In part 2, I reconfigured my WireGuard VPN to use an Unbound DNS server on the VPN server rather than rely on a third party server I had used for the original quick and dirty configuration. It was important for me to set up a validating DNS server, which I did in that part.

In this part, I’m extending the existing configuration to include some basic block lists for known ad and tracking servers. As I’m mainly trying to use the VPN while on the road, I want to ensure that anything I end up doing using the VPN is as secure as I can make it with reasonable effort. That makes tracking and preventing malicious ads the next step. That said, I’m not planning to go for a full Pi-Hole like setup. Initially, I am trying to do is integrate one known good blocklists into the Unbound configuration and automate the process. I can get fancy with a more Pi-Hole like setup later if I want to.

Picking a DNS filter list and using it from Unbound

I started by using a single DNS block list from StevenBlack’s github repo. deadc0de.re’s blog has a good how-to post including the necessary awk incantations for converting the file into the format Unbound needs. I used that blog post as my as my starting point.

The process overall is relatively simple. First, pick the flavour of blocklist you want. Download the hosts file for the blocklist. I used wget to download it as it’s already installed on my OpenBSD system, but curl would also work. My assumption is that you’re running these commands in /var/unbound/etc, so all the absolute paths refer to that location.

wget -O /tmp/blocklist-hosts https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts

This list is in the traditional host file format, so we need to convert it into the format that Unbound needs. Fortunately, deadc0de.re’s blog post contains the necessary code to accomplish that transformation:

cat /tmp/blocklist-hosts | grep '^0\.0\.0\.0' | awk '{print "local-zone: \""$2"\" redirect\nlocal-data: \""$2" A 0.0.0.0\""}' > adblocker.conf

We also need to update our unbound.conf file to include the freshly generated host blocklist. To do that, we have to add an include statement to the server section of the configuration file. The change looks like this:

    server:
      ...
      include: /var/unbound/etc/block-ads.conf

I also had to set up unbound-control to ensure that I didn’t have to restart the server every time I updated the block list. Thus, I had to make a slight detour that involved running unbound-control-setup to generate the necessary certificates. I also needed to add the following statement to my unbound.conf:

remote-control:
  control-enable: yes

Note that remote-control is its own section and is not part of the server: section. The default setup only accepts remote control connections on the loopback interface. This is perfect for my setup, so I didn’t need to make any other changes.
After restarting unbound to pick up the configuration changes I was able to test the VPN with the new DNS blocking and it proved to be mostly effective on the websites I visited.

Automating the process

Of course I’m a software engineer by background, so clearly I wanted to automate the process. Fortunately this is about as complicated as pasting the commands I listed above into a shell script and periodically run it. My script looks like this:

#!/bin/sh

cd /var/unbound/etc
wget -O /tmp/black-hosts https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts
cat /tmp/black-hosts | grep '^0\.0\.0\.0' | awk '{print "local-zone: \""$2"\" redirect\nlocal-data: \""$2" A 0.0.0.0\""}' > block-ads.conf
rm /tmp/black-hosts
unbound-control reload

I’m running this script via cron once a week, as that seems to roughly correspond to the update frequency of the list. I may change that in the future, especially if I end up combining the multiple block lists instead. In the meantime I don’t think it’s necessary to run the cron script more often.

What’s next?

Right now it looks like WireGuard VPN server is working as intended and does what I need it to. TuM’Fatig has a great blog post on expanding the approach I’m using to include all of the public block lists that Pi-Hole is using, so I’m probably going to look into that sooner or later. Other than that and keeping the machine up to date, the next project will be to create orchestration scripts to recreate the server from scratch. I found setting up WireGuard on OpenBSD much easier than doing it on a Linux host. Nevertheless having a Terraform or Ansible script that allowed me to quickly stand one up from scratch if the current instance was damage would likely be a good thing.

Would I go the OpenBSD route again?

I had mentioned at the start of this series that I hadn’t had done much with OpenBSD for years. Was it worth choosing OpenBSD over FreeBSD, which I use on a very regular basis? Maybe, maybe not. OpenBSD required less additional fiddling to secure it out of the box. Some of the time saved was taken up by reacquainting myself with the system, so I’d call that a wash. I suspect that setting up the actual WireGuard VPN instance would take the same amount of time on FreeBSD as I’d run the same commands, so no clear advantage there. I do like the newer version of pf that comes with OpenBSD - FreeBSD’s is a few versions behind and is missing some features, and I doubt it’ll ever catch up.

Put that down as a “maybe”.

How well does WireGuard work for me?

So far it is proving performant enough to run on one of Vultr’s $5 instances that aren’t exactly swimming in computing power. Of course this is only a personal VPN and I’m not running a whole company’s worth of traffic across it. That would very likely require more oomph (technical term) on the server, but overall WireGuard VPN appears to be both very lightweight and more importantly, easy to configure both at the server and client end.

Throughput is good enough to use it to watch YouTube videos in good quality on crappy hotel Wifi without visibly dropping frames. That’s good enough for me as a performance metric because it shows that the VPN server is not the bottleneck. The real use cases for the VPN really are for accessing more sensitive information like financial information, and that is usually all interactive anyway.