Restricting Lambda function by IP address

handler.py

import json
import os

def ping(event, context):    
    ip1 = event['headers']['X-Forwarded-For'].split(',')[0]
    ip2 = event['requestContext']['identity']['sourceIp']
    print('two different referring IP address parsing techniques ip1: %s and ip2: %s') % (ip1, ip2)

    referringIP = event['requestContext']['identity']['sourceIp']
    #TODO: use a comma-delimited string to store multiple IP address values in the environment variable
    if (os.environ['IP_WHITELIST'] != referringIP):
        return {
            'statusCode': 401,
            'body': 'This IP address is not allowed %s' % referringIP
        }

    return {
        'statusCode': 200,
        'body': 'This IP address is allowed %s' % referringIP
    }

serverless.yml

service: ip-restrict

provider:
  name: aws
  runtime: python2.7
  stage: dev
  region: us-west-2
  profile: ko-playground-admin
  environment:
    IP_WHITELIST: "44.99.53.83"

functions:
  ping:
    handler: handler.ping
    events:
      - http:
          path: ping
          method: GET