sdp_lambda_forwarder.py

import base64
import json
import urllib.request

def new_response(body=None, status=200, headers=None):
    return {
        'statusCode': status,
        'headers': headers,
        'body': body,
    }

def lambda_handler(event, context):
    try:
        url = event["queryStringParameters"]["url"]
        headers = event["headers"]
        method = event["requestContext"]["http"]["method"]
        b64body = event.get("body")
    except KeyError:
        return new_response(json.dumps(event), status=400)

    WHITELIST_HEADERS = {"location", "retry-after", "link", "authorization"}
    headers = {
        key: value
        for key, value in headers.items()
        if key.lower() in WHITELIST_HEADERS
    }

    if b64body is not None:
        body = base64.b64decode(b64body)
        if len(body) >= 40960:
            return new_response("Request Entity Too Large", status=413)
    else:
        body = None

    try:
        request = urllib.request.Request(url, data=body, headers=headers, method=method)
        response = urllib.request.urlopen(request)
        response_headers = {
            key: value
            for key, value in response.headers.items()
            if key.lower() in WHITELIST_HEADERS
        }
        return {
            'statusCode': response.status,
            'headers': response_headers,
            'body': response.read()
        }
    except Exception as err:
        return new_response(str(err), status=500)