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#+TITLE: Creating a VPN Gateway with OpenBSD 6.7
#+DATE: 2020-07-11T13:48:25-04:00
#+DRAFT: true
#+DESCRIPTION:
#+TAGS[]: openbsd openvpn
#+KEYWORDS[]: openbsd openvpn
#+SHOWTOC: true
#+SLUG:
#+SUMMARY:
* The Problem
Say you have an account with a VPN provider. Maybe there are a limit
to how many connections you can have with one account, and you want to
put more machines than you have connections on the account. Or maybe
you want to put a large number of machines of the connection,
including maybe FreeBSD Jails, LXC containers, or VMs, and you don't
want to download the VPN profiles, sign in and configure them all
individually.
* The Solution
The solution I came up with to this problem is to setup a VPN gateway
on my network using [[https://www.openbsd.org/faq/pf/][OpenBSD]]. Any device that sets that machine as it's
gateway will automatically get its traffic tunneled through the VPN
connection. It's also setup such that if the VPN connection ever drops
or gets killed for any reason, the traffic will stop and won't be able
to reach the internet. Thanks to this I don't have to worry about the
traffic ever leaking out through my residential gateway should OpenVPN
decide to close the connection. Sort of like a "kill switch", as some
companies market it.
* My Network
In this post the machine will have a single network interface called
=vio0= with a desired static IP of =192.168.0.11=, although the
interface and IP in your case will be differ.
* Hardware
To replicate my setup you'll need a dedicated machine running
OpenBSD. You'll have to choose an appropriate host, taking into
consideration how much traffic you plan to put through it, the speed
of you VPN connection, and the speed of your home internet
connection. Anything from a virtual machine or a low power single
board PC will do in most cases, as home internet connections
generally aren't the fastest. If your internet connection is fast
enough though, you may consider [[https://blog.lambda.cx/posts/installing-openbsd-on-pcengines/][installing OpenBSD]] on a [[https://blog.lambda.cx/posts/pcengines-comparison/][PC Engines
APU2]], as they're affordable, have gigabit Ethernet, and great
OpenBSD driver support. In my case I created a virtual machine on a
server in my house running [[https://www.proxmox.com/en/][Proxmox]]. In my case, the machine only has
1 vCPU and 512 MB RAM, which is more than enough for my needs.
* Documentation
I highly recommend you check out the man pages for the firewall
configuration file format [[https://man.openbsd.org/man5/pf.conf.5][=pf.conf(5)=]], and the pf control command
[[https://man.openbsd.org/man8/pfctl.8][ =pfctl(8)=]] if you plan on setting something like this up. They're all
very well written and explain a lot of what I'm doing in very clear
detail. You should also read the excellent [[https://www.openbsd.org/faq/pf/][PF FAQ]] from the OpenBSD
website, which covers many more PF configuration examples.
* Install OpenBSD
I won't be covering installing OpenBSD here, although it's extremely
simple and straight forward. You can pick up the disk =.iso= image or
USB =.fs= image from the [[https://www.openbsd.org/faq/faq4.html#Download][download]] page on OpenBSD website. If this is
your first time installing OpenBSD, you should check out the
[[https://www.openbsd.org/faq/faq4.html#Download][ installation guide]], which goes over the process in detail.
* Configuring a Static IP
The most important thing is to set a static IP, so it can be set as
the gateway for client machines. We'll set this first.
Setting a static IP in OpenBSD couldn't be simpler. For each
interface on the machine, you can create a file with the name
=/etc/hostname.<if>=, where =<if>= is the name of the
interface. Since we want to set a configure the interface =vio0=,
the file we want is =/etc/hostname.vio0=. If your box was configured
with DHCP, the file might contain =dhcp=. We want to give the
interface the static IP =192.168.0.11=, so we open the file and
replace its contents with the following.
#+BEGIN_SRC
inet 192.168.0.11/24
#+END_SRC
Now we run [[https://man.openbsd.org/man8/netstart.8][=netstart(8)=]] to reconfigure the interface according to the
file we've just edited.
#+BEGIN_SRC shell
dosa sh /etc/netstat vio0
#+END_SRC
Now if you check =ifconfig=, you should see the interface has the
correct IP.
* Configuring OpenVPN
First we have to install [[https://openvpn.net/][OpenVPN]], which is provided by the OpenBSD
package manager. Normally we would install the =openvpn= package,
but due to an [[{{< ref "openvpn-issues-openbsd" >}}][issue with libressl]], we'll be installing the =mbedtls=
version. This problem should hopefully be resolved soon, so we'll
likely be able to use regular =openvpn= in the future.
#+BEGIN_SRC shell
doas pkg_add openvpn--mbedtls
#+END_SRC
Note: The =--mbedtls= is required to get the =mbedtls= flavour of
the =openvpn= package.
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