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RE: White paper: Exploiting the Win32 API.
From: "John Howie" <JHowie () securitytoolkit com>
Date: Tue, 6 Aug 2002 14:15:28 -0700

Florian,
 
You are correct about Windows Stations and Desktops, but these are not new and have been around since the early 
releases of Windows NT. They are not a panacea. A (bad) developer can easily create a service that interacts with the 
user's desktop and launch windows onto it by specifying SERVICE_INTERACTIVE_PROCESS in the dwServiceParameter to 
CreateService (). There is even a mechanism for services to be made aware when a user is logging on to the system so 
that they can do just this. Chris' paper on his web-site names one such application.
 
I suspect laziness or ignorance drove the developer to code their application the way that they did. In fact, they 
would absoultely not want to use an alternate Windows Station as they want to provide a user interface. An application 
running with a window in another Windows Station or Desktop cannot be viewed by the user unless he/she can switch to 
it. While there is an API for this it is seldom used (remember the old Switch Desktop utility in the early Resource 
Kits?).
 
John

        -----Original Message----- 
        From: Florian Weimer [mailto:Weimer () CERT Uni-Stuttgart DE] 
        Sent: Tue 8/6/2002 1:51 PM 
        To: John Howie 
        Cc: Chris Paget; bugtraq () securityfocus com 
        Subject: Re: White paper: Exploiting the Win32 API.
        
        

        "John Howie" <JHowie () securitytoolkit com> writes:
        
        > This class of attack is not new, it has been discussed before. While you
        > can assert that the blame lies with Microsoft (and I'll admit they do
        > have some responsibility to address the problem you describe)
        
        A bit of MSDN browsing revealed that Microsoft has already "fixed" the
        vulnerabilites, despite the claim that this was impossible.  The
        concepts are called "window stations" and "desktops", and there is
        plenty of documentation.  Everything is there: separate sets of hooks,
        separate message queues, and so on.
        
        Maybe there are some flaws, but the overall design seems to be sound.
        
        --
        Florian Weimer                    Weimer () CERT Uni-Stuttgart DE
        University of Stuttgart           http://CERT.Uni-Stuttgart.DE/people/fw/
        RUS-CERT                          fax +49-711-685-5898
        


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