Metadata discovery for third party authorized TURN session
draft-reddy-tram-token-metadata-00

TRAM                                                            T. Reddy
Internet-Draft                                             S. Nandakumar
Intended status: Standards Track                                 D. Wing
Expires: February 29, 2016                                         Cisco
                                                             B. Williams
                                                            Akamai, Inc.
                                                         August 28, 2015

       Metadata discovery for third party authorized TURN session
                   draft-reddy-tram-token-metadata-00

Abstract

   The operator of the TURN server might want to have fine grained
   control on the clients usage of the server resources for providing
   features such as limiting the bandwith usage, number of allocations
   and so on.  This document proposes a generic mechanism for the
   operator to introspect the access token to retrieve any policy
   restrictions imposed by the authorization server on the TURN server
   resources assigned to the client.

Status of This Memo

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   This Internet-Draft will expire on February 29, 2016.

Copyright Notice

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   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Introspection Request . . . . . . . . . . . . . . . . . . . .   3
   4.  Introspection Response  . . . . . . . . . . . . . . . . . . .   4
   5.  INTROSPECTION_ENDPOINT Attribute  . . . . . . . . . . . . . .   5
   6.  Notifications from Introspection Endpoint . . . . . . . . . .   5
   7.  Alternate approach  . . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  JSON Web Token Claims . . . . . . . . . . . . . . . . . .   6
     9.2.  Well-Known 'introspection' URI  . . . . . . . . . . . . .   7
     9.3.  STUN attribute  . . . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     11.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The TURN protocol [RFC5766] is used to setup a relay service (via a
   TURN Server) to exchange traffic (real time media, data) between
   peers when direct peer-to-peer connection is not otherwise possible.
   Due to the costs associated with operating a relay service, it is
   important to constrain resource usage.  For example, the operator
   might want to limit the number of allocations or bandwidth.

   [I-D.ietf-tram-turn-third-party-authz] allows clients to obtain
   OAuth2.0 access token (of type 'Assertion') authorized by a
   Authorization Server to access a given TURN server.  On receiving
   such a token, the TURN server validates the token to grant or reject
   access to the session resources.  However, having a token doesn't
   provide any control for the operator of the TURN server restrict the
   server's resources.  This specification proposes using the mechanism
   defined in [I-D.ietf-oauth-introspection] to query OAuth2.0
   authorization server to determine resource restrictions for this
   token.

   The rest of the document is organized as follows.  Section 3 provides
   procedure for querying the OAuth2.0 introspection endpoint and

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   Section 4 shows the introspection response with the parameters
   identifying the policy controls associated with the access token.

2.  Terminology

   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].

   This document defines the following terms:

   Access Token: OAuth 2.0 access token.

   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.  The Introspection
   Endpoint could be a WebRTC server.

3.  Introspection Request

   For introspecting the meta-information associated with the access
   token, the TURN server shall execute the procedures defined in
   Section 2.1 of [I-D.ietf-oauth-introspection].

     POST {scheme}://{host}:{port}/.well-known/introspection
     Accept: application/json
     Content-Type: application/x-www-form-urlencoded

     {
         "token" : "string"
         "token_type_hint" : "string"
     }

        token REQUIRED.  This parameter is defined in
        [I-D.ietf-oauth-introspection].  The access token is conveyed by
        the TURN client to the TURN server as discussed in Section 3.1
        of [I-D.ietf-tram-turn-third-party-authz].

        token_type_hint OPTIONAL.  This parameter is defined in
        [I-D.ietf-oauth-introspection].  The token type MUST be set to
        'access_token' defined in [RFC7009].  If the token type is not
        'access_token', the server rejects the request with a 400 (Bad
        Request) error.

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   Following is a non-normative example request showcasing the
   introspection request for a given access token.

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

     {

        "token" : "2YotnFZFEjr1zCsicMWpAA"
        "token_type_hint" : "access_token"

     }

4.  Introspection Response

   The OAuth2.0 Introspection Endpoint on recognizing the token,
   responds with a JSON object [RFC7159] in "application/json" format
   with the following members.

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

     {
     "active" : "boolean",
     "scope" : "string",
     "max_upstream_bandwidth" : "unsigned integer",
     "max_downstream_bandwidth" : "unsigned integer",
     "max_allocations" : "unsigned integer",
     "lifetime" : "unsigned integer",
     }

        active REQUIRED.  This parameter is defined in
        [I-D.ietf-oauth-introspection].

        scope OPTIONAL.  This parameter is defined in
        [I-D.ietf-oauth-introspection].  For this specification, the
        scope MUST be 'stun'.

        max_upstream_bandwidth REQUIRED.  The value of this parameter is
        an 64 bit unsigned integer that represents the maximum upstream
        bandwidth permitted for the token in kilobits per second (1
        kilobit = 1024 bits).

        max_downstream bandwidth REQUIRED.  The value of this parameter
        is an 64 bit unsigned integer that represents the maximum

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        downstream bandwidth permitted for the token in kilobits per
        second (1 kilobit = 1024 bits).

        max_allocations: REQUIRED. 16 bit unsigned integer defining
        maximum number of allocations that is allowable for the given
        access token.

        lifetime: REQUIRED: The lifetime of the access token, in
        seconds.

   NOTE: Future specifications are allowed to define further top-level
   members as mandated by the use-cases.

   Following is a non-normative example response:

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

     {
     "active" : true,
     "scope" : "stun",
     "upstream-bandwidth" : 4096,
     "downstream-bandwidth" : 4096,
     "max-allocations" : 1,
     }

5.  INTROSPECTION_ENDPOINT Attribute

   This attribute is used by the TURN client to inform the TURN server
   the FQDN of Introspection Endpoint.

   The TURN server establishes an HTTPS connection with the indicated
   server and sends the above-described communications to that server.
   The INTROSPECTION_ENDPOINT attribute is a comprehension-optional
   attribute (see Section 15 from [RFC5389]).

   TBD: An alternate approach is to convey the FQDN in the token itself.

6.  Notifications from Introspection Endpoint

   Introspection Endpoint can send unsolicited responses to notify
   updates to the metadata associated with the token to the TURN server
   using HTTP/2 server push mechanism.  Examples where such
   notifications are desired are:

   o  The Introspection Endpoint can signal the TURN server to revoke
      the access token after the call is terminated by setting lifetime
      to zero.

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   o  When the call switches from audio to video, the Introspection
      Endpoint notifies the increased bandwidth to the TURN server.

7.  Alternate approach

   TBD:

   Another approach, not discussed in this document, is a self-
   contained token where the metadata is contained within the token
   itself.  This approach has the benefit of avoiding a protocol between
   the TURN server and the Introspection Endpoint.  However, this
   approach has the following drawbacks:

   o  Needs a large TURN packet to accommodate the token.

   o  Token needs versioning for future enhancements, and the
      Introspection Endpoint needs a mechanism to learn the token
      version supported by the TURN server.

   o  Introspection Endpoint cannot notify changes to the metadata
      associated with the token to the TURN server.

8.  Security Considerations

   The Security Considerations and Privacy Considerations of
   [I-D.ietf-oauth-introspection] apply to this document.

9.  IANA Considerations

9.1.  JSON Web Token Claims

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

   o  Claim Name: "max_upstream_bandwidth"
   o  Claim Description: Maximum limit of upstream bandwidth
   o  Change Controller: IESG
   o  Specification Document(s): Section 4 of [[ this document ]].

   o  Claim Name: "max_downstream_bandwidth"
   o  Claim Description: Maximum limit of downstream bandwidth
   o  Change Controller: IESG
   o  Specification Document(s): Section 4 of [[ this document ]].

   o  Claim Name: "max_allocations"
   o  Claim Description: Maximum number of allocations
   o  Change Controller: IESG
   o  Specification Document(s): Section 4 of [[ this document ]].

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9.2.  Well-Known 'introspection' URI

   This memo registers the 'introspection' well-known URI in the Well-
   Known URIs registry as defined by [RFC5785].

   URI suffix: introspection

   Change controller: IETF

   Specification document(s): This document

   Related information: None

9.3.  STUN attribute

   [Paragraphs below in braces should be removed by the RFC Editor upon
   publication]

   [IANA is requested to add the following attributes to the STUN
   attribute registry [iana-stun], the INTROSPECTION_ENDPOINT attribute
   requires that IANA allocate a value in the "STUN attributes Registry"
   from the comprehension-optional range (0x8000-0xBFFF)].

   This document defines the INTROSPECTION_ENDPOINT attribute, described
   in Section 5.  IANA has allocated the comprehension-optional
   codepoint TBD for this attribute.

10.  Acknowledgements

   TODO

11.  References

11.1.  Normative References

   [I-D.ietf-oauth-introspection]
              Richer, J., "OAuth 2.0 Token Introspection", draft-ietf-
              oauth-introspection-11 (work in progress), July 2015.

   [I-D.ietf-tram-turn-third-party-authz]
              Reddy, T., Patil, P., R, R., and J. Uberti, "Session
              Traversal Utilities for NAT (STUN) Extension for Third
              Party Authorization", draft-ietf-tram-turn-third-party-
              authz-16 (work in progress), May 2015.

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   [iana-stun]
              IANA, , "IANA: STUN Attributes", April 2011,
              <http://www.iana.org/assignments/stun-parameters/stun-pa
              rameters.xml>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC5389]  Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
              "Session Traversal Utilities for NAT (STUN)", RFC 5389,
              DOI 10.17487/RFC5389, October 2008,
              <http://www.rfc-editor.org/info/rfc5389>.

   [RFC5766]  Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
              Relays around NAT (TURN): Relay Extensions to Session
              Traversal Utilities for NAT (STUN)", RFC 5766,
              DOI 10.17487/RFC5766, April 2010,
              <http://www.rfc-editor.org/info/rfc5766>.

11.2.  Informative References

   [RFC5785]  Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
              Uniform Resource Identifiers (URIs)", RFC 5785,
              DOI 10.17487/RFC5785, April 2010,
              <http://www.rfc-editor.org/info/rfc5785>.

   [RFC7009]  Lodderstedt, T., Ed., Dronia, S., and M. Scurtescu, "OAuth
              2.0 Token Revocation", RFC 7009, DOI 10.17487/RFC7009,
              August 2013, <http://www.rfc-editor.org/info/rfc7009>.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <http://www.rfc-editor.org/info/rfc7159>.

Authors' Addresses

   Tirumaleswar Reddy
   Cisco Systems, Inc.

   Email: tireddy@cisco.com

   Suhas Nandakumar
   Cisco Systems, Inc.

   Email: snandaku@cisco.com

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   Dan Wing
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, California  95134
   USA

   Email: dwing@cisco.com

   Brandon Williams
   Akamai, Inc.
   8 Cambridge Center
   Cambridge, MA  02142
   USA

   Email: brandon.williams@akamai.com

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