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 (markat_private) 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 Fax +44 208 401 0076 enquiriesat_private
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