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DescriptionChristian Heimes
2023-02-22 09:21:49 UTC
This bug was initially created as a copy of Bug #2171817
cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. In affected versions `Cipher.update_into` would accept Python objects which implement the buffer protocol, but provide only immutable buffers. This would allow immutable objects (such as `bytes`) to be mutated, thus violating fundamental rules of Python and resulting in corrupted output. This now correctly raises an exception. This issue has been present since `update_into` was originally introduced in cryptography 1.8.
Verified manually on RHEL9.3 nightly machine with python3-cffi-1.14.5-5.el9.x86_64 and python3-cryptography-36.0.1-3.el9.x86_64
# python3
Python 3.9.16 (main, Dec 8 2022, 00:00:00)
[GCC 11.3.1 20221121 (Red Hat 11.3.1-4)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
>>> c = Cipher(algorithms.AES(os.urandom(16)), modes.ECB())
>>> encryptor = c.encryptor()
>>> buf = b"\x00" * 32
>>> encryptor.update_into(b"\xff" * 16, buf)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib64/python3.9/site-packages/cryptography/hazmat/primitives/ciphers/base.py", line 128, in update_into
return self._ctx.update_into(data, buf)
File "/usr/lib64/python3.9/site-packages/cryptography/hazmat/backends/openssl/ciphers.py", line 158, in update_into
baseoutbuf = self._backend._ffi.from_buffer(buf, require_writable=True)
BufferError: Object is not writable.
>>> buf == b"\x00" * 32
True
Marking as verified.
Comment 23Florence Blanc-Renaud
2023-07-31 13:16:10 UTC
*** Bug 2175093 has been marked as a duplicate of this bug. ***
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory (Moderate: python-cryptography security update), and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2023:6615