SQLite3::setAuthorizer

Descrierea

Sets a callback that will be called by SQLite every time an action is performed (reading, deleting, updating, etc.). This is used when preparing a SQL statement from an untrusted source to ensure that the SQL statements do not try to access data they are not allowed to see, or that they do not try to execute malicious statements that damage the database. For example, an application may allow a user to enter arbitrary SQL queries for evaluation by a database. But the application does not want the user to be able to make arbitrary changes to the database. An authorizer could then be put in place while the user-entered SQL is being prepared that disallows everything except SELECT statements.

The authorizer callback may be called multiple times for each statement prepared by SQLite. A SELECT or UPDATE query will call the authorizer for every column that would be read or updated.

The authorizer is called with up to five parameters. The first parameter is always given, and is an int (action code) matching a constant from SQLite3. The other parameters are only passed for some actions. The following table describes the second and third parameters according to the action:

List of action codes and parameters

Action	Second parameter	Third parameter
SQLite3::CREATE_INDEX	Index Name	Table Name
SQLite3::CREATE_TABLE	Table Name	null
SQLite3::CREATE_TEMP_INDEX	Index Name	Table Name
SQLite3::CREATE_TEMP_TABLE	Table Name	null
SQLite3::CREATE_TEMP_TRIGGER	Trigger Name	Table Name
SQLite3::CREATE_TEMP_VIEW	View Name	null
SQLite3::CREATE_TRIGGER	Trigger Name	Table Name
SQLite3::CREATE_VIEW	View Name	null
SQLite3::DELETE	Table Name	null
SQLite3::DROP_INDEX	Index Name	Table Name
SQLite3::DROP_TABLE	Table Name	null
SQLite3::DROP_TEMP_INDEX	Index Name	Table Name
SQLite3::DROP_TEMP_TABLE	Table Name	null
SQLite3::DROP_TEMP_TRIGGER	Trigger Name	Table Name
SQLite3::DROP_TEMP_VIEW	View Name	null
SQLite3::DROP_TRIGGER	Trigger Name	Table Name
SQLite3::DROP_VIEW	View Name	null
SQLite3::INSERT	Table Name	null
SQLite3::PRAGMA	Pragma Name	First argument passed to the pragma, or null
SQLite3::READ	Table Name	Column Name
SQLite3::SELECT	null	null
SQLite3::TRANSACTION	Operation	null
SQLite3::UPDATE	Table Name	Column Name
SQLite3::ATTACH	Filename	null
SQLite3::DETACH	Database Name	null
SQLite3::ALTER_TABLE	Database Name	Table Name
SQLite3::REINDEX	Index Name	null
SQLite3::ANALYZE	Table Name	null
SQLite3::CREATE_VTABLE	Table Name	Module Name
SQLite3::DROP_VTABLE	Table Name	Module Name
SQLite3::FUNCTION	null	Function Name
SQLite3::SAVEPOINT	Operation	Savepoint Name
SQLite3::RECURSIVE	null	null

The 5th parameter will be the name of the database ("main", "temp", etc.) if applicable.

The 6th parameter to the authorizer callback is the name of the inner-most trigger or view that is responsible for the access attempt or null if this access attempt is directly from top-level SQL code.

When the callback returns SQLite3::OK, that means the operation requested is accepted. When the callback returns SQLite3::DENY, the call that triggered the authorizer will fail with an error message explaining that access is denied.

If the action code is SQLite3::READ and the callback returns SQLite3::IGNORE then the prepared statement statement is constructed to substitute a null value in place of the table column that would have been read if SQLite3::OK had been returned. The SQLite3::IGNORE return can be used to deny an untrusted user access to individual columns of a table.

When a table is referenced by a SELECT but no column values are extracted from that table (for example in a query like "SELECT count(*) FROM table") then the SQLite3::READ authorizer callback is invoked once for that table with a column name that is an empty string.

If the action code is SQLite3::DELETE and the callback returns SQLite3::IGNORE then the DELETE operation proceeds but the truncate optimization is disabled and all rows are deleted individually.

Only a single authorizer can be in place on a database connection at a time. Each call to SQLite3::setAuthorizer() overrides the previous call. Disable the authorizer by installing a null callback. The authorizer is disabled by default.

The authorizer callback must not do anything that will modify the database connection that invoked the authorizer callback.

Note that the authorizer is only called when a statement is prepared, not when it's executed.

More details can be found in the » SQLite3 documentation.

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