PHP DynDNS

Introduction

PHP DynDNS is a very simple DynDNS service. It allows you to update your DNS server via a simple HTTP request.

Authorization is done using HTTP Basic Auth or using the username and password URL variables.

The full URL looks like https://dyndns.example.com/?hostname=myhost.example.com (HTTP Basic Auth) or https://dyndns.example.com/?hostname=myhost.example.com&username=myuser&password=mypassword (URL variable auth).

You may also specify the IPv4 and IPv6 address using GET variables (myip=your.ipv4.address.here and myipv6=your:ipv6:address:here).

Examples:

• IPv4 only: https://dyndns.example.com/?hostname=myhost.example.com&myip=79.206.99.18
• IPv6 only: https://dyndns.example.com/?hostname=myhost.example.com&myipv6=2003:66:ef5d:9300:5899:991b:8542:b19f
• IPv4 + IPv6: https://dyndns.example.com/?hostname=myhost.example.com&myip=79.206.99.18&myipv6=2003:66:ef5d:9300:5899:991b:8542:b19f

Requirements

• A domain
• A web server running PHP 7.2 or newer
• A DNS server (e.g. bind)

Or use the ready to run Docker image (see section Installation using Docker).

Installation

There are two methods for getting the latest release:

• (recommended) Download the latest release and extract it to your web directory from where you want to serve the files (e.g. /var/www/dyndns)
• Clone this repository to your web directory from where you want to serve the files (e.g. /var/www/dyndns)

Directly cloning the repository requires you to download the required dependencies using Composer: composer install

Once downloaded, continue with the following steps:

• Copy config.sample.json to config.json
• Edit config.json to fit your needs (see Configuration section bellow for details)
• Configure your DNS server to allow update requests from the webserver (e.g. allow-update { localhost; } in bind)
• Configure your router to automatically request the URL of your DynDNS service after each reconnect (or create a cronjob with curl/wget).

Installation using Docker

PHPDynDNS is also provided as a Docker image. Just pull it from Docker Hub.

Mount your config.json to /app/config.json

Example command to start the container:

docker run -d --name phpdyndns -p 80:80 -v /path/to/config.json:/app/config.json:ro programie/phpdyndns

Important

Make sure the config.json is not readable via HTTP! On Apache this is already done using the .htaccess file.

Configuration

The configuration is done using JSON stored in the config.json file which looks like the following:

{
    "server": "localhost",
    "ttl": 60,
    "users": {
        "myuser": {
            "password_hash": "$5$1IekWfmq$yVTjQcWsX/qK.TIws0NWAj0mmlyDFsSMw6nSFYHcyH8",
            "hosts": {
                "myhost.example.com": {
                    "zone": "example.com"
                },
                "anotherhost.example.com": {
                    "zone": "anotherhost.example.com"
                }
            },
            "post_process": "nohup sudo /opt/some-script.sh %hostname% %ipv4address%"
        }
    }
}

Properties

• server: The DNS server to connect to (default: localhost)
• ttl: The TTL (time to live) for all DNS entries managed by PHPDynDNS (default: 60)
• users: A map listing all users (the key of each entry is the username)
  • password_hash: The hashed password of the user (e.g. created with mkpasswd -m sha-256)
  • hosts: A map listing all hosts this user is able to update (the key of each entry is the hostname to update)
    • zone: The zone which contains this hostname
  • post_process: A command which should be executed after successfully updating the DNS entry (can contain placeholders, see note below)

Placeholders for post_process option

There are a few placeholders which can be used in the post_process option to be replaced on execution.

• %username%: The username
• %hostname%: The hostname
• %ipv4address%: The new IPv4 address (if available)
• %ipv6address%: The new IPv6 address (if available)

Configure your router

Fritz!Box

• DynDNS Provider: Custom
• Update URL: https://your.domain/path/to/phpdyndns?username=<username>&password=<pass>&hostname=<domain>&myip=<ipaddr>
• Domain: your.configured.host.of.your.domain
• Username: your configured username
• Password: your configured password

Cronjob (crontab)

Use this variant if your router does not support sending updates to (custom) DynDNS services. Every request will cause an update to your DNS zone!

* * * * * curl https://your.domain/path/to/phpdyndns?username=your-username&password=your-password&hostname=your.domain.tld

This will update your domain your.domain.tld every minute.

Replace your-username, your-password and your.domain.tld with your configured username, password and domain.

Post Processing

PHP DynDNS can trigger user defined commands after the DynDNS hostname has been updated successfully.

A command might be /opt/reload-iptables.sh which automatically reloads iptables using the new IP-Address of the DynDNS hostname.

The post-processing command can be individually configured for each user in the config.json.

Example: Dynamic firewall using iptables

PHP DynDNS can execute commands after the hostname has been updated successfully. And such a command might reload your iptables rules from a file which also forces iptables to re-lookup your dynamic hostname.

The post-processing script might look like the following:

#! /bin/sh
/sbin/iptables-restore < /path/to/your/iptables.rules

The iptables.rules might look like the following:

*filter

# Set defaults
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]

# Allow already established connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

# Allow local connections
-A INPUT -i lo -j ACCEPT
-A OUTPUT -o lo -j ACCEPT
-A FORWARD -i lo -o lo -j ACCEPT

# Allow HTTP
-A INPUT -p tcp --dport 80 -j ACCEPT

# DynDNS
-A INPUT -p tcp --dport 22 -s yourhost.example.com -j ACCEPT

COMMIT

Note: You have to call the script with root permissions (e.g. sudo)! Simply allow the user running the webserver (e.g. www-data) to execute the script as root (e.g. add www-data ALL=(ALL) NOPASSWD:/opt/scripts/update_dyndns_iptables.sh to your /etc/sudoers file).