Re: Could a hacker achieve this?
From: Paul Glavich [MVP - ASP.NET] (glav_at_aspalliance.com-NOSPAM)
Date: 04/11/04
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Date: Sun, 11 Apr 2004 22:08:50 +1000
Stealing the DLL is one task and probably the hardest. As was mentioned in
another post, it depends on how you have your security configured. If we
assume a standard .Net app with the DLL in the bin folder, no explicit ACL
set by yourself, then while it is possible, its not too easy. The more your
machine is locked down, the harder it is for a hacker to get in and grab
some code libraries.
Now if we assume that the hacker has gained entry to your machine and can
get your assemblies, then how hard would it be to have a look at your secret
code. Well, without obfuscating your code, it would actually be quite easy.
Obfuscating your code makes it considerably harder, but certainly not
impossible. John mentioned that hardcoding the secret key is quite common,
but it is bad practice. Ideally, you should probably extract it from
somewhere that keeps it in an encrypted form also. Ideal for this situation
is the DPAPI libraries. Typically, you can decrypt data only on the machine
it was encrypted on (or only by the user it was encrypted by), with DPAPI
handling the key storage for you. So if the hacker got your code, it would
simply be referencing a key on the local machine, which is also encrypted.
If the hacker then manages to get that encrypted key, they cant decrypt on
anyother machine, so its useless to them.
So you could either use DPAPI for all your encryption needs or just to
store/encrypt the encryption key that you will be using. DPAPI is an
unmanaged set of libraries/functions, but there is a managed wrapper with
example code to be found here.
http://weblogs.asp.net/pglavich/archive/2004/03/15/89687.aspx
--
- Paul Glavich
Microsoft MVP - ASP.NET
"WJ" <JWebb@Msn2.Com> wrote in message
news:OSam773HEHA.3536@TK2MSFTNGP09.phx.gbl...
>
> "Framework fan" <tempframeworkfan@hotmail.com> wrote in message
> news:f109ac80.0404100653.7a9ba1c2@posting.google.com...
> > Hello.
> >
> > If I have this line of code inside my ASP.NET app:
> >
> > EncryptTripleDES("String to encrypt", "MySecretKeyXYZ!!!")
> >
> > Can a very experienced hacker do either of the following:
> >
> > 1. "Steal" the DLL from the server, then reverse engineer the DLL in
> > order to obtain the hard coded key above.
> >
>
> Depend on how tight your ACL is enforced at your server where the DLL is
> hosted. I would check this first to make sure only the intended users have
> access to it. I would offuscate my code if it is that sensitive.
Hardcoding
> secret key in an application is a common practice. Just name things
> different than suggested by some best programming pratices to make life
> harder for hackers. This means that in some cases, you need to be abnormal
> in your programming style.
>
> > 2. (Much more clever) kind of "listen in to / tap in to" the DLL as
> > it is actually executing on the server, and then kind of "syphon off"
> > the data that is flying about the machine's data ports, in order to
> > "catch / filter off" the secret key.
> >
>
> Chances for this to happen is very slim unless there is an iider help.
>
> John
>
>
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