Hack you 2014 hashme solver: at katagaitai CTF勉強会 #5 - 関東|med

solve.py

from roputils import Proc
from math import sin

def xorstr(x, k):
  if len(k) < len(x):
    k = k * (len(x)//len(k)+1)
  return "".join([chr(ord(x)^ord(y)) for x,y in zip(x, k)])

def length_extension(A, B, C, D, start_i, append):
  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
  X = [int(0xFFFFFFFF * sin(i)) & 0xFFFFFFFF for i in xrange(256)]
  for i, ch in enumerate(append):
    k, l = ord(ch), (start_i + i) & 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]))

def get_certificate(name):
  p.writeline("0")
  p.writeline(name)
  p.read_until("e:")
  p.readline()
  cert = p.readline().strip().decode("base64")
  return cert

p = Proc(host="katagaitai.orz.hm", port=7777)

p.read()

cert = get_certificate("A"*200)
plain = "login=%s&role=anonymous" % ("A"*200)
key = xorstr(cert, plain)[:50]
print "[+] Key = %s" % key.encode("hex")

cert = get_certificate("eshiho")
plain = "login=eshiho&role=anonymous"
hash = xorstr(cert, key)[len(plain):]
print "[+] Hash = %s" % hash
B = int(hash[:8], 16)
A = int(hash[8:16], 16)
D = int(hash[16:24], 16)
C = int(hash[24:32], 16)

for i in xrange(32):
  h_ = length_extension(A, B, C, D, i, "&role=administrator")
  p.writeline("1")
  p.read_until("certificate:\n")
  cert_ = (xorstr(plain + "&role=administrator" + h_, key)).encode("base64").replace("\n", "")
  p.writeline(cert_)
  d = p.readline()
  print "[+] i = %d, result = %r" % (i, d)
  if "Welcome" in d:
    print p.readline()
    break