This document consists of two parts. The first is setting up a firewall (using iptables) on the [[HN]], which will restrict traffic to the VEscontainers. The effect would emulate, as far as the VEs containers and their customers are concerned, an external hardware firewall controlled by the sysadmin. The second is setting up a firewall that protects the HN itself but still allows traffic to the VEscontainers, thus allowing individual VEs containers to define their own iptables.

Setting up While the firewalls shown here can be accomplished using iptables manually (or using Fedora core's iptables service), the methods presented here are especially modular and easy to modify. This is important when you have 20+ containers and a HN-based firewalllot of other things to be doing...

Setting up The exception to this is the nameserver, which we want open to the world. We use it as a firewall that allows per-VE configurationcaching nameserver for our containers and also to host DNS for a few customer domain.

Although it is possible to use iptables within each VE individually, I've not been able to get this to work reliably, but more importantly we simply don't trust our customers to effectively manage their own firewalls and prefer to keep these many firewalls consolidated into one place. As such, this content is missing. You are invited to fill it in, if you get to it before I do. == Simple firewall configuration independent of IP addresses:)vzfirewall ==

Traffic_accounting_with_iptablesNote that it is recommended to use hostnames instead of IP addresses here, so the configuration is persistent for VE movements to different IP-address: you just need to run <code>vzfirewall -a</code> again after movement. It is also reboot-safe, as the rules are applied to <code>/etc/sysconfig/iptables</code> (at RHEL systems). Vzfirewall and its documentation are available at [http://en.dklab.ru/lib/dklab_vzfirewall/ http://en.dklab.ru/lib/dklab_vzfirewall/]. == An alternative from the author of Shorewall == For those who might find the solution provided in this wiki article unsatisfactory (for whatever reason), the creator of Shorewall (Tom Eastep) has written a nice article explaining how to use Shorewall on an OpenVZ host node to manage the host node, containers, and more... with quite a complex setup as an example. The article IS NOT an introduction to Shorewall for beginners, so some pre-existing knowledge and understanding of Shorewall may be required. Shorewall and OpenVZ by Tom Eastep - http://www.shorewall.net/OpenVZ.html See also this OpenVZ Forum posting - http://forum.openvz.org/index.php?t=msg&goto=16406& == Setting up a HN-based firewall == This setup emulates (to the containers anyway) an external hardware firewall. It protects the HN from any access and then defines what services and ports are allowed/banned for individual containers. This leaves the firewall controlled by the site administrator, not be individual containers and the hackers who've gotten into them. ;) First off, let's disable Fedora's existing <code>iptables</code> service:<pre>service iptables stopchkconfig iptables off</pre> Now create the new <code>firewall</code> service. This code should be <code>/etc/init.d/firewall</code> and then should be chmod'd 755.<pre>#!/bin/sh# firewall Start iptables firewall# chkconfig: 2345 97 87# description: Starts, stops and saves iptables firewall# This script sets up the firewall for the INPUT chain (which is for# the HN itself) and then processes the config files under# /etc/firewall.d to set up additional rules in the FORWARD chain# to allow access to containers' services.# http://wiki.openvz.org/Setting_up_an_iptables_firewall . /etc/init.d/functions # the IP block allocated to this serverSEGMENT="192.168.0.0/24"# the IP used by the hosting server itselfTHISHOST="192.168.0.1"# services that should be allowed to the HN;# services for containers are configured in /etc/firewall.d/*OKPORTS="53"# hosts allowed full access through the firewall,# to all containers and to this serverDMZS="12.34.56.78 90.123.45.67" purge() { echo -n "Firewall: Purging and allowing all traffic" iptables -P OUTPUT ACCEPT iptables -P FORWARD ACCEPT iptables -P INPUT ACCEPT iptables -F success ; echo} setup() { echo -n "Firewall: Setting default policies to DROP" iptables -P INPUT DROP iptables -P FORWARD DROP iptables -I INPUT -j ACCEPT -m state --state ESTABLISHED,RELATED iptables -I FORWARD -j ACCEPT -m state --state ESTABLISHED,RELATED iptables -I INPUT -j ACCEPT -i lo iptables -I FORWARD -j ACCEPT --source $SEGMENT success ; echo  echo "Firewall: Allowing access to HN" for port in $OKPORTS ; do echo -n " port $port" iptables -I INPUT -j ACCEPT -s $SEGMENT -d $THISHOST --protocol tcp --destination-port $port iptables -I INPUT -j ACCEPT -s $SEGMENT -d $THISHOST --protocol udp --destination-port $port success ; echo done for ip in $DMZS ; do echo -n " DMZ $ip" iptables -I INPUT -i eth0 -j ACCEPT -s $ip iptables -I FORWARD -i eth0 -j ACCEPT -s $ip success ; echo done  CTSETUPS=`echo /etc/firewall.d/*` if [ "$CTSETUPS" != "/etc/firewall.d/*" ] ; then echo "Firewall: Setting up container firewalls" for i in $CTSETUPS ; do . $i echo -n " $CTNAME CT$CTID" if [ -n "$BANNED" ]; then for source in $BANNED ; do iptables -I FORWARD -j DROP --destination $CTIP --source $source ; done fi if [ -n "$OPENPORTS" ]; then for port in $OPENPORTS ; do iptables -I FORWARD -j ACCEPT --protocol tcp --destination $CTIP --destination-port $port ; done for port in $OPENPORTS ; do iptables -I FORWARD -j ACCEPT --protocol udp --destination $CTIP --destination-port $port ; done fi if [ -n "$DMZS" ]; then for source in $DMZS ; do iptables -I FORWARD -j ACCEPT --protocol tcp --destination $CTIP --source $source ; done for source in $DMZS ; do iptables -I FORWARD -j ACCEPT --protocol udp --destination $CTIP --source $source ; done fi [ $? -eq 0 ] && success || failure echo done fi} case "$1" in start) echo "Starting firewall..." purge setup ;; stop) echo "Stopping firewall..." purge ;; restart) $0 stop $0 start ;; status) iptables -n -L ;; *) echo "Usage: $0 <start|stop|restart|status>" ;;esac</pre> Note: This will only allow access to the HN from the hosts/networks defined in SEGMENT. If you'd like to open up the OKPORTS on the HN to everybody, you can remove the ''-s $SEGMENT'' parameters from the iptables commands under the "Firewall: Allowing access to HN" section. The modified lines would look like this: <pre>iptables -I INPUT -j ACCEPT -d $THISHOST --protocol tcp --destination-port $portiptables -I INPUT -j ACCEPT -d $THISHOST --protocol udp --destination-port $port</pre> The above script can be called like this:<pre>service firewall startservice firewall stopservice firewall restartservice firewall status</pre> It will set up the firewall for the HN according to the parameters you specified for OKPORTS, DMZs, etc. and then it will call each file under /etc/firewall.d and process its configuration. So create a file under /etc/firewall.d The exact filename isn't important, as long as it's meaningful to you, e.g. <code>ExampleCompany</code> or <code>ve12</code> and give it content like this: <pre># This file is processed by /etc/init.d/firewallCTID="1" # the container's ID#CTNAME="Customer1" # A human-friendly label for the containerCTIP="192.168.1.34" # the IP address for this container OPENPORTS="80 443" # ports that should be universally opened # to the entire InternetDMZS="1.2.3.0/24 5.6.7.8/32" # IPs and blocks that should have full access # to the container's servicesBANNED="" # IPs and blocks that should be entirely # blocked from the container's services</pre> And there you go.  Note: You can only put one IP address inside the CTIP variable, but if your container has multiple IP addresses you can create a copy of the file for each IP address. Go ahead and start the firewall and check its status:<pre>service firewall restartservice firewall status</pre> As you can see, you can now add and edit the configurations for individual containers very easily. This method proves a lot easier to manage than Fedora's iptables-config mechamism! To make the firewall service automatically start when the HN boots, run<pre>chkconfig --add firewall</pre> === Debian Notes === The setup above works fine for Debian as well, however /etc/init.d/functions is missing. Here is a very simple version that you can use:  # /etc/init.d/functions success() { echo -n "...success" } failure() { echo -n "...failure" } == Setting up a firewall that allows per-container configuration == This setup configures iptables on the HN to disallow access to all hosts, including the containers. However, it allows all traffic into the containers so they may define their own iptables rules and therefore manage their own firewall. <pre>iptables -P FORWARD ACCEPTiptables -F FORWARD</pre> This will remove all rules for the FORWARD chain so all packets can pass back and forth between containers and the outside world. If you want to use a firewall inside a container, please load these modules BEFORE starting the container: <pre>modprobe xt_tcpudpmodprobe ip_conntrack</pre> If you do not, you will get an error like this: "iptables: No chain/target/match by that name"* Note: xt_tcpudp module seem to be included in the kernel packages of Debian 6, but not of CentOS 6. If you want to use stateful firewall rules (and you should!) you will also need to make sure that 'ipt_state' is in the 'IPTABLES' option in your vz.conf file: <pre>IPTABLES="ipt_REJECT ipt_tos ipt_limit ipt_multiport iptable_filter iptable_mangle ipt_TCPMSS ipt_tcpmss ipt_ttl ipt_length ipt_state"</pre> Also make sure the 'xt_state' module is loaded on the host: <pre>modprobe xt_state</pre>  Above information is outdated, to enable iptables you need to make sure that CT.conf(CT - id of your container, 100 for example) contains following line: <pre>NETFILTER="full"</pre> When this done, you should reboot your container and iptables should work properly. == See also == * [[Traffic accounting with iptables]]* [http://www.readymakers.com/blog/how-to-enable-iptables-in-openvz-container/ How to enable IPtables in OpenVZ container] (Frank Taveras) - Lack of modprobe modules on HN. [[Category: Networking]]