Execute Immediate within a stored procedure keeps giving insufficient priviliges error

Here is the definition of the stored procedure:

CREATE OR REPLACE PROCEDURE usp_dropTable(schema VARCHAR, tblToDrop VARCHAR) IS
BEGIN
  DECLARE v_cnt NUMBER;
  BEGIN
    SELECT COUNT(*) 
      INTO v_cnt 
      FROM all_tables 
     WHERE owner = schema
       AND table_name = tblToDrop;

     IF v_cnt > 0 THEN 
        EXECUTE IMMEDIATE('DROP TABLE someschema.some_table PURGE');
     END IF;
   END;
END;

Here is the call:

CALL usp_dropTable('SOMESCHEMA', 'SOME_TABLE');

For some reason, I keep getting insufficient privileges error for the EXECUTE IMMEDIATE command. I looked online and found out that the insufficient privileges error usually means the oracle user account does not have privileges for the command used in the query that is passes, which in this case is DROP. However, I have drop privileges. I am really confused and I can't seem to find a solution that works for me.

Thanks to you in advance.

SOLUTION:

As Steve mentioned below, Oracle security model is weird in that it needs to know explicitly somewhere in the procedure what kind of privileges to use. The way to let Oracle know that is to use AUTHID keyword in the CREATE OR REPLACE statement. If you want the same level of privileges as the creator of the procedure, you use AUTHID DEFINER. If you want Oracle to use the privileges of the user currently running the stored procedure, you want to use AUTHID CURRENT_USER. The procedure declaration looks as follows:

CREATE OR REPLACE PROCEDURE usp_dropTable(schema VARCHAR, tblToDrop VARCHAR) 
AUTHID CURRENT_USER IS
BEGIN
  DECLARE v_cnt NUMBER;
  BEGIN
    SELECT COUNT(*) 
      INTO v_cnt 
      FROM all_tables 
     WHERE owner = schema
       AND table_name = tblToDrop;

     IF v_cnt > 0 THEN 
        EXECUTE IMMEDIATE('DROP TABLE someschema.some_table PURGE');
     END IF;
   END;
END;

Thank you everyone for responding. This was definitely very annoying problem to get to the solution.

Oracle's security model is such that when executing dynamic SQL using Execute Immediate (inside the context of a PL/SQL block or procedure), the user does not have privileges to objects or commands that are granted via role membership. Your user likely has "DBA" role or something similar. You must explicitly grant "drop table" permissions to this user. The same would apply if you were trying to select from tables in another schema (such as sys or system) - you would need to grant explicit SELECT privileges on that table to this user.

You should use this example with AUTHID CURRENT_USER :

CREATE OR REPLACE PROCEDURE Create_sequence_for_tab (VAR_TAB_NAME IN VARCHAR2)
   AUTHID CURRENT_USER
IS
   SEQ_NAME       VARCHAR2 (100);
   FINAL_QUERY    VARCHAR2 (100);
   COUNT_NUMBER   NUMBER := 0;
   cur_id         NUMBER;
BEGIN
   SEQ_NAME := 'SEQ_' || VAR_TAB_NAME;

   SELECT COUNT (*)
     INTO COUNT_NUMBER
     FROM USER_SEQUENCES
    WHERE SEQUENCE_NAME = SEQ_NAME;

   DBMS_OUTPUT.PUT_LINE (SEQ_NAME || '>' || COUNT_NUMBER);

   IF COUNT_NUMBER = 0
   THEN
      --DBMS_OUTPUT.PUT_LINE('DROP SEQUENCE ' || SEQ_NAME);
      -- EXECUTE IMMEDIATE 'DROP SEQUENCE ' || SEQ_NAME;
      -- ELSE
      SELECT 'CREATE SEQUENCE COMPTABILITE.' || SEQ_NAME || ' START WITH ' || ROUND (DBMS_RANDOM.VALUE (100000000000, 999999999999), 0) || ' INCREMENT BY 1'
        INTO FINAL_QUERY
        FROM DUAL;

      DBMS_OUTPUT.PUT_LINE (FINAL_QUERY);
      cur_id := DBMS_SQL.OPEN_CURSOR;
      DBMS_SQL.parse (cur_id, FINAL_QUERY, DBMS_SQL.v7);
      DBMS_SQL.CLOSE_CURSOR (cur_id);
   -- EXECUTE IMMEDIATE FINAL_QUERY;

   END IF;

   COMMIT;
END;
/

you could use "AUTHID CURRENT_USER" in body of your procedure definition for your requirements.