RailsのCookieStoreをnodeで復号した

setDecryptCookies.ts

import * as crypto from "crypto";
import Marshal from "marshal";

function decrypt(cookie: string): Object {
  const unescapedCookie = unescape(cookie);

  if (!process.env.RAILS_SECRET_KEY_BASE) {
    throw new Error("No Exists process.env.RAILS_SECRET_KEY_BASE");
  }
  const secretKeyBase = process.env.RAILS_SECRET_KEY_BASE;
  const encryptedCookieSalt = "encrypted cookie";
  const encryptedSignedCookieSalt = "signed encrypted cookie";
  const iterations = 1000;
  const keySize = 64;
  const secret = crypto.pbkdf2Sync(secretKeyBase, encryptedCookieSalt, iterations, keySize / 2, "SHA1");
  const signedSecret = crypto.pbkdf2Sync(secretKeyBase, encryptedSignedCookieSalt, iterations, keySize, "SHA1");

  const [data, digest] = unescapedCookie.split("--");

  //   raise 'invalid message' unless digest == OpenSSL::HMAC.hexdigest(OpenSSL::Digest::SHA1.new, sign_secret, data)
  //   # you better use secure compare instead of `==` to prevent time based attact,
  //   # ref: ActiveSupport::SecurityUtils.secure_compare

  const encryptedMessage = Buffer.from(data, "base64").toString();
  const [encryptedData, iv] = encryptedMessage.split("--").map(message => {
    return Buffer.from(message, "base64");
  });

  const decipher = crypto.createDecipheriv("aes-256-cbc", secret, iv);
  let dec = decipher.update(encryptedData);
  dec = Buffer.concat([dec, decipher.final()]);

  const marshal = new Marshal();
  const parsed = marshal.load(dec).parsed;

  return parsed;
}

export const setDecryptCookies = (cookieName: string) => {
  return (req, _, next) => {
    if (req.cookies && req.cookies[cookieName]) {
      // Base64 encode & 暗号化 された文字列をオブジェクトへ変換
      req.cookies[cookieName] = decrypt(req.cookies[cookieName]);
      next();
    } else {
      next();
    }
  };
};