[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 09 10 11 12 13 14 15 16 17 18 19

OAuth Working Group                                            J. Richer
Internet-Draft                                     The MITRE Corporation
Intended status: Standards Track                                M. Jones
Expires: February 6, 2015                                      Microsoft
                                                              J. Bradley
                                                           Ping Identity
                                                             M. Machulak
                                                    Newcastle University
                                                                 P. Hunt
                                                      Oracle Corporation
                                                          August 5, 2014


             OAuth 2.0 Dynamic Client Registration Protocol
                      draft-ietf-oauth-dyn-reg-19

Abstract

   This specification defines mechanisms for dynamically registering
   OAuth 2.0 clients with authorization servers.  Registration requests
   send a set of desired client metadata values to the authorization
   server and the resulting registration responses return a client
   identifier to use at the authorization server and the client metadata
   values registered for the client.  The client can then use this
   registration information to communicate with the authorization server
   using the OAuth 2.0 protocol.  This specification also defines a set
   of common client metadata fields and values for clients to use during
   registration.

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 February 6, 2015.






Richer, et al.          Expires February 6, 2015                [Page 1]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 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
   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   4
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.3.  Protocol Flow . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Client Metadata . . . . . . . . . . . . . . . . . . . . . . .   6
     2.1.  Relationship between Grant Types and Response Types . . .  10
     2.2.  Human Readable Client Metadata  . . . . . . . . . . . . .  10
     2.3.  Software Statement  . . . . . . . . . . . . . . . . . . .  12
   3.  Client Registration Endpoint  . . . . . . . . . . . . . . . .  12
     3.1.  Client Registration Request . . . . . . . . . . . . . . .  13
     3.2.  Client Registration Response  . . . . . . . . . . . . . .  16
   4.  Responses . . . . . . . . . . . . . . . . . . . . . . . . . .  16
     4.1.  Client Information Response . . . . . . . . . . . . . . .  16
     4.2.  Client Registration Error Response  . . . . . . . . . . .  17
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
     5.1.  OAuth Dynamic Registration Client Metadata Registry . . .  19
       5.1.1.  Registration Template . . . . . . . . . . . . . . . .  20
       5.1.2.  Initial Registry Contents . . . . . . . . . . . . . .  20
     5.2.  OAuth Token Endpoint Authentication Methods Registry  . .  22
       5.2.1.  Registration Template . . . . . . . . . . . . . . . .  23
       5.2.2.  Initial Registry Contents . . . . . . . . . . . . . .  23
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  24
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  27
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  27
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  28
   Appendix A.  Use Cases  . . . . . . . . . . . . . . . . . . . . .  28
     A.1.  Open versus Protected Dynamic Client Registration . . . .  28
       A.1.1.  Open Dynamic Client Registration  . . . . . . . . . .  28
       A.1.2.  Protected Dynamic Client Registration . . . . . . . .  29
     A.2.  Registration Without or With Software Statements  . . . .  29
       A.2.1.  Registration Without a Software Statement . . . . . .  29



Richer, et al.          Expires February 6, 2015                [Page 2]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


       A.2.2.  Registration With a Software Statement  . . . . . . .  29
     A.3.  Registration by the Client or Developer . . . . . . . . .  29
       A.3.1.  Registration by the Client  . . . . . . . . . . . . .  29
       A.3.2.  Registration by the Developer . . . . . . . . . . . .  29
     A.4.  Client ID per Client Instance or per Client Software  . .  30
       A.4.1.  Client ID per Client Software Instance  . . . . . . .  30
       A.4.2.  Client ID Shared Among All Instances of Client
               Software  . . . . . . . . . . . . . . . . . . . . . .  30
     A.5.  Stateful or Stateless Registration  . . . . . . . . . . .  30
       A.5.1.  Stateful Client Registration  . . . . . . . . . . . .  30
       A.5.2.  Stateless Client Registration . . . . . . . . . . . .  30
   Appendix B.  Acknowledgments  . . . . . . . . . . . . . . . . . .  31
   Appendix C.  Document History . . . . . . . . . . . . . . . . . .  31
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  36

1.  Introduction

   In order for an OAuth 2.0 client to utilize an OAuth 2.0
   authorization server, the client needs specific information to
   interact with the server, including an OAuth 2.0 client identifier to
   use 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 is digitally
   signed or MACed; in the case of a software statement, the issuer is
   vouching for the validity of the data about the client.

   Traditionally, registration of a client with an authorization server
   is performed manually.  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.  Multiple
   applications using OAuth 2.0 have previously developed mechanisms for
   accomplishing such registrations.  This specficiation generalizes the
   registration mechanisms defined by the OpenID Connect Dynamic Client
   Registration 1.0 [OpenID.Registration] specification and used by the
   User Managed Access (UMA) Profile of OAuth 2.0
   [I-D.hardjono-oauth-umacore] specification in a way that is
   compatible with both, while being applicable to a wider set of OAuth
   2.0 use cases.






Richer, et al.          Expires February 6, 2015                [Page 3]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


1.1.  Notational Conventions

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

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

1.2.  Terminology

   This specification uses the terms "access token", "authorization
   code", "authorization endpoint", "authorization grant",
   "authorization server", "client", "client identifier", "client
   secret", "grant type", "protected resource", "redirection URI",
   "refresh token", "resource owner", "resource server", "response
   type", and "token endpoint" defined by OAuth 2.0 [RFC6749] and 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.
   Client Instance
      A deployed instance of a piece of client software.
   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 to a developer or client 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.  Use
      of an initial access token is required when the authorization
      server limits the parties that can register a client.
   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




Richer, et al.          Expires February 6, 2015                [Page 4]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


      publisher may be working with many different deployment
      organizations.
   Software API Deployment
      A deployed 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 as well as a client registration endpoint.
      The means by which endpoints are obtained 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.  In some cases a
      software API publisher and a client developer may be the same
      organization.
   Software Statement
      Digitally signed or MACed JSON Web Token (JWT) [JWT] that asserts
      metadata values about the client software.  In some cases, a
      software statement will be issued directly by the organization or
      developer that creates the client software.  In other cases, a
      software statement will be issued by a third party organization
      for use by the organization or developer that creates the client
      software.  In both cases, the trust relationship the authorization
      server has with the issuer of the software statement is intended
      to be used as an input to the evaluation of whether the
      registration request is accepted.  A software statement can be
      presented to an authorization server as part of a client
      registration request.

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




Richer, et al.          Expires February 6, 2015                [Page 5]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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 the client's desired registration metadata, optionally
      including the initial access token from (A) if one is required by
      the authorization server.
   (D)  The authorization server registers the client and returns the
      client's registered metadata, a client identifier that is unique
      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 client
   identifier at an authorization server, such as the list of valid
   redirection URIs or a display name.

   The client metadata values are used in two ways:

   o  as input values to registration requests, and
   o  as output values in registration responses.

   The following client metadata fields are defined by this
   specification.  The implementation and use of all client metadata
   fields is OPTIONAL, unless stated otherwise.

   redirect_uris
      Array of redirection URI values for use in redirect-based flows
      such as the authorization code and implicit flows.  As required by
      Section 2 of OAuth 2.0 [RFC6749], clients using flows with
      redirection MUST register their redirection URI values.
      Authorization servers that support dynamic registration for
      redirect-based flows MUST implement support for this metadata
      value.
   token_endpoint_auth_method




Richer, et al.          Expires February 6, 2015                [Page 6]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


      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 established in Section 5.2.
      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.
   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.  If omitted, the default is
      that the client will use only the "authorization_code" Grant Type.
   response_types
      Array of the OAuth 2.0 response types that the client may use.
      These response types are defined as follows:





Richer, et al.          Expires February 6, 2015                [Page 7]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


      *  "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.  If omitted, the
      default is that the client will use only the "code" response type.
   client_name
      Human-readable name of the client to be presented to the user
      during authorization.  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 Section 2.2.
   client_uri
      URL of a web page providing information about 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 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
      Section 2.2.
   scope
      Space separated list of scope values (as described in Section 3.3
      of OAuth 2.0 [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.
   contacts
      Array of strings representing ways to contact people responsible
      for this client, typically email addresses.  The authorization
      server MAY make these addresses available to end users for support
      requests for the client.
   tos_uri
      URL that points to a human-readable terms of service document for
      the client that describes a contractual relationship between the
      end-user and the client that the end-user accepts when authorizing
      the client.  The authorization server SHOULD display this URL to
      the end-user if it is provided.  The value of this field MUST



Richer, et al.          Expires February 6, 2015                [Page 8]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


      point to a valid web page.  The value of this field MAY be
      internationalized, as described in Section 2.2.
   policy_uri
      URL that points to a human-readable privacy policy document that
      describes how the deployment organization collects, uses, retains,
      and discloses personal data.  The authorization server SHOULD
      display this URL to the end-user if it is provided.  The value of
      this field MUST point to a valid web page.  The value of this
      field MAY be internationalized, as described in Section 2.2.
   jwks_uri
      URL referencing the client's JSON Web Key Set [JWK] document,
      which contains the client's public keys.  The value of this field
      MUST point to a valid JWK Set document.  These keys can be used by
      higher level protocols that use signing or encryption.  For
      instance, these keys might be used by some applications for
      validating signed requests made to the token endpoint when using
      JWTs for client authentication [OAuth.JWT].  Use of this parameter
      is preferred over the "jwks" parameter, as it allows for easier
      key rotation.  The "jwks_uri" and "jwks" parameters MUST NOT be
      used together.
   jwks
      Client's JSON Web Key Set [JWK] document value, which contains the
      client's public keys.  The value of this field MUST be a JSON
      object containing a valid JWK Set. These keys can be used by
      higher level protocols that use signing or encryption.  This
      parameter is intended to be used by clients that cannot use the
      "jwks_uri" parameter, such as native clients that cannot host
      public URLs.  The "jwks_uri" and "jwks" parameters MUST NOT be
      used together.
   software_id
      Identifier for the software that comprises a client.  Unlike
      "client_id", which is issued by the authorization server and may
      vary between instances, the "software_id" is asserted by the
      client software on behalf of the software developer and is
      intended to be shared among all instances of the client software.
      The identifier SHOULD NOT change when software version changes or
      when a new installation occurs.
   software_version
      Version identifier for the software that comprises a client.  The
      value of this field is a string that is intended to be compared
      using string equality matching.  The value of the
      "software_version" SHOULD change on any update to the client
      software.

   Extensions and profiles of this specification MAY expand this list.
   The authorization server MUST ignore any client metadata values sent
   by the client that it does not understand.




Richer, et al.          Expires February 6, 2015                [Page 9]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   Client metadata values can either be communicated directly in the
   body of a registration request, as described in Section 3.1, or
   included as claims in a software statement, as described in
   Section 2.3, or a mixture of both.  If the same client metadata name
   is present in both locations and the software statement is trusted by
   the authorization server, the value of a claim in the software
   statement MUST 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, for example by returning an
   "invalid_client_metadata" error response to an inconsistent
   registration request.

   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.

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



Richer, et al.          Expires February 6, 2015               [Page 10]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   "client_name", "tos_uri", "policy_uri", "logo_uri", and "client_uri"
   might have multiple locale-specific values in some client
   registrations to facilitate use in different locations.

   To specify the languages and scripts, BCP47 [RFC5646] language tags
   are added to client metadata member names, delimited by a #
   character.  Since JSON [RFC7159] 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
   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 =




Richer, et al.          Expires February 6, 2015               [Page 11]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   JSON.parse(json);", then the member "client_name#en-us" can be
   accessed using the JavaScript syntax "j["client_name#en-us"]".

2.3.  Software Statement

   A software statement is a JSON Web Token (JWT) [JWT] that asserts
   metadata values about the client software as a bundle.  A set of
   claims that can be used in a software statement are defined in
   Section 2.  When presented to the authorization server as part of a
   client registration request, the software statement MUST be digitally
   signed or MACed using JWS [JWS] and MUST contain an "iss" (issuer)
   claim denoting the party attesting to the claims in the software
   statement.  It is RECOMMENDED that software statements be digitally
   signed using the "RS256" signature algorithm, although particular
   applications MAY specify the use of different algorithms.

   The means by which a client or developer obtains a software statement
   are outside the scope of this specification.  Some common methods
   could include a client developer generating a client-specific JWT
   registering with a software API publisher to obtain a software
   statement for a class of clients.  The software statement is
   typically distributed with all instances of a client application.

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

   In some cases, authorization servers MAY choose to accept a software
   statement value directly as a client identifier 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.

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].




Richer, et al.          Expires February 6, 2015               [Page 12]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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 client or developer 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 registration requests
   with no authorization (which is to say, with no initial 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.

3.1.  Client Registration Request

   This operation registers a client with the authorization server.  The
   authorization server assigns this client a unique client identifier,
   optionally assigns a client secret, and associates the metadata
   provided 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.

   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 [RFC7159] document consisting of a JSON
   object and all requested client metadata values as top-level members
   of that JSON object.

   Client metadata values may also be provided in a software statement,
   as described in Section 2.3.  Software statements are included in the
   requesting JSON object using this member:

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

   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:







Richer, et al.          Expires February 6, 2015               [Page 13]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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"],
      "client_name":"My Example Client",
      "client_name#ja-Jpan-JP":
         "\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D",
      "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",
      "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.





















Richer, et al.          Expires February 6, 2015               [Page 14]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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"],
      "client_name":"My Example Client",
      "client_name#ja-Jpan-JP":
         "\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D",
      "token_endpoint_auth_method":"client_secret_basic",
      "policy_uri":"https://client.example.org/policy.html",
      "jwks":{"keys":[{...omitted for brevity...}]},
      "example_extension_parameter": "example_value"
     }

   In the following example, some registration parameters are conveyed
   as claims in a software statement, while some values specific to the
   client instance are conveyed as regular parameters (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...]",
       "scope":"read write",
       "example_extension_parameter":"example_value"
     }








Richer, et al.          Expires February 6, 2015               [Page 15]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


3.2.  Client Registration Response

   Upon successful registration, the authorization server returns a
   client identifier for the client.  The server responds with an HTTP
   201 Created code and a body of type "application/json" with content
   as described in Section 4.1.

   Upon an unsuccessful registration, the authorization server responds
   with an error, as described in Section 4.2.

4.  Responses

   The following responses are sent in response to registration
   requests.

4.1.  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.

   client_id
      REQUIRED.  OAuth 2.0 client identifier.  It SHOULD NOT be
      currently valid for any other registered client, though an
      authorization server MAY issue the same client identifier to
      multiple instances of a registered client, at its discretion.
   client_secret
      OPTIONAL.  OAuth 2.0 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.



Richer, et al.          Expires February 6, 2015               [Page 16]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   The response is an "application/json" document with all parameters as
   top-level members of a JSON object [RFC7159].

   If a software statement was used as part of the registration, its
   value MUST be returned in the response along with other metadata.
   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).

   Following is a non-normative example response:

     HTTP/1.1 201 Created
     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"],
      "client_name":"My Example Client",
      "client_name#ja-Jpan-JP":
         "\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D",
      "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",
      "example_extension_parameter": "example_value"
     }

4.2.  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 [RFC7159]
   describing the error in the response body.

   Two members are defined for inclusion in the JSON object:




Richer, et al.          Expires February 6, 2015               [Page 17]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   error
      REQUIRED.  Single ASCII error code string.
   error_description
      OPTIONAL.  Human-readable ASCII text description of the error used
      for debugging.

   Other members MAY also be included, and if not understood, MUST be
   ignored.

   This specification defines the following error codes:

   invalid_redirect_uri
      The value of one or more redirection 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.
   invalid_software_statement
      The software statement presented is invalid.
   unapproved_software_statement
      The software statement presented is not approved for use by this
      authorization server.

   Following is a non-normative example of an error response resulting
   from a redirection URI that has been blacklisted by the authorization
   server (with line wraps within values 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 redirection URI
        http://sketchy.example.com is not allowed by this server."
     }













Richer, et al.          Expires February 6, 2015               [Page 18]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   Following is a non-normative example of an error response resulting
   from an inconsistent combination of "response_types" and
   "grant_types" values (with line wraps within values for display
   purposes only):

     HTTP/1.1 400 Bad Request
     Content-Type: application/json
     Cache-Control: no-store
     Pragma: no-cache

     {
      "error": "invalid_client_metadata",
      "error_description": "The grant type 'authorization_code' must be
        registered along with the response type 'code' but found only
       'implicit' instead."
     }

5.  IANA Considerations

5.1.  OAuth Dynamic Registration Client Metadata Registry

   This specification establishes the OAuth Dynamic 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 Dynamic 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)
   and should direct all requests for registration to the review mailing
   list.





Richer, et al.          Expires February 6, 2015               [Page 19]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


5.1.1.  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 "IESG".  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.

5.1.2.  Initial Registry Contents

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

   o  Client Metadata Name: "redirect_uris"
   o  Client Metadata Description: Array of redirection 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 ]]

   o  Client Metadata Name: "response_types"
   o  Client Metadata Description: Array of the OAuth 2.0 response types
      that the client may use



Richer, et al.          Expires February 6, 2015               [Page 20]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   o  Change controller: IESG
   o  Specification document(s): [[ this document ]]

   o  Client Metadata Name: "client_name"
   o  Client Metadata Description: Human-readable name of the client to
      be presented to the user
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "client_uri"
   o  Client Metadata Description: URL of a Web page providing
      information about the client
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "logo_uri"
   o  Client Metadata Description: URL that references a logo for the
      client
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "scope"
   o  Client Metadata Description: Space separated list of scope values
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "contacts"
   o  Client Metadata Description: Array of strings representing ways to
      contact people responsible for this client, typically email
      addresses
   o  Change Controller: IESG
   o  Specification document(s): [[ this document ]]

   o  Client Metadata Name: "tos_uri"
   o  Client Metadata Description: URL that points to a human-readable
      Terms of Service document for the client
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "policy_uri"
   o  Client Metadata Description: URL that points to a human-readable
      Policy document for the client
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "jwks_uri"
   o  Client Metadata Description: URL referencing the client's JSON Web
      Key Set [JWK] document representing the client's public keys



Richer, et al.          Expires February 6, 2015               [Page 21]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "jwks"
   o  Client Metadata Description: Client's JSON Web Key Set [JWK]
      document representing the client's public keys
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "software_id"
   o  Client Metadata Description: Identifier for the software that
      comprises a client
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "software_version"
   o  Client Metadata Description: Version identifier for the software
      that comprises a client
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "client_id"
   o  Client Metadata Description: Client identifier
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "client_secret"
   o  Client Metadata Description: Client secret
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "client_id_issued_at"
   o  Client Metadata Description: Time at which the client identifier
      was issued
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

   o  Client Metadata Name: "client_secret_expires_at"
   o  Client Metadata Description: Time at which the client secret will
      expire
   o  Change Controller: IESG
   o  Specification Document(s): [[ this document ]]

5.2.  OAuth Token Endpoint Authentication Methods Registry

   This specification establishes the OAuth Token Endpoint
   Authentication Methods registry.




Richer, et al.          Expires February 6, 2015               [Page 22]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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.

5.2.1.  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 "IESG".  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.

5.2.2.  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



Richer, et al.          Expires February 6, 2015               [Page 23]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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 ]]

6.  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 MUST
   require clients to register their redirection URI values.  This can
   help mitigate attacks where rogue actors inject and impersonate a
   validly registered client and intercept its authorization code or
   tokens through an invalid redirection URI or open redirector.
   Additionally, in order to prevent hijacking of the return values of
   the redirection, registered redirection URI values MUST be one of:

   o  A remote web site protected by TLS (e.g.,
      https://client.example.com/oauth_redirect)
   o  A web site hosted on the local machine using an HTTP URI (e.g.,
      http://localhost:8080/oauth_redirect)
   o  A non-HTTP application-specific URL that is available only to the
      client application (e.g., exampleapp://oauth_redirect)

   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



Richer, et al.          Expires February 6, 2015               [Page 24]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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.

   Unless used as a claim in a software statement, the authorization
   server MUST treat all client metadata as self-asserted.  For
   instance, a rogue client might use the name and logo of a legitimate
   client that it is trying to impersonate.  Additionally, a rogue
   client might try to use the software identifier or software version
   of a legitimate client to attempt to associate itself on the
   authorization server with instances of the legitimate client.  To
   counteract this, an authorization server needs to take steps to
   mitigate this risk by looking at the entire registration request and
   client configuration.  For instance, an authorization server could
   issue a warning if the domain/site of the logo doesn't match the
   domain/site of redirection URIs.  An authorization server could also
   refuse registration requests from a known software identifier that is
   requesting different redirection URIs or a different client homepage
   URI.  An authorization server can also present warning messages to
   end users about dynamically registered clients in all cases,
   especially if such clients have been recently registered or have not
   been trusted by any users at the authorization server before.

   In a situation where the authorization server is supporting open
   client registration, it must be extremely careful with any URL
   provided by the client that will be displayed to the user (e.g.
   "logo_uri", "tos_uri", "client_uri", and "policy_uri").  For



Richer, et al.          Expires February 6, 2015               [Page 25]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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 URIs resolve to valid web pages.

   Clients MAY use both the direct JSON object and the JWT-encoded
   software statement to present client metadata to the authorization
   server as part of the registration request.  A software statement is
   cryptographically protected and represents claims made by the issuer
   of the statement, while the JSON object represents the self-asserted
   claims made by the client or developer directly.  If the software
   statement is valid and trusted, the values of client metadata within
   the software statement MUST take precedence over those metadata
   values presented in the plain JSON object, which could have been
   modified en route.

   The software statement is an item that is self-asserted by the
   client, even though its contents have been digitally signed or MACed
   by the issuer of the software statement.  As such, presentation of
   the software statement is not sufficient in most cases to fully
   identity a piece of client software.  An initial access token, in
   contrast, does not necessarily contain information about a particular
   piece of client software but instead represents authorization to use
   the registration endpoint.  An authorization server MUST consider the
   full registration request, including the software statement, initial
   access token, and JSON client metadata values, when deciding whether
   to honor a given registration request.

   If an authorization server receives a registration request for a
   client that uses the same "software_id" and "software_version" values
   as another client, the server should treat the new registration as
   being suspect.  It is possible that the new client is trying to
   impersonate the existing client.

   Since a client identifier is a public value that can be used to
   impersonate a client at the authorization endpoint, an authorization
   server that decides to issue the same client identifier to multiple
   instances of a registered client MUST be very particular about the
   circumstances under which this occurs.  For instance, the
   authorization server can limit a given client identifier to clients
   using the same redirect-based flow and the same redirection URIs.  An
   authorization server SHOULD NOT issue the same client secret to
   multiple instances of a registered client, even if they are issued
   the same client identifier, or else the client secret could be
   leaked, allowing malicious imposters to impersonate a confidential
   client.



Richer, et al.          Expires February 6, 2015               [Page 26]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


7.  References

7.1.  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), July 2014.

   [JWS]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", draft-ietf-jose-json-web-signature (work
              in progress), July 2014.

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

   [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.

   [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.





Richer, et al.          Expires February 6, 2015               [Page 27]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   [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.

   [RFC7159]  Bray, T., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, March 2014.

7.2.  Informative References

   [I-D.hardjono-oauth-umacore]
              Hardjono, T., "User-Managed Access (UMA) Profile of OAuth
              2.0", draft-hardjono-oauth-umacore-10 (work in progress),
              July 2014.

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

   [OpenID.Registration]
              Sakimura, N., Bradley, J., and M. Jones, "OpenID Connect
              Dynamic Client Registration 1.0", February 2014.

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.





Richer, et al.          Expires February 6, 2015               [Page 28]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


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 digitally signed or MACed (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 by an authority for a set of client metadata values.
   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.

A.3.  Registration by the Client or 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 identifier and other
   information needed to interact with the authorization server.  In
   this case, no client identifier 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 identifier value(s) for the authorization server(s)
   can be packaged with the client software.



Richer, et al.          Expires February 6, 2015               [Page 29]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


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 identifier
   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 Among All Instances of Client Software

   In some cases, each deployed instance of a piece of client software
   will share a common client identifier value.  For instance, this is
   often the case for in-browser clients using the 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 identifier values, and return the same
   client identifier 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

A.5.1.  Stateful Client Registration

   In some cases, authorization servers will maintain state about
   registered clients, typically indexing this state using the client
   identifier 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.  One possible set of
   operations upon stateful registrations is 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 identifier value, and possibly




Richer, et al.          Expires February 6, 2015               [Page 30]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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 ]]

   -19

   o  Added informative references to the OpenID Connect Dynamic Client
      Registration and UMA specifications in the introduction.
   o  Clarified the "jwks" and "jwks_uri" descriptions and included an
      example situation in which they might be used.
   o  Removed "application_type".
   o  Added redirection URI usage restrictions to the Security
      Considerations section, based on the client type.
   o  Expanded the "tos_uri" and "policy_uri" descriptions.

   -18

   o  Corrected an example HTTP response status code to be 201 Created.
   o  Said more about who issues and uses initial access tokens and
      software statements.
   o  Stated that the use of an initial access token is required when
      the authorization server limits the parties that can register a
      client.
   o  Stated that the implementation and use of all client metadata
      fields is OPTIONAL, other than "redirect_uris", which MUST be used
      for redirect-based flows and implemented to fulfill the
      requirement in Section 2 of OAuth 2.0.
   o  Added the "application_type" metadata value, which had somehow
      been omitted.
   o  Added missing default metadata values, which had somehow been
      omitted.
   o  Clarified that the "software_id" is ultimately asserted by the
      client developer.



Richer, et al.          Expires February 6, 2015               [Page 31]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   o  Clarified that the "error" member is required in error responses,
      "error_description" member is optional, and other members may be
      present.
   o  Added security consideration about registrations with duplicate
      "software_id" and "software_version" values.

   -17

   o  Merged draft-ietf-oauth-dyn-reg-metadata back into this document.
   o  Removed "Core" from the document title.
   o  Explicitly state that all metadata members are optional.
   o  Clarified language around software statements for use in
      registration context.
   o  Clarified that software statements need to be digitally signed or
      MACed.
   o  Added a "jwks" metadata parameter to parallel the "jwks_uri"
      parameter.
   o  Removed normative language from terminology.
   o  Expanded abstract and introduction.
   o  Addressed review comments from several working group members.

   -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

   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 identifier value under certain
      circumstances.
   o  Rewrote the introduction.
   o  Rewrote the Use Cases appendix.

   -14

   o  Added software_id and software_version metadata fields



Richer, et al.          Expires February 6, 2015               [Page 32]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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
   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



Richer, et al.          Expires February 6, 2015               [Page 33]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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.
   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.




Richer, et al.          Expires February 6, 2015               [Page 34]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   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

   -01

   o  Merged UMA and OpenID Connect registrations into a single document



Richer, et al.          Expires February 6, 2015               [Page 35]

Internet-Draft       OAuth 2.0 Dynamic Registration          August 2014


   o  Changed to form-parameter inputs to endpoint
   o  Removed pull-based registration

   -00

   o  Imported original UMA draft specification

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












Richer, et al.          Expires February 6, 2015               [Page 36]


Html markup produced by rfcmarkup 1.108, available from http://tools.ietf.org/tools/rfcmarkup/