Callbacks security

How to verify callbacks authenticity

For security reasons, when sending and receiving data and information to and from an external endpoint (i.e. real-time webhooks, external resources) we recommend verifying the callback authenticity by signing the payload with the shared secret (SHA256 HMAC) and comparing the result with the X-CommerceLayer-Signature callback header. In details:

1. Read the X-CommerceLayer-Signature header and get the encrypted signature.

2. Rebuild the signature according to the SHA256 HMAC algorithm, using the payload body and the provided shared secret.

3. Compare your signature with the one you got from the header.

4. If the two signatures match, you can proceed safely — if not, you can't trust the callback.

Example

This is a sample script in Node.js that you can use as a reference to check the signature:

import { createHmac } from "node:crypto";

export default (req, res) => {
  const signature = req.headers['x-commercelayer-signature']
  
  const encode = createHmac("sha256", process.env.CL_SHARED_SECRET)
    .update(req.body)
    .digest("base64");
  
  if (req.method === 'POST' && signature === encode) {
		// your-code
    res.status(200).json({
      success: true,
    })
  } else {
    res.status(401).json({
      error: 'Unauthorized',
    })
  }
}

When verifying the callback authenticity, make sure to read the raw body of the payload and NOT the parsed one.

Do you prefer to use Next.js or Express.js to verify the signature? Check the linked code samples from our Examples open-source repository on GitHub.