4.2

      *  "password": The Resource Owner Password Credentials Grant
         described in OAuth 2.0 Section 4.3

      *  "client_credentials": The Client Credentials Grant described in
         OAuth 2.0 Section 4.4

      *  "refresh_token": The Refresh Token Grant described in OAuth 2.0
         Section 6.

      *  "urn:ietf:params:oauth:grant-type:jwt-bearer": The JWT Bearer
         Grant defined in OAuth JWT Bearer Token Profiles [OAuth.JWT].

      *  "urn:ietf:params:oauth:grant-type:saml2-bearer": The SAML 2
         Bearer Grant defined in OAuth SAML 2 Bearer Token Profiles
         [OAuth.SAML2].

      Authorization Servers MAY allow for other values as defined in
      grant type extensions to OAuth 2.0.  The extension process is
      described in OAuth 2.0 Section 2.5.  If the token endpoint is used
      in the grant type, the value of this parameter MUST be the same as
      the value of the "grant_type" parameter passed to the token
      endpoint defined in the extension.

   response_types  Array of the OAuth 2.0 response types that the Client
      may use.  These response types are defined as follows:

      *  "code": The Authorization Code response described in OAuth 2.0
         Section 4.1.

      *  "token": The Implicit response described in OAuth 2.0 Section
         4.2.

      Authorization servers MAY allow for other values as defined in
      response type extensions to OAuth 2.0.  The extension process is
      described in OAuth 2.0 Section 2.5.  If the authorization endpoint
      is used by the grant type, the value of this parameter MUST be the
      same as the value of the "response_type" parameter passed to the
      authorization endpoint defined in the extension.




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   Authorization servers MUST accept all fields in this list.
   Extensions and profiles of this specification MAY expand this list.
   For instance, the [OAuth.Registration.Metadata] specification defines
   additional client metadata values.  The authorization server MUST
   ignore any client metadata values sent by the Client that it does not
   understand.

   Client metadata values can either be communicated directly in the
   body of a registration request, as described in Section 4.1, or
   included as claims in a software statement, as described in
   Section 3.  If the same client metadata name is present in both
   locations, the value in the software statement SHOULD take
   precedence.

2.1.  Relationship between Grant Types and Response Types

   The "grant_types" and "response_types" values described above are
   partially orthogonal, as they refer to arguments passed to different
   endpoints in the OAuth protocol.  However, they are related in that
   the "grant_types" available to a client influence the
   "response_types" that the client is allowed to use, and vice versa.
   For instance, a "grant_types" value that includes
   "authorization_code" implies a "response_types" value that includes
   "code", as both values are defined as part of the OAuth 2.0
   authorization code grant.  As such, a server supporting these fields
   SHOULD take steps to ensure that a client cannot register itself into
   an inconsistent state.

   The correlation between the two fields is listed in the table below.

   +-----------------------------------------------+-------------------+
   | grant_types value includes:                   | response_types    |
   |                                               | value includes:   |
   +-----------------------------------------------+-------------------+
   | authorization_code                            | code              |
   | implicit                                      | token             |
   | password                                      | (none)            |
   | client_credentials                            | (none)            |
   | refresh_token                                 | (none)            |
   | urn:ietf:params:oauth:grant-type:jwt-bearer   | (none)            |
   | urn:ietf:params:oauth:grant-type:saml2-bearer | (none)            |
   +-----------------------------------------------+-------------------+

   Extensions and profiles of this document that introduce new values to
   either the "grant_types" or "response_types" parameter MUST document
   all correspondences between these two parameter types.





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3.  Software Statement

   A Software Statement is a JSON Web Token (JWT) [JWT] that asserts
   metadata values about the client software.  The JWT MUST be signed
   and contain an "iss" (issuer) claim if its metadata values are being
   attested to by the issuer; if the metadata values are not being
   attested to, the JWT MAY be unsigned.  This can be used by the
   registration system to qualify clients for eligibility to register.
   It may also be accepted by some authorization servers directly as a
   Client ID value, without prior registration.

   To obtain a software statement, a client developer may generate a
   client specific JWT, or a client developer may register with a
   software API publisher to obtain a software statement.  The statement
   is typically distributed with all copies of a client application.

   The criteria by which authorization servers determine whether to
   trust and utilize the information in a software statement is beyond
   the scope of this specification.

   If the authorization server determines that the claims in a software
   statement uniquely identify a piece of software, the same Client ID
   value MAY be returned for all dynamic registrations using that
   software statement.  However, authorization servers MAY alternatively
   return a unique Client ID value for each dynamic registration of a
   piece of software.

   In some cases, authorization servers MAY choose to accept a software
   statement value directly as a Client ID in an authorization request,
   without a prior dynamic client registration having been performed.
   The circumstances under which an authorization server would do so,
   and the specific software statement characteristics required in this
   case, are beyond the scope of this specification.


4.  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 be registered
   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].



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   The client registration endpoint MAY be an OAuth 2.0 protected
   resource and accept an initial access token in the form of an OAuth
   2.0 [RFC6749] access token to limit registration to only previously
   authorized parties.  The method by which the initial access token is
   obtained by the registrant is generally out-of-band and is out of
   scope for this specification.  The method by which the initial access
   token is verified and validated by the client registration endpoint
   is out of scope for this specification.

   To support open registration and facilitate wider interoperability,
   the client registration endpoint SHOULD allow initial registration
   requests with no authorization (which is to say, with no OAuth 2.0
   access token in the request).  These requests MAY be rate-limited or
   otherwise limited to prevent a denial-of-service attack on the client
   registration endpoint.

   The client registration endpoint MUST ignore all parameters it does
   not understand.

4.1.  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 client metadata parameters being specified for
   the client during the registration.  The authorization server MAY
   provision default values for any items omitted in the client
   metadata.

   Client metadata values may also be provided in a software statement,
   as described in Section 3.  Software statements are included in
   registration requests using this registration parameter:

   software_statement  A software statement containing client metadata
      values about the client software as claims.

   To register, the client or developer 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, if the server supports open registration (with no
   initial access token), the client could send the following
   registration request to the client registration endpoint:






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   The following is a non-normative example request not using an initial
   access token (with line wraps within values 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"],
      "token_endpoint_auth_method":"client_secret_basic",
      "example_extension_parameter": "example_value"
     }

   Alternatively, if the server supports authorized registration, the
   developer or the client will be provisioned with an initial access
   token (the method by which the initial access token is obtained is
   out of scope for this specification).  The developer or client sends
   the following authorized registration request to the client
   registration endpoint.  Note that the initial access token sent in
   this example as an OAuth 2.0 Bearer Token [RFC6750], but any OAuth
   2.0 token type could be used by an authorization server.

   The following is a non-normative example request using an initial
   access token (with line wraps within values for display purposes
   only):

     POST /register HTTP/1.1
     Content-Type: application/json
     Accept: application/json
     Authorization: Bearer ey23f2.adfj230.af32-developer321
     Host: server.example.com

     {
      "redirect_uris":["https://client.example.org/callback",
         "https://client.example.org/callback2"],
      "token_endpoint_auth_method":"client_secret_basic",
      "example_extension_parameter": "example_value"
     }









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   In the following example, some registration parameters are conveyed
   as claims in a software statement (with line wraps within values 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"
       ],
       "software_statement":"eyJhbGciOiJFUzI1NiJ9.
          eyJpc3Mi[...omitted for brevity...].
          J9l-ZhwP[...omitted for brevity...]",
       "extension_parameter":"foo"
     }

4.2.  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 as described in Section 5.1.

   Upon an unsuccessful registration, the authorization server responds
   with an error, as described in Section 5.2.


5.  Responses

   The following responses are sent in response to registration
   requests.

5.1.  Client Information Response

   The response contains the client identifier as well as the client
   secret, if the client is a confidential client.  The response MAY
   contain additional fields as specified by extensions to this
   specification.








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   client_id  REQUIRED.  Unique client identifier.  It MUST NOT be
      currently valid for any other distinct registered client.  It MAY
      be the same as the Client ID value used by other instances of this
      client, provided that the Redirection URI values and potentially
      other values dictated by authorization server policy are the same
      for all instances.

   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 [RFC6749] Section 2.3.1.

   client_id_issued_at  OPTIONAL.  Time at which the Client Identifier
      was issued.  The time is represented as the number of seconds from
      1970-01-01T0:0:0Z as measured in UTC until the date/time.

   client_secret_expires_at  REQUIRED if "client_secret" is issued.
      Time at which the "client_secret" will expire or 0 if it will not
      expire.  The time is represented as the number of seconds from
      1970-01-01T0:0:0Z as measured in UTC until the date/time.

   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 [RFC4627].

   If a software statement was used as part of the registration, its
   value SHOULD be returned in the response and its value MUST be
   returned if the authorization server supports registration management
   operations [OAuth.Registration.Management] that would require its
   presence in subsequent operations.  Client metadata elements used
   from the software statement MUST also be returned directly as top-
   level client metadata values in the registration response (possibly
   with different values, since the values requested and the values used
   may differ).











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   Following is a non-normative example response:

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

     {
      "client_id":"s6BhdRkqt3",
      "client_secret": "cf136dc3c1fc93f31185e5885805d",
      "client_id_issued_at":2893256800,
      "client_secret_expires_at":2893276800,
      "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",
      "example_extension_parameter": "example_value"
     }

5.2.  Client Registration Error Response

   When an OAuth 2.0 error condition occurs, such as the client
   presenting an invalid initial access token, the authorization server
   returns an error response appropriate to the OAuth 2.0 token type.

   When a registration error condition occurs, the authorization server
   returns an HTTP 400 status code (unless otherwise specified) 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  Single ASCII error code string.

   error_description  Human-readable ASCII text description of the error
      used for debugging.

   This specification defines the following error codes:

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

   invalid_client_metadata  The value of one of the client metadata
      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.




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   invalid_software_statement  The software statement presented is
      invalid.

   unapproved_software_statement  The software statement presented is
      not approved for use with this authorization server.

   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
     Pragma: no-cache

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


6.  IANA Considerations

6.1.  OAuth Registration Client Metadata Registry

   This specification establishes the OAuth Registration Client Metadata
   registry.

   OAuth registration client metadata values are registered with a
   Specification Required ([RFC5226]) after a two-week review period on
   the oauth-ext-review@ietf.org mailing list, on the advice of one or
   more Designated Experts.  However, to allow for the allocation of
   values prior to publication, the Designated Expert(s) may approve
   registration once they are satisfied that such a specification will
   be published.

   Registration requests must be sent to the oauth-ext-review@ietf.org
   mailing list for review and comment, with an appropriate subject
   (e.g., "Request to register OAuth Registration Client Metadata name:
   example").

   Within the review period, the Designated Expert(s) will either
   approve or deny the registration request, communicating this decision
   to the review list and IANA.  Denials should include an explanation
   and, if applicable, suggestions as to how to make the request
   successful.

   IANA must only accept registry updates from the Designated Expert(s)



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   and should direct all requests for registration to the review mailing
   list.

6.1.1.  Registration Template

   Client Metadata Name:  The name requested (e.g., "example").  This
      name is case sensitive.  Names that match other registered names
      in a case insensitive manner SHOULD NOT be accepted.

   Client Metadata Description:
      Brief description of the metadata value (e.g., "Example
      description").

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

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

6.1.2.  Initial Registry Contents

   The initial contents of the OAuth Registration Client Metadata
   registry are:

   o  Client Metadata Name: "redirect_uris"
   o  Client Metadata Description: Array of redirect URIs for use in
      redirect-based flows
   o  Change controller: IESG
   o  Specification document(s): [[ this document ]]

   o  Client Metadata Name: "token_endpoint_auth_method"
   o  Client Metadata Description: Requested authentication method for
      the token endpoint
   o  Change controller: IESG
   o  Specification document(s): [[ this document ]]

   o  Client Metadata Name: "grant_types"
   o  Client Metadata Description: Array of OAuth 2.0 grant types that
      the Client may use
   o  Change controller: IESG
   o  Specification document(s): [[ this document ]]





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   o  Client Metadata Name: "response_types"
   o  Client Metadata Description: Array of the OAuth 2.0 response types
      that the Client may use
   o  Change controller: IESG
   o  Specification document(s): [[ this document ]]

6.2.  OAuth Token Endpoint Authentication Methods Registry

   This specification establishes the OAuth Token Endpoint
   Authentication Methods registry.

   Additional values for use as "token_endpoint_auth_method" metadata
   values are registered with a Specification Required ([RFC5226]) after
   a two-week review period on the oauth-ext-review@ietf.org mailing
   list, on the advice of one or more Designated Experts.  However, to
   allow for the allocation of values prior to publication, the
   Designated Expert(s) may approve registration once they are satisfied
   that such a specification will be published.

   Registration requests must be sent to the oauth-ext-review@ietf.org
   mailing list for review and comment, with an appropriate subject
   (e.g., "Request to register token_endpoint_auth_method value:
   example").

   Within the review period, the Designated Expert(s) will either
   approve or deny the registration request, communicating this decision
   to the review list and IANA.  Denials should include an explanation
   and, if applicable, suggestions as to how to make the request
   successful.

   IANA must only accept registry updates from the Designated Expert(s)
   and should direct all requests for registration to the review mailing
   list.

6.2.1.  Registration Template

   Token Endpoint Authorization Method Name:  The name requested (e.g.,
      "example").  This name is case sensitive.  Names that match other
      registered names in a case insensitive manner SHOULD NOT be
      accepted.

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






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

6.2.2.  Initial Registry Contents

   The initial contents of the OAuth Token Endpoint Authentication
   Methods registry are:

   o  Token Endpoint Authorization Method Name: "none"
   o  Change controller: IESG
   o  Specification document(s): [[ this document ]]

   o  Token Endpoint Authorization Method Name: "client_secret_post"
   o  Change controller: IESG
   o  Specification document(s): [[ this document ]]

   o  Token Endpoint Authorization Method Name: "client_secret_basic"
   o  Change controller: IESG
   o  Specification document(s): [[ this document ]]


7.  Security Considerations

   Since requests to the client registration 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
   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].

   For clients that use redirect-based grant types such as
   "authorization_code" and "implicit", authorization servers SHOULD
   require clients to register their "redirect_uris".  Requiring clients
   to do so can help mitigate attacks where rogue actors inject and
   impersonate a validly registered client and intercept its
   authorization code or tokens through an invalid redirect URI.

   Public clients MAY register with an authorization server using this
   protocol, if the authorization server's policy allows them.  Public
   clients use a "none" value for the "token_endpoint_auth_method"
   metadata field and are generally used with the "implicit" grant type.
   Often these clients will be short-lived in-browser applications



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   requesting access to a user's resources and access is tied to a
   user's active session at the authorization server.  Since such
   clients often do not have long-term storage, it's possible that such
   clients would need to re-register every time the browser application
   is loaded.  Additionally, such clients may not have ample opportunity
   to unregister themselves using the delete action before the browser
   closes.  To avoid the resulting proliferation of dead client
   identifiers, an authorization server MAY decide to expire
   registrations for existing clients meeting certain criteria after a
   period of time has elapsed.

   Since different OAuth 2.0 grant types have different security and
   usage parameters, an authorization server MAY require separate
   registrations for a piece of software to support multiple grant
   types.  For instance, an authorization server might require that all
   clients using the "authorization_code" grant type make use of a
   client secret for the "token_endpoint_auth_method", but any clients
   using the "implicit" grant type do not use any authentication at the
   token endpoint.  In such a situation, a server MAY disallow clients
   from registering for both the "authorization_code" and "implicit"
   grant types simultaneously.  Similarly, the "authorization_code"
   grant type is used to represent access on behalf of an end user, but
   the "client_credentials" grant type represents access on behalf of
   the client itself.  For security reasons, an authorization server
   could require that different scopes be used for these different use
   cases, and as a consequence it MAY disallow these two grant types
   from being registered together by the same client.  In all of these
   cases, the authorization server would respond with an
   "invalid_client_metadata" error response.


8.  References

8.1.  Normative References

   [JWT]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", draft-ietf-oauth-json-web-token (work in
              progress), January 2014.

   [OAuth.JWT]
              Jones, M., Campbell, B., and C. Mortimore, "JSON Web Token
              (JWT) Profile for OAuth 2.0 Client Authentication and
              Authorization Grants", draft-ietf-oauth-jwt-bearer (work
              in progress), December 2013.

   [OAuth.Registration.Management]
              Richer, J., Jones, M., Bradley, J., Machulak, M., and P.
              Hunt, "OAuth 2.0 Dynamic Client Registration Management



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              Protocol", draft-ietf-oauth-dyn-reg-management (work in
              progress), February 2014.

   [OAuth.SAML2]
              Campbell, B., Mortimore, C., and M. Jones, "SAML 2.0
              Profile for OAuth 2.0 Client Authentication and
              Authorization Grants", draft-ietf-oauth-saml2-bearer (work
              in progress), December 2013.

   [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.

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

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [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.

8.2.  Informative References

   [OAuth.Registration.Metadata]
              Richer, J., Jones, M., Bradley, J., Machulak, M., and P.
              Hunt, "OAuth 2.0 Dynamic Client Registration Metadata",
              draft-ietf-oauth-dyn-reg-metadata (work in progress),
              February 2014.







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Appendix A.  Use Cases

   This appendix describes different ways that this specification can be
   utilized, including describing some of the choices that may need to
   be made.  Some of the choices are independent and can be used in
   combination, whereas some of the choices are interrelated.

A.1.  Open versus Protected Dynamic Client Registration

A.1.1.  Open Dynamic Client Registration

   Authorization servers that support open registration allow
   registrations to be made with no initial access token.  This allows
   all client software to register with the authorization server.

A.1.2.  Protected Dynamic Client Registration

   Authorization servers that support protected registration require
   that an initial access token be used when making registration
   requests.  While the method by which a client or developer receives
   this initial access token and the method by which the authorization
   server validates this initial access token are out of scope for this
   specification, a common approach is for the developer to use a manual
   pre-registration portal at the authorization server that issues an
   initial access token to the developer.

A.2.  Registration Without or With Software Statements

A.2.1.  Registration Without a Software Statement

   When a software statement is not used in the registration request,
   the authorization server must be willing to use client metadata
   values without them being signed (and thereby attested to) by any
   authority.  (Note that this choice is independent of the Open versus
   Protected choice, and that an initial access token is another
   possible form of attestation.)

A.2.2.  Registration With a Software Statement

   A software statement can be used in a registration request to provide
   attestation for a set of client metadata values for a piece of client
   software by an authority.  This can be useful when the authorization
   server wants to restrict registration to client software attested to
   by a set of authorities or when it wants to know that multiple
   registration requests refer to the same piece of client software.






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A.3.  Registration by the Client or the Developer

A.3.1.  Registration by the Client

   In some use cases, client software will dynamically register itself
   with an authorization server to obtain a Client ID and other
   information needed to interact with the authorization server.  In
   this case, no Client ID for the authorization server is packaged with
   the client software.

A.3.2.  Registration by the Developer

   In some cases, the developer (or development software being used by
   the developer) will pre-register the client software with the
   authorization server or a set of authorization servers.  In this
   case, the Client ID value(s) for the authorization server(s) can be
   packaged with the client software.

A.4.  Client ID per Client Instance or per Client Software

A.4.1.  Client ID per Client Software Instance

   In some cases, each deployed instance of a piece of client software
   will dynamically register and obtain distinct Client ID values.  This
   can be advantageous, for instance, if the code flow is being used, as
   it also enables each client instance to have its own client secret.
   This can be useful for native clients, which cannot maintain the
   secrecy of a client secret value packaged with the software, but
   which may be able to maintain the secrecy of a per-instance client
   secret.

A.4.2.  Client ID Shared between all Instances of Client Software

   In some cases, each deployed instance of a piece of client software
   will share a common Client ID value.  For instance, this is often the
   case for native client using implicit flow, when no client secret is
   involved.  Particular authorization servers might choose, for
   instance, to maintain a mapping between software statement values and
   Client ID values, and return the same Client ID value for all
   registration requests for a particular piece of software.  The
   circumstances under which an authorization server would do so, and
   the specific software statement characteristics required in this
   case, are beyond the scope of this specification.

A.5.  Stateful or Stateless Registration






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A.5.1.  Stateful Client Registration

   In some cases, authorization servers will maintain state about
   registered clients, typically indexing this state using the Client ID
   value.  This state would typically include the client metadata values
   associated with the client registration, and possibly other state
   specific to the authorization server's implementation.  When stateful
   registration is used, operations to support retrieving and/or
   updating this state may be supported, as described in the
   [OAuth.Registration.Management] specification.

A.5.2.  Stateless Client Registration

   In some cases, authorization servers will be implemented in a manner
   the enables them to not maintain any local state about registered
   clients.  One means of doing this is to encode all the registration
   state in the returned Client ID value, and possibly encrypting the
   state to the authorization server to maintain the confidentiality and
   integrity of the state.


Appendix B.  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, 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.


Appendix C.  Document History

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

   -16

   o  Replaced references to draft-jones-oauth-dyn-reg-metadata and
      draft-jones-oauth-dyn-reg-management with
      draft-ietf-oauth-dyn-reg-metadata and
      draft-ietf-oauth-dyn-reg-management.

   o  Addressed review comments by Phil Hunt and Tony Nadalin.

   -15



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   o  Partitioned the Dynamic Client Registration specification into
      core, metadata, and management specifications.  This built on work
      first published as draft-richer-oauth-dyn-reg-core-00 and
      draft-richer-oauth-dyn-reg-management-00.

   o  Added the ability to use Software Statements.  This built on work
      first published as draft-hunt-oauth-software-statement-00 and
      draft-hunt-oauth-client-association-00.

   o  Created the IANA OAuth Registration Client Metadata registry for
      registering Client Metadata values.

   o  Defined Client Instance term and stated that multiple instances
      can use the same Client ID value under certain circumstances.

   o  Rewrote the introduction.

   o  Rewrote the Use Cases appendix.

   -14

   o  Added software_id and software_version metadata fields

   o  Added direct references to RFC6750 errors in read/update/delete
      methods

   -13

   o  Fixed broken example text in registration request and in delete
      request

   o  Added security discussion of separating clients of different grant
      types

   o  Fixed error reference to point to RFC6750 instead of RFC6749

   o  Clarified that servers must respond to all requests to
      configuration endpoint, even if it's just an error code

   o  Lowercased all Terms to conform to style used in RFC6750

   -12

   o  Improved definition of Initial Access Token

   o  Changed developer registration scenario to have the Initial Access
      Token gotten through a normal OAuth 2.0 flow




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   o  Moved non-normative client lifecycle examples to appendix

   o  Marked differentiating between auth servers as out of scope

   o  Added protocol flow diagram

   o  Added credential rotation discussion

   o  Called out Client Registration Endpoint as an OAuth 2.0 Protected
      Resource

   o  Cleaned up several pieces of text

   -11

   o  Added localized text to registration request and response
      examples.

   o  Removed "client_secret_jwt" and "private_key_jwt".

   o  Clarified "tos_uri" and "policy_uri" definitions.

   o  Added the OAuth Token Endpoint Authentication Methods registry for
      registering "token_endpoint_auth_method" metadata values.

   o  Removed uses of non-ASCII characters, per RFC formatting rules.

   o  Changed "expires_at" to "client_secret_expires_at" and "issued_at"
      to "client_id_issued_at" for greater clarity.

   o  Added explanatory text for different credentials (Initial Access
      Token, Registration Access Token, Client Credentials) and what
      they're used for.

   o  Added Client Lifecycle discussion and examples.

   o  Defined Initial Access Token in Terminology section.

   -10

   o  Added language to point out that scope values are service-specific

   o  Clarified normative language around client metadata

   o  Added extensibility to token_endpoint_auth_method using absolute
      URIs





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   o  Added security consideration about registering redirect URIs

   o  Changed erroneous 403 responses to 401's with notes about token
      handling

   o  Added example for initial registration credential

   -09

   o  Added method of internationalization for Client Metadata values

   o  Fixed SAML reference

   -08

   o  Collapsed jwk_uri, jwk_encryption_uri, x509_uri, and
      x509_encryption_uri into a single jwks_uri parameter

   o  Renamed grant_type to grant_types since it's a plural value

   o  Formalized name of "OAuth 2.0" throughout document

   o  Added JWT Bearer Assertion and SAML 2 Bearer Assertion to example
      grant types

   o  Added response_types parameter and explanatory text on its use
      with and relationship to grant_types

   -07

   o  Changed registration_access_url to registration_client_uri

   o  Fixed missing text in 5.1

   o  Added Pragma: no-cache to examples

   o  Changed "no such client" error to 403

   o  Renamed Client Registration Access Endpoint to Client
      Configuration Endpoint

   o  Changed all the parameter names containing "_url" to instead use
      "_uri"

   o  Updated example text for forming Client Configuration Endpoint URL

   -06




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

   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



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   o  clarified signing and encryption URLs

   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-parameter inputs to endpoint

   o  Removed pull-based registration

   -00

   o  Imported original UMA draft specification








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Authors' Addresses

   Justin Richer
   The MITRE Corporation

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


   Phil Hunt
   Oracle Corporation

   Email: phil.hunt@yahoo.com



















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