Google Cloud Dynamic DNS Client

This is a simple dynamic DNS script for Google Cloud DNS. The script will check for its public IP address, and then based on its configuration it read from the configuration file, check whether Google Cloud DNS has a corresponding DNS entry. If no corresponding entry is found, the script will create one. If a corresponding entry is found, but has an IP address which doesn't match that of what the script found, then the script will update then Google Cloud entry (read delete, then create). Finally, if the scripts configuration file matches that of the Google Cloud DNS entry, then it will sleep for an interval of x, and the process repeats.

This project consists of the following components:

• gcloud-ddns.py: the dynamic dns client script
• ddns-conf.yaml: programs configuration file
• requirements.txt: requirements to be installed

Requirements

This script requires Python 3.6 or greater. f-strings are extensively used. Package requirements are listed in requirements.txt

Usage

Usage: python gcloud-ddns.py [path_to_configuration_file.yaml]

Setup

$ git clone git@github.com:conorcunningham/google-ddns.git
$ cd google-ddns
$ python3 gcloud-ddns.py

The script will run in the foreground. I'm going to play around with it and test it to see if it can run reliably as a service.

Configuration file

The configuration for the script is read from a yaml file. Here are the contents of the example ddns-conf.yaml file

api-key: './ddns-api-key.json'
logfile: './ddns.log'
hosts:
    -   host: 'firewall.example.com.'
        project_id: 'fluffy-penguin-242411'
        managed_zone: 'example'
        domain: 'example.com'
        ttl: 60
        interval: 600

    -   host: 'www.example-two.com.'
        project_id: 'fluffy-penguin-242411'
        managed_zone: 'example-two'
        domain: 'example-two.com'
        ttl: 60
        interval: 600

The script accepts one optional CLI argument which is the path to the configuration file. If none is given, the script will look for ddns-config.yaml in the same directory as the script.

• host: the fully-qualified domain name of the host you want to set. NB* You must include the . after the .com. This is a Google requirement/
• project_id: Your project ID within Google Cloud
• managed_zone: The name of your managed zone in Google Cloud
• domain: Your domain name
• ttl: The number of seconds for the TTL
• interval: How long the script will sleep before running again
• api-key: Path to the API key in JSON format
• log-path: Path to the logfile

Authentication

In order to use the Google Cloud API, you will need an API key for your account. This key will be a json file and must be configured in the configuration file.

The script will set GOOGLE_APPLICATION_CREDENTIALS environmental variable to the path of your API key and Google's modules will use this environmental variable to handle authentication.

os.environ["GOOGLE_APPLICATION_CREDENTIALS"] = api_key

Docker

A Dockerfile is included in the repository so you can launch this as a container inside a Docker instance.

docker build -t google-ddns .

The default docker command expects a config.yaml file inside the /ddns directory

docker run -it --rm -v <path/to/config>:/ddns google-ddns

Keep in mind that the paths inside the config file are relative to the container

api-key: '/ddns/ddns-api-key.json'
logfile: '/ddns/ddns.log'
...

Here's a quick-and-dirty docker-compose file if you use that

version: '3'

services:
  ddns:
    image: google-ddns
    volumes:
    - ./config:/ddns

ipify.org API

This project makes use of the snazzy ipify.org API for fetching the clients public IP address.