After helping some people (here and on irc) to setup their OpenVPN server I would like to start a collection of useful tips regarding the operation of an OpenVPN server.
First the basic steps:
- Click on the "enable TUN/TAP device" within for server panel and restart the vps. [for OpenVZ]
After that a
cat: /dev/net/tun: File descriptor in bad state
apt-get install openvpn
If /dev/net/tun is missing
openvpn --mktun --dev tun0
Hard way (yup there are still images out there which do not have a /dev/net):
mkdir -p /dev/net mknod /dev/net/tun c 10 200 chmod 600 /dev/net/tun
Setup configuration of openvpn
cp -r /usr/share/doc/openvpn/ /etc/ cd /etc/openvpn/examples/easy-rsa/2.0 nano vars
Setup the last exports to save you some typing:
export KEY_SIZE=2048 export KEY_COUNTRY="" export KEY_PROVINCE="" export KEY_CITY="" export KEY_ORG="" export KEY_EMAIL="" export KEY_CN=changeme export KEY_NAME=changeme export KEY_OU=changeme
Key size should be at least 2048 bit!
Of course no empty values ...
If they key tools reporting that they cannot find the openssl lib...
Change following line (the double [[:digit:]] is wrong):
elif $OPENSSL version | grep -E "1\.0\.[[:digit:]]" > /dev/null; then
Start generating the keys:
./clean-all [to clean all generated stuff - if you want to start right from the beginning] ./build-ca [certificate authority of all your certs] ./build-key-server servername [cert for server] ./build-key clientname [certs per client] ./build-dh [dh parameter for key-exchange algorithm]
Copy keys to openvpn server
mkdir /etc/openvpn/keys cd keys cp ca.crt ca.key dh1024.pem server.crt server.key /etc/openvpn/keys [depends on your naming of the build-* calls, if you called your server mybox it is e.g. mybox.crt and mybox.key] chmod 600 /etc/openvpn/keys/*
Creating the server config
cd /etc/openvpn/examples/sample-config-files/ gunzip server.conf.gz cp server.conf /etc/openvpn/ cd /etc/openvpn/ nano /etc/openvpn/server.conf
Alterting the config
port 1149 #[port you want to use] dev tun #[device type you want to use] #relative paths of the keys: ca keys/ca.crt cert keys/servch.crt key keys/servch.key dh keys/dh1024.pem server 10.10.10.0 255.255.255.0 #[network of openvpn server - server itself will get 10.10.10.1] push "redirect-gateway def1 bypass-dhcp" #[if you want to surf through the vpn] client-to-client #[if each openvpn client should see the other openvpn clients (gaming)] comp-lzo #[compression is good] max-clients 3 #[number of concurrent users] user nobody group nogroup #[downgrade rights of openvpn for security] persist-key persist-tun #[nobdy cannot alter devices - so persist there settings] status openvpn-status.log log-append openvpn.log #[logging is good for checking problems]
Track the usage of your openvpn server
OpenVPN server does have some nice hookups that you can use to modify its workflow. One nice feature are following hooks (added to the server config):
script-security 3 system client-connect /etc/openvpn/client-login.sh client-disconnect /etc/openvpn/client-logout.sh
So the scripts are called whenever a client connects or disconnects!
#!/bin/bash #Send an email when a client connects with today's time and date NOW="$(date +"%H:%M:%S - %Y-%m-%d")" sendmail [email protected].com <
#!/bin/bash #Send an email when a client connects with today's time and date NOW="$(date +"%H:%M:%S - %Y-%m-%d")" sendmail [email protected] <
Yup I really like this global vars. So this script can be altered to put this information into a csv file or into a database.
You get all information you need - and the used bandwith too.
chmod +x /etc/openvpn/*.ssh
And we are done.
Next hook is the login mode
Need a password instead of certs? Or an additional password to the certs?
auth-user-pass-verify /etc/openvpn/auth.sh via-file
This just has to return "0" or "1" for good and bad auth:
#!/bin/sh #Simplest way ALLOWED_USER1="wlanboy" ALLOWED_PASS1="supersecure" if [ "$username" == "$ALLOWED_USER1" ] && [ "$password" == "$ALLOWED_PASS1" ] then exit 0 fi exit 1
Want no client certs? Add this to the server.conf
device="venet0" #// OpenVZ yourexternalid="220.127.116.11" #// Change this value! yourvpnsubnet="10.10.10.0/24" #// Change this value! yourvpnport="1149" #//Change this value! # allow OPENVPN and enable ip forwarding iptables -A INPUT -i tun0 -j ACCEPT iptables -A FORWARD -i tun0 -j ACCEPT iptables -A FORWARD -o $device -i tun0 -j ACCEPT iptables -A FORWARD -o tun0 -i $device -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A INPUT -i $device -p udp --dport $yourvpnport -m state --state NEW -j ACCEPT iptables -t nat -A POSTROUTING -s $yourvpnsubnet -j SNAT --to $yourexternalid
Depens on your choice if you are using a startup script or persist these iptables rules.
. ./vars ./revoke-full clientname
So this is everything I am duing to setup a OpenVPN server.
Looking forward to your input and your addons.