feat: add support for configuring SSH2 HostKeys

Dockerfile

@@ -10,7 +10,8 @@ RUN set -eux; \
         net-tools \
         screen \
     ; \
-    rm -rf /var/lib/apt/lists/*
+    rm -rf /var/lib/apt/lists/* \
+    rm /etc/ssh/ssh_host_*key*
 
 ADD start.sh /
 

README.md

@@ -15,6 +15,7 @@
 | Key | Format | Description |
 | --- | --- | --- |
 | `ROOT_AUTHORIZED_KEYS` | `/path/to/file` | Path to file that contains the public SSH keys that can be used for root user authentication. This file will be copied to `/root/.ssh/authorized_keys` |
+| `HOSTKEYS` | `/path/to/hostkey` | Specifies a (semi-colon separated list of) file(s) containing a private host key used by SSH. |
 | `USERADD` | `{username}:{uid}:{gid};...` | Create user account(s) on startup |
 | `GROUPADD` | `{groupname}:{gid};...` | Create group account(s) on startup |
 | `BASE_DIR` | `/home` | Basedir used for user account creation (Default: `/home`) |
@@ -26,6 +27,7 @@ $ docker run -it \
     --name jumpbox \
     -v $(pwd)/jumpbox:/var/lib/jumpbox \
     -e "ROOT_AUTHORIZED_KEYS=/var/lib/jumpbox/authorized_keys"
+    -e "HOSTKEYS=/var/lib/jumpbox/ssh_host_ed25519_key;/var/lib/jumpbox/ssh_host_rsa_key"
     -e "USERADD=jumpbox:1000:1000"
     -e "GROUPADD=jumpbox:1000"
     -p 1022:22 \
@@ -47,6 +49,7 @@ services:
       - '${PWD}/jumpbox:/var/lib/jumpbox'
     environment:
       ROOT_AUTHORIZED_KEYS: /var/lib/jumpbox/authorized_keys
+      HOSTKEYS: /var/lib/jumpbox/ssh_host_ed25519_key;/var/lib/jumpbox/ssh_host_rsa_key
       USERADD: jumpbox:1000:1000
       GROUPADD: jumpbox:1000
 ```

start.sh

@@ -45,4 +45,37 @@ while [ "$USERADD" != "$i" ] ;do
     useradd --home-dir "$BASE_DIR/$USER_NAME" --uid "$USER_UID" --gid "$USER_GID" "$USER_NAME"
 done
 
+# HOSTKEYS="/var/lib/jumpbox/ssh_host_ed25519_key;/var/lib/jumpbox/ssh_host_rsa_key"
+if [ -n "$HOSTKEYS" ]; then
+    while [ "$HOSTKEYS" != "$i" ]; do
+        i=${HOSTKEYS%%;*}
+        HOSTKEYS="${HOSTKEYS#$i;}"
+
+        if [ ! -e "$i" ]; then
+            echo "Could not read $i, file is missing"
+            continue
+        else
+            echo "Configuring HostKey $i"
+        fi
+
+        FILENAME=$(basename "$i")
+        if [ ! -e "/etc/ssh/$FILENAME" ]; then
+            install -m 0600 "$i" "/etc/ssh/$FILENAME"
+            ssh-keygen -y -f "$i" > "/etc/ssh/$FILENAME.pub"
+            ssh-keygen -l -f "/etc/ssh/$FILENAME.pub"
+        fi
+
+        if ! grep "^HostKey /etc/ssh/$FILENAME" /etc/ssh/sshd_config; then
+            echo "HostKey /etc/ssh/$FILENAME" >> /etc/ssh/sshd_config
+        fi
+    done
+fi
+
+if [ -z "$(find /etc/ssh/ -maxdepth 1 -name 'ssh_host_*_key' -print -quit)" ]; then
+    echo "Creating SSH2 ED25519 key; this may take some time ..."
+    ssh-keygen -q -f /etc/ssh/ssh_host_ed25519_key -N '' -t ed25519
+    ssh-keygen -l -f /etc/ssh/ssh_host_ed25519_key.pub
+    echo "HostKey /etc/ssh/ssh_host_ed25519_key" >> /etc/ssh/sshd_config
+fi
+
 exec /usr/sbin/sshd -D -e