< draft-ietf-stir-rph-emergency-services-05.txt   draft-ietf-stir-rph-emergency-services-07.txt >
STIR M. Dolly STIR M. Dolly
Internet-Draft AT&T Internet-Draft AT&T
Intended status: Standards Track C. Wendt Intended status: Standards Track C. Wendt
Expires: July 29, 2021 Comcast Expires: September 12, 2021 Comcast
January 25, 2021 March 11, 2021
Assertion Values for a Resource Priority Header Claim and a SIP Priority Assertion Values for a Resource Priority Header Claim and a SIP Priority
Header Claim in Support of Emergency Services Networks Header Claim in Support of Emergency Services Networks
draft-ietf-stir-rph-emergency-services-05 draft-ietf-stir-rph-emergency-services-07
Abstract Abstract
This document adds new assertion values for a Resource Priority This document adds new assertion values for a Resource Priority
Header ("rph") claim and a new SIP Priority Header claim ("sph") for Header ("rph") claim and a new SIP Priority Header claim ("sph") for
protection of the "psap-callback" value as part of the "rph" PASSporT protection of the "psap-callback" value as part of the "rph" PASSporT
extension, in support of the security of Emergency Services Networks extension, in support of the security of Emergency Services Networks
for emergency call origination and callback. for emergency call origination and callback.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 29, 2021. This Internet-Draft will expire on September 12, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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signing party authorization. A signed SIP "Resource-Priority" or signing party authorization. A signed SIP "Resource-Priority" or
"Priority" header field will allow a receiving entity (including "Priority" header field will allow a receiving entity (including
entities located in different network domains/boundaries) to verify entities located in different network domains/boundaries) to verify
the validity of assertions to act on the information with confidence the validity of assertions to act on the information with confidence
that the information has not been spoofed or compromised. that the information has not been spoofed or compromised.
This document adds new "auth" array key values for a Resource This document adds new "auth" array key values for a Resource
Priority Header ("rph") claim defined in [RFC8443], in support of Priority Header ("rph") claim defined in [RFC8443], in support of
Emergency Services Networks for emergency call origination and Emergency Services Networks for emergency call origination and
callback. This document additionally defines a new PASSporT claim, callback. This document additionally defines a new PASSporT claim,
"sph", including protection of the SIP Priority header for the "sph", including protection of the SIP Priority header field for the
indication of an emergency service call-back assigned the value indication of an emergency service call-back assigned the value
"psap-callback" as defined in [RFC7090]. The use of the newly "psap-callback" as defined in [RFC7090]. The use of the newly
defined claim and key values corresponding to the SIP 'Resource- defined claim and key values corresponding to the SIP 'Resource-
Priority' and 'Priority' header fields for emergency services is Priority' and 'Priority' header fields for emergency services is
introduced in [I-D.rosen-stir-emergency-calls] but otherwise out-of- introduced in [I-D.rosen-stir-emergency-calls] but otherwise out-of-
scope of this document. In addition, the PASSPorT claims and values scope of this document. In addition, the PASSPorT claims and values
defined in this document are intended for use in environments where defined in this document are intended for use in environments where
there are means to verify that the signer of the SIP 'Resource- there are means to verify that the signer of the SIP 'Resource-
Priority' and 'Priority' header fields is authoritative. Priority' and 'Priority' header fields is authoritative.
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14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. New Assertion Values for "rph" claim 3. New Assertion Values for "rph" claim
This specification defines the ability to sign the SIP Resource- This specification defines the ability to sign the SIP Resource-
Priority Header field namespace for local emergency communications Priority Header field namespace for local emergency communications
defined in [RFC7135] and represented by the string "esnet.x" where x defined in [RFC7135] and represented by the string "esnet.x" where x
is the priority-level allowed in the esnet namespace. As of the is the priority-level allowed in the esnet namespace. As of the
writing of this specification the priority-level is between 0 and 4, writing of this specification the priority-level is between 0 and 4,
but may be extended by future specifications. inclusive, but may be extended by future specifications.
Similar to the values allowed by [RFC8443] for the "auth" JSON object Similar to the values defined by [RFC8443] for the "auth" JSON object
key inside the "rph" claim, the string "esnet.x" with the appropriate key inside the "rph" claim, the string "esnet.x" with the appropriate
value should be used when resource priority is required for local value should be used when resource priority is required for local
emergency communications corresponding and exactly matching the SIP emergency communications corresponding and exactly matching the SIP
Resource-Priority header string representing the namespace invoked in Resource-Priority header field representing the namespace invoked in
the call. the call.
When using "esnet.x" as the "auth" assertion value in emergency When using "esnet.x" as the "auth" assertion value in emergency
service destined calls, the "orig" claim of the PASSporT MUST service destined calls, the "orig" claim of the PASSporT MUST
represent the calling party number that initiates the call to represent the calling party number that initiates the call to
emergency services. The "dest" claim MUST either be a country or emergency services. The "dest" claim MUST either be a country or
region specific dial string (e.g., "911" for North America or "112" region specific dial string (e.g., "911" for North America or "112"
GSM defined string used in Europe and other countries) or GSM defined string used in Europe and other countries) or
"urn:service:sos" as defined in [RFC5031], representing the emergency "urn:service:sos" as defined in [RFC5031], representing the emergency
services destination of the call. services destination of the call.
The following is an example of an "rph" claim for SIP 'Resource- The following is an example of an "rph" claim for SIP 'Resource-
Priority' header field with an "esnet.1" assertion: Priority' header field with an "esnet.1" assertion:
{ {
"orig":{"tn":"12155551212"},
"dest":{"uri":["urn:service:sos"]}, "dest":{"uri":["urn:service:sos"]},
"iat":1443208345, "iat":1615471428,
"orig":{"tn":"12155551212"},
"rph":{"auth":["esnet.1"]} "rph":{"auth":["esnet.1"]}
} }
For emergency services callbacks, the "orig" claim of the "rph" For emergency services callbacks, the "orig" claim of the "rph"
PASSporT MUST represent the Public Saftey Answering Point (PSAP) PASSporT MUST represent the Public Saftey Answering Point (PSAP)
telephone number. The "dest" claim MUST be the telephone number telephone number. The "dest" claim MUST be the telephone number
representing the original calling party of the emergency service call representing the original calling party of the emergency service call
that is being called back. that is being called back.
The following is an example of an "rph" claim for SIP 'Resource- The following is an example of an "rph" claim for SIP 'Resource-
Priority' header field with a "esnet.0" assertion: Priority' header field with a "esnet.0" assertion:
{ {
"orig":{"tn":"12155551213"},
"dest":{"tn":["12155551212"]}, "dest":{"tn":["12155551212"]},
"iat":1443208345, "iat":1615471428,
"orig":{"tn":"12155551213"},
"rph":{"auth":["esnet.0"]} "rph":{"auth":["esnet.0"]}
} }
After the header and claims PASSporT objects have been constructed, After the header and claims PASSporT objects have been constructed,
their signature is generated normally per the guidance in [RFC8225] their signature is generated normally per the guidance in [RFC8225]
using the full form of PASSPorT. The credentials (i.e., Certificate) using the full form of PASSPorT. The credentials (i.e., Certificate)
used to create the signature must have authority over the namespace used to create the signature must have authority over the namespace
of the "rph" claim, and there is only one authority per claim. The of the "rph" claim, and there is only one authority per claim. The
authority MUST use its credentials associated with the specific authority MUST use its credentials associated with the specific
service supported by the resource priority namespace in the claim. service supported by the resource priority namespace in the claim.
If r-values are added or dropped by the intermediaries along the If r-values are added or dropped by the intermediaries along the
path, the intermediaries must generate a new "rph" header and sign path, the intermediaries must generate a new "rph" identity header
the claim with their own authority. and sign the claim with their own authority.
4. The SIP Priority header "sph" claim 4. The SIP Priority header "sph" claim
As defined in [RFC7090] the SIP Priority header may be set to the As defined in [RFC7090] the SIP Priority header field may be set to
value "psap-callback" for emergency services callback calls. Because the value "psap-callback" for emergency services callback calls.
some SIP networks may act on this value and provide priority or other Because some SIP networks may act on this value and provide priority
special routing based on this value, it is important to protect and or other special routing based on this value, it is important to
validate the authoritative use associated with it. protect and validate the authoritative use associated with it.
Therefore, we define a new claim key as part of the "rph" PASSporT, Therefore, we define a new claim key as part of the "rph" PASSporT,
"sph". This is an optional claim that MUST only be used only with an "sph". This is an optional claim that MUST only be used only with an
"auth" claim with an "esnet.x" value indicating an authorized "auth" claim with an "esnet.x" value indicating an authorized
emergency callback call and corresponding to a SIP Priority header emergency callback call and corresponding to a SIP Priority header
with the value "psap-callback". field with the value "psap-callback".
The value of the "sph" claim key should only be "psap-callback" which The value of the "sph" claim key should only be "psap-callback" which
MUST match the SIP Priority header field value for authorized MUST match the SIP Priority header field value for authorized
emergency services callbacks. If the value is anything other than emergency services callbacks. If the value is anything other than
"psap-callback", the PASSporT validation MUST be considered a failure "psap-callback", the PASSporT validation MUST be considered a failure
case. case.
Note: Because the intended use of this specification is only for Note: Because the intended use of this specification is only for
emergency services, there is also an explicit assumption that the emergency services, there is also an explicit assumption that the
signer of the "rph" PASSporT can authoritatively represent both the signer of the "rph" PASSporT can authoritatively represent both the
content of the Resource Priority Header and Priority Header content of the Resource Priority Header field and Priority Header
information associated specifically with a emergency services field information associated specifically with a emergency services
callback case where both could exist. This document is not intended callback case where both could exist. This document is not intended
to be a general mechanism for protecting SIP Priority Header fields, to be a general mechanism for protecting SIP Priority Header fields,
this could be accomplished as part of future work with a new PASSporT this could be accomplished as part of future work with a new PASSporT
extension or new claim added to either an existing PASSporT or extension or new claim added to either an existing PASSporT or
PASSporT extension usage. PASSporT extension usage.
The following is an example of an "sph" claim for SIP 'Priority' The following is an example of an "sph" claim for SIP 'Priority'
header field with the value "psap-callback": header field with the value "psap-callback":
{ {
"orig":{"tn":"12155551213"},
"dest":{"tn":["12155551212"]}, "dest":{"tn":["12155551212"]},
"iat":1443208345, "iat":1615471428,
"orig":{"tn":"12155551213"},
"rph":{"auth":["esnet.0"]}, "rph":{"auth":["esnet.0"]},
"sph":"psap-callback" "sph":"psap-callback"
} }
5. Order of Claim Keys 5. Order of Claim Keys
The order of the claim keys MUST follow the rules of [RFC8225] The order of the claim keys MUST follow the rules of [RFC8225]
Section 9; the claim keys MUST appear in lexicographic order. Section 9 which defines the deterministic JSON serialization used for
Therefore, the claim keys discussed in this document appear in the signature generation (and validation); the claim keys MUST appear in
PASSporT Payload in the following order, lexicographic order. Therefore, the claim keys discussed in this
document appear in the PASSporT Payload in the following order,
o dest o dest
o iat o iat
o orig o orig
o rph o rph
o sph o sph
6. Compact Form of PASSporT 6. Compact Form of PASSporT
The use of the compact form of PASSporT is not specified in this The use of the compact form of PASSporT is not specified in this
document or recommended for 'rph' PASSporTs. document or recommended for 'rph' PASSporTs.
7. Acknowledgements 7. Acknowledgements
The authors would like to thank Brian Rosen, Terry Reese, and Jon The authors would like to thank Brian Rosen, Terry Reese, and Jon
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Claim Name: "sph" Claim Name: "sph"
Claim Description: SIP Priority header field Claim Description: SIP Priority header field
Change Controller: IESG Change Controller: IESG
Specification Document(s): [RFCThis] Specification Document(s): [RFCThis]
9. Security Considerations 9. Security Considerations
The security considerations discussed in [RFC8224], Section 12, are The security considerations discussed in [RFC8224], [RFC8225], and
applicable here. [RFC8443] are applicable here.
10. References 10. References
10.1. Normative References 10.1. Normative References
[RFC4412] Schulzrinne, H. and J. Polk, "Communications Resource [RFC4412] Schulzrinne, H. and J. Polk, "Communications Resource
Priority for the Session Initiation Protocol (SIP)", Priority for the Session Initiation Protocol (SIP)",
RFC 4412, DOI 10.17487/RFC4412, February 2006, RFC 4412, DOI 10.17487/RFC4412, February 2006,
<https://www.rfc-editor.org/info/rfc4412>. <https://www.rfc-editor.org/info/rfc4412>.
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