From: "James A. Donald" <jamesd@netcom.com>
Date: Wed, 18 Jan 95 11:12:04 PST
To: "Perry E. Metzger" <perry@imsi.com>
Subject: Re: (none)
In-Reply-To: <9501181603.AA01635@snark.imsi.com>
Message-ID: <Pine.3.89.9501181033.A15911-0100000@netcom10>
MIME-Version: 1.0
Content-Type: text/plain


Eric Hughes says:
> > I argue that if you hook your machine up to the Internet, you've
> > implicitly authorized people to send you packets -- as many as they
> > want and of whatever nature as they want.  No service provision I've
> > ever seen gives any recourse to the end user against the provider for
> > "bad" packets.
 
On Wed, 18 Jan 1995, Perry E. Metzger wrote:
> Be that as it may, people HAVE been kicked off for mischief like
> forging routing packets -- and if someone started hosing me down with
> any one of several really nasty packet based attacks I'm familiar with
> I would expect action to be taken against them.

Unix is broken.  Windows and DOS are fragile and under construction.

Servers should have built in limits, that cause them to spit back
packets from unknown clients that are unreasonable or strain the
system.

For example an SMTP server should have a default limit on volume
per address and per client, with the user being able to vary
such limits for particular clients or addresses -- trusted or
hostile clients.

At present most unix utilities have arbitrary fixed length internal
buffers for processing variable length fields.  If you overflow 
the buffer by sending pathological data you will crash the system.  
If you know machine code, and you overflow the buffer with 
carefully chosen data then instead of a random crash you can
get the server to do some particular unexpected thing -- for
example the internet worm caused the server to execute a
file that the mail server had just received.

This is one of many bugs that make attacks possible.

This is a bug.  It can and regularly does crash your
system and cause loss of data even if nobody attacks.

Every flaw in the system causes more havoc by accident
than it does by malice.  The correct solution is not
to create institutions capable of dealing effectively
with hostile acts.   The big problem is bugs that urgently
need fixing.

Now even if all the bugs were fixed some really evil
packet based attacks are still possible, in which case
social action -- cutting the connectivity of a host
that generates bad packets -- is still necessary, but 
again bad packets are more common by malfunction
than by malice.

> I doubt it. It really hasn't proved to be an actual problem thus
> far. If anything, the limiting factor on scalability is the fact that
> the net has no locality of reference, which is making routing design
> harder and harder. Routing is currently THE big unsolved problem on
> the net -- something outsiders to the IETF rarely suspect, because the
> engineers have been faking it so well for so long. Unfortunately, all
> the good solutions to the routing problem are mathematically
> intractable -- and the practical ones are leading to bad potential
> long term problems..

This is inaccurate.  Optimal solutions to the routing problem are
mathematically intractable.  Tolerable solutions are mathematically
tractable.  For realistic routing problems, tractable approximations
are only worse than an optimal solution by a modest factor.

There are real world problems where tractable approximations
are not good enough, but routing is not one of them.

Of course I am sure Perry is correct when he says that
the tractable approximations that we are currently using 
fail to scale, but this is not a fundamental unsolved 
problem in mathematics -- it is merely yet another bug.

 ---------------------------------------------------------------------
We have the right to defend ourselves and our       
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are.  True law derives from this right, not from    James A. Donald
the arbitrary power of the omnipotent state.        jamesd@netcom.com

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