From 7f3e5a22e18e091e2eeabaa47a18a854788e7db8 Mon Sep 17 00:00:00 2001
From: Erik Wramner <erik@wramner.name>
Date: Thu, 1 Aug 2019 09:58:22 +0200
Subject: [PATCH] Create checksums in start script, avoid race condition

---
 target/check-for-changes.sh | 26 ++++++++++++++------------
 target/start-mailserver.sh  | 26 ++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/target/check-for-changes.sh b/target/check-for-changes.sh
index 2fbd9683..5a5ab494 100755
--- a/target/check-for-changes.sh
+++ b/target/check-for-changes.sh
@@ -2,15 +2,8 @@
 
 # create date for log output
 log_date=$(date +"%Y-%m-%d %H:%M:%S ")
-# Prevent a start too early
-sleep 5
 echo "${log_date} Start check-for-changes script."
 
-# create checksum file outside mounted directory
-# the checksum file should be reused on subsequent runs,
-# but only by this container, not by others
-CHKSUM_FILE=/tmp/docker-mailserver-config-chksum
-
 # change directory
 cd /tmp/docker-mailserver
 
@@ -18,7 +11,14 @@ cd /tmp/docker-mailserver
 if [ ! -f postfix-accounts.cf ]; then
    echo "${log_date} postfix-accounts.cf is missing! This should not run! Exit!"
    exit
-fi 
+fi
+
+# Verify checksum file exists; must be prepared by start-mailserver.sh
+CHKSUM_FILE=/tmp/docker-mailserver-config-chksum
+if [ ! -f $CHKSUM_FILE ]; then
+   echo "${log_date} ${CHKSUM_FILE} is missing! Start script failed? Exit!"
+   exit
+fi
 
 # Determine postmaster address, duplicated from start-mailserver.sh
 # This script previously didn't work when POSTMASTER_ADDRESS was empty
@@ -30,15 +30,15 @@ fi
 PM_ADDRESS="${POSTMASTER_ADDRESS:=postmaster@${DOMAINNAME}}"
 echo "${log_date} Using postmaster address ${PM_ADDRESS}"
 
-# create an array of files to monitor (perhaps simple *.cf would be ok here)
+# Create an array of files to monitor, must be the same as in start-mailserver.sh
 declare -a cf_files=()
 for file in postfix-accounts.cf postfix-virtual.cf postfix-aliases.cf; do
   [ -f "$file" ] && cf_files+=("$file")
 done
 
-# Update / generate after start
-echo "${log_date} Makeing new checksum file."
-sha512sum ${cf_files[@]/#/--tag } >$CHKSUM_FILE
+# Wait to make sure server is up before we start
+# Plus the files have just been generated, no hurry to process changes
+sleep 20
 
 # Run forever
 while true; do
@@ -54,6 +54,8 @@ if [[ $chksum == *"FAIL"* ]]; then
 
 	# Bug alert! This overwrites the alias set by start-mailserver.sh
 	# Take care that changes in one script are propagated to the other
+        # Also note that changes are performed in place and are not atomic
+        # We should fix that and write to temporary files, stop, swap and start
 
 	#regen postix aliases.
 	echo "root: ${PM_ADDRESS}" > /etc/aliases
diff --git a/target/start-mailserver.sh b/target/start-mailserver.sh
index 2ccc6566..e715b28b 100644
--- a/target/start-mailserver.sh
+++ b/target/start-mailserver.sh
@@ -49,6 +49,7 @@ DEFAULT_VARS["VIRUSMAILS_DELETE_DELAY"]="${VIRUSMAILS_DELETE_DELAY:="7"}"
 ##########################################################################
 HOSTNAME="$(hostname -f)"
 DOMAINNAME="$(hostname -d)"
+CHKSUM_FILE=/tmp/docker-mailserver-config-chksum
 ##########################################################################
 # << GLOBAL VARS
 ##########################################################################
@@ -88,6 +89,7 @@ function register_functions() {
 	################### >> setup funcs
 
 	_register_setup_function "_setup_default_vars"
+	_register_setup_function "_setup_chksum_file"
 
 	if [ "$ENABLE_ELK_FORWARDER" = 1 ]; then
 		_register_setup_function "_setup_elk_forwarder"
@@ -439,6 +441,30 @@ function _setup_default_vars() {
 	done
 }
 
+function _setup_chksum_file() {
+        notify 'task' "Setting up configuration checksum file"
+
+
+        if [ -d /tmp/docker-mailserver ]; then
+          pushd /tmp/docker-mailserver
+
+          declare -a cf_files=()
+          for file in postfix-accounts.cf postfix-virtual.cf postfix-aliases.cf; do
+            [ -f "$file" ] && cf_files+=("$file")
+          done
+
+          notify 'inf' "Creating $CHKSUM_FILE"
+          sha512sum ${cf_files[@]/#/--tag } >$CHKSUM_FILE
+
+          popd
+        else
+          # We could just skip the file, but perhaps config can be added later?
+          # If so it must be processed by the check for changes script
+          notify 'inf' "Creating empty $CHKSUM_FILE (no config)"
+          touch $CHKSUM_FILE
+        fi
+}
+
 function _setup_mailname() {
 	notify 'task' 'Setting up Mailname'