In my previous post, I mentioned that I somehow ended up with a corrupted filesystem on the WireGuard server I had set up earlier this year. That iteration of my VPN server was built on Linux as I expected I would get better performance using the kernel-based WireGuard implementation. It had taken me a while to set it up right, and I didn’t get the impression that the performance was so much better anyway. Keep in mind that I mostly use my VPN server from hotel WiFi and we all know how “good” that tends to be performance wise.

While I’ve done a fair bit of Linux admin work, I didn’t fancy re-doing the whole setup again. I also hadn’t scripted it up using Ansible or similar. I tend to prefer BSD anyway, and most of my personal servers run some flavour of BSD Unix. As I didn’t want to spend too much time securing this server, I used OpenBSD as it is a little more secure out of the box compared to FreeBSD. I also hadn’t experimented with OpenBSD for a while so I was curious to see the more recent improvements.

OpenBSD WireGuard Server setup at Vultr

I re-used the VPS I already had set up for the old Linux WireGuard VPN server at Vultr. Heck, it was corrupted already so formatting it was the only choice. In the interest of getting the VPN up and running quickly again, I used Vultr’s preconfigured OpenBSD image. With hindsight I probably wouldn’t do that again. More about this later. I followed a combination of instructions, mainly from the Cryptsus blog post on setting up WireGuard on an OpenBSD 6.6 server, but also referencing Jasper.La’s blog and Ankur Kothari’s blog. Setting up WireGuard on OpenBSD took me a lot less time than configuring the Linux version. I think it took me an hour or two to get the basic VPN tunnel up and working, including configuring the macOS client.

Overall I found this approach simpler than setting up WireGuard on Linux. I think there are two reasons for this – using the precompiled binaries for the user mode processes means you don’t have to futz around with kernel modules, third party repos and all that fun stuff, plus I personally find FreeBSD and to a certain extent OpenBSD easier to set up. This is obviously a personal preference. Plus, no systemd :).

Notes on the default Vultr OpenBSD Image

The Cryptsus instruction include setting up OpenBSD using full disk encryption. This is more secure than using Vultr’s default, preconfigured VPS image as that one doesn’t support full disk encryption out of the box. Using the preconfigured image makes the installation process easier and quicker, but at the expense of not getting the full official OpenBSD configuration out of the box. With hindsight, I probably what should have used a custom (well, the official) OpenBSD 6.6 image instead of the preconfigured Vultr one, but as mentioned I was in a bit of a rush and it was a case of “good enough and working” trumping “more secure”. When setting up a VPN server, there are basically multiple issues you want to protect yourself against:

  1. Someone remotely logging into your VPN server and getting hold of the encryption keys, and/or being able to capture traffic on your VPN server. That’s obviously the worst-case scenario from a security and privacy perspective, and the main one that I wanted to protect myself against. For that, I rely on OpenBSD’s security with strong passwords and key-based SSH authentication to log into the machine.
  2. Someone getting hold of the disk image – that’s what the full disk encryption part protects against. Something I will want to add to the server sooner or later – it does require a reinstall first, though. The risk of this is considerably lower than someone breaking into the VPN server itself and requires either an infrastructure fluke or an infrastructure compromise.
  3. Someone getting a level of access to the VPS host such that they can observe the running VPS and dump out its memory. Again, that’s possible but it requires a lot of work to get there. I like to think that there are a lot juicier targets than myself out there that would warrant this level of effort. So for right now, I’m discounting this threat model.

I’ve got the first point covered right now, will probably address the second one at some point and do my best to ignore the third one for now.

What’s still left to be done

The basic setup for my OpenBSD WireGuard server is up and running, and I’ve successfully used it while traveling. It’s definitely fast enough even on one of Vultr’s $5 instances. Most of the time, when I use the VPN I don’t need lots of bandwidth, but even when “testing” by watching YouTube videos, the performance was more than good enough.

I’m currently using the AdGuard DNS servers that were mentioned in the Cryptsus blog post I linked to above, but I really want to move to an Unbound DNS server on the VPN host itself that a) validates domains were possible and b) uses something like the Pi-hole blocklists to block ads and trackers. The latter is somewhat optional as I don’t really use the VPN for normal browsing, but it’s a definite nice to have.

One thought on “Building an OpenBSD Wireguard server”

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