Subject: [stir] [Technical Errata Reported] RFC8224 (5391)

From: RFC Errata System <[email-masked]>
Date: Thu, 14 Jun 2018 13:15:41 -0700 (PDT)

The following errata report has been submitted for RFC8224,
"Authenticated Identity Management in the Session Initiation Protocol (SIP)".

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You may review the report below and at:
http://www.rfc-editor.org/errata/eid5391

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Type: Technical
Reported by: Invalid content for "iat" <[email-masked]>

Section: 4.1

Original Text
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      Third, the JSON key "iat" MUST appear.  The authentication service
      SHOULD set the value of "iat" to an encoding of the value of the
      SIP Date header field as a JSON NumericDate (as UNIX time, per
      [RFC7519], Section 2), though an authentication service MAY set
      the value of "iat" to its own current clock time.  If the
      authentication service uses its own clock time, then the use of
      the full form of PASSporT is REQUIRED.  In either case, the
      authentication service MUST NOT generate a PASSporT for a SIP
      request if the Date header is outside of its local policy for
      freshness (sixty seconds is RECOMMENDED).

Corrected Text
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“4.1 PASSPorT Construction”:

Third, the JSON key "iat" MUST appear. 
The authentication service SHOULD set the 
value of "iat" to an encoding of the value of 
JWT generation as a JSON NumericDate 
(as UNIX time, per [RFC7519], Section 2).

Notes
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RFC7519 JSON Web Token (JWT)
 
4.1.6.  "iat" (Issued At) Claim
 
   The "iat" (issued at) claim identifies the time at which the JWT was
   issued.  This claim can be used to determine the age of the JWT.  Its
   value MUST be a number containing a NumericDate value.  Use of this
   claim is OPTIONAL.
 
This text clearly states that “iat” is for the generation time of JWS. 

One may argue that origination of SIP dialog - on which Date header content is based - and JWT generation times would be very close to each other but this is not always true. JWT, for example, can be added only at administrative boundaries and a session may have started long before that,e .g. it involves user interaction with an IVR for announcement/PIN verification. 

It should be noted that populating "iat" with JWT issuance time makes use of complete form mandatory. So, if this errata is accepted, there probably would be a need to remove compact form as an option.

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RFC8224 (draft-ietf-stir-rfc4474bis-16)
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Title               : Authenticated Identity Management in the Session Initiation Protocol (SIP)
Publication Date    : February 2018
Author(s)           : J. Peterson, C. Jennings, E. Rescorla, C. Wendt
Category            : PROPOSED STANDARD
Source              : Secure Telephone Identity Revisited
Area                : Applications and Real-Time
Stream              : IETF
Verifying Party     : IESG