OAuth Working Group                                       J. Richer, Ed.
Internet-Draft                                     The MITRE Corporation
Intended status: Standards Track                            May 01, 2013
Expires: November 02, 2013

                       OAuth Token Introspection


   This specification defines a method for a client or protected
   resource to query an OAuth authorization server to determine meta-
   information about an OAuth token.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

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
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   This Internet-Draft will expire on November 02, 2013.

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

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   to this document.  Code Components extracted from this document must
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Introspection Endpoint  . . . . . . . . . . . . . . . . . . .   2
     2.1.  Introspection Request . . . . . . . . . . . . . . . . . .   3
     2.2.  Introspection Response  . . . . . . . . . . . . . . . . .   3
     2.3.  Non-normative Example . . . . . . . . . . . . . . . . . .   4
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   In OAuth, the contents of tokens are opaque to clients.  This means
   that the client does not need to know anything about the content or
   structure of the token itself, if there is any.  However, there is
   still a large amount of metadata that may be attached to a token,
   such as its current validity, approved scopes, and extra information
   about the authentication context in which the token was issued.
   These pieces of information are often vital to Protected Resources
   making authorization decisions based on the tokens being presented.
   Since OAuth2 defines no direct relationship between the Authorization
   Server and the Protected Resource, only that they must have an
   agreement on the tokens themselves, there have been many different
   approaches to bridging this gap.

   This specification defines an Introspection Endpoint that allows the
   holder of a token to query the Authorization Server to discover the
   set of metadata for a token.  A Protected Resource may use the
   mechanism described in this draft to query the Introspection Endpoint
   in a particular authorization decision context and ascertain the
   relevant metadata about the token in order to make this authorization
   decision appropriately.

2.  Introspection Endpoint

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   The Introspection Endpoint is an OAuth 2 Endpoint that responds to
   HTTP POST requests (and optionally HTTP GET requests) from token
   holders, particularly including Resource Servers and Clients.  The
   endpoint takes a single parameter representing the token (and
   optionally further authentication) and returns a JSON document
   representing the meta information surrounding the token.

   The endpoint MUST be protected by TLS or equivalent.

2.1.  Introspection Request

   token  REQUIRED.  The string value of the token.

   resource_id  OPTIONAL.  A service-specific string identifying the
      resource that the client doing the introspection is asking about.

   token_type_hint  OPTIONAL.  A hint about the type of the token
      submitted for revocation.  Clients MAY pass this parameter in
      order to help the authorization server to optimize the token
      lookup.  If the server is unable to locate the token using the
      given hint, it MUST extend its search accross all of its supported
      token types.  An authorization server MAY ignore this parameter,
      particularly if it is able to detect the token type automatically.
      Values for this field are defined in OAuth Token Revocation

   The endpoint MAY allow other parameters to provide context to the
   query.  For instance, an authorization service may need to know the
   IP address of the Client in order to determine the appropriateness of
   the token being presented.

   The endpoint SHOULD also require some form of authentication to
   access this endpoint, such as the Client Authentication as described
   in OAuth 2 Core Specification [RFC6749] or a separate OAuth 2.0
   Access Token.  The methods of managing and validating these
   authentication credentials are out of scope of this specification.

2.2.  Introspection Response

   The server responds with a JSON object [RFC4627] in "application/
   json" format with the following top-level members.  Specific
   implementations MAY extend this structure with their own service-
   specific pieces of information.

   active  REQUIRED.  Boolean indicator of whether or not the presented
      token is currently active.

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   exp  OPTIONAL.  Integer timestamp, measured in the number of seconds
      since January 1 1970 UTC, indicating when this token will expire.

   iat  OPTIONAL.  Integer timestamp, measured in the number of seconds
      since January 1 1970 UTC, indicating when this token was
      originally issued.

   scope  OPTIONAL.  A space-separated list of strings representing the
      scopes associated with this token, in the format described in
      Section 3.3 of OAuth 2.0 [RFC6749].

   client_id  OPTIONAL.  Client Identifier for the OAuth Client that
      requested this token.

   sub  OPTIONAL.  Local identifier of the Resource Owner who authorized
      this token.

   aud  OPTIONAL.  Service-specific string identifier or list of string
      identifiers representing the intended audience for this token.

   token_type  OPTIONAL.  Type of the token as defined in OAuth 2.0
      section 5.1.

2.3.  Non-normative Example

   For example, a Protected Resource accepts a request from a Client
   carrying an OAuth2 Bearer Token.  In order to know how and whether to
   serve the request, the Protected Resource then makes the following
   request to the Introspection Endpoint of the Authorization Server.
   The Protected Resource is here authenticating with its own Client ID
   and Client Secret as per OAuth2 [RFC6749] Section 2.3.1.

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

   POST /register HTTP/1.1
   Accept: application/x-www-form-urlencoded
   Host: server.example.com
   Authorization: Basic czZCaGRSa3F0Mzo3RmpmcDBaQnIxS3REUmJuZlZkbUl3


   The Authorization Server validates the client credentials and looks
   up the information in the token.  If the token is currently active,
   it returns the following JSON document.

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

   HTTP/1.1 200 OK
   Content-Type: application/json
   Cache-Control: no-store

    "active": true,
    "scope": "read write dolphin",
    "sub": "2309fj32kl",
    "aud": "http://example.org/protected-resource/*"

   If the token presented is not currently active (but the
   authentication presented is valid), it returns the following JSON

   Following is a non-normative example response to an inactive or
   invalid token (with line wraps for display purposes only):

   HTTP/1.1 200 OK
   Content-Type: application/json
   Cache-Control: no-store

    "active": false

   If the client credentials are invalid or there is another error, the
   Authorization Server responds with an HTTP 400 (Bad Request) as
   described in OAuth 2.0 section 5.2 [RFC6749].

3.  IANA Considerations

   This document makes no request of IANA.

4.  Security Considerations

   If left unprotected and un-throttled, the Introspection Endpoint
   could present a means for an attacker to poll a series of possible
   token values, fishing for a valid token.  Therefore, the
   Authorization Server SHOULD issue special client credentials to any
   protected resources or clients that need to access the introspection
   endpoint.  These credentials may be used directly at the endpoint, or

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   they may be exchanged for an OAuth2 Access token scoped specifically
   for the Introspection Endpoint.

   Since the introspection endpoint takes in OAuth 2 tokens as
   parameters, it MUST be protected by TLS or equivalent.  A server MAY
   require an HTTP POST method only to the endpoint.

5.  Acknowledgements

   Thanks to the OAuth Working Group and the UMA Working Group for

6.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

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

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

              Lodderstedt, T., "OAuth Token Revocation", April 2013.

Author's Address

   Justin Richer (editor)
   The MITRE Corporation

   Email: jricher@mitre.org

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