trigger new keys generation if supplied key file is empty

README.md

@@ -22,7 +22,7 @@ From there, system install can be performed as usual with `setup-alpine` for ins
 Add-on files may be added next to `headless.apkovl.tar.gz` to customise boostrapping configuration (sample files are provided):
 - `wpa_supplicant.conf`[^2] (*mandatory for wifi usecase*): define wifi SSID & password.
 - `interfaces`[^2] (*optional*): define network interfaces at will, if defaults DCHP-based are not suitable.
-- `ssh_host_*_key*` (*optional*): provide custom ssh keys to be injected (may be stored), instead of using bundled ones[^1] (not stored).
+- `ssh_host_*_key*` (*optional*): provide custom ssh keys to be injected (may be stored), instead of using bundled ones[^1] (not stored). Providing an empty key file will trigger new keys generation (ssh server may take longer to start).
 - `unattended.sh`[^2] (*optional*): create custom automated deployment script to further tune & extend actual setup (backgrounded).
 
 

overlay/etc/local.d/headless.start

@@ -94,10 +94,6 @@ cat <<-EOF >> /etc/ssh/sshd_config
 	Banner /tmp/.trash/banner
 	EOF
 
-cat <<-EOF >> /etc/conf.d/sshd
-	sshd_disable_keygen=yes
-	EOF
-
 # banner file
 cat <<-EOF > /tmp/.trash/banner
 
@@ -107,6 +103,7 @@ cat <<-EOF > /tmp/.trash/banner
 
 # bundled temporary keys are moved in RAM /tmp so they won't be stored
 # within permanent config later (new ones will then be generated)
+KEYGEN_STANCE="sshd_disable_keygen=yes"
 mv /etc/ssh/ssh_host_*_key* /tmp/.trash/.
 # inject optional custom keys (those might be stored)
 if ! install -m600 "${ovlpath}"/ssh_host_*_key* /etc/ssh/; then
@@ -115,8 +112,18 @@ if ! install -m600 "${ovlpath}"/ssh_host_*_key* /etc/ssh/; then
 		HostKey /tmp/.trash/ssh_host_ed25519_key
 		HostKey /tmp/.trash/ssh_host_rsa_key
 		EOF
+else
+	# look for empty key within injected ones: generate new keys if found
+	if find /etc/ssh/ -maxdepth 1 -type f -name 'ssh_host_*_key*' -empty | grep -q .; then
+		rm /etc/ssh/ssh_host_*_key*
+		KEYGEN_STANCE=""
+		logger -st ${0##*/} "Will generate new SSH keys..."
+	else
+		logger -st ${0##*/} "Using injected SSH keys..."
+	fi
 fi
 
+echo "$KEYGEN_STANCE" >> /etc/conf.d/sshd
 rc-service sshd start
 
 ## Prep for final post-cleanup