ControlThread (SecurityPermission)

From: Thread enumeration (whatabohr@hotmail.com)
Date: 03/24/03 

From: "Thread enumeration" <whatabohr@hotmail.com>
Date: Sun, 23 Mar 2003 21:29:48 -0800

I am writing an application which needs to allow
partially trusted plugins to execute. I load these
assemblies with very few permissions (In fact, I have
tried it with _nothing_ but execute).

I find however that even without the ControlThread
SecurityPermission being assigned, the plugin code still
seems to have full control over creating a thread and
setting priority. I need a way to prevent the plugin
(which is potentially malicious) from creating a new
thread and performing a DOS against legitimate code.

When I call into a plugin I create a thread and execute
on that thread (having assigned it a lower priority) then
I have a monitor thread which is capable of aborting the
plugin thread if it doesn't return after a timeout. This
works great, what I cannot do is prevent the plugin from
spawning a thread (which I have no way of controlling)
which survives after I kill the parent thread.

If there was some way I could enumerate the managed
threads, then perhaps I could identify these leftover
threads and abort them, but I cannot find a way to do
this. From a System.Diagnostics.Process instance I can
enumerate the unmanaged threads, but there seems to be no
way to translate from these to managed Thread objects,
nor any way to terminate them.

Any thoughts?

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