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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                                              July 3, 2015
Intended status: Standards Track
Expires: January 4, 2016


                     OAuth 2.0 Token Introspection
                   draft-ietf-oauth-introspection-11

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 January 4, 2016.

Copyright Notice

   Copyright (c) 2015 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.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Introspection Endpoint  . . . . . . . . . . . . . . . . . . .   4
     2.1.  Introspection Request . . . . . . . . . . . . . . . . . .   4
     2.2.  Introspection Response  . . . . . . . . . . . . . . . . .   6
     2.3.  Error Response  . . . . . . . . . . . . . . . . . . . . .   8
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     3.1.  OAuth Token Introspection Response Registry . . . . . . .   9
       3.1.1.  Registration Template . . . . . . . . . . . . . . . .   9
       3.1.2.  Initial Registry Contents . . . . . . . . . . . . . .  10
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   5.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  14
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Appendix A.  Use with Proof of Posession Tokens . . . . . . . . .  15
   Appendix B.  Document History . . . . . . . . . . . . . . . . . .  16
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  17

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] does not define a protocol for the resource
   server to learn meta-information about a token that is has received
   from an authorization server, several different approaches have been
   developed to bridge this gap.  These include using structured token
   formats such as JWT [RFC7519] or proprietary inter-service
   communication mechanisms (such as shared databases and protected
   enterprise service buses) that convey token information.



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   This specification defines a protocol that allows authorized
   protected resources to query the authorization server to determine
   the set of metadata for a given token that was presented to 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 to make this
   authorization decision appropriately.

1.1.  Notational Conventions

   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 [RFC2119].

   Unless otherwise noted, all the protocol parameter names and values
   are case sensitive.

1.2.  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) [RFC7519].

   This specification defines the following terms:

   Token Introspection
      The act of inquiring about the current state of an OAuth 2.0 token
      through use of the network protocol defined in this document.

   Introspection Endpoint
      The OAuth 2.0 endpoint through which the token introspection
      operation is accomplished..



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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 dependent upon 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 valid
   for use at the protected resource making the introspection call.

   The introspection endpoint MUST be protected by a transport-layer
   security mechanism as described in Section 4.  The means by which the
   protected resource discovers the location of the introspection
   endpoint are outside the scope of this specification.

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
   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 MAY pass this
      parameter 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 the OAuth Token Type Hints
      registry defined in OAuth Token Revocation [RFC7009].

   The introspection endpoint MAY accept other OPTIONAL parameters to
   provide further context to the query.  For instance, an authorization
   server may desire to know the IP address of the client accessing the
   protected resource to determine if the correct client is likely to be
   presenting the token.  The definition of this or any other parameters



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   are outside the scope of this specification, to be defined by service
   documentation or extensions to this specification.  If the
   authorization server is unable to determine the state of the token
   without additional information, it SHOULD return an introspection
   response indicating the token is not active as described in
   Section 2.2.

   To prevent 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
   token.  The protected resource is using a separate OAuth 2.0 bearer
   token to authorize this call.

   Following is a non-normative example request:

     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:

     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







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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 specifics of a token's "active" state
      will vary depending on the implementation of the authorization
      server, and the information it keeps about its tokens, but a
      "true" value return for the "active" property will generally
      indicate that a given token has been issued by this authorization
      server, has not been revoked by the resource owner, and is within
      its given time window of validity (e.g. after its issuance time
      and before its expiration time).  See Section 4 for information on
      implementation of such checks.

   scope
      OPTIONAL.  A JSON string containing a space-separated list of
      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.

   username
      OPTIONAL.  Human-readable identifier for the resource owner who
      authorized this token.

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

   exp
      OPTIONAL.  Integer timestamp, measured in the number of seconds
      since January 1 1970 UTC, indicating when this token will expire,
      as defined in JWT [RFC7519].

   iat
      OPTIONAL.  Integer timestamp, measured in the number of seconds
      since January 1 1970 UTC, indicating when this token was
      originally issued, as defined in JWT [RFC7519].

   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, as defined in JWT [RFC7519].



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   sub
      OPTIONAL.  Subject of the token, as defined in JWT [RFC7519].
      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, as
      defined in JWT [RFC7519].

   iss
      OPTIONAL.  String representing the issuer of this token, as
      defined in JWT [RFC7519].

   jti
      OPTIONAL.  String identifier for the token, as defined in JWT
      [RFC7519].

   Specific implementations MAY extend this structure with their own
   service-specific response names as top-level members of this JSON
   object.  Response names intended to be used across domains MUST be
   registered in the OAuth Token Introspection Response registry defined
   in Section 3.1.

   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 are
   returned for each protected resource to prevent protected resources
   from learning more about the larger network than is necessary for its
   operation.

   The response MAY be cached by the protected resource to improve
   performance and reduce load on the introspection endpoint, but at the
   cost of liveness of the information used by the protected resource.
   See Section 4 for more information regarding the trade off when the
   response is cached.

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












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   Following is a non-normative example response:

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

     {
      "active": true,
      "client_id": "l238j323ds-23ij4",
      "username": "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 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
     }


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].





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   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

3.1.  OAuth Token Introspection Response Registry

   This specification establishes the OAuth Token Introspection Response
   registry.

   OAuth registration client metadata names and descriptions are
   registered with a Specification Required ([RFC5226]) after a two-week
   review period on the oauth-ext-review@ietf.org mailing list, on the
   advice of one or more Designated Experts.  However, to allow for the
   allocation of names prior to publication, the Designated Expert(s)
   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 Token
   Introspection Response name: example").

   Within the review period, the Designated Expert(s) will either
   approve or deny the registration request, communicating this decision
   to the review list and IANA.  Denials should include an explanation
   and, if applicable, suggestions as to how to make the request
   successful.

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

3.1.1.  Registration Template

   Name:
      The name requested (e.g., "example").  This name is case
      sensitive.  Names that match other registered names in a case



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      insensitive manner SHOULD NOT be accepted.  Names that match
      claims registered in the JSON Web Token Claims registry
      established by [RFC7519] SHOULD have comparable definitions and
      semantics.

   Description:
      Brief description of the metadata value (e.g., "Example
      description").

   Change controller:
      For Standards Track RFCs, state "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(s) that specify the token endpoint
      authorization method, preferably including a URI that can be used
      to retrieve a copy of the document(s).  An indication of the
      relevant sections may also be included but is not required.

3.1.2.  Initial Registry Contents

   The initial contents of the OAuth Token Introspection Response
   registry are:

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

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

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

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

   o  Name: "token_type"
   o  Description: Type of the token
   o  Change Controller: IESG



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

   o  Name: "exp"
   o  Description: Expiration timestamp of the token
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

   o  Name: "iat"
   o  Description: Issuance timestamp of the token
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

   o  Name: "nbf"
   o  Description: Timestamp which the token is not valid before
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

   o  Name: "sub"
   o  Description: Subject of the token
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

   o  Name: "aud"
   o  Description: Audience of the token
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

   o  Name: "iss"
   o  Description: Issuer of the token
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

   o  Name: "jti"
   o  Description: Unique identifier of the token
   o  Change Controller: IESG
   o  Specification Document(s): Section 2.2 of [[ this document ]].

4.  Security Considerations

   Since there are many different and valid ways to implement an OAuth
   2.0 system, there are consequently many ways for an authorization
   server to determine whether or not a token is currently "active" or
   not.  However, since resource servers using token introspection rely
   on the authorization server to determine the state of a token, the
   authorization server MUST perform all applicable checks against a
   token's state.  For instance:





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   o  If the token can expire, the authorization server MUST determine
      whether or not the token has expired.
   o  If the token can be issued before it is able to be used, the
      authorization server MUST determine whether or not a token's valid
      period has started yet.
   o  If the token can be revoked after it was issued, the authorization
      server MUST determine whether or not such a revocation has taken
      place.
   o  If the token has been signed, the authorization server MUST
      validate the signature.
   o  If the token can be used only at certain resource servers, the
      authorization server MUST determine whether or not the token can
      be used at the resource server making the introspection call.

   If an authorization server fails to perform any applicable check, the
   resource server could make an erroneous security decision based on
   that response.  Note that not all of these checks will be applicable
   to all OAuth 2.0 deployments and it is up to the authorization server
   to determine which of these checks (and any other checks) apply.

   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 and responds with information used to make authorization
   decisions, 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, as specified in RFC 6125
   [RFC6125].  Implementation security considerations can be found in
   Recommendations for Secure Use of TLS and DTLS [TLS.BCP].





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   To prevent the values of access tokens from leaking into server-side
   logs via query parameters, an authorization server offering token
   introspection MAY disallow the use of HTTP GET on the introspection
   endpoint and instead require the HTTP POST method to be used at the
   introspection endpoint.

   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").

   Since a protected resource MAY cache the response of the
   introspection endpoint, designers of an OAuth 2.0 system using this
   protocol MUST consider the performance and security trade-offs
   inherent in caching security information such as this.  A less
   aggressive cache with a short timeout will provide the protected
   resource with more up to date information (due to it needing to query
   the introspection endpoint more often) at the cost of increased
   network traffic and load on the introspection endpoint.  A more
   aggressive cache with a longer duration will minimize network traffic
   and load on the introspection endpoint, but at the risk of stale
   information about the token.  For example, the token may be revoked
   while the protected resource is relying on the value of the cached
   response to make authorization decisions.  This creates a window
   during which a revoked token could be used at the protected resource.
   Consequently, an acceptable cache validity duration needs to be
   carefully considered given the concerns and sensitivities of the
   protected resource being accessed and the likelihood of a token being
   revoked or invalidated in the interim period.  Highly sensitive
   environments can opt to disable caching entirely on the protected
   resource to eliminate the risk of stale cached information entirely,
   again at the cost of increased network traffic and server load.  If
   the response contains the "exp" parameter (expiration), the response
   MUST NOT be cached beyond the time indicated therein.

   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
   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 to access this information.  Also note



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   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 method is to transmit user identifiers as
   opaque service-specific strings, potentially returning different
   identifiers to each protected resource.

   If the protected resource sends additional information about the
   client's request to the authorization server (such as the client's IP
   address) using an extension of this specification, such information
   could have additional privacy considerations that the extension
   should detail.  However, the nature and implications of such
   extensions are outside the scope of this specification.

   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 User Managed Access Working
   Group for feedback and review of this document, and to the various
   implementors of both the client and server components of this
   specification.  In particular, the author would like to thank Amanda
   Anganes, John Bradley, Thomas Broyer, Brian Campbell, George
   Fletcher, Paul Freemantle, Thomas Hardjono, Eve Maler, Josh Mandel,
   Steve Moore, Mike Schwartz, Prabath Siriwardena, Sarah Squire, and
   Hannes Tschofennig.

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.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

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



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   [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.

   [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.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, May 2015.

   [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

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

Appendix A.  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 to obtain the
   necessary key information needed to validate the signature on the



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   request.  The details of this usage are outside the scope of this
   specification and will be defined in an extension to this
   specification.

Appendix B.  Document History

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

   -11

   o  Minor wording tweaks from IESG review.

   -10

   o  Added missing 2119 section to terminology.
   o  Removed optional HTTP GET at introspection endpoint.
   o  Added terminology.
   o  Renamed this "a protocol" instead of "web API".
   o  Moved JWT to normative reference.
   o  Reworded definition of "scope" value.
   o  Clarified extensibility of input parameters.
   o  Noted that discover is out of scope.
   o  Fixed several typos and imprecise references.

   -09

   o  Updated JOSE, JWT, and OAuth Assertion draft references to final
      RFC numbers.

   -08

   o  Added privacy considerations note about extensions.
   o  Added acknowledgements (finally).

   -07

   o  Created a separate IANA registry for introspection responses,
      importing the values from JWT.

   -06

   o  Clarified relationship between AS and RS in introduction.
   o  Used updated TLS text imported from Dyn-Reg drafts.
   o  Clarified definition of active state.
   o  Added some advice on caching responses.
   o  Added security considerations on active state implementation.
   o  Changed user_id to username based on WG feedback.




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   -05

   o  Typo fix.
   o  Updated author information.
   o  Removed extraneous "linewrap" note from examples.

   - 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.

   - 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.

Author's Address

   Justin Richer (editor)

   Email: ietf@justin.richer.org








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