ACME DNS Client

ACME (Let's Encrypt) client for issuing SSL/TLS certificate through DNS validation.

Motivation

To order a wildcard SSL/TLS certificate (i.e. a certificate for *.example.com) from an ACME provider like Let's Encrypt, you are required to perform DNS validation to prove ownership of the domain.

This requires you to serve a TXT record at _acme-challenge.example.com during validation containing a token provided to you by the ACME provider. However, automating this can be challenging as many domain name registrars do not provide a way to update records programmatically.

Fortunately, with a particular set of resource records that you pre-configure with your domain registrar, you can defer all future DNS queries for _acme-challenge.example.com to your server of choice. This tool will let you take advantage of this by running a temporary barebones DNS server that only responds to validation queries from the ACME provider.

Installation

Download the binary from GitHub by running wget https://github.com/ShazzAmin/acme-dns-client/releases/download/v0.2.0/acme-dns-client.

Alternatively, you can build from source by cloning this repository and running cargo build --release.

Use

Ensure your DNS records are set-up as such with your domain name registrar:

_acme-challenge.example.com.     CNAME     _acme-challenge.acme-dns-server.example.com.
acme-dns-server.example.com.     NS        yourserver.example.com.
yourserver.example.com           A         <IP address of the server you will run this tool on>

Now simply run the tool:

$ sudo ./acme-dns-client --domain "*.example.com" --email "hello@example.com" --output "/etc/acme-certs/"
Ordering certificate for *.example.com using email hello@example.com from Let's Encrypt...
DNS validation required; starting DNS server...
DNS validation complete.
Order successful; saved certificate and private keys in /etc/acme-certs/
Certificate will expire in 89 days.

If everything goes well, there should be 1 .crt file (your public certificate) and 2 .key files (one is the private key for your certificate and the other is the private key for your ACME account) in /etc/acme-certs/.

You can set this up as a cron job to renew your certificate periodically.

Testing

Use the --staging option if you are testing. This will use the staging Let's Encrypt provider.

License

MIT