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Sam DNS Tools

This is an unofficial software that I developed to solve a few problems I have related to DNS, including DNS-01 challenge for wildcard certificates in letsencrypt/certbot (I'm not affiliated with any of the DNS providers listed here). Also as a dynamic DNS client.

Introduction

certbot command

For letsencrypt and its Certbot's challenge of type DNS-01 to sign Wildcard certificates for domains, a TXT record is required to be added to the DNS records of the domain, this script automates the process of adding and removing the TXT record.

In Certbot, the --manual-auth-hook and --manual-cleanup-hook options are used to specify the script to be executed before and after the challenge. This program is designed to be called in these scripts.

I developed this program because I love for my tools to be reusable, testable and to be written in such a way where errors are impossible to happen. I hate writing random bash scripts to do this with weird curl commands, so I spent a few hours to create the first version of this.

This program also has some extra features for DNS control, such as dyndns. The default subcommand is certbot, but feel free to try the others. It can be used for any other automation tasks that require DNS control.

Dynamic DNS

This program can also be used as a dynamic DNS client. It can be used to update the IP address of a domain name to the current IP address of the machine running this program. This is useful for home servers that don't have a static IP address. This is done using the dyndns subcommand.

Every run of the program with dyndns subcommand will check the current IP address of the machine running this program, and if it's different from the IP address of the domain name, it will update the domain name to the current IP address.

Capabilities/Features

This program is very simple by design. It can do two things:

  • Subcommand test: Test the implementation of a specific DNS provider automatically (for both testing the health of your setup and for adding new DNS providers)
  • Subcommand certbot: Modify DNS records as per certbot requirements through the supported add/remove/list DNS host records using https calls
  • Subcommand dyndns: Update the IP address of a domain name to the current IP address of the machine running this program

With the test functionality, you can have a cron job that will daily call this for you to test that your DNS calls are working correctly, and on failure, send you an email to notify you of the error. When the time comes for your certbot renewal, you can be sure that your DNS provider calls are working correctly.

Available DNS Providers

I started this for myself, where I use Epik.com as domain provider, but you're welcome to add more services and add it to the list.

  • Epik.com

Usage

First step in using this program, is to input your configuration of your domains in the config.yaml file. See the Configuration file section for more details. Once you do, you can test your configuration using the test command (cargo run -- test). See the Test-run section for more details. If the tests pass, you're ready to use this program with certbot.

This program isn't meant to be installed. I don't mind cloning it from github and running it directly.

Certbot usage

In order to use this program with certbot, you can clone the repository, and then add the hook scripts provided as follows, in the directory where you cloned the repository:

certbot ${MoreArgumentsForYourDomain} --manual-auth-hook ./dns_auth_hook.sh --manual-cleanup-hook dns_cleanup_hook.sh

If you'd like to use a proxy, define the environment variable PROXY_FOR_CERTBOT_DNS_HOOK to be the proxy URL. For example:

export PROXY_FOR_CERTBOT_DNS_HOOK=socks5://1.2.3.4:1080
certbot ${MoreArgumentsForYourDomain} --manual-auth-hook ./dns_auth_hook.sh --manual-cleanup-hook dns_cleanup_hook.sh

These scripts are in this repository. They are made to be used as is with the source code. Most likely you won't need to change anything in them. You should have Rust installed so that cargo works.

Dyndns usage

In order to use this program as a dynamic DNS client, you can clone the repository. Let's say for the domain example.com, you want to make internal.example.com point to the current IP address of the machine running this program. You can do the following:

cargo run -- dyndns --account-domain-name=example.com --subdomain=internal

You can also use a proxy, by adding the --proxy argument. The proxy can be helpful for whitelisting purposes. For example:

cargo run -- dyndns --account-domain-name=example.com --subdomain=internal --proxy socks5://127.0.0.1:1080

Notice here that example.com should be configured in the configuration file. See the Configuration file section for more details.

SECURITY NOTE: It is not recommended to run this program as root. This is because cargo downloads dependencies and compiles them. While it's extremely unlikely that any of the dependencies have malicious code, I can't guarantee that for you and I'm paranoid by nature. So, it's better to run this program as a normal user. After all the security trade-offs are up to you.

Configuration file

Start by renaming the config.yaml.example file to config.yaml and edit it to match your setup. Once you're done, run the test as in section Testing your configuration to make sure your configuration is correct.

What problem does the configuration file solve?

Every service provider has its own way of authenticating and authorizing API calls. This program is designed to be extensible, so you can add more providers. The configuration file is used to specify the provider and the required credentials.

The configuration is deserialized (from config.yaml) into a struct that implements the DomainController trait. This trait is used to add/remove/list DNS records.

Testing your configuration

To ensure your configuration is correct, you can run the following command after having filled config.yaml:

cargo run -- test

or with some socks5 proxy (to test your DNS provider from a whitelisted IP):

cargo run -- test --proxy socks5://1.2.3.4:1080

This will test all the domains in the configuration file.

How to contribute

You're welcome to contribute to add your own DNS providers to use this program as your DNS hook.

How to add a new DNS provider? (for developers)

To add new DNS providers, you need to:

  1. Add a module in dns_providers/ directory, with a struct that represents the provider (let's call it the DNS provider struct). All authentication details + domain name variable should be stored in this struct. (See how epik.rs is implemented). This struct should also implement Serialize/Deserialize traits from serde. so that it can be used in the configuration file.
  2. Implement the DomainController trait for the DNS provider struct. (See how epik.rs is implemented). This trait is used to add/remove/list DNS records.
  3. Add the DNS provider struct deserialization to the Config struct in the config module. (See how epik.rs is implemented). All configurations that are listed must be deserialized into Vec, just like it's done for Vec.
  4. The method Config::into_domain_controllers() should be able to add your configuration to the list of domain controllers.
  5. At this point you're good to start adding configurations in the config.yaml file and test your implementation using cargo run -- test (with or without proxy, depending on your DNS provider configuration and IP whitelisting). If the tests pass, that means your implementation and configuration are correct.

License

This program is licensed under the MIT license. See the LICENSE file for more details.