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>

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