[cod] Game server whitelisting rules

Boyd G. Gafford Ph.D. drboyd at westportresearch.com
Tue Apr 17 14:49:30 EDT 2012


Unfortunately OpenVZ does not have all the needed iptables modules 
ported yet, so the new protection scheme won't work with OpenVZ.  It 
will work with Xen though (that's what I use on my VPS's) and of course 
regular non-virtualized Linux servers.

Hopefully OpenVZ will eventually get the needed modules implemented.

Specifically, the protection scripts use the following iptables modules:

1) recent (with --reap option, for whitelisting)
2) string (with |hexval| matching, for basic packet content matching)
3) limit (for general packet rate limiting)
4) hashlimit (for player whitelisted packet rate limiting)

Some older implementations of iptables do not have the --reap option on 
the recent module, which is absolutely necessary to expire whitelisted 
players after they have left the game server.

To determine if your server supports --reap, just type

man iptables

and then

/--reap[enter]

If you find your cursor on the --reap option in the iptables manual, you 
are good to go.

Thanks,

/Boyd/
/__________________________________
Boyd G. Gafford Ph.D.
Manager of Software Development
Westport Research Associates Inc.
7001 Blue Ridge Blvd
Raytown, MO 64133
(816) 358-8990
drboyd at westportresearch.com
/

On 04/17/2012 01:29 PM, Robert Mount wrote:
> Would love to see this integrated with csf/lfd somehow.
>
> http://www.configserver.com/cp/csf.html
>
> --Rob
>
> On Tue, Apr 17, 2012 at 2:09 PM, Brandon R. Miller
> <brandonm at branzone.com>  wrote:
>> Will it work on CentOS 5.x with iptables 1.3.5?
>>
>> - Brandon M.
>>
>> On 4/17/2012 10:12 AM, Boyd G. Gafford Ph.D. wrote:
>>
>> Just wanted to let everyone know that I am making the dynamic whitelisting
>> iptables rules I have been testing available to anyone who runs a
>> Q3-protocol server under Linux and wants to try them out.  These rules were
>> designed for the most severe of all attacks, and that is attacks where the
>> source IP is spoofed and is random.  It also works for attacks from a single
>> IP as well, as well as indirect reflection attacks.
>>
>> We have 2 commercial server companies using these rules currently in their
>> production environment, and I am currently working with two more.  I also
>> have test servers running on several VPS's that I use for development.
>>
>> So what do the iptables do?  Here's the list:
>>
>> 1) Players have their IP saved automatically at the kernel level when they
>> join a game server, and then those IPs are used as a filter for other
>> rules.  When they leave the game server the IP is retired after 10 minutes.
>> (This is what we call a whitelisted player).  This is the main guts of the
>> protection, as identifying valid players is important to mitigating attacks.
>>
>> 2) Server query packets like 'getstatus' and 'getinfo' are rate limited to
>> 10/sec to prevent lag when they are used in a DOS attack.  Players that are
>> whitelisted have their packets allowed (so they can see server status while
>> in game even during an attack).
>>
>> 3) 'getchallenge' packets (normally used by a player to join the game) are
>> rate limited to 2/sec, to prevent lag when they are used in a DOS attack.
>> Players that are whitelisted always have their requests to join the server
>> processed.  This allows a player who was recently playing the ability to
>> join the server again, even when the DOSer is trying to lock down the
>> population on the server by spamming fake players joining.
>>
>> 4) All other packets are rate limited per whitelisted player IP to no more
>> than 100/second, to prevent lag when a DOSer has stolen a valid player IP
>> address and is attacking with it in an attempt to break through the
>> whitelist rules.
>>
>> 5) Attempts to use your game server as a reflector to attack other game
>> servers is blocked (due to rate limiting in 1-4).
>>
>> 6) Reflection attack packets hitting your server are dropped (again due to
>> rate limiting in 1-4).
>>
>> 7) A custom packet (not part of the Q3 protocol) can be sent by a player to
>> break into and join a game that is under 24/7 'getchallenge' attack.  This
>> is one of the slicker features of the iptables rules, as this 'server
>> lockdown' DOS attack is now easily breached.
>>
>>
>> The iptables rules are added dynamically per server IP:PORT pair.  That way
>> the rules affect nothing but UDP packets to that game server.  No other
>> types of packets are affected whatsoever.  To make it easy, the rules have
>> been put into shell scripts.
>>
>> Example:  Protect the game running on 10.1.2.3 port 28000.
>>
>> # ./protectgame.sh 10.1.2.3 28000
>>
>> Example:  Show the iptables rules currently protecting the game running on
>> 10.1.2.3 port 28000.
>>
>> # ./listgame.sh 10.1.2.3 28000
>>
>> Example:  Remove the iptables rules protecting the game running on 10.1.2.3
>> port 28000.
>>
>> # ./unprotectgame.sh 10.1.2.3 28000
>>
>> Rather than just send the scripts to the whole list here, I've decided to
>> ask anyone interested to Email me personally and request it.  If you run a
>> commercial gaming service (or even your own COD server and agree not to
>> share it with anyone else), I will be happy to send it to you and help you
>> understand how to use it in your environment.
>>
>> Thanks,
>>
>>    Boyd
>>
>> __________________________________
>> Boyd G. Gafford Ph.D.
>> Manager of Software Development
>> Westport Research Associates Inc.
>> 7001 Blue Ridge Blvd
>> Raytown, MO 64133
>> (816) 358-8990
>> drboyd at westportresearch.com
>>
>>
>>
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