Persona Assertion Token
draft-ietf-stir-passport-07
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8225.
|
|
|---|---|---|---|
| Authors | Chris Wendt , Jon Peterson | ||
| Last updated | 2016-09-09 | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 8225 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-stir-passport-07
quot;:"021ACC5427ABEB9C533F3E4B652E7D463F5442CD54
F17A03A27DF9B07F4619B2"
},
{
"alg":"sha-256",
"dig":"4AADB9B13F82183B540212DF3E5D496B19E57C
AB3E4B652E7D463F5442CD54F1"
}
],
"orig":{"tn":"12155551212"}
}
5. PASSporT Signature
The signature of the PASSporT is created as specified by JWS
[RFC7515] Section 5.1 Steps 1 through 6. PASSporT MUST use the JWS
Protected Header. For the JWS Payload and the JWS Protected Header,
the lexicographic ordering and white space rules described above, and
JSON serialization rules in Section 6 of this document MUST be
followed.
Appendix A of this document has a detailed example of how to follow
the steps to create the JWS Signature.
JWS [RFC7515] Section 5.1 Step 7 JWS JSON serialization is not
supported for PASSporT.
JWS [RFC7515] Section 5.1 Step 8 describes the method to create the
final JWS Compact Serialization form of the PASSporT Token.
6. Extending PASSporT
PASSporT includes the bare minimum set of claims needed to securely
assert the originating identity and support the secure properties
discussed in various parts of this document. JWT supports a straight
forward way to add additional claims by simply adding new claim key
pairs. PASSporT can be extended beyond the defined base set of
claims to represent other information requiring assertion or
validation beyond the originating identity itself as needed.
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6.1. "ppt" (PASSporT) header parameter
For extension of the base set of claims defined in this document, a
new JWS header parameter "ppt" MUST be used with a unique string.
Any PASSporT extension should be defined in a specification
describing the PASSporT extension and the string used in the "ppt"
header string that defines any new claims that would extend the base
set of claims of PASSporT.
An example header with a PASSporT extension type of "foo" is as
follows:
{
"alg":"ES256",
"ppt":"foo",
"typ":"passport",
"x5u":"https://tel.example.org/passport.cer"
}
6.2. Extended PASSporT Claims
Specifications that define extensions to the PASSporT mechanism MUST
explicitly specify what claims they include beyond the base set of
claims from this document, the order in which they will appear, and
any further information necessary to implement the extension. All
extensions MUST include the baseline JWT elements specified in
Section 3; claims may only be appended to the claims object
specified; they can never be removed or re-ordered. Specifying new
claims follows the baseline JWT procedures ([RFC7519] Section 10.1).
Understanding an extension or new claims defined by the extension on
the destination verification of the PASSporT token is optional. The
creator of a PASSporT object cannot assume that destination systems
will understand any given extension. Verification of PASSporT tokens
by destination systems that do support an extension may then trigger
appropriate application-level behavior in the presence of an
extension; authors of extensions should provide appropriate
extension-specific guidance to application developers on this point.
An example set of extended claims, extending the first example in
Section 4.1.2.4. using "bar" as the newly defined claim would be as
follows:
{
"bar":"beyond all recognition"
"dest":{"uri":["sip:alice@example.com"]},
"iat":"1443208345",
"orig":{"tn":"12155551212"}
}
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7. Deterministic JSON Serialization
JSON, as a canonical format, can include spaces, line breaks and key
value pairs can occur in any order and therefore makes it, from a
string format, non-deterministic. In order to make the digital
signature verification work deterministically, the JSON
representation of the PASSporT Header and Claims, particularly if
PASSporT is used across multiple signaling environments, specifically
the JWS Protected Header object and JWS Payload object MUST be
computed as follows.
The JSON object MUST follow the rules for the construction of the
thumbprint of a JSON Web Key (JWK) as defined in [RFC7638] Section 3
Step 1 only. Step 2 MUST NOT be performed; as noted in JWK this is
still a legal JWK object.
The PASSporT header and claim direct members MUST follow the
lexicographical ordering rules. Any top level JSON members that
contain JSON objects or arrays, such as "dest" or "mky" MUST follow
their own lexicographical ordering and whitespace and line break
rules for the sub-elements. This includes any header or claims
defined in future specifications using PASSporT.
7.1. Example PASSport deterministic JSON form
This section demonstrate the deterministic JSON serialization for the
example PASSporT Payload shown in Section 4.2.2.
The initial JSON object is shown here:
{
"dest":{"uri":["sip:alice@example.com"]},
"orig":{"tn":"12155551212"}
"iat":"1443208345",
"mky":[
{
"alg":"sha-256",
"dig":"021ACC5427ABEB9C533F3E4B652E7D463F5442CD54
F17A03A27DF9B07F4619B2"
},
{
"alg":"sha-256",
"dig":"4AADB9B13F82183B540212DF3E5D496B19E57C
AB3E4B652E7D463F5442CD54F1"
}
],
}
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The parent members of the JSON object are as follows:
o "dest"
o "orig"
o "iat"
o "mky"
Their lexicographic order is:
o "dest"
o "iat"
o "mky"
o "orig"
The final constructed deterministic JSON serialization
representation, with whitespace and line breaks removed, (with line
breaks used for display purposes only) is:
{"dest":{"uri":["sip:alice@example.com"],"iat":1443208345,"mky":
[{"alg":"sha-256","dig":"021ACC5427ABEB9C533F3E4B652E7D463F5442
CD54F17A03A27DF9B07F4619B2"},{"alg":"sha-256","dig":"4AADB9B13F
82183B540212DF3E5D496B19E57CAB3E4B652E7D463F5442CD54F1"}],
"orig":{"tn":"12155551212"}}
8. Security Considerations
8.1. Avoidance of replay and cut and paste attacks
There are a number of security considerations for use of the token
for avoidance of replay and cut and paste attacks. PASSporT tokens
should be sent with other application level protocol information
(e.g. for SIP an INVITE as defined in [RFC3261]). In order to make
the token signature unique to a specific origination of personal
communications there should be a link between various information
provided in the token and information provided by the application
level protocol information. This uniqueness specified using the
following two claims:
o 'iat' claim should correspond to a date/time the message was
originated. It should also be within a relative time that is
reasonable for clock drift and transmission time characteristics
associated with the application using the PASSporT token.
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Therefore, validation of the token should consider date and time
correlation, which could be influenced by signaling protocol
specific use and network time differences.
o 'dest' claim is included to prevent the valid re-use of a
previously originated message to send to another destination
party.
8.2. Solution Considerations
The use of PASSporT tokens based on the validation of the digital
signature and the associated certificate requires consideration of
the authentication and authority or reputation of the signer to
attest to the identity being asserted. It should be recognized that
the use of this token should not, in it's own right, be considered a
full solution for absolute non-repudiation of the identity being
asserted. It can and often is the case that the end user that the
identity represents and signer are not one in the same. However,
applications that use PASSporT should ensure the signer is in an
authoritative position to represent the user and authenticate the
user onto the communications network and should be the responsible
party for protecting the destination party from potential identity
spoofing in addition to other abuse of the communications network
outside of PASSporT.
8.3. Privacy Considerations
Because PASSporT explicitly includes claims of identifiers of parties
involved in communications, date and times, and potentially other
call detail, care should be taken outside of traditional protected or
private telephony communications paths where there may be concerns
about exposing information to either unintended or illegitimate
actors. These identifiers are often exposed through many
communications signaling protocols as of today, but appropriate
precautions should be taken.
9. IANA Considerations
9.1. Media Type Registration
9.1.1. Media Type Registry Contents Additions Requested
This section registers the "application/passport" media type
[RFC2046] in the "Media Types" registry in the manner described in
[RFC6838], which can be used to indicate that the content is a
PASSporT defined JWT and JWS.
o Type name: application
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o Subtype name: passport
o Required parameters: n/a
o Optional parameters: n/a
o Encoding considerations: 8bit; application/passport values outside
the US-ASCII range are encoded using percent encoding as described
in section 2.1 of RFC 3986 (some values may be the empty string),
each separated from the next by a single period ('.') character.
o Security considerations: See the Security Considerations section
of RFC 7515.
o Interoperability considerations: n/a
o Published specification: draft-ietf-stir-passport-05
o Applications that use this media type: STIR and other applications
that require identity related assertion
o Fragment identifier considerations: n/a
o Additional information:
* Magic number(s): n/a
* File extension(s): n/a
* Macintosh file type code(s): n/a
o Person and email address to contact for further information: Chris
Wendt, chris-ietf@chriswendt.net
o Intended usage: COMMON
o Restrictions on usage: none
o Author: Chris Wendt, chris-ietf@chriswendt.net
o Change Controller: IESG
o Provisional registration? No
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9.2. JSON Web Token Claims Registration
9.2.1. Registry Contents Additions Requested
o Claim Name: "orig"
o Claim Description: Originating Identity String
o Change Controller: IESG
o Specification Document(s): Section 3.2 of draft-ietf-stir-
passport-05
o Claim Name: "dest"
o Claim Description: Destination Identity String
o Change Controller: IESG
o Specification Document(s): Section 3.2 of draft-ietf-stir-
passport-05
o Claim Name: "mky"
o Claim Description: Media Key Fingerprint String
o Change Controller: IESG
o Specification Document(s): Section 3.2 of draft-ietf-stir-
passport-05
10. Acknowledgements
Particular thanks to members of the ATIS and SIP Forum NNI Task Group
including Jim McEchern, Martin Dolly, Richard Shockey, John Barnhill,
Christer Holmberg, Victor Pascual Avila, Mary Barnes, Eric Burger for
their review, ideas, and contributions also thanks to Henning
Schulzrinne, Russ Housley, Alan Johnston, Richard Barnes, Mark
Miller, Ted Hardie, Dave Crocker, Robert Sparks for valuable feedback
on the technical and security aspects of the document. Additional
thanks to Harsha Bellur for assistance in coding the example tokens.
11. References
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11.1. Normative References
[I-D.ietf-stir-rfc4474bis]
Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
"Authenticated Identity Management in the Session
Initiation Protocol (SIP)", draft-ietf-stir-rfc4474bis-12
(work in progress), August 2016.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<http://www.rfc-editor.org/info/rfc2046>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>.
[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572,
DOI 10.17487/RFC4572, July 2006,
<http://www.rfc-editor.org/info/rfc4572>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<http://www.rfc-editor.org/info/rfc6838>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://www.rfc-editor.org/info/rfc7515>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<http://www.rfc-editor.org/info/rfc7518>.
[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>.
[RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
2015, <http://www.rfc-editor.org/info/rfc7638>.
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11.2. Informative References
[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>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<http://www.rfc-editor.org/info/rfc5280>.
[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>.
Appendix A. Example PASSporT JWS Serialization and Signature
For PASSporT, there will always be a JWS with the following members:
o "protected", with the value BASE64URL(UTF8(JWS Protected Header))
o "payload", with the value BASE64URL (JWS Payload)
o "signature", with the value BASE64URL(JWS Signature)
This example will follow the steps in JWS [RFC7515] Section 5.1,
steps 1-6 and 8 and incorporates the additional serialization steps
required for PASSporT.
Step 1 for JWS references the JWS Payload, an example PASSporT
Payload is as follows:
{
"dest":{"uri":["sip:alice@example.com"]}
"iat":"1443208345",
"orig":{"tn":"12155551212"}
}
This would be serialized to the form (with line break used for
display purposes only):
{"dest":{"uri":["sip:alice@example.com"]},"iat":"1443208345",
"orig":{"tn":"12155551212"}}
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Step 2 Computes the BASE64URL(JWS Payload) producing this value (with
line break used for display purposes only):
eyJkZXN0Ijp7InVyaSI6WyJzaXA6YWxpY2VAZXhhbXBsZS5jb20iXX0sImlhd
CI6IjE0NDMyMDgzNDUiLCJvcmlnIjp7InRuIjoiMTIxNTU1NTEyMTIifX0
For Step 3, an example PASSporT Protected Header comprising the JOSE
Header is as follows:
{
"typ":"passport",
"alg":"ES256",
"x5u":"https://cert.example.org/passport.cer"
}
This would be serialized to the form (with line break used for
display purposes only):
{"alg":"ES256","typ":"passport","x5u":"https://cert.example.org/
passport.cer"}
Step 4 Performs the BASE64URL(UTF8(JWS Protected Header)) operation
and encoding produces this value (with line break used for display
purposes only):
eyJhbGciOiJFUzI1NiIsInR5cCI6InBhc3Nwb3J0IiwieDV1IjoiaHR0cHM6Ly9j
ZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNlciJ9
Step 5 and Step 6 performs the computation of the digital signature
of the PASSporT Signing Input ASCII(BASE64URL(UTF8(JWS Protected
Header)) || '.' || BASE64URL(JWS Payload)) using ES256 as the
algorithm and the BASE64URL(JWS Signature).
rq3pjT1hoRwakEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYso
jNCpTzO3QfPOlckGaS6hEck7w
Step 8 describes how to create the final PASSporT token,
concatenating the values in the order Header.Payload.Signature with
period ('.') characters. For the above example values this would
produce the following (with line breaks between period used for
readability purposes only):
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eyJhbGciOiJFUzI1NiIsInR5cCI6InBhc3Nwb3J0IiwieDV1IjoiaHR0cHM6Ly
9jZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNlciJ9
.
eyJkZXN0Ijp7InVyaSI6WyJzaXA6YWxpY2VAZXhhbXBsZS5jb20iXX0sImlhd
CI6IjE0NDMyMDgzNDUiLCJvcmlnIjp7InRuIjoiMTIxNTU1NTEyMTIifX0
.
rq3pjT1hoRwakEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYso
jNCpTzO3QfPOlckGaS6hEck7w
A.1. X.509 Private Key Certificate for Example
-----BEGIN EC PRIVATE KEY-----
MHcCAQEEIFeZ1R208QCvcu5GuYyMfG4W7sH4m99/7eHSDLpdYllFoAoGCCqGSM49
AwEHoUQDQgAE8HNbQd/TmvCKwPKHkMF9fScavGeH78YTU8qLS8I5HLHSSmlATLcs
lQMhNC/OhlWBYC626nIlo7XeebYS7Sb37g==
-----END EC PRIVATE KEY-----
A.2. X.509 Public Key Certificate for Example
-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE8HNbQd/TmvCKwPKHkMF9fScavGeH
78YTU8qLS8I5HLHSSmlATLcslQMhNC/OhlWBYC626nIlo7XeebYS7Sb37g==
-----END PUBLIC KEY-----
Authors' Addresses
Chris Wendt
Comcast
One Comcast Center
Philadelphia, PA 19103
USA
Email: chris-ietf@chriswendt.net
Jon Peterson
Neustar Inc.
1800 Sutter St Suite 570
Concord, CA 94520
US
Email: jon.peterson@neustar.biz
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