RE: C# Exceptions

["Patrick" <patrick () curioustechnology com>]

To my knowledge, no one has successfully executed code using a buffer
overrun in .Net.  The .NET CLR is not a good target for executing shell
code.  If you do manage to do this, pat yourself on the back, post on
bugtrack and be prepared to have made a significant impact on the software
industry.  Please site me as your first detractor ;)

Crashing .net itself ain't hard.  I'm an example of the type of dev who's
done it regularly!  As I mentioned before, I'm unaware of anyone having
successfully used a .net overrun to execute code.  It may be possible, but
it's been 6 years since .NET came on the scene and so far MS has been very
successful on delivering on the promised enhanced security that the
marketing folks have always referenced.

I alluded before to the [unsafe] keyword.  Read more on [unsafe] here:
http://www.codersource.net/csharp_unsafe_code.html.  The only known way to
do code execution via the stack would be if the target app used [unsafe].
Just a caveat- I don't believe that [unsafe] is provided in vb, so be double
sure your app is built with the environment that you think it is if you're
going to cross your fingers and go after an [unsafe] opportunity.

As far as your best opportunity for penetration, go back to targeting the
environment rather than the application.  On the other hand, perhaps you
have dependencies on other applications that may lead you to an
executable/command line environment via the web services interfaces they've
created.  I'm sure you've seen SQL injection attacks that reverse shell out
a command line with xp_cmdshell.  I assume you've already exhausted this end
of things though and if you're still struggling, I'd say it's time to spend
time with your Nessus dumps and start thinking about service configurations
or old versions of IIS.

Good luck!



-----Original Message-----
From: 3 shool [mailto:3shool () gmail com] 
Sent: Saturday, August 26, 2006 10:36 PM
To: Patrick
Cc: pen-test () securityfocus com
Subject: Re: C# Exceptions

Patrick, thanx for the detailed email.

We are able to crash the application over the network by intercepting
the traffic that goes in  to the target application from the
legitimate web serivces. We got these three different exceptions for
different type of fuzzed data. Now before we move forward we were
planning to see what would be our best option out of these three
exceptions or memory dump that could give us remote code execution or
at least best chance of penetration.

Since buffer overruns are not possible in a .Net applicaiton what if
we target a bufferoverrun in .Net itself? We got a couple of crashes
that crashed .Net instead of generating any exceptions.

If we were to pursue our best possibility of penetration what would it be?


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