Metadata

ID: kotlin-security/no-pseudo-random

Language: Kotlin

Severity: Error

Category: Security

CWE: 330

Description

This rule enforces the use of secure and unpredictable random numbers in Kotlin applications. Using pseudo-random numbers can make your code vulnerable to attacks because pseudo-random numbers follow a deterministic sequence that can be predicted if the initial seed is known. This is especially crucial in contexts such as generating encryption keys, generating random identifiers, or performing any other security-related functionalities.

To adhere to this rule, avoid using SecureRandom with a fixed seed using the setSeed() method or passing a byte array to the SecureRandom constructor. Both of these methods produce pseudo-random numbers, which can lead to vulnerabilities in your code. Also, avoid reseeding a SecureRandom instance with a predictable value, such as the current time.

Instead, create a SecureRandom instance without a set seed, or use SecureRandom.getInstanceStrong(). Following these best practices helps you generate secure and unpredictable random numbers in your Kotlin applications.

Non-Compliant Code Examples

import java.security.SecureRandom

// Setting a fixed numeric seed
val random1 = SecureRandom()
random1.setSeed(123456L)  // Noncompliant

// Setting a fixed string seed
val random2 = SecureRandom("myseed".toByteArray())  // Noncompliant

// Reseeding with predictable value
val random3 = SecureRandom()
val time = System.currentTimeMillis()
random3.setSeed(time)  // Noncompliant: timestamp is predictable

Compliant Code Examples

import java.security.SecureRandom

// Let SecureRandom choose its own seed
val random1 = SecureRandom()
val bytes = random1.nextBytes(32)

// Use strong instance (preferred)
val random2 = SecureRandom.getInstanceStrong()
val number = random2.nextInt()

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