[Ietf-dkim] Fwd: Re: [..] Recommendation for dkim signing

[Steffen Nurpmeso <[e-mail]>]

--- Forwarded from Steffen Nurpmeso <[e-mail]> ---
Date: Wed, 06 Mar 2024 22:49:48 +0100
Author: Steffen Nurpmeso <[e-mail]>
From: Steffen Nurpmeso <[e-mail]>
...
Subject: Re: [pfx] Recommendation for dkim signing
Message-ID: <20240306214948.V5gSjSiU@steffen%sdaoden.eu>
...

...
So now that i have DKIM myself i tested.
And *no* verification software i can reach actually supports
Ed25519-sha256 as of RFC 8463 from September 2018!
It is even *worse* than that.

  - Google: at least reaches out to the RSA signature and verifies
    that, it ignores the other one saying "no key".

  - Microsoft: fails the DKIM test if a RFC 8463 signature is
    present, no matter whether first or last!!!
    Is this *really* true?  That is really bad.

  - The software this list uses (rspamd i think): fails if the
    Ed25519 signature is first, aka does not reach out.  (Which it
    should, says DKIM, does it.  The DKIM standard is
    *fantastic*!)  It at least succeeds if the RSA is first.

What a mess.  Even though explicitly envisioned in the DKIM
standard, it seems to me one cannot simply create two signatures,
as i wanted to do.  (For a while, at least; until i see Ed is
supported anywhere.  I had no plan, actually.)

So as of today DKIM interoperability seems to mean:

  - Place a single signature.

  - It must be RSA-sha256.

RFC 6376 surely would have deserved something better.

  ...
 -- End forward <20240306214948.V5gSjSiU@steffen%sdaoden.eu>

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)