openssh: allow to override OpenSSL HostKeys when read-only-rootfs

With these changes it is possible to have a .bbappend that
- sets SYSCONFDIR to some persistent storage
- modifies SYSCONFDIR/sshd_config to use ssh host keys from
  the (writable) sysconfdir

Signed-off-by: André Draszik <adraszik@tycoint.com>
Reviewed-by: Stephane Ayotte <sayotte@tycoint.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>

2 files changed, 44 insertions, 6 deletions

diff --git a/meta/classes/rootfs-postcommands.bbclass b/meta/classes/rootfs-postcommands.bbclass
index 1d66a42953..78f7c55933 100644
--- a/meta/classes/rootfs-postcommands.bbclass
+++ b/meta/classes/rootfs-postcommands.bbclass
@@ -93,10 +93,10 @@ read_only_rootfs_hook () {
 	# and the keys under /var/run/ssh.
 	if [ -d ${IMAGE_ROOTFS}/etc/ssh ]; then
 		if [ -e ${IMAGE_ROOTFS}/etc/ssh/ssh_host_rsa_key ]; then
-			echo "SYSCONFDIR=/etc/ssh" >> ${IMAGE_ROOTFS}/etc/default/ssh
+			echo "SYSCONFDIR=\${SYSCONFDIR:-/etc/ssh}" >> ${IMAGE_ROOTFS}/etc/default/ssh
 			echo "SSHD_OPTS=" >> ${IMAGE_ROOTFS}/etc/default/ssh
 		else
-			echo "SYSCONFDIR=/var/run/ssh" >> ${IMAGE_ROOTFS}/etc/default/ssh
+			echo "SYSCONFDIR=\${SYSCONFDIR:-/var/run/ssh}" >> ${IMAGE_ROOTFS}/etc/default/ssh
 			echo "SSHD_OPTS='-f /etc/ssh/sshd_config_readonly'" >> ${IMAGE_ROOTFS}/etc/default/ssh
 		fi
 	fi
diff --git a/meta/recipes-connectivity/openssh/openssh/init b/meta/recipes-connectivity/openssh/openssh/init
index 1f63725cc0..386628afc8 100644
--- a/meta/recipes-connectivity/openssh/openssh/init
+++ b/meta/recipes-connectivity/openssh/openssh/init
@@ -19,10 +19,24 @@ fi
 [ -z "$SYSCONFDIR" ] && SYSCONFDIR=/etc/ssh
 mkdir -p $SYSCONFDIR
 
-HOST_KEY_RSA=$SYSCONFDIR/ssh_host_rsa_key
-HOST_KEY_DSA=$SYSCONFDIR/ssh_host_dsa_key
-HOST_KEY_ECDSA=$SYSCONFDIR/ssh_host_ecdsa_key
-HOST_KEY_ED25519=$SYSCONFDIR/ssh_host_ed25519_key
+parse_sshd_opts() {
+    set -- ${SSHD_OPTS} --
+    sshd_config=/etc/ssh/sshd_config
+    while true ; do
+        case "$1" in
+        -f*) if [ "$1" = "-f" ] ; then
+                 sshd_config="$2"
+                 shift
+             else
+                 sshd_config="${1#-f}"
+             fi
+             shift
+             ;;
+        --) shift; break;;
+        *) shift;;
+        esac
+    done
+}
 
 check_for_no_start() {
     # forget it if we're trying to start, and /etc/ssh/sshd_not_to_be_run exists
@@ -45,21 +59,45 @@ check_config() {
 }
 
 check_keys() {
+	# parse location of keys
+	local HOST_KEY_RSA
+	local HOST_KEY_DSA
+	local HOST_KEY_ECDSA
+	local HOST_KEY_ED25519
+
+	parse_sshd_opts
+	HOST_KEY_RSA=$(grep ^HostKey "${sshd_config}" | grep _rsa_ | tail -1 | awk ' { print $2 } ')
+	[ -z "${HOST_KEY_RSA}" ] && HOST_KEY_RSA=$(grep HostKey "${sshd_config}" | grep _rsa_ | tail -1 | awk ' { print $2 } ')
+	[ -z "${HOST_KEY_RSA}" ] && HOST_KEY_RSA=$SYSCONFDIR/ssh_host_rsa_key
+	HOST_KEY_DSA=$(grep ^HostKey "${sshd_config}" | grep _dsa_ | tail -1 | awk ' { print $2 } ')
+	[ -z "${HOST_KEY_DSA}" ] && HOST_KEY_DSA=$(grep HostKey "${sshd_config}" | grep _dsa_ | tail -1 | awk ' { print $2 } ')
+	[ -z "${HOST_KEY_DSA}" ] && HOST_KEY_DSA=$SYSCONFDIR/ssh_host_dsa_key
+	HOST_KEY_ECDSA=$(grep ^HostKey "${sshd_config}" | grep _ecdsa_ | tail -1 | awk ' { print $2 } ')
+	[ -z "${HOST_KEY_ECDSA}" ] && HOST_KEY_ECDSA=$(grep HostKey "${sshd_config}" | grep _ecdsa_ | tail -1 | awk ' { print $2 } ')
+	[ -z "${HOST_KEY_ECDSA}" ] && HOST_KEY_ECDSA=$SYSCONFDIR/ssh_host_ecdsa_key
+	HOST_KEY_ED25519=$(grep ^HostKey "${sshd_config}" | grep _ed25519_ | tail -1 | awk ' { print $2 } ')
+	[ -z "${HOST_KEY_ED25519}" ] && HOST_KEY_ED25519=$(grep HostKey "${sshd_config}" | grep _ed25519_ | tail -1 | awk ' { print $2 } ')
+	[ -z "${HOST_KEY_ED25519}" ] && HOST_KEY_ED25519=$SYSCONFDIR/ssh_host_ed25519_key
+
 	# create keys if necessary
 	if [ ! -f $HOST_KEY_RSA ]; then
 		echo "  generating ssh RSA key..."
+		mkdir -p $(dirname $HOST_KEY_RSA)
 		ssh-keygen -q -f $HOST_KEY_RSA -N '' -t rsa
 	fi
 	if [ ! -f $HOST_KEY_ECDSA ]; then
 		echo "  generating ssh ECDSA key..."
+		mkdir -p $(dirname $HOST_KEY_ECDSA)
 		ssh-keygen -q -f $HOST_KEY_ECDSA -N '' -t ecdsa
 	fi
 	if [ ! -f $HOST_KEY_DSA ]; then
 		echo "  generating ssh DSA key..."
+		mkdir -p $(dirname $HOST_KEY_DSA)
 		ssh-keygen -q -f $HOST_KEY_DSA -N '' -t dsa
 	fi
 	if [ ! -f $HOST_KEY_ED25519 ]; then
 		echo "  generating ssh ED25519 key..."
+		mkdir -p $(dirname $HOST_KEY_ED25519)
 		ssh-keygen -q -f $HOST_KEY_ED25519 -N '' -t ed25519
 	fi
 }