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OpenBSD scripts to convert wg-quick VPN files

Written by Solène, on 27 April 2024.
Tags: #openbsd #vpn #security

Comments on Fediverse/Mastodon

1. Introduction §

If you use commercial VPN, you may have noticed they all provide WireGuard configurations in the wg-quick format, this is not suitable for an easy use in OpenBSD.

As I currently work a lot for a VPN provider, I often have to play with configurations and I really needed a script to ease my work.

I made a shell script that turns a wg-quick configuration into a hostname.if compatible file, for a full integration into OpenBSD. This is practical if you always want to connect to a given VPN server, not for temporary connections.

OpenBSD manual pages: hostname.if

Sourcehut project: wg-quick-to-hostname-if

2. Usage §

It is really easy to use, download the script and mark it executable, then run it with your wg-quick configuration as a parameter, it will output the hostname.if file to the standard output. 

wg-quick-to-hostname-if fr-wg-001.conf | doas tee /etc/hostname.wg0

In the generated file, it uses a trick to dynamically figure the current default route which is required to keep a non-vpn route to the VPN gateway.

3. Short VPN sessions §

When I shared my script on mastodon, Carlos Johnson shared their own script which is pretty cool and complementary to mine.

If you prefer to establish a VPN for a limited session, you may want to take a look at his script.

Carlos Johnson GitHub: file-wg-sh gist

4. Prevent leaks §

If you need your WireGuard VPN to be leakproof (= no network traffic should leave the network interface outside the VPN if it's not toward the VPN gateway), you should absolutely do the following:

  • your WireGuard VPN should be on rdomain 0
  • WireGuard VPN should be established on another rdomain
  • use PF to block traffic on the other rdomain that is not toward the VPN gateway
  • use the VPN provider DNS or a no-log public DNS provider

Older blog post: WireGuard and rdomains

5. Conclusion §

OpenBSD's ability to configure WireGuard VPNs with ifconfig has always been an incredible feature, but it was not always fun to convert from wg-quick files. But now, using a commercial VPN got a lot easier thanks to a few piece of shell.