full-disclosure - Edonkey/Overnet Plugins Could Pose Harm

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Message-ID: <20031217150340.GA6369@SDF.LONESTAR.ORG>
From: petard at freeshell.org (petard)
Subject: Edonkey/Overnet Plugins Could Pose Harm

On Wed, Dec 17, 2003 at 12:11:38AM -0500, ashton wrote:
<gross misunderstanding/ranting about plugins snipped>
I don't get it. You wrote a long message about how running arbitrary
code from an untrusted source on your PC is insecure. How is this
different from any other common plugin architecture?

You site the Windows Media SDK as an example that gets it write because
it uses "COM" instead of what you refer to as "full c++ access", but you
never differentiate between the two. COM objects can certainly be
written in C++, and there is absolutely no sandbox to keep that code
from doing malicious things. It simply must conform to a COM interface.
If you believe that a malicious (for instance) Windows Media
visualization plugin or a malicious photoshop plugin cannot do every
nasty thing an edonkey plugin can, you are delusional.

Here's a hypothetical example for Windows Media, your example of a safe
SDK:

STDMETHODIMP CMyVisualizer::Render(TimedLevel *pLevels, HDC hdc, RECT *prc)
{
    //Check for our malicious process
    if( !isHelperRunning() ) {
        launchEvilHelperProcess();
    }
    // Proceed to draw pretty pictures so that the moron who downloaded
    // and executed this arbitrary code while thinking it was safe since
    // it exported a COM interface suspects nothing
    doRender( pLevels, hdc, prc );
}
I'll leave the implementation of isHelperRunning() and
launchEvilHelperProcess() to your imagination, but suffice to say code
that's running here is in no way restricted by the fact that the
interface used to invoke it is defined by a particular IDL file and
conforms to the COM specification.

To have a reasonable shot at "safe" plugins, you'd really need some sort
of sandboxing system akin to java's. Even then, as we've all seen, it's
hard to get right. No common app that I can think of attempts this.

In short, it doesn't matter what application starts your arbitrary
code. You could write a malicious plugin for netscape, photoshop, quark,
WMP, anything that takes true executable code for plugins. Most plugin
systems do. Furthermore, few if any provide some sort of clearinghouse
to vet plugins and declare them safe. Don't run it unless you trust it.
It is, for all (good and evil) purposes nothing more then executable
code that is launched and communicates in a specified way.

So my question remains: How is eDonkey worse than these others?

Regards,

petard