rspamd 3.11.1's milter_headers skips its verdict routines - removes none
of the sender's X-Spamd-Result / X-Rspamd-Action, adds none - for a client
it counts as local (loopback, a unix socket, local_addrs: the private
ranges) or one that authenticated (skip_local, skip_authenticated, both on
by default; milter_headers.lua skip_wanted(), lua_ip.c lua_ip_is_local()).
The custom routine that signs X-SelfPost-Filter is never put through
skip_wanted(), so it signed the sender's own verdict, and Inbound > Log
showed it as rspamd's. Every sender is private when Docker's proxy relays
port 25 from the bridge gateway. Both options set to false.
Tried 2026-10-14 in a throwaway rspamd/rspamd:3.11.1-3 on the test server
(rspamc --ucl, a message carrying its own verdict headers): old config,
from 10.0.0.5 and as an authenticated user, the milter reply removed and
added neither and added the signature; new config, both removed and
rspamd's own added, as from 203.0.113.9.
Also: the sender rules take the envelope only (extract_from = "smtp"; by
default a bounce's From: header is used - tried: a bounce whose From:
domain is denied was refused before, is not now; a denied sender is
refused either way); the image pinned to 3.11.1-3, the build read (3.11 and
3.11.1 move with each rebuild); the prefilter lines no longer read go.
architecture.md and security.md say so. Assumptions C-R7, B-R1, C-R4,
C-R12, C-R5.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Comments only, no behaviour changed. Each main.cf/master.cf parameter the
build sets, the wrapper's and the reload hook's reliance on Postfix 3.7.11
(postfix-script, master.5, postconf.5, cleanup_init.c, smtpd_peer.c,
README_FILES), supervisor 4.2.5 (process.py, options.py, events.rst),
logrotate 3.21.0, OpenDKIM's config, Cyrus SASL's sasldb, rspamd 3.11.1
(milter_headers.lua, multimap, the map watcher), Docker Compose, CoreDNS
and certbot now say where that is written. Measurements already there stay
measurements ("date not recorded" where none was); hand-composed fixtures
say so.
Contradictions left for their own commits: C-P31 cleanup's size limit,
C-P42 master outside supervisor's signal, C-V5/V6 startsecs, C-V10,
C-S3/Q3 sasldb written in place, C-Q4/A1 certbot's symlinks, C-R7 rspamd
skips local clients but the signature routine does not, C-P8, C-R4, C-R12,
C-M7, C-E2, C-K8/K9, C-D1.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The routine kept the key after its first read. SelfPost makes a new key
when the file is lost or damaged, or a backup brings back another, and
rspamd would then have gone on signing with the old one - every verdict
unrecorded - until someone restarted the sidecar. The file is one short
line; reading it per message costs nothing worth keeping a copy for.
The guide says what never needs doing: nothing of rspamd's is cleared
after a change of the lists or the key; a restart is for a change of
its own configuration only.
Prompted by the owner's question whether rspamd's cache needs clearing
(2026-10-12).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Closes what the security review left as an accepted risk: with the
spam filter down - it is attached fail-open - nothing removes verdict
headers a sender wrote himself, and the inbound journal recorded his
verdict as the filter's. The owner asked whether rspamd could add a
header that proves the others are ours (2026-10-12) and agreed to a
signature: a fixed mark could be written by a sender as easily as the
verdict.
- inbound.FilterKey: a key of 32 random bytes, 64 hex characters, in
/data/antispam/filter.key, made on the first start with the relay
on. 0644 like the list files beside it: the filter is another user
in another container.
- deploy/antispam/rspamd/milter_headers.conf: a custom routine reads
the key through the directory the sidecar already mounts and adds
X-SelfPost-Filter, the HMAC-SHA256 of the message's queue id, hex;
a header of that name from the sender is removed.
- internal/milter/inbound.go: the verdict headers are kept as they
are read, and at end-of-message - when the queue id is known - they
count only if the signature fits (FilterSignature, hmac.Equal). No
key, no queue id, no signature or a wrong one: the row is that of
mail nobody judged (accept, selfpost, no detail).
The signature goes on to the upstream with the mail and is of no use
there: it fits one queue id.
Tried in a throwaway rspamd 3.11 container on the test server before
the Go side was written: the routine loads, signs
(2aa1ca6d... for key 0123...cdef and queue id 4A1B2C3D5E, the value
python's hmac gives and TestFilterSignatureIsWhatTheFilterWrites
pins), removes a sender's header of the same name, and adds nothing
without a queue id.
Tests: signed, unsigned, made-up, another message's, another key's,
the sender's followed by the real one, the next message on the
connection, no queue id; the key made once, read after, replaced when
damaged, left alone by the lists. e2e: filter.key is there, 644, 65
bytes.
docs/security.md: the accepted risk is replaced by a narrower one (the
key is readable on the host); Mail path describes the signature.
Checked on the test server, uncommitted tree: go vet ./... ok,
go test ./... ok (22 packages), make e2e ok.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Step 3/12 of docs/plans/inbound-antispam-panel.md.
The panel serves a second milter while the inbound relay is on
(internal/milter/inbound.go, socket INBOUND_JOURNAL_MILTER_SOCKET,
default /run/selfpost/inbound-journal.sock). build/postfix-config.sh
puts it last on port 25, after the optional antispam milter, with
default_action=accept; postfix-wrapper.sh waits for its socket. At
end-of-message it writes one inbound_spam_log row per recipient at an
inbound domain - other port-25 recipients (DMARC report addresses) get
none - and always accepts. With a filter attached it reads the verdict
from X-Rspamd-Action and X-Spamd-Result (action, score, up to six
weighted symbols, only what the patterns recognise, 255 bytes); without
one those headers are the sender's and are not read. The plan named
X-Rspamd-Score, which rspamd does not have.
The antispam compose fragment mounts rspamd/milter_headers.conf into
the sidecar so that it adds the two headers (checked in rspamd 3.11:
both routines exist and remove a sender's own headers of those names).
Store: InsertInboundSpam, IsInboundDomain.
Checked on the test server, uncommitted tree: go vet ./... ok,
go test ./... ok (22 packages), make e2e ok - the relayed message of
inbound_relay_delivers_and_refuses has its journal row (accept by
selfpost) and the DMARC report sent through the same listener has none.
Not yet seen in a real run: a verdict written by rspamd reaching this
milter. The e2e stand has no filter, and the test server's only inbound
domain has no upstream, so it accepts no mail.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
mixandClaude Opus 5.5