Dart Acme Client

An ACME V2 compatible client written in Dart.

Table of Contents

• Dart Acme Client
  • Table of Contents
  • Preamble
  • Install
    • pubspec.yaml
  • Import
  • Acme Client
    • Client Setup
  • Applying for Certificate Issuance
    • Place Order
    • Fetch Authorization Data
    • Get Challenge For Authorization
    • Self Test
    • Trigger Validation
    • Finalize Order
    • Fetch Certificate
  • Changelog
  • Copyright and license

Preamble

As this package is written in pure Dart, it can be used on all platforms on which dart is currently running. This includes the use of frameworks like Flutter, Angular Dart and many more. This package can also be used for command line tools or rest services compiled with dart2native.

Note: Feel free to contribute by creating pull requests or file an issue for bugs, questions and feature requests.

Install

pubspec.yaml

Update pubspec.yaml and add the following line to your dependencies.

dependencies:
  acme_client: ^1.3.0

Import

Import the package with :

import 'package:acme_client/acme_client.dart';

Acme Client

This is a simple ACME written in Dart based on the RFC 8555. The client should be able to communicate with every ACME server that is based on the mentioned RFC including Let's Encrypt.

Client Setup

Create a new client by calling the constructor and pass the appropriate parameters.

  var client = AcmeClient(
    'https://acme-server.com',
    privateKeyPem,
    publicKeyPem,
    true,
    ['mailto:[email protected]'],
  );

• baseUrl = The base url of the acme server.
• privateKeyPem = The private key in PEM format.
• publicKeyPem = The public key in PEM format.
• acceptTerms = Accept terms and condition while creating / fetching an account.
• contacts = A list of email addresses. Each address should have the format mailto:[email protected].

Note: If you want to create a RSA/ECC key pair with Dart, take a look at the Basic Utils Package. The X509Utils and CryptoUtils, contain everything needed for creating a key pair and formating it to PEM.

After the client is setup, call the init() method, to fetch the directories and account information from the server. If there is no account for the given public key on the server, the client will create a new account.

  await client.init();

Applying for Certificate Issuance

Place Order

Placing an order can be done by creating a new order object and adding the identifiers that should be placed in the certificate. The order methode of the client will then return the order information returned by the acme server.

  var order = Order(
    identifiers: [Identifiers(type: 'dns', value: 'example.com')]
  );
  var newOrder = await client.order(order);

Fetch Authorization Data

For each order, the ACME server return an authorization data for each identifier if requested via the getAuthorization() method..

  var auth = await client.getAuthorization(newOrder!);

Get Challenge For Authorization

For each returned authorization there are multiple challenges. You can use one of these challenges to prove controll over one identifier and fulfill the authorization request.

  for(var a in auth){
     var data = a.getHttpDcvData();
  }

  for(var a in auth){
     var data = a.getDnsDcvData();
  }

Self Test

It is recommended to check in advance if a challenge is passed by using the appropriate client method. Via the maxAttempts parameter you can increase or decrease the amount of time it will try to check for the challenge token. The default is 15.

Note: The DNS self test uses the Google DNS Rest API to fetch the resource records.

  var self = await client.selfDNSTest(data); // DnsDcvData
  if (!self) {
    print('Selftest failed, no DNS record found');
  }

  var self = await client.selfHttpTest(data); // HttpDcvData
  if (!self) {
    print('Selftest failed, no file found or content missmatch');
  }

Trigger Validation

To tell the ACME server to check the challenge, call the validate() method on the client with the desired challenge. This will trigger the validation and check every 4 seconds the status of the authorization to change to "valid". Via the maxAttempts parameter you can increase or decrease the amount of time it will poll the status. The default is 15.

  var data; // HttpDcvData or DnsDcvData
  var authValid = await client.validate(data.challenge);
  if (!authValid) {
    print('Authorization failed, exit');
  }

Finalize Order

If every authorization has the status "valid" finalize the order by sending a CSR to acme server. The CSR will automatically formated according to the RFC rules (base64Url encoded without headers).

var finalOrder = await client.finalizeOrder(newOrder, csr);

Fetch Certificate

A list of certificates can then be fetched via the getCertificate() method by passing the finalized order object.

var certs = await client.getCertificate(finalOrder);

Changelog

For a detailed changelog, see the CHANGELOG.md file

Copyright and license

MIT License

Copyright (c) 2021 Ephenodrom

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.