Re: Proposing gobby?

["Gustavo J. A. M. Carneiro" <gjc inescporto pt>]

Qua, 2005-11-16 às 18:23 +0100, Philipp Kern escreveu:
> On Nov 16, 2005, at 15:53, Gustavo J. A. M. Carneiro wrote:
> >   This happens because the home user doesn't have any feeling for the
> > limitations of the security of the protocol.  Sure, the security  
> > can be
> > adequate in some cases, but the end user doesn't know which cases, and
> > just uses it even when not secure.
> 
> Well, now you are exaggerating, which is sad.

  I'm not exaggerating.  Ever heard of man-in-the-middle attacks?  Try
ettercap to get the feel of it.  You'll be amazed what it can do :)

>  Verification of public  
> keys was planned, but hey, it's 0.3.0 now.

  Sure.  I know it's only 0.3.0.  Maybe that means Gobby needs 6 more
moths to improve the protocol.  That's perfectly fine and doesn't mean
it is any less a great program.  It's just that we need to cope with
some users that, erm, let's say are not very smart :P

>  Yes, that's indeed why the  
> server generates a public key on startup, which is currently only  
> used for safe password transmission.
> 
> It is currently not possible to replay the password, so you cannot  
> enter a session secured with a password. So the case you stated is  
> not real. By the way you will notice any join.

  TCP is not secure.  An attacker can inject traffic in the middle of
the stream some time after the authentication, and the user will not
notice anyone else joining.

> 
> What's real however is the fact that the data stream itself is  
> unencrypted. This is currently because the encryption on the server  
> side is extensive due to the size of the private key. There is even a  
> stub for a security preferences tab in Gobby.

  Both sides generate and agree on a common key and then use a symmetric
cypher which is less expensive.  I'm not even a security expert and know
all this.  If you are designing a protocol, you should know it better
than me.  So why not just use TLS, or something like that, instead of
reinventing the wheel?

  Alternatively, just add a check to Gobby to see if remote IP is on the
same subnet as the local IP, and warn the user about potencial security
problems if not.

  Best regards.

-- 
Gustavo J. A. M. Carneiro
<gjc inescporto pt> <gustavo users sourceforge net>
The universe is always one step beyond logic.