Bugtraq mailing list archives
RE: Internet Explorer and Opera local zone restriction bypass
From: "Mindwarper *" <mindwarper () linuxmail org>
Date: Sat, 25 Oct 2003 18:02:33 +0800
I decided to use the flash cookie just as an example. I could have used for example the Macromedia Director cookie. Another way would be using IE temporary cookies because they allow html tags and most other ascii symbols except for ";" in the cookie name. So all I have to do is create a document.write script which writes the activex. Another way would be using AIM's urlcache cookies which also apppear /Application Data/. If Mozilla or Opera are installed it is also possible to use they're data which is stored in the /Application Data/. The only problem is that I will still have to know the username of the victim. - Mindwarper ----- Original Message ----- From: "Thor Larholm" <thor () pivx com> Date: Fri, 24 Oct 2003 21:54:32 -0700 To: "Mindwarper *" <mindwarper () linuxmail org>,<bugtraq () securityfocus com> Subject: RE: Internet Explorer and Opera local zone restriction bypass
There was not a lot of details in your post, so I will try to verify and clarify your findings. First things first, this is not a problem with Microsofts Internet Explorer, but with Macromedia and their Flash player. I could reproduce this issue successfully with a fresh install of the latest Flash player, version 6.0.65.0, on fully patched versions of both IE6SP1 and Windows XP Pro. There are two completely new issues at hand here. The first issue is that Macromedia Flash allows you to store arbitrary content in a known location, that is %APPDATA%\Macromedia\Flash Player\YOURDOMAINNAME.TLD\YOURDOMAINNAME.sol. All flash cookies (which is what you set in your example, not browser cookies) from YOURDOMAINNAME.TLD are stored in this file. The issue is caused by Macromedias decision to store the contents of your Flash cookie in plaintext in this .SOL file. When IE later reads the file the "magic filetype" feature of Explorer reads the first 256 bytes, finds HTML content and determines to render the file as HTML since the target application is the browser, including your scripting. Being able to store arbitrary content in a known location is vital to any of the current range of IE exploits. Flash itself is a binary format, so this complete issue can easily be fixed by Macromedia by applying the same level of binary formatting to its Flash cookie contents, to provide slight obfuscation of the contents of Flash cookies when storing them on disk so Explorer does not misread its datatype. End-users can protect themselves against this exploit by changing how much data Flash applications are allowed to store on disk by going to http://www.macromedia.com/support/flashplayer/help/settings/global_storage.html and moving the slider all the way down, equivelant to checking the "Never Ask Again" checkbox on the page. When an updated version of the Flash player that fixes this is available, it is equally easy to change the setting back. System administrators can edit the file %APPDATA%\Macromedia\Flash Player\maromedia.com\support\sys\settings.sol and change the bytes at positions c7 and c8 to contain BF and F0, respectively (ASCII ¿ and ð), to restrict data storage for Flash applications as an end-user would above. If you want to restore the file to default settings (for storing 100KB data) change the bytes back to 40 and 59, respectively (ASCII @ and Y). This is also why several people have said they could not reproduce the issue. They were either not logged in with the Administrator account, which your POC required, or they did not have the Macromedia Flash player installed. A similar issue was found way back with ID3 tags in Winamp and RealPlayer media files, and has been found on several occasions where a third-party non-Microsoft application allows you to store arbitrary content in a known location. The second issue is that IE lets you redirect to local files. This was restricted in IE6 SP1. While going over the source code in your POC, we discovered that it inadvertently redirects to a local file, despite the apparent restriction. When IE encounters a redirect such as the following Content-Location: file://c:/somefile.html it will disallow the action and not follow the redirect. However, your POC has one important alteration, which is the following Content-Location: file:///c:/somefile.html Did you notice that slight difference? Adding another slash to the URL circumvents the initial restriction, and when IE finally decides to load the URL in another part of its code it removes any excess slashes and properly loads file://c:/somefile.html The restriction imposed by IE6 SP1 is imposed on all local protocols, such as file:// and res://, and this new way to circumvent it equally applies to all local protocols. This means that you don't have to know the location of a specific file, but instead can open a ressource file available on all systems, such as Content-Location: res:///browselc.dll/mb404.htm Of course, since you could not inject any code in the ressource file you will now have to use another cross-domain scripting vulnerability in place of the Macromedia Flash vulnerability you identified in the first issue. On the positive side, it also means that you no longer have to guess the users Windows Logon name. In summary, when Macromedia changes their Flash player to no longer store Flash cookies in plaintext in a known location, this will no longer be an issue. All of the currently unpatched cross-domain scripting vulnerabilities are having patches produced, and since they have no easy POC exploits I doubt we will see any malicious use of the local file redirection variation you found. Regards Thor Larholm PivX Solutions, LLC - Senior Security Researcher http://pivx.com/larholm/ - Get our research, join our mailinglist -----Original Message----- From: Mindwarper * [mailto:mindwarper () linuxmail org] Sent: Friday, October 24, 2003 6:53 AM To: bugtraq () securityfocus com Subject: Internet Explorer and Opera local zone restriction bypass <snip http://www.securityfocus.com/archive/1/342317/2003-10-22/2003-10-28/0>
-----------------------------| - Mindwarper | - mindwarper () linuxmail org | - http://mlsecurity.com | -----------------------------| -- ______________________________________________ Check out the latest SMS services @ http://www.linuxmail.org This allows you to send and receive SMS through your mailbox. Powered by Outblaze
Current thread:
- Internet Explorer and Opera local zone restriction bypass Mindwarper * (Oct 24)
- Re: Internet Explorer and Opera local zone restriction bypass Jort Slobbe (Oct 24)
- Re: Internet Explorer and Opera local zone restriction bypass jelmer (Oct 27)
- Re: Internet Explorer and Opera local zone restriction bypass Andreas Sandblad (Oct 27)
- Re: Internet Explorer and Opera local zone restriction bypass Andreas Sandblad (Oct 27)
- Re: Internet Explorer and Opera local zone restriction bypass jelmer (Oct 28)
- <Possible follow-ups>
- RE: Internet Explorer and Opera local zone restriction bypass Thor Larholm (Oct 27)
- RE: Internet Explorer and Opera local zone restriction bypass Mindwarper * (Oct 27)
- Re: Internet Explorer and Opera local zone restriction bypass Heikki Toivonen (Oct 27)
- Re: Internet Explorer and Opera local zone restriction bypass Mohsen Hariri (Oct 27)
- Re: Internet Explorer and Opera local zone restriction bypass Paul Szabo (Oct 27)
- RE: Internet Explorer and Opera local zone restriction bypass Thor Larholm (Oct 28)
- Re: Internet Explorer and Opera local zone restriction bypass Bipin Gautam hUNT3R (Oct 28)
- Re: Internet Explorer and Opera local zone restriction bypass william schulze (Oct 30)
- RE: Internet Explorer and Opera local zone restriction bypass Francis Favorini (Oct 30)
- Re: Internet Explorer and Opera local zone restriction bypass Paul Szabo (Oct 30)
- RE: Internet Explorer and Opera local zone restriction bypass Thor Larholm (Oct 30)
- RE: Internet Explorer and Opera local zone restriction bypass Paul Szabo (Oct 31)
- Re: Internet Explorer and Opera local zone restriction bypass Jort Slobbe (Oct 24)