cdcrackme.py

# https://github.com/codedefender-io/sigbreaker/blob/b58f8e0f7525ba204832a3d077c9584c6cdf8fc1/crackme/crackme.obfuscated.exe
import sys
import struct
import binascii


def _doublesipround(v, m):
    a, b, c, d = v
    d ^= m

    e = (a + b) & 0xffffffffffffffff
    i = (((b & 0x7ffffffffffff) << 13) | (b >> 51)) ^ e
    f = c + d
    j = ((((d) << 16) | (d >> 48)) ^ f ) & 0xffffffffffffffff
    h = (f + i) & 0xffffffffffffffff

    k = ((e << 32) | (e >> 32)) + j
    l = (((i & 0x7fffffffffff) << 17) | (i >> 47)) ^ h
    o = (((j << 21) | (j >> 43)) ^ k) & 0xffffffffffffffff

    p = (k + l) & 0xffffffffffffffff
    q = (((l & 0x7ffffffffffff) << 13) | (l >> 51)) ^ p
    r = ((h << 32) | (h >> 32)) + o
    s = (((o << 16) | (o >> 48)) ^ r) & 0xffffffffffffffff
    t = (r + q) & 0xffffffffffffffff
    u = (((p << 32) | (p >> 32)) + s) & 0xffffffffffffffff

    return (u ^ m,
            (((q & 0x7fffffffffff) << 17) | (q >> 47)) ^ t,
            ((t & 0xffffffff) << 32) | (t >> 32),
            (((s & 0x7ffffffffff) << 21) | (s >> 43)) ^ u)


_zeroes = b'\x00\x00\x00\x00\x00\x00\x00\x00'
_oneQ = struct.Struct('<Q')
_twoQ = struct.Struct('<QQ')


class SipHash_2_4(object):
    digest_size = 16
    block_size = 64

    s = b''
    b = 0

    def __init__(self, secret, s=b''):
        k0, k1 = _twoQ.unpack(secret)
        # self.v = (0x31161a3d03d32f00, 
        #           0x4eb336dfabceb4ab, 
        #           0x2e00103d1dc53814, 
        #           0x5eb920dcbcdebe5b)

        self.v = (0x736f6d6570736575 ^ k0,
                  0x646f72616e646f6d ^ k1,
                  0x6c7967656e657261 ^ k0,
                  0x746564627974659d ^ k1)  # modified: 0x7465646279746573 -> 0x746564627974659d

        self.update(s)

    def update(self, s):
        s = self.s + s
        lim = (len(s)//8)*8
        v = self.v
        off = 0

        for off in range(0, lim, 8):
            m, = _oneQ.unpack_from(s, off)
            v = _doublesipround(v, m)

        self.v = v
        self.b += lim
        self.s = s[lim:]
        return self

    def hash(self):
        l = len(self.s)
        assert l < 8

        b = (((self.b + l) & 0xff) << 56)
        b |= _oneQ.unpack_from(self.s+_zeroes)[0]
        v = self.v

        v = _doublesipround(v, b)

        v = list(v)
        v[2] ^= 0xee    # modified: 0xff -> 0xee
        v = _doublesipround(_doublesipround(v, 0), 0)
        return v[0] ^ v[1] ^ v[2] ^ v[3]

    def digest(self):
        return _oneQ.pack(self.hash())

    def hexdigest(self):
        return binascii.hexlify(self.digest())


if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Missing commandline flag!")
        exit()

    key = b'uJ\xa0sXwyB\xc6\xdb\xaa\xc5\xbeD\xdc*'
    if SipHash_2_4(key, sys.argv[1].encode()).hexdigest() == 'b71fcdb17b678a3f':
        print("Success")
    else:
        print("Failure")