Usage of Insecure SHA1 Hash Algorithm

[sec1-security]

WeasyPrint/weasyprint/text/fonts.py

Line 124 in b195aab

config_key = sha1((

The above code utilizes the SHA1 hash algorithm to generate a configuration key. However, SHA1 is considered insecure and is not recommended for use as a cryptographic signature or hash function. The vulnerability arises from the following line of code:
config_key = sha1((
f'{rule_descriptors["font_family"]}-{fontconfig_style}-'
f'{fontconfig_weight}-{features_string}').encode()).hexdigest()

SHA1 has been proven to be vulnerable to collision attacks, where two different inputs can produce the same hash value. This weakness can be exploited by attackers to forge digital signatures, bypass integrity checks, or manipulate data without detection.

Impact:
The use of SHA1 in cryptographic operations poses a security risk. Attackers can potentially exploit the collision vulnerability to:

Forge digital signatures, allowing unauthorized modifications or tampering of data.
Bypass integrity checks, undermining the trust in the integrity of the hashed data.
Create collisions in hash-based identifiers or keys, leading to potential security breaches.
The severity of the impact depends on how the generated configuration key is used and the sensitivity of the data or operations relying on it.

Recommendation:
To mitigate this vulnerability, it is strongly recommended to replace the SHA1 hash algorithm with a more secure alternative. Consider the following options:

Use SHA256 or SHA3 (e.g., SHA3-256) as they provide stronger collision resistance and are considered cryptographically secure.
If a shorter hash digest is required, consider using a truncated version of SHA256 or SHA3 instead of SHA1.
For digital signatures, use asymmetric cryptographic algorithms like RSA or ECDSA with appropriate key lengths.
Regularly update and patch the cryptographic libraries and dependencies to ensure protection against known vulnerabilities.
By transitioning to a secure hash algorithm and following cryptographic best practices, the risk associated with using SHA1 can be effectively mitigated.

References:
NIST: Transitioning the Use of Cryptographic Algorithms and Key Lengths https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-131Ar2.pdf
OWASP: Insecure Cryptographic Storage https://owasp.org/www-project-top-ten/2017/A3_2017-Sensitive_Data_Exposure

[liZe]

This key is not used for security purpose. There’s no problem here.