start_telnet_daemon.py

#!/usr/bin/env python3
import subprocess
import os
import sys

def launch():
    # Ensure python binary and script path are correct
    cmd = [sys.executable, 'telnet_shell.py']
    # start_new_session=True → child is in a new session group
    # stdout/stderr can go to log files or /dev/null
    with open('telnet_shell.log', 'ab', 0) as logf:
        subprocess.Popen(
            cmd,
            stdin=subprocess.DEVNULL,
            stdout=logf,
            stderr=logf,
            start_new_session=True
        )
    print("Launched telnet_shell.py in background.")

if __name__ == '__main__':
    launch()

telnet_shell.py

import socket
import threading
import os
import pty
import select
import signal  # ← for sending SIGKILL
import time

def handle_client(conn):
    # Fork a new process with a PTY
    pid, fd = pty.fork()
    if pid == 0:
        # Child process: replace with bash
        os.execv("/bin/bash", ["/bin/bash"])
    else:
        # Parent process: schedule a kill after 15 minutes
        def kill_shell():
            try:
                os.kill(pid, signal.SIGKILL)
            except ProcessLookupError:
                pass  # already exited
        timer = threading.Timer(900, kill_shell)
        timer.daemon = True
        timer.start()

        # Relay data between socket and PTY master
        try:
            while True:
                rlist, _, _ = select.select([conn, fd], [], [])
                
                if conn in rlist:
                    data = conn.recv(1024)
                    if not data:
                        break
                    os.write(fd, data)
                
                if fd in rlist:
                    output = os.read(fd, 1024)
                    if not output:
                        break
                    conn.sendall(output)
        finally:
            conn.close()
            timer.cancel()  # in case the shell exited early

def main():
    host = "0.0.0.0"
    port = 2323  # unprivileged port
    
    server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    server.bind((host, port))
    server.listen(5)
    
    print(f"[*] Listening on {host}:{port}")
    try:
        while True:
            conn, addr = server.accept()
            print(f"[*] Connection from {addr}, shell will auto-kill in 15 min")
            t = threading.Thread(target=handle_client, args=(conn,))
            t.daemon = True
            t.start()
    except KeyboardInterrupt:
        print("\n[*] Shutting down.")
    finally:
        server.close()

if __name__ == "__main__":
    main()