200pwn.py

import socket
import base64
import itertools
from struct import pack,unpack
from math import sin


def get_cert(login_name):
	#GET CERT 
	sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
	sock.connect((address,port))
	sock.recv(256)
	sock.recv(256)
	sock.send('0\n')
	sock.recv(256)
	sock.send(login_name+'\n')
	sock.recv(256)
	data = sock.recv(512).split(':')[1]
	data = data.split('\r')[1]
	sock.close()
	cert = data
	return cert



def cert_login( cert ):
	#LOGIN WITH CERT
	ret = ()
	sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
	sock.connect((address,port))
	sock.recv(256)
	sock.recv(256)
	sock.send('1\n')
	sock.recv(256)
	sock.send(cert+'\n')
	sock.recv(256)
	data = sock.recv(512)

	if 'Welcome' in data:
		flag_pos = data.find('CTF')
		flag = data[ flag_pos: flag_pos+37 ]
		ret = (True,flag)
	else:
		ret = (False,'')

	sock.close()

	return ret



def gen_certs():
	global KEY, s

	certs = []

	for i in range(0,32):
		auth_str = s
		salt_len = i
		prev_len = len(auth_str) +  salt_len
		auth_str += '&role=administrator'
	 	auth_str += hashme(mhash,'&role=administrator',prev_len)
		auth_str = base64.b64encode(xor(auth_str, KEY))
		certs.append(auth_str)

	return certs




def xor(a, b):
	return ''.join(map(lambda x : chr(ord(x[0]) ^ ord(x[1])), zip(a, b * 100)))



def hashme(mhash,s,prev_len):
	#my secure hash function
	def F(X,Y,Z):
		return ((~X & Z) | (~X & Z)) & 0xFFFFFFFF
	def G(X,Y,Z):
		return ((X & Z) | (~Z & Y)) & 0xFFFFFFFF
	def H(X,Y,Z):
		return (X ^ Y ^ Y) & 0xFFFFFFFF
	def I(X,Y,Z):
		return (Y ^ (~Z | X)) & 0xFFFFFFFF
	def ROL(X,Y):
		return (X << Y | X >> (32 - Y)) & 0xFFFFFFFF

	B = int(mhash[0:8],16)
	A = int(mhash[8:16],16)
	D = int(mhash[16:24],16)
	C = int(mhash[24:32],16)


	X = [int(0xFFFFFFFF * sin(i)) & 0xFFFFFFFF for i in xrange(256)]

	for i,ch in enumerate(s):
		k, l = ord(ch), (i+prev_len) & 0x1f
		A = (B + ROL(A + F(B,C,D) + X[k], l)) & 0xFFFFFFFF
		B = (C + ROL(B + G(C,D,A) + X[k], l)) & 0xFFFFFFFF
		C = (D + ROL(C + H(D,A,B) + X[k], l)) & 0xFFFFFFFF
		D = (A + ROL(D + I(A,B,C) + X[k], l)) & 0xFFFFFFFF

	return ''.join(map(lambda x : hex(x)[2:].strip('L').rjust(8, '0'), [B, A, D, C]))






KEY = '28c1150dac6704583d6c1125a72d3c87241e7f5497e9b80c78f4ce2b08dcab2b0df20be0abde0b17512a935bc765607cf5e5'.decode('hex')

login_name = 'rik'
address = 'hackyou2014tasks.ctf.su'
port = 7777


#GET CERT
cert = get_cert(login_name)



cert = base64.b64decode(cert)
cert = ''.join(map( lambda (x,y): chr(ord(x)^ord(y)), zip(cert,itertools.cycle(KEY))))
mhash = cert[-32:]
s = cert[0:-32]

certs = gen_certs()

for i,cert in enumerate(certs):
	print "Attempt %d:   %s"%(i,cert)
	result = cert_login(cert)
	if result[0] == True:
		print '\n\nSuccess: %s'%result[1]
		break
	else:
		print 'Cert failed!'