Twilio webhook validation for POST events using an AWS lambda proxy integration

twilioLambdaProxyValidation.py

"""Twilio webhook validation for POST events using an AWS lambda proxy integration.
This will return the parsed body or throw an exception if validation fails. It assumes
you are using an aws Lambda functions with an API Gateway proxy integration. 
Example:
    $ eventParser = TwilioEventParser(twilio_auth_token)
    $ try:
    $     parsedBody = eventParser.parse(event, validate=True)
    $ except:
    $     pass
    
"""
from urllib.parse import parse_qs
from collections import OrderedDict
from twilio.request_validator import RequestValidator

def parseTwilioEventParams(event:dict) -> OrderedDict:
    if 'body' in event: #if post
        try:
            params = OrderedDict()
            for (k,v) in parse_qs(event['body']).items():
                if len(v) == 1:
                    params[k] = v[0]
                else:
                    params[k] = v
            return params
        except:
            raise Exception('failed to parse twilio parameters') # Bring your own custom exceptions
    else:
        raise Exception('Request missing body')


class TwilioEventParser():
    def __init__(self, auth_token:str):
        self.validator = RequestValidator(auth_token)

    def validateEvent(self, event:dict, parsedParams:OrderedDict) -> bool:
        twilioSig = event.get('headers').get('X-Twilio-Signature')
        host = event.get('headers').get('Host')
        port = event.get('headers').get('X-Forwarded-Port')
        protocol = event.get('headers').get('X-Forwarded-Proto')
        path = event['path']
        url = f"{protocol}://{host}:{port}{path}"
        isValid = self.validator.validate(url, parsedParams, twilioSig)
        print(f"Validation: {('success' if isValid else 'failure')}")
        return isValid

    def parse(self, event:dict, validate:bool=True) -> OrderedDict:
        messageParams = parseTwilioEventParams(event)
        if not validate:
            return messageParams
        if not self.validateEvent(event, messageParams):
            raise Exception('twilio signature validation failed')
        return messageParams