Verify app proxy request if it came through Shopify or not

shopify-app-proxy-authenticated-route

  app.get("/app-proxy", async (req, res) => {
    // Sorted list of query parameters
    const q = {
      path_prefix: req.query['path_prefix'],
      shop: req.query['shop'],
      timestamp: req.query['timestamp'],
    };

    const originalQuerystring = Object.keys(q).map(key => key + '=' + q[key]).join('');
    const crypto = require('crypto')

    function computeSignature(querystringFromClient, shopifyAppSecret) {
        const computedSignature = crypto.createHmac('sha256', shopifyAppSecret)
            .update(querystringFromClient, 'utf-8').digest('hex')
        return computedSignature
    }

    const computedSignature = computeSignature(originalQuerystring, "API_SECRET_KEY")

    console.log(originalQuerystring)
    console.log(computedSignature, req.query);


    if (computedSignature === req.query['signature']) {
      res.setHeader('Content-Type', 'application/liquid');
      res.send("Hello authenticated {{ customer.id }}");
    } else {
      res.send('Error');
    }
  });