小程序云开发用云函数获取sessionkey和opengid

2018-09-22

目前小程序获取群ID只有一个办法，就是分享小程序到微信群后，用户从微信点小程序进来，才能获取群ID。

测试页面test.wxml

<view>
  <view wx:if="{{openGid}}" class='groupName'>
    群名称：
    <open-data type="groupName" open-gid="{{openGid}}"></open-data>
  </view>
  <view wx:else>
    <button class='button' bindtap='clickReload'>点击加载群名称和群ID</button>
  </view>
  <view class='button'>{{openGid ? openGid : ' '}}</view>
  <view>把这个页面在真机上分享到微信群，然后从群里点进来，再点击按钮就能获取群ID</view>
</view>

test.js

const app = getApp()

Page({
  /**
   * 页面的初始数据
   */
  data: {

  },
 onLoad: function (options) {
    let that = this
    wx.showShareMenu({
//设为true，获取ShareTicket
      withShareTicket: true
    })
    app.getShareTiket(function (globalData) {
      console.log('clickReload---globalData-->' + JSON.stringify(globalData))
      that.setData({
        openGid: globalData.openGid
      })
    })
  },

  clickReload: function () {
    let that = this
    app.getShareTiket(function (globalData) {
      console.log('clickReload---globalData-->' + JSON.stringify(globalData))
      that.setData({
        openGid: globalData.openGid
      })
    })
  }

})

app.js

wx.cloud.init();
App({
 onShow: function (options) {
    let that = this
    if (options && options.scene == 1044) {
      //获取shareTicket
      that.globalData.shareTicket = options.shareTicket
    }
    console.log('onShow---options=--->' + JSON.stringify(options))
  },
  getShareTiket: function (cb) {
    let that = this
    if (that.globalData.shareTicket) {
      wx.getShareInfo({
        shareTicket: that.globalData.shareTicket,
        success: function (res) {
          console.log('getShareTiket---shareTicket-->' + JSON.stringify(res))
          //获取encryptedData、iv
          let js_encryptedData = res.encryptedData
          let js_iv = res.iv
          wx.login({
            success: function (res) {
              //获取code
              console.log('code-->' + res.code)
             
              //调用云函数，破解opengid
              wx.cloud.callFunction({
                name: 'opengid',
                data: {
                  js_code: res.code,
                  appId: 'wx7c1126bc182ab756',
                  encryptedData: js_encryptedData,
                  iv: js_iv
                },
                success: function (res) {
                  console.log('打印opengid' + res.result.openGId);                
                  console.log('res' + JSON.stringify(res));
                  that.globalData.openGid = res.result.openGId
                  console.log('getShareTiket---openGid' + that.globalData.openGid)
                  typeof cb == "function" && cb(that.globalData)
                },
                fail: function (err) {
                  console.log('getShareTiket---err' + JSON.stringify(err))
                }             
              })
            }
          })
        }
      })
    } else {
      console.log('不存在shareTicket')
    }
  },

  globalData: {
    shareTicket: '',
    openGid: ''
   }
})

在云函数couldfunctions目录下新建opengid云函数，在opengid目录下用npm安装crypto和request。

opengid/index.js

const cloud = require('wx-server-sdk');
const WXBizDataCrypt = require('./WXBizDataCrypt')
const requestSync = require('./requestSync')

cloud.init();


/*
传入参数
{
  data:{
    js_code,
    encryptedData,
    iv
  }
}
*/
exports.main = async (event, context) => {
  const code = event.js_code;
  const appid = event.userInfo.appId;
  const encryptedData = event.encryptedData;
  const iv = event.iv;
  const secret = '填你小程序的secret'

  const url = {
    url: 'https://api.weixin.qq.com/sns/jscode2session?appid=' + appid + '&secret=' + secret + '&js_code=' + code + '&grant_type=authorization_code'
  }
  const req = await requestSync(url);
  const session = JSON.parse(req);
  const sessionKey = session.session_key;
  const pc = new WXBizDataCrypt(appid, sessionKey);
  const data = pc.decryptData(encryptedData, iv);
  return data;
}

另外在opengid目录下新建requestSync.js,获取sessionKey

const request = require("request");

const requestSync = async (url) =>
  new Promise((resolve, reject) => {
    request(url, (err, response, body) => {
      if (err) {
        reject(err);
      } else {
        resolve(body);
      }
    })
  })
module.exports = requestSync

在opengid目录下新建WXBizDataCrypt.js,用来解密,这段代码是微信官网示例代码nodejs版本。

var crypto = require('crypto')

function WXBizDataCrypt(appId, sessionKey) {
  this.appId = appId
  this.sessionKey = sessionKey
}

WXBizDataCrypt.prototype.decryptData = function (encryptedData, iv) {
  // base64 decode
  var sessionKey = new Buffer(this.sessionKey, 'base64')
  encryptedData = new Buffer(encryptedData, 'base64')
  iv = new Buffer(iv, 'base64')

  try {
    // 解密
    var decipher = crypto.createDecipheriv('aes-128-cbc', sessionKey, iv)
    // 设置自动 padding 为 true，删除填充补位
    decipher.setAutoPadding(true)
    var decoded = decipher.update(encryptedData, 'binary', 'utf8')
    decoded += decipher.final('utf8')

    decoded = JSON.parse(decoded)

  } catch (err) {
    console.log('try err', err)
    throw new Error('Illegal Buffer1')
  }

  if (decoded.watermark.appid !== this.appId) {
    throw new Error('appid unmatch')
  }

  return decoded
}

module.exports = WXBizDataCrypt

在模拟器上无法获取shareTicket，你要在真机上建一个群，然后分享点击，才能获取shareTicket，进而解出opengid。

代码没有完全调试，直接复制粘贴，可能会报错，如果报错，请留言告知。

整体上看用云函数和原来的服务端开发差不多，熟悉了感觉更方便，毕竟不需要搭建后端了。如果后期微信能像获取openid一样方便的获取群ID那就更好了。现在的过程还是太绕了。

感谢这两位朋友提供的代码，是他们提供轮子。
小程序如何获取群聊的openGid以及名称
小程序用云函数获取opengid

调试过程遇到的坑。

对象不能直接打印出来，需要用JSON.stringify()转成json才能打印出来。