JHipster Kotlin using insecure source of randomness `RandomStringUtils` before v1.2.0

JHipster Kotlin is using an insecure source of randomness to generate all of its random values. JHipster Kotlin relies upon apache commons lang3 RandomStringUtils.

From the documentation:

> Caveat: Instances of Random, upon which the implementation of this class relies, are not cryptographically secure.
> - https://commons.apache.org/proper/commons-lang/javadocs/api-3.9/org/apache/commons/lang3/RandomStringUtils.html

Here are the examples of JHipster Kotlin's use of an insecure PRNG:

https://github.com/jhipster/jhipster-kotlin/blob/193ae8f13c0be686f9687e78bacfedb144c47d8c/generators/server/templates/src/main/kotlin/package/service/util/RandomUtil.kt.ejs#L32

Proof Of Concepts Already Exist

There has been a POC of taking one RNG value generated RandomStringUtils and reversing it to generate all of the past/future RNG values public since March 3rd, 2018.

https://medium.com/@alex91ar/the-java-soothsayer-a-practical-application-for-insecure-randomness-c67b0cd148cd

POC Repository: https://github.com/alex91ar/randomstringutils

Potential Impact Technical

All that is required is to get one password reset token from a JHipster Kotlin generated service and using the POC above, you can reverse what all future password reset tokens to be generated by this server. This allows an attacker to pick and choose what account they would like to takeover by sending account password reset requests for targeted accounts.

Potential Impact Scale

Not as large as for the original jhipster project as the kotlin blueprint is not that widely used.

Patches

Update your generated applications to > 1.2.0

Workarounds

Change the content of RandomUtil.kt like this:

import java.security.SecureRandom
import org.apache.commons.lang3.RandomStringUtils

private const val DEF_COUNT = 20

object RandomUtil {
    private val secureRandom: SecureRandom = SecureRandom()

    init {
        secureRandom.nextBytes(byteArrayOf(64.toByte()))
    }

    private fun generateRandomAlphanumericString(): String {
        return RandomStringUtils.random(DEF_COUNT, 0, 0, true, true, null, secureRandom)
    }

    /**
    * Generate a password.
    *
    * @return the generated password.
    */
    fun generatePassword(): String = generateRandomAlphanumericString()
}

Important is to exchange every call of RandomStringUtils.randomAlphaNumeric.

For more information

If you have any questions or comments about this advisory:
* Open an issue in JHipster Kotlin