draft-richer-oauth-introspection.xml

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<rfc category="std" docName="draft-richer-oauth-introspection-04"
     ipr="trust200902">
  <front>
    <title abbrev="oauth-introspection">OAuth Token Introspection</title>

    <author fullname="Justin Richer" initials="J." role="editor"
            surname="Richer">
      <organization>The MITRE Corporation</organization>

      <address>
        <email>jricher@mitre.org</email>
      </address>
    </author>

    <date day="1" month="May" year="2013"/>

    <area>Security</area>

    <workgroup>OAuth Working Group</workgroup>

    <abstract>
      <t>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.</t>
    </abstract>

    <note title="Requirements Language">
      <t>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 <xref
      target="RFC2119">RFC 2119</xref>.</t>
    </note>
  </front>

  <middle>
    <section anchor="introduction" title="Introduction">
      <t>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.</t>

      <t>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.</t>
    </section>

    <section title="Introspection Endpoint">
      <t hangText="instance_name">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.</t>

      <t hangText="instance_name">The endpoint MUST be protected by TLS or
      equivalent.</t>

      <section title="Introspection Request">
        <t hangText="instance_name"><list style="hanging">
            <t hangText="token">REQUIRED. The string value of the token.</t>

            <t hangText="resource_id">OPTIONAL. A service-specific string
            identifying the resource that the client doing the introspection
            is asking about.</t>

            <t hangText="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 <xref
            target="Revocation">OAuth Token Revocation</xref>.</t>
          </list></t>

        <t hangText="instance_name">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.</t>

        <t hangText="instance_name">The endpoint SHOULD also require some form
        of authentication to access this endpoint, such as the Client
        Authentication as described in <xref target="RFC6749">OAuth 2 Core
        Specification</xref> or a separate OAuth 2.0 Access Token. The methods
        of managing and validating these authentication credentials are out of
        scope of this specification.</t>
      </section>

      <section title="Introspection Response">
        <t>The server responds with a <xref target="RFC4627">JSON
        object</xref> in <spanx style="verb">application/json</spanx> format
        with the following top-level members. Specific implementations MAY
        extend this structure with their own service-specific pieces of
        information.</t>

        <t><list style="hanging">
            <t hangText="active">REQUIRED. Boolean indicator of whether or not
            the presented token is currently active.</t>

            <t hangText="exp">OPTIONAL. Integer timestamp, measured in the
            number of seconds since January 1 1970 UTC, indicating when this
            token will expire.</t>

            <t hangText="iat">OPTIONAL. Integer timestamp, measured in the
            number of seconds since January 1 1970 UTC, indicating when this
            token was originally issued.</t>

            <t hangText="scope">OPTIONAL. A space-separated list of strings
            representing the scopes associated with this token, in the format
            described in Section 3.3 of <xref target="RFC6749">OAuth
            2.0</xref>.</t>

            <t hangText="client_id">OPTIONAL. Client Identifier for the OAuth
            Client that requested this token.</t>

            <t hangText="sub">OPTIONAL. Local identifier of the Resource Owner
            who authorized this token.</t>

            <t hangText="aud">OPTIONAL. Service-specific string identifier or
            list of string identifiers representing the intended audience for
            this token.</t>

            <t hangText="token_type">OPTIONAL. Type of the token as defined in
            OAuth 2.0 section 5.1.</t>
          </list></t>
      </section>

      <section title="Non-normative Example">
        <t hangText="instance_name">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 <xref
        target="RFC6749">OAuth2</xref> Section 2.3.1.</t>

        <figure>
          <preamble>Following is a non-normative example request (with line
          wraps for display purposes only):</preamble>

          <artwork><![CDATA[POST /register HTTP/1.1
Accept: application/x-www-form-urlencoded
Host: server.example.com
Authorization: Basic czZCaGRSa3F0Mzo3RmpmcDBaQnIxS3REUmJuZlZkbUl3

token=X3241Affw.4233-99JXJ
]]></artwork>
        </figure>

        <t>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.</t>

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

          <artwork><![CDATA[HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store

{
 "active": true,
 "client_id":"s6BhdRkqt3",
 "scope": "read write dolphin",
 "sub": "2309fj32kl",
 "aud": "http://example.org/protected-resource/*"
}]]></artwork>
        </figure>

        <t/>

        <t>If the token presented is not currently active (but the
        authentication presented is valid), it returns the following JSON
        document.</t>

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

          <artwork><![CDATA[HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store

{
 "active": false
}]]></artwork>
        </figure>

        <t/>

        <t>If the client credentials are invalid or there is another error,
        the Authorization Server responds with an HTTP 400 (Bad Request) as
        described in <xref target="RFC6749">OAuth 2.0 section 5.2</xref>.</t>
      </section>
    </section>

    <section anchor="IANA" title="IANA Considerations">
      <t>This document makes no request of IANA.</t>
    </section>

    <section anchor="Security" title="Security Considerations">
      <t>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 they may be
      exchanged for an OAuth2 Access token scoped specifically for the
      Introspection Endpoint.</t>

      <t>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.</t>
    </section>

    <section title="Acknowledgements">
      <t>Thanks to the OAuth Working Group and the UMA Working Group for
      feedback.</t>
    </section>
  </middle>

  <back>
    <references title="Normative References">
      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.6749.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.6750.xml'?>

      <?rfc include='http://xml.resource.org/public/rfc/bibxml/reference.RFC.4627.xml'?>

      <reference anchor="Revocation">
        <front>
          <title>OAuth Token Revocation</title>

          <author fullname="Torsten Lodderstedt" initials="T."
                  surname="Lodderstedt">
            <organization>Deutsche Telekom AG</organization>
          </author>

          <date day="15" month="April" year="2013"/>
        </front>
      </reference>
    </references>
  </back>
</rfc>