SQLite WAL mode auxiliary file permission inheritance

Database Access Control in WAL Mode

SQLite relies on the host operating system's file system permissions to prevent unauthorized access, as it lacks internal user authentication. When the database is configured with PRAGMA journal_mode=WAL;, SQLite creates two auxiliary files: the Write-Ahead Log (-wal) and the shared memory file (-shm).

A security concern arises regarding the creation of these files during the transition from the default rollback journal to WAL mode. If the main database file has strict OS-level permissions, it is unclear if the automatically generated -wal and -shm files consistently inherit those same restrictive permissions or if they are created with default system masks (umask) that could potentially allow broader access.

Given that these auxiliary files contain active database changes and state, ensuring they are not world-readable is critical for preventing data exposure.

• Does SQLite guarantee that -wal and -shm files inherit the exact permission bits of the primary database file upon creation?
• In environments with strict ACLs, is manual permission synchronization required after enabling WAL mode?