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Versions: 00 draft-ietf-stir-rph

STIR                                                          Ray. Singh
Internet-Draft                                              Vencore Labs
Intended status: Standards Track                           Martin. Dolly
Expires: December 8, 2017                                           AT&T
                                                              Subir. Das
                                                            Vencore Labs
                                                              An. Nguyen
                                   Office of Emergency Communication/DHS
                                                           June 06, 2017


         PASSporT Extension for Resource-Priority Authorization
                        draft-singh-stir-rph-00

Abstract

   This document extends the PASSporT object to convey
   cryptographically-signed assertions of authorization for
   communications 'Resource-Priority'.  It extends PASSporT to allow
   cryptographic-signing of the SIP 'Resource-Priority" header field
   which is used for communications resource prioritization.  It also
   describes how the PASSPorT extension is used in SIP signaling to
   convey assertions of authorization of the information in the SIP
   'Resource-Priority' header field.

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 December 8, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  PASSporT 'rph' Claim  . . . . . . . . . . . . . . . . . . . .   3
   4.  'rph' in SIP  . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Authentication Service Behavior . . . . . . . . . . . . .   4
     4.2.  Verification Service Behavior . . . . . . . . . . . . . .   5
   5.  Further Information Associated with Resource-Priority . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  JSON Web Token Claims Registration  . . . . . . . . . . .   6
     6.2.  PASSporT RPH Types  . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
     7.1.  Avoidance of replay and cut and past attacks  . . . . . .   7
     7.2.  Solution Considerations . . . . . . . . . . . . . . . . .   7
     7.3.  Acknowledgements  . . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   PASSporT [I-D.ietf-stir-passport] is a token format based on JWT
   [RFC7519] for conveying cryptographically-signed information about
   the identities involved in personal communications; it is used with
   STIR [I-D.ietf-stir-rfc4474bis] to convey a signed assertion of the
   identity of the participants in real-time communications established
   via a protocol like SIP.  This specification extends PASSporT to
   allow cryptographic-signing of the SIP 'Resource-Priority' header
   field defined in [RFC4412].

   [RFC4412] defines the SIP 'Resource-Priority' header field for
   communications Resource Priority.  As specified in [RFC4412], the
   'Resource-Priority' header field may be used by SIP user agents,
   including, Public Switched Telephone Network (PSTN) gateways and
   terminals, and SIP proxy servers to influence prioritization afforded
   to communication sessions,including PSTN calls.  However, the SIP



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   'Resource-Priority' header field could be spoofed and abused by
   unauthorized entities.

   The STIR architecture assumes that an authority on the originating
   side of a call provides a cryptographic assurance of the validity of
   the calling party number in order to prevent impersonation attacks.
   The STIR architecture allows extension that can be utilized by
   authorities supporting real-time communication services using the
   'Resource-Priority' header field to cryptographically sign the SIP
   'Resource-Priority' header field and convey assertion of the
   authorization for 'Resource-Priority'.  For example, the authority on
   the originating side verifying the authorization of a particular
   communication for Resource-Priority can use a PASSPorT claim to
   cryptographically-sign the SIP 'Resource-Priority' header field and
   convey an assertion of the authorization for 'Resource-Priority'.
   This will allow a receiving entity (including entities located in
   different network domains/boundaries) to verify the validity of
   assertions authorizating Resource-Priority.  Cryphographically-signed
   SIP 'Resource-Priority' headers will allow a receiving entity to
   verify and act on the information with confidence that the
   information have not been spoofed or compromised.

   This specification documents an optional extension to PASSporT and
   the associated STIR mechanisms to provide a function to sign the SIP
   'Resource-Priority' header field.  How the optional extension to
   PASSporT is used for real-time communications supported using SIP
   'Resource-Priority' header field is defined in other documents and is
   outside the scope of this document.

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 RFC 2119 [RFC2119].

3.  PASSporT 'rph' Claim

   This specification defines a new JSON Web Token claim for "rph",
   which provides an assertion for information in SIP 'Resource-
   Priority'header.

   The creator of a PASSporT object adds a "ppt" value of "rph" to the
   header of a PASSporT object, in which case the PASSporT claims MUST
   contain a "rph" claim, and any entities verifying the PASSporT object
   will be required to understand the "ppt" extension in order to
   process the PASSporT in question.  A PASSPort header with the "ppt"
   included will look as follows:




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   {  "typ":"passport",
     "ppt":"rph",
     "alg":"ES256",
     "x5u":"https://www.example.org/cert.cer"}

   The "rph" claim will provide an assertion of authorization,"auth",
   for information in the SIP "Resource-Priority" header field (i.e.,
   Resource-Priority: namespace "." r-priority) based on [RFC4412].  The
   value of the "rph" claim is an array containing one or more of JSON
   objects for the content of the SIP 'Resource-Priority' header that is
   being asserted of which one of the "rph" object, is mandatory.

   The following is an example "rph" claim for a SIP "Resource-Priority"
   header field with a "namespace "." r-priority" value of "ets.0".

    { "orig":{"tn":"12155551212"}
     "dest":{"tn":"12125551213"},
     "iat":1443208345,
     "rph":{"auth":":"Resource-Priority: ets.0"}}

   After the header and claims PASSporT objects have been constructed,
   their signature is generated normally per the guidance in
   [I-D.ietf-stir-passport] using the full form of PASSPorT.  The
   credentials (e.g., authority responsible for authorizating Resource-
   Priority) used to create the signature must have authority over the
   "rph" claim.

4.  'rph' in SIP

   This section specifies SIP-specific usage for the "rph" claim in
   PASSporT.

4.1.  Authentication Service Behavior

   The Authentication Service will create the "rph" claim using the
   values discussed in section 3 based on [RFC4412].  The constrcution
   of "rph" claim follows the steps described in Section 4 of
   [I-D.ietf-stir-rfc4474bis].

   The resulting Identity header for "rph" might look as follows:











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"eyJhbGciOiJFUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJleUowZVhBaU9pSndZWE56Y0c5eW
RDSXNEUW9pY0hCMElqb2ljbkJvSWl3TkNpSmhiR2NpT2lKRlV6STFOaUlzRFFvaWVEVjFJanBvZE
hSd2N6b3ZMM2QzZHk1bGVHRnRjR3hsTG1OdmJTOWpaWEowTG1ObGNuME5DZz09LmV5SnZjbWxuSW
pwN0luUnVJam9pTVRJeE5UVTFOVEV5TVRJaWZTd2dEUW9pYVdGMElqb2lNVFEwTXpJd09ETTBOU0
lzSUEwS0ltUmxjM1FpT25zaWRHNGlPaUl4TWpFMU5UVTFNVEl4TXlKOURRb2ljbkJvSWpwN0ltRj
FkR2dpT2lKU1pYTnZkWEpqWlMxUWNtbHZjbWwwZVRvZ1pYUnpMakFpWFgxOURRb05DZzBLIiwibm
JmIjoxNDk2NzU4Mzk0LCJleHAiOjE0OTY3NjE5OTQsImlhdCI6MTQ5Njc1ODM5NH0.0-oNMVgchp
biDzSxCktUIQVbkJWL48DfxOTllSHBmj3sZtV2S3SKZkmnU2V9akv2LnJ50JK9W_1ynz7JrChJ3g";
info= "https://www.example.org/cert.cer";alg=ES256;ppt="rph"

   A SIP authentication service typically will derive the value of "rph"
   from the 'Resource-Priority' header field based on policy associated
   with service specific use of the "namespace "." r-priority" values
   based on [RFC4412].  The authentication service derives the value of
   the PASSPorT claim by verifying the authorization for Resource-
   Priority (i.e., verifying a calling user privilege for Resoure-
   Priority based on its identity) which mighth be derived from customer
   profile data or from access to external services.

   [RFC4412] allows multiple "namespace "." r-priority" pairs, either in
   a single SIP Resource-Priority header or across multiple SIP
   Resource-Priority headers.  However, it is not necessary to sign all
   content of a SIP Resource-Priority header or all SIP Resource-
   Priority headers in a given SIP message.  An authority is only
   responsible for signing the content of a SIP Resource-Priority header
   for which it has authority (e.g., a specific "namespace "."
   r-priority").

4.2.  Verification Service Behavior

   [I-D.ietf-stir-rfc4474bis] Section 6.2 Step 5 requires that
   specifications defining "ppt" values describe any additional verifier
   behavior.  The behavior specified for the "ppt" values of "rph" is as
   follows:

   The verification service MUST extract the value associated with the
   "auth" key in a full form PASSPorT with a "ppt" value of "rph".  If
   the signature validates, then the verification service can use the
   value of the "rph" claim as validation that the calling party is
   authorized for Resource-Priority, which would in turn be used for
   priority treatment in accordance with local policy for the associated
   communication service.

   The verification service MUST extract the value associated with the
   "auth" key in a full form PASSPorT with a "ppt" value of "rph".  If
   the signature validates, then the verification service can use the
   value of the "rph" claim as validation that the calling party is
   authorized for Resource-Priority, which would in turn be used for



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   priority treatment in accordance with local policy for the associated
   communication service.

   In addition, [I-D.ietf-stir-rfc4474bis] Section 6.2 Step 4 requires
   "iat" value in "rph" claim to be verified.

   The behavior of a SIP UAs upon receiving an INVITE containing a
   PASSporT object with a "rph" claim will largely remain a matter of
   implementation policy for the specific communication service.  In
   most cases,implementations would act based on confidence in the
   veracity of this information.

5.  Further Information Associated with Resource-Priority

   There may be additional information about the calling party or the
   call that could be relevant to authorization for Resource-Priority.
   This may include information related to the device subscription of
   the caller, or to any institutions that the caller or device is
   associated with, or even categories of institutions.  All of these
   data elements would benefit from the secure attestations provided by
   the STIR and PASSporT frameworks.  The specification of the "rph"
   claim could entail the optional presence of one or more such
   additional information fields.

   A new IANA registry has been defined to hold potential values of the
   "rph" array; see Section 8.3.  Details of extensions to the "rph"
   claim to encompass other data elements are left for future version of
   this specification.

6.  IANA Considerations

6.1.  JSON Web Token Claims Registration

   o  Claim Name: "rph"

   o  Claim Description: Resource Priority Header

   o  Change Controller: IESG

   o  Specification Document(s): Section 3 of [RFCThis]

6.2.  PASSporT RPH Types

   This document requests that the IANA create a new registry for
   PASSporT RPH types.  Registration of new PASSporT RPH types shall be
   under the specification required policy.





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   This registry is to be initially populated with a single value for
   "namespace" which is specified in [RFCThis].

7.  Security Considerations

   The security considerations discussed in [I-D.ietf-stir-rfc4474bis]
   in Section 10 are applicable here.

7.1.  Avoidance of replay and cut and past attacks

   The PASSporT extension with a "ppt" value of "rph" MUST only be sent
   with SIP when 'Resource-Priority' header is used to convey the
   priority of the communication as defined in [RFC4412].  A uniqueness
   of the set of token with extension claims and token signature is
   constructed using the originating identity being asserted with the
   "orig" claim along with the following two claims:

   o  "iat" claim should correspond to a date/time the message was
      originated.  It should also be within a relative time that is
      reasonable for clock drift and transmission time characteristics
      associated with the application using the PASSporT token.
      Therefore, validation of the token should consider date and time
      correlation, which could be influenced by signaling protocol
      specific use and network time differences.

   o  "dest" claim is included to prevent the valid re-use of a
      previously originated message to send to another destination
      party.

7.2.  Solution Considerations

   The use of extension to PASSporT tokens with ppt value rph based on
   the validation of the digital signature and the associated
   certificate requires consideration of the authentication and
   authority or reputation of the signer to attest to the identity being
   asserted.  The following considerations should be recognized when
   using PASSporT extension with "ppt" value of "rph":

   o  The use of this token should not, in it's own right, be considered
      a full solution for absolute non-repudiation of the identity being
      asserted.

   o  An authority (signer) is only allowed to sign the content of a SIP
      'Resource-Priority' header for which it has the right authority.
      The authority that signs the token MUST have a secure method for
      authentication of the end user or the device.





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   o  The verification of the signature MUST include means of verifying
      that the signer is authoritative for the signed content of the SIP
      'Resource-Priority' header.

7.3.  Acknowledgements

   We would like to thank STIR members, ATIS/SIP Forum Task Force on
   IPNNI members, and the NS/EP Priority Services community for
   contributions to this problem statement and specification.  We would
   also like to thank David Hancock for his valuable inputs.

8.  References

8.1.  Normative References

   [I-D.ietf-stir-passport]
              Wendt, C. and J. Peterson, "Personal Assertion Token
              (PASSporT)", February 2017.

   [I-D.ietf-stir-rfc4474bis]
              Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
              "Authenticated Identity Management in the Session
              Initiation Protocol (SIP)", February 2017.

   [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>.

   [RFC4412]  Schulzrinne, H. and J. Polk, "Communications Resource
              Priority for the Session Initiation Protocol (SIP)",
              RFC 4412, DOI 10.17487/RFC4412, February 2006,
              <http://www.rfc-editor.org/info/rfc4412>.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <http://www.rfc-editor.org/info/rfc7519>.

8.2.  Informative References

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <http://www.rfc-editor.org/info/rfc3261>.






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   [RFC6919]  Barnes, R., Kent, S., and E. Rescorla, "Further Key Words
              for Use in RFCs to Indicate Requirement Levels", RFC 6919,
              DOI 10.17487/RFC6919, April 2013,
              <http://www.rfc-editor.org/info/rfc6919>.

   [RFC7340]  Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure
              Telephone Identity Problem Statement and Requirements",
              RFC 7340, DOI 10.17487/RFC7340, September 2014,
              <http://www.rfc-editor.org/info/rfc7340>.

Authors' Addresses

   Ray P. Singh
   Vencore Labs
   150 Mount Airy Road
   New Jersey, NJ  07920
   USA

   Email: rsingh@vencorelabs.com


   Martin Dolly
   AT&T
   200 Laurel Avenue
   Middletown, NJ 07748
   USA

   Email: md3135@att.com


   Subir Das
   Vencore Labs
   150 Mount Airy Road
   New Jersey, NJ  07920
   USA

   Email: sdas@vencorelabs.com


   An Nguyen
   Office of Emergency Communication/DHS
   245 Murray Lane, Building 410
   Washington, DC 20528
   USA

   Email: an.p.nguyen@HQ.DHS.GOV





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