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Description
The lack of entropy available for, or used by, a Pseudo-Random Number Generator (PRNG) can be a stability and security threat.
Modes of Introduction:
– Architecture and Design
Likelihood of Exploit: Medium
Related Weaknesses
CWE-331
Consequences
Availability: DoS: Crash, Exit, or Restart
If a pseudo-random number generator is using a limited entropy source which runs out (if the generator fails closed), the program may pause or crash.
Access Control, Other: Bypass Protection Mechanism, Other
If a PRNG is using a limited entropy source which runs out, and the generator fails open, the generator could produce predictable random numbers. Potentially a weak source of random numbers could weaken the encryption method used for authentication of users.
Potential Mitigations
Phase: Architecture and Design, Requirements
Description:
Use products or modules that conform to FIPS 140-2 [REF-267] to avoid obvious entropy problems. Consult FIPS 140-2 Annex C (“Approved Random Number Generators”).
Phase: Implementation
Description:
Consider a PRNG that re-seeds itself as needed from high-quality pseudo-random output, such as hardware devices.
Phase: Architecture and Design
Description:
When deciding which PRNG to use, look at its sources of entropy. Depending on what your security needs are, you may need to use a random number generator that always uses strong random data — i.e., a random number generator that attempts to be strong but will fail in a weak way or will always provide some middle ground of protection through techniques like re-seeding. Generally, something that always provides a predictable amount of strength is preferable.
CVE References
- CVE-2019-1715
- security product has insufficient entropy in the DRBG, allowing collisions and private key discovery
