Major update to stretch and many improvements

Improvements:
* Update to debian stretch
* Fix Dockerfile style
* Add FTP UID/GID Docker build args
* Add run-ssl to Makefile for testing SSL config
* Fix scripts style
* Fix scripts issues reported by shellcheck
* Add FTP_CHOWN_ROOT function to chown /srv in the container
* Add allow_writeable_chroot=YES to vsftpd_ssl.conf to match vsftpd.conf
* Update README.md

entry.sh

@@ -1,34 +1,41 @@
 #!/usr/bin/env bash
+# vsftpd container entrypoint script 
 
 set -e
 
-[ "$DEBUG" == 'true' ] && set -x
+[[ "${DEBUG}" == "true" ]] && set -x
 
 # Generate password if hash not set
-if [ ! -z "$FTP_PASSWORD" -a -z "$FTP_PASSWORD_HASH" ]; then
-  FTP_PASSWORD_HASH=$(echo "$FTP_PASSWORD" | mkpasswd -s -m sha-512)
+if [[ ! -z "${FTP_PASSWORD}" ]] && [[ -z "${FTP_PASSWORD_HASH}" ]]; then
+  FTP_PASSWORD_HASH="$(echo "${FTP_PASSWORD}" | mkpasswd -s -m sha-512)"
 fi
 
-if [ ! -z "$FTP_USER" -a ! -z "$FTP_PASSWORD_HASH" ]; then
-    /add-virtual-user.sh -d "$FTP_USER" "$FTP_PASSWORD_HASH"
+if [[ ! -z "${FTP_USER}" ]] || [[ ! -z "${FTP_PASSWORD_HASH}" ]]; then
+  /add-virtual-user.sh -d "${FTP_USER}" "${FTP_PASSWORD_HASH}"
 fi
 
 # Support multiple users
-while read user; do
-	IFS=: read name pass <<< "${!user}"
-	echo "Adding user $name"
-	/add-virtual-user.sh "$name" "$pass"
+while read -r user; do
+  IFS=: read -r name pass <<< "${!user}"
+  echo "Adding user ${name}"
+  /add-virtual-user.sh "${name}" "${pass}"
 done < <(env | grep "FTP_USER_" | sed 's/^\(FTP_USER_[a-zA-Z0-9]*\)=.*/\1/')
 
 # Support user directories
-if [ ! -z "$FTP_USERS_ROOT" ]; then
-	sed -i 's/local_root=.*/local_root=\/srv\/$USER/' /etc/vsftpd*.conf
+if [[ ! -z "${FTP_USERS_ROOT}" ]]; then
+  # shellcheck disable=SC2016
+  sed -i 's/local_root=.*/local_root=\/srv\/$USER/' /etc/vsftpd*.conf
 fi
 
-function vsftpd_stop {
+# Manage /srv permissions
+if [[ ! -z "${FTP_CHOWN_ROOT}" ]]; then
+  chown ftp:ftp /srv
+fi
+
+vsftpd_stop() {
   echo "Received SIGINT or SIGTERM. Shutting down vsftpd"
   # Get PID
-  pid=$(cat /var/run/vsftpd/vsftpd.pid)
+  pid="$(cat /var/run/vsftpd/vsftpd.pid)"
   # Set TERM
   kill -SIGTERM "${pid}"
   # Wait for exit
@@ -37,13 +44,13 @@ function vsftpd_stop {
   echo "Done"
 }
 
-if [ "$1" == "vsftpd" ]; then
+if [[ "${1}" == "vsftpd" ]]; then
   trap vsftpd_stop SIGINT SIGTERM
-  echo "Running $@"
-  $@ &
-  pid="$!"
+  echo "Running ${*}"
+  "${@}" &
+  pid="${!}"
   echo "${pid}" > /var/run/vsftpd/vsftpd.pid
-  wait "${pid}" && exit $?
+  wait "${pid}" && exit ${?}
 else
-  exec "$@"
+  exec "${@}"
 fi