Vulnerability Report For BEA Weblogic's Proxy

Vulnerability Report For BEA Weblogic's Proxy

Advisory ID: CORE-081300

Bugtraq ID: 1570

CVE Name: CVE-2000-0681

Title: BEA Weblogic Multiple Buffer Overflow Vulnerabilities

Class: Boundary Error Condition (Buffer Overflow)

Remotely Exploitable: Yes

Locally Exploitable: Yes

Vulnerability Description:
BEA Systems Inc. Weblogic server provides facilities to integrate it to third party web servers. This is accomplished by a plug-in that allows the third party web server to proxy requests to the Weblogic Server. As described in BEA's documentation plugins are supported for Netscape Enterprise Server, IIS and Apache in the form of dynamically loadable libraries.

http://www.weblogic.com/docs51/admindocs/lockdown.html

These web servers can be configured to redirect requests for servlets and JSP files to a Weblogic server running on the same or on a different host.

Several buffer overflows in these plugins provided by BEA Weblogic server allow a remote attacker to execute arbitrary code on the system running the proxying web server. The net result of this is remote execution of arbitrary code as the user running the proxying server (generally root on UNIX systems, SYSTEM on MS NT). For those interested a technical description and proof of concept follow towards the end of this advisory.

Vulnerable Packages/Systems:
In each instance the particular vulnerable binary information is provided due to the fact that is differant for each web server/ OS.
Netscape Enterprise Webserver (NES)
-----------------------------------
NSAPI Weblogic binaries are:
NES for UNIX - libproxy.so
NES for NT - proxy30.dll, proxy35.dll, proxy36.dll
- Solaris with NES versions 3.0 to 4.1
- AIX with NES 3.6
- HP-UX 10.20 with NES version 3.6
- HP-UX 11.00 with NES version 3.6
- Windows NT with NES versions 3.0 to 4.1
Internet Information Server (IIS)
---------------------------------
ISAPI Weblogic binaries are:
IIS - iisproxy.dll
- NT 4.0 with IIS 4.0
Apache Server
-------------
ISAPI Weblogic binaries are:
Apache for UNIX - mod_wl.so, mod_wl_ssl.so, mod_wl_ssl_raven.so
- Solaris with Apache Server 1.3.9, 1.3.12
- Linux with Apache Server 1.3.9, 1.3.12
- HP-UX 11.00 with Apache Server 1.3.9, 1.3.12
- C2Net Stronghold/3.0 and Covalent Raven/1.4.3
- C2Net Stronghold/3.0 and Covalent Raven/1.4.3
- C2Net Stronghold/3.0
- Linux with Apache Server 1.3.9, 1.3.12
- HP-UX 11.00 with Apache Server 1.3.9, 1.3.12

Solution/Vendor Information/Workaround:
BEA advises the following:
Version: BEA WebLogic Server and Express 5.1.x, 4.5.x standalone version or as part of BEA WebLogic Enterprise 5.1 on all OS platforms
Action : Upgrade the proxy plug-in used for third-party Web server integration.

To do this, download the package at:
ftp://ftpna.bea.com/pub/releases/patches/SecurityBEA00-0500.zip (800kb)
This package includes an updated version of the proxy plug-in for use with Netscape Enterprise Server (NES), MicrosoftInternet Information Server (IIS), and Apache Web servers. The maximum size of the buffer used to hold the computed URI path remains 2048 bytes. If a computed URI path is greater than the size of the buffer, the proxy plug-in will report the error "414 - Request-URI Too Long" to the client as suggested by the HTTP 1.1 specification.

After downloading this package, open it and follow the instructions in your version of the product for installation procedures.

BEA strongly suggests that customers apply the remedies recommended in all their security advisories. In addition, customers are advised to apply every Service Pack as they are released. Service Packs include a roll up of all bug fixes for each version of the product, as well as each of the previously released Service Packs.

Additionally, advisories and information on security issues of BEA products can be obtained from:
http://developer.bea.com/alerts/index.html
http://www.securityfocus.com/bid/1525
http://www.securityfocus.com/bid/1518
http://www.securityfocus.com/bid/1517
http://www.securityfocus.com/bid/1378
http://www.securityfocus.com/bid/1328

Vendor notified on: July 24th, 2000

Credits:
This vulnerability was discovered by Gerardo Richarte and Hernan Ochoa of CORE SDI S.A., Buenos Aires, Argentina.

We wish to thank BEA Systems Inc. from their prompt response to the problem report.

This advisory was drafted with the help of the SecurityFocus.com Vulnerability Help Team. For more information or assistance drafting advisories please mail vulnhelp@securityfocus.com.

Technical Description - Exploit/Concept Code:
Tests were performed using iPlanet Webserver Enterprise 4.1 as the proxying web server. Following BEA documentation it was configured to proxy .JSP requests to a Weblogic server on a different host using the following configuration settings in servername/config/obj.conf:
obj.conf:
[... text deleted ...]
<Object name=default>
[...]
Service method=(GET|HEAD|POST|PUT) type=text/jsp fn=wl-proxy\
WebLogicHost=weblogic WebLogicPort=7001 PathPrepend=/jspfiles
[....]
</Object>
[....]

The above configuration will direct the iPlanet Webserver to use the provided library (libproxy.so) to redirect the requests for files with extension .JSP to the WebLogic server listening on port 7001/tcp of the host 'weblogic' The '/jspfile' string will be prepended to the URL sent to the Weblogic host.

For example the request for 'http://webserver/test.jsp?my_parameter' will become 'http://weblogic:7001/jspfiles/test.jsp?my_parameter' and proxied to the WebLogic server.

Handling of the requests to be proxied is made in the wl_proxy function of the libproxy.so library.

At wl_proxy+1812 there is a call to strcat() that tries to concatenate the PathPrepend argument specified in the obj.conf file with the requested URL, no bound checks are performed on the destination buffer allocated in the stack. By providing a request with more than 2100 characters long a buffer overflow condition can be exploited and arbitrary code run as the user running the proxying web server.

Explotation of the vulnerability can be difficult due to the fact that after the overflow certain automatic variables, placed in the stack and now corrupted by the overflow, are accessed at wl_proxy+1896, before executing a ret instruction.

Also, the proxying web server performs some length checks of its own on the received request and its therefore not possible to send arbitrary long requests. However, this size limit on the proxying web server is permissive enough to let an attacker exploit the problem in the library.

The PathPrepend argument does not need to be set in order to exploit the vulnerability Unsuccessful explotation of the problem does not lead to denial of service attacks as the web server continues normal execution.

Sample, proof of concept code:
$ perl -e 'print "GET http://webserver/test.jsp?";print "A"x2200;\
print " HTTP/1.0

"'|nc weblogic 80

note: wrapped for readability

DISCLAIMER:
The contents of this advisory are copyright (c) 2000 CORE SDI S.A. and may be distributed freely provided that no fee is charged for this distribution and proper credit is given.

Locally Exploitable: 
no
Remotely Exploitable: 
no
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