Using pseudorandom number generators (PRNGs) is security-sensitive. For example, it has led in the past to the following vulnerabilities:
When software generates predictable values in a context requiring unpredictability, it may be possible for an attacker to guess the next value that
will be generated, and use this guess to impersonate another user or access sensitive information.
As the java.util.Random class relies on a pseudorandom number generator, this class and relating java.lang.Math.random()
method should not be used for security-critical applications or for protecting sensitive data. In such context, the
java.security.SecureRandom class which relies on a cryptographically strong random number generator (RNG) should be used in place.
Ask Yourself Whether
- the code using the generated value requires it to be unpredictable. It is the case for all encryption mechanisms or when a secret value, such
as a password, is hashed.
- the function you use generates a value which can be predicted (pseudo-random).
- the generated value is used multiple times.
- an attacker can access the generated value.
There is a risk if you answered yes to any of those questions.
Recommended Secure Coding Practices
- Use a cryptographically strong random number generator (RNG) like "java.security.SecureRandom" in place of this PRNG.
- Use the generated random values only once.
- You should not expose the generated random value. If you have to store it, make sure that the database or file is secure.
Sensitive Code Example
Random random = new Random(); // Sensitive use of Random
byte bytes[] = new byte[20];
random.nextBytes(bytes); // Check if bytes is used for hashing, encryption, etc...
Compliant Solution
SecureRandom random = new SecureRandom(); // Compliant for security-sensitive use cases
byte bytes[] = new byte[20];
random.nextBytes(bytes);
See
