fix: pin logrotate config mode in image and fail loud on bad permissions

COPY --chmod makes /etc/logrotate.d/mail 0644 regardless of build context
file modes (Windows tar sync). logrotate-loop preflight exits non-zero when
logrotate would ignore the config. E2e covers mode, forced rotation, and a
group-writable context build.

Co-Authored-By: Composer 2.5 <noreply@cursor.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

CHANGELOG.md

@@ -5,6 +5,15 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); version
 
 ## [Unreleased]
 
+### Fixed
+
+- image: `mail.log` rotation no longer silently stops when the build context
+  ships `logrotate-mail.conf` with group/other write bits (common after a
+  Windows checkout sync). Runtime `COPY --chmod` pins config and script modes
+  in the Dockerfile; `logrotate-loop.sh` refuses a config logrotate would
+  ignore. E2e checks mode `644`, forced rotation, and a group-writable context
+  build.
+
 ## [1.2.2] - 2026-08-12
 
 Status page layout after 1.2.1: paired cards in a wide column, denser machine

build/Dockerfile

@@ -88,20 +88,20 @@ COPY --from=build /out/selfpost-backup /usr/local/bin/selfpost-backup
 
 # Licence text shipped with the image (AGPL-3.0 conveyance). The panel also
 # serves the same text at /license from an embedded copy.
-COPY LICENSE NOTICE /usr/share/doc/selfpost/
+COPY --chmod=0644 LICENSE NOTICE /usr/share/doc/selfpost/
 
-COPY build/opendkim.conf /etc/opendkim.conf
-COPY build/logrotate-mail.conf /etc/logrotate.d/mail
-COPY build/postfix-wrapper.sh /usr/local/bin/postfix-wrapper.sh
-COPY build/postfix-config.sh /usr/local/bin/postfix-config.sh
-COPY build/postfix-cert-reload.sh /usr/local/bin/postfix-cert-reload.sh
-COPY build/logrotate-loop.sh /usr/local/bin/logrotate-loop.sh
-COPY build/crashexit.py /usr/local/bin/crashexit.py
-COPY build/entrypoint.sh /usr/local/bin/entrypoint.sh
-COPY build/supervisord.conf /etc/supervisor/supervisord.conf
-RUN chmod +x /usr/local/bin/postfix-wrapper.sh /usr/local/bin/postfix-config.sh \
-      /usr/local/bin/postfix-cert-reload.sh /usr/local/bin/logrotate-loop.sh \
-      /usr/local/bin/crashexit.py /usr/local/bin/entrypoint.sh
+# File modes are pinned here so a build context copied from a checkout without
+# POSIX permissions (e.g. Windows tar sync) cannot land group-writable config
+# that logrotate would silently ignore — see docs/plans/logrotate-mode.md.
+COPY --chmod=0644 build/opendkim.conf /etc/opendkim.conf
+COPY --chmod=0644 build/logrotate-mail.conf /etc/logrotate.d/mail
+COPY --chmod=0755 build/postfix-wrapper.sh /usr/local/bin/postfix-wrapper.sh
+COPY --chmod=0755 build/postfix-config.sh /usr/local/bin/postfix-config.sh
+COPY --chmod=0755 build/postfix-cert-reload.sh /usr/local/bin/postfix-cert-reload.sh
+COPY --chmod=0755 build/logrotate-loop.sh /usr/local/bin/logrotate-loop.sh
+COPY --chmod=0755 build/crashexit.py /usr/local/bin/crashexit.py
+COPY --chmod=0755 build/entrypoint.sh /usr/local/bin/entrypoint.sh
+COPY --chmod=0644 build/supervisord.conf /etc/supervisor/supervisord.conf
 
 # Published submission ports: 465 (smtps, primary) and 587 (submission, optional)
 # plus the panel on 8080. Outbound delivery dials remote MXs on 25 as a client,

build/logrotate-loop.sh

@@ -14,10 +14,49 @@
 # often than daily — polling merely bounds how late a legitimate rotation runs.
 set -eu
 
+CONFIG=/etc/logrotate.d/mail
 INTERVAL="${LOGROTATE_INTERVAL_SECONDS:-21600}"
 
+# logrotate refuses configs writable by group or others and exits 0 while
+# ignoring them — fail here so supervisord reports the fault.
+logrotate_config_ok() {
+	mode=$(stat -c '%a' "$CONFIG")
+	mode=${mode#0}
+	grp=$(( (mode / 10) % 10 ))
+	oth=$(( mode % 10 ))
+	case $grp in 2|3|6|7) return 1 ;; esac
+	case $oth in 2|3|6|7) return 1 ;; esac
+	return 0
+}
+
+logrotate_config_fatal() {
+	echo "logrotate-loop: refusing to run: $CONFIG mode $(stat -c '%a' "$CONFIG") is writable by group or others" >&2
+	exit 1
+}
+
+if ! logrotate_config_ok; then
+	logrotate_config_fatal
+fi
+
+run_logrotate() {
+	out=$(logrotate "$CONFIG" 2>&1) || {
+		echo "$out" >&2
+		return 1
+	}
+	case "$out" in
+		*Ignoring*|*Potentially\ dangerous\ mode*)
+			echo "$out" >&2
+			logrotate_config_fatal
+			;;
+	esac
+	return 0
+}
+
 while true; do
-	if logrotate /etc/logrotate.d/mail; then
+	if ! logrotate_config_ok; then
+		logrotate_config_fatal
+	fi
+	if run_logrotate; then
 		:
 	else
 		echo "logrotate-loop: logrotate failed, will retry after ${INTERVAL}s" >&2

build/supervisord.conf

@@ -104,8 +104,9 @@ stderr_logfile=/dev/stderr
 stderr_logfile_maxbytes=0
 
 ; Periodic logrotate for /data/log/mail.log (spec 9, 10: daily, 7-14 files kept
-; in the image). Runs as root so logrotate can read/rotate the log; never exits
-; non-zero, so it neither trips the crashexit listener nor needs restarting.
+; in the image). Runs as root so logrotate can read/rotate the log. Exits
+; non-zero when the config is group/other-writable (logrotate would ignore it
+; silently); autorestart surfaces BACKOFF on the Status page.
 [program:logrotate]
 command=/usr/local/bin/logrotate-loop.sh
 priority=400

docs/development.md

@@ -162,8 +162,10 @@ docker build -f build/Dockerfile -t selfpost:dev --build-arg VERSION=dev .
 ```
 
 The Dockerfile has a build stage (`go vet`, `go build` with `VERSION`) and a
-runtime stage (Debian + mail stack). See [architecture.md](architecture.md) §
-Image and processes.
+runtime stage (Debian + mail stack). Runtime config and scripts use `COPY
+--chmod` so file modes in the image do not depend on how the build context was
+synced (e.g. a Windows checkout widening permissions on `logrotate-mail.conf`).
+See [architecture.md](architecture.md) § Image and processes.
 
 ---
 

docs/plans/logrotate-mode.md

@@ -1,89 +1,28 @@
 # Plan: logrotate-mode (mail.log stops rotating in some images)
 
-**Status:** candidate  
-**Version:** patch; no schema, no configuration surface.  
-**Order:** independent. Worth doing before anything that lets an instance run
-unattended for months.
+**Status:** done  
+**Version:** patch; no schema, no configuration surface.
 
 ---
 
-## What was observed
+## Summary
 
-The container log carries, on every start:
+`mail.log` stopped rotating when `/etc/logrotate.d/mail` landed in the image
+with group/other write permission (e.g. build context from a Windows tar sync).
+logrotate ignores such configs but exits 0, so the loop looked healthy while
+the log grew without bound.
 
-```
-warning: Potentially dangerous mode on /etc/logrotate.d/mail: 0664
-error: Ignoring /etc/logrotate.d/mail because it is writable by group or others.
-```
+## What shipped
 
-logrotate refuses a configuration file that group or others may write, so
-`mail.log` is never rotated in an image with that mode. It grows until the
-volume does.
+- [`build/Dockerfile`](../../build/Dockerfile): `COPY --chmod` pins config
+  (`0644`) and script (`0755`) modes so the image no longer depends on checkout
+  file modes.
+- [`build/logrotate-loop.sh`](../../build/logrotate-loop.sh): preflight and
+  per-iteration checks refuse group/other-writable configs; logrotate stderr
+  mentioning `Ignoring` is fatal.
+- [`test/e2e/logrotate_check.go`](../../test/e2e/logrotate_check.go): asserts
+  mode `644`, forced `logrotate -f`, and that a group-writable context file
+  still produces `644` in the image.
 
-Measured across three images built on the same host from the same commit range:
-
-| Image built from | Mode of `/etc/logrotate.d/mail` |
-|---|---|
-| a sync made two days earlier | `0644` — works |
-| a later sync (`tar -czf -` pipe from a Windows checkout) | `0666` |
-| a later sync (`git archive` from the same checkout) | `0664` |
-
-So the file is fine in the repository (git records `100644`) and is spoiled on
-the way into the build context. `COPY build/logrotate-mail.conf
-/etc/logrotate.d/mail` ([build/Dockerfile](../../build/Dockerfile)) takes the
-mode from the context as it finds it, and an archive produced from a checkout
-without POSIX permissions carries the umask-widened mode instead of the one git
-recorded.
-
-**Not established:** whether images built by the release workflow are affected.
-They are built from a checkout on Linux, where the mode should survive as
-`0644`, but the published image could not be pulled to check. Confirm before
-concluding that only locally built images have this.
-
-## Why it deserves a plan rather than a one-line fix
-
-Three separate things are wrong, and fixing only the visible one leaves the
-other two.
-
-1. **The image trusts the build context's file modes.** Every `COPY` in the
-   Dockerfile has this property, not just this one; the scripts happen to be
-   `chmod +x`-ed afterwards, which is why they were never noticed.
-2. **The failure is silent.** `logrotate-loop.sh` runs
-   `logrotate /etc/logrotate.d/mail` and only reports a failure on a non-zero
-   exit — but logrotate *ignores* the file and exits 0, so the loop reports
-   nothing and the operator's only clue is a warning printed once at start.
-3. **Nothing checks the outcome.** No test or health check notices that
-   `mail.log` has not rotated, and the panel's Status page has no view of it.
-
-## Directions to weigh
-
-- `COPY --chmod=0644` on the configuration files (and an explicit mode on the
-  scripts instead of the later `chmod +x`), which makes the image's file modes a
-  property of the Dockerfile rather than of whoever built it. Needs a check of
-  the minimum BuildKit version the project is willing to require.
-- Or an explicit `chmod` in the same `RUN` that already fixes the scripts —
-  cruder, no build-time requirement.
-- Make `logrotate-loop.sh` fail loudly: `logrotate` has `--debug`-free ways to
-  be told to care, but the simplest reliable check is that the loop verifies
-  the configuration is readable-and-not-writable before entering the loop, and
-  exits non-zero so supervisord reports it.
-- Consider whether the e2e stack should assert that a rotation actually happens
-  (it can run with a short `LOGROTATE_INTERVAL_SECONDS`).
-
-## Done when
-
-- An image built from a Windows checkout and one built by the release workflow
-  both carry `0644`, and rotation runs in both.
-- A configuration logrotate would ignore makes the container say so in a way an
-  operator will see, rather than exiting 0.
-- The dev loop's sync step cannot silently widen file modes again, or the image
-  no longer cares if it does.
-
-## Risks
-
-- Low blast radius, but it touches the image's startup path — a mistake here is
-  a container that will not start rather than a log that does not rotate.
-- The `create 0640 postfix selfpost` line in the rotate configuration is load
-  bearing (see the comment in `logrotate-loop.sh`: a postlogd-triggered recreate
-  lands the file unreadable by the unprivileged panel). Any rework of the
-  configuration must keep it.
+`create 0640 postfix selfpost` in [`build/logrotate-mail.conf`](../../build/logrotate-mail.conf)
+is unchanged — required for panel readability after rotation.

docs/roadmap.md

@@ -29,7 +29,6 @@ in `git log` and [CHANGELOG.md](../CHANGELOG.md).
 | inbound-relay | Inbound relay (backup-MX / forwarding) | **agreed** | [plans/inbound-relay.md](plans/inbound-relay.md) |
 | contributing | `CONTRIBUTING.md` | candidate | — |
 | dmarc-reports | DMARC aggregate report ingestion and panel UI | candidate | [plans/dmarc-reports.md](plans/dmarc-reports.md) |
-| logrotate-mode | `mail.log` stops rotating in some builds | candidate | [plans/logrotate-mode.md](plans/logrotate-mode.md) |
 | panel-docs | In-panel operator documentation | candidate | — |
 
 **Recommended order** (not binding): **inbound-relay** first among agreed

test/e2e/logrotate_check.go

@@ -0,0 +1,97 @@
+package e2e
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// checkLogrotateConfigMode verifies the image pins /etc/logrotate.d/mail at 0644
+// so logrotate will not silently ignore it (docs/plans/logrotate-mode.md).
+func checkLogrotateConfigMode(s *stack) error {
+	mode, err := s.execIn("selfpost", "stat", "-c", "%a", "/etc/logrotate.d/mail")
+	if err != nil {
+		return fmt.Errorf("stat logrotate config: %w", err)
+	}
+	mode = strings.TrimSpace(mode)
+	if mode != "644" {
+		return fmt.Errorf("/etc/logrotate.d/mail mode is %q, want 644", mode)
+	}
+	return nil
+}
+
+// checkLogrotateRotation forces a rotation and checks the recreated mail.log is
+// panel-readable (0640 postfix:selfpost per build/logrotate-mail.conf).
+func checkLogrotateRotation(s *stack) error {
+	const logPath = "/data/log/mail.log"
+	marker := "e2e-logrotate-marker\n"
+	if _, err := s.execIn("selfpost", "sh", "-c",
+		fmt.Sprintf("printf %q >> %s", marker, logPath)); err != nil {
+		return fmt.Errorf("write mail.log: %w", err)
+	}
+	if _, err := s.execIn("selfpost", "logrotate", "-f", "/etc/logrotate.d/mail"); err != nil {
+		return fmt.Errorf("logrotate -f: %w", err)
+	}
+	rotated, err := s.execIn("selfpost", "sh", "-c", "test -f /data/log/mail.log.1 && echo yes")
+	if err != nil || strings.TrimSpace(rotated) != "yes" {
+		return fmt.Errorf("expected /data/log/mail.log.1 after forced rotation (out=%q err=%v)", rotated, err)
+	}
+	mode, err := s.execIn("selfpost", "stat", "-c", "%a", logPath)
+	if err != nil {
+		return fmt.Errorf("stat rotated mail.log: %w", err)
+	}
+	if strings.TrimSpace(mode) != "640" {
+		return fmt.Errorf("new %s mode is %q, want 640", logPath, strings.TrimSpace(mode))
+	}
+	body, err := s.execIn("selfpost", "grep", "-F", strings.TrimSpace(marker), "/data/log/mail.log.1")
+	if err != nil || !strings.Contains(body, strings.TrimSpace(marker)) {
+		return fmt.Errorf("rotated file does not contain marker (out=%q err=%v)", body, err)
+	}
+	return nil
+}
+
+// TestImageBuildPreservesLogrotateMode builds from a context where
+// logrotate-mail.conf is group-writable and checks the image still ships 0644.
+func TestImageBuildPreservesLogrotateMode(t *testing.T) {
+	conf := filepath.Join(h.repoRoot, "build", "logrotate-mail.conf")
+	info, err := os.Stat(conf)
+	if err != nil {
+		t.Fatalf("stat source config: %v", err)
+	}
+	origMode := info.Mode().Perm()
+
+	if err := os.Chmod(conf, origMode|0o020); err != nil {
+		t.Fatalf("chmod g+w source config: %v", err)
+	}
+	t.Cleanup(func() {
+		_ = os.Chmod(conf, origMode)
+	})
+
+	tag := "selfpost:e2e-logrotate-mode"
+	build := exec.Command("docker", "build",
+		"-f", filepath.Join(h.repoRoot, "build", "Dockerfile"),
+		"-t", tag,
+		"--build-arg", "VERSION=e2e",
+		h.repoRoot,
+	)
+	build.Env = os.Environ()
+	if out, err := build.CombinedOutput(); err != nil {
+		t.Fatalf("docker build with group-writable context config: %v\n%s", err, out)
+	}
+	t.Cleanup(func() {
+		_, _ = exec.Command("docker", "rmi", "-f", tag).CombinedOutput()
+	})
+
+	run := exec.Command("docker", "run", "--rm", tag, "stat", "-c", "%a", "/etc/logrotate.d/mail")
+	run.Env = os.Environ()
+	out, err := run.CombinedOutput()
+	if err != nil {
+		t.Fatalf("stat in image: %v\n%s", err, out)
+	}
+	if strings.TrimSpace(string(out)) != "644" {
+		t.Fatalf("image logrotate config mode is %q, want 644", strings.TrimSpace(string(out)))
+	}
+}

test/e2e/main_test.go

@@ -105,6 +105,12 @@ func TestE2E(t *testing.T) {
 		if err := checkSupervisorProcesses(h); err != nil {
 			t.Fatal(err)
 		}
+		if err := checkLogrotateConfigMode(h); err != nil {
+			t.Fatal(err)
+		}
+		if err := checkLogrotateRotation(h); err != nil {
+			t.Fatal(err)
+		}
 		if err := waitForPanelReady(); err != nil {
 			t.Fatal(err)
 		}