ctf-tcp-proxy.py

#!/usr/bin/python3
import socket
import ssl
import sys
import asyncio

BASE_HOSTNAME = '{}.ctf-challenges.example.com'
DEFAULT_CLIENT_PORT = 7000
REMOTE_PORT = 7000
BUF_SIZE = 1024

# https://stackoverflow.com/questions/46413879/how-to-create-tcp-proxy-server-with-asyncio
async def create_pipe(reader, writer):
    try:
        while not reader.at_eof():
            writer.write(await reader.read(BUF_SIZE))
    finally:
        writer.close()

async def proxy(hostname, lread, lwrite):
    context = ssl.create_default_context()
    rread, rwrite = await asyncio.open_connection(hostname, REMOTE_PORT, ssl=context)
    pipe1 = create_pipe(lread, rwrite)
    pipe2 = create_pipe(rread, lwrite)
    await asyncio.gather(pipe1, pipe2)

if __name__ == '__main__':
    if len(sys.argv) > 3 or len(sys.argv) < 2:
        print("usage: {} <name> [port]".format(sys.argv[0]))
        sys.exit(1)

    hostname = BASE_HOSTNAME.format(sys.argv[1])
    port = int(sys.argv[2]) if len(sys.argv) == 3 and sys.argv[2].isnumeric() else DEFAULT_CLIENT_PORT
    
    loop = asyncio.get_event_loop()
    server = loop.run_until_complete(
        asyncio.start_server(lambda r, w: proxy(hostname, r, w), '127.0.0.1', port)
    )
    print("proxy server listening on port", port)
    
    try:
        loop.run_forever()
    except KeyboardInterrupt:
        pass
    server.close()
    loop.run_until_complete(server.wait_closed())
    loop.close()