Payload signature

Saleor calculates a payload signature and puts the result into Saleor-Signature header:

• DEPRECATED if secretKey was set for a webhook - the HMAC SHA-256 header based on it and the payload
• if secretKey wasn't set for a webhook - the JWS signature using RS256 with payload detached, to verify the signature you can use a public key, which can be fetched from http(s)://<your-backend-domain>/.well-known/jwks.json (available since Saleor 3.5, before 3.5 the payload from webhooks without secretKey set were not signed)

Validating signature

To validate signatures in Saleor Apps, use withWebhookSignatureVerified middleware provided by @saleor/app-sdk

import type { Handler } from "retes";
import { Response } from "retes/response";
import { toNextHandler } from "retes/adapter";
import {
  withSaleorEventMatch,
  withWebhookSignatureVerified,
} from "@saleor/app-sdk/middleware";

const handler: Handler = async (request) => {
  // ...

  return Response.OK({ success: true });
};

export default toNextHandler([
  withSaleorDomainMatch,
  withWebhookSignatureVerified(),
  handler,
]);

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You can also manually validate the JWS signature in JavaScript with the jose package. Remember that you need to supply it with a raw body string, not a parsed object.

import getRawBody from "raw-body";

const JWKS = jose.createRemoteJWKSet(
  new URL("https://master.staging.saleor.cloud" + "/.well-known/jwks.json")
);

// In Next.js you need to disable `bodyParser` in order to get raw body string
// https://github.com/vercel/next.js/discussions/12517
export const config = {
  api: {
    bodyParser: false,
  },
};

export default function(req, res) {
  const jws = req.headers["saleor-signature"];
  const buffer = getRawBody(req, {
    length: req.headers["content-length"],
    limit: "1mb",
  });
  const [header, _, signature] = jws.split(".");
  try {
    await jose.flattenedVerify({
      protected: header,
      payload: buffer.toString("utf-8"),
      signature
    }, JWKS);
  } catch (e) {
    // return error
  }

  // handle your request
}

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