[cod] Some new cool iptables!
Boyd G. Gafford Ph.D.
drboyd at westportresearch.com
Fri Mar 9 11:41:00 EST 2012
Yeah, if they flood "getstatus" and "getinfo", during the attack your
server will not be visible from the master list.
If they flood "getchallenge", during the attack nobody will be able to
join your server.
Once the attack ends, then you'll be visible again and people can join
normally.
Since most of these attacks are from spoofed random IP addresses
(millions of them), you can't limit per IP, as no IP repeats.
This set of rules is about the best I've found short of doing a
whitelisted server, where you only allow IP's of known good players, and
block everything else, and then people have to join the server with
"connect IP:PORT". That's fairly inconvenient for most players, so
these rules are about as good as you can get and still allow usage from
the master list.
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 03/09/2012 10:00 AM, Ruediger Meier wrote:
> On Friday 09 March 2012, Boyd G. Gafford Ph.D. wrote:
>> Just wanted to share these with the COD group here. I've been
>> running these rules for about a week now, and they have been working
>> wonderfully. Let me know if you end up using them and how they work
>> for you.
> Be aware that now it's easy for a attacker to make your servers
> invisible for others by flooding your limit rules.
> Maybe you should rather limit per ip.
>
> cu,
> Rudi
>
>> #!/bin/bash
>> # The main logic of ServerArk, all done with iptables!
>> # Version 1.01
>> # (C) 2012 Boyd G. Gafford Ph.D. (Usage is under the LGPL)
>> # To contact me, simply post on the forum at elitewarriors.net.
>> #
>> # Please note these rules ONLY affect UDP packets to the game
>> servers, nothing else!
>> # This script will protect all Q3-protocol servers on the port 28960.
>> It protects
>> # against both 'getstatus' and 'getinfo' attacks, as well as
>> 'getchallenge' atttacks,
>> # even from a UDP flood with random source IPs.
>>
>> # Add a limit/drop chain for "getstatus" packets that limits it to 10
>> a second for all servers.
>> # If you are only protecting one server, you can set the number from
>> 10 down to 4 (or 2 even).
>> iptables -N LIMITSTAT
>> iptables -A LIMITSTAT -p udp -m limit --limit 10/sec --limit-burst 10
>> -j ACCEPT
>> iptables -A LIMITSTAT -p udp -j DROP
>>
>> # Add a limit/drop chain for "getinfo" packets that limits it to 10 a
>> second for all servers.
>> # If you are only protecting one server, you can set the number from
>> 10 down to 4 (or 2 even).
>> iptables -N LIMITINFO
>> iptables -A LIMITINFO -p udp -m limit --limit 10/sec --limit-burst 10
>> -j ACCEPT
>> iptables -A LIMITINFO -p udp -j DROP
>>
>> # Add a limit/drop chain for "getchallenge" packets that limits it to
>> 5 a second for all servers.
>> # If you are only protecting one server, you can set the number from
>> 5 down to 2. Setting it
>> # at 2 means only 2 players could connect to the server per second.
>> Set LIMITCONN to the
>> # same, as there is one getchallenge/connect packet sequence per
>> valid player connection.
>> iptables -N LIMITCHLG
>> iptables -A LIMITCHLG -p udp -m limit --limit 5/sec --limit-burst 5
>> -j ACCEPT
>> iptables -A LIMITCHLG -p udp -j DROP
>>
>> # Add a limit/drop chain for "connect" packets that limits it to 5 a
>> second for all servers.
>> # If you are only protecting one server, you can set the number from
>> 5 down to 2. Setting it
>> # at 2 means only 2 players could connect to the server per second.
>> Set LIMITCHLG to the
>> # same, as there is one getchallenge/connect packet sequence per
>> valid player connection.
>> iptables -N LIMITCONN
>> iptables -A LIMITCONN -p udp -m limit --limit 5/sec --limit-burst 5
>> -j ACCEPT
>> iptables -A LIMITCONN -p udp -j DROP
>>
>> # Add a limit chain that prevents more than 70 packets a second per
>> player. # This is the main logic of ServerArk, but just performed by
>> an iptable rule.
>> # We allow up to 128 players which is enough for 4 servers full (at
>> 32 players each).
>> # If you only have one server, you could the size and max to 32.
>> # If you have players who have manually set their packet rate up to
>> 100, just change the 70 to 100.
>> iptables -N LIMITPLRS
>> iptables -A LIMITPLRS -p udp -m hashlimit --hashlimit-name PLAYERS
>> --hashlimit-above 70/sec --hashlimit-burst 70 --hashlimit-mode
>> srcip,srcport --hashlimit-htable-size 128 --hashlimit-htable-max 128
>> --hashlimit-htable-gcinterval 1000 --hashlimit-htable-expire 10000 -j
>> DROP iptables -A LIMITPLRS -p udp -j ACCEPT
>>
>> # Add the rules to pick out the various special packets and send them
>> to appropriate limit chains.
>> # To protect 5 ports, just specify a range like "--dport 28960:28964"
>> below. iptables -A INPUT -p udp --dport 28960-m string --string
>> "getstatus" --algo bm --from 32 --to 33 -j LIMITSTAT
>> iptables -A INPUT -p udp --dport 28960-m string --string "getinfo"
>> --algo bm --from 32 --to 33 -j LIMITINFO
>> iptables -A INPUT -p udp --dport 28960-m string --string
>> "getchallenge" --algo bm --from 32 --to 33 -j LIMITCHLG
>> iptables -A INPUT -p udp --dport 28960-m string --string "connect"
>> --algo bm --from 32 --to 33 -j LIMITCONN
>>
>> # Send all other packets (normal player packets) to the limit players
>> chain. # A port range like "--dport 28960:28964" could also be used
>> here as well. iptables -A INPUT -p udp --dport 28960-j LIMITPLRS
>> /
>> /Also, you can do an "iptables -L -v -n" to see what kind of attacks
>> these rules have blocked. Here's an example of this command after a
>> "getchallenge" flood attack from random IPs, on our Dallas server
>> running on port 29070.
>>
>> ew at server1:~$ sudo iptables -L -v -n
>> Chain INPUT (policy ACCEPT 11368 packets, 1538K bytes)
>> pkts bytes target prot opt in out source
>> destination
>> 3880 177K LIMITSTAT udp -- * * 0.0.0.0/0
>> 0.0.0.0/0 udp dpt:29070 STRING match "getstatus" ALGO name
>> bm FROM 32 TO 33
>> 14036 617K LIMITINFO udp -- * * 0.0.0.0/0
>> 0.0.0.0/0 udp dpt:29070 STRING match "getinfo" ALGO name bm
>> FROM 32 TO 33
>> 37M 1620M LIMITCHLG udp -- * * 0.0.0.0/0
>> 0.0.0.0/0 udp dpt:29070 STRING match "getchallenge" ALGO
>> name bm FROM 32 TO 33
>> 17 4989 LIMITCONN udp -- * * 0.0.0.0/0
>> 0.0.0.0/0 udp dpt:29070 STRING match "connect" ALGO name bm
>> FROM 32 TO 33
>> 237K 17M LIMITPLRS udp -- * * 0.0.0.0/0
>> 0.0.0.0/0 udp dpt:29070
>>
>> Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
>> pkts bytes target prot opt in out source
>> destination
>>
>> Chain OUTPUT (policy ACCEPT 343K packets, 54M bytes)
>> pkts bytes target prot opt in out source
>> destination
>>
>> Chain LIMITCHLG (1 references)
>> pkts bytes target prot opt in out source
>> destination
>> 40025 1761K ACCEPT udp -- * * 0.0.0.0/0
>> 0.0.0.0/0 limit: avg 5/sec burst 5
>> *37M 1618M DROP* udp -- * * 0.0.0.0/0
>> 0.0.0.0/0
>>
>> Chain LIMITCONN (1 references)
>> pkts bytes target prot opt in out source
>> destination
>> 17 4989 ACCEPT udp -- * * 0.0.0.0/0
>> 0.0.0.0/0 limit: avg 5/sec burst 5
>> 0 0 DROP udp -- * * 0.0.0.0/0
>> 0.0.0.0/0
>>
>> Chain LIMITINFO (1 references)
>> pkts bytes target prot opt in out source
>> destination
>> 14036 617K ACCEPT udp -- * * 0.0.0.0/0
>> 0.0.0.0/0 limit: avg 10/sec burst 10
>> 0 0 DROP udp -- * * 0.0.0.0/0
>> 0.0.0.0/0
>>
>> Chain LIMITPLRS (1 references)
>> pkts bytes target prot opt in out source
>> destination
>> 1642 104K DROP udp -- * * 0.0.0.0/0
>> 0.0.0.0/0 limit: above 70/sec burst 70 mode srcip-srcport
>> htable-size 128 htable-max 128
>> 236K 17M ACCEPT udp -- * * 0.0.0.0/0
>> 0.0.0.0/0
>>
>> Chain LIMITSTAT (1 references)
>> pkts bytes target prot opt in out source
>> destination
>> 3868 177K ACCEPT udp -- * * 0.0.0.0/0
>> 0.0.0.0/0 limit: avg 10/sec burst 10
>> 12 516 DROP udp -- * * 0.0.0.0/0
>> 0.0.0.0/0
>>
>> Notice the bolded packet/byte statistics for the "getchallenge" drop
>> chain named LIMITCHLG. A total of 37 million packets dropped. I was
>> on the game during this attack, and although the server did lag a bit
>> from the sheer size of the flood (almost saturating the bandwidth),
>> nobody lagged out. Without this rule, the game server deadlocked.
>>
>> Also notice you can tell how many players have connected to the
>> server, as the LIMITCONN status shows 17 packets accepted. So during
>> this time we had 17 players join the game.
>>
>> You can also see how many people requested the servers in game (as
>> well as other services like GameTracker getting info on you), as that
>> corresponds to the LIMITSTAT and LIMITINFO chains.
>>
>> Another cool thing you can do is "cat /proc/srv/ipt_hashlimit/PLAYERS
>> to see the IP addresses of all the players currently connected to the
>> server(s). Once a player quits playing, he goes out of this file
>> automatically after 10 seconds.
>>
>> I may refine these a bit further, but for now, these seem to be
>> working well on our VPS.
>>
>> Thanks,
>>
>> /Boyd/
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