Node.js实现微信支付v3JSAPI

最近做的小程序需要用到微信支付,但是由于后端只会Node.js,所以只能用Node.js实现微信支付功能了,微信支付官方没有提供Node.js的SDK,只好手动实现了,确实有点点麻烦

下单流程

具体实现

后端获取openid

var request = require("../utils/request").request
function code2Session(code) {
    return new Promise((resolve, reject) => {
        if (!code) {
            reject({ errcode: "error_noCode" })
        } else {
            request({
                url: "https://api.weixin.qq.com/sns/jscode2session",
                data: {
                    appid: "wx0da2fc08*******",
                    secret: "19083b917c9d08f***************",
                    js_code: code,
                    grant_type: "authorization_code"
                },
                method: "GET",
            }).then(res => {
                let resObj = JSON.parse(res)
                if (resObj.openid) {
                    resolve({ errcode: "success", data: resObj })
                }
                else if (resObj.errcode == 40163) {
                    reject({ errcode: "error_codeBeenUsed" })
                } else if (resObj.errcode == 40029) {
                    reject({ errcode: "error_invalidCode" })
                } else {
                    reject({ errcode: "error_unknownError" })
                }
            })
        }
    })
}

request是封装axios的方法

后端prepay接口

POST https://api.mch.weixin.qq.com/v3/pay/transactions/jsapi

参数:

{
     mchid: config.mchid,
     out_trade_no: getUUID(),
     appid: config.appid,
     description: "test",
     notify_url: "",
     amount: {
          total: money
     },
     payer: {
          openid: openid
     }
}

数字签名格式

WECHATPAY2-SHA256-RSA2048 mchid="${mchid}",nonce_str="${nonce_str}",signature="${signature}",timestamp="${timestamp}",serial_no="${serial_no}"

mchid为商户号,serial_no为证书序列号

数字签名写法

微信支付的数字签名算法是SHA256withRSA后再base64,一开始打算用crypto实现,但是一直报错,所以用jsrsasign来写了,content是签名内容,privateKey是私钥,hash这里是SHA256withRSA

// rsa.js

const { KJUR, hextob64 } = require('jsrsasign')
/**
 * rsa签名参考：https://www.jianshu.com/p/145eab95322c
 */
var SignUtil = {
    /**
     * rsa签名
     * @param content 签名内容
     * @param privateKey 私钥，PKCS#1
     * @param hash hash算法，SHA256withRSA，SHA1withRSA
     * @returns 返回签名字符串，base64
     */
    rsaSign: function (content, privateKey, hash) {
        // 创建 Signature 对象
        const signature = new KJUR.crypto.Signature({
            alg: hash,
            //!这里指定 私钥 pem!
            prvkeypem: privateKey
        })
        signature.updateString(content)
        const signData = signature.sign()
        // 将内容转成base64
        return hextob64(signData)
    },
}

module.exports = SignUtil

需信息拼接

需加密信息格式如下

HTTP请求方法\n
URL\n
请求时间戳\n
请求随机串\n
请求报文主体\n

使用joinMessage函数拼接

function joinMessage(...args) {
    return args.join("\n") + "\n"
}

发请求

const fs = require("fs")
const axios = require("axios")
const getUUID = require("./getUUID")
const config = require("../config.js")
const utils = require("./utils")
const SignUtil = require("./rsa")
const pem = fs.readFileSync("./certs/apiclient_key.pem").toString()

function calcSign(msg) {
    return SignUtil.rsaSign(msg, pem, "SHA256withRSA")
}

function prepay(money, openid) {
    return new Promise((resolve, reject) => {
        let nonce_str = getUUID()
        let ts = utils.getTimeStamp()
        let reqBody = {
            mchid: config.mchid,
            out_trade_no: getUUID(),
            appid: config.appid,
            description: "test",
            notify_url: "https://waimai.diaoan.xyz/callback",
            amount: {
                total: money
            },
            payer: {
                openid: openid
            }
        }
        let msg = utils.joinMessage("POST", "/v3/pay/transactions/jsapi", ts, nonce_str, JSON.stringify(reqBody))
        let signature = calcSign(msg)
        let auth = `WECHATPAY2-SHA256-RSA2048 mchid="${config.mchid}",nonce_str="${nonce_str}",signature="${signature}",timestamp="${ts}",serial_no="${config.serial_no}"`
        console.log(msg);
        console.log(signature);
        console.log(auth);
        axios.post("https://api.mch.weixin.qq.com/v3/pay/transactions/jsapi", reqBody, {
            headers: {
                Authorization: auth
            }
        }).then(res => {
            if (res.status == 200) {
                let package = `prepay_id=${res.data.prepay_id}`
                let paySignMsg = utils.joinMessage(config.appid, ts, nonce_str, package)
                let paySign = calcSign(paySignMsg)
                resolve({
                    nonce_str: nonce_str,
                    ts: ts,
                    prepay_id: res.data.prepay_id,
                    paySign: paySign
                })
            }
        }).catch(err => {
            console.log(err)
            reject(err)
        })
    })
}

生成paySign

顺序是appid,ts,nonce_str,package,不能弄错,拼接后,再进行一次数字签名,传到前端

前端唤起微信支付

api.request({
  url: "/prepay",
  method: "POST",
  data: {
    money: 1,
    openid: wx.getStorageSync('user').openid
  }
}).then(res => {
  console.log(res)
  let data = {
    nonceStr: res.data.nonce_str,
    package: `prepay_id=${res.data.prepay_id}`,
    paySign: res.data.paySign,
    timeStamp: res.data.ts.toString(),
    signType: "RSA"
  }
  console.log(data)
  wx.requestPayment(data)
}).catch(err => {
  console.log(err)
})

api.request是对wx.request的封装

这样就完成了微信支付小程序的下单

用到的几个函数

calcSign

function calcSign(msg) {
    return SignUtil.rsaSign(msg, pem, "SHA256withRSA")
}
// msg为需加密内容,pem是用fs模块读取证书文件并转成字符串

getTimeStamp

function getTimeStamp() {
    return Math.round(+new Date / 1000)
}
// 返回10位时间戳

joinMessage

function joinMessage(...args) {
    return args.join("\n") + "\n"
}
// 将传入的参数以每行一个的形式转化成字符串

getUUID

var guid = require("guid")
function getUUID() {
    return guid.create().value.replace(/-/g, "").slice(0, 30)
}
// 生成32位UUID