In Bouncy Castle for Java FIPS (BC-FJA) before bc-fips 1.0.2.7 (1.0.X series), 2.0.2 (2.0.X series) and 2.1.3 (2.1.X series), sensitive key material held by the AES and DESede engines, the SP 800-90A DRBGs, SymmetricSecretKey and the PBKD and scrypt parameter classes was zeroised on garbage collection by overriding Object.finalize. Finalization runs at an unspecified time and in an unspecified order and is serviced by a single finalizer thread, so where objects carrying a finalizer are allocated faster than that thread retires them the pending-finalization queue grows without bound: disposal falls arbitrarily far behind, which can contribute to an OutOfMemoryError under load, and the key material those objects hold stays resident in the heap for as long as they are queued, defeating the purpose of the zeroisation. The behaviour was not a problem on Java 8 or Java 11; it is later JVMs, on which finalization has been deprecated and progressively de-emphasised, where it becomes one. Disposal of these classes now runs from a java.lang.ref.Cleaner registered in the multi-release jdk1.9 overlay, so on Java 9 and later it no longer depends on the finalizer being scheduled. Bouncy Castle for Java (bcprov) and Bouncy Castle for Java LTS are not affected, as neither implements the finalizer-based zeroisation scheme.
Weakness
The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.
Potential Mitigations
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
- For example, languages such as Java, Ruby, and Lisp perform automatic garbage collection that releases memory for objects that have been deallocated.
- Use resource-limiting settings provided by the operating system or environment. For example, when managing system resources in POSIX, setrlimit() can be used to set limits for certain types of resources, and getrlimit() can determine how many resources are available. However, these functions are not available on all operating systems.
- When the current levels get close to the maximum that is defined for the application (see CWE-770), then limit the allocation of further resources to privileged users; alternately, begin releasing resources for less-privileged users. While this mitigation may protect the system from attack, it will not necessarily stop attackers from adversely impacting other users.
- Ensure that the application performs the appropriate error checks and error handling in case resources become unavailable (CWE-703).