[OAUTH-WG] Re: [Technical Errata Reported] RFC7519 (8060)

[Brian Campbell <[e-mail]>]

That is a good catch of an inconsistency in JWT/RFC7519 that is deserving
of errata. Note however that JWE/RFC7516 says that the "rules about
handling Header Parameters that are not understood by the implementation
are also the same [as JWS]"* so the correcting errata text should probably
be more generally applicable to all JWTs.

* see https://datatracker.ietf.org/doc/html/rfc7516#section-4

On Wed, Jul 31, 2024 at 7:27 AM RFC Errata System <[e-mail]>
wrote:

> The following errata report has been submitted for RFC7519,
> "JSON Web Token (JWT)".
>
> --------------------------------------
> You may review the report below and at:
> https://www.rfc-editor.org/errata/eid8060
>
> --------------------------------------
> Type: Technical
> Reported by: Pieter Kasselman <[e-mail]>
>
> Section: 7.2
>
> Original Text
> -------------
>    5.   Verify that the resulting JOSE Header includes only parameters
>         and values whose syntax and semantics are both understood and
>         supported or that are specified as being ignored when not
>         understood.
>
> Corrected Text
> --------------
>    5.   Verify that the resulting JOSE Header includes only parameters
>         and values whose syntax and semantics are both understood and
>         supported or that are specified as being ignored when not
>         understood. If the JWT is a JWS, the steps specified in
>         RFC7515 takes precedence when validating JOSE Header parameters.
>
> Notes
> -----
> Validation step 5 in section 7.2 of RFC 7519 states that header parameters
> should only be ignored if they are explicitly specified as needing to be
> ignored.
>
> This is contrary to step 7 in section 7.2 which requires that the
> processing rules of RFC 1515 be used if the JWT is a JWS (defined in RFC
> 1515). RFC 7515 does not include any special provisions for only ignoring
> header parameters if they are specified as being ignored, but instead
> requires all header parameters to be ignored if they are not understood
> (repeated below for convenience).
>
> "Unless listed as a critical Header Parameter, per
>    Section 4.1.11, all Header Parameters not defined by this
>    specification MUST be ignored when not understood."
>
> A discussion with the authors at IETF 120 confirmed that all header
> parameters that are not understood must be ignored.
>
> The proposed errata aims to clarify that if the JWT is a JWS, the
> processing rules of RFC 7151 should apply (including ignoring header
> parameters that are not understood). This is consistent with point 7.2,
> which requires that RFC 7515 [JWS] rules applies and avoids the impression
> that a new requirement on when parameters are ignored is being introduced
> in (i.e. the need to be explicitly defined as needing to be ignored).
>
> Instructions:
> -------------
> This erratum is currently posted as "Reported". (If it is spam, it
> will be removed shortly by the RFC Production Center.) Please
> use "Reply All" to discuss whether it should be verified or
> rejected. When a decision is reached, the verifying party
> will log in to change the status and edit the report, if necessary.
>
> --------------------------------------
> RFC7519 (draft-ietf-oauth-json-web-token-32)
> --------------------------------------
> Title               : JSON Web Token (JWT)
> Publication Date    : May 2015
> Author(s)           : M. Jones, J. Bradley, N. Sakimura
> Category            : PROPOSED STANDARD
> Source              : Web Authorization Protocol
> Stream              : IETF
> Verifying Party     : IESG
>
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>

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