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Sonar: Secure Source of Randomness


ImportanceReview GuidanceRequires Scanning Tool
HighMerge After Cursory ReviewYes (Sonar)

This codemod acts upon the following Sonar rules: python:S2245.

This codemod replaces all instances of functions in the random module (e.g. random.random() with their, much more secure, equivalents from the secrets module (e.g. secrets.SystemRandom().random()).

There is significant algorithmic complexity in getting computers to generate genuinely unguessable random bits. The random.random() function uses a method of pseudo-random number generation that unfortunately emits fairly predictable numbers.

If the numbers it emits are predictable, then it's obviously not safe to use in cryptographic operations, file name creation, token construction, password generation, and anything else that's related to security. In fact, it may affect security even if it's not directly obvious.

Switching to a more secure version is simple and the changes look something like this:

- import random
+ import secrets
- random.random()
+ secrets.SystemRandom().random()

If you have feedback on this codemod, please let us know!


Why is this codemod marked as Merge After Cursory Review?

While most of the functions in the random module aren't cryptographically secure, there are still valid use cases for random.random() such as for simulations or games.

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