Set secure_delete pragma for SQLite3 connections

secure_delete makes SQLite3 overwrite deleted data with zeros, thus actually deleting it from the filesystem.

Ubuntu and FreeBSD enable it by defualt, but some distributions, such as Debian, have it disabled by default, so it is better to set it explicitly.

The performance impact should be negligible as Gajim uses the database rarely.

gajim/common/logger.py

@@ -158,9 +158,15 @@ class Logger:
             self._create(CACHE_SQL_STATEMENT, self._cache_db_path)
 
     @staticmethod
-    def _create(statement, path):
+    def _connect(*args, **kwargs):
+        con = sqlite.connect(*args, **kwargs)
+        con.execute("PRAGMA secure_delete=1")
+        return con
+
+    @classmethod
+    def _create(cls, statement, path):
         log.info(_('Creating %s'), path)
-        con = sqlite.connect(path)
+        con = cls._connect(path)
         os.chmod(path, 0o600)
 
         try:
@@ -181,11 +187,11 @@ class Logger:
 
     def _migrate_databases(self):
         try:
-            con = sqlite.connect(self._log_db_path)
+            con = self._connect(self._log_db_path)
             self._migrate_logs(con)
             con.close()
 
-            con = sqlite.connect(self._cache_db_path)
+            con = self._connect(self._cache_db_path)
             self._migrate_cache(con)
             con.close()
         except Exception:
@@ -272,7 +278,7 @@ class Logger:
         app.ged.raise_event(event, None, str(error))
 
     def _connect_databases(self):
-        self._con = sqlite.connect(
+        self._con = self._connect(
             self._log_db_path, timeout=20.0, isolation_level='IMMEDIATE')
 
         self._con.row_factory = self.namedtuple_factory

gajim/history_manager.py

@@ -131,6 +131,7 @@ class HistoryManager:
 
         self.con = sqlite3.connect(
             log_db_path, timeout=20.0, isolation_level='IMMEDIATE')
+        self.con.execute("PRAGMA secure_delete=1")
         self.cur = self.con.cursor()
 
         self._init_jids_listview()