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Rust: Add .qhelp.
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‎rust/ql/src/queries/security/CWE-328/WeakSensitiveDataHashing.qhelp

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<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>
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Using a broken or weak cryptographic hash function can leave data
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vulnerable, and should not be used in security related code.
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</p>
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<p>
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A strong cryptographic hash function should be resistant to:
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</p>
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<ul>
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<li>
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<b>Pre-image attacks</b>. If you know a hash value <code>h(x)</code>,
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you should not be able to easily find the input <code>x</code>.
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</li>
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<li>
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<b>Collision attacks</b>. If you know a hash value <code>h(x)</code>,
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you should not be able to easily find a different input
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<code>y</code>
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with the same hash value <code>h(x) = h(y)</code>.
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</li>
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<li>
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<b>Brute force</b>. For passwords and other data with limited
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input space, if you know a hash value <code>h(x)</code>
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you should not be able to find the input <code>x</code> even using
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a brute force attack (without significant computational effort).
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</li>
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</ul>
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<p>
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As an example, both MD5 and SHA-1 are known to be vulnerable to collision attacks.
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</p>
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<p>
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All of MD5, SHA-1, SHA-2 and SHA-3 are weak against offline brute forcing, so
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they are not suitable for hashing passwords. This includes SHA-224, SHA-256,
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SHA-384 and SHA-512, which are in the SHA-2 family.
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</p>
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<p>
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Since it's OK to use a weak cryptographic hash function in a non-security
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context, this query only alerts when these are used to hash sensitive
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data (such as passwords, certificates, usernames).
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</p>
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</overview>
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<recommendation>
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<p>
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Ensure that you use a strong, modern cryptographic hash function, such as:
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</p>
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<ul>
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<li>
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Argon2, scrypt, bcrypt, or PBKDF2 for passwords and other data with limited input space where
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a dictionary-like attack is feasible.
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</li>
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<li>
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SHA-2, or SHA-3 in other cases.
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</li>
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</ul>
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<p>
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Note that special purpose algorithms, which are used to ensure that a message comes from a
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particular sender, exist for message authentication. These algorithms should be used when
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appropriate, as they address common vulnerabilities of simple hashing schemes in this context.
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</p>
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</recommendation>
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<example>
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<p>
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The following examples show hashing sensitive data using the MD5 hashing algorithm that is known to be
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vulnerable to collision attacks, and hashing passwords using the SHA-3 algorithm that is weak to brute
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force attacks:
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</p>
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<sample src="WeakSensitiveDataHashingBad.rs"/>
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<p>
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To make these secure, we can use the SHA-3 algorithm for sensitive data and Argon2 for passwords:
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</p>
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<sample src="WeakSensitiveDataHashingGood.rs"/>
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</example>
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<references>
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<li>
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OWASP:
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<a href="https://cheatsheetseries.owasp.org/cheatsheets/Password_Storage_Cheat_Sheet.html">
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Password Storage Cheat Sheet
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</a>
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and
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<a href="https://cheatsheetseries.owasp.org/cheatsheets/Transport_Layer_Security_Cheat_Sheet.html">
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Transport Layer Security Cheat Sheet
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</a>
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GitHub:
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<a href="https://github.com/RustCrypto/hashes?tab=readme-ov-file#rustcrypto-hashes">
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RustCrypto: Hashes
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</a>
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and
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<a href="https://github.com/RustCrypto/password-hashes?tab=readme-ov-file#rustcrypto-password-hashes">
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RustCrypto: Password Hashes
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</a>
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</li>
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</references>
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</qhelp>

‎rust/ql/src/queries/security/CWE-328/WeakSensitiveDataHashingBad.rs

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// MD5 is not appropriate for hashing sensitive data.
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let mut md5_hasher = md5::Md5::new();
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...
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md5_hasher.update(emergency_contact); // BAD
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md5_hasher.update(credit_card_no); // BAD
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...
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my_hash = md5_hasher.finalize();
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// SHA3-256 is not appropriate for hashing passwords.
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my_hash = sha3::Sha3_256::digest(password); // BAD

‎rust/ql/src/queries/security/CWE-328/WeakSensitiveDataHashingGood.rs

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// SHA3-256 *is* appropriate for hashing sensitive data.
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let mut sha3_256_hasher = sha3::Sha3_256::new();
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...
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sha3_256_hasher.update(emergency_contact); // GOOD
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sha3_256_hasher.update(credit_card_no); // GOOD
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...
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my_hash = sha3_256_hasher.finalize();
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// Argon2 is appropriate for hashing passwords.
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let argon2_salt = argon2::password_hash::Salt::from_b64(salt)?;
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my_hash = argon2::Argon2::default().hash_password(password.as_bytes(), argon2_salt)?.to_string(); // GOOD

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