NGSSoftware Insight Security Research Advisory

Name: Oracle Listener Control Format Strings
Systems Affected:  Oracle 9i, 8i on all platforms
Severity: Medium
Category: Format String Vulnerabilities
Vendor URL:   http://www.oracle.com/
Authors:  David Litchfield (david@ngssoftware.com)
Advisory URL: http://www.ngssoftware.com/advisories/ora-lsnrfmtstr.txt
Date:   14th August 2002
Advisory number: #NISR14082002
VNA Reference:  http://www.nextgenss.com/vna/ora-lsnrctl.txt


Description
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Oracle provide a tool called the Listener Control utility (lsnrctl) to allow
an Oracle DBA to remotely control the Listener. The Listener is responsible
for dealing with client requests for database services. This control utility
contains an indirect remotely exploitable format string vulnerability.

Details
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By default the Oracle Listener is not protected against unauthenticated
access and control. The configuration files of Listeners in such a state can
be modified without the user needing to supply a password. By modifying
certain entries in the listener.ora file, by inserting a format string
exploit, an attacker can gain control of a Listener control utility.
Typically an attack would require the attacker to modify the file and wait
for an Oracle DBA to use the Listener control utility to access the Listener
at which point control over the utility's path of execution can be gained.
This will give the attacker the ability only to gain control of the DBA's
machine and not the database server. This is a complex attack and requires
certain "events" to happen and as such the risk is quite low. That said,
Oracle users are urged to apply the patch.


Fix Information
***************
NGSSoftware alerted Oracle to this problem on the 13th May 2002. Oracle have
produced a patch and issued an alert. Please see their bulletin for more
details.

http://otn.oracle.com/deploy/security/pdf/2002alert40rev1.pdf

In the intermin NGSSoftware advise that Oracle DBAs ensure that the Listener
can not be controlled remotely and anonymously.

There are several steps one can take to secure the Listener and hence
prevent exploitation of this format string vulnerability.

One can set in the listener.ora

ADMIN_RESTRICTIONS_lsnrname=ON

This will prevent modifications to the Listener config files. Furthe a
password should be set to limit actions a user can take.