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

Versions: (draft-jones-oauth-discovery) 00 01 02 03 04 05 06 07

OAuth Working Group                                             M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                             N. Sakimura
Expires: March 11, 2018                                              NRI
                                                              J. Bradley
                                                           Ping Identity
                                                       September 7, 2017


                OAuth 2.0 Authorization Server Metadata
                     draft-ietf-oauth-discovery-07

Abstract

   This specification defines a metadata format that an OAuth 2.0 client
   can use to obtain the information needed to interact with an OAuth
   2.0 authorization server, including its endpoint locations and
   authorization server capabilities.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 11, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of



Jones, et al.            Expires March 11, 2018                 [Page 1]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Notation and Conventions . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Authorization Server Metadata . . . . . . . . . . . . . . . .   3
     2.1.  Signed Authorization Server Metadata  . . . . . . . . . .   7
   3.  Obtaining Authorization Server Metadata . . . . . . . . . . .   8
     3.1.  Authorization Server Metadata Request . . . . . . . . . .   9
     3.2.  Authorization Server Metadata Response  . . . . . . . . .   9
     3.3.  Authorization Server Metadata Validation  . . . . . . . .  10
   4.  String Operations . . . . . . . . . . . . . . . . . . . . . .  10
   5.  Compatibility Notes . . . . . . . . . . . . . . . . . . . . .  11
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
     6.1.  TLS Requirements  . . . . . . . . . . . . . . . . . . . .  11
     6.2.  Impersonation Attacks . . . . . . . . . . . . . . . . . .  11
     6.3.  Publishing Metadata in a Standard Format  . . . . . . . .  12
     6.4.  Protected Resources . . . . . . . . . . . . . . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
     7.1.  OAuth Authorization Server Metadata Registry  . . . . . .  13
       7.1.1.  Registration Template . . . . . . . . . . . . . . . .  14
       7.1.2.  Initial Registry Contents . . . . . . . . . . . . . .  14
     7.2.  Updated Registration Instructions . . . . . . . . . . . .  17
     7.3.  Well-Known URI Registry . . . . . . . . . . . . . . . . .  18
       7.3.1.  Registry Contents . . . . . . . . . . . . . . . . . .  18
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  18
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  20
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  21
   Appendix B.  Document History . . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction

   This specification generalizes the metadata format defined by "OpenID
   Connect Discovery 1.0" [OpenID.Discovery] in a way that is compatible
   with OpenID Connect Discovery, while being applicable to a wider set
   of OAuth 2.0 use cases.  This is intentionally parallel to the way
   that the "OAuth 2.0 Dynamic Client Registration Protocol" [RFC7591]
   specification generalized the dynamic client registration mechanisms
   defined by "OpenID Connect Dynamic Client Registration 1.0"
   [OpenID.Registration] in a way that was compatible with it.

   The metadata for an authorization server is retrieved from a well-
   known location as a JSON [RFC7159] document, which declares its



Jones, et al.            Expires March 11, 2018                 [Page 2]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   endpoint locations and authorization server capabilities.  This
   process is described in Section 3.

   This metadata can either be communicated in a self-asserted fashion
   by the server origin via HTTPS or as a set of signed metadata values
   represented as claims in a JSON Web Token (JWT) [JWT].  In the JWT
   case, the issuer is vouching for the validity of the data about the
   authorization server.  This is analogous to the role that the
   Software Statement plays in OAuth Dynamic Client Registration
   [RFC7591].

   The means by which the client obtains the location of the
   authorization server metadata document is out of scope.  In some
   cases, the location may be manually configured into the client.  In
   other cases, it may be dynamically discovered, for instance, through
   the use of WebFinger [RFC7033], as described in Section 2 of "OpenID
   Connect Discovery 1.0" [OpenID.Discovery].

1.1.  Requirements Notation and Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in RFC
   2119 [RFC2119].

   All uses of JSON Web Signature (JWS) [JWS] and JSON Web Encryption
   (JWE) [JWE] data structures in this specification utilize the JWS
   Compact Serialization or the JWE Compact Serialization; the JWS JSON
   Serialization and the JWE JSON Serialization are not used.

1.2.  Terminology

   This specification uses the terms "Access Token", "Authorization
   Code", "Authorization Endpoint", "Authorization Grant",
   "Authorization Server", "Client", "Client Authentication", "Client
   Identifier", "Client Secret", "Grant Type", "Protected Resource",
   "Redirection URI", "Refresh Token", "Resource Owner", "Resource
   Server", "Response Type", and "Token Endpoint" defined by OAuth 2.0
   [RFC6749], the terms "Claim Name", "Claim Value", and "JSON Web Token
   (JWT)" defined by JSON Web Token (JWT) [JWT], and the term "Response
   Mode" defined by OAuth 2.0 Multiple Response Type Encoding Practices
   [OAuth.Responses].

2.  Authorization Server Metadata

   Authorization servers can have metadata describing their
   configuration.  The following authorization server metadata values




Jones, et al.            Expires March 11, 2018                 [Page 3]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   are used by this specification and are registered in the IANA "OAuth
   Authorization Server Metadata" registry established in Section 7.1:

   issuer
      REQUIRED.  The authorization server's issuer identifier, which is
      a URL that uses the "https" scheme and has no query or fragment
      components.  This is the location where ".well-known" RFC 5785
      [RFC5785] resources containing information about the authorization
      server are published.  Using these well-known resources is
      described in Section 3.  The issuer identifier is used to prevent
      authorization server mix-up attacks, as described in "OAuth 2.0
      Mix-Up Mitigation" [I-D.ietf-oauth-mix-up-mitigation].

   authorization_endpoint
      REQUIRED.  URL of the authorization server's authorization
      endpoint [RFC6749].

   token_endpoint
      URL of the authorization server's token endpoint [RFC6749].  This
      is REQUIRED unless only the implicit grant type is used.

   jwks_uri
      OPTIONAL.  URL of the authorization server's JWK Set [JWK]
      document.  The referenced document contains the signing key(s) the
      client uses to validate signatures from the authorization server.
      This URL MUST use the "https" scheme.  The JWK Set MAY also
      contain the server's encryption key(s), which are used by clients
      to encrypt requests to the server.  When both signing and
      encryption keys are made available, a "use" (public key use)
      parameter value is REQUIRED for all keys in the referenced JWK Set
      to indicate each key's intended usage.

   registration_endpoint
      OPTIONAL.  URL of the authorization server's OAuth 2.0 Dynamic
      Client Registration endpoint [RFC7591].

   scopes_supported
      RECOMMENDED.  JSON array containing a list of the OAuth 2.0
      [RFC6749] "scope" values that this authorization server supports.
      Servers MAY choose not to advertise some supported scope values
      even when this parameter is used.

   response_types_supported
      REQUIRED.  JSON array containing a list of the OAuth 2.0
      "response_type" values that this authorization server supports.
      The array values used are the same as those used with the
      "response_types" parameter defined by "OAuth 2.0 Dynamic Client
      Registration Protocol" [RFC7591].



Jones, et al.            Expires March 11, 2018                 [Page 4]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   response_modes_supported
      OPTIONAL.  JSON array containing a list of the OAuth 2.0
      "response_mode" values that this authorization server supports, as
      specified in OAuth 2.0 Multiple Response Type Encoding Practices
      [OAuth.Responses].  If omitted, the default is "["query",
      "fragment"]".  The response mode value "form_post" is also defined
      in OAuth 2.0 Form Post Response Mode [OAuth.Post].

   grant_types_supported
      OPTIONAL.  JSON array containing a list of the OAuth 2.0 grant
      type values that this authorization server supports.  The array
      values used are the same as those used with the "grant_types"
      parameter defined by "OAuth 2.0 Dynamic Client Registration
      Protocol" [RFC7591].  If omitted, the default value is
      "["authorization_code", "implicit"]".

   token_endpoint_auth_methods_supported
      OPTIONAL.  JSON array containing a list of client authentication
      methods supported by this token endpoint.  Client authentication
      method values are used in the "token_endpoint_auth_method"
      parameter defined in Section 2 of [RFC7591].  If omitted, the
      default is "client_secret_basic" -- the HTTP Basic Authentication
      Scheme specified in Section 2.3.1 of OAuth 2.0 [RFC6749].

   token_endpoint_auth_signing_alg_values_supported
      OPTIONAL.  JSON array containing a list of the JWS signing
      algorithms ("alg" values) supported by the token endpoint for the
      signature on the JWT [JWT] used to authenticate the client at the
      token endpoint for the "private_key_jwt" and "client_secret_jwt"
      authentication methods.  This metadata entry MUST be present if
      either of these authentication methods are specified in the
      "token_endpoint_auth_methods_supported" entry.  No default
      algorithms are implied if this entry is omitted.  Servers SHOULD
      support "RS256".  The value "none" MUST NOT be used.

   service_documentation
      OPTIONAL.  URL of a page containing human-readable information
      that developers might want or need to know when using the
      authorization server.  In particular, if the authorization server
      does not support Dynamic Client Registration, then information on
      how to register clients needs to be provided in this
      documentation.

   ui_locales_supported
      OPTIONAL.  Languages and scripts supported for the user interface,
      represented as a JSON array of BCP47 [RFC5646] language tag
      values.  If omitted, the set of supported languages and scripts is
      unspecified.



Jones, et al.            Expires March 11, 2018                 [Page 5]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   op_policy_uri
      OPTIONAL.  URL that the authorization server provides to the
      person registering the client to read about the authorization
      server's requirements on how the client can use the data provided
      by the authorization server.  The registration process SHOULD
      display this URL to the person registering the client if it is
      given.  As described in Section 5, despite the identifier
      "op_policy_uri", appearing to be OpenID-specific, its usage in
      this specification is actually referring to a general OAuth 2.0
      feature that is not specific to OpenID Connect.

   op_tos_uri
      OPTIONAL.  URL that the authorization server provides to the
      person registering the client to read about the authorization
      server's terms of service.  The registration process SHOULD
      display this URL to the person registering the client if it is
      given.  As described in Section 5, despite the identifier
      "op_tos_uri", appearing to be OpenID-specific, its usage in this
      specification is actually referring to a general OAuth 2.0 feature
      that is not specific to OpenID Connect.

   revocation_endpoint
      OPTIONAL.  URL of the authorization server's OAuth 2.0 revocation
      endpoint [RFC7009].

   revocation_endpoint_auth_methods_supported
      OPTIONAL.  JSON array containing a list of client authentication
      methods supported by this revocation endpoint.  The valid client
      authentication method values are those registered in the IANA
      "OAuth Token Endpoint Authentication Methods" registry
      [IANA.OAuth.Parameters].  If omitted, the default is
      "client_secret_basic" -- the HTTP Basic Authentication Scheme
      specified in Section 2.3.1 of OAuth 2.0 [RFC6749].

   revocation_endpoint_auth_signing_alg_values_supported
      OPTIONAL.  JSON array containing a list of the JWS signing
      algorithms ("alg" values) supported by the revocation endpoint for
      the signature on the JWT [JWT] used to authenticate the client at
      the revocation endpoint for the "private_key_jwt" and
      "client_secret_jwt" authentication methods.  This metadata entry
      MUST be present if either of these authentication methods are
      specified in the "revocation_endpoint_auth_methods_supported"
      entry.  No default algorithms are implied if this entry is
      omitted.  The value "none" MUST NOT be used.

   introspection_endpoint
      OPTIONAL.  URL of the authorization server's OAuth 2.0
      introspection endpoint [RFC7662].



Jones, et al.            Expires March 11, 2018                 [Page 6]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   introspection_endpoint_auth_methods_supported
      OPTIONAL.  JSON array containing a list of client authentication
      methods supported by this introspection endpoint.  The valid
      client authentication method values are those registered in the
      IANA "OAuth Token Endpoint Authentication Methods" registry
      [IANA.OAuth.Parameters] or those registered in the IANA "OAuth
      Access Token Types" registry [IANA.OAuth.Parameters].  (These
      values are and will remain distinct, due to Section 7.2.)  If
      omitted, the set of supported authentication methods MUST be
      determined by other means.

   introspection_endpoint_auth_signing_alg_values_supported
      OPTIONAL.  JSON array containing a list of the JWS signing
      algorithms ("alg" values) supported by the introspection endpoint
      for the signature on the JWT [JWT] used to authenticate the client
      at the introspection endpoint for the "private_key_jwt" and
      "client_secret_jwt" authentication methods.  This metadata entry
      MUST be present if either of these authentication methods are
      specified in the "introspection_endpoint_auth_methods_supported"
      entry.  No default algorithms are implied if this entry is
      omitted.  The value "none" MUST NOT be used.

   code_challenge_methods_supported
      OPTIONAL.  JSON array containing a list of PKCE [RFC7636] code
      challenge methods supported by this authorization server.  Code
      challenge method values are used in the "code_challenge_method"
      parameter defined in Section 4.3 of [RFC7636].  The valid code
      challenge method values are those registered in the IANA "PKCE
      Code Challenge Methods" registry [IANA.OAuth.Parameters].  If
      omitted, the authorization server does not support PKCE.

   Additional authorization server metadata parameters MAY also be used.
   Some are defined by other specifications, such as OpenID Connect
   Discovery 1.0 [OpenID.Discovery].

2.1.  Signed Authorization Server Metadata

   In addition to JSON elements, metadata values MAY also be provided as
   a "signed_metadata" value, which is a JSON Web Token (JWT) [JWT] that
   asserts metadata values about the authorization server as a bundle.
   A set of claims that can be used in signed metadata are defined in
   Section 2.  The signed metadata MUST be digitally signed or MACed
   using JSON Web Signature (JWS) [JWS] and MUST contain an "iss"
   (issuer) claim denoting the party attesting to the claims in the
   signed metadata.  Consumers of the metadata MAY ignore the signed
   metadata if they do not support this feature.  If the consumer of the
   metadata supports signed metadata, metadata values conveyed in the




Jones, et al.            Expires March 11, 2018                 [Page 7]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   signed metadata MUST take precedence over the corresponding values
   conveyed using plain JSON elements.

   Signed metadata is included in the authorization server metadata JSON
   object using this OPTIONAL member:

   signed_metadata
      A JWT containing metadata values about the authorization server as
      claims.  This is a string value consisting of the entire signed
      JWT.  A "signed_metadata" metadata value SHOULD NOT appear as a
      claim in the JWT.

3.  Obtaining Authorization Server Metadata

   Authorization servers supporting metadata MUST make a JSON document
   containing metadata as specified in Section 2 available at a path
   formed by concatenating a well-known URI string such as "/.well-
   known/oauth-authorization-server" to the authorization server's
   issuer identifier.  This path MUST use the "https" scheme.  The
   syntax and semantics of ".well-known" are defined in RFC 5785
   [RFC5785].  The well-known URI path suffix used MUST be registered in
   the IANA "Well-Known URIs" registry [IANA.well-known].

   Different applications utilizing OAuth authorization servers in
   application-specific ways may define and register different well-
   known URI path suffixes used to publish authorization server metadata
   as used by those applications.  For instance, if the Example
   application uses an OAuth authorization server in an Example-specific
   way, and there are Example-specific metadata values that it needs to
   publish, then it might register and use the "example-configuration"
   URI path suffix and publish the metadata document at the path formed
   by concatenating "/.well-known/example-configuration" to the
   authorization server's issuer identifier.

   An OAuth 2.0 application using this specification MUST specify what
   well-known URI string it will use for this purpose.  The same
   authorization server MAY choose to publish its metadata at multiple
   well-known locations relative to its issuer identifier, for example,
   publishing metadata at both "/.well-known/example-configuration" and
   "/.well-known/oauth-authorization-server".

   Some OAuth applications will choose to use the well-known URI path
   suffix "openid-configuration" and publish the metadata document at
   the path formed by concatenating "/.well-known/openid-configuration"
   to the authorization server's issuer identifier.  As described in
   Section 5, despite the identifier "/.well-known/openid-
   configuration", appearing to be OpenID-specific, its usage in this




Jones, et al.            Expires March 11, 2018                 [Page 8]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   specification is actually referring to a general OAuth 2.0 feature
   that is not specific to OpenID Connect.

3.1.  Authorization Server Metadata Request

   An authorization server metadata document MUST be queried using an
   HTTP "GET" request at the previously specified path.

   The client would make the following request when the issuer
   identifier is "https://example.com" and the well-known URI path
   suffix is "oauth-authorization-server" to obtain the metadata, since
   the issuer identifier contains no path component:

     GET /.well-known/oauth-authorization-server HTTP/1.1
     Host: example.com

   If the issuer identifier value contains a path component, any
   terminating "/" MUST be removed before appending "/.well-known/" and
   the well-known URI path suffix.  The client would make the following
   request when the issuer identifier is "https://example.com/issuer1"
   and the well-known URI path suffix is "oauth-authorization-server" to
   obtain the metadata, since the issuer identifier contains a path
   component:

     GET /issuer1/.well-known/oauth-authorization-server HTTP/1.1
     Host: example.com

   Using path components enables supporting multiple issuers per host.
   This is required in some multi-tenant hosting configurations.  This
   use of ".well-known" is for supporting multiple issuers per host;
   unlike its use in RFC 5785 [RFC5785], it does not provide general
   information about the host.

3.2.  Authorization Server Metadata Response

   The response is a set of claims about the authorization server's
   configuration, including all necessary endpoints and public key
   location information.  A successful response MUST use the 200 OK HTTP
   status code and return a JSON object using the "application/json"
   content type that contains a set of claims as its members that are a
   subset of the metadata values defined in Section 2.  Other claims MAY
   also be returned.

   Claims that return multiple values are represented as JSON arrays.
   Claims with zero elements MUST be omitted from the response.

   An error response uses the applicable HTTP status code value.




Jones, et al.            Expires March 11, 2018                 [Page 9]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   The following is a non-normative example response:

     HTTP/1.1 200 OK
     Content-Type: application/json

     {
      "issuer":
        "https://server.example.com",
      "authorization_endpoint":
        "https://server.example.com/authorize",
      "token_endpoint":
        "https://server.example.com/token",
      "token_endpoint_auth_methods_supported":
        ["client_secret_basic", "private_key_jwt"],
      "token_endpoint_auth_signing_alg_values_supported":
        ["RS256", "ES256"],
      "userinfo_endpoint":
        "https://server.example.com/userinfo",
      "jwks_uri":
        "https://server.example.com/jwks.json",
      "registration_endpoint":
        "https://server.example.com/register",
      "scopes_supported":
        ["openid", "profile", "email", "address",
         "phone", "offline_access"],
      "response_types_supported":
        ["code", "code token"],
      "service_documentation":
        "http://server.example.com/service_documentation.html",
      "ui_locales_supported":
        ["en-US", "en-GB", "en-CA", "fr-FR", "fr-CA"]
     }

3.3.  Authorization Server Metadata Validation

   The "issuer" value returned MUST be identical to the authorization
   server's issuer identifier value that was concatenated with the well-
   known URI path suffix to create the URL used to retrieve the
   metadata.  If these values are not identical, the data contained in
   the response MUST NOT be used.

4.  String Operations

   Processing some OAuth 2.0 messages requires comparing values in the
   messages to known values.  For example, the member names in the
   metadata response might be compared to specific member names such as
   "issuer".  Comparing Unicode [UNICODE] strings, however, has
   significant security implications.



Jones, et al.            Expires March 11, 2018                [Page 10]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   Therefore, comparisons between JSON strings and other Unicode strings
   MUST be performed as specified below:

   1.  Remove any JSON applied escaping to produce an array of Unicode
       code points.

   2.  Unicode Normalization [USA15] MUST NOT be applied at any point to
       either the JSON string or to the string it is to be compared
       against.

   3.  Comparisons between the two strings MUST be performed as a
       Unicode code point to code point equality comparison.

5.  Compatibility Notes

   The identifiers "/.well-known/openid-configuration", "op_policy_uri",
   and "op_tos_uri" contain strings referring to the OpenID Connect
   [OpenID.Core] family of specifications that were originally defined
   by "OpenID Connect Discovery 1.0" [OpenID.Discovery].  Despite the
   reuse of these identifiers that appear to be OpenID-specific, their
   usage in this specification is actually referring to general OAuth
   2.0 features that are not specific to OpenID Connect.

6.  Security Considerations

6.1.  TLS Requirements

   Implementations MUST support TLS.  Which version(s) ought to be
   implemented will vary over time, and depend on the widespread
   deployment and known security vulnerabilities at the time of
   implementation.  The authorization server MUST support TLS version
   1.2 [RFC5246] and MAY support additional transport-layer security
   mechanisms meeting its security requirements.  When using TLS, the
   client MUST perform a TLS/SSL server certificate check, per RFC 6125
   [RFC6125].  Implementation security considerations can be found in
   Recommendations for Secure Use of TLS and DTLS [BCP195].

   To protect against information disclosure and tampering,
   confidentiality protection MUST be applied using TLS with a
   ciphersuite that provides confidentiality and integrity protection.

6.2.  Impersonation Attacks

   TLS certificate checking MUST be performed by the client, as
   described in Section 6.1, when making an authorization server
   metadata request.  Checking that the server certificate is valid for
   the issuer identifier URL prevents man-in-middle and DNS-based
   attacks.  These attacks could cause a client to be tricked into using



Jones, et al.            Expires March 11, 2018                [Page 11]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   an attacker's keys and endpoints, which would enable impersonation of
   the legitimate authorization server.  If an attacker can accomplish
   this, they can access the resources that the affected client has
   access to using the authorization server that they are impersonating.

   An attacker may also attempt to impersonate an authorization server
   by publishing a metadata document that contains an "issuer" claim
   using the issuer identifier URL of the authorization server being
   impersonated, but with its own endpoints and signing keys.  This
   would enable it to impersonate that authorization server, if accepted
   by the client.  To prevent this, the client MUST ensure that the
   issuer identifier URL it is using as the prefix for the metadata
   request exactly matches the value of the "issuer" metadata value in
   the authorization server metadata document received by the client.

6.3.  Publishing Metadata in a Standard Format

   Publishing information about the authorization server in a standard
   format makes it easier for both legitimate clients and attackers to
   use the authorization server.  Whether an authorization server
   publishes its metadata in an ad-hoc manner or in the standard format
   defined by this specification, the same defenses against attacks that
   might be mounted that use this information should be applied.

6.4.  Protected Resources

   Secure determination of appropriate protected resources to use with
   an authorization server for all use cases is out of scope of this
   specification.  This specification assumes that the client has a
   means of determining appropriate protected resources to use with an
   authorization server and that the client is using the correct
   metadata for each authorization server.  Implementers need to be
   aware that if an inappropriate protected resource is used by the
   client, that an attacker may be able to act as a man-in-the-middle
   proxy to a valid protected resource without it being detected by the
   authorization server or the client.

   The ways to determine the appropriate protected resources to use with
   an authorization server are in general, application-dependent.  For
   instance, some authorization servers are used with a fixed protected
   resource or set of protected resources, the locations of which may be
   well known, or which could be published as metadata values by the
   authorization server.  In other cases, the set of resources that can
   be used with an authorization server can by dynamically changed by
   administrative actions.  Many other means of determining appropriate
   associations between authorization servers and protected resources
   are also possible.




Jones, et al.            Expires March 11, 2018                [Page 12]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


7.  IANA Considerations

   The following registration procedure is used for the registry
   established by this specification.

   Values are registered on a Specification Required [RFC5226] basis
   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 Experts may approve registration once they are
   satisfied that such a specification will be published.

   Registration requests sent to the mailing list for review should use
   an appropriate subject (e.g., "Request to register OAuth
   Authorization Server Metadata: example").

   Within the review period, the Designated Experts 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.
   Registration requests that are undetermined for a period longer than
   21 days can be brought to the IESG's attention (using the
   iesg@ietf.org mailing list) for resolution.

   Criteria that should be applied by the Designated Experts includes
   determining whether the proposed registration duplicates existing
   functionality, determining whether it is likely to be of general
   applicability or whether it is useful only for a single application,
   and whether the registration makes sense.

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

   It is suggested that multiple Designated Experts be appointed who are
   able to represent the perspectives of different applications using
   this specification, in order to enable broadly-informed review of
   registration decisions.  In cases where a registration decision could
   be perceived as creating a conflict of interest for a particular
   Expert, that Expert should defer to the judgment of the other
   Experts.

7.1.  OAuth Authorization Server Metadata Registry

   This specification establishes the IANA "OAuth Authorization Server
   Metadata" registry for OAuth 2.0 authorization server metadata names.
   The registry records the authorization server metadata member and a
   reference to the specification that defines it.



Jones, et al.            Expires March 11, 2018                [Page 13]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


7.1.1.  Registration Template

   Metadata Name:
      The name requested (e.g., "issuer").  This name is case-sensitive.
      Names may not match other registered names in a case-insensitive
      manner unless the Designated Experts state that there is a
      compelling reason to allow an exception.

   Metadata Description:
      Brief description of the metadata (e.g., "Issuer identifier URL").

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

   Specification Document(s):
      Reference to the document or documents that specify the parameter,
      preferably including URIs that can be used to retrieve copies of
      the documents.  An indication of the relevant sections may also be
      included but is not required.

7.1.2.  Initial Registry Contents

   o  Metadata Name: "issuer"
   o  Metadata Description: Authorization server's issuer identifier URL
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "authorization_endpoint"
   o  Metadata Description: URL of the authorization server's
      authorization endpoint
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "token_endpoint"
   o  Metadata Description: URL of the authorization server's token
      endpoint
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "jwks_uri"
   o  Metadata Description: URL of the authorization server's JWK Set
      document
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "registration_endpoint"



Jones, et al.            Expires March 11, 2018                [Page 14]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   o  Metadata Description: URL of the authorization server's OAuth 2.0
      Dynamic Client Registration Endpoint
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "scopes_supported"
   o  Metadata Description: JSON array containing a list of the OAuth
      2.0 "scope" values that this authorization server supports
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "response_types_supported"
   o  Metadata Description: JSON array containing a list of the OAuth
      2.0 "response_type" values that this authorization server supports
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "response_modes_supported"
   o  Metadata Description: JSON array containing a list of the OAuth
      2.0 "response_mode" values that this authorization server supports
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "grant_types_supported"
   o  Metadata Description: JSON array containing a list of the OAuth
      2.0 grant type values that this authorization server supports
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "token_endpoint_auth_methods_supported"
   o  Metadata Description: JSON array containing a list of client
      authentication methods supported by this token endpoint
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "token_endpoint_auth_signing_alg_values_supported"
   o  Metadata Description: JSON array containing a list of the JWS
      signing algorithms supported by the token endpoint for the
      signature on the JWT used to authenticate the client at the token
      endpoint
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "service_documentation"
   o  Metadata Description: URL of a page containing human-readable
      information that developers might want or need to know when using
      the authorization server
   o  Change Controller: IESG



Jones, et al.            Expires March 11, 2018                [Page 15]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "ui_locales_supported"
   o  Metadata Description: Languages and scripts supported for the user
      interface, represented as a JSON array of BCP47 language tag
      values
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "op_policy_uri"
   o  Metadata Description: URL that the authorization server provides
      to the person registering the client to read about the
      authorization server's requirements on how the client can use the
      data provided by the authorization server
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "op_tos_uri"
   o  Metadata Description: URL that the authorization server provides
      to the person registering the client to read about the
      authorization server's terms of service
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "revocation_endpoint"
   o  Metadata Description: URL of the authorization server's OAuth 2.0
      revocation endpoint
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "revocation_endpoint_auth_methods_supported"
   o  Metadata Description: JSON array containing a list of client
      authentication methods supported by this revocation endpoint
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name:
      "revocation_endpoint_auth_signing_alg_values_supported"
   o  Metadata Description: JSON array containing a list of the JWS
      signing algorithms supported by the revocation endpoint for the
      signature on the JWT used to authenticate the client at the
      revocation endpoint
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "introspection_endpoint"
   o  Metadata Description: URL of the authorization server's OAuth 2.0
      introspection endpoint



Jones, et al.            Expires March 11, 2018                [Page 16]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "introspection_endpoint_auth_methods_supported"
   o  Metadata Description: JSON array containing a list of client
      authentication methods supported by this introspection endpoint
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name:
      "introspection_endpoint_auth_signing_alg_values_supported"
   o  Metadata Description: JSON array containing a list of the JWS
      signing algorithms supported by the introspection endpoint for the
      signature on the JWT used to authenticate the client at the
      introspection endpoint
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Metadata Name: "code_challenge_methods_supported"
   o  Metadata Description: PKCE code challenge methods supported by
      this authorization server
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

7.2.  Updated Registration Instructions

   This specification adds to the instructions for the Designated
   Experts of the following IANA registries, both of which are in the
   "OAuth Parameters" registry [IANA.OAuth.Parameters]:

   o  OAuth Access Token Types
   o  OAuth Token Endpoint Authentication Methods

   IANA has added a link to this specification in the Reference sections
   of these registries.  [[ RFC Editor: The above sentence is written in
   the past tense as it would appear in the final specification, even
   though these links won't actually be created until after the IESG has
   requested publication of the specification.  Please delete this note
   after the links are in place. ]]

   For these registries, the designated experts must reject registration
   requests in one registry for values already occurring in the other
   registry.  This is necessary because the
   "introspection_endpoint_auth_methods_supported" parameter allows for
   the use of values from either registry.  That way, because the values
   in the two registries will continue to be mutually exclusive, no
   ambiguities will arise.




Jones, et al.            Expires March 11, 2018                [Page 17]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


7.3.  Well-Known URI Registry

   This specification registers the well-known URI defined in Section 3
   in the IANA "Well-Known URIs" registry [IANA.well-known] established
   by RFC 5785 [RFC5785].

7.3.1.  Registry Contents

   o  URI suffix: "oauth-authorization-server"
   o  Change controller: IESG
   o  Specification document: Section 3 of [[ this specification ]]
   o  Related information: (none)

8.  References

8.1.  Normative References

   [BCP195]   Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <http://www.rfc-editor.org/info/bcp195>.

   [IANA.OAuth.Parameters]
              IANA, "OAuth Parameters",
              <http://www.iana.org/assignments/oauth-parameters>.

   [JWE]      Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
              RFC 7516, DOI 10.17487/RFC7516, May 2015,
              <http://tools.ietf.org/html/rfc7516>.

   [JWK]      Jones, M., "JSON Web Key (JWK)", RFC 7517,
              DOI 10.17487/RFC7517, May 2015,
              <http://tools.ietf.org/html/rfc7517>.

   [JWS]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <http://tools.ietf.org/html/rfc7515>.

   [JWT]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <http://tools.ietf.org/html/rfc7519>.

   [OAuth.Post]
              Jones, M. and B. Campbell, "OAuth 2.0 Form Post Response
              Mode", April 2015, <http://openid.net/specs/
              oauth-v2-form-post-response-mode-1_0.html>.




Jones, et al.            Expires March 11, 2018                [Page 18]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   [OAuth.Responses]
              de Medeiros, B., Ed., Scurtescu, M., Tarjan, P., and M.
              Jones, "OAuth 2.0 Multiple Response Type Encoding
              Practices", February 2014, <http://openid.net/specs/
              oauth-v2-multiple-response-types-1_0.html>.

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

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

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

   [RFC5646]  Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
              Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
              September 2009, <https://www.rfc-editor.org/info/rfc5646>.

   [RFC5785]  Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
              Uniform Resource Identifiers (URIs)", RFC 5785,
              DOI 10.17487/RFC5785, April 2010,
              <https://www.rfc-editor.org/info/rfc5785>.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
              2011, <https://www.rfc-editor.org/info/rfc6125>.

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

   [RFC7009]  Lodderstedt, T., Ed., Dronia, S., and M. Scurtescu, "OAuth
              2.0 Token Revocation", RFC 7009, DOI 10.17487/RFC7009,
              August 2013, <https://www.rfc-editor.org/info/rfc7009>.

   [RFC7033]  Jones, P., Salgueiro, G., Jones, M., and J. Smarr,
              "WebFinger", RFC 7033, DOI 10.17487/RFC7033, September
              2013, <https://www.rfc-editor.org/info/rfc7033>.



Jones, et al.            Expires March 11, 2018                [Page 19]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


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

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

   [RFC7636]  Sakimura, N., Ed., Bradley, J., and N. Agarwal, "Proof Key
              for Code Exchange by OAuth Public Clients", RFC 7636,
              DOI 10.17487/RFC7636, September 2015,
              <https://www.rfc-editor.org/info/rfc7636>.

   [RFC7662]  Richer, J., Ed., "OAuth 2.0 Token Introspection",
              RFC 7662, DOI 10.17487/RFC7662, October 2015,
              <https://www.rfc-editor.org/info/rfc7662>.

   [UNICODE]  The Unicode Consortium, "The Unicode Standard",
              <http://www.unicode.org/versions/latest/>.

   [USA15]    Davis, M. and K. Whistler, "Unicode Normalization Forms",
              Unicode Standard Annex 15, June 2015,
              <http://www.unicode.org/reports/tr15/>.

8.2.  Informative References

   [I-D.ietf-oauth-mix-up-mitigation]
              Jones, M., Bradley, J., and N. Sakimura, "OAuth 2.0 Mix-Up
              Mitigation", draft-ietf-oauth-mix-up-mitigation-01 (work
              in progress), July 2016.

   [IANA.well-known]
              IANA, "Well-Known URIs",
              <http://www.iana.org/assignments/well-known-uris>.

   [OpenID.Core]
              Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
              C. Mortimore, "OpenID Connect Core 1.0", November 2014,
              <http://openid.net/specs/openid-connect-core-1_0.html>.

   [OpenID.Discovery]
              Sakimura, N., Bradley, J., Jones, M., and E. Jay, "OpenID
              Connect Discovery 1.0", November 2014,
              <http://openid.net/specs/
              openid-connect-discovery-1_0.html>.





Jones, et al.            Expires March 11, 2018                [Page 20]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   [OpenID.Registration]
              Sakimura, N., Bradley, J., and M. Jones, "OpenID Connect
              Dynamic Client Registration 1.0", November 2014,
              <http://openid.net/specs/
              openid-connect-registration-1_0.html>.

Appendix A.  Acknowledgements

   This specification is based on the OpenID Connect Discovery 1.0
   specification, which was produced by the OpenID Connect working group
   of the OpenID Foundation.

   The authors would like to thank the following people for their
   reviews of this specification: Brian Campbell, William Denniss,
   Vladimir Dzhuvinov, Samuel Erdtman, George Fletcher, Phil Hunt, Tony
   Nadalin, Eric Rescorla, Justin Richer, Hannes Tschofenig, and Hans
   Zandbelt.

Appendix B.  Document History

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

   -07

   o  Applied clarifications suggested by EKR.

   -06

   o  Incorporated resolutions to working group last call comments.

   -05

   o  Removed the "protected_resources" element and the reference to
      draft-jones-oauth-resource-metadata.

   -04

   o  Added the ability to list protected resources with the
      "protected_resources" element.

   o  Added ability to provide signed metadata with the
      "signed_metadata" element.

   o  Removed "Discovery" from the name, since this is now just about
      authorization server metadata.

   -03




Jones, et al.            Expires March 11, 2018                [Page 21]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   o  Changed term "issuer URL" to "issuer identifier" for terminology
      consistency, paralleling the same terminology consistency change
      in the mix-up mitigation spec.

   -02

   o  Changed the title to OAuth 2.0 Authorization Server Discovery
      Metadata.

   o  Made "jwks_uri" and "registration_endpoint" OPTIONAL.

   o  Defined the well-known URI string "/.well-known/oauth-
      authorization-server".

   o  Added security considerations about publishing authorization
      server discovery metadata in a standard format.

   o  Added security considerations about protected resources.

   o  Added more information to the "grant_types_supported" and
      "response_types_supported" definitions.

   o  Referenced the working group Mix-Up Mitigation draft.

   o  Changed some example metadata values.

   o  Acknowledged individuals for their contributions to the
      specification.

   -01

   o  Removed WebFinger discovery.

   o  Clarified the relationship between the issuer identifier URL and
      the well-known URI path relative to it at which the discovery
      metadata document is located.

   -00

   o  Created the initial working group version based on draft-jones-
      oauth-discovery-01, with no normative changes.

Authors' Addresses








Jones, et al.            Expires March 11, 2018                [Page 22]


Internet-Draft   OAuth 2.0 Authorization Server Metadata  September 2017


   Michael B. Jones
   Microsoft

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


   Nat Sakimura
   Nomura Research Institute, Ltd.

   Email: n-sakimura@nri.co.jp
   URI:   http://nat.sakimura.org/


   John Bradley
   Ping Identity

   Email: ve7jtb@ve7jtb.com
   URI:   http://www.thread-safe.com/
































Jones, et al.            Expires March 11, 2018                [Page 23]


Html markup produced by rfcmarkup 1.123, available from https://tools.ietf.org/tools/rfcmarkup/