OpenVPN client in Linux Containers
This article describes how to setup a Linux Container to run OpenVPN in client mode with a "kill switch" for secure/private internet use. Doing so offers a distinct advantage over using full-blown virtualization like VirtualBox or QEMU in that the resource overhead is minimal by comparison and able to run on low powered devices.
Basic setup and understanding of Linux Containers is required. This article assumes that readers have a base LXC setup operational. Newcomers to these are directed to the aforementioned article.
The container's configuration should be modified to include several key lines in order to both run OpenVPN and have internet programs (browsers, email clients, torrent clients, etc.) interact with the host system from within the LXC and from behind the VPN.
For the example, the lxc is named "playtime" and a full configuration is shown:
... ## for openvpn lxc.mount.entry = /dev/net dev/net none bind,create=dir lxc.cgroup2.devices.allow = c 10:200 rwm
Needed packages within the container
- Provide a functional "kill switch" to maintain privacy should the connection to the VPN fail.
- Keep nasty stuff out.
This guide useswhich is very easy to configure, but other examples can certainly be used.
Configuration of OpenVPN is beyond the scope of this article. Readers are encouraged to read the OpenVPN article to properly setup the software for a given VPN provider. Note that many private VPN providers include links to directly download a properly configured openvpn.opvn profile unique to their particular service. For the purposes of this guide,
/etc/openvpn/client/myprofile.conf will refer to that config.
Avoiding DNS leaks
Users are highly encouraged to setup openvpn with to manage
/etc/resolv.conf via the instructions in OpenVPN#DNS. Failure to do so may lead to DNS leaks if the host's DNS server is specified in said file.
Configuration of ufw is described in OpenVPN#Firewall configuration. Once modified as described, additional setup is simply to define the protocols to run (ssh, torrent, etc.) and also define the IP address or address range of the VPN provider. Again, these are available from the private providers.
First setup the default deny policy and then allow whatever services are to pass though:
ufw default deny outgoing ufw default deny incoming ufw allow ssh ufw allow 1194 ufw allow out 1194 ufw allow out on tun0 from any to any ufw allow in on tun0 from any to any
Now add the VPN server IP addresses or ranges. Note two entries for each IP address is required. In the example below, only a single fictitious IP address is shown for illustrative purposes.
ufw allow in from 220.127.116.11 to any ufw allow out from 18.104.22.168 to any
Finally, add the internal LAN IP range to allow access regardless of VPN connectivity:
ufw allow from 192.168.0.0/24
Start ufw and enable
ufw.service to start at boot.
# ufw enable
Additional protection can be had via using pgl within the container. See: PeerGuardian Linux#Running pgl from within a container.
Test the service
From within the running container, (connected via ssh or via
lxc-attach -n playtime) test the setup by exporting a browser to the host's machine X server:
$ DISPLAY=:0 firefox
The result should be a firefox window in the host's X server with the title, "Mozilla Firefox (playtime)." A number of websites can be used to verify IP address and status of DNS entries. Once such site is ipleak dot net.
At this point, the IP and DNS entries corresponding to
/etc/openvpn/client/myprofile.conf should be displayed.