RE: application for an employment

["David Gillett" <gillettdavid () fhda edu>]

> -----Original Message-----
> From: Ansgar -59cobalt- Wiechers [mailto:bugtraq () planetcobalt net] 
> Sent: Thursday, March 30, 2006 10:35 AM
> To: security-basics () securityfocus com
> Subject: Re: application for an employment
>
> On 2006-03-30 David Gillett wrote:
> > > The legitimate reason you have is the simple fact that you 
> don't have 
> > > any other option of determining what services are available on a 
> > > given host or range of hosts.
> >
> >   Yes you do.
>
> No, I don't. There are some exceptions, where I don't have 
> to, but in general there is no way of finding out other than 
> actually connecting to the service.
>
> >   Suppose you want to send me an email.  By your argument, 
> your only 
> > option is to scan our whole address block(s!) looking for machines 
> > that will answer on port 25.
> >   Bzzzt!  WRONG!  Do a DNS lookup for the MX records for our domain.
>
> So, how do I do a DNS lookup without somehow accessing port 
> 53/udp of a DNS server that I do not own? How do I get 
> permission to do that?

  You don't.  You send your DNS query to a server you *do* have permission
to access, and it queries servers that *it* has permission to, and so on.
By registering our domain, we've given the root servers permission to refer 
queries *about our domain* to the servers we've registered.
 
> >   Suppose you want to register online to take courses here. 
>  By your 
> > argument, your only option is to scan our address space for 
> hosts that 
> > answer on ports 80 and 443.
> >   Bzzzt!  WRONG!  Point your browser at the college homepage (you 
> > could Google for it) and follow the links to "Registration".
>
> So, how does Google get the address of your webserver? Or 
> permission to access/index it? How do I get permission to 
> access Google? And how does a listing of $something in Google 
> give me the permission to access it?

  AFAIK, Google still supports a mechanism for telling them about specific
pages to be indexed.  And their spider plays by the robots.txt rules, which
your port scanner probably does not.
 
> >   Suppose you want to compromise one of our hosts to set up a warez 
> > server.  By your argument, your only option is to scan our address 
> > space looking for a host running a service for which you have an 
> > exploit available.
> >   Uh, wait.  You just lost the qualifier "legitimate".
>
> I was by no means talking about exploits. In fact I expressly 
> stated that one may be held liable when breaking something 
> (which you obviously chose to ignore for whatever reason).

  Oh, okay, let's exclude all non-legitimate examples.  Then give me a
legitimate one, please, that I *can't* knock down.

> >   If I want you to be able to use a service X on host Y, I 
> will find 
> > some way to advertise that service.  If I don't advertise 
> the service, 
> > it may be something that I don't even know is there -- perhaps 
> > installed silently by the OS or some legitimate application, or 
> > perhaps by some cracker.  In neither case is there a 
> presumption that 
> > I'm inviting you to use it, if only you can find it.
>
> That's ridiculous and you know it. The Internet does not have 
> advertisement mechanisms for services. The network is public 
> and so is every service on it. It was your decision to put 
> the box into a public network and there are ways to know what 
> services it provides (and to disable those services you don't 
> want to provide). I cannot know if you made a service 
> available on purpose, and I do not have to assume that you 
> didn't. If I had to, the Internet would have to be shut down 
> right this second.

  I've already listed two "advertising" mechanisms, without going
into silly proprietary endeavors like SLP.

> Bottom line: If you don't want your property trespassed, 
> don't put it into public places.

  Our data center is not, by any stretch, a public place.  By your
analogy, my lawn becomes a public parking lot because a driveway 
connects it to the street.  Once again, "Bzzzt!  Wrong."

> Regards
> Ansgar Wiechers
> --
> "All vulnerabilities deserve a public fear period prior to 
> patches becoming available."
> --Jason Coombs on Bugtraq

David Gillett



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