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175 lines (135 loc) · 5.37 KB
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from binascii import hexlify
from hmac import compare_digest
from os import urandom
from p28 import MerkleDamgardHash
class MD4(MerkleDamgardHash):
def __init__(self, backdoored=False, backdoor=None):
super(MD4, self).__init__()
self.h = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476]
self.X = None
self.backdoored = backdoored
if self.backdoored:
self.backdoor = backdoor
self.h = self.backdoor[:]
def pad(self, msg: bytes) -> bytes:
padded = super(MD4, self).pad(msg)
return padded[:-8] + padded[-8:][::-1]
@staticmethod
def f(x, y, z):
return (x & y) | (~x & z)
@staticmethod
def g(x, y, z):
return (x & y) | (x & z) | (y & z)
@staticmethod
def h(x, y, z):
return x ^ y ^ z
def round1(self, a, b, c, d, i, s):
tmp = self.h[a] + MD4.f(self.h[b], self.h[c], self.h[d]) + self.X[i]
self.h[a] = self.rotateleft(tmp, s)
def round2(self, a, b, c, d, i, s):
tmp = self.h[a] + MD4.g(self.h[b], self.h[c], self.h[d]) + self.X[i]
tmp = (tmp + 0o13240474631) & 0xffffffff
self.h[a] = self.rotateleft(tmp, s)
def round3(self, a, b, c, d, i, s):
tmp = self.h[a] + MD4.h(self.h[b], self.h[c], self.h[d]) + self.X[i]
tmp = (tmp + 0o15666365641) & 0xffffffff
self.h[a] = self.rotateleft(tmp, s)
def hash(self, msg: bytes) -> bytes:
padded = self.pad(msg)
blocks = len(padded) // self.BLOCKSIZE
for i in range(blocks):
chunk = padded[i*self.BLOCKSIZE:(i+1)*self.BLOCKSIZE]
self.X = [x for x in map(
lambda word: int.from_bytes(word, byteorder='big'),
[chunk[j*4:(j+1)*4] for j in range(16)]
)]
if self.backdoored:
self.h = self.backdoor[:]
AA, BB, CC, DD = self.h
self.round1(0, 1, 2, 3, 0, 3)
self.round1(3, 0, 1, 2, 1, 7)
self.round1(2, 3, 0, 1, 2, 11)
self.round1(1, 2, 3, 0, 3, 19)
self.round1(0, 1, 2, 3, 4, 3)
self.round1(3, 0, 1, 2, 5, 7)
self.round1(2, 3, 0, 1, 6, 11)
self.round1(1, 2, 3, 0, 7, 19)
self.round1(0, 1, 2, 3, 8, 3)
self.round1(3, 0, 1, 2, 9, 7)
self.round1(2, 3, 0, 1, 10, 11)
self.round1(1, 2, 3, 0, 11, 19)
self.round1(0, 1, 2, 3, 12, 3)
self.round1(3, 0, 1, 2, 13, 7)
self.round1(2, 3, 0, 1, 14, 11)
self.round1(1, 2, 3, 0, 15, 19)
self.round2(0, 1, 2, 3, 0, 3)
self.round2(3, 0, 1, 2, 4, 5)
self.round2(2, 3, 0, 1, 8, 9)
self.round2(1, 2, 3, 0, 12, 13)
self.round2(0, 1, 2, 3, 1, 3)
self.round2(3, 0, 1, 2, 5, 5)
self.round2(2, 3, 0, 1, 9, 9)
self.round2(1, 2, 3, 0, 13, 13)
self.round2(0, 1, 2, 3, 2, 3)
self.round2(3, 0, 1, 2, 6, 5)
self.round2(2, 3, 0, 1, 10, 9)
self.round2(1, 2, 3, 0, 14, 13)
self.round2(0, 1, 2, 3, 3, 3)
self.round2(3, 0, 1, 2, 7, 5)
self.round2(2, 3, 0, 1, 11, 9)
self.round2(1, 2, 3, 0, 15, 13)
self.round3(0, 1, 2, 3, 0, 3)
self.round3(3, 0, 1, 2, 8, 9)
self.round3(2, 3, 0, 1, 4, 11)
self.round3(1, 2, 3, 0, 12, 15)
self.round3(0, 1, 2, 3, 2, 3)
self.round3(3, 0, 1, 2, 10, 9)
self.round3(2, 3, 0, 1, 6, 11)
self.round3(1, 2, 3, 0, 14, 15)
self.round3(0, 1, 2, 3, 1, 3)
self.round3(3, 0, 1, 2, 9, 9)
self.round3(2, 3, 0, 1, 5, 11)
self.round3(1, 2, 3, 0, 13, 15)
self.round3(0, 1, 2, 3, 3, 3)
self.round3(3, 0, 1, 2, 11, 9)
self.round3(2, 3, 0, 1, 7, 11)
self.round3(1, 2, 3, 0, 15, 15)
self.h[0] = (self.h[0] + AA) & 0xffffffff
self.h[1] = (self.h[1] + BB) & 0xffffffff
self.h[2] = (self.h[2] + CC) & 0xffffffff
self.h[3] = (self.h[3] + DD) & 0xffffffff
hashed = ((self.h[3] << 96) |
(self.h[2] << 64) |
(self.h[1] << 32) |
self.h[0])
self.h = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476]
return int.to_bytes(hashed, 16, byteorder='little')
def _md4mac(key: bytes, msg: bytes) -> bytes:
md4 = MD4()
mac = md4.hash(key + msg)
return mac
def p30() -> str:
msg = b'comment1=cooking%20MCs;userdata=foo;comment2=%20like%20a%20pound' \
b'%20of%20bacon'
key = urandom(16)
auth = _md4mac(key, msg)
msglen = len(msg) + len(key)
dummy = b'\x00' * msglen
m = MD4()
glue = m.pad(dummy)[msglen:]
hs = []
authval = int.from_bytes(auth, byteorder='little')
while authval:
hs.append(int(authval & 0xffffffff))
authval = authval >> 32
inject = b';admin=true'
tampered = MD4(backdoored=True, backdoor=hs)
forged = tampered.hash(dummy + glue + inject)
if compare_digest(forged, _md4mac(key, msg + glue + inject)):
return f'Message: {msg + glue + inject}\n' \
f'MAC: {hexlify(forged).decode()}'
else:
return 'Message Forgery Failed'
def main():
from main import Solution
return Solution('30: Break an MD4 keyed MAC using length extension', p30)