const crypto = require('crypto');

function verifyGitHubWebhook(rawBody, signatureHeader, secret) {
  if (!signatureHeader || !secret) return false;
  
  // GitHub sends: sha256=xxxx
  const [algorithm, signature] = signatureHeader.split('=');
  if (algorithm !== 'sha256') return false;
  
  const expected = crypto
    .createHmac('sha256', secret)
    .update(rawBody)
    .digest('hex');
  
  try {
    return crypto.timingSafeEqual(Buffer.from(signature), Buffer.from(expected));
  } catch {
    return false;
  }
}

const express = require('express');
const app = express();

// CRITICAL: Use express.raw() - GitHub requires raw body for signature verification
app.post('/webhooks/github',
  express.raw({ type: 'application/json' }),
  (req, res) => {
    const signature = req.headers['x-hub-signature-256'];  // Use sha256, not sha1
    const event = req.headers['x-github-event'];
    const delivery = req.headers['x-github-delivery'];
    
    // Verify signature
    if (!verifyGitHubWebhook(req.body, signature, process.env.GITHUB_WEBHOOK_SECRET)) {
      console.error('GitHub signature verification failed');
      return res.status(401).send('Invalid signature');
    }
    
    // Parse payload after verification
    const payload = JSON.parse(req.body.toString());
    
    console.log(`Received ${event} (delivery: ${delivery})`);
    
    // Handle by event type
    switch (event) {
      case 'push':
        console.log(`Push to ${payload.ref}:`, payload.head_commit?.message);
        break;
      case 'pull_request':
        console.log(`PR #${payload.number} ${payload.action}:`, payload.pull_request?.title);
        break;
      case 'issues':
        console.log(`Issue #${payload.issue?.number} ${payload.action}:`, payload.issue?.title);
        break;
      case 'ping':
        console.log('Ping:', payload.zen);
        break;
      default:
        console.log('Received event:', event);
    }
    
    res.json({ received: true });
  }
);

import hmac
import hashlib

def verify_github_webhook(raw_body: bytes, signature_header: str, secret: str) -> bool:
    if not signature_header or not secret:
        return False
    
    # GitHub sends: sha256=xxxx
    try:
        algorithm, signature = signature_header.split('=')
        if algorithm != 'sha256':
            return False
    except ValueError:
        return False
    
    expected = hmac.new(secret.encode(), raw_body, hashlib.sha256).hexdigest()
    return hmac.compare_digest(signature, expected)

GITHUB_WEBHOOK_SECRET=your_webhook_secret   # Set when creating webhook in GitHub

# Install Hookdeck CLI for local webhook testing
brew install hookdeck/hookdeck/hookdeck

# Start tunnel (no account needed)
hookdeck listen 3000 --path /webhooks/github

// Generated with: github-webhooks skill
// https://github.com/hookdeck/webhook-skills