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. On Debian-based systems, run:

   apt install libnetfilter-queue-dev
   

   The library enables 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
     

   • 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
     

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

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

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.