Automated GitHub Release Radar & Changelog Synthesizer for Slack

import express from "express";
import crypto from "crypto";

const app = express();
app.use(express.json({ verify: (req: any, _res, buf) => { req.rawBody = buf; } }));

function verifyGitHubSignature(req: any) {
  const secret = process.env.GITHUB_WEBHOOK_SECRET || "";
  const signature = req.headers["x-hub-signature-256"] as string;
  if (!signature) return false;
  const hmac = crypto.createHmac("sha256", secret);
  const digest = "sha256=" + hmac.update(req.rawBody).digest("hex");
  return crypto.timingSafeEqual(Buffer.from(signature), Buffer.from(digest));
}

app.post("/webhook/github", async (req, res) => {
  if (!verifyGitHubSignature(req)) {
    return res.status(401).send("Invalid Signature");
  }
  const event = req.headers["x-github-event"];
  if (event === "release" && req.body.action === "published") {
    await postToSlack(req.body.release, req.body.repository);
  }
  return res.status(200).send("OK");
});