Security audit 2026-10-17, M6 and M8 (nits), stage 6.
M6: Content-Type, MIME-Version and Message-ID were not in h= (as in
OpenDKIM's default list): a relay could change a MIME boundary or the type
and the signature still verified. They are signed when present; Message-ID
is not over-signed, since cleanup adds one a message lacks after the
milters and an absent name in h= would refuse it.
M8: a header line over smtp_line_length_limit (998) is broken by Postfix's
smtp client after signing and the signature fails silently; only body
lines were logged. longHeaderLine names the header, once per message, in
the same words.
Tests: TestSignLinesCoverTheMIMEHeadersAndLongHeaderLinesAreNamed; the h=
expectations gain Message-ID; e2e dkim_shapes expects content-type: in h=
(and the receiver's verification over it). Docs: security.md,
architecture.md, guide; CHANGELOG.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
mixandClaude Opus 5.5
5c5f49bad1