The post will show you how to setup a headless linux server using Ubuntu 16.04 LTS and only allowing outgoing connections using a secure VPN 1 connection with OpenVPN. If the VPN connection fails, no traffic is leaked. I will be using NordVPN as an example VPN provider since it is what I use myself, but any VPN provider with OpenVPN profiles should work.
First we install the OpenVPN client and required dependencies as described at NordVPN guide:
$ sudo apt install openvpn unzip ca-certificates
Next we download and unzip the OpenVPN configuration files:
$ cd /etc/openvpn $ sudo wget https://nordvpn.com/api/files/zip $ sudo unzip zip $ sudo rm zip
Now we can connect to a server. To see a list of all servers available, do a
ls -al from
/etc/openvpn. Choose one of these files, e.g.
$ sudo openvpn at1.nordvpn.com.udp1194.ovpn
And enter your login credentials. You can test that you are in Austria (AT) from another shell using:
$ curl ipinfo.io/country AT
And when disconnecting the OpenVPN from the first shell (just use
CTRL + C) and rerunning the above command you should get your origin country.
Next we make sure we can only use the VPN internet connection. If you are doing this over SSH remember to do a
sudo ufw allow 22 to prevent being locked out.
$ sudo apt install ufw $ sudo ufw default deny incoming $ sudo ufw default deny outgoing $ sudo ufw allow out 1194/udp $ sudo ufw allow out on tun0 $ sudo ufw enable
The above will prevent all incoming and outgoing connections except for
tun0 which is the VPN and port 1194 so we can connect to the VPN. Notice that I do not allow VPN connections on port 443 since I might accidentally connect to websites without VPN.
We also make sure to use NordVPN’s DNS servers as described here.
$ sudo cat > nano /etc/resolvconf/resolv.conf.d/base << EOF $ nameserver 188.8.131.52 $ nameserver 184.108.40.206 $ EOF
We now test the connection without being on the VPN which prevents data-connections and DNS lookups.
$ ping google.com -c 1 ping: unknown host google.com $ curl ipinfo.io/country curl: (6) Could not resolve host: ipinfo.io
And with the VPN we are able to
$ ping google.com -c 1 PING google.com (220.127.116.11) 56(84) bytes of data. 64 bytes from fra16s12-in-f206.1e100.net (18.104.22.168): icmp_seq=1 ttl=57 time=34.3 ms --- google.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 34.301/34.301/34.301/0.000 ms $ curl ipinfo.io/country CH
First we save our credentials in a file. The information is stored as cleartext so be sure to secure it. Replace
Password with your own information.
$ sudo sh -c 'cat > /etc/openvpn/NordVPN_credentials << EOF $ Username $ Password $ EOF'
Next we modify the OpenVPN files to use the credentials from the file.
$ sudo sed -i -- 's/auth-user-pass.*/auth-user-pass \/etc\/openvpn\/NordVPN_credentials/g' /etc/openvpn/*
And finally we create a cronjob to autostart the VPN client on boot, replace
at1.nordvpn.com.udp1194.ovpn with whatever configuration file you want to use.
$ (crontab -u root -l; echo "@reboot sleep 10 && /usr/sbin/openvpn /etc/openvpn/at1.nordvpn.com.udp1194.ovpn" ) | crontab -u root -
Restart the server and you should automatically use the VPN connection.