Row-0 mitigation of SQL injection

From: Jim Halfpenny (jimsmailinglists@gmail.com)
Date: Wed Jun 06 2007 - 18:21:28 EDT


Hi,
One thing I've noticed about SQL injection is that quite often the
injected code returns a data set and the vulnerable application plucks
the first row from the set. Consider a simple example where a login
form is vulnerable and the following code is generated:

select * from users where login = '' or 'a' = 'a';

Instead of returning one row as expected the whole table is returned
and the application more often than not reads the first row. This hack
is especially bad if the first user in the table has admin right,
which is often the case.

One way of potentially hobbling simple SQL injection would be to
insert a sentinel record at the beginning of the table (hence the
row-0 concept). This this row is ever returned the the application can
be made aware something bad has happened.

Does this sound like a good idea, or does it encourage poor coding by
having a safety net? All comments welcome.

Jim

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