Verify a license key

import * as wmill from "https://deno.land/x/[email protected]/mod.ts";

// licenseKey generated by https://hub.windmill.dev/scripts/helper/1508/generate-a-license-key-using-rsa-pss-for-a-customer-helper

export async function main(licenseKey: string) {

  const [client, signature] = licenseKey.split('.')

  const data = new TextEncoder().encode(atob(client))

  const signatureAb = Uint8Array.from(atob(signature), c => c.charCodeAt(0))

  // publicKey generated by https://hub.windmill.dev/scripts/helper/1509/generate-an-rsa-pss-key-pair-helper

  let publicKey = await importPublicKey(

    (await wmill.getVariable("u/user/public_license_key"))!,

  );

  let verified = await crypto.subtle.verify(

    {

      name: "RSA-PSS",

      saltLength: 32,

    },

    publicKey,

    signatureAb,

    data

  );

  return verified;

}

function importPublicKey(pem: string) {

  const binaryDerString = window.atob(pem);

  const binaryDer = str2ab(binaryDerString);

  return window.crypto.subtle.importKey(

    "spki",

    binaryDer,

    {

      name: "RSA-PSS",

      hash: "SHA-256",

    },

    true,

    ["verify"],

  );

}

function str2ab(str: string) {

  const buf = new ArrayBuffer(str.length);

  const bufView = new Uint8Array(buf);

  for (let i = 0, strLen = str.length; i < strLen; i++) {

    bufView[i] = str.charCodeAt(i);

  }

  return buf;

}

https://keyguardian.org/a/1308?id=da05ef6e57d84a78b7c6411702449ffd