STIR C. Wendt
Internet-Draft Comcast
Intended status: Standards Track M. Barnes
Expires: April 20, 2019 iconectiv
October 17, 2018
PASSporT SHAKEN Extension (SHAKEN)
draft-ietf-stir-passport-shaken-04
Abstract
This document extends PASSporT, which is a token object that conveys
cryptographically-signed information about the participants involved
in communications, to include information defined as part of the
SHAKEN specification from ATIS (Alliance for Telecommunications
Industry Solutions) and the SIP Forum IP-NNI Joint Task Force. These
extensions provide a level of confidence in the correctness of the
originating identity for a telephone network that has communications
coming from both STIR participating originating communications as
well as communications that does not include STIR information.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Overview of 'shaken' PASSporT extension . . . . . . . . . . . 3
4. PASSporT 'attest' Claim . . . . . . . . . . . . . . . . . . . 3
5. PASSporT 'origid' Claim . . . . . . . . . . . . . . . . . . . 4
6. Example "shaken" PASSporT . . . . . . . . . . . . . . . . . . 4
7. Using 'shaken' in SIP . . . . . . . . . . . . . . . . . . . . 5
8. Order of Claim Keys . . . . . . . . . . . . . . . . . . . . . 5
9. Security Considerations . . . . . . . . . . . . . . . . . . . 5
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
10.1. JSON Web Token claims . . . . . . . . . . . . . . . . . 6
10.2. PASSporT Types . . . . . . . . . . . . . . . . . . . . . 6
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
12.1. Normative References . . . . . . . . . . . . . . . . . . 7
12.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
The SHAKEN [ATIS-1000074] specification defines a framework for using
STIR protocols including PASSporT [RFC8225], SIP Authenticated
Identity Management [RFC8224] and the STIR certificate framework
[RFC8226] for implementing the cryptographic validation of an
authorized originator of telephone calls using SIP. Because the
current telephone network contains both VoIP and TDM/SS7 originated
traffic, there are many scenarios that need to be accounted for where
PASSporT signatures may represent either direct or indirect call
origination scenarios. The SHAKEN [ATIS-1000074] specification
defines levels of attestation of the origination of the call as well
as an origination identifier that can help create a unique
association with the origination of calls from various parts of the
VoIP or TDM telephone network. This document specifies these
indicators as a specified PASSporT extension.
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].
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3. Overview of 'shaken' PASSporT extension
The SHAKEN framework is designed to use PASSporT [RFC8225] as a
method of asserting the telephone number calling identity. In
addition to the PASSporT base claims, there are two additional claims
that have been defined for the needs of a service provider to signal
information beyond just the telephone identity. First, in order to
help bridge the transition of the state of the current telephone
network which has calls with no authentication and non-SIP [RFC3261]
signaling not compatible with the use of PASSporT and Secure
Telephone Identity (STI) in general, there is an attestation claim.
This provides three levels of attestation, including a full
attestation when the service provider can fully attest to the calling
identity, a partial attestation, when the service provider originated
a telephone call but can not fully attest to the calling identity,
and a gateway attestation which is the lowest level of attestation
and represents the service provider receiving a call from a non
PASSporT or STI supporting telephone gateway.
The second claim is a unique origination identifier that should be
used by the service provider to identify different sources of
telephone calls to support a traceback mechanism that can be used for
enforcement and identification of a source of illegitimate calls.
The use of the compact form of PASSporT is not specified in this
document and is not specified for use in SHAKEN [ATIS-1000074].
The next two sections define these new claims.
4. PASSporT 'attest' Claim
This indicator allows for both identifying the service provider that
is vouching for the call as well as clearly indicating what
information the service provider is attesting to. The 'attest' claim
can be one of the following three values, 'A', 'B', or 'C' as defined
in [ATIS-1000074].
'A' represents 'Full Attestation' where the signing provider MUST
satisfy all of the following conditions:
o Is responsible for the origination of the call onto the IP based
service provider voice network.
o Has a direct authenticated relationship with the initiator of the
call and can identify the customer associated with the initiator.
o Has established a verified association with the calling party
telephone number used for the call.
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'B' represents 'Partial Attestation' where the signing provider MUST
satisfy all of the following conditions:
o Is responsible for the origination of the call onto its IP-based
voice network.
o Has a direct authenticated relationship with the initiator of the
call and can identify the customer associated with the initiator.
o Has NOT established a verified association with the calling party
telephone number being used for the call.
'C' represents 'Gateway Attestation' where the signing provider MUST
satisfy all of the following conditions:
o Is the entry point of the call into its VoIP network.
o Has no relationship with the initiator of the call (e.g.,
international gateways)
5. PASSporT 'origid' Claim
The purpose of the unique origination identifier is to assign an
opaque identifier corresponding to the service provider-initiated
calls themselves, customers, classes of devices, or other groupings
that a service provider might want to use for determining things like
reputation or trace back identification of customers or gateways.
The value of 'origid' claim is a UUID as defined in [RFC4122].
SHAKEN isn't prescriptive in the exact usage of origid other than the
UUID format as a globally unique identifier representing the
originator of the call to whatever granularity the PASSporT signer
determines is sufficient for the ability to trace the original
origination point of the call. There will likely be best practices
documents that more precisely guide it's usage in real deployments.
6. Example "shaken" PASSporT
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Protected Header
{
"alg":"ES256",
"typ":"passport",
"ppt":"shaken",
"x5u":"https://cert.example.org/passport.cer"
}
Payload
{
"attest":"A"
"dest":{"uri":["sip:alice@example.com"]}
"iat":"1443208345",
"orig":{"tn":"12155551212"},
"origid":"123e4567-e89b-12d3-a456-426655440000"
}
7. Using 'shaken' in SIP
The use of the 'shaken' PASSporT type and the claims 'attest' and
'origid' are formally defined in [ATIS-1000074] for usage in SIP
[RFC3261] aligned with the use of the identity header defined in
[RFC8224].
8. 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 attest
o dest
o iat
o orig
o origid
9. Security Considerations
This document defines a new PASSporT [RFC8225] extension. The
considerations related to the security of the PASSporT object itself
are the same as those described in [RFC8225].
[RFC8224] defines how to compare the values of the "dest", "orig" and
"iat" claims against fields in a SIP containing a PASSporT as part of
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validating that request. The values of the new "attest" and "origid"
claims added by this extension are not used in such a validation
step. They are not compared to fields in the SIP message. Instead,
they simply carry additional information from the signer to the
consumer of the PASSport. This new information shares the same
integrity protection and non-repudiation properties as the base
claims in the PASSporT.
10. IANA Considerations
10.1. 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: "attest"
Claim Description: Attestation level as defined in SHAKEN framework
Change Controller: IESG
Specification Document(s): [RFCThis]
Claim Name: "origid"
Claim Description: Originating Identifier as defined in SHAKEN
framework
Change Controller: IESG
Specification Document(s): [RFCThis]
10.2. PASSporT Types
This specification requests that the IANA add a new entry to the
Personal Assertion Token (PASSporT) Extensions registry for the type
"shaken" which is specified in [RFCThis].
11. Acknowledgements
The authors would like to thank those that helped review and
contribute to this document including specific contributions from Jon
Peterson, Russ Housley, and Andrew Jurczak. The authors would like
acknowledge the work of the ATIS/SIP Forum IP-NNI Task Force to
develop the concepts behind this document.
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12. References
12.1. Normative References
[ATIS-1000074]
ATIS/SIP Forum NNI Task Group, "Signature-based Handling
of Asserted information using toKENs (SHAKEN)", January
2017, <https://access.atis.org/apps/group_public/
download.php/32237/ATIS-1000074.pdf>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>.
[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>.
12.2. 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>.
[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>.
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Authors' Addresses
Chris Wendt
Comcast
One Comcast Center
Philadelphia, PA 19103
USA
Email: chris-ietf@chriswendt.net
Mary Barnes
iconectiv
Email: mary.ietf.barnes@gmail.com
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