shopify_carrierservice_request.py

import hashlib, base64, hmac, json, settings

def shopify_carrierservice_request(f):
  """
  A decorator thats checks and validates a CarrierService request from Shopify.
  """

  def _hmac_is_valid(body, secret, hmac_to_verify):
    hash            = hmac.new(body, secret, hashlib.sha256)
    hmac_calculated = base64.b64encode(hash.digest())
    return hmac_calculated == hmac_to_verify

  @wraps(f)
  def wrapper(request, *args, **kwargs):
    # Try to get required headers and decode the body of the request.
    try:
      request_hmac  = request.META['HTTP_X_SHOPIFY_HMAC_SHA256']
      request_data  = json.loads(request.body)
    except:
      return HttpResponseBadRequest()

    # Verify the HMAC.
    if not _hmac_is_valid(request.body, settings.SHOPIFY_API_SECRET, request_hmac):
      return HttpResponseForbidden()

    # Otherwise, set properties on the request object and return.
    request.request_data  = request_data
    return f(request, args, kwargs)

  return wrapper