enable keypair auth and some refactoring

entrypoint.sh

@@ -3,9 +3,19 @@
 # generate host keys if not present
 ssh-keygen -A
 
-# check wether a random root-password is provided
-if [ ! -z "${ROOT_PASSWORD}" ] && [ "${ROOT_PASSWORD}" != "root" ]; then
-    echo "root:${ROOT_PASSWORD}" | chpasswd
+# set root login mode by password or keypair
+if [ "${KEYPAIR_LOGIN}" = "true" ] && [ -f "${HOME}/.ssh/authorized_keys" ] ; then
+    sed -i "s/#PermitRootLogin.*/PermitRootLogin without-password/" /etc/ssh/sshd_config
+    sed -i "s/#PasswordAuthentication.*/PasswordAuthentication no/" /etc/ssh/sshd_config
+    echo "Enabled root-login by keypair and disabled password-login"
+else
+    sed -i s/#PermitRootLogin.*/PermitRootLogin\ yes/ /etc/ssh/sshd_config
+    set +x
+    if [ -n "${ROOT_PASSWORD}" ] && [ "${ROOT_PASSWORD}" != "root" ]; then
+        echo "root:${ROOT_PASSWORD}" | chpasswd
+    fi
+    set -x
+    echo "Enabled root-login by password"
 fi
 
 # do not detach (-D), log to stderr (-e), passthrough other arguments