Nahamcon 2021
Dice Roll
The given script suggests that it is using random number generators, python uses mersenne twister algorithm, googling we find a github repo of python module which enable us to predict the number.
https://github.com/kmyk/mersenne-twister-predictor
We use the following code, to automate the process using pwntools
from pwn import *
from mt19937predictor import MT19937Predictor
import re
predictor = MT19937Predictor()
r = remote('challenge.nahamcon.com' , '31784')
r.recvuntil('> ')
for i in range (0, 625):
r.sendline('2')
text = r.recvuntil('> ')
print(text)
num = [int(s) for s in text.split() if s.isdigit()]
print(num)
num = num[0]
predictor.setrandbits(num, 32)
flag = predictor.getrandbits(32)
r.sendline('3')
print(r.recvuntil('> '))
r.sendline(str(flag))
print(r.recv(2048))