Introduction
OpenVPN is an opensource Virtual Private Networking (VPN) solution which can be downloaded freely on the Internet. It also included in almost every Linux distro to-date, so it can be easily installed using your distro’s favourite package manager tools. It uses the SSL/TLS VPN stacks, which makes it different from almost every other VPN solution (which are usually based on IPSec).
This guide will described how OpenVPN can be installed and configured on a Debian system, so that it can be used as a means to connect to your home and company networks.
The Server
First install the openvpn package:
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# apt-get install openvpn |
If apt-get suggests extra packages to install, just install them!
Two networks will be created:
* one to create a secure network for servers: 192.168.1.0/24
* one to create a secure network of client PC’s, Macbooks, Linux desktops, … : 10.66.99.0/24
Next, we will need an OpenVPN configuration file for the OpenVPN we’re about to create:
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.oO( ieyasu | /etc/openvpn )Oo. cat server.conf # LIKE A BOSS local 176.9.64.17 port 1194 proto udp dev tun0 mode server tls-server persist-key persist-tun #certificates and encryption ca ca.crt cert ieyasu.crt key ieyasu.key dh dh2048.pem tls-auth ta.key 0 cipher AES-256-CBC comp-lzo server 192.168.1.0 255.255.255.0 route 10.66.99.0 255.255.255.0 ifconfig-pool-persist ipp.txt push "route 10.66.99.0 255.255.255.0" # separate client configs client-config-dir ccd #log and security user nobody group nogroup keepalive 5 30 status /var/log/openvpn-status.log verb 3 |
We will also need some firewall rules allowing our OpenVPN traffic:
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$IPTABLES -A INPUT -i tun0 -s 192.168.1.0/24 -d 192.168.1.0/24 -j ACCEPT $IPTABLES -A INPUT -i tun0 -s 10.66.99.0/24 -d 192.168.1.1 -j ACCEPT $IPTABLES -A INPUT -i tun0 -s 10.66.99.0/24 -d 10.66.99.0/24 -j ACCEPT $IPTABLES -P FORWARD DROP $IPTABLES -A FORWARD -i tun0 -s 10.66.99.0/24 -d 192.168.1.1 -j ACCEPT $IPTABLES -A FORWARD -i tun0 -s 10.66.99.0/24 -d 10.66.99.0/24 -j ACCEPT $IPTABLES -A FORWARD -i tun0 -s 192.168.1.0/24 -d 192.168.1.0/24 -j ACCEPT $IPTABLES -A INPUT -p udp --dport 1194 -j ACCEPT |
Now we need to create a CCD file for each client. The CCD file contains the network settings for the connection OpenVPN clients.
Example:
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.oO( ieyasu | ~ )Oo. cat /etc/openvpn/ccd/bear ifconfig-push 192.168.1.11 192.168.1.12 .oO( ieyasu | ~ )Oo. cat /etc/openvpn/ccd/lion ifconfig-push 10.66.99.3 10.66.99.4 |
The final thing to do for the OpenVPN server, is to create the x509 certificates.
First:
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# mkdir /etc/openvpn/easy-rsa/ # cp -R /usr/share/doc/openvpn/examples/easy-rsa/2.0/* /etc/openvpn/easy-rsa/ |
This will copy the required tools for creating the certificates for both the server as the clients.
Next, specify your information in /etc/openvpn/easy-rsa/vars, only the bottom is of real importance:
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vi /etc/openvpn/easy-rsa/vars *snip* # These are the default values for fields # which will be placed in the certificate. # Don't leave any of these fields blank. export KEY_COUNTRY="BE" export KEY_PROVINCE="LIM" export KEY_CITY="As" export KEY_ORG="MORETRIX" export KEY_EMAIL="info@moretrix.com" |
Finally we will create the CA and the server certificate (we’re making a 2048 one!):
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# cd /etc/openvpn/easy-rsa/ # chown -R root:admin . # chmod g+w . # source ./vars # ./clean-all # ./build-dh # ./pkitool --initca # ./pkitool --server server # cd keys # openvpn --genkey --secret ta.key # cp server.crt server.key ca.crt dh2048.pem ta.key ../../ |
Finally we just need to start the OpenVPN service and the server is ready!
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# /etc/init.d/openvpn restart |
The Clients
Every client will need his own x509 certificate:
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# cd /etc/openvpn/easy-rsa # ./pkitool bear |
bear is the name of the client host.
Now create a client configuration file, let’s call it bear.conf and we’ll save in it /tmp/client_config/:
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client dev tun remote 176.9.64.17 1194 nobind resolv-retry infinite persist-key persist-tun ca ca.crt cert bear.crt key bear.key tls-auth ta.key 1 cipher AES-256-CBC comp-lzo verb 3 |
Finally grab all the files the client will need
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# cd /etc/openvpn/easy-rsa/keys/ # cp ca.crt ta.key bear.crt bear.key /tmp/client_config/ # cd /tmp/client_config/ # ls -ltr total 24 -rw------- 1 root root 636 Jun 22 16:17 ta.key -rw-r--r-- 1 root root 1537 Jun 22 16:17 ca.crt -rw-r--r-- 1 root root 5053 Jun 22 16:17 bear.crt -rw------- 1 root root 1704 Jun 22 16:17 bear.key -rw-r--r-- 1 root root 185 Jun 22 16:17 bear.conf |
If the client also uses the OpenVPN command line tools, just copy the above files to /etc/openvpn and restart the openvpn service.
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root@bear:/etc/openvpn# ls -ltr total 28 -rwxr-xr-x 1 root root 1357 2011-03-11 02:03 update-resolv-conf -rw-r--r-- 1 root root 636 2011-06-20 22:40 ta.key -rw-r--r-- 1 root root 1537 2011-06-20 22:40 ca.crt -rw-r--r-- 1 root root 1704 2011-06-20 22:40 bear.key -rw-r--r-- 1 root root 5053 2011-06-20 22:40 bear.crt -rw-r--r-- 1 root root 185 2011-06-21 20:13 bear.conf root@bear:/etc/openvpn# /etc/init.d/openvpn restart |
Resources
* https://help.ubuntu.com/community/OpenVPN
* http://openvpn.net/index.php/open-source/documentation/howto.html
* http://openvpn.net/index.php/open-source/documentation/miscellaneous/76-ethernet-bridging.html