feat: support configuring a shell for a user

Dockerfile

@@ -1,16 +1,17 @@
 FROM debian:bookworm-slim
 
-RUN set -eux; \
-    apt-get update; \
-    DEBIAN_FRONTEND=noninteractive apt-get upgrade -y; \
+RUN set -eux && \
+    apt-get update && \
+    DEBIAN_FRONTEND=noninteractive apt-get upgrade -y && \
     DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
         openssh-server \
         curl \
         telnet \
         net-tools \
         screen \
-    ; \
-    rm -rf /var/lib/apt/lists/*; \
+        vim \
+    && \
+    rm -rf /var/lib/apt/lists/* && \
     rm /etc/ssh/ssh_host_*key*
 
 ADD start.sh /

README.md

@@ -15,7 +15,8 @@
 | 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` |
-| `USERADD` | `{username}:{uid}:{gid};...` | Create user account(s) on startup |
+| `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}:{shell};...` | 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`) |
 
@@ -26,7 +27,8 @@ $ docker run -it \
     --name jumpbox \
     -v $(pwd)/jumpbox:/var/lib/jumpbox \
     -e "ROOT_AUTHORIZED_KEYS=/var/lib/jumpbox/authorized_keys"
-    -e "USERADD=jumpbox:1000:1000"
+    -e "HOSTKEYS=/var/lib/jumpbox/ssh_host_ed25519_key;/var/lib/jumpbox/ssh_host_rsa_key"
+    -e "USERADD=jumpbox:1000:1000:/bin/bash"
     -e "GROUPADD=jumpbox:1000"
     -p 1022:22 \
     pommib/jumpbox:latest
@@ -47,6 +49,7 @@ services:
       - '${PWD}/jumpbox:/var/lib/jumpbox'
     environment:
       ROOT_AUTHORIZED_KEYS: /var/lib/jumpbox/authorized_keys
-      USERADD: jumpbox:1000:1000
+      HOSTKEYS: /var/lib/jumpbox/ssh_host_ed25519_key;/var/lib/jumpbox/ssh_host_rsa_key
+      USERADD: jumpbox:1000:1000:/bin/bash
       GROUPADD: jumpbox:1000
 ```

build.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-set -x
+set -ex
 
 IMAGE=pommib/jumpbox:latest
 docker pull $IMAGE

start.sh

@@ -22,6 +22,7 @@ if [ ! -d "$BASE_DIR" ]; then
 fi
 
 # GROUPADD="group1:1000;group2:1001;group3:1002"
+i=""
 while [ "$GROUPADD" != "$i" ] ;do
     i=${GROUPADD%%;*}
     GROUPADD="${GROUPADD#$i;}"
@@ -32,19 +33,51 @@ while [ "$GROUPADD" != "$i" ] ;do
     groupadd --gid "$GROUP_GID" "$GROUP_NAME"
 done
 
-# USERADD="user1:1000:1000;user2:1001:1000;user3:1002:1002"
+# USERADD="user1:1000:1000:/bin/bash;user2:1001:1000:/bin/sh;user3:1002:1002:/bin/sh"
+i=""
+j=""
 while [ "$USERADD" != "$i" ] ;do
     i=${USERADD%%;*}
     USERADD="${USERADD#$i;}"
 
     USER_NAME=${i%%:*}
-    UID_GID="${i#$USER_NAME:}"
-    USER_UID="${UID_GID%%:*}"
-    USER_GID="${UID_GID#$USER_UID:}"
+    j="${i#$USER_NAME:}"
+    USER_UID="${j%%:*}"
+    j="${j#$USER_UID:}"
+    USER_GID="${j%%:*}"
+    j="${j#$USER_GID:}"
+    USER_SHELL=$j
 
-    useradd --home-dir "$BASE_DIR/$USER_NAME" --uid "$USER_UID" --gid "$USER_GID" "$USER_NAME"
+    useradd --home-dir "$BASE_DIR/$USER_NAME" --shell "$USER_SHELL" --uid "$USER_UID" --gid "$USER_GID" "$USER_NAME"
 done
 
+# HOSTKEYS="/var/lib/jumpbox/ssh_host_ed25519_key;/var/lib/jumpbox/ssh_host_rsa_key"
+i=""
+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