Description
The application stores sensitive data in memory that is not locked, or that has been incorrectly locked, which might cause the memory to be written to swap files on disk by the virtual memory manager. This can make the data more accessible to external actors.
On Windows systems the VirtualLock function can lock a page of memory to ensure that it will remain present in memory and not be swapped to disk. However, on older versions of Windows, such as 95, 98, or Me, the VirtualLock() function is only a stub and provides no protection. On POSIX systems the mlock() call ensures that a page will stay resident in memory but does not guarantee that the page will not appear in the swap. Therefore, it is unsuitable for use as a protection mechanism for sensitive data. Some platforms, in particular Linux, do make the guarantee that the page will not be swapped, but this is non-standard and is not portable. Calls to mlock() also require supervisor privilege. Return values for both of these calls must be checked to ensure that the lock operation was actually successful.
Modes of Introduction:
– Implementation
Related Weaknesses
Consequences
Confidentiality: Read Application Data, Read Memory
Sensitive data that is written to a swap file may be exposed.
Potential Mitigations
Phase: Architecture and Design
Description:
Identify data that needs to be protected from swapping and choose platform-appropriate protection mechanisms.
Phase: Implementation
Description:
Check return values to ensure locking operations are successful.