On Thu 30/May/2024 19:19:16 +0200 Murray S. Kucherawy wrote:
On Thu, May 30, 2024 at 9:13 AM Alessandro Vesely <[email protected]> wrote:
z= saves all fields, which would be too much in most cases. Moreover,
doing so suggests treating all fields as a whole, rather than dealing with
each one's peculiarity. >
That's not what the RFC says.
Most implementations put there all signed fields. OpenDKIM also "skip" fields.
Undoing transformations is not a diagnostic operation. For example, Mailman 3
is qp-encoding the Subject:
X-Mailman-Version: 3.3.9rc4
Precedence: list
Subject: =?utf-8?q?=5BIetf-dkim=5D_Re=3A_Manipulation_of_signed_messages?=
That way I cannot verify Gmail's signatures any more. Diagnostics is only
needed to get the culprit, so as to better the heuristics...
Of course, if an Original- field is tampered with the original signature
won't verify after replacing it, just like if you altered z=. But then,
reverting without cooperation is not the same as doing it with active
opposition. Why would someone alter Original- fields? A mediator wanting
to disrupt the possibility to reverse had better removing the signature
directly. >
Space munging applied to all fields, for example, is enough to break this
scheme. "z=", by contrast, is immune to such mutations, because it's
encoded.
Right. However, Mailman re-folds header fields it writes from memory, so if
canonicalization is not relaxed the verification fails anyway. z= doesn't
include itself.
Best
Ale
--
_______________________________________________
Ietf-dkim mailing list -- [email protected]
To unsubscribe send an email to [email protected]
