[openpgp] Re: New Version Notification for draft-gallagher-email-unobtrusive-signatures-00.txt

[Andrew Gallagher <[e-mail]>]

On 14 May 2025, at 14:35, Stephen Farrell <[e-mail]> wrote:
> 
> On 14/05/2025 14:22, Andrew Gallagher wrote:
>> The only caveat is whether DKIM’s relaxed/relaxed canonicalisation
>> allows a DKIM signature over a slightly mangled message (e.g.
>> trailing whitespace) to validate when an E2E signature would not -
>> but the message canonicalisation guidance in section 5.4 of the
>> current draft is designed to avoid this.
> 
> I don't disagree, but there's also the potential that
> the way you're spec'ing multipart/mixed here causes the
> DKIM2 algebra to get a wrong answer. I guess that also
> shouldn't happen, but it's a thing to be checked as
> that DKIM2 algebra is developed.

We'll definitely keep an eye on it, although DKIM should be ignorant of MIME structure. That said, one issue that I have encountered is that some MUAs (such as Apple Mail) create MIME parts with spurious extra leading newlines in the preamble, and some MTAs (I never pinpointed the culprits) silently strip the redundant newlines in transit. However, this also breaks DKIM signatures over the same body, even under the proposed DKIM2 guidance...

A