generate shopify multipass token

gen-token.js

const crypto = require("crypto");

class Multipass {
  constructor(multipass_secret) {
    const key_material = crypto.createHash("sha256").update(multipass_secret).digest();
    this.encryption_key = key_material.subarray(0, 16);
    this.signature_key = key_material.subarray(16);
  }

  generate_token(customer_data_hash) {
    customer_data_hash.created_at = new Date().toISOString();
    const ciphertext = this.encrypt(JSON.stringify(customer_data_hash));
    return Buffer.concat([ciphertext, this.sign(ciphertext)]).toString("base64url");
  }

  encrypt(plaintext) {
    const iv = crypto.randomBytes(16);
    const cipher = crypto.createCipheriv("aes-128-cbc", this.encryption_key, iv);
    return Buffer.concat([iv, cipher.update(plaintext), cipher.final()]);
  }

  sign(data) {
    return crypto.createHmac("SHA256", this.signature_key).update(data).digest();
  }
}

const user = { email: "customer@email.com" };
const multipass = new Multipass("secert");
console.log(multipass.generate_token(user));