Brute Force Attack in Sails (Javascript)

A brute force attack against a Sails.js application built with JavaScript focuses on exhausting authentication or token endpoints by submitting a high volume of guesses. Sails does not enforce account lockout or progressive delays by default, so login routes such as POST /auth/local can be hammered with credential guesses. Attackers may use lists of common passwords and previously leaked username patterns to test access to accounts, particularly when passwords are weak or reused across services.

JavaScript on the server side can inadvertently expose timing differences that assist offline brute force campaigns. For example, asynchronous operations that resolve or reject at different speeds depending on whether a username exists can leak user enumeration information. If valid usernames are identified, attackers can narrow their efforts to password-only brute force, reducing the search space and increasing success likelihood.

Endpoints that rely on predictable identifiers or that do not enforce per-IP or per-account rate limiting are susceptible to rapid credential attempts. In Sails, controllers written in JavaScript may expose verbose error messages, such as “username not found” versus “invalid password,” which can be leveraged to refine guesses. Without additional protections like multi-factor authentication or captcha challenges, brute force attacks against authentication paths in JavaScript-driven Sails apps can lead to unauthorized access, privilege escalation, and lateral movement within an application.

middleBrick performs checks across 12 security categories in parallel, including Authentication and Rate Limiting, to detect weaknesses that could allow brute force behavior. By testing the unauthenticated attack surface, the scanner identifies whether login endpoints are resilient to rapid attempts and whether error handling inadvertently aids attackers. Findings are mapped to real-world attack patterns such as OWASP API Top 10 Credential Stuffing and provide remediation guidance to harden authentication flows.

To mitigate brute force risks in Sails with JavaScript, enforce rate limiting at the controller or policy level and standardize error responses to avoid user enumeration. Implement account-level or IP-level throttling and introduce small, consistent delays for failed attempts. Avoid leaking information through timing differences by ensuring the authentication path performs similar operations regardless of whether the username exists.

Below are concrete JavaScript examples for a Sails controller and a custom policy that reduce the effectiveness of brute force attacks.

1. Consistent error response and delay

Ensure that the login response time remains similar for valid and invalid users, and return a generic message.

// api/controllers/AuthController.js
module.exports = {
  login: async function (req, res) {
    const { username, password } = req.body;
    // Simulate work to reduce timing differences
    const start = Date.now();
    const user = await User.findOne({ username }).select('password');
    if (!user) {
      // Still perform a dummy hash to keep timing similar
      await bcrypt.hash(password, 10);
      while (Date.now() - start < 300) { /* busy wait to normalize timing */ }
      return res.unauthorized({ message: 'Invalid credentials' });
    }
    const match = await bcrypt.compare(password, user.password);
    while (Date.now() - start < 300) { /* busy wait to normalize timing */ }
    if (!match) {
      return res.unauthorized({ message: 'Invalid credentials' });
    }
    return res.ok({ token: Jwt.sign({ id: user.id }, Sails.config.jwtSecret) });
  }
};

2. Rate limiting via a custom policy

Create a policy that tracks attempts per identity and enforces progressive delays or temporary blocks.

// api/policies/rate-limit-auth.js
const attempts = new Map();

module.exports = async function (req, res, proceed) {
  const { username } = req.body || {};
  const key = username || req.ip;
  const now = Date.now();
  const WINDOW = 60_000; // 1 minute
  const MAX = 5;

  if (!attempts.has(key)) {
    attempts.set(key, { count: 1, firstAttempt: now });
    return proceed();
  }

  const record = attempts.get(key);
  if (now - record.firstAttempt > WINDOW) {
    attempts.set(key, { count: 1, firstAttempt: now });
    return proceed();
  }

  record.count += 1;
  if (record.count > MAX) {
    return res.status(429).json({ message: 'Too many attempts, try again later.' });
  }

  return proceed();
};

Apply this policy to your authentication route in config/policies.js:

// config/policies.js
module.exports.policies = {
  AuthController: {
    login: ['rate-limit-auth']
  }
};

3. Enforce global rate limits with Express middleware

For broader protection, add an Express-style rate limiter in your Sails hooks or server entry point.

// config/http.js
const rateLimit = require('express-rate-limit');

module.exports.http = {
  middleware: {
    order: ['rateLimiter', 'cookieParser', 'session', 'bodyParser', 'compress', 'poweredBy', '$custom', 'www', 'favicon', '404', '500'],
    rateLimiter: rateLimit({
      windowMs: 15 * 60 * 1000,
      max: 100,
      message: { error: 'Too many requests from this IP, please try again later.' }
    })
  }
};

middleBrick scans for these kinds of configuration and runtime issues across Authentication and Rate Limiting checks, providing prioritized findings with severity levels and remediation guidance. By combining secure coding practices with appropriate middleware and policies, you can significantly reduce the risk of successful brute force attacks against your Sails APIs.