2.0 KiB
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 DELETEauto_vacuum = FULL: freed pages are reclaimed immediatelyforeign_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 pgcrypto's digest() function for MD5 and a custom xor_combine PL/pgSQL function for the XOR.
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 if keepKey is true or if the key is empty (no encryption). This means unencrypted stores can always be reopened. If keepKey is false and the key is non-empty, reopenDBStore fails with "no key".
dbBusyLoop — initial connection retry
connectSQLiteStore wraps connectDB in dbBusyLoop to handle database locking during initial connection. All transactions (withTransactionPriority) are also wrapped in dbBusyLoop as a retry layer on top of the busy_timeout PRAGMA.