draft-ietf-oauth-dyn-reg.xml

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<rfc category="std" docName="draft-ietf-oauth-dyn-reg-14" ipr="trust200902">
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  <front>
    <title abbrev="oauth-dyn-reg">OAuth 2.0 Dynamic Client Registration
    Protocol</title>

    <author fullname="Justin Richer" initials="J" role="editor"
            surname="Richer">
      <organization>The MITRE Corporation</organization>

      <address>
        <postal>
          <street/>

          <city/>

          <region/>

          <code/>

          <country/>
        </postal>

        <phone/>

        <facsimile/>

        <email>jricher@mitre.org</email>

        <uri/>
      </address>
    </author>

    <author fullname="John Bradley" initials="J." surname="Bradley">
      <organization abbrev="Ping Identity">Ping Identity</organization>

      <address>
        <email>ve7jtb@ve7jtb.com</email>
      </address>
    </author>

    <author fullname="Michael B. Jones" initials="M.B." surname="Jones">
      <organization abbrev="Microsoft">Microsoft</organization>

      <address>
        <email>mbj@microsoft.com</email>

        <uri>http://self-issued.info/</uri>
      </address>
    </author>

    <author fullname="Maciej Machulak" initials="M" surname="Machulak">
      <organization>Newcastle University</organization>

      <address>
        <email>m.p.machulak@ncl.ac.uk</email>

        <uri>http://ncl.ac.uk/</uri>
      </address>
    </author>

    <date day="29" month="July" year="2013"/>

    <area>Security</area>

    <workgroup>OAuth Working Group</workgroup>

    <abstract>
      <t>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.</t>
    </abstract>
  </front>

  <middle>
    <section anchor="Introduction" title="Introduction">
      <t>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 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.</t>

      <t>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.</t>

      <section anchor="Notation" title="Notational Conventions">
        <t>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 <xref
        target="RFC2119"/>.</t>

        <t>Unless otherwise noted, all the protocol parameter names and values
        are case sensitive.</t>
      </section>

      <section anchor="terminology" title="Terminology">
        <t>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 <xref target="RFC6749">OAuth
        2.0</xref>.</t>

        <t>This specification defines the following additional terms:</t>

        <t><list style="hanging">
            <t hangText="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.</t>

            <t hangText="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.</t>

            <t hangText="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.</t>

            <t hangText="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.</t>
          </list></t>
      </section>

      <section anchor="protocol-flow" title="Protocol Flow">
        <figure>
          <preamble>(preamble)</preamble>

          <artwork><![CDATA[
       +--------(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 -----------|               |
 +-----------+                                      +---------------+


]]></artwork>

          <postamble>Figure 1: Abstract Protocol Flow</postamble>
        </figure>

        <t>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:</t>

        <t><list style="hanging">
            <t hangText="(A)"><vspace blankLines="0"/>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.</t>

            <t hangText="(B)"><vspace blankLines="0"/>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.</t>

            <t hangText="(C)"><vspace blankLines="0"/>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.</t>

            <t hangText="(D)"><vspace blankLines="0"/>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.</t>

            <t hangText="(E)"><vspace blankLines="0"/>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.</t>

            <t hangText="(F)"><vspace blankLines="0"/>The client or developer
            optionally calls the client configuration endpoint with a delete
            request using the registration access token issued in (C).</t>

            <t hangText="(G)"><vspace blankLines="0"/>The authorization server
            deprovisions the client and responds with a confirmation that the
            deletion has taken place.</t>
          </list>Further discussion of possible example lifecycles are found
        in the Appendix to this specification, <xref
        target="client-lifecycle-examples">Client Lifecycle
        Examples</xref>.</t>
      </section>

      <section anchor="Credentials"
               title="Registration Tokens and Client Credentials">
        <t>Throughout the course of the dynamic registration protocol, there
        are three different classes of credentials in play, each with
        different properties and targets.</t>

        <t><list style="symbols">
            <t>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.</t>

            <t>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.</t>

            <t>The client credentials (such as <spanx style="verb">client_secret</spanx>)
            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.</t>
          </list></t>

        <section anchor="credential-rotation" title="Credential Rotation">
          <t>The Authorization Server MAY rotate the client's registration
          access token and/or client credentials (such as a <spanx
          style="verb">client_secret</spanx>) throughout the lifetime of the
          client. The client can discovery that these values have changed by
          reading the client information response returned from either a read
          or update request to the client configuration endpoint. The client's
          current registration access token and client credentials (if
          applicable) MUST be included in this response.</t>

          <t>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.</t>
        </section>
      </section>
    </section>

    <section anchor="client-metadata" title="Client Metadata">
      <t>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.</t>

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

      <t><list style="symbols">
          <t>the client requesting its desired values for each parameter to
          the authorization server in a <xref
          target="RegistrationRequest">register</xref> or <xref
          target="UpdateRequest">update</xref> request, and</t>

          <t>the authorization server informing the client of the current
          values of each parameter that the client has been registered to use
          through a <xref target="client-info-response">client information
          response</xref>.</t>
        </list></t>

      <t>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.</t>

      <t>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.</t>

      <t><list style="hanging">
          <t hangText="redirect_uris"><vspace blankLines="0"/>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.</t>

          <t hangText="client_name"><vspace blankLines="0"/>Human-readable
          name of the client to be presented to the user. If omitted, the
          authorization server MAY display the raw <spanx style="verb">client_id</spanx>
          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 <xref target="HumanReadableClientMetadata">Human
          Readable Client Metadata</xref>.</t>

          <t hangText="client_uri"><vspace/>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 <xref
          target="HumanReadableClientMetadata">Human Readable Client
          Metadata</xref>.</t>

          <t hangText="logo_uri"><vspace blankLines="0"/>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 <xref
          target="HumanReadableClientMetadata">Human Readable Client
          Metadata</xref>.</t>

          <t hangText="contacts"><vspace blankLines="0"/>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.</t>

          <t hangText="tos_uri"><vspace blankLines="0"/>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 <xref
          target="HumanReadableClientMetadata">Human Readable Client
          Metadata</xref>.</t>

          <t hangText="policy_uri"><vspace blankLines="0"/>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 <xref
          target="HumanReadableClientMetadata">Human Readable Client
          Metadata</xref>.</t>

          <t hangText="token_endpoint_auth_method"><vspace blankLines="0"/>The
          requested authentication method for the token endpoint. Values
          defined by this specification are: <list style="symbols">
              <t><spanx style="verb">none</spanx>: The client is a public
              client as defined in OAuth 2.0 and does not have a client
              secret.</t>

              <t><spanx style="verb">client_secret_post</spanx>: The client
              uses the HTTP POST parameters defined in OAuth 2.0 section
              2.3.1.</t>

              <t><spanx style="verb">client_secret_basic</spanx>: the client
              uses HTTP Basic defined in OAuth 2.0 section 2.3.1</t>
            </list> Additional values can be defined via the IANA OAuth Token
          Endpoint Authentication Methods Registry <xref
          target="team-registry"/>. Absolute URIs can also be used as values
          for this parameter without being registered. If unspecified or
          omitted, the default is <spanx style="verb">client_secret_basic</spanx>,
          denoting HTTP Basic Authentication Scheme as specified in Section
          2.3.1 of OAuth 2.0.</t>

          <t hangText="scope"><vspace blankLines="0"/>Space separated list of
          scope values (as described in <xref target="RFC6749">OAuth 2.0
          Section 3.3</xref>) 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.</t>

          <t hangText="grant_types"><vspace blankLines="0"/>Array of OAuth 2.0
          grant types that the Client may use. These grant types are defined
          as follows:<list style="symbols">
              <t><spanx style="verb">authorization_code</spanx>: The
              Authorization Code Grant described in OAuth 2.0 Section 4.1</t>

              <t><spanx style="verb">implicit</spanx>: The Implicit Grant
              described in OAuth 2.0 Section 4.2</t>

              <t><spanx style="verb">password</spanx>: The Resource Owner
              Password Credentials Grant described in OAuth 2.0 Section
              4.3</t>

              <t><spanx style="verb">client_credentials</spanx>: The Client
              Credentials Grant described in OAuth 2.0 Section 4.4</t>

              <t><spanx style="verb">refresh_token</spanx>: The Refresh Token
              Grant described in OAuth 2.0 Section 6.</t>

              <t><spanx style="verb">urn:ietf:params:oauth:grant-type:jwt-bearer</spanx>:
              The JWT Bearer Grant defined in <xref target="OAuth.JWT">OAuth
              JWT Bearer Token Profiles</xref>.</t>

              <t><spanx style="verb">urn:ietf:params:oauth:grant-type:saml2-bearer</spanx>:
              The SAML 2 Bearer Grant defined in <xref
              target="OAuth.SAML2">OAuth SAML 2 Bearer Token
              Profiles</xref>.</t>
            </list>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 <spanx style="verb">grant_type</spanx> parameter passed
          to the token endpoint defined in the extension.</t>

          <t hangText="response_types"><vspace blankLines="0"/>Array of the
          OAuth 2.0 response types that the Client may use. These response
          types are defined as follows:<list style="symbols">
              <t><spanx style="verb">code</spanx>: The Authorization Code
              response described in OAuth 2.0 Section 4.1.</t>

              <t><spanx style="verb">token</spanx>: The Implicit response
              described in OAuth 2.0 Section 4.2.</t>
            </list>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 <spanx style="verb">response_type</spanx>
          parameter passed to the authorization endpoint defined in the
          extension.</t>

          <t hangText="jwks_uri"><vspace blankLines="0"/>URL for the Client's
          <xref target="JWK">JSON Web Key Set</xref> 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.</t>

          <t hangText="software_id"><vspace blankLines="0"/>A identifier for
          the software that comprises a client. Unlike <spanx style="verb">client_id</spanx>,
          which is issued by the authorization server and generally varies
          between instances, the <spanx style="verb">software_id</spanx> is
          asserted by the client software and is intended to be shared between
          all copies of the client software. The value for this field MAY be a
          <xref target="RFC4122">UUID</xref>. The identifier SHOULD NOT change
          when software version changes or when a new installation instance is
          detected. Authorization servers MUST treat this field as
          self-asserted by the client and MUST NOT make any trusted decisions
          on the value of this field alone.</t>

          <t hangText="software_version"><vspace blankLines="0"/>A 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 <spanx style="verb">software_version</spanx>
          SHOULD change on any update to the client software. Authorization
          servers MUST treat this field as self-asserted by the client and
          MUST NOT make any trusted decisions on the value of this field
          alone.</t>
        </list></t>

      <section anchor="GrantTypesAndResponseTypes"
               title="Relationship Between Grant Types and Response Types">
        <t>The <spanx style="verb">grant_types</spanx> and <spanx
        style="verb">response_types</spanx> 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
        <spanx style="verb">grant_types</spanx> available to a client
        influence the <spanx style="verb">response_types</spanx> that the
        client is allowed to use, and vice versa. For instance, a <spanx
        style="verb">grant_types</spanx> value that includes <spanx
        style="verb">authorization_code</spanx> implies a <spanx style="verb">response_types</spanx>
        value that includes <spanx style="verb">code</spanx>, 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.</t>

        <t>The correlation between the two fields is listed in the table
        below.</t>

        <texttable>
          <ttcol>grant_types value includes:</ttcol>

          <ttcol>response_types value includes:</ttcol>

          <c>authorization_code</c>

          <c>code</c>

          <c>implicit</c>

          <c>token</c>

          <c>password</c>

          <c>(none)</c>

          <c>client_credentials</c>

          <c>(none)</c>

          <c>refresh_token</c>

          <c>(none)</c>

          <c>urn:ietf:params:oauth:grant-type:jwt-bearer</c>

          <c>(none)</c>

          <c>urn:ietf:params:oauth:grant-type:saml2-bearer</c>

          <c>(none)</c>
        </texttable>

        <t>Extensions and profiles of this document that introduce new values
        to either the <spanx style="verb">grant_types</spanx> or <spanx
        style="verb">response_types</spanx> parameter MUST document all
        correspondences between these two parameter types.</t>
      </section>

      <section anchor="HumanReadableClientMetadata"
               title="Human Readable Client Metadata">
        <t>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
        <spanx style="verb">client_name</spanx>, <spanx style="verb">tos_uri</spanx>,
        <spanx style="verb">policy_uri</spanx>, <spanx style="verb">logo_uri</spanx>,
        and <spanx style="verb">client_uri</spanx> might have multiple
        locale-specific values in some client registrations.</t>

        <t>To specify the languages and scripts, <xref
        target="RFC5646">BCP47</xref> 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 <xref target="IANA.Language">IANA Language
        Subtag Registry</xref>. 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 <spanx style="verb">fr</spanx>
        might be sufficient in many contexts, rather than <spanx style="verb">fr-CA</spanx>
        or <spanx style="verb">fr-FR</spanx>.</t>

        <t>For example, a client could represent its name in English as <spanx
        style="verb">"client_name#en": "My Client"</spanx> and its name in
        Japanese as <spanx style="verb">"client_name#ja-Jpan-JP": "\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D"</spanx>
        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.</t>

        <t>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.</t>

        <t>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 <spanx style="verb">#</spanx> 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, <spanx style="verb">var j = JSON.parse(json);</spanx>,
        then the member <spanx style="verb">client_name#en-us</spanx> can be
        accessed using the JavaScript syntax <spanx style="verb">j["client_name#en-us"]</spanx>.</t>
      </section>
    </section>

    <section anchor="RegistrationEndpoint"
             title="Client Registration Endpoint">
      <t>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 <spanx style="verb">application/json</spanx> format. The
      client registration endpoint MUST be protected by a transport-layer
      security mechanism, and the server MUST support TLS 1.2 <xref
      target="RFC5246">RFC 5246</xref> and/or TLS 1.0 <xref target="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 <xref target="RFC6125">RFC
      6125</xref>.</t>

      <t>The client registration endpoint MAY be an OAuth 2.0 protected
      resource and accept an initial access token in the form of an <xref
      target="RFC6749">OAuth 2.0 </xref> 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.</t>

      <t>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.</t>

      <t>To allow the registrant to manage the client's information, the
      client registration endpoint issues a request access token as an <xref
      target="RFC6750">OAuth 2.0 Bearer Token</xref> to securely authorize
      calls to the <xref target="AccessEndpoint">client configuration
      endpoint</xref>.</t>

      <t>The client registration endpoint MUST ignore all parameters it does
      not understand.</t>

      <section anchor="RegistrationRequest"
               title="Client Registration Request">
        <t>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 <xref
        target="client-metadata">Client Metadata</xref> 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.</t>

        <t>To register, the client or developer sends an HTTP POST to the
        client registration endpoint with a content type of <spanx
        style="verb">application/json</spanx>. The HTTP Entity Payload is a
        <xref target="RFC4627">JSON</xref> document consisting of a JSON
        object and all parameters as top-level members of that JSON
        object.</t>

        <t>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:</t>

        <figure>
          <preamble>Following is a non-normative example request (with line
          wraps for display purposes only):</preamble>

          <artwork><![CDATA[
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"
}
]]></artwork>
        </figure>

        <t/>

        <t>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 <xref target="RFC6750">OAuth 2.0 Bearer Token</xref>, but any OAuth
        2.0 token type could be used by an authorization server:</t>

        <figure>
          <preamble>Following is a non-normative example request (with line
          wraps for display purposes only):</preamble>

          <artwork><![CDATA[
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"
}
]]></artwork>
        </figure>

        <t/>
      </section>

      <section anchor="RegistrationResponse"
               title="Client Registration Response">
        <t>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
        <spanx style="verb">application/json</spanx> with content described in
        <xref target="client-info-response">Client Information
        Response</xref>.</t>

        <t>Upon an unsuccessful registration, the authorization server
        responds with an error as described in <xref
        target="client-registration-error">Client Registration
        Error</xref>.</t>
      </section>
    </section>

    <section anchor="AccessEndpoint" title="Client Configuration Endpoint">
      <t>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 <spanx style="verb">registration_client_uri</spanx>
      member of the <xref target="client-info-response">Client Information
      Response</xref>. The client MUST use its registration access token in
      all calls to this endpoint as an <xref target="RFC6750">OAuth 2.0 Bearer
      Token</xref>.</t>

      <t>Operations on this endpoint are switched through the use of different
      <xref target="RFC2616">HTTP methods</xref>. If an authorization server
      does not support a particular method on the client configuration
      endpoint, it MUST respond with the appropriate error code.</t>

      <section anchor="client-configuration-endpoint-uri"
               title="Forming the Client Configuration Endpoint URL">
        <t>The authorization server MUST provide the client with the fully
        qualified URL in the <spanx style="verb">registration_client_uri</spanx>
        element of the <xref target="client-info-response">Client Information
        Response</xref>. 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.</t>

        <t>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 <spanx style="verb">client_id</spanx> for this client, with the
        latter as either a path parameter or a query parameter. For example, a
        client with the client identifier <spanx style="verb">s6BhdRkqt3</spanx>
        could be given a client configuration endpoint URL of <spanx
        style="verb">https://server.example.com/register/s6BhdRkqt3</spanx>
        (path parameter) or of <spanx style="verb">https://server.example.com/register?client_id=s6BhdRkqt3</spanx>
        (query parameter). In both of these cases, the client simply uses the
        URL as given by the authorization server.</t>

        <t>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.</t>
      </section>

      <section anchor="ReadRequest" title="Client Read Request">
        <t>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.</t>

        <figure>
          <preamble>Following is a non-normative example request (with line
          wraps for display purposes only):</preamble>

          <artwork><![CDATA[GET /register/s6BhdRkqt3 HTTP/1.1
Accept: application/json
Host: server.example.com
Authorization: Bearer reg-23410913-abewfq.123483

]]></artwork>
        </figure>

        <t/>

        <t>Upon successful read of the information for a currently active
        client, the authorization server responds with an HTTP 200 OK with
        content type of <spanx style="verb">application/json</spanx> and a
        payload as described in <xref target="client-info-response">Client
        Information Response</xref>. Some values in the response, including
        the <spanx style="verb">client_secret</spanx> and <spanx style="verb">registration_access_token</spanx>,
        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 <spanx style="verb">client_id</spanx> MUST NOT change
        from the initial registration response.</t>

        <t>If the registration access token used to make this request is not
        valid, the server MUST respond with an error as described in <xref
        target="RFC6750">OAuth Bearer Token Usage</xref>.</t>

        <t>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.</t>

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

      <section anchor="UpdateRequest" title="Client Update Request">
        <t>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.</t>

        <t>The client sends an HTTP PUT to the client configuration endpoint
        with a content type of <spanx style="verb">application/json</spanx>.
        The HTTP entity payload is a <xref target="RFC4627">JSON</xref>
        document consisting of a JSON object and all parameters as top- level
        members of that JSON object.</t>

        <t>This request MUST include all fields described in <xref
        target="client-metadata">Client Metadata</xref> as returned to the
        client from a previous register, read, or update operation. The client
        MUST NOT include the <spanx style="verb">registration_access_token</spanx>,
        <spanx style="verb">registration_client_uri</spanx>, <spanx
        style="verb">client_secret_expires_at</spanx>, or <spanx style="verb">client_id_issued_at</spanx>
        fields described in <xref target="client-info-response">Client
        Information Response</xref>.</t>

        <t>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.</t>

        <t>The client MUST include its <spanx style="verb">client_id</spanx>
        field in the request, and it MUST be the same as its currently-issued
        client identifier. If the client includes the <spanx style="verb">client_secret</spanx>
        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.</t>

        <t>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.</t>

        <t>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:</t>

        <figure>
          <preamble>Following is a non-normative example request (with line
          wraps for display purposes only):</preamble>

          <artwork><![CDATA[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"
}
]]></artwork>
        </figure>

        <t/>

        <t>Upon successful update, the authorization server responds with an
        HTTP 200 OK Message with content type <spanx style="verb">application/json</spanx>
        and a payload as described in <xref
        target="client-info-response">Client Information Response</xref>. Some
        values in the response, including the <spanx style="verb">client_secret</spanx>
        and r<spanx style="verb">egistration_access_token</spanx>, 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 <spanx style="verb">client_id</spanx> MUST NOT change from the
        initial registration response.</t>

        <t>If the registration access token used to make this request is not
        valid, the server MUST respond with an error as described in <xref
        target="RFC6750">OAuth Bearer Token Usage</xref>.</t>

        <t>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.</t>

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

        <t>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 <xref
        target="client-registration-error">Client Registration Error
        Response</xref>.</t>
      </section>

      <section anchor="DeleteRequest" title="Client Delete Request">
        <t>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.</t>

        <figure>
          <preamble>Following is a non-normative example request (with line
          wraps for display purposes only):</preamble>

          <artwork><![CDATA[DELETE /register/s6BhdRkqt3 HTTP/1.1
Host: server.example.com
Authorization: Bearer reg-23410913-abewfq.123483

]]></artwork>
        </figure>

        <t/>

        <t>A successful delete action will invalidate the <spanx style="verb">client_id</spanx>,
        <spanx style="verb">client_secret</spanx>, and <spanx style="verb">registration_access_token</spanx>
        for this client, thereby preventing the <spanx style="verb">client_id</spanx>
        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.</t>

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

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

        <t>If the registration access token used to make this request is not
        valid, the server MUST respond with an error as described in <xref
        target="RFC6750">OAuth Bearer Token Usage</xref>.</t>

        <t>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.</t>

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

        <figure>
          <preamble>Following is a non-normative example response:</preamble>

          <artwork><![CDATA[HTTP/1.1 204 No Content
Cache-Control: no-store
Pragma: no-cache

]]></artwork>
        </figure>
      </section>
    </section>

    <section anchor="Responses" title="Responses">
      <t>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.</t>

      <section anchor="client-info-response"
               title="Client Information Response">
        <t>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 of 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.</t>

        <t><list style="hanging">
            <t hangText="client_id"><vspace/>REQUIRED. The unique client
            identifier, MUST NOT be currently valid for any other registered
            client.</t>

            <t hangText="client_secret"><vspace/>OPTIONAL. The client secret.
            If issued, this MUST be unique for each <spanx style="verb">client_id</spanx>.
            This value is used by confidential clients to authenticate to the
            token endpoint as described in <xref target="RFC6749">OAuth
            2.0</xref> Section 2.3.1.</t>

            <t hangText="client_id_issued_at"><vspace/>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.</t>

            <t hangText="client_secret_expires_at"><vspace/>REQUIRED if <spanx
            style="verb">client_secret</spanx> is issued. Time at which the
            <spanx style="verb">client_secret</spanx> 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.</t>

            <t hangText="registration_access_token"><vspace/>REQUIRED. Access
            token that is used at the client configuration endpoint to perform
            subsequent operations upon the client registration.</t>

            <t hangText="registration_client_uri"><vspace
            blankLines="0"/>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.</t>
          </list></t>

        <t>Additionally, the Authorization Server MUST return all registered
        <xref target="client-metadata">metadata</xref> 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.</t>

        <t>The response is an <spanx style="verb">application/json</spanx>
        document with all parameters as top-level members of a <xref
        target="RFC4627">JSON object</xref>.</t>

        <figure>
          <preamble>Following is a non-normative example response:</preamble>

          <artwork><![CDATA[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"
}]]></artwork>
        </figure>
      </section>

      <section anchor="client-registration-error"
               title="Client Registration Error Response">
        <t>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 <xref
        target="RFC6750">OAuth 2.0 Bearer Token Usage</xref>.</t>

        <t>When a registration error condition occurs, the authorization
        server returns an HTTP 400 status code (unless otherwise specified)
        with content type <spanx style="verb">application/json</spanx>
        consisting of a <xref target="RFC4627">JSON object</xref> describing
        the error in the response body.</t>

        <t>The JSON object contains two members:</t>

        <t><list style="hanging">
            <t hangText="error"><vspace/>The error code, a single ASCII
            string.</t>

            <t hangText="error_description"><vspace/>A human-readable text
            description of the error for debugging.</t>
          </list></t>

        <t>This specification defines the following error codes:</t>

        <t><list style="hanging">
            <t hangText="invalid_redirect_uri"><vspace/>The value of one or
            more <spanx style="verb">redirect_uris</spanx> is invalid.</t>

            <t hangText="invalid_client_metadata"><vspace/>The value of one of
            the <xref target="client-metadata">client metadata</xref> 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.</t>

            <t hangText="invalid_client_id"><vspace/> The value of <spanx
            style="verb">client_id</spanx> does not match the one assigned to
            this client.</t>
          </list></t>

        <figure>
          <preamble>Following is a non-normative example of an error response
          (with line wraps for display purposes only):</preamble>

          <artwork><![CDATA[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."
}]]></artwork>
        </figure>
      </section>
    </section>

    <section anchor="IANA" title="IANA Considerations">
      <section anchor="team-registry"
               title="OAuth Token Endpoint Authentication Methods Registry">
        <t>This specification establishes the OAuth Token Endpoint
        Authentication Methods registry.</t>

        <t>Additional values for use as <spanx style="verb">token_endpoint_auth_method</spanx>
        metadata values are registered with a Specification Required (<xref
        target="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.</t>

        <t>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").</t>

        <t>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.</t>

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

        <section anchor="team-template" title="Registration Template">
          <t><list style="hanging">
              <t
              hangText="Token Endpoint Authorization Method name:"><vspace/>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.</t>

              <t hangText="Change controller:"><vspace/>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.</t>

              <t hangText="Specification document(s):"><vspace/>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.</t>
            </list></t>
        </section>

        <section anchor="team-contents" title="Initial Registry Contents">
          <t>The OAuth Token Endpoint Authentication Methods registry's
          initial contents are:</t>

          <t><?rfc subcompact="yes"?> <list style="symbols">
              <t>Token Endpoint Authorization Method name: <spanx
              style="verb">none</spanx></t>

              <t>Change controller: IETF</t>

              <t>Specification document(s): [[ this document ]]</t>
            </list></t>

          <t><list style="symbols">
              <t>Token Endpoint Authorization Method name: <spanx
              style="verb">client_secret_post</spanx></t>

              <t>Change controller: IETF</t>

              <t>Specification document(s): [[ this document ]]</t>
            </list></t>

          <t><list style="symbols">
              <t>Token Endpoint Authorization Method name: <spanx
              style="verb">client_secret_basic</spanx></t>

              <t>Change controller: IETF</t>

              <t>Specification document(s): [[ this document ]]</t>
            </list></t>
        </section>

        <?rfc subcompact="no"?>
      </section>
    </section>

    <section anchor="Security" title="Security Considerations">
      <t>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 <xref
      target="RFC5246">RFC 5246</xref> and/or TLS 1.0 <xref target="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 <xref target="RFC6125">RFC
      6125</xref>.</t>

      <t>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.</t>

      <t>For clients that use redirect-based grant types such as <spanx
      style="verb">authorization_code</spanx> and <spanx style="verb">implicit</spanx>,
      authorization servers SHOULD require clients to register their <spanx
      style="verb">redirect_uris</spanx>. 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.</t>

      <t>The authorization server MUST treat all client metadata as
      self-asserted. For instance, a rogue client might use the name and logo
      for the legitimate client which 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 instances of the legitimate client. To
      counteract this, an authorization server needs to take steps to mitigate
      this phishing risk by looking at the entire registration request and
      client configuration. 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 could also refuse registration from a
      known software identifier that is requesting different redirect 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.</t>

      <t>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. <spanx
      style="verb">logo_uri</spanx>, <spanx style="verb">tos_uri</spanx>,
      <spanx style="verb">client_uri</spanx>, and <spanx style="verb">policy_uri</spanx>).
      For instance, a rogue client could specify a registration request with a
      reference to a drive-by download in the <spanx style="verb">policy_uri</spanx>.
      The authorization server SHOULD check to see if the <spanx style="verb">logo_uri</spanx>,
      <spanx style="verb">tos_uri</spanx>, <spanx style="verb">client_uri</spanx>,
      and <spanx style="verb">policy_uri</spanx> have the same host and scheme
      as the those defined in the array of <spanx style="verb">redirect_uris</spanx>
      and that all of these resolve to valid web pages.</t>

      <t>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 <xref target="RFC6750">OAuth 2.0 Bearer Token Usage</xref>.</t>

      <t>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).</t>

      <t>Public clients MAY register with an authorization server using this
      protocol, if the authorization server's policy allows them. Public
      clients use a <spanx style="verb">none</spanx> value for the <spanx
      style="verb">token_endpoint_auth_method</spanx> metadata field and are
      generally used with the <spanx style="verb">implicit</spanx> 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 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.</t>

      <t>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 <spanx style="verb">authorization_code</spanx> grant type make
      use of a client secret for the <spanx style="verb">token_endpoint_auth_method</spanx>,
      but any clients using the <spanx style="verb">implicit</spanx> 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
      <spanx style="verb">authorization_code</spanx> and <spanx style="verb">implicit</spanx>
      grant types simultaneously. Similarly, the <spanx style="verb">authorization_code</spanx>
      grant type is used to represent access on behalf of an end user, but the
      <spanx style="verb">client_credentials</spanx> 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
      <spanx style="verb">invalid_client_metadata</spanx> <xref
      target="client-registration-error">error response</xref>.</t>
    </section>
  </middle>

  <back>
    <references title="Normative References">
      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml' ?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.2246.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.2616.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.4122.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.4627.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.5226.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.5246.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.5646.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.6125.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.6749.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.6750.xml'?>

      <reference anchor="JWK">
        <front>
          <title>JSON Web Key (JWK)</title>

          <author fullname="Michael B. Jones" initials="M.B." surname="Jones">
            <organization>Microsoft</organization>

            <address>
              <email>mbj@microsoft.com</email>

              <uri>http://self-issued.info/</uri>
            </address>
          </author>

          <date day="8" month="May" year="2013"/>
        </front>

        <seriesInfo name="Internet-Draft" value="draft-ietf-jose-json-web-key"/>

        <format target="http://tools.ietf.org/html/draft-ietf-jose-json-web-key"
                type="HTML"/>
      </reference>

      <reference anchor="OAuth.JWT">
        <front>
          <title abbrev="OAuth JWT Bearer Token Profiles">JSON Web Token (JWT)
          Bearer Token Profiles for OAuth 2.0</title>

          <author fullname="Michael B. Jones" initials="M.B." surname="Jones">
            <!-- role="editor" -->

            <organization>Microsoft</organization>
          </author>

          <author fullname="Brian Campbell" initials="B." surname="Campbell">
            <organization abbrev="Ping Identity">Ping Identity
            Corp.</organization>
          </author>

          <author fullname="Chuck Mortimore" initials="C." surname="Mortimore">
            <organization>Salesforce</organization>
          </author>

          <date day="29" month="March" year="2013"/>
        </front>

        <seriesInfo name="Internet-Draft" value="draft-ietf-oauth-jwt-bearer"/>

        <format target="http://tools.ietf.org/html/draft-ietf-oauth-jwt-bearer"
                type="HTML"/>
      </reference>

      <reference anchor="OAuth.SAML2">
        <front>
          <title abbrev="OAuth JWT Bearer Token Profiles">SAML 2.0 Bearer
          Assertion Profiles for OAuth 2.0</title>

          <author fullname="Brian Campbell" initials="B." surname="Campbell">
            <organization abbrev="Ping Identity">Ping Identity
            Corp.</organization>
          </author>

          <author fullname="Chuck Mortimore" initials="C." surname="Mortimore">
            <organization>Salesforce</organization>
          </author>

          <author fullname="Michael B. Jones" initials="M.B." surname="Jones">
            <organization>Microsoft</organization>
          </author>

          <date day="29" month="March" year="2013"/>
        </front>

        <seriesInfo name="Internet-Draft"
                    value="draft-ietf-oauth-saml2-bearer"/>

        <format target="http://tools.ietf.org/html/draft-ietf-oauth-saml2-bearer"
                type="HTML"/>
      </reference>

      <reference anchor="IANA.Language">
        <front>
          <title>Language Subtag Registry</title>

          <author>
            <organization>Internet Assigned Numbers Authority
            (IANA)</organization>
          </author>

          <date year="2005"/>
        </front>

        <format target="http://www.iana.org/assignments/language-subtag-registry"
                type="TXT"/>
      </reference>
    </references>

    <section anchor="Acknowledgments" title="Acknowledgments">
      <t>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.</t>
    </section>

    <section anchor="client-lifecycle-examples"
             title="Client Lifecycle Examples">
      <t>In the <xref target="RFC6749">OAuth 2.0 specification</xref>, a
      client is identified by its own unique Client identifier (<spanx
      style="verb">client_id</spanx>) 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 client identifier is the
      expected trigger for a client registration operation.</t>

      <t>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:</t>

      <t><list style="symbols">
          <t>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.</t>

          <t>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.</t>
        </list></t>

      <t>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 <xref
      target="RegistrationRequest">registration request</xref> results in the
      issuance of a new client identifier.</t>

      <t>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.</t>

      <section anchor="OpenRegistration" title="Open Registration">
        <t>Open registration, with no authorization required on the client
        registration endpoint, works as follows:</t>

        <t><list style="letters">
            <t>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.</t>

            <t>The client sends an HTTP POST request to the client
            registration endpoint at the authorization server and includes its
            metadata.</t>

            <t>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.</t>

            <t>The client stores the returned response from the authorization
            server. At a minimum, it should remember the values of <spanx
            style="verb">client_id</spanx>, <spanx style="verb">client_secret</spanx>
            (if present), <spanx style="verb">registration_access_token</spanx>,
            and <spanx style="verb">registration_client_uri</spanx>.</t>

            <t>The client uses the its <spanx style="verb">client_id</spanx>
            and <spanx style="verb">client_secret</spanx> (if provided) to
            request OAuth 2.0 tokens using any valid OAuth 2.0 flow for which
            it is authorized.</t>

            <t>If the client's <spanx style="verb">client_secret</spanx>
            expires or otherwise stops working, the client sends an HTTP GET
            request to the <spanx style="verb">registration_client_uri</spanx>
            with the <spanx style="verb">registration_access_token</spanx> as
            its authorization. This response will contain the client's
            refreshed <spanx style="verb">client_secret</spanx> along with any
            changed metadata values. Its <spanx style="verb">client_id</spanx>
            will remain the same.</t>

            <t>If the client needs to update its configuration on the
            authorization server, it sends an HTTP PUT request to the <spanx
            style="verb">registration_client_uri</spanx> with the <spanx
            style="verb">registration_access_token</spanx> as its
            authorization. This response will contain the client's changed
            metadata values. Its <spanx style="verb">client_id</spanx> will
            remain the same.</t>

            <t>If the client is uninstalled or otherwise deprovisioned, it can
            send an HTTP DELETE request to the <spanx style="verb">registration_client_uri</spanx>
            with the <spanx style="verb">registration_access_token</spanx> as
            its authorization. This will effectively deprovision the client
            from the authorization server.</t>
          </list></t>
      </section>

      <section anchor="ProtectedRegistration" title="Protected Registration">
        <t>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.</t>

        <t><list style="letters">
            <t>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.</t>

            <t>The developer visits a manual pre-registration page at the
            authorization server and is issued an initial access token in the
            form of an <xref target="RFC6750">OAuth 2.0 Bearer
            Token</xref>.</t>

            <t>The developer packages that token with all instances of the
            client application.</t>

            <t>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.</t>

            <t>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.</t>

            <t>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.</t>

            <t>The client stores the returned response from the authorization
            server. At a minimum, it should know the values of <spanx
            style="verb">client_id</spanx>, <spanx style="verb">client_secret</spanx>
            (if present), <spanx style="verb">registration_access_token</spanx>,
            and <spanx style="verb">registration_client_uri</spanx>.</t>

            <t>The client uses the its <spanx style="verb">client_id</spanx>
            and <spanx style="verb">client_secret</spanx> (if provided) to
            request OAuth 2.0 tokens using any supported OAuth 2.0 flow for
            which this client is authorized.</t>

            <t>If the client's <spanx style="verb">client_secret</spanx>
            expires or otherwise stops working, the client sends an HTTP GET
            request to the <spanx style="verb">registration_client_uri</spanx>
            with the <spanx style="verb">registration_access_token</spanx> as
            its authorization. This response will contain the client's
            refreshed <spanx style="verb">client_secret</spanx> along with any
            metadata values registered to that client, some of which may have
            changed. Its <spanx style="verb">client_id</spanx> will remain the
            same.</t>

            <t>If the client needs to update its configuration on the
            authorization server, it sends an HTTP PUT request to the <spanx
            style="verb">registration_client_uri</spanx> with the <spanx
            style="verb">registration_access_token</spanx> as its
            authorization. The response will contain the client's changed
            metadata values. Its <spanx style="verb">client_id</spanx> will
            remain the same.</t>

            <t>If the client is uninstalled or otherwise deprovisioned, it can
            send an HTTP DELETE request to the <spanx style="verb">registration_client_uri</spanx>
            with the <spanx style="verb">registration_access_token</spanx> as
            its authorization. This will effectively deprovision the client
            from the Authorization Server.</t>
          </list></t>
      </section>

      <section anchor="DeveloperAutomation" title="Developer Automation">
        <t>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 registration
        endpoint, as described in <xref
        target="ProtectedRegistration">Protected Registration </xref>.
        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. <list style="letters">
            <t>A developer is creating a client to use an authorization server
            and knows that instances of the client will not dynamically
            register at runtime.</t>

            <t>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 <xref
            target="RFC6750">OAuth 2.0 Bearer Token</xref>.</t>

            <t>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 <xref
            target="RFC6750">OAuth 2.0 Bearer Token</xref>.</t>

            <t>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.</t>

            <t>The developer packages the client identifier with the client
            and stores the <spanx style="verb">registration_access_token</spanx>,
            and <spanx style="verb">registration_client_uri</spanx> in the
            deployment system.</t>

            <t>The client uses the its <spanx style="verb">client_id</spanx>
            and <spanx style="verb">client_secret</spanx> (if provided) to
            request OAuth 2.0 tokens using any supported OAuth 2.0 flow.</t>

            <t>If the client's <spanx style="verb">client_secret</spanx>
            expires or otherwise stops working, the developer's deployment
            system sends an HTTP GET request to the <spanx style="verb">registration_client_uri</spanx>
            with the <spanx style="verb">registration_access_token</spanx> as
            its authorization. This response will contain the client's
            refreshed <spanx style="verb">client_secret</spanx> along with any
            changed metadata values. Its <spanx style="verb">client_id</spanx>
            will remain the same. These new values will then be packaged and
            shipped to or retrieved by instances of the client, if
            necessary.</t>

            <t>If the developer needs to update its configuration on the
            authorization server, the deployment system sends an HTTP PUT
            request to the <spanx style="verb">registration_client_uri</spanx>
            with the <spanx style="verb">registration_access_token</spanx> as
            its authorization. This response will contain the client's changed
            metadata values. Its <spanx style="verb">client_id</spanx> will
            remain the same. These new values will then be packaged and
            shipped to or retrieved by instances of the client, if
            necessary.</t>

            <t>If the client is deprovisioned, the developer's deployment
            system can send an HTTP DELETE request to the <spanx style="verb">registration_client_uri</spanx>
            with the <spanx style="verb">registration_access_token</spanx> as
            its authorization. This will effectively deprovision the client
            from the authorization server and prevent any instances of the
            client from functioning.</t>
          </list></t>
      </section>
    </section>

    <section anchor="History" title="Document History">
      <t>[[ to be removed by the RFC editor before publication as an RFC
      ]]</t>

      <t>-14</t>

      <t><list style="symbols">
          <t>Added software_id and software_version metadata fields</t>

          <t>Added direct references to RFC6750 errors in read/update/delete
          methods</t>
        </list></t>

      <t>-13</t>

      <t><list style="symbols">
          <t>Fixed broken example text in registration request and in delete
          request</t>

          <t>Added security discussion of separating clients of different
          grant types</t>

          <t>Fixed error reference to point to RFC6750 instead of RFC6749</t>

          <t>Clarified that servers must respond to all requests to
          configuration endpoint, even if it's just an error code</t>

          <t>Lowercased all Terms to conform to style used in RFC6750</t>
        </list></t>

      <t>-12</t>

      <t><list style="symbols">
          <t>Improved definition of Initial Access Token</t>

          <t>Changed developer registration scenario to have the Initial
          Access Token gotten through a normal OAuth 2.0 flow</t>

          <t>Moved non-normative client lifecycle examples to appendix</t>

          <t>Marked differentiating between auth servers as out of scope</t>

          <t>Added protocol flow diagram</t>

          <t>Added credential rotation discussion</t>

          <t>Called out Client Registration Endpoint as an OAuth 2.0 Protected
          Resource</t>

          <t>Cleaned up several pieces of text</t>
        </list></t>

      <t>-11</t>

      <t><list style="symbols">
          <t>Added localized text to registration request and response
          examples.</t>

          <t>Removed <spanx style="verb">client_secret_jwt</spanx> and <spanx
          style="verb">private_key_jwt</spanx>.</t>

          <t>Clarified <spanx style="verb">tos_uri</spanx> and <spanx
          style="verb">policy_uri</spanx> definitions.</t>

          <t>Added the OAuth Token Endpoint Authentication Methods registry
          for registering <spanx style="verb">token_endpoint_auth_method</spanx>
          metadata values.</t>

          <t>Removed uses of non-ASCII characters, per RFC formatting
          rules.</t>

          <t>Changed <spanx style="verb">expires_at</spanx> to <spanx
          style="verb">client_secret_expires_at</spanx> and <spanx
          style="verb">issued_at</spanx> to <spanx style="verb">client_id_issued_at</spanx>
          for greater clarity.</t>

          <t>Added explanatory text for different credentials (Initial Access
          Token, Registration Access Token, Client Credentials) and what
          they're used for.</t>

          <t>Added Client Lifecycle discussion and examples.</t>

          <t>Defined Initial Access Token in Terminology section.</t>
        </list></t>

      <t>-10</t>

      <t><list style="symbols">
          <t>Added language to point out that scope values are
          service-specific</t>

          <t>Clarified normative language around client metadata</t>

          <t>Added extensibility to token_endpoint_auth_method using absolute
          URIs</t>

          <t>Added security consideration about registering redirect URIs</t>

          <t>Changed erroneous 403 responses to 401's with notes about token
          handling</t>

          <t>Added example for initial registration credential</t>
        </list></t>

      <t>-09</t>

      <t><list style="symbols">
          <t>Added method of internationalization for Client Metadata
          values</t>

          <t>Fixed SAML reference</t>
        </list></t>

      <t>-08</t>

      <t><list style="symbols">
          <t>Collapsed jwk_uri, jwk_encryption_uri, x509_uri, and
          x509_encryption_uri into a single jwks_uri parameter</t>

          <t>Renamed grant_type to grant_types since it's a plural value</t>

          <t>Formalized name of "OAuth 2.0" throughout document</t>

          <t>Added JWT Bearer Assertion and SAML 2 Bearer Assertion to example
          grant types</t>

          <t>Added response_types parameter and explanatory text on its use
          with and relationship to grant_types</t>
        </list></t>

      <t>-07</t>

      <t><list style="symbols">
          <t>Changed registration_access_url to registration_client_uri</t>

          <t>Fixed missing text in 5.1</t>

          <t>Added Pragma: no-cache to examples</t>

          <t>Changed "no such client" error to 403</t>

          <t>Renamed Client Registration Access Endpoint to Client
          Configuration Endpoint</t>

          <t>Changed all the parameter names containing "_url" to instead use
          "_uri"</t>

          <t>Updated example text for forming Client Configuration Endpoint
          URL</t>
        </list></t>

      <t>-06</t>

      <t><list style="symbols">
          <t>Removed secret_rotation as a client-initiated action, including
          removing client secret rotation endpoint and parameters.</t>

          <t>Changed _links structure to single value
          registration_access_url.</t>

          <t>Collapsed create/update/read responses into client info
          response.</t>

          <t>Changed return code of create action to 201.</t>

          <t>Added section to describe suggested generation and composition of
          Client Registration Access URL.</t>

          <t>Added clarifying text to PUT and POST requests to specify JSON in
          the body.</t>

          <t>Added Editor's Note to DELETE operation about its inclusion.</t>

          <t>Added Editor's Note to registration_access_url about alternate
          syntax proposals.</t>
        </list></t>

      <t>-05</t>

      <t><list style="symbols">
          <t>changed redirect_uri and contact to lists instead of space
          delimited strings</t>

          <t>removed operation parameter</t>

          <t>added _links structure</t>

          <t>made client update management more RESTful</t>

          <t>split endpoint into three parts</t>

          <t>changed input to JSON from form-encoded</t>

          <t>added READ and DELETE operations</t>

          <t>removed Requirements section</t>

          <t>changed token_endpoint_auth_type back to
          token_endpoint_auth_method to match OIDC who changed to match us</t>
        </list></t>

      <t>-04</t>

      <t><list style="symbols">
          <t>removed default_acr, too undefined in the general OAuth2 case</t>

          <t>removed default_max_auth_age, since there's no mechanism for
          supplying a non-default max_auth_age in OAuth2</t>

          <t>clarified signing and encryption URLs</t>

          <t>changed token_endpoint_auth_method to token_endpoint_auth_type to
          match OIDC</t>
        </list></t>

      <t>-03</t>

      <t><list style="symbols">
          <t>added scope and grant_type claims</t>

          <t>fixed various typos and changed wording for better clarity</t>

          <t>endpoint now returns the full set of client information</t>

          <t>operations on client_update allow for three actions on metadata:
          leave existing value, clear existing value, replace existing value
          with new value</t>
        </list></t>

      <t>-02</t>

      <t><list style="symbols">
          <t>Reorganized contributors and references</t>

          <t>Moved OAuth references to RFC</t>

          <t>Reorganized model/protocol sections for clarity</t>

          <t>Changed terminology to "client register" instead of "client
          associate"</t>

          <t>Specified that client_id must match across all subsequent
          requests</t>

          <t>Fixed RFC2XML formatting, especially on lists</t>
        </list></t>

      <t>-01</t>

      <t><list style="symbols">
          <t>Merged UMA and OpenID Connect registrations into a single
          document</t>

          <t>Changed to form-paramter inputs to endpoint</t>

          <t>Removed pull-based registration</t>
        </list></t>

      <t>-00</t>

      <t><list style="symbols">
          <t>Imported original UMA draft specification</t>
        </list></t>
    </section>
  </back>
</rfc>