Re: New DoS attack

[BlueBoar () THIEVCO COM (Blue Boar)]

Dave Booth wrote:
> Sorry, BB - normally I read your comments here with much head-nodding
> and agreement but this time I have to disagree. As a previous poster
> pointed out if you are reimplementing TCP in UDP gaming protocols you
> may as well just use TCP. Lots of reasons, all performance-related, why
> game designers dont want to do that. Assuming 2-way UDP traffic is
> possible through whatever firewalling setup is in place (or they wouldnt
> be playing now!) how do you hit the back-channel nightmares you worry
> about with a scheme like this...?

No, just the initial 3-way handshake.  Should be a grand total of one
extra packet and about 2 extra round trips, assuming no retransmits
required.  All at the beginning.  Shouldn't hurt gameplay one bit.

> Game client makes tcp connection to server and requests to join the
> game.
> Server responds (as part of the same tcp session) with a unique token,
> remembers it and the clients IP then signs off.
> Client initiates normal UDP game connection including the token in
> every datagram.
> Server silently ignores all incoming datagrams where there isnt a valid
> token that matches up with the IP address the datagram claims to come
> from.
>
> In each case the connection is initiated by the client, but that makes
> blind spoofing to create bogus connections impossible as there has to be
> a two-way conversation in tcp to pass the token before the UDP join game
> request (which doesnt get modified at all apart from the inclusion of
> the token) will be accepted by the server. If it isnt blind spoofing but
> is done by someone who can sniff the network then as you so rightly
> pointed out the victim is in a world of hurt anyway and spoofed game
> connections are the least of their problems.

You're right, that would work fine.  It's extra work above what I was
proposing, though.  You can take any portion of the features from
TCP and put them atop UDP manually.  That's what UDP is for in my mind.

                                        BB