In cryptography, a "salt" is an extra piece of data which is included when hashing a password. This makes rainbow-table attacks
more
difficult. Using a cryptographic hash function without an unpredictable salt increases the likelihood that an attacker could successfully find the
hash value in databases of precomputed hashes (called rainbow-tables
).
This rule raises an issue when a hashing function which has been specifically designed for hashing passwords, such as PBKDF2
, is used
with a non-random, reused or too short salt value. It does not raise an issue on base hashing algorithms such as sha1
or md5
as they should not be used to hash passwords.
Below, the hashed password use a predictable salt:
byte[] salt = "notrandom".getBytes(); PBEParameterSpec cipherSpec = new PBEParameterSpec(salt, 10000); // Noncompliant, predictable salt PBEKeySpec spec = new PBEKeySpec(chars, salt, 10000, 256); // Noncompliant, predictable salt
Use java.security.SecureRandom
to generate an unpredictable salt:
SecureRandom random = new SecureRandom(); byte[] salt = new byte[16]; random.nextBytes(salt); PBEParameterSpec cipherSpec = new PBEParameterSpec(salt, 10000); // Compliant PBEKeySpec spec = new PBEKeySpec(chars, salt, 10000, 256); // Compliant