Full Disclosure mailing list archives
Re: Mozilla extensions: a security nightmare
From: Mario Vilas <mvilas () gmail com>
Date: Wed, 5 Aug 2015 10:12:26 +0200
%APPDATA% is within the user's home directory - by default it should not be writeable by other users. If this is the case then the problem is one of bad file permissions, not the location. Incidentally, many other browsers and tons of software also store executable code in %APPDATA%. I think "security nightmare" may be a bit of an overstatement here. I'll refrain from panicking about this "issue" for the time being. On Tuesday, August 4, 2015, Stefan Kanthak <stefan.kanthak () nexgo de> wrote:
Hi @ll, Mozilla Thunderbird 38 and newer installs and activates per default the 'Lightning' extension. Since extensions live in the (Firefox and) Thunderbird profiles (which are stored beneath %APPDATA% in Windows) and 'Lightning' comes (at least for Windows) with a DLL and some Javascript, Thunderbird with 'Lightning' violates one of the mandatory and basic requirements of the now 20 year old "Designed for Windows" guidelines and breaks a security boundary: applications must be installed in %ProgramFiles% where they are protected against tampering by unprivileged users (and of course malware running in their user accounts too) since only privileged users can write there. Code installed in %APPDATA% (or any other user-writable location) is but not protected against tampering. This is a fundamental flaw of (not only) Mozilla's extensions, and a security nightmare. Separation of code from (user) data also allows to use whitelisting (see <https://technet.microsoft.com/en-us/library/bb457006.aspx> for example) to secure Windows desktops and servers: users (and of course Windows too) don't need to run code stored in their user profiles, they only need to run the installed programs/applications, so unwanted software including malware can easily be blocked from running. JFTR: current software separates code from data in virtual memory and uses "write xor execute" or "data execution prevention" to prevent both tampering of code and execution of data. The same separation and protection can and of course needs to be applied to code and data stored in the file system too! The Lightning extension for Windows but defeats the tamper protection and code/data separation provided by Windows: 1. its calbasecomps.dll can be replaced or overwritten with an arbitrary DLL which DllMain() is executed every time this DLL is loaded; 2. its (XUL/chrome) Javascripts can be replaced or overwritten and used to load and call arbitrary DLLs via js-ctypes. Only non-XUL/chrome Javascript is less critical since its execution is confined by (Firefox and) Thunderbird and subject to the restrictions imposed by these programs for non-XUL/chrome Javascript. Mitigation(s): ~~~~~~~~~~~~~~ Disable profile local installation of extensions in Mozilla products, enable ONLY application global installation of extensions. stay tuned Stefan Kanthak _______________________________________________ Sent through the Full Disclosure mailing list https://nmap.org/mailman/listinfo/fulldisclosure Web Archives & RSS: http://seclists.org/fulldisclosure/
-- “There's a reason we separate military and the police: one fights the enemy of the state, the other serves and protects the people. When the military becomes both, then the enemies of the state tend to become the people.” _______________________________________________ Sent through the Full Disclosure mailing list https://nmap.org/mailman/listinfo/fulldisclosure Web Archives & RSS: http://seclists.org/fulldisclosure/
Current thread:
- Mozilla extensions: a security nightmare Stefan Kanthak (Aug 05)
- Re: Mozilla extensions: a security nightmare Mario Vilas (Aug 05)
- Re: Mozilla extensions: a security nightmare Thomas D. (Aug 11)
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- Re: Mozilla extensions: a security nightmare Dave Horsfall (Aug 07)
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- Re: Mozilla extensions: a security nightmare Mario Vilas (Aug 05)