使用Google Cloud Function配置Meta WhatsApp Cloud API Webhook验证失败

在Google Cloud Function中搭建Webhook用于接收WhatsApp Business API消息并转发至Front平台时，Meta for WhatsApp配置Webhook时出现错误：
The callback URL or verify token couldn't be validated. Please verify the provided information or try again later.

已确认WhatsApp Business API凭证、Webhook URL配置正确，Google Cloud Function已部署可访问，但查看日志发现验证Webhook时出现：Received message with missing contacts or messages property. Skipping message processing，尝试返回200状态码仍无法解决。

相关代码如下：

const axios = require('axios');

const FRONT_API_TOKEN = 'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzY29wZXMiOlsicHJvdmlzaW9uaW5nIiwicHJpdmF0ZToqIiwic2hhcmVkOioiXSwiaWF0IjoxNjc5NTE0MDU1LCJpc3MiOiJmcm9udCIsInN1YiI6ImI4MGUzZDExODQyMDUzZTk5OGE0IiwianRpIjoiYmM5NzNlNGQyZTA3YTAzMiJ9.7LBqJ5Kw3O65c4GttZuh4K2Zt7fkGIIq9yI96l06TJ8';
const FRONT_CUSTOM_CHANNEL_WEBHOOK_URL = 'https://api2.frontapp.com/channels/cha_ak6s0/incoming_messages';
const VERIFY_TOKEN = 'whatsappfronttoken';

const handleVerification = (req, res) => {
  const queryToken = req.query.verify_token;
  console.log('Verification request received:', req.query);
  if (queryToken === VERIFY_TOKEN) {
    res.send(req.query.challenge);
  } else {
    console.error('Invalid verify token:', queryToken);
    res.sendStatus(403);
  }
};

exports.whatsappHandler = async (req, res) => {
  if (req.query.verify_token) {
    handleVerification(req, res);
  } else {
    const message = req.body;

    if (!message.contacts || !message.messages) {
      console.warn('Received message with missing contacts or messages property. Skipping message processing.');
      res.sendStatus(200);
      return;
    }

    // Extract relevant information from the WhatsApp message
    const sender = message.contacts[0].profile.name || message.contacts[0].wa_id;
    const text = message.messages[0].text.body;

    // Format the message for Front's custom channel webhook URL
    const formattedMessage = {
      sender: {
        name: sender,
        handle: sender,
      },
      subject: 'WhatsApp Message',
      body: text,
      body_format: 'markdown',
    };

    // Forward the message to Front's custom channel webhook URL
    try {
      await axios.post(FRONT_CUSTOM_CHANNEL_WEBHOOK_URL, formattedMessage, {
        headers: {
          'Authorization': `Bearer ${FRONT_API_TOKEN}`,
        },
      });
      res.sendStatus(200);
    } catch (error) {
      console.error(error);
      res.sendStatus(500);
    }
  }
};

Meta的Webhook验证请求是POST请求，不会携带verify_token查询参数，而是将验证信息（hub.mode、hub.verify_token、hub.challenge）放在请求体中。当前代码仅在req.query.verify_token存在时才处理验证逻辑，导致验证请求被误判为普通消息请求，进入后续分支后因缺少contacts和messages字段触发警告，最终虽然返回200，但没有正确响应Meta的验证要求。

修改whatsappHandler函数，优先通过请求体中的hub.mode字段判断是否为验证请求，替换原有的查询参数判断逻辑：

exports.whatsappHandler = async (req, res) => {
  // 处理Meta的Webhook验证请求
  const { hub } = req.body;
  if (hub?.mode === 'subscribe' && hub?.verify_token === VERIFY_TOKEN) {
    res.send(hub.challenge);
    return;
  }

  // 处理普通的WhatsApp消息请求
  const message = req.body;

  if (!message.contacts || !message.messages) {
    console.warn('Received message with missing contacts or messages property. Skipping message processing.');
    res.sendStatus(200);
    return;
  }

  // 原有的消息转发逻辑保持不变
  const sender = message.contacts[0].profile.name || message.contacts[0].wa_id;
  const text = message.messages[0].text.body;

  const formattedMessage = {
    sender: {
      name: sender,
      handle: sender,
    },
    subject: 'WhatsApp Message',
    body: text,
    body_format: 'markdown',
  };

  try {
    await axios.post(FRONT_CUSTOM_CHANNEL_WEBHOOK_URL, formattedMessage, {
      headers: {
        'Authorization': `Bearer ${FRONT_API_TOKEN}`,
      },
    });
    res.sendStatus(200);
  } catch (error) {
    console.error(error);
    res.sendStatus(500);
  }
};

额外注意事项：

• 确保Google Cloud Function的触发方式为HTTP触发，允许所有请求方法（尤其是POST）
• 验证请求的响应需直接返回hub.challenge的原始内容，不能添加额外格式或状态码包装

内容的提问来源于stack exchange，提问作者nvercher