add shadow management in config if user changes password

Author: thelamer

Dockerfile

@@ -112,6 +112,7 @@ RUN \
 	-L "http://security.ubuntu.com/ubuntu/pool/universe/libp/libpam4j/libpam4j-java_1.4-2+deb8u1build0.16.04.1_all.deb" && \
  dpkg -i /tmp/libpam.deb && \
  echo "**** cleanup ****" && \
+ mv /usr/bin/passwd /usr/bin/passwdbin && \
  apt-get autoclean && \
  rm -rf \
         /var/lib/apt/lists/* \

Dockerfile.aarch64

@@ -112,6 +112,7 @@ RUN \
 	-L "http://security.ubuntu.com/ubuntu/pool/universe/libp/libpam4j/libpam4j-java_1.4-2+deb8u1build0.16.04.1_all.deb" && \
  dpkg -i /tmp/libpam.deb && \
  echo "**** cleanup ****" && \
+ mv /usr/bin/passwd /usr/bin/passwdbin && \
  apt-get autoclean && \
  rm -rf \
         /var/lib/apt/lists/* \

Dockerfile.armhf

@@ -112,6 +112,7 @@ RUN \
 	-L "http://security.ubuntu.com/ubuntu/pool/universe/libp/libpam4j/libpam4j-java_1.4-2+deb8u1build0.16.04.1_all.deb" && \
  dpkg -i /tmp/libpam.deb && \
  echo "**** cleanup ****" && \
+ mv /usr/bin/passwd /usr/bin/passwdbin && \
  apt-get autoclean && \
  rm -rf \
         /var/lib/apt/lists/* \

root/etc/cont-init.d/61-shadow-config

@@ -0,0 +1,7 @@
+#!/usr/bin/with-contenv bash
+
+if [ -f /config/shadow ] && [ "$(md5sum /config/shadow| cut -c -32)" != "$(md5sum /etc/shadow| cut -c -32)" ]; then
+	cp /config/shadow /etc/shadow
+	chown root:shadow /etc/shadow
+	chmod 640 /etc/shadow
+fi 	  

root/usr/bin/passwd

@@ -0,0 +1,7 @@
+#! /bin/bash
+/usr/bin/passwdbin "$@"
+sudo cp /etc/shadow /config/shadow
+sudo chown ${USER}:${USER} /config/shadow
+echo "A wrapper has been executed to save shadow so your password survives upgrades"
+echo "If you would like to disable this feature please run:"
+echo "sudo mv /usr/bin/passwdbin /usr/bin/passwd"