def encrypt_msg(self, msg: bytes) -> Tuple[bytes, bytes]:
key = sha1(
self._session_key.to_bytes(
floor(self._session_key.bit_length() / 8) + 1, "big"))[:16]
iv = gen_random_bytes(16)
cbc = AESCipher(AESCipher.MODE_CBC, key, iv=iv)
return (iv, cbc.encrypt(pkcs7_pad(msg)))
def _encryption_oracle(bytes_: bytes) -> Tuple[bytes, str]:
key = gen_random_bytes(16)
iv = gen_random_bytes(16)
prefix = gen_random_bytes(random.randint(5, 10))
suffix = gen_random_bytes(random.randint(5, 10))
pt = prefix + bytes_ + suffix
cbc_mode = random.choice([True, False])
if cbc_mode:
cbc = AESCipher(AESCipher.MODE_CBC, key, iv=iv)
ct = cbc.encrypt(pkcs7_pad(pt))
answer = "cbc"
else:
ecb = AESCipher(AESCipher.MODE_ECB, key)
ct = ecb.encrypt(pkcs7_pad(pt))
answer = "ecb"
return ct, answer
def _get_token(user_data: str) -> bytes:
prefix = "comment1=cooking%20MCs;userdata="
suffix = ";comment2=%20like%20a%20pound%20of%20bacon"
token = prefix + quote(user_data) + suffix
return _ctr.encrypt(pkcs7_pad(token.encode("latin")))
def _encrypt_it(bytes_: bytes) -> bytes:
pt = bytes_ + _SECRET
ct = _ecb.encrypt(pkcs7_pad(pt))
return ct
def _encrypt(pt: bytes) -> (bytes, bytes):
iv = gen_random_bytes(16)
cbc = AESCipher(AESCipher.MODE_CBC, _KEY, iv=iv)
ct = cbc.encrypt(pkcs7_pad(pt))
return iv, ct
def challenge09(bytes_: bytes, block_size: int) -> bytes:
return pkcs7_pad(bytes_, block_size)
def _oracle(email: str) -> bytes:
cookie = bytes(_profile_for(email).encode("ascii"))
encrypted_cookie = _ecb.encrypt(pkcs7_pad(cookie))
return encrypted_cookie
def test_pkcs7_padding_add_block(self):
a = gen_random_bytes()
b = pkcs7_pad(a)
c = Padding.pad(a, 16)
assert b == c, "The result does not match the expected value"
