Insufficient Entropy in PRNG

Opis

The lack of entropy available for, or used by, a Pseudo-Random Number Generator (PRNG) can be a stability and security threat.

Skutki

• 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.

Zapobieganie

• Architecture and Design, Requirements · Libraries or Frameworks

  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").

• Implementation

  Consider a PRNG that re-seeds itself as needed from high-quality pseudo-random output, such as hardware devices.

• Architecture and Design

  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.

Przykłady podatności

• CVE-2019-1715 security product has insufficient entropy in the DRBG, allowing collisions and private key discovery

Słabość nadrzędna

• CWE-331 Insufficient Entropy

Kiedy powstaje

• Architecture and Design
• Implementation — REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Dotyczy

Not Language-Specific

Uwagi

As of CWE 4.5, terminology related to randomness, entropy, and predictability can vary widely. Within the developer and other communities, "randomness" is used heavily. However, within cryptography, "entropy" is distinct, typically implied as a measurement. There are no commonly-used definitions, even within standards documents and cryptography papers. Future versions of CWE will attempt to define these terms and, if necessary, distinguish between them in ways that are appropriate for different communities but do not reduce the usability of CWE for mapping, understanding, or other scenarios.

Źródła

1. FIPS PUB 140-2: SECURITY REQUIREMENTS FOR CRYPTOGRAPHIC MODULES — Information Technology Laboratory, National Institute of Standards and Technology, 2001
2. The CLASP Application Security Process — Secure Software, Inc., 2005
3. Randstorm: You Can't Patch a House of Cards — Unciphered, 2023