update_ddns_lambda

import json

import boto3


# To use, connect to an API gateway, grant route53 permissions and:
#
# curl "https://your_api_gateway_host/prod/updateDdns?host_name=host_name_to_update&secret=matching_secret"
#
# or
#
# curl "https://your_api_gateway_host/prod/updateDdns?host_name=host_name_to_update&secret=matching_secret&ip=override_autodetected_ip"


HOST_NAME_SECRETS = {
    'ddns-host.example.com': '3278461871',
}

HOSTED_ZONE_ID = '123456'  # id of your hosted zone


def lambda_handler(event, context):
    ip = event['queryStringParameters'].get('ip', 
                                            event['headers']['X-Forwarded-For'].split(',')[0])
    host_name = event['queryStringParameters']['host_name']
    secret = event['queryStringParameters']['secret']

    if HOST_NAME_SECRETS[host_name] != secret:
        raise Exception('Bad secret')

    route53 = boto3.client('route53')
    route53.change_resource_record_sets(
        HostedZoneId=HOSTED_ZONE_ID,
        ChangeBatch={
            'Comment': 'lambda ddns update',
            'Changes': [
                {
                    'Action': 'UPSERT',
                    'ResourceRecordSet': {
                        'Name': host_name,
                        'Type': 'A',
                        'TTL': 60,
                        'ResourceRecords': [
                            {
                                'Value': ip
                            },
                        ],
                    }
                }
            ]
        }
    )

    return {
        'statusCode': 200,
        'headers': { 'Content-Type': 'application/json' },
        'body': json.dumps({
            'ip': ip,
            'host_name': host_name,
        })
    }