WhatsApp Flow (Encrypt response)

encrypt_response.py

from base64 import b64decode, b64encode
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
import json

def flip_iv(iv):
    flipped_bytes = []
    for byte in iv:
        flipped_byte = byte ^ 0xFF
        flipped_bytes.append(flipped_byte)
    return bytes(flipped_bytes)

def handler(pd):
    # GET AES Key
    aes_key_b64 = pd.steps["Decrypt_WhatsApp_Key"]["$return_value"]["decrypted_aes_key"]
    print("Decrypt AES Key:", aes_key_b64)

    # Variable iv_base64 like initial IV
    iv_base64 = pd.steps["trigger"]["event"]["body"]["initial_vector"]

    # Decoding AES key and base64 IV to bytes
    aes_key = b64decode(aes_key_b64)
    iv = b64decode(iv_base64)

    # Inverting the IV
    iv_flipped = flip_iv(iv)
    print("Inverted IV:", b64encode(iv_flipped).decode("utf-8"))

    # Adding prints to check the values of the "flow_token" and "status" fields
    #params = {
        #"flow_token": pd.steps["Decrypt_WhatsApp_Message"]["$return_value"]["flow_token"],
        #"status": pd.steps["shopify_developer_app"]["$return_value"]["orders"][0]["id"]
    #}
    #print("Flow_token value:", params["flow_token"])
    #print("Status value:", params["status"])

    response = {
        "version": "3.0",
        "screen": "SUCCESS",
        "data": {
            "extension_messge_response": {
                "params": {
                    "flow_token": pd.steps["Decrypt_WhatsApp_Message"]["$return_value"]["flow_token"],
                    "status": pd.steps["shopify_developer_app"]["$return_value"]["orders"][0]["id"]
                }
            }
        }
    }

    response = json.dumps(response)
    print (response)

    # Encrypting the response
    cipher = Cipher(algorithms.AES(aes_key), modes.GCM(iv_flipped))
    encryptor = cipher.encryptor()
    encrypted = encryptor.update(response.encode("utf-8")) + encryptor.finalize() + encryptor.tag
    encrypted_response = b64encode(encrypted).decode("utf-8")

    return encrypted_response, 200, {"Content-Type": "application/json"}