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hashlib-insecure-hash-function (S324)#

Derived from the flake8-bandit linter.

What it does#

Checks for uses of weak or broken cryptographic hash functions.

Why is this bad?#

Weak or broken cryptographic hash functions may be susceptible to collision attacks (where two different inputs produce the same hash) or pre-image attacks (where an attacker can find an input that produces a given hash). This can lead to security vulnerabilities in applications that rely on these hash functions.

Avoid using weak or broken cryptographic hash functions in security contexts. Instead, use a known secure hash function such as SHA256.

Example#

import hashlib


def certificate_is_valid(certificate: bytes, known_hash: str) -> bool:
    hash = hashlib.md5(certificate).hexdigest()
    return hash == known_hash

Use instead: 

import hashlib


def certificate_is_valid(certificate: bytes, known_hash: str) -> bool:
    hash = hashlib.sha256(certificate).hexdigest()
    return hash == known_hash

References#