Internet DRAFT - draft-asveren-stir-p-charge-info
draft-asveren-stir-p-charge-info
STIR T. Asveren
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Intended status: Standards Track May 8, 2018
Expires: November 9, 2018
PASSPorT Extension for P-Charge-Info Header
draft-asveren-stir-p-charge-info-00
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) P-Charge-Info'
header, which is used for conveying information about the entity to
be charged for a particular real time session.
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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. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. PASSPortT 'pci' Claim . . . . . . . . . . . . . . . . . . . . 3
4. Using 'pci' in SIP . . . . . . . . . . . . . . . . . . . . . 3
4.1. Authentication Service Behavior . . . . . . . . . . . . . 4
4.2. Verification Service Behavior . . . . . . . . . . . . . . 4
4.3. Other Behavior . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. Informative References . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
PASSporT RFC 8225 [RFC8225] is a token format based on JSON Web Token
(JWT) RFC 7519 [RFC7519] for conveying cryptographically signed
information about the identities involved in personal communications;
it is used with STIR RFC 8224 [RFC8224] to convey a signed assertion
of the identity of the participants in real-time communications
established via a protocol like SIP RFC 3261 [RFC3261]. This
specification extends PASSporT to allow cryptographic-signing of the
'SIP P-Charge-Info' header [RFCXXX], which is used to provide
information about the party to be charged for a real time session.
'SIP P-Charge-Info' header could be spoofed and abused by
unauthorized entities. Compromise of the 'SIP P-Charge-Info' header
would allow charging fraud.
Extension mechanisms defined in RFC8225 can be utilized to
cyrptographically sign the 'SIP P-Charge-Info' header. This would
allow a receiving entity to verify the validity of this header.
This specification documents an extension to PASSporT and the
associated STIR mechanisms to provide a function to sign the 'SIP P-
Charge-Info' header.
2. Requirements Language
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.
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3. PASSPortT 'pci' Claim
This specification defines a new JSON Web Token claim for "pci",
which provides an assertion for information in 'SIP P-Charge-Info'
header.
The creator of a PASSporT object adds a "ppt" value of "pci" to the
header of a PASSporT object, in which case the PASSporT claims MUST
contain a "pci" 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:
{
"typ":"passport",
"ppt":"pci",
"alg":"ES256",
"x5u":"https://www.example.org/cert.cer"
}
The "pci" claim will provide an assertion for information in the 'SIP
P-Charge-Info' header as defined in [RFCXXX] .
After the header and claims PASSporT objects have been constructed,
their signature is generated normally per the guidance in [RFC8225].
The credentials (i.e., Certificate) used to create the signature must
have authority over the "pci" claim and there is only one authority
per claim. If P-Charge-Info header is added or by the intermediaries
along the path, intermediaries must generate a new "pci" header and
sign the claim with its own authority.
The following is an example "pci" claim for a 'SIP P-Charge-Info'
header field with a value of "12125550100"
{
"orig":{"tn":"12155550112"},
"dest":{["tn":"12125550113"]},
"iat":1443208345,
"pci":{["tn": "12125550100"]}
}
4. Using 'pci' in SIP
This section specifies SIP-specific usage for the "pci" PASSporT type
and its handling in the SIP Identity header field "ppt" parameter
value. Other using protocols of PASSporT may define behavior
specific to their use of the "pci" claim.
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4.1. Authentication Service Behavior
An authentication service adds an Identity header field containing
the "pci" PASSporT type to an SIP request only if it adds a P-Charge-
Info header to the request. Whether to add such an Identity header
is controlled by local policy. When adding an Identity header field
with a PASSporT object containing a "pci" claim, SIP authentication
services MUST also add a "ppt" parameter to that Identity header with
a value of "pci". The resulting Identity header field to add to the
message might look as follows:
Identity: eyJhbGciOiJFUzI1NiIsInR5cCI6InBhc3Nwb3J0IiwieDV1I \
joiaHR0cHM6Ly9jZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNlciJ9.eyJ \
kZXN0Ijp7InVyaSI6WyJzaXA6YWxpY2VAZXhhbXBsZS5jb20iXX0sImlhdC \
I6IjE0NDMyMDgzNDUiLCJvcmlnIjp7InRuIjoiMTIxNTU1NTEyMTIifX0.r \
q3pjT1hoRwakEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYs \
ojNCpTzO3QfPOlckGaS6hEck7w;info=<https://biloxi.example.org \
/biloxi.cert>;alg=ES256;ppt="pci"
4.2. Verification Service Behavior
RFC 8224 [RFC8224] Section 6.2 Step 5 requires that specifications
defining "ppt" values describe any additional verifier behavior. The
behavior specified for the "pci" value of "ppt" is as follows. The
verification service MUST extract the value associated with the "pci"
key in a PASSPorT with a "ppt" value of "pci". If the signature
validates, then the verification service can use the value of the
"pci" claim as validation that P-Charge-Info in the received request
is authentic. The verifier MUST also ensure that the generator of
Identity header is authorized to declare the value used for P-Charge-
Info as the party to be charged. How this can be achieved is out of
the scope of this specification.
4.3. Other Behavior
An entity dropping P-Charge-Info MUST drop the corresponding Identity
header with "ppt" parameter value of "pci".
5. IANA Considerations
This specification requests that the IANA add a new claim to the JSON
Web Token Claims registry as defined in RFC 7519 [RFC7519].
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Claim Name: "pci"
Claim Description: Party to be charged for a session
Change Controller: IESG
Specification Document(s): [RFCThis]
6. Security Considerations
This specification describes a security feature, and is primarily
concerned with increasing security for information regarding the
party to be charged for a real time session.
A malicious entity may add a P-Charge-Info value and a corresponding
Identity header for charge abuse. This would be detected either
because the signature validation fails or because the malicious
entity does not have authority to declare the value of P-Charge-Info
as the party to be charged.
A malicious entity may drop the P-Charge-Info and the corresponding
Identity header. This would cause infoirmation about the actual
party to cherge not being present for a receiver entity which
otherwise would use it for billing purposes. One way to avoid this
type of attack would be, for example, to enforce presence of P-
Charge-Info header by the billing entity and reject the session if
there is none. This check may be performed only for certain sessions
based on origination and/or destination identity for the call.
7. Acknowledgements
8. 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>.
[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>.
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[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>.
Author's Address
Tolga Asveren
Ribbon Communications
Freehold, NJ 07728
USA
Email: tasveren@rbbn.com
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