Implementing a Virtual Private Network (VPN) in Python

A Virtual Private Network (VPN) is a powerful tool that helps maintain privacy and security while browsing the internet. It encrypts and routes internet traffic through a secure tunnel, allowing users to access blocked content and mask their online identity. This article will discuss how to implement a basic VPN server and client using Python.

To follow along, you will need the following:

• Python 3.6 or higher installed on your machine
• Basic knowledge of Python programming and networking concepts

Additionally, we will be using the following libraries:

• socket: A built-in Python library for creating and working with network sockets
• ssl: A built-in Python library for implementing SSL/TLS encryption
• asyncio: A built-in Python library for asynchronous I/O

You can install the necessary libraries using pip:

pip install asyncio

Setting up a VPN server

First, let’s set up a basic SSL/TLS server using the asyncio and ssl libraries. This server will act as our VPN server.

import asyncio 
import ssl 
import socket 
 
async def handle_client(reader, writer): 
    data = await reader.read(100) 
    message = data.decode() 
    addr = writer.get_extra_info('peername') 
 
    print(f"Received {message} from {addr}") 
 
    print(f"Send: {message}") 
    writer.write(data) 
    await writer.drain() 
 
    print("Closing the connection") 
    writer.close() 
 
async def main(): 
    server_cert = 'server_cert.pem' 
    server_key = 'server_key.pem' 
    context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH) 
    context.load_cert_chain(certfile=server_cert, keyfile=server_key) 
 
    server = await asyncio.start_server( 
        handle_client, '0.0.0.0', 8888, ssl=context) 
 
    addr = server.sockets[0].getsockname() 
    print(f'Serving on {addr}') 
 
    async with server: 
        await server.serve_forever() 
 
asyncio.run(main())

This script will create an SSL/TLS server that listens for incoming connections on port 8888. Replace server_cert.pem and server_key.pem with your own SSL/TLS certificate and private key files.

Implementing a VPN client

Now, let’s create a VPN client that connects to our server and forwards local traffic through the secure tunnel.

import asyncio 
import ssl 
import socket 
 
async def tcp_echo_client(message): 
    ca_cert = 'ca_cert.pem' 
    context = ssl.create_default_context(ssl.Purpose.SERVER_AUTH) 
    context.load_verify_locations(cafile=ca_cert) 
 
    reader, writer = await asyncio.open_connection( 
        'vpn.example.com', 8888, ssl=context) 
 
    print(f'Send: {message}') 
    writer.write(message.encode()) 
 
    data = await reader.read(100) 
    print(f'Received: {data.decode()}') 
 
    print('Closing the connection') 
    writer.close() 
 
asyncio.run(tcp_echo_client('Hello, VPN!'))

Replace ca_cert.pem with your own Certificate Authority (CA) certificate and vpn.example.com with your VPN server's domain name or IP address.

Testing the VPN connection

Now that we have a VPN server and client, let’s test the connection. First, start the VPN server by running the server script. Then, run the client script to send a message through it.

Follow me on Medium, LinkedIn, and Twitter. Let’s connect!

I am looking forward to hearing from you!

All the best,

Luis Soares

CTO | Head of Engineering | Fintech & Blockchain SME | Web3 | DeFi | Cyber Security

#cybersecurity #vpn #tls #encryption #infrastructure #defense #privatenetwork #network #softwaredevelopment #softwareengineering #secure #connection