Internet DRAFT - draft-ietf-stir-rph
draft-ietf-stir-rph
STIR R. Singh
Internet-Draft Vencore Labs
Intended status: Standards Track M. Dolly
Expires: November 25, 2018 AT&T
S. Das
Vencore Labs
A. Nguyen
Office of Emergency Communication/DHS
May 24, 2018
PASSporT Extension for Resource Priority Authorization
draft-ietf-stir-rph-06
Abstract
This document extends the PASSporT (Personal Assertion Token)
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, which is used for communications resource
prioritization.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 25, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
Singh, et al. Expires November 25, 2018 [Page 1]
Internet-Draft PASSporT-ext May 2018
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 . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Authentication Service Behavior . . . . . . . . . . . . . 5
4.2. Verification Service Behavior . . . . . . . . . . . . . . 5
5. Further Information Associated with 'Resource-Priority' . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. JSON Web Token Claims . . . . . . . . . . . . . . . . . . 6
6.2. PASSporT Types . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7.1. Avoidance of replay and cut and paste attacks . . . . . . 7
7.2. Solution Considerations . . . . . . . . . . . . . . . . . 7
7.3. Acknowledgements . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
PASSporT [RFC8225] is a token format based on JSON Web Token (JWT)
[RFC7519] for conveying cryptographically signed information about
the identities involved in personal communications. PASSporT with
STIR [RFC8224] provides a mechanism by which an authority on the
originating side of a call via a protocol like SIP [RFC3261] can
provide a cryptographic assurance of the validity of the calling
party telephone number in order to prevent impersonation attacks.
[RFC4412] defines the 'SIP Resource-Priority' header field for
communications 'Resource-Priority'. As specified in [RFC4412], the
'SIP Resource-Priority' header field may be used by SIP user agents
[RFC3261] (including Public Switched Telephone Network (PSTN)
gateways and SIP proxy servers) to influence prioritization afforded
to communication sessions including PSTN calls (e.g., to manage
scarce network resources during network congestion scenarios).
However, the 'SIP Resource-Priority' header field could be spoofed
and abused by unauthorized entities, the threat models and use cases
of which are described in [RFC7375] and [RFC7340], respectively.
Singh, et al. Expires November 25, 2018 [Page 2]
Internet-Draft PASSporT-ext May 2018
Compromise of the 'SIP Resource-Priority' header field [RFC4412]
could lead to misuse of network resource (i.e., during congestion
scenarios) resulting in impacts to 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
'SIP Resource-Priority' can use a PASSPorT claim to cryptographically
sign the 'SIP Resource-Priority' header field and convey assertion of
the authorization for 'Resource-Priority'. Signed 'SIP Resource-
Priority' header field will allow a receiving entity (including
entities located in different network domains/boundaries) to verify
the validity of assertions authorizing 'Resource-Priority' and to act
on the information with confidence that the information has not been
spoofed or compromised.
This specification documents an extension to PASSporT and the
associated STIR mechanisms to provide a function to cryptographically
sign the 'SIP Resource-Priority' header field. This PASSporT object
is used to provide attestation of a calling user authorization for
priority communications. This is necessary in addition to the
PASSporT object that is used for calling user telephone number
attestation. How this extension to PASSporT is used for real-time
communications supported using 'SIP Resource-Priority' header field
is outside the scope of this document. In addition, the PASSPorT
extension defined in this document is intended for use in
environments where there are means to verify that the signer of the
'SIP Resource-Priority' header field is authoritative.
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] and
in RFC 8174 [RFC8174].
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 field.
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:
Singh, et al. Expires November 25, 2018 [Page 3]
Internet-Draft PASSporT-ext May 2018
{
"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 based on
[RFC4412] and the syntax is:
{
Resource-Priority = "Resource-Priority" : r-value,
r-value= namespace "." r-priority
}
Specifically, the "rph" claim includes an assertion of the priority-
level of the user to be used for a given communication session. The
value of the "rph" claim is an Object with one or more keys. Each
key is associated with a JSON Array. These arrays contain Strings
that correspond to the r-values indicated in the 'SIP Resource-
Priority' header field.
The following is an example "rph" claim for a 'SIP Resource-Priority'
header field with one r-value of "ets.0" and with another r-value of
"wps.0":
{
"orig":{"tn":"12155550112"},
"dest":{["tn":"12125550113"]},
"iat":1443208345,
"rph":{"auth":["ets.0", "wps.0"]}
}
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, intermediaries must generate a new "rph" header and sign the
claim with its own authority.
The use of the compact form of PASSporT is not specified in this
document.
Singh, et al. Expires November 25, 2018 [Page 4]
Internet-Draft PASSporT-ext May 2018
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 of this document that are based on
[RFC4412]. The construction of "rph" claim follows the steps
described in Section 4.1 of [RFC8224].
The resulting Identity header for "rph" might look as
follows(backslashes shown for line folding only):
Identity:eyJhbGciOiJFUzI1NiIsInBwdCI6InJwaCIsInR5cCI6InBhc3Nwb3J0\
IiwieDV1IjoiaHR0cHM6Ly93d3cuZXhhbXBsZS5jb20vY2VydC5jZXIifQo.eyJkZ\
XN0Ijp7WyJ0biI6IjEyMTI1NTUwMTEzIl19LCJpYXQiOiIxNDQzMjA4MzQ1Iiwib3\
JpZyI6eyJ0biI6IjEyMTU1NTUwMTEyIn0sInJwaCI6eyJhdXRoIjpbImV0cy4wIiw\
id3BzLjAiXX19Cg.s37S6VC8HM6Dl6YzJeQDsrZcwJ0lizxhUrA7f_98oWBHvo-cl\
-n8MIhoCr18vYYFy3blXvs3fslM_oos2P2Dyw;info=<https://www.example.\
org/cert.cer>;alg=ES256;ppt="rph"
A SIP authentication service will derive the value of "rph" from the
'SIP Resource-Priority' header field based on policy associated with
service specific use of the "namespace "." r-priority" for r-values
based on [RFC4412]. The authentication service derives the value of
the PASSPorT claim by verifying the authorization for 'SIP Resource-
Priority' (i.e., verifying a calling user privilege for 'Resource-
Priority' based on its identity) which might be derived from customer
profile data or from access to external services.
[RFC4412] allows multiple "namespace "." priority value" pairs,
either in a single 'SIP Resource-Priority' header field or across
multiple 'SIP Resource-Priority' headers. An authority is
responsible for signing all the content of a 'SIP Resource-Priority'
header field for which it has the authority.
4.2. Verification Service Behavior
[RFC8224] 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
Singh, et al. Expires November 25, 2018 [Page 5]
Internet-Draft PASSporT-ext May 2018
authorized for 'SIP Resource-Priority' as indicated in the claim.
This value would in turn be used for priority treatment in accordance
with local policy for the associated communication service. If the
signature validation fails, the verification service should infer
that the calling party is not authorized for 'SIP Resource-Priority'
as indicated in the claim. In such cases, the priority treatment for
the associated communication service is handled as per the local
policy of the verifier. In such scenarios, 'SIP Resource-Priority'
header field SHOULD be stripped from SIP request and the network
entities should treat the call as an ordinary call.
In addition, [RFC8224] Section 6.2 Step 4 requires the "iat" value in
"rph" claim to be verified.
The behavior of a SIP UA 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 'SIP 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 applicable to 'SIP Resource-
Priority'.
A new IANA registry has been defined to hold potential values of the
"rph" array; see Section 6.2. The definition of the "rph" claim may
have one or more such additional information field(s). Details of
such "rph" claim to encompass other data elements are left for future
version of this specification.
6. IANA Considerations
6.1. JSON Web Token Claims
This specification requests that the IANA add a new claim to the JSON
Web Token Claims registry as defined in [RFC7519].
o Claim Name: "rph"
Singh, et al. Expires November 25, 2018 [Page 6]
Internet-Draft PASSporT-ext May 2018
o Claim Description: Resource Priority Header Authorization
o Change Controller: IESG
o Specification Document(s): Section 3 of [RFCThis]
6.2. PASSporT Types
This specification also requests that the IANA creates a new entry to
the PASSporT Types registry for the type "rph" which is specified in
[RFCThis]. In addition, another registry needs to be created in
which each entry must contain two fields: the name of the "rph" type
and the specification in which the type is described. This registry
is to be initially populated with a single value for "auth" which is
specified in [RFCThis]. Registration of new "rph" types shall be
under the specification required policy.
7. Security Considerations
The security considerations discussed in [RFC8224] in Section 12 are
applicable here.
7.1. Avoidance of replay and cut and paste attacks
The PASSporT extension with a "ppt" value of "rph" MUST only be sent
with SIP INVITE when 'Resource-Priority' header field is used to
convey the priority of the communication as defined in [RFC4412]. To
avoid replay, and cut and paste attacks, the recommendations provided
in Section 12.1 of [RFC8224] MUST be followed.
7.2. Solution Considerations
Using extensions to PASSporT tokens with a "ppt" value of "rph"
requires knowledge of the authentication, authorization, and
reputation of the signer to attest to the identity being asserted,
including validating the digital signature and the associated
certificate chain to a trust anchor. The following considerations
should be recognized when using PASSporT extensions with a "ppt"
value of "rph":
o A signer is only allowed to sign the content of a 'SIP Resource-
Priority' header field for which it has the proper authorization.
Before signing tokens, the signer MUST have a secure method for
authentication of the end user or the device being granted a
token.
Singh, et al. Expires November 25, 2018 [Page 7]
Internet-Draft PASSporT-ext May 2018
o The verification of the signature MUST include means of verifying
that the signer is authoritative for the signed content of the
resource priority namespace in the PASSporT.
7.3. Acknowledgements
We would like to thank STIR WG 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 and Ning Zhang for their valuable
inputs.
8. References
8.1. Normative References
[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>.
[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>.
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <http://www.rfc-editor.org/info/rfc8174>.
[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,
<http://www.rfc-editor.org/info/rfc8224>.
Singh, et al. Expires November 25, 2018 [Page 8]
Internet-Draft PASSporT-ext May 2018
[RFC8225] Wendt, C. and J. Peterson, "PASSporT:Personal Assertion
Token", RFC 8225, DOI 10.17487/RFC8225, February 2018,
<http://www.rfc-editor.org/info/rfc8225>.
8.2. Informative References
[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>.
[RFC7375] Peterson, J., "Secure Telephone Identity Threat Model",
RFC 7375, DOI 10.17487/RFC7375, October 2014,
<http://www.rfc-editor.org/info/rfc7375>.
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
Singh, et al. Expires November 25, 2018 [Page 9]
Internet-Draft PASSporT-ext May 2018
An Nguyen
Office of Emergency Communication/DHS
245 Murray Lane, Building 410
Washington, DC 20528
USA
Email: an.p.nguyen@HQ.DHS.GOV
Singh, et al. Expires November 25, 2018 [Page 10]
