simplexmq/spec/modules/Simplex/Messaging/Agent/Store/SQLite.md

Simplex.Messaging.Agent.Store.SQLite

SQLite backend — store creation, encrypted connection management, migration, and custom SQL functions.

Source: Agent/Store/SQLite.hs

Security-relevant PRAGMAs

connectDB sets PRAGMAs at connection time:

• secure_delete = ON: data is overwritten (not just unlinked) on DELETE
• auto_vacuum = FULL: freed pages are reclaimed immediately
• foreign_keys = ON: referential integrity enforced

These are set per-connection, not per-database — every new connection (including re-opens) gets them.

simplex_xor_md5_combine — custom SQLite function

A C-exported SQLite function registered at connection time. Takes an existing IdsHash and a RecipientId, XORs the hash with the MD5 of the ID. This is the SQLite implementation of the accumulative IdsHash used by service subscriptions (see TSessionSubs.md). PostgreSQL uses its native md5() and decode() functions instead.

openSQLiteStore_ — connection swap under MVar

Uses bracketOnError with takeMVar/tryPutMVar: takes the connection MVar, creates a new connection, and puts the new one back. If connection fails, tryPutMVar restores the old connection. The dbClosed TVar is flipped atomically with the key update.

storeKey — conditional key retention

storeKey key keepKey stores the encryption key in the dbKey TVar only if keepKey is true. This allows reopenDBStore to re-open without the caller re-supplying the key. If keepKey is false and the store is closed, reopenDBStore fails with "no key".