Enable compile-time flag SQLITE_ENABLE_DBPAGE_VTAB to add support for .recover shell option.

Signed-off-by: DL6ER <dl6er@dl6er.de>

src/CMakeLists.txt

@@ -26,7 +26,8 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR})
 # SQLITE_OMIT_PROGRESS_CALLBACK: The progress handler callback counter must be checked in the inner loop of the bytecode engine. By omitting this interface, a single conditional is removed from the inner loop of the bytecode engine, helping SQL statements to run slightly faster.
 # SQLITE_DEFAULT_FOREIGN_KEYS=1: This macro determines whether enforcement of foreign key constraints is enabled or disabled by default for new database connections.
 # SQLITE_DQS=0: This setting disables the double-quoted string literal misfeature.
-set(SQLITE_DEFINES "-DSQLITE_OMIT_LOAD_EXTENSION -DSQLITE_DEFAULT_MEMSTATUS=0 -DSQLITE_OMIT_DEPRECATED -DSQLITE_OMIT_PROGRESS_CALLBACK -DSQLITE_DEFAULT_FOREIGN_KEYS=1 -DSQLITE_DQS=0")
+# SQLITE_ENABLE_DBPAGE_VTAB: Enables the SQLITE_DBPAGE virtual table. Warning: writing to the SQLITE_DBPAGE virtual table can very easily cause unrecoverably database corruption.
+set(SQLITE_DEFINES "-DSQLITE_OMIT_LOAD_EXTENSION -DSQLITE_DEFAULT_MEMSTATUS=0 -DSQLITE_OMIT_DEPRECATED -DSQLITE_OMIT_PROGRESS_CALLBACK -DSQLITE_DEFAULT_FOREIGN_KEYS=1 -DSQLITE_DQS=0 -DSQLITE_ENABLE_DBPAGE_VTAB")
 
 # Code hardening and debugging improvements
 # -fstack-protector-strong: The program will be resistant to having its stack overflowed

src/database/common.c

@@ -193,6 +193,17 @@ void db_init(void)
 	// explicitly check for failures to have happened
 	sqlite3_config(SQLITE_CONFIG_LOG, SQLite3LogCallback, NULL);
 
+	// SQLITE_DBCONFIG_DEFENSIVE
+	// Disbale language features that allow ordinary SQL to deliberately corrupt
+	// the database file. The disabled features include but are not limited to
+	// the following:
+	//
+	// - The PRAGMA writable_schema=ON statement.
+	// - The PRAGMA journal_mode=OFF statement.
+	// - Writes to the sqlite_dbpage virtual table.
+	// - Direct writes to shadow tables.
+	sqlite3_config(SQLITE_DBCONFIG_DEFENSIVE, true);
+
 	// Register Pi-hole provided SQLite3 extensions (see sqlite3-ext.c)
 	sqlite3_auto_extension((void (*)(void))sqlite3_pihole_extensions_init);