Domain registrar agnostic authenticator plugin for certbot

An authenticator plugin for certbot to support Let's Encrypt DNS challenges (dns-01) for domains managed by any registrar.

• There is no other authenticator plugin for your domain registrar.
• Some domain registrars do not support fine-grained API permissions. Storing domain registrar credentials in a file on a web server might pose a security risk to all your domains.
• Migrating from one domain registrar to another does not require a new authenticator plugin.

1. Optionally install the netfilter_queue library and iptables. On Debian-based systems, run:

   apt install libnetfilter-queue-dev iptables build-essential
   

   These dependencies enable support for DNS challenge authentication if UDP port 53 is already occupied.

2. Plugin installation:

   • If you are using certbot from your distribution repository or from the Python Package Index:

     pip install certbot-dns-local[netfilter]
     

   • If you are using certbot-auto, clone the repository, cd into the folder and run:

     /opt/eff.org/certbot/venv/bin/pip install certbot-dns-local[netfilter]
     

   If you do not need the netfilter feature, you can install the plugin through pip install certbot-dns-local without the [netfilter] suffix specifying optional dependencies.

3. Set up a DNS NS record for _acme-challenge.yourdomain.com pointing to the server which certbot is running on.
   For example:

   _acme-challenge.yourdomain.com. 300 IN NS yourdomain.com.
   

   Such a record has to be created for each subdomain which you want to obtain a certificate for.

A new certificate can be requested as follows:

certbot certonly -a dns-local -d yourdomain.com -d '*.yourdomain.com'

Older versions of certbot may require you to use the plugin legacy name as follows:

certbot certonly -a certbot-dns-local:dns-local -d yourdomain.com -d '*.yourdomain.com'

Renewals will automatically be performed using the same authenticator by certbot.

By default, the authenticator will attempt to resolve the challenge domain's nameserver IP addresses and bind sockets to these addresses. This is done to prevent listening on 0.0.0.0 or ::, which may result in collisions with services like systemd-resolved. This behavior can be overridden by specifying one or multiple bind addresses manually using the --dns-local-listen <address> parameter, e.g. in cases where certbot is running behind NAT.

You can also use the Docker container as follows:

docker run -it --name certbot-dns-local -v /etc/letsencrypt:/etc/letsencrypt --rm --net=host ghcr.io/blechschmidt/certbot-dns-local:latest certonly -d yourdomain.com -d '*.yourdomain.com'

Note that with the use of the Docker Container method, you will still need to automate certificate renewal. Therefore, this repository contains an extra folder with systemd units taking over this job.

Behind the curtain, the plugin will open a UDP server on port 53 in order to serve the DNS validations. In case binding to port 53 fails because it is already occupied by another application, it will fall back to packet interception using the netfilter_queue library.