17th Feb 2003 [SBWID-5992]
COMMAND
Oracle9i Application Server Format String Vulnerability
SYSTEMS AFFECTED
All platforms; Oracle9i Application Server Release 9.0.2
PROBLEM
Thanks to David Litchfield [david@ngssoftware] and Mark Litchfield
[[email protected]] of NGSSoftware Insight Security Research,
advisory [#NISR16022003d] :
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.
SOLUTION
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
Further Information
*******************
For further information about the scope and effects of buffer overflows,
please see
http://www.ngssoftware.com/papers/non-stack-bo-windows.pdf
http://www.ngssoftware.com/papers/ntbufferoverflow.html
http://www.ngssoftware.com/papers/bufferoverflowpaper.rtf
http://www.ngssoftware.com/papers/unicodebo.pdf
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
Fax +44 208 401 0076
[email protected]