|Oracle8i Supplied PL/SQL Packages Reference
Release 2 (8.1.6)
Part Number A76936-01
DBMS_RLS package contains the fine-grained access control administrative interface.
The functionality to support fine-grained access control is based on dynamic predicates, where security rules are not embedded in views, but are acquired at the statement parse time, when the base table or view is referenced in a DML statement.
A dynamic predicate for a table or view is generated by a PL/SQL function, which is associated with a security policy through a PL/SQL interface. For example:
EMP table, under
SCOTT schema, is referenced in a query or subquery (
SELECT), the server calls the
EMP_SEC function (under
SECUSR schema). This returns a predicate specific to the current user for the
EMP_POLICY policy. The policy function may generate the predicates based on whatever session environment variables are available during the function call. These variables usually appear in the form of application contexts.
The server then produces a transient view with the text:
SAL > 10000, or even a subquery) is the predicate returned from the
EMP_SEC function. The server treats the
EMP table as a view and does the view expansion just like the ordinary view, except that the view text is taken from the transient view instead of the data dictionary.
If the predicate contains subqueries, then the owner (definer) of the policy function is used to resolve objects within the subqueries and checks security for those objects. In other words, users who have access privilege to the policy protected objects do not need to know anything about the policy. They do not need to be granted object privileges for any underlying security policy. Furthermore, the users also do not require
EXECUTE privilege on the policy function, because the server makes the call with the function definer's right.
DBMS_RLS package also provides the interface to drop and enable/disable security policies. For example, you can drop or disable the
EMP_POLICY with the following PL/SQL statements:
DBMS_RLS.DROP_POLICY('scott', 'emp', 'emp_policy'); DBMS_RLS.ENABLE_POLICY('scott', 'emp', 'emp_policy', FALSE)
A security check is performed when the transient view is created with subquery. The schema owning the policy function, which generates the dynamic predicate, is the transient view's definer for the purpose of security check and object look-up.
DBMS_RLS procedures cause current DML transactions, if any, to commit before the operation. However, the procedures do not cause a commit first if they are inside a DDL event trigger. With DDL transactions, the
DBMS_RLS procedures are part of the DDL transaction.
For example, you may create a trigger for
TABLE. Inside the trigger, you may add a column through
TABLE, and you can add a policy through
DBMS_RLS. All these operations are in the same transaction as
TABLE, even though each one is a DDL statement. The
TABLE succeeds only if the trigger is completed successfully.