Successfully validate a Starling Bank webhook signature

starling_webhook_valid_express.js

//https://stackoverflow.com/questions/56664705/nodejs-base-64-encoding-of-the-sha-512-digest/59738487#59738487

const express = require("express");
const crypto = require('crypto');
const app = express();
const bodyParser = require('body-parser');

app.use(bodyParser.json({
  verify: (req, res, buf) => {
    req.rawBody = buf
  }
}));

app.post('/starling',async (request,response)=>{

  const secret = 'abcd-efgh-12f3-asd34-casd-whatever';

  let hash = crypto.createHash('sha512');

  hash.update(secret+request.rawBody);

  const sigCheck = hash.digest('base64');
  
  const valid = sigCheck==request.headers['x-hook-signature'];
});