cert-reload: renew Postfix's copy of a renewed certificate (audit H2)
postfix-config.sh copies the mounted certificate and key into /etc/postfix/tls-internal at start (root-owned, key 0600) and Postfix reads the copy; cert-reload only ran `postfix reload` daily, which re-read the stale copy, so a certificate renewed while the container ran expired on 465/587 with the old one. postfix-cert-reload.sh now, every TLS_RELOAD_INTERVAL_SECONDS: compares the mount with the copy (cmp); when they differ and the certificate and key belong together (openssl public keys equal - a renewer writes them one after the other), writes each file beside its target, root-owned with the start's modes, renames it over the target, and reloads Postfix. Nothing changed - no reload. No copy (files missing at start) - the old periodic reload. Never exits non-zero. e2e renewed_certificate_picked_up: writes a new certificate into the stand's mount and waits (30 s) for port 465 to present its serial; compose.override.yml sets TLS_RELOAD_INTERVAL_SECONDS=2. supervisord.conf comment, architecture.md (process table, § Postfix TLS certs, the env knob), guide (after the proxies: picked up within a day). CHANGELOG [Unreleased], audit plan line ticked, roadmap 12/61. Evidence: GOOS=linux go vet in test/e2e clean; the server run of the stage follows before the push. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Claude Opus 5.5
@@ -1,25 +1,69 @@
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#!/bin/sh
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# Periodic `postfix reload` so refreshed TLS certificates are picked up (spec
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# 5.2 p.4). The reverse-proxy renews the PEM files in the read-only mount every
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# few months; Postfix only re-reads them on reload. A simple daily reload is
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# more than enough (a day of staleness is harmless) and far simpler than an
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# inotify watcher — the spec explicitly prefers this.
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# Picks up a renewed TLS certificate while the container runs (spec 5.2 p.4;
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# audit 2026-10-12, H2).
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#
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# Runs under supervisord as root, so it can reload Postfix directly. It sleeps
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# first, then reloads in a loop: no reload at container start (the wrapper is
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# still bringing Postfix up then) and none until at least one interval has
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# passed. A reload is harmless when nothing changed.
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set -eu
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# Postfix does not read the mounted files: postfix-config.sh copies them at
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# start into /etc/postfix/tls-internal, because Postfix wants the key owned by
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# root with mode 0600, which a read-only bind mount owned by the host's user
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# cannot give. A renewal of the mounted files therefore reaches Postfix only
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# through a new copy. Every interval this compares the mounted files with the
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# copy; when they differ, and the certificate and the key belong together (a
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# renewer writes them one after the other), it replaces the copy - each file
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# written beside its target and renamed over it, with the owner and modes of
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# the start - and reloads Postfix. When nothing changed it does nothing.
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#
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# Runs under supervisord as root. It sleeps first: at container start the
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# wrapper is still bringing Postfix up. It never exits non-zero, so a failure
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# does not trip the crashexit listener; it is logged and tried again.
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set -u
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INTERVAL="${TLS_RELOAD_INTERVAL_SECONDS:-86400}"
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SRC_CERT="${TLS_CERT_FILE:-/etc/postfix/tls/fullchain.pem}"
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SRC_KEY="${TLS_KEY_FILE:-/etc/postfix/tls/privkey.pem}"
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DIR=/etc/postfix/tls-internal
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reload() {
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if postfix reload; then
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echo "cert-reload: postfix reloaded ($1)"
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else
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echo "cert-reload: postfix reload failed, will retry after ${INTERVAL}s" >&2
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fi
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}
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# same_pair says whether a certificate and a private key belong together.
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same_pair() {
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cert_pub=$(openssl x509 -noout -pubkey -in "$1" 2>/dev/null) || return 1
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key_pub=$(openssl pkey -pubout -in "$2" 2>/dev/null) || return 1
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[ -n "$cert_pub" ] && [ "$cert_pub" = "$key_pub" ]
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}
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# install_copy SRC DST MODE: DST becomes a root-owned copy of SRC in one rename.
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install_copy() {
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cp -f "$1" "$2.new" && chown root:root "$2.new" && chmod "$3" "$2.new" && mv -f "$2.new" "$2"
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}
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refresh() {
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if [ ! -f "$DIR/fullchain.pem" ]; then
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# No copy: the mounted files were missing at start and Postfix was
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# pointed at them as they are. A reload is what picks up a change there.
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reload "periodic TLS refresh"
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return
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fi
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if cmp -s "$SRC_CERT" "$DIR/fullchain.pem" && cmp -s "$SRC_KEY" "$DIR/privkey.pem"; then
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return
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fi
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if ! same_pair "$SRC_CERT" "$SRC_KEY"; then
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echo "cert-reload: the mounted certificate and key differ from Postfix's copy but do not belong together; will look again after ${INTERVAL}s" >&2
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return
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fi
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if install_copy "$SRC_KEY" "$DIR/privkey.pem" 0600 && install_copy "$SRC_CERT" "$DIR/fullchain.pem" 0644; then
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reload "renewed certificate"
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else
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echo "cert-reload: copying the renewed certificate failed, will retry after ${INTERVAL}s" >&2
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fi
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}
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while true; do
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sleep "${INTERVAL}"
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if postfix reload; then
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echo "cert-reload: postfix reloaded (periodic TLS refresh)"
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else
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# Never exit non-zero: a transient reload failure must not trip the
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# crashexit listener and take the container down. Log and retry next cycle.
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echo "cert-reload: postfix reload failed, will retry after ${INTERVAL}s" >&2
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fi
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refresh
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done
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