Oracle9i Application Server Format String Vulnerability (#NISR16022003d)

["NGSSoftware Insight Security Research" <nisr () nextgenss com>]

NGSSoftware Insight Security Research Advisory

Name:    Oracle9i Application Server Format String Vulnerability
Systems Affected:  All platforms; Oracle9i Application Server Release 9.0.2
Severity:  Critical Risk
Category:               Format String Vulnerability
Vendor URL:   http://www.oracle.com
Author:   David Litchfield (david@ngssoftware) and Mark Litchfield
(mark () ngssoftware com)
Date:   16th February 2003
Advisory number: #NISR16022003d


Description
***********
Oracle's 9i Application Server offers a highly functional web server
designed to seamlessly integrate with an Oracle backend database server.
Based on Apache the server offers many environments for web based
applications such as Java/JSP, PL/SQL, Perl and FastCGI. With their latest
release of the Application Server, 9.0.2, Oracle has added support for
WebDAV, Web Distributed Authoring and Versioning, that turns the Web into a
file sharing system.


Details
*******
DAV is turned on by default. Whilst this is bad in and of itself, as
attackers can anonymously upload files to the server, an attacker can
exploit a format string bug in the one of the logging functions. If an
attacker uses the COPY method and supplies a destination URI that uses a
different scheme or port then a 502 Bad Gateway response is returned. This
is logged and in doing so the format string can be exploited. Although the
Apache mod dav module is not vulnerable itself the vulnerable code is
there - it is just not ever executed. Oracle has modified the moddav module
and changed it so bad gateway responses are logged - and thus they are
vulnerable. Looking at the moddav source

> From mod_dav.c revision 1.157

..
..
lookup = dav_lookup_uri(dest, r);
if (lookup.rnew == NULL)
{
      if (lookup.err.status == HTTP_BAD_REQUEST)
      {
            ap_log_rerror(APLOG_MARK, APLOG_ERR | APLOG_NOERRNO,
r,lookup.err.desc);
            return HTTP_BAD_REQUEST;
      }
      return dav_error_response(r, lookup.err.status, lookup.err.desc);
}
..
..

This code calls the dav_lookup_uri() function in dav_util.c. From dav_util.c
revision 1.84

..
dav_lookup_result dav_lookup_uri(const char *uri, request_rec * r)
{
..
..
if (strcasecmp(comp.scheme, scheme) != 0 || comp.port != port)
{
      result.err.status = HTTP_BAD_GATEWAY;
      result.err.desc = ap_psprintf(r->pool,
      "Destination URI refers to different "
      "scheme or port (%s://hostname:%d)\n"
      "(want: %s://hostname:%d)",
      comp.scheme ? comp.scheme : scheme,
      comp.port ? comp.port : port,
      scheme, port);

      return result;

..
..
}

When dav_lookup_uri() returns to mod_dav.c the format strings occurs

..
lookup = dav_lookup_uri(dest, r);
if (lookup.rnew == NULL)
{
      if (lookup.err.status == HTTP_BAD_REQUEST)
      {
      // THIS IS THE FIRST FORMAT STRING VULNERABILITY
      ap_log_rerror(APLOG_MARK, APLOG_ERR | APLOG_NOERRNO,
r,lookup.err.desc);
..
..
}


Of course the code should have read

ap_log_rerror(APLOG_MARK, APLOG_ERR | APLOG_NOERRNO,
r,"%s",lookup.err.desc);

to not be vulnerable.

By crafting a specially formed format string and sending to the server an
attacker can overwrite arbitrary address with arbitrary values which can
allow an attacker to gain control of the web server. To do this they could
overwrite a saved return address on the stack, an exception handler or
pointer to a function with an address that points to a buffer that contains
the arbitrary code to execute.

Fix Information
***************
NGSSoftware alerted Oracle to this vulnerability on 24th September 2002.
Oracle has developed a patch which is available from

http://otn.oracle.com/deploy/security/pdf/2003alert52.pdf

A check for these issues has been added to OraScan, a comprehensive
automated vulnerability assessment tool for Oracle Application Servers of
which more information is available from the NGSSite

http://www.nextgenss.com/software/orascan.html

About NGSSoftware
*****************
NGSSoftware design, research and develop intelligent, advanced application
security assessment scanners. Based in the United Kingdom, NGSSoftware have
offices in the South of London and the East Coast of Scotland. NGSSoftware's
sister company NGSConsulting, offers best of breed security consulting
services, specialising in application, host and network security
assessments.

http://www.ngssoftware.com/
http://www.ngsconsulting.com/

Telephone +44 208 401 0070
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