Security review of the DMARC report path (Fable, 2026-10-11), which ran
for the first time in 2.0.0. No Critical or High finding. Fixed:
- Medium: a report was bounded only as 8 MiB of XML - some 160 000
records or one name of megabytes, all of it rows and table cells. At
most 5 000 records (more is ErrRejected, dropped), text fields cut to
255 bytes on a character boundary, a record's count capped.
- Medium: the cap of 500 reports was for the whole server, so a stranger
filing under one domain's address evicted every other domain's
reports. PruneDMARCReports counts per domain.
- Low: the pipe service ran up to default_process_limit (100) commands
at once against the panel's database; maxproc is 1.
- Low: the reason logged for a dropped message carried the sender's
bytes (header line, zip entry name) as they came; cut to 200 bytes and
reduced to printable ASCII, zip entry names quoted.
- Low: SELFPOST_DATA_DIR / SELFPOST_DB_PATH with whitespace or "$" would
reach the command through export_environment as another path; refused
at start when DMARC ingest is on.
Left as they are, told to the owner: the parse-failure count is a
lifetime figure shown under "This week"; a report larger than the
command reads is dropped as unreadable; nested multipart is not searched.
The hub's Retention line follows the design commit before this one.
security.md: the review, and the accepted-risk entry says what a
stranger can and cannot do now. The roadmap no longer calls the review
pending.
go vet ./cmd/... ./internal/dmarc/ ./internal/store/: ok
go test ./cmd/... ./internal/dmarc/ ./internal/store/ ./internal/web/...: ok
make e2e on the test server (with the port-25 scenarios of the next
commit): ok
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The first DMARC report to reach the test server (Google, 2026-10-11
09:41 UTC) was accepted on port 25 and then sat in the queue:
postfix/pipe: fatal: missing user= command-line attribute
postfix/qmgr: warning: private/dmarc-ingest socket: malformed response
Three things stood between an accepted report and the panel, all since
the feature shipped in 1.7.0 - no report had ever been delivered:
- The service was addressed as dmarc-ingest/unix-pipe. Its type is unix:
postconf -P answered "unmatched service_name/type" for flags=, user=
and argv= (the warnings in the container log at every start), which
are arguments of pipe(8) anyway and not -o parameters, and the service
stayed a bare "pipe". For the same reason postconf -MX never removed
it. It is dmarc-ingest/unix now, with the arguments in the service line.
- pipe(8) gives the command export_environment and nothing else, so the
command would have refused to run: it reads DMARC_REPORTS_ENABLE (and
the data directory, when it is not the default) from the environment.
Those are now named in export_environment.
- The command took the recipient from RECIPIENT, which local(8) sets and
pipe(8) does not. With no recipient the check that a report came to the
address of its own domain is skipped. It is now ${recipient} in argv,
one recipient per run.
When DMARC ingest is off the service and both parameters are removed.
e2e: every port-25 combination now asks Postfix for the service and the
two parameters (postconf -M / -h), and for their absence when ingest is
off - which is how the wrong type was found. make e2e on the test
server: ok. go test ./cmd/panel/ ./internal/dmarc/ ./internal/postfix/:
ok.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
mixandClaude Opus 5.5