Re: C# Exceptions

Ok, I've reached the next level now.

I did a runtime analysis of the exe and some important DLLs as
ADMINISTRATOR and found a number of Heap Overruns in the COM
(unmanaged) components used by the application. Now the scenario is
that the C# application runs with privileges of the user logged-in and
not like a service or SYSTEM account so is it possible to do
following:

1. Obtain the same Heap Overruns from any LOW privileged user. Even if
it was possible would the attacker gain any extra privilege as the
application is running as the LOW privileged user.
2. Can these attacks be sent over the network when the application
communicates with the Internet services?
3. Any other attacks that are possible here?

Thnx.

On 8/28/06, 3 shool <3shool@xxxxxxxxx> wrote:
Thankx for your replies.

My comments in capitals below.

> In a (web)service orientated architecture, the message integrity is
> crucial. I would suggest to encrypt the data sent through the network
> and also digitally sign it. The desktop application validates the
> signature and if its not valid it will reject the incoming data. If the
> signature is valid then the app can decrypt the response and process it.

THE COMMUNICATION WITH WEB SERVICES IS OVER HTTPS AND IT HAS DIGITAL
CERTIFICATE. HOWEVER I UNDERSTAND SSL CERTIFICATES CAN BE SPOOFED AND
PROBABLY IF THE DESKTOP APPLICATION VALIDATES THE SIGNATURE THAT COULD
BE SPOOFED TOO?


ALSO THE COMMUNICATION WITH DATABASE SERVER IS ENCRYPTED.

> It's also recommended not to catch general exception like:
> catch (Exception ex) {}, but catch and handle different kind of
> exceptions as in : catch (NullReferenceException nullex) {} or catch
> OverflowException, etc.

SORRY BUT I DIDN'T GET THIS ONE. IF AN APPLICATION THROWS DIFFERENT
TYPES OF ACCEPTIONS LIKE NULL, AV, THAT WULD BE GOOD OR HAVING A
GENERIC ERROR MESSAGE IS BETTER. I FEEL IT WOULD BE BETTER TO THROW A
GENERIC ERROR.


> Another issue is that through reflection, ildasm you can re-construct
> the source code of a managed app (see .NET Reflector). It's also

WE ARE ABLE TO RE-CONSTRUCT THE SOURCE CODE OF SOME IMPORTANT DLLS BUT
NOT FOR THE MAIN PROGRAM EXE FILE.

> possible to patch system assemblies. It is possible to bring the
> Framework to its knees with fuzzed data. You cant really trust anything,

YES, THAT'S TRUE. IT IS NOT DIFFICULT TO CRASH A C# DESKTOP
APPLICATION BY FUZZING TECHNIQUES. ALTHOUGH I BELIEVE IT ISN'T REALLY
A SERIUOS ISSUE AS DOS ATTACK WILL AFFECT ONLY A SINGLE USER AND THE
OTHER IMPORTANT THING IS IT DOESN'T HAVE ANY PORTS OPEN OR SERVICE
AVAILABLE ON THE NETWORK.

> but do your best to detect it and do some defensive coding.

I THINK IT TAKES A LOT OF TIME TO PIN POINT THE CODE DEFECTS THAT
CAUSED A CRASH. WOULD IT BE WORTHWHILE TO SPEND THAT MUCH TIME FIXING
IT? ANYWAYS THIS ISSUE IS MAXIMUM GOING TO CAUSE A NON-SERIOUS DOS.


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