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Versions: (draft-dolly-stir-rph-emergency-services) 00 01 02

STIR                                                            M. Dolly
Internet-Draft                                                      AT&T
Intended status: Standards Track                                C. Wendt
Expires: January 14, 2021                                        Comcast
                                                           July 13, 2020


Assertion Values for a Resource Priority Header Claim and a SIP Priority
         Header Claim in Support of Emergency Services Networks
               draft-ietf-stir-rph-emergency-services-02

Abstract

   This document adds new assertion values for a Resource Priority
   Header ("rph") claim and a new SIP Priority Header claim ("sph") for
   protection of the "psap-callback" value as part of the "rph" PASSporT
   extension, in support of the security of Emergency Services Networks
   for emergency call origination and callback.

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 January 14, 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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.  New Assertion Values for "rph" claim  . . . . . . . . . . . .   3
     3.1.  ESorig  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  EScallback  . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  The SIP Priority header "sph" claim . . . . . . . . . . . . .   4
   5.  Order of Claim Keys . . . . . . . . . . . . . . . . . . . . .   5
   6.  Compact Form of PASSporT  . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  PASSporT Resource Priority Header (rph) Types . . . . . .   5
     7.2.  JSON Web Token claims . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Personal Assertion Token (PASSporT) Extension for Resource Priority
   Authorization [RFC8443] extended the Personal Assertion Token
   (PASSporT) specification defined in [RFC8225] to allow the inclusion
   of cryptographically signed assertions of authorization for the
   values populated in the Session Initiation Protocol (SIP) "Resource-
   Priority" header field [RFC4412], which is used for communications
   resource prioritization and the SIP "Priority" header field, used for
   categorizing the priority use of the call.

   Compromise of the SIP "Resource-Priority" header field could lead to
   misuse of network resources (i.e., during congestion scenarios),
   impacting the application services supported using the SIP "Resource-
   Priority" header field.

   [RFC8225] allows extensions by which an authority on the originating
   side verifying the authorization of a particular communication for
   the SIP "Resource-Priority" header field or the SIP "Priority" header
   field can use PASSPorT claims to cryptographically sign the
   information associated with either the SIP "Resource-Priority" or
   "Priority" header fields and convey assertion of those values by the
   signing party authorization.  A signed SIP "Resource-Priority" or
   "Priority" header fields will allow a receiving entity (including
   entities located in different network domains/boundaries) to verify




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   the validity of assertions to act on the information with confidence
   that the information has not been spoofed or compromised.

   This document adds new assertion values for a Resource Priority
   Header ("rph") claim defined in [RFC8443], in support of Emergency
   Services Networks for emergency call origination and callback.  This
   document also defines a new claim, "sph", including protection of the
   SIP Priority header for the indication of an emergency service call-
   back assigned the value "psap-callback" as defined in [RFC7090].  The
   use of these new assertion values for real-time communications
   supported using the SIP 'Resource-Priority' and 'Priority' header
   fields for emergency services is introduced in
   [I-D.rosen-stir-emergency-calls] but otherwise out-of-scope of this
   document.  In addition, the PASSPorT claims and values defined in
   this document are intended for use in environments where there are
   means to verify that the signer of the SIP 'Resource-Priority' and
   'Priority' header fields is authoritative.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  New Assertion Values for "rph" claim

   This specification defines new assertions values for:

   *  "ESorig": Emergency Services call origination
   *  "EScallback": Emergency Services callback.

3.1.  ESorig

   When using "ESorig" as the "rph" assertion value, the "orig" claim of
   the PASSporT MUST represent the calling party number that initiates
   the call to emergency services.  The "dest" claim MUST either be a
   country or region specific dial string (e.g., "911" for North America
   or "112" GSM defined string used in Europe and other countries) or
   "urn:service:sos" as defined in TBD, representing the emergency
   services destination of the call.

   The following is an example of an "rph" claim for SIP 'Resource-
   Priority' header field with a "ESorig" assertion:






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     {
       "orig":{"tn":"12155551212"},
       "dest":{["uri":"urn:service:sos"]},
       "iat":1443208345,
       "rph":{"ESorig":["esnet,x"]}
     }

3.2.  EScallback

   When using "EScallback" as the "rph" assertion value, the "orig"
   claim of the PASSporT MUST represent the emergency network telephone
   number.  The "dest" claim MUST be the telephone number representing
   the original calling party of the emergency service call that is
   being called back.

   The following is an example of an "rph" claim for SIP 'Resource-
   Priority' header field with a "EScallback" assertion:

     {
       "orig":{"tn":"12155551213"},
       "dest":{["tn":"12155551212"]},
       "iat":1443208345,
       "rph":{"EScallback":["esnet,x"]}
     }

   After the header and claims PASSporT objects have been constructed,
   their signature is generated normally per the guidance in [RFC8225]
   using the full form of PASSPorT.  The credentials (i.e., Certificate)
   used to create the signature must have authority over the namespace
   of the "rph" claim, and there is only one authority per claim.  The
   authority MUST use its credentials associated with the specific
   service supported by the resource priority namespace in the claim.
   If r-values are added or dropped by the intermediaries along the
   path, the intermediaries must generate a new "rph" header and sign
   the claim with their own authority.

4.  The SIP Priority header "sph" claim

   As discussed in [I-D.rosen-stir-emergency-calls], and as defined in
   [RFC7090] the SIP Priority header may be set to the value "psap-
   callback" for emergency services callback calls.  Because some SIP
   networks may act on this value and provide priority or other special
   routing based on this value, it is important to protect and validate
   the authoritative use associated with it.

   Therefore, we define a new claim key as part of the "rph" PASSporT,
   "sph", which MUST be used only for authorized emergency callbacks and
   correspond to a SIP Priority header with the value "psap-callback".



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   The value of the "sph" claim key should only be "psap-callback" to
   match the SIP Priority header field value for authorized emergency
   services callbacks.

   The following is an example of an "sph" claim for SIP 'Priority'
   header field with the value "psap-callback":

     {
       "orig":{"tn":"12155551213"},
       "dest":{["tn":"12155551212"]},
       "iat":1443208345,
       "rph":{"EScallback":["esnet,x"]},
       "sph":"psap-callback"
     }

5.  Order of Claim Keys

   The order of the claim keys MUST follow the rules of [RFC8225]
   Section 9; the claim keys MUST appear in lexicographic order.
   Therefore, the claim keys discussed in this document appear in the
   PASSporT Payload in the following order,

   o  dest

   o  iat

   o  orig

   o  rph

   o  sph

6.  Compact Form of PASSporT

   The use of the compact form of PASSporT is not specified in this
   document or recommended for 'rph' PASSporTs.

7.  IANA Considerations

7.1.  PASSporT Resource Priority Header (rph) Types

   This specification requests that the IANA add two new assertion
   values to the "PASSporT Resource Priority Header (rph) Types"
   Registry as defined in [RFC8443].

   The following assertion values will be added to the registry:





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   * "ESorig": Emergency Services call origination
   * "EScallback": Emergency Services callback

       +--------------+------------+
       | rph Type     | Reference  |
       +--------------+------------+
       | ESorig       | [this RFC] |
       +--------------+------------+
       | EScallback   | [this RFC] |
       +--------------+------------+

7.2.  JSON Web Token claims

   This specification requests that the IANA add two new claims to the
   JSON Web Token Claims registry as defined in [RFC7519].

   Claim Name: "sph"

   Claim Description: SIP Priority header field

   Change Controller: IESG

   Specification Document(s): [RFCThis]

8.  Security Considerations

   The security considerations discussed in [RFC8224], Section 12, are
   applicable here.

9.  References

9.1.  Normative References

   [I-D.rosen-stir-emergency-calls]
              Rosen, B., "Non-Interactive Emergency Calls", draft-rosen-
              stir-emergency-calls-00 (work in progress), March 2020.

   [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,
              <https://www.rfc-editor.org/info/rfc3261>.

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




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   [RFC7090]  Schulzrinne, H., Tschofenig, H., Holmberg, C., and M.
              Patel, "Public Safety Answering Point (PSAP) Callback",
              RFC 7090, DOI 10.17487/RFC7090, April 2014,
              <https://www.rfc-editor.org/info/rfc7090>.

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

   [RFC8224]  Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
              "Authenticated Identity Management in the Session
              Initiation Protocol (SIP)", RFC 8224,
              DOI 10.17487/RFC8224, February 2018,
              <https://www.rfc-editor.org/info/rfc8224>.

   [RFC8225]  Wendt, C. and J. Peterson, "PASSporT: Personal Assertion
              Token", RFC 8225, DOI 10.17487/RFC8225, February 2018,
              <https://www.rfc-editor.org/info/rfc8225>.

   [RFC8226]  Peterson, J. and S. Turner, "Secure Telephone Identity
              Credentials: Certificates", RFC 8226,
              DOI 10.17487/RFC8226, February 2018,
              <https://www.rfc-editor.org/info/rfc8226>.

   [RFC8443]  Singh, R., Dolly, M., Das, S., and A. Nguyen, "Personal
              Assertion Token (PASSporT) Extension for Resource Priority
              Authorization", RFC 8443, DOI 10.17487/RFC8443, August
              2018, <https://www.rfc-editor.org/info/rfc8443>.

9.2.  Informative References

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

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

   [RFC7375]  Peterson, J., "Secure Telephone Identity Threat Model",
              RFC 7375, DOI 10.17487/RFC7375, October 2014,
              <https://www.rfc-editor.org/info/rfc7375>.







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   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

Authors' Addresses

   Martin Dolly
   AT&T

   Email: md3135@att.com


   Chris Wendt
   Comcast
   Comcast Technology Center
   Philadelphia, PA  19103
   USA

   Email: chris-ietf@chriswendt.net



























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