Opt no wipe argon2 32 pyx #11
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While using pymonocypher for a cryptographic protocol, we encountered an
AttributeError:
File "c_monocypher.pyx", line 328, in monocypher.argon2i_32
AttributeError: 'dict' object has no attribute 'nb_block'
Using the Python console to reproduce the error with monocypher 4.0.2.3:
>>> import monocypher
>>> monocypher.argon2i_32(nb_blocks=100000, nb_iterations=3,
password=password, salt=salt, key=None,
ad=None)
This will result in the following exception:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "c_monocypher.pyx", line 328, in monocypher.argon2i_32
AttributeError: 'dict' object has no attribute 'nb_block'
It appears that the c_monocypher.pyx is defined in the singular
'nb_block' for the binding when it should be 'nb_blocks'. After changing
that value to 'nb_blocks', it works as expected:
>>> password = b'123456'
>>> salt = b'00125235'
>>> monocypher.argon2i_32(nb_blocks=100000, nb_iterations=3,
password=password, salt=salt, key=None,
ad=None)
This produces a bytes object as expected:
b'\x8cj\x88\xc7\xda}\x7f\x18Z\x01\xbf\xbb\xd5\x01\x13\xd9<\xb4\xb9\'c\x8f\x98\xee\x96\x04E-\xfc"\xd9o'
mliberty1
approved these changes
Aug 17, 2024
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On line 350 of
c_monocypher.pyxthere is an unconditional call tocrypto_wipe. Starting on line 155 the definition ofwipeincludes a comment that says: "WARNING: this violates the Python memory model and may result in corrupted data. Ensure that the data to wipe is the only active reference!"""While developing a cryptographic protocol that optionally uses very short passwords, we appear to have encountered this issue. We outlined this finding in our comments but we only seem to trigger it for passwords with a length that is less than two bytes: https://codeberg.org/rendezvous/reunion/src/branch/main/reunion/primitives.py#L17 We additionally make a copy of the original password for use over long periods of time.
We would prefer to not corrupt memory for the single password cases in our protocol, if that is indeed happening. We would also prefer not to need to make a copy of the original passphrase to work around this specific use case as erasing the password in memory is problematic for long running protocol runs.
This change optionally allows a caller to avoid
argon2i_32callingwipeorcrypto_wipeinternally by passing the optional value_wipe=Falsewhen usingargon2i_32. By default the original behavior is retained (e.g.:_wipe=Trueandwipeis called byargon2i_32). This change would only impact callers who want to disable wiping.