trying to mock github webhook request, get: "X-Hub-Signature does not match blob signature"

Question

Here is a little proxy server setup to handle github webhooks:

require('dotenv').config();
var http = require('http');
var createHandler = require('github-webhook-handler');
var handler = createHandler({
  path: '/webhook',
  secret: process.env.GIT_WEBHOOK_SECRET
});

http
  .createServer(function(req, res) {
    handler(req, res, function(err) {
      res.statusCode = 404;
      res.end('no such location');
    });
  })
  .listen(8080);

handler.on('error', function(err) {
  console.error('Error:', err.message);
});

handler.on('push', function(event) {
  console.log(
    'Received a push event for %s to %s',
    event.payload.repository.name,
    event.payload.ref
  );
});

handler.on('issues', function(event) {
  console.log(
    'Received an issue event for %s action=%s: #%d %s',
    event.payload.repository.name,
    event.payload.action,
    event.payload.issue.number,
    event.payload.issue.title
  );
});

In postman, I have these headers set:

The raw body is here: https://developer.github.com/v3/activity/events/types/#pullrequestreviewevent

Here is my pre-request script:

var payload = request.data;
console.log("Using payload as " + payload)
var hash = CryptoJS.HmacSHA1(payload, environment.secret).toString(CryptoJS.enc.Hex)
postman.setGlobalVariable("signature", hash);

I can confirm that the GIT_WEBHOOK_SECRET in .env is the same as what is set in secret in my Postman environment settings.

Answer 1

You need to set content of X-Hub-Signature as parameters with sha1 field :

var payload = request.data;
console.log("Using payload as " + payload)
var hash = CryptoJS.HmacSHA1(payload, environment.secret).toString(CryptoJS.enc.Hex)
postman.setGlobalVariable("signature", "sha1=" + hash);

From validating payloads from Github :

No matter which implementation you use, the hash signature starts with sha1=, using the key of your secret token and your payload body.