server/src/lib/password.ts

import crypto from 'crypto';

// Password hashing with Node's built-in scrypt (no external dependency).
// Stored format: `scrypt$<saltHex>$<hashHex>`.
const KEYLEN = 64;
const SALT_BYTES = 16;

export function hashPassword(password: string): string {
  const salt = crypto.randomBytes(SALT_BYTES);
  const hash = crypto.scryptSync(password, salt, KEYLEN);
  return `scrypt$${salt.toString('hex')}$${hash.toString('hex')}`;
}

export function verifyPassword(password: string, stored: string): boolean {
  const parts = stored.split('$');
  if (parts.length !== 3 || parts[0] !== 'scrypt') return false;
  const salt = Buffer.from(parts[1], 'hex');
  const expected = Buffer.from(parts[2], 'hex');
  let actual: Buffer;
  try {
    actual = crypto.scryptSync(password, salt, expected.length);
  } catch {
    return false;
  }
  // Constant-time compare; lengths match by construction (both KEYLEN).
  return actual.length === expected.length && crypto.timingSafeEqual(actual, expected);
}