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Backport the AES KWP fix (#4164)

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* fix bug with n % 8 length wrapping on AESKWP (#4160)

* fix bug with n % 8 length wrapping on AESKWP

* review feedback

* add changelog
This commit is contained in:
Paul Kehrer 2018-03-20 18:42:18 -04:00 committed by Alex Gaynor
parent b17f0527a0
commit be31b36152
3 changed files with 35 additions and 2 deletions
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4
CHANGELOG.rst
View file

@ -8,6 +8,10 @@ Changelog
* Reverted a change to ``GeneralNames`` which prohibited having zero elements,
due to breakages.
* Fixed a bug in
:func:`~cryptography.hazmat.primitives.keywrap.aes_key_unwrap_with_padding`
that caused it to raise ``InvalidUnwrap`` when key length modulo 8 was
zero.
.. _v2-2:

9
src/cryptography/hazmat/primitives/keywrap.py
View file

@ -118,11 +118,16 @@ def aes_key_unwrap_with_padding(wrapping_key, wrapped_key, backend):
b = (8 * n) - mli
if (
not bytes_eq(a[:4], b"\xa6\x59\x59\xa6") or not
8 * (n - 1) < mli <= 8 * n or not bytes_eq(data[-b:], b"\x00" * b)
8 * (n - 1) < mli <= 8 * n or (
b != 0 and not bytes_eq(data[-b:], b"\x00" * b)
)
):
raise InvalidUnwrap()
return data[:-b]
if b == 0:
return data
else:
return data[:-b]
def aes_key_unwrap(wrapping_key, wrapped_key, backend):

24
tests/hazmat/primitives/test_keywrap.py
View file

@ -141,6 +141,18 @@ class TestAESKeyWrapWithPadding(object):
)
assert params["c"] == binascii.hexlify(wrapped_key)
@pytest.mark.parametrize(
"params",
_load_all_params("keywrap", ["kwp_botan.txt"], load_nist_vectors)
)
def test_wrap_additional_vectors(self, backend, params):
wrapping_key = binascii.unhexlify(params["key"])
key_to_wrap = binascii.unhexlify(params["input"])
wrapped_key = keywrap.aes_key_wrap_with_padding(
wrapping_key, key_to_wrap, backend
)
assert wrapped_key == binascii.unhexlify(params["output"])
@pytest.mark.parametrize(
"params",
_load_all_params(
@ -163,6 +175,18 @@ class TestAESKeyWrapWithPadding(object):
)
assert params["p"] == binascii.hexlify(unwrapped_key)
@pytest.mark.parametrize(
"params",
_load_all_params("keywrap", ["kwp_botan.txt"], load_nist_vectors)
)
def test_unwrap_additional_vectors(self, backend, params):
wrapping_key = binascii.unhexlify(params["key"])
wrapped_key = binascii.unhexlify(params["output"])
unwrapped_key = keywrap.aes_key_unwrap_with_padding(
wrapping_key, wrapped_key, backend
)
assert unwrapped_key == binascii.unhexlify(params["input"])
def test_unwrap_invalid_wrapped_key_length(self, backend):
# Keys to unwrap must be at least 16 bytes
with pytest.raises(ValueError, match='Must be at least 16 bytes'):