Duck DNS module for Caddy

This package contains a DNS provider module for Caddy. It can be used to manage DNS records for Duck DNS.

Caddy module name

dns.providers.duckdns

Caddyfile definition

duckdns [<api_token>] {
    api_token <api_token>
    override_domain <duckdns_domain>
}

• api_token may be specified as an argument to the duckdns directive, or in the body.
• override_domain is optional; see Challenge delegation below.

Config examples

To use this module for the ACME DNS challenge, configure the ACME issuer in your Caddy JSON like so:

{
	"module": "acme",
	"challenges": {
		"dns": {
			"provider": {
				"name": "duckdns",
				"api_token": "YOUR_DUCKDNS_API_TOKEN",
				"override_domain": "OPTIONAL_DUCKDNS_DOMAIN"
			}
		}
	}
}

or with the Caddyfile:

tls {
	dns duckdns {env.DUCKDNS_API_TOKEN}
}

You can replace {env.DUCKDNS_API_TOKEN} with the actual auth token if you prefer to put it directly in your config instead of an environment variable.

Authenticating

See the associated README in the libdns package for important information about credentials. Your token can be found at the top of the page when logged in at https://www.duckdns.org.

Challenge delegation

To obtain a certificate using ACME DNS challenges, you'd use this module as described above. But, if you have a different domain (say, my.example.com) CNAME'd to your Duck DNS domain, you have two options:

1. Not use this module: Use a module matching the DNS provider for my.example.com.
2. Delegate the challenge to Duck DNS.

Delegating the challenge is actually quite easy, and may be useful if the DNS provider for my.example.com is difficult to configure or slow:

Since Let’s Encrypt follows the DNS standards when looking up TXT records for DNS-01 validation, you can use CNAME records or NS records to delegate answering the challenge to other DNS zones. This can be used to delegate the _acme-challenge subdomain to a validation-specific server or zone. It can also be used if your DNS provider is slow to update, and you want to delegate to a quicker-updating server.

Let's say you have my.example.com as a CNAME to example.duckdns.org. Following the above instructions, you'd want to add a CNAME from _acme-challenge.my.example.com to example.duckdns.org. Then, in your Caddyfile, instruct this module to override the domain used when communicating with Duck DNS' API:

my.example.com {
	tls {
		dns duckdns <token> {
			override_domain example.duckdns.org
		}
	}
	...
}

If you do not set override_domain, this module will attempt to ask Duck DNS to update my.example.com. Duck DNS will return an error, because it does not know about my.example.com. Setting this value fixes this up and allows Caddy to ask for a certificate matching my.example.com, but by performing DNS challenges on example.duckdns.org instead!