KRACK module requires python-cryptography

[ria4]

When python-cryptography or python3-cryptography packages are not installed, the KRACK module cannot be loaded.

>>> load_module("krack")
ERROR: Loading module scapy.modules.krack
Traceback (most recent call last):
  File "/home/ria/scapy/scapy/main.py", line 150, in _load
    mod = importlib.import_module(module)
  File "/usr/lib/python3.7/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/ria/scapy/scapy/modules/krack/__init__.py", line 28, in <module>
    from scapy.modules.krack.automaton import KrackAP  # noqa: F401
  File "/home/ria/scapy/scapy/modules/krack/automaton.py", line 7, in <module>
    from cryptography.hazmat.primitives import hashes
ModuleNotFoundError: No module named 'cryptography'

Calling @commial to assess whether the module could still offer functionalities with a crypto_valid around some blocks. But at first glance I believe a missing cryptography should completely prevent importing the module.

scapy/scapy/modules/krack/automaton.py

Lines 6 to 10 in a58e1b9

	from cryptography.hazmat.primitives import hashes
	from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
	from cryptography.hazmat.backends import default_backend

scapy/scapy/modules/krack/crypto.py

Lines 6 to 9 in a58e1b9

	from cryptography.hazmat.primitives.ciphers import Cipher, algorithms
	from cryptography.hazmat.backends import default_backend

[commial]

Hi,

This is indeed needed to install the PMK. I'm not sure the module still has an interest without being able to compute it. So preventing the module to be imported seems the right solution to me.

[p-l-]

I do not think this is a bug: you try to use a module => you need a dependency => Python complains with an ImportError. What would you expect?

[ria4]

It's not a breaking bug indeed. Other modules (TLS, IPsec...) explicitly specify the dependency, I believe it's relevant to do the same here.

[p-l-]

@ria4 thanks for your answer!