[Cryptography-dev] cryptography 36.0.1 Fernet example: AES in CBC mode UnsupportedAlgorithm

[ejanssen at itmatters.nl]

Hi,

This is maybe not a cryptography question but an openssl one, please 
bear with me..

I compiled openssl 1.1.1m myself and installed it next to the existing 
1.0.1t from my distribution (debian 8). I built a Python linking against 
this new openssl.

When I try the example code from the documentation I get 
UnsupportedAlgorithm:

$ python3 -i
Python 3.9.10 (main, Jan 19 2022, 14:33:07)
[GCC 4.9.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import cryptography.hazmat.backends.openssl.backend as b

>>> b.openssl_version_text()
'OpenSSL 1.1.1m  14 Dec 2021'

>>> '{:x}'.format(b.openssl_version_number())
'101010df'

>>> from cryptography.fernet import Fernet
>>> key = Fernet.generate_key()
>>> f = Fernet(key)
>>> token = f.encrypt(b"my deep dark secret")
Traceback (most recent call last):

<skipping parts>

     raise UnsupportedAlgorithm(msg, _Reasons.UNSUPPORTED_CIPHER)
cryptography.exceptions.UnsupportedAlgorithm: cipher AES in CBC mode is 
not supported by this backend (Your version of OpenSSL may be too old. 
Current version: OpenSSL 1.1.1m  14 Dec 2021.)


However, I can do this on the commandline:

$ openssl version
OpenSSL 1.1.1m  14 Dec 2021

$ openssl enc -aes128 -base64 -in text.plain -out text.enc
enter aes-128-cbc encryption password:
Verifying - enter aes-128-cbc encryption password:
*** WARNING : deprecated key derivation used.
Using -iter or -pbkdf2 would be better.

$ cat text.enc
U2FsdGVkX18dFTIizaI1vyR/zo26kRa6ZusV61GMYZ8=

This didn't work initially, I first had to align openssl.cnf with the 
one from the distribution. But now I would say the openssl itself is 
working.

Why is this not working in the cryptography module? Or/and, what would 
be the best next step to analyse?


Thanks!

Erik