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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, Ed.
Internet-Draft                                     The MITRE Corporation
Intended status: Standards Track                              J. Bradley
Expires: January 03, 2014                                  Ping Identity
                                                                M. Jones
                                                               Microsoft
                                                             M. Machulak
                                                    Newcastle University
                                                           July 02, 2013


             OAuth 2.0 Dynamic Client Registration Protocol
                      draft-ietf-oauth-dyn-reg-13

Abstract

   This specification defines an endpoint and protocol for dynamic
   registration of OAuth 2.0 clients at an authorization server and
   methods for the dynamically registered client to manage its
   registration through an OAuth 2.0 protected web API.

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 January 03, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Protocol Flow . . . . . . . . . . . . . . . . . . . . . .   4
     1.4.  Registration Tokens and Client Credentials  . . . . . . .   6
       1.4.1.  Credential Rotation . . . . . . . . . . . . . . . . .   7
   2.  Client Metadata . . . . . . . . . . . . . . . . . . . . . . .   7
     2.1.  Relationship Between Grant Types and Response Types . . .  10
     2.2.  Human Readable Client Metadata  . . . . . . . . . . . . .  11
   3.  Client Registration Endpoint  . . . . . . . . . . . . . . . .  12
     3.1.  Client Registration Request . . . . . . . . . . . . . . .  13
     3.2.  Client Registration Response  . . . . . . . . . . . . . .  15
   4.  Client Configuration Endpoint . . . . . . . . . . . . . . . .  15
     4.1.  Forming the Client Configuration Endpoint URL . . . . . .  15
     4.2.  Client Read Request . . . . . . . . . . . . . . . . . . .  16
     4.3.  Client Update Request . . . . . . . . . . . . . . . . . .  17
     4.4.  Client Delete Request . . . . . . . . . . . . . . . . . .  19
   5.  Responses . . . . . . . . . . . . . . . . . . . . . . . . . .  20
     5.1.  Client Information Response . . . . . . . . . . . . . . .  20
     5.2.  Client Registration Error Response  . . . . . . . . . . .  21
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22
     6.1.  OAuth Token Endpoint Authentication Methods Registry  . .  22
       6.1.1.  Registration Template . . . . . . . . . . . . . . . .  23
       6.1.2.  Initial Registry Contents . . . . . . . . . . . . . .  23
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  24
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .  26
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  27
   Appendix B.  Client Lifecycle Examples  . . . . . . . . . . . . .  27
     B.1.  Open Registration . . . . . . . . . . . . . . . . . . . .  28
     B.2.  Protected Registration  . . . . . . . . . . . . . . . . .  29
     B.3.  Developer Automation  . . . . . . . . . . . . . . . . . .  30
   Appendix C.  Document History . . . . . . . . . . . . . . . . . .  32
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  35

1.  Introduction

   In some use-case scenarios, it is desirable or necessary to allow
   OAuth 2.0 clients to obtain authorization from an OAuth 2.0
   authorization server without requiring the two parties to interact
   beforehand.  Nevertheless, for the authorization server to accurately
   and securely represent to end-users which client is seeking



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   authorization to access the end-user's resources, a method for
   automatic and unique registration of clients is needed.  The OAuth
   2.0 authorization framework does not define how the relationship
   between the client and the authorization server is initialized, or
   how a given client is assigned a unique client identifier.
   Historically, this has happened out-of-band from the OAuth 2.0
   protocol.  This draft provides a mechanism for a client to register
   itself with the authorization server, which can be used to
   dynamically provision a client identifier, and optionally a client
   secret.  Additionally, the mechanisms in this draft may can be used
   by a client developer to register the client with the authorization
   server in a programmatic fashion.

   As part of the registration process, this specification also defines
   a mechanism for the client to present the authorization server with a
   set of metadata, such as a display name and icon to be presented to
   the user during the authorization step.  This draft also provides a
   mechanism for the client to read and update this information after
   the initial registration action.  This draft protects these actions
   through the use of an OAuth 2.0 bearer access token that is issued to
   the client during registration explicitly for this purpose.

1.1.  Notational Conventions

   The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
   'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this
   document are to be interpreted as described in [RFC2119].

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

1.2.  Terminology

   This specification uses the terms "Access Token", "Refresh Token",
   "Authorization Code", "Authorization Grant", "Authorization Server",
   "Authorization Endpoint", "Client", "Client Identifier", "Client
   Secret", "Protected Resource", "Resource Owner", "Resource Server",
   and "Token Endpoint" defined by OAuth 2.0 [RFC6749].

   This specification defines the following additional terms:

   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 are obtained are out of scope for
      this specification.






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   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.
   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.
   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.

1.3.  Protocol Flow

   (preamble)

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



   Figure 1: Abstract Protocol Flow





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   The abstract OAuth 2.0 Client dynamic registration flow illustrated
   in Figure 1 describes the interaction between the client or developer
   and the two endpoints 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 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.
   (B)
      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.
   (C)
      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, a URI pointing to the client
      configuration endpoint, and a registration access token to be used
      when calling the client configuration endpoint.
   (D)
      The client or developer optionally calls the client configuration
      endpoint with a read or update request using the registration
      access token issued in (C).  An update request contains all of the
      client's registered metadata.
   (E)
      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 (C) for all subsequent
      calls to the client configuration endpoint.
   (F)
      The client or developer optionally calls the client configuration
      endpoint with a delete request using the registration access token
      issued in (C).
   (G)
      The authorization server deprovisions the client and responds with
      a confirmation that the deletion has taken place.

   Further discussion of possible example lifecycles are found in the
   Appendix to this specification, Client Lifecycle Examples
   (Appendix B).





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1.4.  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 between 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 should 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 and should not be shared between instances of a client
      (otherwise, one instance could change or delete registration
      values for all instances of the client).  The registration access
      token can be rotated through the use of the client read and update
      methods on the client configuration endpoint.  The registration
      access token should be used only at the client configuration
      endpoint.
   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 and update methods on the
      client configuration endpoint.  The client credentials can not be
      used for authentication at the client registration endpoint or at
      the client configuration endpoint.




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1.4.1.  Credential Rotation

   The Authorization Server MAY rotate the client's registration access
   token and/or client credentials (such as a "client_secret")
   throughout the lifetime of the client.  The client is informed of the
   changed values changing by making either read or update requests to
   the client configuration endpoint, and the new values of the
   registration access token and the client credentials will 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 which
   point the new registration access token is returned to the client and
   the old registration access token SHOULD be discarded by both
   parties.  If the registration access token to expire or be rotated
   outside of such requests, the client or developer may be locked out
   of managing the client's configuration.

2.  Client Metadata

   Clients generally have an array of metadata associated with their
   unique client identifier at the authorization server.  These can
   range from human-facing display strings, such as a client name, to
   items that impact the security of the protocol, such as the list of
   valid redirect URIs.

   The client metadata values serve two parallel purposes in the overall
   OAuth 2.0 dynamic client registration protocol:

   o  the client requesting its desired values for each parameter to the
      authorization server in a register (Section 3.1) or update
      (Section 4.3) request, and
   o  the authorization server informing the client of the current
      values of each parameter that the client has been registered to
      use through a client information response (Section 5.1).

   An authorization server MAY override any value that a client requests
   during the registration process (including any omitted values) and
   replace the requested value with a default at the server's
   discretion.  The authorization server SHOULD provide documentation
   for any fields that it requires to be filled in by the client or to
   have particular values or formats.  An authorization server MAY
   ignore the values provided by the client for any field in this list.

   Extensions and profiles of this specification MAY expand this list,
   and authorization servers MUST accept all fields in this list.  The
   authorization server MUST ignore any additional parameters sent by
   the Client that it does not understand.



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   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.
   client_name
      Human-readable name of the client to be presented to the user.  If
      omitted, the authorization server MAY display the raw "client_id"
      value to the user instead.  It is RECOMMENDED that clients always
      send this field.  The value of this field MAY be internationalized
      as described in Human Readable Client Metadata (Section 2.2).
   client_uri
      URL of the homepage of the client.  If present, the server SHOULD
      display this URL to the end user in a clickable fashion.  It is
      RECOMMENDED that clients always send this field.  The value of
      this field MUST point to a valid web page.  The value of this
      field MAY be internationalized as described in Human Readable
      Client Metadata (Section 2.2).
   logo_uri
      URL that references a logo for the client.  If present, the server
      SHOULD display this image to the end user during approval.  The
      value of this field MUST point to a valid image file.  The value
      of this field MAY be internationalized as described in Human
      Readable Client Metadata (Section 2.2).
   contacts
      Array of email addresses for people responsible for this client.
      The authorization server MAY make these addresses available to end
      users for support requests for the client.  An authorization
      server MAY use these email addresses as identifiers for an
      administrative page for this client.
   tos_uri
      URL that points to a human-readable Terms of Service document for
      the client.  The Authorization Server SHOULD display this URL to
      the end-user if it is given.  The Terms of Service usually
      describe a contractual relationship between the end-user and the
      client that the end-user accepts when authorizing the client.  The
      value of this field MUST point to a valid web page.  The value of
      this field MAY be internationalized as described in Human Readable
      Client Metadata (Section 2.2).
   policy_uri









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      URL that points to a human-readable Policy document for the
      client.  The authorization server SHOULD display this URL to the
      end-user if it is given.  The policy usually describes how an end-
      user's data will be used by the client.  The value of this field
      MUST point to a valid web page.  The value of this field MAY be
      internationalized as described in Human Readable Client Metadata
      (Section 2.2).
   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 6.1.  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.
   scope
      Space separated list of scope values (as described in OAuth 2.0
      Section 3.3 [RFC6749]) that the client can use when requesting
      access tokens.  The semantics of values in this list is service
      specific.  If omitted, an authorization server MAY register a
      Client with a default set of scopes.
   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].





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      *  "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.
   jwks_uri
      URL for the Client's JSON Web Key Set [JWK] document representing
      the client's public keys.  The value of this field MUST point to a
      valid JWK Set. These keys MAY be used for higher level protocols
      that require signing or encryption.

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.





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   +-------------------------------------------------+-----------------+
   | 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.

2.2.  Human Readable Client Metadata

   Human-readable client metadata values and client metadata values that
   reference human-readable values MAY be represented in multiple
   languages and scripts.  For example, the values of fields such as
   "client_name", "tos_uri", "policy_uri", "logo_uri", and "client_uri"
   might have multiple locale-specific values in some client
   registrations.

   To specify the languages and scripts, BCP47 [RFC5646] language tags
   are added to client metadata member names, delimited by a #
   character.  Since JSON member names are case sensitive, it is
   RECOMMENDED that language tag values used in Claim Names be spelled
   using the character case with which they are registered in the IANA
   Language Subtag Registry [IANA.Language].  In particular, normally
   language names are spelled with lowercase characters, region names
   are spelled with uppercase characters, and languages are spelled with
   mixed case characters.  However, since BCP47 language tag values are
   case insensitive, implementations SHOULD interpret the language tag
   values supplied in a case insensitive manner.  Per the
   recommendations in BCP47, language tag values used in metadata member
   names should only be as specific as necessary.  For instance, using
   "fr" might be sufficient in many contexts, rather than "fr-CA" or
   "fr-FR".

   For example, a client could represent its name in English as
   ""client_name#en": "My Client"" and its name in Japanese as
   ""client_name#ja-Jpan-JP":
   "\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D"" within the same
   registration request.  The authorization server MAY display any or



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   all of these names to the resource owner during the authorization
   step, choosing which name to display based on system configuration,
   user preferences or other factors.

   If any human-readable field is sent without a language tag, parties
   using it MUST NOT make any assumptions about the language, character
   set, or script of the string value, and the string value MUST be used
   as-is wherever it is presented in a user interface.  To facilitate
   interoperability, it is RECOMMENDED that clients and servers use a
   human-readable field without any language tags in addition to any
   language-specific fields, and it is RECOMMENDED that any human-
   readable fields sent without language tags contain values suitable
   for display on a wide variety of systems.

   Implementer's Note: Many JSON libraries make it possible to reference
   members of a JSON object as members of an object construct in the
   native programming environment of the library.  However, while the
   "#" character is a valid character inside of a JSON object's member
   names, it is not a valid character for use in an object member name
   in many programming environments.  Therefore, implementations will
   need to use alternative access forms for these claims.  For instance,
   in JavaScript, if one parses the JSON as follows, "var j =
   JSON.parse(json);", then the member "client_name#en-us" can be
   accessed using the JavaScript syntax "j["client_name#en-us"]".

3.  Client Registration Endpoint

   The client registration endpoint is an OAuth 2.0 endpoint defined in
   this document that is designed to allow a client to 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].

   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.




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   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.

   To allow the registrant to manage the client's information, the
   client registration endpoint issues a request access token as an
   OAuth 2.0 Bearer Token [RFC6750] to securely authorize calls to the
   client configuration endpoint (Section 4).

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

3.1.  Client Registration Request

   This operation registers a new client to the authorization server.
   The authorization server assigns this client a unique client
   identifier, optionally assigns a client secret, and associates the
   metadata given in the request with the issued client identifier.  The
   request includes any parameters described in Client Metadata
   (Section 2) that the client wishes to specify for itself during the
   registration.  The authorization server MAY provision default values
   for any items omitted in the client metadata.

   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:

   Following is a non-normative example request (with line wraps for
   display purposes only):














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   POST /register HTTP/1.1
   Content-Type: application/json
   Accept: application/json
   Host: server.example.com

   {
    "redirect_uris":["https://client.example.org/callback",
       "https://client.example.org/callback2"],
    "client_name":"My Example Client",
    "client_name#ja-Jpan-JP":
       "\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D",
    "token_endpoint_auth_method":"client_secret_basic",
    "scope":"read write dolphin",
    "logo_uri":"https://client.example.org/logo.png",
    "jwks_uri":"https://client.example.org/my_public_keys.jwks"
   }


   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:

   Following is a non-normative example request (with line wraps for
   display purposes only):

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

   {
    "redirect_uris":["https://client.example.org/callback",
       "https://client.example.org/callback2"],
    "client_name":"My Example Client",
    "client_name#ja-Jpan-JP":
       "\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D",
    "token_endpoint_auth_method":"client_secret_basic",
    "scope":"read write dolphin",
    "logo_uri":"https://client.example.org/logo.png",
    "jwks_uri":"https://client.example.org/my_public_keys.jwks"
   }




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3.2.  Client Registration Response

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

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

4.  Client 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
   endpoint is communicated to the client through the
   "registration_client_uri" member of the Client Information Response
   (Section 5.1).  The client MUST use its registration access token in
   all calls to this endpoint as an OAuth 2.0 Bearer Token [RFC6750].

   Operations on this endpoint are switched through the use of different
   HTTP methods [RFC2616].  If an authorization server does not support
   a particular method on the client configuration endpoint, it MUST
   respond with the appropriate error code.

4.1.  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 (Section 5.1).  The authorization server MUST
   NOT expect the client to construct or discover this URL on its own.
   The client MUST use the URL as given by the server and MUST NOT
   construct this URL from component pieces.















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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 which 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.

4.2.  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.

   Following is a non-normative example request (with line wraps for
   display purposes only):

   GET /register/s6BhdRkqt3 HTTP/1.1
   Accept: application/json
   Host: server.example.com
   Authorization: Bearer reg-23410913-abewfq.123483
















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   Upon successful read of the information for a currently active
   client, the authorization server responds with an HTTP 200 OK with
   content type of "application/json" and a payload as described in
   Client Information Response (Section 5.1).  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 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 does not have permission to read its record, the server
   MUST return an HTTP 403 Forbidden.

4.3.  Client Update Request

   This operation updates a previously-registered client with new
   metadata at the authorization server.  This request is authenticated
   by the registration access token issued to the client.

   The client sends an HTTP PUT to the client configuration endpoint
   with a content type of "application/json".  The HTTP entity payload
   is a JSON [RFC4627] document consisting of a JSON object and all
   parameters as top- level members of that JSON object.

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

   Valid values of client metadata fields in this request MUST replace,
   not augment, the values previously associated with this client.
   Omitted fields MUST be treated as null or empty values by the server.

   The client MUST include its "client_id" field in the request, and it
   MUST be the same as its currently-issued client identifier.  If the
   client includes 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.




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   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:

   Following is a non-normative example request (with line wraps for
   display purposes only):

   PUT /register/s6BhdRkqt3 HTTP/1.1
   Accept: application/json
   Host: server.example.com
   Authorization: Bearer reg-23410913-abewfq.123483

   {
    "client_id":"s6BhdRkqt3",
    "client_secret": "cf136dc3c1fc93f31185e5885805d",
    "redirect_uris":["https://client.example.org/callback",
       "https://client.example.org/alt"],
    "scope": "read write dolphin",
    "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"
   }


   Upon successful update, the authorization server responds with an
   HTTP 200 OK Message with content type "application/json" and a
   payload as described in Client Information Response (Section 5.1).
   Some values in the response, including the "client_secret" and
   r"egistration_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 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 is not allowed to update its records, the server MUST
   respond with HTTP 403 Forbidden.

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

4.4.  Client Delete Request

   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.

   Following is a non-normative example request (with line wraps for
   display purposes only):

   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.
   The authorization server SHOULD immediately invalidate all existing
   authorization grants and currently-active tokens associated with this
   client.

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

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

   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 delete itself, the server MUST
   respond with HTTP 403 Forbidden.

   Following is a non-normative example response:





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



5.  Responses

   In response to certain requests from the client to either the client
   registration endpoint or the client configuration endpoint as
   described in this specification, the authorization server sends the
   following response bodies.

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 also
   contains the fully qualified URL to the client configuration endpoint
   for this specific client that the client may use to obtain and update
   information about itself.  The response also contains a registration
   access token that is to be used by the client to perform subsequent
   operations at the client configuration endpoint.

   client_id
      REQUIRED.  The unique client identifier, MUST NOT be currently
      valid for any other registered client.
   client_secret
      OPTIONAL.  The client secret.  If issued, this MUST be unique for
      each "client_id".  This value is used by confidential clients to
      authenticate to the token endpoint as described in OAuth 2.0
      Section 2.3.1.
   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.
   registration_access_token
      REQUIRED.  Access token that is used at the client configuration
      endpoint to perform subsequent operations upon the client
      registration.
   registration_client_uri
      REQUIRED.  The fully qualified URL of the client configuration
      endpoint for this client.  The client MUST use this URL as given
      when communicating with the client configuration endpoint.



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

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

   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"]
    "scope": "read write dolphin",
    "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"
   }


5.2.  Client Registration Error Response

   When an OAuth 2.0 error condition occurs, such as the client
   presenting an invalid registration access token, the authorization
   server returns an error response appropriate to the OAuth 2.0 token
   type.  For the registration access token, which is an OAuth 2.0
   bearer token, this error response is defined in Section 3 of OAuth
   2.0 Bearer Token Usage [RFC6750].





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   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
      The error code, a single ASCII string.
   error_description
      A human-readable text description of the error for debugging.

   This specification defines the following error codes:

   invalid_redirect_uri
      The value of one or more "redirect_uris" is invalid.
   invalid_client_metadata
      The value of one of the client metadata (Section 2) fields is
      invalid and the server has rejected this request.  Note that an
      Authorization server MAY choose to substitute a valid value for
      any requested parameter of a client's metadata.
   invalid_client_id
      The value of "client_id" does not match the one assigned to this
      client.

   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 of http://sketchy.example.com
      is not allowed for this server."
   }


6.  IANA Considerations

6.1.  OAuth Token Endpoint Authentication Methods Registry

   This specification establishes the OAuth Token Endpoint
   Authentication Methods registry.





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   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.

6.1.1.  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.

   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 OAuth Token Endpoint Authentication Methods registry's initial
   contents are:

   o  Token Endpoint Authorization Method name: "none"
   o  Change controller: IETF



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

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

   o  Token Endpoint Authorization Method name: "client_secret_basic"
   o  Change controller: IETF
   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].

   Since the client configuration endpoint is an OAuth 2.0 protected
   resource, it SHOULD have some rate limiting on failures to prevent
   the registration access token from being disclosed though repeated
   access attempts.

   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.

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





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   In a situation where the authorization server is supporting open
   client registration, it must be extremely careful with any URL
   provided by the client that will be displayed to the user (e.g.
   "logo_uri", "tos_uri", "client_uri", and "policy_uri").  For
   instance, a rogue client could specify a registration request with a
   reference to a drive-by download in the "policy_uri".  The
   authorization server SHOULD check to see if the "logo_uri",
   "tos_uri", "client_uri", and "policy_uri" have the same host and
   scheme as the those defined in the array of "redirect_uris" and that
   all of these resolve to valid web pages.

   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 or updating 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 OAuth 2.0
   Bearer Token Usage [RFC6750].

   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.  To prevent accidental
   disclosure from such an erroneous situation, 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).

   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
   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



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   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 (Section 5.2).

8.  Normative References

   [IANA.Language]
              Internet Assigned Numbers Authority (IANA), "Language
              Subtag Registry", 2005.

   [JWK]      Jones, M., "JSON Web Key (JWK)", draft-ietf-jose-json-web-
              key (work in progress), May 2013.

   [OAuth.JWT]
              Jones, M., Campbell, B., and C. Mortimore, "JSON Web Token
              (JWT) Bearer Token Profiles for OAuth 2.0", draft-ietf-
              oauth-jwt-bearer (work in progress), March 2013.

   [OAuth.SAML2]
              Campbell, B., Mortimore, C., and M. Jones, "SAML 2.0
              Bearer Assertion Profiles for OAuth 2.0", draft-ietf-
              oauth-saml2-bearer (work in progress), March 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.



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   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [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.

   [RFC5646]  Phillips, A. and M. Davis, "Tags for Identifying
              Languages", BCP 47, RFC 5646, September 2009.

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

   [RFC6749]  Hardt, D., "The OAuth 2.0 Authorization Framework", RFC
              6749, October 2012.

   [RFC6750]  Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
              Framework: Bearer Token Usage", RFC 6750, October 2012.

Appendix A.  Acknowledgments

   The authors thank the OAuth Working Group, the User-Managed Access
   Working Group, and the OpenID Connect Working Group participants for
   their input to this document.  In particular, the following
   individuals have been instrumental in their review and contribution
   to various versions of this document: Amanda Anganes, 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, Nat Sakimura,
   Christian Scholz, and Hannes Tschofenig.

Appendix B.  Client Lifecycle Examples

   In the OAuth 2.0 specification [RFC6749], a client is identified by
   its own unique Client identifier ("client_id") at each authorization
   server that it associates with.  Dynamic registration as defined in
   this document is one way for a client to get a client identifier and
   associate a set of metadata with that identifier.  Lack of such a



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   client identifier is the expected trigger for a client registration
   operation.

   In many cases, this client identifier is a unique, pairwise
   association between a particular running instance of a piece of
   client software and a particular running instance of an authorization
   server software.  In particular:

   o  A single instance of client software (such as a Web server)
      talking to multiple authorization servers will need to register
      with each authorization server separately, creating a distinct
      client identifier with each authorization server.  The client can
      not make any assumption that the authorization servers are
      correlating separate registrations of the client software together
      without further profiles and extensions to this specification
      document.  The means by which a client discovers and
      differentiates between multiple authorization servers is out of
      scope for this specification.
   o  Multiple instances of client software (such as a native
      application installed on multiple devices simultaneously) talking
      to the same authorization server will need to each register with
      that authorization server separately, creating a distinct client
      identifier for each copy of the application.  The authorization
      server cannot make any assumption of correlation between these
      clients without further specifications, profiles, and extensions
      to this specification.  The client can not make any assumption
      that the authorization server will correlate separate
      registrations of the client software together without further
      profiles and extensions to this specification document.

   A client identifier (and its associated credentials) could also be
   shared between multiple instances of a client.  Mechanisms for
   sharing client identifiers between multiple instances of a piece of
   software (either client or authorization server) are outside the
   scope of this specification, as it is expected that every successful
   registration request (Section 3.1) results in the issuance of a new
   client identifier.

   There are several patterns of OAuth client registration that dynamic
   registration protocol can enable.  The following non-normative
   example lifecycle descriptions are not intended to be an exhaustive
   list.  It is assumed that the authorization server supports the
   dynamic registration protocol and that all necessary discovery steps
   (which are out of scope for this specification) have already been
   performed.

B.1.  Open Registration




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   Open registration, with no authorization required on the client
   registration endpoint, works as follows:

   a.  A client needs to get OAuth 2.0 tokens from an authorization
       server, but the client does not have a client identifier for that
       authorization server.
   b.  The client sends an HTTP POST request to the client registration
       endpoint at the authorization server and includes its metadata.
   c.  The authorization server issues a client identifier and returns
       it to the client along with a registration access token and a
       reference to the client's client configuration endpoint.
   d.  The client stores the returned response from the authorization
       server.  At a minimum, it should remember the values of
       "client_id", "client_secret" (if present),
       "registration_access_token", and "registration_client_uri".
   e.  The client uses the its "client_id" and "client_secret" (if
       provided) to request OAuth 2.0 tokens using any valid OAuth 2.0
       flow for which it is authorized.
   f.  If the client's "client_secret" expires or otherwise stops
       working, the client sends an HTTP GET request to the
       "registration_client_uri" with the "registration_access_token" as
       its authorization.  This response will contain the client's
       refreshed "client_secret" along with any changed metadata values.
       Its "client_id" will remain the same.
   g.  If the client needs to update its configuration on the
       authorization server, it sends an HTTP PUT request to the
       "registration_client_uri" with the "registration_access_token" as
       its authorization.  This response will contain the client's
       changed metadata values.  Its "client_id" will remain the same.
   h.  If the client is uninstalled or otherwise deprovisioned, it can
       send an HTTP DELETE request to the "registration_client_uri" with
       the "registration_access_token" as its authorization.  This will
       effectively deprovision the client from the authorization server.

B.2.  Protected Registration

   An authorization server may require an initial access token for
   requests to its registration endpoint.  While the method by which a
   client 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.  This allows
   the developer to package the initial access token with different
   instances of the client application.  While each copy of the
   application would get its own client identifier (and registration
   access token), all instances of the application would be tied back to
   the developer by their shared use of this initial access token.



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   a.  A developer is creating a client to use an authorization server
       and knows that instances of the client will dynamically register
       at runtime, but that the authorization server requires
       authorization at the registration endpoint.
   b.  The developer visits a manual pre-registration page at the
       authorization server and is issued an initial access token in the
       form of an OAuth 2.0 Bearer Token [RFC6750].
   c.  The developer packages that token with all instances of the
       client application.
   d.  The client needs to get OAuth 2.0 tokens from an authorization
       server, but the client does not have a client identifier for that
       authorization server.
   e.  The client sends an HTTP POST request to the client registration
       endpoint at the authorization server with its metadata, and the
       initial access token as its authorization.
   f.  The authorization server issues a client identifier and returns
       it to the client along with a registration access token and a
       reference to the client's client configuration endpoint.
   g.  The client stores the returned response from the authorization
       server.  At a minimum, it should know the values of "client_id",
       "client_secret" (if present), "registration_access_token", and
       "registration_client_uri".
   h.  The client uses the its "client_id" and "client_secret" (if
       provided) to request OAuth 2.0 tokens using any supported OAuth
       2.0 flow for which this client is authorized.
   i.  If the client's "client_secret" expires or otherwise stops
       working, the client sends an HTTP GET request to the
       "registration_client_uri" with the "registration_access_token" as
       its authorization.  This response will contain the client's
       refreshed "client_secret" along with any metadata values
       registered to that client, some of which may have changed.  Its
       "client_id" will remain the same.
   j.  If the client needs to update its configuration on the
       authorization server, it sends an HTTP PUT request to the
       "registration_client_uri" with the "registration_access_token" as
       its authorization.  The response will contain the client's
       changed metadata values.  Its "client_id" will remain the same.
   k.  If the client is uninstalled or otherwise deprovisioned, it can
       send an HTTP DELETE request to the "registration_client_uri" with
       the "registration_access_token" as its authorization.  This will
       effectively deprovision the client from the Authorization Server.

B.3.  Developer Automation

   The dynamic registration protocol can also be used in place of a
   manual registration portal, for instance as part of an automated
   build and deployment process.  In this scenario, the authorization
   server may require an initial access token for requests to its



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   registration endpoint, as described in Protected Registration
   (Appendix B.2).  However, here the developer manages the client's
   registration instead of the client itself.  Therefore, the initial
   registration token and registration access token all remain with the
   developer.  The developer packages the client identifier with the
   client as part of the client's build process.

   a.  A developer is creating a client to use an authorization server
       and knows that instances of the client will not dynamically
       register at runtime.
   b.  If required for registrations at the authorization server, the
       developer performs an OAuth 2.0 authorization of his build
       environment against the authorization server using any valid
       OAuth 2.0 flow.  The authorization server and is issues an
       initial access token to the developer's build environment in the
       form of an OAuth 2.0 Bearer Token [RFC6750].
   c.  The developer configures his build environment to send an HTTP
       POST request to the client registration endpoint at the
       authorization server with the client's metadata, using the
       initial access token obtained the previous step as an OAuth 2.0
       Bearer Token [RFC6750].
   d.  The authorization server issues a client identifier and returns
       it to the developer along with a registration access token and a
       reference to the client's client configuration endpoint.
   e.  The developer packages the client identifier with the client and
       stores the "registration_access_token", and
       "registration_client_uri" in the deployment system.
   f.  The client uses the its "client_id" and "client_secret" (if
       provided) to request OAuth 2.0 tokens using any supported OAuth
       2.0 flow.
   g.  If the client's "client_secret" expires or otherwise stops
       working, the developer's deployment system sends an HTTP GET
       request to the "registration_client_uri" with the
       "registration_access_token" as its authorization.  This response
       will contain the client's refreshed "client_secret" along with
       any changed metadata values.  Its "client_id" will remain the
       same.  These new values will then be packaged and shipped to or
       retrieved by instances of the client, if necessary.
   h.  If the developer needs to update its configuration on the
       authorization server, the deployment system sends an HTTP PUT
       request to the "registration_client_uri" with the
       "registration_access_token" as its authorization.  This response
       will contain the client's changed metadata values.  Its
       "client_id" will remain the same.  These new values will then be
       packaged and shipped to or retrieved by instances of the client,
       if necessary.
   i.  If the client is deprovisioned, the developer's deployment system
       can send an HTTP DELETE request to the "registration_client_uri"



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       with the "registration_access_token" as its authorization.  This
       will effectively deprovision the client from the authorization
       server and prevent any instances of the client from functioning.

Appendix C.  Document History

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

   -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
   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.



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   -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
   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

   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.



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   o  Added clarifying text to PUT and POST requests to specify JSON in
      the body.
   o  Added Editor's Note to DELETE operation about its inclusion.
   o  Added Editor's Note to registration_access_url about alternate
      syntax proposals.

   -05

   o  changed redirect_uri and contact to lists instead of space
      delimited strings
   o  removed operation parameter
   o  added _links structure
   o  made client update management more RESTful
   o  split endpoint into three parts
   o  changed input to JSON from form-encoded
   o  added READ and DELETE operations
   o  removed Requirements section
   o  changed token_endpoint_auth_type back to
      token_endpoint_auth_method to match OIDC who changed to match us

   -04

   o  removed default_acr, too undefined in the general OAuth2 case
   o  removed default_max_auth_age, since there's no mechanism for
      supplying a non-default max_auth_age in OAuth2
   o  clarified signing and encryption URLs
   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




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   -01

   o  Merged UMA and OpenID Connect registrations into a single document
   o  Changed to form-paramter inputs to endpoint
   o  Removed pull-based registration

   -00

   o  Imported original UMA draft specification

Authors' Addresses

   Justin Richer (editor)
   The MITRE Corporation

   Email: jricher@mitre.org


   John Bradley
   Ping Identity

   Email: ve7jtb@ve7jtb.com


   Michael B. Jones
   Microsoft

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


   Maciej Machulak
   Newcastle University

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















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