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HOWTO - Letsencrypt Certificates for pfSense

2021-07-17 by Mohammad H. Al-Shami

I recently helped a friend set up pfSense as a VPN server/firewall for his colocated rack. We wanted SSH and the web configurator to be accessible from a set of static IPs.

When we tried to enable LetsEncrypt, we found out they do not publish the list the IP addresses used for the HTTP provider. It took me a while to figure out how to securely work around that and I will be sharing it here.

In Firewall -> Aliases -> IP, start with adding an alias to all IPs you want to allow to access web configurator or SSH.

In Firewall -> Aliases -> Ports add an alias to ports, 80, 443 and 22

Set up the port forwarding rules. Port 8443 is what the ACME client listens on to do the TLS verification.

From System -> Package Manager, choose “Available Packages” and install the “acme” package.

In Services -> Acme Certificates -> Account keys, Add a new key

In Services -> Acme Certificates -> Account keys, Add a new certificate with the following SAN list and Actions

And you’re done.

This works as follows:

  • Connections from AdminHosts to ports 80, 443, 22 are forwarded to the same port on the LAN interface
  • All other connections to port 443 are forwarded to port 8443 on the WAN interface
  • Port 8443 is only active when the ACME client is running, so the port forwarding is secure

After setting things up I thought that using haproxy might have been a simpler option. But it’s always better to have alternatives.

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Dev gone Ops gone DevOps. Any views expressed on this blog are mine alone and do not necessarily reflect the views of my employer.