Changes

This document consists of two parts. The first is setting up a firewall (using iptables) on the [[HN]], which will restrict traffic to the containers. The effect would emulate, as far as the 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 containers, thus allowing individual containers to define their own iptables.

== Simple firewall configuration independent to of IP addresses: vzfirewall ==

<code>Vzfirewall</code> tool allows you to open/close ports for incoming connections with no dependencies to foreign IP addresses. E.g. you may allow a hostname <code>release.prod.example.com</code> to connect to port 5432 of VE 1234 and leave all other ports closed by modifying <code>1234.conf</code> file adding multiline <code>FIREWALL</code> directive directives into it:

Note 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, because as the rules are applied to <code>/etc/sysconfig/iptables</code> (at RHEL systems).

You== 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 got 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 in onewill call each file under /etc/firewall.d and process its configuration. So create a file under /etc/firewall. Couldnd 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 it betetrone 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" }