autossh reverse tunnel manager

autossh-reverse-tunnel-manager.sh

#!/usr/bin/bash
# author -  me and anthropic claude 
# Configuration
REMOTE_HOST="[email protected]"
REMOTE_PORT="23237"          # Port on the remote server
LOCAL_PORT="22"              # Local SSH port to expose
MONITOR_PORT="0"             # AutoSSH monitoring port (0 disables it)
AUTOSSH_PIDFILE="/tmp/reverse_tunnel_autossh.pid"
SSH_PIDFILE="/tmp/reverse_tunnel_ssh.pid"

# Log file for debugging
LOG_FILE="/tmp/reverse_tunnel.log"

start_tunnel() {
    # Check if tunnel is already running
    if [ -f "$AUTOSSH_PIDFILE" ] && kill -0 $(cat "$AUTOSSH_PIDFILE") 2>/dev/null; then
        echo "Reverse tunnel is already running."
        return 1
    fi

    # Export required AutoSSH settings
    export AUTOSSH_PIDFILE="$AUTOSSH_PIDFILE"
    export AUTOSSH_POLL=60
    export AUTOSSH_FIRST_POLL=30
    export AUTOSSH_GATETIME=0
    export AUTOSSH_LOGLEVEL=7        # Verbose logging for debugging
    export AUTOSSH_LOGFILE="$LOG_FILE"

    # Start AutoSSH in background
    autossh -M "$MONITOR_PORT" \
            -f \
            -N \
            -R "$REMOTE_PORT:localhost:$LOCAL_PORT" \
            "$REMOTE_HOST" \
            -o "ServerAliveInterval 30" \
            -o "ServerAliveCountMax 3" \
            -o "ExitOnForwardFailure yes" \
            -o "StrictHostKeyChecking accept-new" \
            -o "RemoteCommand none" \
            -o "RequestTTY no"

    if [ $? -eq 0 ]; then
        echo "Reverse tunnel started successfully."
        # Store the SSH process PID
        pgrep -f "ssh.*$REMOTE_HOST.*$REMOTE_PORT:localhost:$LOCAL_PORT" > "$SSH_PIDFILE"
        echo "You can now access this machine via: ssh -p $REMOTE_PORT localhost (when logged into $REMOTE_HOST)"
        echo "Or directly via: ssh -J $REMOTE_HOST -p $REMOTE_PORT localhost"
    else
        echo "Failed to start reverse tunnel."
        return 1
    fi
}

stop_tunnel() {
    local killed=0

    # Kill AutoSSH process if PID file exists
    if [ -f "$AUTOSSH_PIDFILE" ]; then
        if kill $(cat "$AUTOSSH_PIDFILE") 2>/dev/null; then
            killed=1
            echo "AutoSSH process terminated."
        fi
        rm -f "$AUTOSSH_PIDFILE"
    fi

    # Kill SSH process if PID file exists
    if [ -f "$SSH_PIDFILE" ]; then
        if kill $(cat "$SSH_PIDFILE") 2>/dev/null; then
            killed=1
            echo "SSH process terminated."
        fi
        rm -f "$SSH_PIDFILE"
    fi

    # Backup: Kill any remaining matching processes
    if pgrep -f "ssh.*$REMOTE_HOST.*$REMOTE_PORT:localhost:$LOCAL_PORT" > /dev/null; then
        pkill -f "ssh.*$REMOTE_HOST.*$REMOTE_PORT:localhost:$LOCAL_PORT"
        killed=1
        echo "Cleaned up remaining SSH processes."
    fi

    if [ $killed -eq 0 ]; then
        echo "No running reverse tunnel found."
        return 1
    fi
}

status_tunnel() {
    if [ -f "$AUTOSSH_PIDFILE" ] && kill -0 $(cat "$AUTOSSH_PIDFILE") 2>/dev/null; then
        echo "Reverse tunnel is running."
        echo "AutoSSH PID: $(cat "$AUTOSSH_PIDFILE")"
        [ -f "$SSH_PIDFILE" ] && echo "SSH PID: $(cat "$SSH_PIDFILE")"
        echo "Remote port: $REMOTE_PORT on $REMOTE_HOST"
        echo "Local port: $LOCAL_PORT"
        
        # Check if the tunnel is actually working
        if ss -tln | grep -q ":$LOCAL_PORT "; then
            echo "Local SSH port is listening."
        else
            echo "Warning: Local SSH port is not listening!"
        fi
        return 0
    else
        echo "Reverse tunnel is not running."
        return 1
    fi
}

check_dependencies() {
    if ! command -v autossh >/dev/null 2>&1; then
        echo "Error: autossh is not installed. Please install it first."
        echo "On Debian/Ubuntu: sudo apt-get install autossh"
        echo "On RedHat/CentOS: sudo yum install autossh"
        exit 1
    fi
}

case "$1" in
    start)
        check_dependencies
        start_tunnel
        ;;
    stop)
        stop_tunnel
        ;;
    status)
        status_tunnel
        ;;
    restart)
        stop_tunnel
        sleep 2
        start_tunnel
        ;;
    *)
        echo "Usage: $0 {start|stop|status|restart}"
        exit 1
        ;;
esac