dyndns.py

#!/usr/bin/env python3

import boto3
import requests
from datetime import datetime


"""
Dynamic DNS updater.
Simple boto script that will update a dns record in AWS
into the current public ip.
"""

domain = ''
subdomain = ''
HostedZoneId = ''


def get_public_ip():
    """
    return the current public ip.
    """
    r = requests.get('http://icanhazip.com')
    return r.text.rstrip()


def add_cname_record(hosted_zone_id, client, name, value, action):
    """
    Add/update an A record.
    """
    response = client.change_resource_record_sets(
        HostedZoneId=hosted_zone_id,
        ChangeBatch={
            'Comment':
            'add %s -> %s' % (name, value),
            'Changes': [{
                'Action': action,
                'ResourceRecordSet': {
                    'Name': name,
                    'Type': 'A',
                    'TTL': 300,
                    'ResourceRecords': [{
                        'Value': value
                    }]
                }
            }]
        })


if __name__ == '__main__':
    route53 = boto3.client('route53')
    current_ip = get_public_ip()

    try:
        with open('cur_ip') as f:
            record_ip = f.read()
    except FileNotFoundError:
        record_ip = None

    if record_ip != current_ip:
        add_cname_record(
            HostedZoneId,
            client=route53,
            name=f'{subdomain}.{domain}',
            value=current_ip,
            action='UPSERT')
        with open('cur_ip', 'w') as f:
            f.write(current_ip)