Internet DRAFT - draft-ietf-stir-passport-shaken
draft-ietf-stir-passport-shaken
STIR C. Wendt
Internet-Draft Comcast
Intended status: Standards Track M. Barnes
Expires: September 11, 2019 iconectiv
March 10, 2019
PASSporT SHAKEN Extension (SHAKEN)
draft-ietf-stir-passport-shaken-08
Abstract
This document extends PASSporT, which is a token object that conveys
cryptographically-signed information about the participants involved
in communications. The extension is defined, corresponding to the
SHAKEN specification, to provide both a specific set of levels-of-
confidence in the correctness of the originating identity for a SIP
based Communication Service Provider (CSP) telephone network
originated call as well as an identifier that allows the CSP to
uniquely identify the origin of the call within its network.
Status of This Memo
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Copyright Notice
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview of 'shaken' PASSporT extension . . . . . . . . . . . 3
4. PASSporT 'attest' Claim . . . . . . . . . . . . . . . . . . . 4
5. PASSporT 'origid' Claim . . . . . . . . . . . . . . . . . . . 4
6. Example "shaken" PASSporT . . . . . . . . . . . . . . . . . . 4
7. Using 'shaken' in SIP . . . . . . . . . . . . . . . . . . . . 4
8. Order of Claim Keys . . . . . . . . . . . . . . . . . . . . . 4
9. Security Considerations . . . . . . . . . . . . . . . . . . . 5
10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 5
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
11.1. JSON Web Token claims . . . . . . . . . . . . . . . . . 6
11.2. PASSporT Types . . . . . . . . . . . . . . . . . . . . . 6
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
13.1. Normative References . . . . . . . . . . . . . . . . . . 7
13.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
The Signature-based Handling of Asserted information using toKENs
(SHAKEN) [ATIS-1000074] specification defines a framework for using
Secure Telephone Identity Revisited (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 between the origin of a particular
call to the point in the VoIP or TDM telephone network the call came
from to identify, for example, either a customer or class of service
that call represents. This document specifies these values as claims
to extend the base set of PASSporT claims.
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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.
In addition, the following terms are used in this document:
o Verified association: is typically defined as an authenticated
relationship between a customer and a device that initiated a call
on behalf of that customer, for example, a subscriber account with
a specific SIM card or set of SIP credentials.
o PASSporT: Defined in [RFC8225] is a JSON Web Token [RFC7519]
defined specifically for securing the identity of an initiator of
personal communication. This document defines a specific
extension to PASSporT.
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 and non-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.
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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'. These
values correspond to 'Full Attestation', 'Partial Attestation', and
'Gateway Attestation', respectively. See [ATIS-1000074] for the
definitions of these three levels of attestation.
5. PASSporT 'origid' Claim
The purpose of the 'origid' claim is described in [ATIS-1000074].
The value of 'origid' claim is a UUID as defined in [RFC4122].
Please refer to Section 10 for a discussion of the privacy
considerations around the use of this value.
6. Example "shaken" PASSporT
Protected Header
{
"alg":"ES256",
"typ":"passport",
"ppt":"shaken",
"x5u":"https://cert.example.org/passport.cer"
}
Payload
{
"attest":"A"
"dest":{"tn":["12155550131"]}
"iat":"1443208345",
"orig":{"tn":"12155550121"},
"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 field 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,
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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
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. Privacy Considerations
As detailed in [RFC3261] Section 26, SIP messages inherently carry
identifying information of the caller and callee. The addition of
STIR cryptographically attests that the signing party vouches for the
information given about the callee, as is discussed in the Privacy
Considerations of [RFC8224].
SHAKEN [ATIS-1000074] furthermore adds an 'origid' value to the STIR
PASSporT, which is an opaque unique identifier representing an
element on the path of a given SIP request. This identifier is
generated by an originating telephone service provider to identify
where within their network (e.g. a gateway or particular service
element) a call was initiated; 'origid' can facilitate forensic
analysis of call origins when identifying and stopping bad actors
trying to spoof identities or make fraudulent calls.
The opacity of the 'origid' claim value is intended to minimize
exposure of information about the origination of calls labelled with
an 'origid' value. It is therefore RECOMMENDED that implementations
generate a unique 'origid' value per call in such a way that only the
generator of the 'origid' can determine when two 'origid' values
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represent the same or different elements. If deployed systems
instead use a common or related 'origid' for service elements in
their network, the potential for discovering patterns through
correlation of those calls exists. This could allow a recipient of
calls to, for instance, learn that a set of callers are using a
particular service or coming through a common gateway. It is
expected that SHAKEN PASSporTs are shared only within an [RFC3324]
trust domain and will be stripped before calls exit that trust
domain, but this information still could be used by analytics on
intermediary and terminating systems to reveal information that could
include geographic location and even device-level information,
depending on how the 'origid' is generated.
11. IANA Considerations
11.1. 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]
11.2. 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].
12. Acknowledgements
The authors would like to thank those that helped review and
contribute to this document including specific contributions from Jon
Peterson, Russ Housley, Robert Sparks, and Andrew Jurczak. The
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authors would like to acknowledge the work of the ATIS/SIP Forum IP-
NNI Task Force to develop the concepts behind this document.
13. References
13.1. Normative References
[ATIS-1000074]
ATIS/SIP Forum IP-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>.
13.2. 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>.
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[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>.
[RFC3323] Peterson, J., "A Privacy Mechanism for the Session
Initiation Protocol (SIP)", RFC 3323,
DOI 10.17487/RFC3323, November 2002,
<https://www.rfc-editor.org/info/rfc3323>.
[RFC3324] Watson, M., "Short Term Requirements for Network Asserted
Identity", RFC 3324, DOI 10.17487/RFC3324, November 2002,
<https://www.rfc-editor.org/info/rfc3324>.
[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
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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