在WhatsApp Flow执行data_exchange时遇payload解密失败求助

执行WhatsApp Flow的data_exchange操作时触发错误，使用的是Facebook官方data_exchange示例，收到错误提示：

We failed to decrypt your payload. Please check your encryption/decryption logic.

自身编写的解密代码能正常运行，以下是相关代码，请求协助排查问题：

解密代码 #

def decrypt_request(self,encrypted_flow_data_b64, encrypted_aes_key_b64, initial_vector_b64):
    flow_data = b64decode(encrypted_flow_data_b64)
    iv = b64decode(initial_vector_b64)

    # 解密AES密钥
    encrypted_aes_key = b64decode(encrypted_aes_key_b64)
    
    PRIVATE_KEY = request.env['res.company'].search([],limit=1)
    encoded_data = b64decode(PRIVATE_KEY.private_key_attachment).decode('utf-8').encode('utf-8')
    private_key = load_pem_private_key(
        encoded_data, password=None)
    aes_key = private_key.decrypt(encrypted_aes_key, OAEP(
        mgf=MGF1(algorithm=hashes.SHA256()), algorithm=hashes.SHA256(), label=None))

    # 解密Flow数据
    encrypted_flow_data_body = flow_data[:-16]
    encrypted_flow_data_tag = flow_data[-16:]
    decryptor = Cipher(algorithms.AES(aes_key),
                       modes.GCM(iv, encrypted_flow_data_tag)).decryptor()
    decrypted_data_bytes = decryptor.update(
        encrypted_flow_data_body) + decryptor.finalize()
    decrypted_data = json.loads(decrypted_data_bytes.decode("utf-8"))
    return decrypted_data, aes_key, iv

加密代码 #

def encrypt_response(self,response, aes_key, iv):
    # 翻转初始化向量
    flipped_iv = bytearray(b ^ 0xFF for b in iv)
    
    # 加密响应数据
    encryptor = Cipher(
        algorithms.AES(aes_key),
        modes.GCM(flipped_iv[:12]),
        backend=default_backend()
    ).encryptor()
    
    # 加密并完成
    response_bytes = json.dumps(response).encode("utf-8")
    ciphertext = encryptor.update(response_bytes) + encryptor.finalize()
    
    # 拼接密文和标签
    encrypted_payload = ciphertext + encryptor.tag
    
    # Base64编码
    encoded_payload = b64encode(encrypted_payload).decode("utf-8")
    
    return encoded_payload

主方法代码 #

def whatsapp_data_exchange_flow(self,**kw):
    data = json.loads(request.httprequest.data)

    # 读取请求字段
    encrypted_flow_data_b64 = data['encrypted_flow_data']
    encrypted_aes_key_b64 = data['encrypted_aes_key']
    initial_vector_b64 = data['initial_vector']

    decrypted_data, aes_key, iv = self.decrypt_request(
        encrypted_flow_data_b64, encrypted_aes_key_b64, initial_vector_b64)
    print(decrypted_data)

    # 返回下一个页面及数据给客户端
    response = {
        "version": "3.0",
        "screen": "BOOKING_INFO"
    }
    encrpted_response = self.encrypt_response(response, aes_key, iv)

    headers = werkzeug.datastructures.Headers(None)
    headers['Content-Type'] = 'text/plain'
    response = request.make_response(final_response,headers=headers.to_wsgi_list(),status=200)
    return response

可能的排查方向 #

• 变量名错误：主方法中final_response未定义，实际应使用加密后的encrpted_response，此错误会导致返回无效内容，触发解密失败
• IV处理验证：确认原IV长度是否为12字节（GCM标准长度），加密时截取flipped_iv[:12]若原IV长度不足会导致IV异常
• 响应格式检查：确保返回的是纯Base64字符串，无额外空格、换行或其他字符
• 密钥解密参数：验证OAEP填充的哈希算法、MGF函数是否与Facebook官方要求完全一致
• 响应头确认：虽然官方文档标注返回text/plain，但可尝试切换为application/json测试是否兼容

内容的提问来源于stack exchange，提问作者Mayur Nagar