parlor.py

from pwn import *
import struct
import md5

r = remote('127.0.0.1', 4321)
print(r.recvuntil("quit\n====================\n"))

r.sendline("1")
print(r.recvuntil("Please pick odds (as a power of 2 between 1 and 112): "))

r.send("112")
print(r.recvuntil("good luck!"))

# Retrieve HASH(nounce + "abc")

r.sendline("3")
print(r.recvuntil("Okay, send us a nonce for this round!"))

r.send("abc")
print(r.recvuntil("odds of 2^112"))

result = r.recvuntil("luck next time!")
result_100bits = int(result[23:-33])

print(result)
print(result_100bits)

# Retrieve HASH(nounce + pad("abc") + "1")

r.sendline("3")
print(r.recvuntil("Okay, send us a nonce for this round!"))

initial_length = 16 + 3
r.send("abc\x80" + ("\x00" * (64 - 9 - initial_length) + struct.pack("<Q", initial_length << 3) + "1"))
print(r.recvuntil("odds of 2^112"))

result = r.recvuntil("luck next time!")
result_test_100bits = int(result[23:-33])

print(result)
print(result_test_100bits)

for i in xrange(0, 2**16):
	if i % 1000000 == 0:
		print i
		
	i_hash = hex(i * 2**(128 - 16) + result_100bits)[2:].replace("L", "")
	i_hash = "0" * (32 - len(i_hash)) + i_hash
	final_block = "1" + "\x80" + "\x00" * (64 - 9 - 1) + struct.pack("<Q", 65 << 3)
	state = list(struct.unpack("<4I", i_hash.decode("hex")))
	state = md5.md5_compress(state, final_block)
	final_hash  = "".join(struct.pack("<4I", state[0], state[1], state[2], state[3]))

	if int(final_hash.encode("hex"), 16) % 2**112 == result_test_100bits:
		print("Found %d" % i)
		break

state = list(struct.unpack("<4I", i_hash.decode("hex")))

for j in range(2, 100000000):
	m = str(j)
	final_block = m + "\x80" + "\x00" * (64 - 9 - len(m)) + struct.pack("<Q", (64 + len(m)) << 3)
	to_send = "abc\x80" + "\x00" * (64 - 9 - initial_length) + struct.pack("<Q", initial_length << 3) + m
	final_state = md5.md5_compress(state, final_block)
	final_hash  = "".join(struct.pack("<4I", final_state[0], final_state[1], final_state[2], final_state[3]))
	final_int = int(final_hash.encode("hex"), 16)
	
	nb_bet = 0
	while final_int % 2 == 0:
		nb_bet += 1
		final_int /= 2

	if nb_bet == 0:
		continue

	r.sendline("4")
	print(r.recvuntil("Your current balance is $"))
	amount = int(r.recv(1024))

	print("At %d$ ..." % amount)
	r.sendline("1")
	print(r.recvuntil("Please pick odds (as a power of 2 between 1 and 112): "))
	r.sendline("%d" % nb_bet)

	r.sendline("2")
	r.recvuntil("Please pick your bet amount (between 0 and %d): " % amount)
	r.send("%d" % amount)

	r.sendline("3")
	print(r.recvuntil("Okay, send us a nonce for this round!"))
	r.send(to_send)
	r.recvuntil("Wow! You won, congratulations!")