Let's Encrypt + DNS = acme-dns-01-test

| Built by Root for Hub

An ACME dns-01 test harness for Let's Encrypt integrations.

| ACME HTTP-01 | ACME DNS-01 | Greenlock Express | Greenlock.js | ACME.js

This was specificially designed for ACME.js and Greenlock.js, but will be generically useful to any JavaScript DNS plugin for Let's Encrypt.

npm install --save-dev acme-dns-01-test@3.x

How Let's Encrypt works with DNS

In order to validate wildcard, localhost, and private domains through Let's Encrypt, you must use set some special TXT records in your domain's DNS.

This is called the ACME DNS-01 Challenge

For example:

dig TXT example.com

;; QUESTION SECTION:
;_acme-challenge.example.com.		IN	TXT

;; ANSWER SECTION:
_acme-challenge.example.com.	300	IN	TXT	"xxxxxxx"
_acme-challenge.example.com.	300	IN	TXT	"xxxxxxx"

ACME DNS-01 Challenge Process

The ACME DNS-01 Challenge process works like this:

1. The ACME client order's an SSL Certificate from Let's Encrypt
2. Let's Encrypt asks for validation of the domains on the certificate
3. The ACME client asks to use DNS record verification
4. Let's Encrypt gives a DNS authorization token
5. The ACME client manipulates the token and sets TXT record with the result
6. Let's Encrypt checks the TXT record from DNS clients in diverse locations
7. The ACME client gets a certificate if the validate passes

Using a Let's Encrypt DNS plugin

Each plugin will define some options, such as an api key, or username and password that are specific to that plugin.

Other than that, they're all used the same.

ACME.js + Let's Encrypt DNS-01

This is how an ACME challenge module is with ACME.js:

acme.certificates.create({
	accountKey,
	csr,
	domains,
	challenges: {
		'dns-01': require('acme-dns-01-MODULE_NAME').create({
			fooUser: 'A_PLUGIN_SPECIFIC_OPTION',
			barToken: 'A_PLUGIN_SPECIFIC_OPTION'
		})
	}
});

Greenlock + Let's Encrypt DNS-01

This is how modules are used with Greenlock / Greenlock Express

Global default:

greenlock.manager.defaults({
	challenges: {
		'dns-01': {
			module: 'acme-dns-01-_MODULE_NAME',
			fooUser: 'A_PLUGIN_SPECIFIC_OPTION',
			barToken: 'A_PLUGIN_SPECIFIC_OPTION'
		}
	}
});

Per-Site config:

greenlock.add({
	subject: 'example.com',
	altnames: ['example.com', '*.example.com', 'foo.bar.example.com'],
	challenges: {
		'dns-01': {
			module: 'acme-dns-01-YOUR_MODULE_NAME',
			fooUser: 'A_PLUGIN_SPECIFIC_OPTION',
			barToken: 'A_PLUGIN_SPECIFIC_OPTION'
		}
	}
});

The Easy Way to Build a Plugin

This repo includes unit test suite which makes it very easy to create a plugin.

You can start with a template file that will fail all of the tests, and just build until you pass all of the tests.

After that, you can test the Greenlock CLI to see if you actually get a valid SSL certificate.

Overview

There are only a few methods to implement - just basic CRUD operations.

For most serivices these are very simple to implement (see the reference implementations down below).

Some enterprise-y services are more difficult as they may have special rules about zones (Google Cloud) or intricate authentication schemes (AWS).

init({ request })

zones({ dnsHosts })

set({ challenge: { dnsZone, dnsPrefix, dnsHost, keyAuthorizationDigest } })

get({ challenge: { dnsZone, dnsPrefix, dnsHost, keyAuthorizationDigest } })

remove({ challenge: { dnsZone, dnsPrefix, dnsHost, keyAuthorizationDigest } })

Plugin Outline

This is an even better starter template below, but this outline shows the bare bones of a plugin.

'use strict';

var MyModule = module.exports;

MyModule.create = function (options) {

    var m = {};

    m.init = async function ({ request }) {
        // (optional) initialize your module
    }

    m.zones = async function ({ dnsHosts }) {
        // return a list of "Zones" or "Apex Domains" (i.e. example.com, NOT foo.example.com)
    }

    m.set = async function ({ challenge: { dnsZone, dnsPrefix, dnsHost, keyAuthorizationDigest } }) {
        // set a TXT record for dnsHost with keyAuthorizationDigest as the value
    }

    m.get = async function ({ challenge: { dnsZone, dnsPrefix, dnsHost, keyAuthorizationDigest } }) {
        // check that the EXACT a TXT record that was set, exists, and return it
    }

    m.remove = async function ({ challenge: { dnsZone, dnsPrefix, dnsHost, keyAuthorizationDigest } }) {
        // remove the exact TXT record that was set
    }

    return m;
}

Using the Test Suite

Test setup:

var tester = require('acme-dns-01-test');
var YOUR_PLUGIN = require('./YOUR-CHALLENGE-STRATEGY');

var challenger = YOUR_PLUGIN.create({
	YOUR_TOKEN_OPTION: 'SOME_API_KEY'
});

Run the tests:

var zone = 'example.com';

tester.testZone('dns-01', zone, challenger).then(function() {
	console.info('PASS');
});

Note: Special DNS services, like DuckDNS, only give you a single sub-domain, not a full "zone". You can test them too:

Some DNS services, such as DuckDNS, only give you a single sub-domain, not not multiple records in a zone. Testing them is slightly different:

var record = 'foo.example.com';

tester.testRecord('dns-01', record, challenger).then(function() {
	console.info('PASS');
});

Reference Implementations

• Compatibility
  • Let's Encrypt v2.1 / ACME draft 18
  • Node v6+
  • Chrome, Firefox, Safari, Edge, etc
• Quality
  • Written in VanillaJS
  • No compliers or build scripts
  • Simple, minimal code, in a single file
  • Zero dependencies

These libraries are useful as a model for any plugins that you create.

• dns-01
  • cli
  • digitalocean
  • vultr
  • gandi
  • duckdns
• http-01
  • cli
  • fs

You can find other implementations by searching npm for acme-http-01- and acme-dns-01-.

If you are building a plugin, please let us know. We may like to co-author and help maintain and promote your module.

Note: In some cases (such as non-HTTP, or very complex APIs) you will not be able to maintain browser compatibility. Other than than, if you keep your code simple, it will also work in browser implementations of ACME.js.

Example

See example.js (it works).

Starter Template

Here's what you could start with.

var tester = require('acme-dns-01-test');

// The dry-run tests can pass on, literally, 'example.com'
// but the integration tests require that you have control over the domain
var zone = 'example.com';
var deps = {};

tester
	.testZone('dns-01', zone, {
		// Gives you the promisified `request` object for HTTP APIs
		init: function(deps) {
			request = deps.request;
			return null;
		},

		// Should return an array of zone domain name strings
		// (APIs that don't implement zones, such as DuckDNS, should return an empty array)
		zones: function(opts) {
			console.log('dnsHosts:', opts.dnsHosts);
			throw new Error('_zone not implemented');
		},

		// Should set a TXT record for dnsHost with dnsAuthorization and ttl || 300
		set: function(opts) {
			console.log('set opts:', opts);
			throw new Error('set not implemented');
		},

		// Should remove the *one* TXT record for dnsHost with dnsAuthorization
		// Should NOT remove otherrecords for dnsHost (wildcard shares dnsHost with
		// non-wildcard)
		remove: function(opts) {
			console.log('remove opts:', opts);
			throw new Error('remove not implemented');
		},

		// Should get the record via the DNS server's API
		// (Note: gets different options than set or remove)
		get: function(opts) {
			console.log('get opts:', opts);
			throw new Error('get not implemented');
		}
	})
	.then(function() {
		console.info('PASS');
	});

Full Detailed Example

Here's a quick pseudo stub-out of what a test-passing plugin object might look like:

var deps = {};

tester
	.testZone('dns-01', 'example.com', {
		init: function({ request }) {
			// { request: { get, post, put, delete } }

			deps.request = request;
			return null;
		},

		zones: function({ dnsHosts }) {
			// { dnsHosts: [
			//     '_acme-challenge.foo.example.com',
			//     '_acme-challenge.bar.example.com'
			//  ] }

			return YourApi(
				'GET',
				// Most Domain Zone apis don't have a search or filter option,
				// but `opts` includes list of dnsHosts is provided just in case.
				'https://exampledns.com/api/dns/zones?search=' + opts.dnsHosts.join(',')
			).then(function(result) {
				return result.zones.map(function(zone) {
					return zone.name;
				});
			});
		},

		set: function(opts) {
			var ch = opts.challenge;
			// { type: 'dns-01'
			// , identifier: { type: 'dns', value: 'foo.example.com' }
			// , wildcard: false
			// , dnsHost: '_acme-challenge.foo.example.com'
			// , dnsPrefix: '_acme-challenge.foo'
			// , dnsZone: 'example.com'
			// , dnsAuthorization: 'zzzz' }

			return YourApi(
				'POST',
				'https://exampledns.com/api/dns/txt/' + ch.dnsZone + '/' + ch.dnsPrefix,
				{ value: ch.dnsAuthorization }
			);
		},

		get: function(query) {
			var ch = query.challenge;
			// { type: 'dns-01'
			// , identifier: { type: 'dns', value: 'foo.example.com' }
			// , altname: '...'
			// , dnsHost: '...'
			// , wildcard: false }
			// Note: query.identifier.value is different for http-01 than for dns-01
			//       because of how a DNS query is different from an HTTP request

			return YourApi(
				'GET',
				'https://exampledns.com/api/dns/txt/' + ch.dnsZone + '/' + ch.dnsPrefix
			).then(function(secret) {
				return { dnsAuthorization: secret };
			});
		},

		remove: function(opts) {
			var ch = opts.challenge;
			// same options as in `set()` (which are not the same as `get()`

			return YourApi(
				'DELETE',
				'https://exampledns.com/api/dns/txt/' + ch.dnsZone + '/' + ch.dnsPrefix
			);
		}
	})
	.then(function() {
		console.info('PASS');
	});

Where YourApi might look something like this:

var YourApi = function createApi(config) {
	return function(method, url, body) {
		return request({
			method: method,
			url: url,
			json: body || true,
			headers: {
				Authorization: 'Bearer ' + config.apiToken
			}
		}).then(function(resp) {
			return resp.body;
		});
	};
};

Note: request is actually @root/request, but the API is the same as the standard request.

Avoid using 3rd party API libraries where you can - they tend to bloat your dependencies and add security risk. Instead, just use the API documentation and cURL examples.

Two notes:

Note 1:

The API.get(), API.set(), and API.remove() is where you do your magic up to upload a file to the correct location on an http serever, set DNS records, or add the appropriate data to the database that handles such things.

Note 2:

• When altname is foo.example.com the dnsHost will be _acme-challenge.foo.example.com
• When altname is *.foo.example.com the dnsHost will still be _acme-challenge.foo.example.com!!
• When altname is bar.foo.example.com the dnsHost will be _acme-challenge.bar.foo.example.com

We Build Let's Encrypt Plugins for You

Want to get the experts involved? Contact Root

We can take it on ourselves, work within your team, or guide an outsourced team.

Turnaround is typically a few days for simple modules with publicly available APIs.