Implement padding control for crypto

[skelsec]

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I am submitting a …

• [ ] bug report
• [x] feature request

Description

Currently all symmetric block ciphers default to the padding whichever one was set in mbedtls at compilation time. Because it's by default not MBEDTLS_PADDING_NONE the current setup excludes many usecases for the ciphers.

Current behavior

As I see currently it's using MBEDTLS_PADDING_PKCS7.

Expected behavior

Either default to MBEDTLS_PADDING_NONE and have the user's implement padding on their own, or expose the mbedtls_cipher_set_padding_mode to the user. (NOTE: should be applied to both encryption and decryption context a the same time)

Steps to reproduce

Minimal demo of the problem

Other information

[Synss]

or expose the mbedtls_cipher_set_padding_mode to the user.

Is probably easier.

Passing callbacks from Python to C is possible but I prefer to avoid that as much as possible.

[Synss]

I changed my mind. Users can use

• https://pypi.org/project/PyPadding/ or

• https://pycryptodome.readthedocs.io/en/latest/src/util/util.html#crypto-util-padding-module

  for padding.

I will default to NONE.

[skelsec]

Works for me, please let me know when the code is updated

[Synss]

It is done.