Connect to SSH server through VPN

vpn.sh

#!/bin/bash

# Configuration variables - modify these
VPN_CONFIG="config.ovpn" # Set the path of the .ovpn file
SSH_HOST="0.0.0.0"
SSH_PORT="22"
SSH_USER="ubuntu"
LOCAL_PORT="2222" # Local port to forward SSH through

# Function to check if required commands exist
check_requirements() {
    local requirements=("openvpn" "ssh" "ip" "grep" "awk")
    for cmd in "${requirements[@]}"; do
        if ! command -v "$cmd" >/dev/null 2>&1; then
            echo "Error: Required command '$cmd' not found."
            exit 1
        fi
    done
}

# Function to clean up VPN connection on script exit
cleanup() {
    echo "Cleaning up..."
    if [ -f "/tmp/vpn-ssh.pid" ]; then
        local vpn_pid=$(cat "/tmp/vpn-ssh.pid")
        kill "$vpn_pid" 2>/dev/null
        rm -f "/tmp/vpn-ssh.pid"
    fi
    exit 0
}

# Set up trap for cleanup on script termination
trap cleanup EXIT INT TERM

# Function to wait for VPN interface
wait_for_vpn_interface() {
    local timeout=30
    local counter=0

    echo "Waiting for VPN interface to initialize..."
    while [ $counter -lt $timeout ]; do
        if ip link show | grep -q "tun[0-9]\|tap[0-9]"; then
            VPN_IFACE=$(ip link show | grep -o "tun[0-9]\|tap[0-9]" | head -n1)
            echo "Found VPN interface: $VPN_IFACE"
            return 0
        fi
        echo -n "."
        sleep 1
        counter=$((counter + 1))
    done
    echo "Timeout waiting for VPN interface"
    return 1
}

# Main script
main() {
    # Check for root privileges
    if [ "$EUID" -ne 0 ]; then
        echo "Please run as root"
        exit 1
    fi

    # Check for required commands
    check_requirements

    # Check if VPN config exists
    if [ ! -f "$VPN_CONFIG" ]; then
        echo "Error: VPN configuration file not found at $VPN_CONFIG"
        exit 1
    fi

    # Make sure TUN module is loaded
    if ! lsmod | grep -q "^tun\s"; then
        echo "Loading TUN module..."
        modprobe tun
    fi

    # Check if TUN/TAP device exists, create if not
    if [ ! -e /dev/net/tun ]; then
        echo "Creating TUN/TAP device..."
        mkdir -p /dev/net
        mknod /dev/net/tun c 10 200
        chmod 600 /dev/net/tun
    fi

    # Start OpenVPN in the background
    echo "Starting VPN connection..."
    openvpn --config "$VPN_CONFIG" --daemon --writepid "/tmp/vpn-ssh.pid" \
        --route-nopull --script-security 2

    # Wait for VPN interface to come up
    if ! wait_for_vpn_interface; then
        echo "Error: VPN interface did not come up within timeout"
        cleanup
        exit 1
    fi

    # Set up routing for SSH server through VPN
    echo "Setting up routing for SSH server..."
    ip route add "$SSH_HOST"/32 dev "$VPN_IFACE"

    # Start SSH connection
    echo "Establishing SSH connection..."
    ssh -p "$SSH_PORT" -L "$LOCAL_PORT:localhost:$SSH_PORT" "$SSH_USER@$SSH_HOST"

    # Keep script running until SSH exits
    wait
}

# Run main function
main

# Cleanup will be handled by trap on exit