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Versions: (draft-richer-oauth-introspection) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 7662

OAuth Working Group                                       J. Richer, Ed.
Internet-Draft                                     The MITRE Corporation
Intended status: Standards Track                       December 23, 2014
Expires: June 26, 2015


                     OAuth 2.0 Token Introspection
                   draft-ietf-oauth-introspection-04

Abstract

   This specification defines a method for a protected resource to query
   an OAuth 2.0 authorization server to determine the active state of an
   OAuth 2.0 token and to determine meta-information about this token.
   OAuth 2.0 deployments can use this method to convey information about
   the authorization context of the token from the authorization server
   to the protected resource.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in 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
   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 June 26, 2015.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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   (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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Introspection Endpoint  . . . . . . . . . . . . . . . . . . .   3
     2.1.  Introspection Request . . . . . . . . . . . . . . . . . .   4
     2.2.  Introspection Response  . . . . . . . . . . . . . . . . .   5
     2.3.  Error Response  . . . . . . . . . . . . . . . . . . . . .   8
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  10
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Document History . . . . . . . . . . . . . . . . . .  11
   Appendix B.  Use with Proof of Posession Tokens . . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   In OAuth 2.0, 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 information
   about the 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
   OAuth 2.0 [RFC6749] 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.  These include using
   structured token formats such as JWT [JWT] or proprietary inter-
   service communication mechanisms (such as shared databases and
   protected enterprise service buses) that convey token information.

   This specification defines an interoperable web API that allows
   authorized protected resources to query the authorization server to
   determine the set of metadata for a given token that was presented to



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   them by an OAuth 2.0 client.  This metadata includes whether or not
   the token is currently active (or if it has expired or otherwise been
   revoked), what rights of access the token carries (usually conveyed
   through OAuth 2.0 scopes), and the authorization context in which the
   token was granted (including who authorized the token and which
   client it was issued to).  Token introspection allows a protected
   resource to query this information regardless of whether or not it is
   carried in the token itself, allowing this method to be used along
   with or independently of structured token values.  Additionally, a
   protected resource can use the mechanism described in this
   specification to introspect the token in a particular authorization
   decision context and ascertain the relevant metadata about the token
   in order to make this authorization decision appropriately.

1.1.  Terminology

   This section defines the terminology used by this specification.
   This section is a normative portion of this specification, imposing
   requirements upon implementations.

   This specification uses the terms "access token", "authorization
   endpoint", "authorization grant", "authorization server", "client",
   "client identifier", "protected resource", "refresh token", "resource
   owner", "resource server", and "token endpoint" defined by OAuth 2.0
   [RFC6749], and the terms "claim names" and "claim values" defined by
   JSON Web Token (JWT) [JWT].

2.  Introspection Endpoint

   The introspection endpoint is an OAuth 2.0 endpoint that takes a
   parameter representing an OAuth 2.0 token and returns a JSON
   [RFC7159] document representing the meta information surrounding the
   token, including whether this token is currently active.  The
   definition of an active token is up to the authorization server, but
   this is commonly a token that has been issued by this authorization
   server, is not expired, has not been revoked, and is within the
   purview of the protected resource making the introspection call.

   The introspection endpoint MUST be protected by TLS of at least
   version 1.2 RFC 5246 [RFC5246] and MAY support additional transport-
   layer mechanisms meeting its security requirements.  When using TLS,
   the protected resource 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 [TLS.BCP].






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2.1.  Introspection Request

   The protected resource calls the introspection endpoint using an HTTP
   POST [RFC7231] request with parameters sent as "application/x-www-
   form-urlencoded" data as defined in [W3C.REC-html5-20141028].  The
   authorization server MAY allow an HTTP GET [RFC7231] request with
   parameters passed in the query string as defined in
   [W3C.REC-html5-20141028].  The protected resource sends a parameter
   representing the token along with optional parameters representing
   additional context that is known by the protected resource to aid the
   authorization server in its response.

   token  REQUIRED.  The string value of the token.  For access tokens,
      this is the "access_token" value returned from the token endpoint
      defined in OAuth 2.0 [RFC6749] section 5.1.  For refresh tokens,
      this is the "refresh_token" value returned from the token endpoint
      as defined in OAuth 2.0 [RFC6749] section 5.1.  Other token types
      are outside the scope of this specification.

   token_type_hint  OPTIONAL.  A hint about the type of the token
      submitted for introspection.  The protected resource re 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 across 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 [RFC7009].

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

   To prevent unauthorized token scanning attacks, the endpoint MUST
   also require some form of authorization to access this endpoint, such
   as client authentication as described in OAuth 2.0 [RFC6749] or a
   separate OAuth 2.0 access token such as the bearer token described in
   OAuth 2.0 Bearer Token Usage [RFC6750].  The methods of managing and
   validating these authentication credentials are out of scope of this
   specification.

   For example, the following example shows a protected resource calling
   the token introspection endpoint to query about an OAuth 2.0 bearer.
   The protected resource is using a separate OAuth 2.0 bearer token to
   authorize this call.





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

     POST /introspect HTTP/1.1
     Host: server.example.com
     Accept: application/json
     Content-Type: application/x-www-form-urlencoded
     Authorization: Bearer 23410913-abewfq.123483

     token=2YotnFZFEjr1zCsicMWpAA


   In this example, the protected resource uses a client identifier and
   client secret to authenticate itself to the introspection endpoint as
   well as send a token type hint.

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

     POST /introspect HTTP/1.1
     Host: server.example.com
     Accept: application/json
     Content-Type: application/x-www-form-urlencoded
     Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW

     token=mF_9.B5f-4.1JqM&token_type_hint=access_token


2.2.  Introspection Response

   The server responds with a JSON object [RFC7159] in "application/
   json" format with the following top-level members.

   active
      REQUIRED.  Boolean indicator of whether or not the presented token
      is currently active.  The authorization server determines whether
      and when a given token is in an active state.

   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 2.0 client that
      requested this token.

   user_id



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      OPTIONAL.  Human-readable identifier for the user who authorized
      this token.

   token_type
      OPTIONAL.  Type of the token as defined in section 5.1 of OAuth
      2.0 [RFC6749].

   The response MAY include any claims defined as JWT [JWT] claim names
   and carry the same semantics and syntax, such as the following:

   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.

   nbf
      OPTIONAL.  Integer timestamp, measured in the number of seconds
      since January 1 1970 UTC, indicating when this token is not to be
      used before.

   sub
      OPTIONAL.  Subject of the token.  Usually a machine-readable
      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.

   iss
      OPTIONAL.  String representing the issuer of this token.

   jti
      OPTIONAL.  String identifier for the token.

   Specific implementations MAY extend this structure with their own
   service-specific pieces of information as top-level members of this
   JSON object.

   The authorization server MAY respond differently to different
   protected resources making the same request.  For instance, an
   authorization server MAY limit which scopes from a given token for
   each protected resources in order to prevent protected resources from
   learning more about the larger network than is necessary for their
   function.



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   The response MAY be cached by the protected resource.

   For example, the following response contains a set of information
   about an active token:

   Following is a non-normative example response:

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

     {
      "active": true,
      "client_id": "l238j323ds-23ij4",
      "user_id": "jdoe",
      "scope": "read write dolphin",
      "sub": "Z5O3upPC88QrAjx00dis",
      "aud": "https://protected.example.net/resource",
      "iss": "https://server.example.com/",
      "exp": 1419356238,
      "iat": 1419350238,
      "extension_field": "twenty-seven"
     }


   If the introspection call is properly authorized but the token is not
   active, does not exist on this server, or the protected resource is
   not allowed to introspect this particular token, the authorization
   server MUST return an introspection response with the active field
   set to false.  Note that in order to avoid disclosing too much of the
   authorization server's state to a third party, the authorization
   server SHOULD NOT include any additional information about an
   inactive token, including why the token is inactive.  For example,
   the response for a token that has been revoked or is otherwise
   invalid would look like the following:

   Following is a non-normative example response:

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

     {
      "active": false
     }








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2.3.  Error Response

   If the protected resource uses OAuth 2.0 client credentials to
   authenticate to the introspection endpoint and its credentials are
   invalid, the authorization server responds with an HTTP 401
   (Unauthorized) as described in section 5.2 of OAuth 2.0 [RFC6749].

   If the protected resource uses an OAuth 2.0 bearer token to authorize
   its call to the introspection endpoint and the token used for
   authorization does not contain sufficient privileges or is otherwise
   invalid for this request, the authorization server responds with an
   HTTP 401 code as described in section 3 of OAuth 2.0 Bearer Token
   Usage [RFC6750].

   Note that a properly formed and authorized query for an inactive or
   otherwise invalid token (or a token the protected resource is not
   allowed to know about) is not considered an error response by this
   specification.  In these cases, the authorization server MUST instead
   respond with an introspection response with the "active" field set to
   "false" as described in Section 2.2.

3.  IANA Considerations

   This specification requests IANA to register the following values
   into the IANA JSON Web Token Claims registry for JWT Claim Names.

   o  Claim Name: "active"
   o  Claim Description: Token active status
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

   o  Claim Name: "user_id"
   o  Claim Description: User identifier of the resource owner
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

   o  Claim Name: "client_id"
   o  Claim Description: Client identifier of the client
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

   o  Claim Name: "scope"
   o  Claim Description: Authorized scopes of the token
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

   o  Claim Name: "token_type"
   o  Claim Description: Type of the token



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   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

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.  To prevent this, the
   authorization server MUST require authentication of protected
   resources that need to access the introspection endpoint and SHOULD
   require protected resources to be specifically authorized to call the
   introspection endpoint.  The specifics of this authentication
   credentials are out of scope of this specification, but commonly
   these credentials could take the form of any valid client
   authentication mechanism used with the token endpoint, an OAuth 2.0
   access token, or other HTTP authorization or authentication
   mechanism.  A single piece of software acting as both a client and a
   protected resource MAY re-use the same credentials between the token
   endpoint and the introspection endpoint, though doing so potentially
   conflates the activities of the client and protected resource
   portions of the software and the authorization server MAY require
   separate credentials for each mode.

   Since the introspection endpoint takes in OAuth 2.0 tokens as
   parameters, the server MUST support TLS 1.2 RFC 5246 [RFC5246] and
   MAY support additional transport-layer mechanisms meeting its
   security requirements.  When using TLS, the client or protected
   resource 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 [TLS.BCP].

   In order to prevent the values of access tokens being from leaking
   into server-side logs via query parameters, an authorization server
   offering token introspection MAY disallow HTTP GET and instead
   require an HTTP POST method only to the introspection endpoint.

   In order to avoid disclosing internal server state, an introspection
   response for an inactive token SHOULD NOT contain any additional
   claims beyond the required "active" claim (with its value set to
   "false").

   An authorization server offering token introspection MUST be able to
   understand the token values being presented to it during this call.
   The exact means by which this happens is an implementation detail and
   outside the scope of this specification.  For unstructured tokens,
   this could take the form of a simple server-side database query
   against a data store containing the context information for the
   token.  For structured tokens, this could take the form of the server



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   parsing the token, validating its signature or other protection
   mechanisms, and returning the information contained in the token back
   to the protected resource (allowing the protected resource to be
   unaware of the token's contents, much like the client).

   Note that for tokens carrying encrypted information that is needed
   during the introspection process, the authorization server MUST be
   able to decrypt and validate the token in order to access this
   information.  Also note that in cases where the authorization server
   stores no information about the token and has no means of accessing
   information about the token by parsing the token itself, it can not
   likely offer an introspection service.

5.  Privacy Considerations

   The introspection response may contain privacy-sensitive information
   such as user identifiers for resource owners.  When this is the case,
   measures MUST be taken to prevent disclosure of this information to
   unintended parties.  One way to limit disclosure is to require
   authorization to call the introspection endpoint and to limit calls
   to only registered and trusted protected resource servers.  Another
   method is to transmit user identifiers as opaque service-specific
   strings, potentially returning different identifiers to each
   protected resource.  Omitting privacy-sensitive information from an
   introspection response is the simplest way of minimizing privacy
   issues.

6.  Acknowledgements

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

7.  References

7.1.  Normative References

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

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, March 2011.




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   [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.

   [RFC7009]  Lodderstedt, T., Dronia, S., and M. Scurtescu, "OAuth 2.0
              Token Revocation", RFC 7009, August 2013.

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

   [RFC7231]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Semantics and Content", RFC 7231, June 2014.

   [W3C.REC-html5-20141028]
              Hickson, I., Berjon, R., Faulkner, S., Leithead, T.,
              Navara, E., O'Connor, E., and S. Pfeiffer, "HTML5",
              World Wide Web Consortium Recommendation REC-
              html5-20141028, October 2014,
              <http://www.w3.org/TR/2014/REC-html5-20141028>.

7.2.  Informative References

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

   [TLS.BCP]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of TLS and DTLS", November
              2014.

Appendix A.  Document History

   [[ To be removed by the RFC Editor. ]]

   - 04

   o  Removed "resource_id" from request.

   o  Added examples.

   - 03

   o  Updated HTML and HTTP references.

   o  Call for registration of parameters in the JWT registry.




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   - 02

   o  Removed SAML pointer.

   o  Clarified what an "active" token could be.

   o  Explicitly declare introspection request as x-www-form-urlencoded
      format.

   o  Added extended example.

   o  Made protected resource authentication a MUST.

   - 01

   o  Fixed casing and consistent term usage.

   o  Incorporated working group comments.

   o  Clarified that authorization servers need to be able to understand
      the token if they're to introspect it.

   o  Various editorial cleanups.

   - 00

   o  Created initial IETF drafted based on draft-richer-oauth-
      introspection-06 with no normative changes.

Appendix B.  Use with Proof of Posession Tokens

   With bearer tokens such as those defined by OAuth 2.0 Bearer Token
   Usage [RFC6750], the protected resource will have in its possession
   the entire secret portion of the token for submission to the
   introspection service.  However, for proof-of-possession style
   tokens, the protected resource will have only a token identifier used
   during the request, along with the cryptographic signature on the
   request.  The protected resource would be able to submit the token
   identifier to the authorization server's token endpoint in order to
   obtain the necessary key information needed to validate the signature
   on the request.  The details of this usage are outside the scope of
   this specification and should be defined in an extension to this
   specification.








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Author's Address

   Justin Richer (editor)
   The MITRE Corporation

   Email: jricher@mitre.org













































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