Raise application error in a stored procedure when inputs contain keywords like 'delete' , 'insert','update'

Question

I have a Stored Procedure which gets 6 input queries and the inputs are the same as where clause of a query. For instance where x=1 and z=5 and e=4. The Application makes these input strings and pass it onto my procedure.This is a part of my procedure in which I'm checking the inputs in order to validate the content of each input query so that they do not contain keywords like "select", "update", "delete" or equivalents.I want to know whether there are better ways to do that.
create or replace procedure app_error_test(query1 nvarchar2,
                                           query2 nvarchar2,
                                           query3 nvarchar2,
                                           query4 nvarchar2,
                                           query5 nvarchar2,
                                           query6 nvarchar2) is
queryconcat nvarchar2(30000);
begin

--**************** validate content of input queries

queryconcat := lower(nvl(query1, '') || nvl(query2, '') ||
                     nvl(query3, '') || nvl(query4, '') ||
                     nvl(query5, '') || nvl(query6, ''));

if (queryconcat like '%drop%' or 
      queryconcat like '%delete%' or
       queryconcat like '%execute%' or 
        queryconcat like '%truncate%' or
         queryconcat like '%create%'  or 
          queryconcat like '%update%'  or
           queryconcat like '%insert%') then

RAISE_APPLICATION_ERROR(-20032, 'ILLEGAL CONTENT');
  end if;
end;

Thanks in advance

William Robertson · Answer

I would use regex_like:
select column_value
     , case
           when regexp_like(' '||column_value||' ','s(drop|execute|truncate|create|insert|update|delete|merge)s', 'i')
               then 'Yes'
       end as illegal
from   table(ora_mining_varchar2_nt
             ('drop table customers', 'just dropping by', 'undroppable'));

COLUMN_VALUE              ILLEGAL
------------------------- -------
drop table customers      Yes
just dropping by          
undroppable

I've added merge to the list as I assume you are trying to prevent SQL injection. If so, there are still risks even if you filter for keywords. execute isn't a SQL keyword, though. Did you mean call?
Your procedure would become:
create or replace procedure app_error_test
    ( query1 nvarchar2
    , query2 nvarchar2
    , query3 nvarchar2
    , query4 nvarchar2
    , query5 nvarchar2
    , query6 nvarchar2 )
as
    queryconcat nvarchar2(30000) :=
        query1||' '||query2||' '||query3||' '||query4||' '||query5||' '||query6;
begin
    if regexp_like(' ' || queryconcat || ' ', 's(drop|call|truncate|create|insert|update|delete|merge)s', 'i')
    then
        raise_application_error(-20032, 'Illegal content in supplied SQL: '||queryconcat);
    end if;
end;

Raise application error in a stored procedure when inputs contain keywords like 'delete' , 'insert','update'

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