OAuth Working Group P. Hunt
Internet-Draft Oracle
Intended status: Standards Track A. Nadalin
Expires: September 14, 2016 Microsoft
March 13, 2016

OAuth 2.0 Bound Configuration Lookup
draft-hunt-oauth-bound-config-00

Abstract

This specification defines a mechanism for the client of an OAuth 2.0 protected resource service to obtain the configuration details of an OAuth 2.0 authorization server that is capable of authorizing access to a specific resource service. The information includes the OAuth 2.0 component endpoint location URIs and as well as 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 http://datatracker.ietf.org/drafts/current/.

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

This Internet-Draft will expire on September 14, 2016.

Copyright Notice

Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

Table of Contents

1. Introduction

This specification generalizes the configuration metadata format defined by "OpenID Connect Discovery 1.0" [OpenID.Discovery] to support 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.

[[Editors note: This draft is intended as a replacement alternative for consideration to draft-ietf-oauth-discovery-01 and as such it contains the same metadata attribute definitions and registry requirements rather than references the original draft.]]

This specification enables clients, having previously discovered an OAuth 2.0 protected resource and an OAuth 2.0 Authorization service (through other means such as an administrative process, a configuration file, use of ".well-known" [RFC5785]), to discover the OAuth 2.0 configuration metadata and to confirm the relationship between the previously discovered authorization server and the protected resource endpoints through the use of query mechanism. This specification uses WebFinger [RFC7033] to query the authorization server configuration discovery to locate the assigned authorization server (if any) for a specified resource endpoint URI and its configuration properties as an authoritative set. This process is described in Section 2.

The use WebFinger serves the following purposes:

Once the authorization server has been identified, this specification provides the configuration information that is retrieved from a well-known location as a JSON [RFC7159] document, including its OAuth 2.0 endpoint locations and authorization server capabilities. This process is described in Section 2.

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].

This specification also defines the following terms:

Resource

Entity that is the target of a request in WebFinger.
Host

Server where a WebFinger service is hosted.

2. Authorization Server WebFinger Discovery

Authorization server WebFinger discovery is a means of determining the location of the authorization server's configuration information.

WebFinger discovery is RECOMMENDED; if a client knows the authorization server's configuration information location through an out-of-band mechanism, it can skip this step and proceed to Section 2.

WebFinger discovery uses the following information to make a discovery request:

resource

A REQUIRED URI that represents the actual resource URL the client intends to use to access the protected resource. This URL may be for a specific sub-set of data (e.g. associated with a resource owner), or it MAY be the base URL for a set of protected resources accessible within the scope of the client's anticipated access authorization. The URI also be the base URL for a service when the end-user is a new user and no specific user-owned resource is defined.
host

The server where the WebFinger service is hosted.
rel

The URI identifying the type of service whose location is being requested.

OAuth 2.0 configuration discovery uses the following rel value in WebFinger [RFC7033]:

Rel Type URI
OAuth 2.0 Configuration Information oauth2

To start discovery of OAuth 2.0 configuration information, the client first discover's the resource endpoint and the associated OAuth URI through a mechanism defined by the resource service provider. The parameter resource, whose value is the protected resource's endpoint URL MUST be included.

The client then makes an HTTP GET request to the OAuth host's WebFinger [RFC7033] endpoint using the URI as the resource parameter value and the rel value oauth2 to obtain the authorization server's configuration information location.

Upon receiving a request, the WebFinger service MAY match the specified resource value through specific value matches or the service MAY match a subset of the URI such as the host name and an initial path. For example, if the client is using a URI to a specific subset of resources, the subset can be ignored.

In the response, one or more matches MAY be returned in the links array element. Each array element MUST contain a rel attribute, an href attribute, and a properties attribute.

The value of the href shall contain a value equivalent to the OAuth "issuer" (see Section 3). The value of rel is oauth2.

The properties attribute contains the authorization server configuration metadata (see Section 3) that corresponds to the OAuth 2.0 server identified in the href attribute. This information includes a set of claims about the authorization server's configuration, including all necessary endpoints and public key location information that contains a set of claims as its members that are a subset of the metadata values defined in Section 3. 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 example WebFinger discovery request follows. To find the authorization server's configuration information for the resource https://finance.example.com/abcpath", the WebFinger parameters are as follows:

WebFinger Parameter Value
resource https://finance.example.com/abcpath
host example.com
rel oauth2

The client would make the following WebFinger request to discover the authorization server's configuration information location (with line wraps within lines for display purposes only): 

  GET /.well-known/webfinger
    ?resource=https%3A%2F%2Ffinance.example.com%2Fabcpath
    &rel=oauth2
    HTTP/1.1
  Host: example.com

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

  {
   "subject": "https://finance.example.com",
   "links":
    [
     {
      "rel": "oauth2",
      "href": "https://server.example.com",
      "properties":
      {
        "issuer":
          "https://server.example.com",
        "authorization_endpoint":
          "https://server.example.com/oauth/authorize",
        "token_endpoint":
          "https://server.example.com/oauth/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/oauth/userinfo",
        "jwks_uri":
          "https://server.example.com/jwks.json",
        "registration_endpoint":
          "https://server.example.com/oauth/register",
        "scopes_supported":
          ["openid", "profile", "email", "address",
           "phone", "offline_access"],
        "response_types_supported":
          ["code", "code token"],
        "service_documentation":
          "http://server.example.com/oauth/service_documentation.html",
        "ui_locales_supported":
          ["en-US", "en-GB", "en-CA", "fr-FR", "fr-CA"]
      } 
     }
    ]
  }

The discovered authorization server is identified as https://server.example.com.

In the event that the authorization server does not support the requested resource, the server MUST indicate that it was unable to match the request as per Section 4.2 [RFC7033].

If any of the validation procedures defined in this specification fail, any operations requiring the information that failed to correctly validate MUST be aborted and the information that failed to validate MUST NOT be used.

The issuer value returned MUST be identical to the configuration information location URL that was directly used to retrieve the configuration information.

3. Authorization Server Metadata

Authorization servers can have metadata describing their configuration. These authorization server metadata values are used by this specification:

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 2. The issuer identifier is used to prevent authorization server mix-up attacks, as described in "OAuth 2.0 Mix-Up Mitigation" [I-D.jones-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

RECOMMMENDED. URL of the authorization server's JWK Set [JWK] document. This contains the signing key(s) the client uses to validate signatures from the authorization server. The JWK Set MAY also contain the Server's encryption key(s), which are used by RPs 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. Although some algorithms allow the same key to be used for both signatures and encryption, doing so is NOT RECOMMENDED, as it is less secure. The JWK x5c parameter MAY be used to provide X.509 representations of keys provided. When used, the bare key values MUST still be present and MUST match those in the certificate.
registration_endpoint

RECOMMENDED. 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.
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. 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. 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.
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 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].
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. The value none MUST NOT be used.
introspection_endpoint

OPTIONAL. URL of the authorization server's OAuth 2.0 introspection endpoint [RFC7662].
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 7.3.)
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. 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].

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

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 configuration information response might be compared to specific member names such as issuer. Comparing Unicode [UNICODE] strings, however, has significant security implications.

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 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 configuration information request. Checking that the server certificate is valid for the configuration information location URL prevents man-in-middle and DNS-based attacks. These attacks could cause a client to be tricked into using 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 discovery document that contains an issuer claim using the configuration information location 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, RPs MUST ensure that the configuration information location URL they are using for the configuration information request exactly matches the value of the issuer metadata value in the authorization server configuration information document received by the client.

7. IANA Considerations

7.1. Registration of OAuth2 Relation Type

This section registers the WebFinger link relation type oauth2 as per Section 6.2.1 of [RFC5988].

Relation Name:
oauth2
Description:
Refers to discovery of OAuth2 configuration metadata.
Reference:
This specification.

7.2. OAuth Discovery Metadata Registry

This specification establishes the IANA "OAuth Discovery 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.

7.2.1. Metadata Registry Procedures

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 Discovery 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.

7.2.2. Registration Template

Discovery 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.
Discovery Metadata Description:

Brief description of the discovery metadata (e.g., "Issuer 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.

7.2.3. Initial Registry Contents

7.3. 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]:

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.

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.
[IANA.OAuth.Parameters] IANA, "OAuth Parameters"
[JWA] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, DOI 10.17487/RFC7518, May 2015.
[JWE] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", RFC 7516, DOI 10.17487/RFC7516, May 2015.
[JWK] Jones, M., "JSON Web Key (JWK)", RFC 7517, DOI 10.17487/RFC7517, May 2015.
[JWS] Jones, M., Bradley, J. and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015.
[JWT] Jones, M., Bradley, J. and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015.
[OAuth.Post] Jones, M. and B. Campbell, "OAuth 2.0 Form Post Response Mode", April 2015.
[OAuth.Responses] de Medeiros, B., Scurtescu, M., Tarjan, P. and M. Jones, "OAuth 2.0 Multiple Response Type Encoding Practices", February 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, DOI 10.17487/RFC2246, January 1999.
[RFC3986] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008.
[RFC5646] Phillips, A. and M. Davis, "Tags for Identifying Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646, September 2009.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known Uniform Resource Identifiers (URIs)", RFC 5785, DOI 10.17487/RFC5785, April 2010.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, DOI 10.17487/RFC5988, October 2010.
[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.
[RFC6749] Hardt, D., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012.
[RFC7009] Lodderstedt, T., Dronia, S. and M. Scurtescu, "OAuth 2.0 Token Revocation", RFC 7009, DOI 10.17487/RFC7009, August 2013.
[RFC7033] Jones, P., Salgueiro, G., Jones, M. and J. Smarr, "WebFinger", RFC 7033, DOI 10.17487/RFC7033, September 2013.
[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 2014.
[RFC7565] Saint-Andre, P., "The 'acct' URI Scheme", RFC 7565, DOI 10.17487/RFC7565, May 2015.
[RFC7591] Richer, J., Jones, M., Bradley, J., Machulak, M. and P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol", RFC 7591, DOI 10.17487/RFC7591, July 2015.
[RFC7636] Sakimura, N., Bradley, J. and N. Agarwal, "Proof Key for Code Exchange by OAuth Public Clients", RFC 7636, DOI 10.17487/RFC7636, September 2015.
[RFC7662] Richer, J., "OAuth 2.0 Token Introspection", RFC 7662, DOI 10.17487/RFC7662, October 2015.
[UNICODE] The Unicode Consortium, "The Unicode Standard"
[USA15] Davis, M. and K. Whistler, "Unicode Normalization Forms", Unicode Standard Annex 15, June 2015.

8.2. Informative References

[I-D.jones-oauth-mix-up-mitigation] Jones, M. and J. Bradley, "OAuth 2.0 Mix-Up Mitigation", Internet-Draft draft-jones-oauth-mix-up-mitigation-01, January 2016.
[OpenID.Core] Sakimura, N., Bradley, J., Jones, M., de Medeiros, B. and C. Mortimore, "OpenID Connect Core 1.0", November 2014.
[OpenID.Discovery] Sakimura, N., Bradley, J., Jones, M. and E. Jay, "OpenID Connect Discovery 1.0", November 2014.
[OpenID.Registration] Sakimura, N., Bradley, J. and M. Jones, "OpenID Connect Dynamic Client Registration 1.0", November 2014.

Appendix A. Acknowledgements

This specification is an alternate proposal to the OAuth 2.0 Discovery working group draft (draft-ietf-oauth-discovery-01) and contains substantial text from this draft. The author would like to thank the original draft authors Mike Jones, Nat Sakimura, and John Bradley as well as the OAuth Working Group.

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

Appendix B. Document History

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

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Authors' Addresses

Phil Hunt Oracle EMail: phil.hunt@yahoo.com URI: http://www.independentid.com
Tony Nadalin Microsoft EMail: tonynad@microsoft.com