A Pseudo-Random Number Generator (PRNG) is initialized from a predictable seed, such as the process ID or system time.
Extended Description
The use of predictable seeds significantly reduces the number of possible seeds that an attacker would need to test in order to predict which random numbers will be generated by the PRNG.
cloud provider product uses a non-cryptographically secure PRNG and seeds it with the current time
Related Attack Patterns (CAPEC)
N/A
Attack TTPs
N/A
Modes of Introduction
Phase
Note
Implementation
REALIZATION: This weakness is caused during implementation of an architectural security tactic.
Common Consequences
Impact: Varies by Context — Notes:
Potential Mitigations
N/A: Use non-predictable inputs for seed generation. (N/A)
Architecture and Design: Use products or modules that conform to FIPS 140-2 [REF-267] to avoid obvious entropy problems, or use the more recent FIPS 140-3 [REF-1192] if possible. (N/A)
Implementation: Use a PRNG that periodically re-seeds itself using input from high-quality sources, such as hardware devices with high entropy. However, do not re-seed too frequently, or else the entropy source might block. (N/A)
Applicable Platforms
None (Not Language-Specific, Undetermined)
Demonstrative Examples
Intro: Both of these examples use a statistical PRNG seeded with the current value of the system clock to generate a random number:
Body: An attacker can easily predict the seed used by these PRNGs, and so also predict the stream of random numbers generated. Note these examples also exhibit CWE-338 (Use of Cryptographically Weak PRNG).
Random random = new Random(System.currentTimeMillis()); int accountID = random.nextInt();
Notes
Maintenance: 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.