MP-Server/macropad-relay/src/utils/authThrottle.ts

// Auth brute-force lockout (in-memory).
//
// Tracks failed authentication attempts keyed by an opaque, namespaced key
// (e.g. `web:${sessionId}:${clientIp}` or `desktop:${sessionId}:${clientIp}`).
// Namespacing by path and client IP keeps the web and desktop keyspaces
// separate so one abusive web client cannot lock out other users or the
// desktop for the same session. After `authLockoutMaxAttempts` failures within
// `authLockoutWindowMs`, further attempts are rejected until
// `authLockoutDurationMs` has elapsed.

import { config } from '../config';

interface AttemptRecord {
  count: number;
  windowStart: number;
  lockedUntil: number;
}

const records = new Map<string, AttemptRecord>();

/**
 * Returns the number of milliseconds remaining on a lockout for this key,
 * or 0 if the key is not currently locked.
 */
export function getLockoutRemaining(key: string): number {
  const rec = records.get(key);
  if (!rec) return 0;
  const now = Date.now();
  if (rec.lockedUntil > now) {
    return rec.lockedUntil - now;
  }
  return 0;
}

/**
 * Record a failed auth attempt. Returns the lockout remaining (ms) after
 * this failure is applied (0 if still not locked).
 */
export function recordFailure(key: string): number {
  const now = Date.now();
  let rec = records.get(key);

  // Start a fresh window if none exists or the current one has expired.
  if (!rec || now - rec.windowStart > config.authLockoutWindowMs) {
    rec = { count: 0, windowStart: now, lockedUntil: 0 };
    records.set(key, rec);
  }

  rec.count += 1;

  if (rec.count >= config.authLockoutMaxAttempts) {
    rec.lockedUntil = now + config.authLockoutDurationMs;
  }

  return rec.lockedUntil > now ? rec.lockedUntil - now : 0;
}

/**
 * Clear any recorded failures for this key (call on successful auth).
 */
export function recordSuccess(key: string): void {
  records.delete(key);
}

// Periodically drop stale records so the map does not grow unbounded.
const cleanup = setInterval(() => {
  const now = Date.now();
  for (const [key, rec] of records) {
    const windowExpired = now - rec.windowStart > config.authLockoutWindowMs;
    const notLocked = rec.lockedUntil <= now;
    if (windowExpired && notLocked) {
      records.delete(key);
    }
  }
}, Math.max(60000, config.authLockoutWindowMs));

// Do not keep the process alive solely for this timer.
if (typeof cleanup.unref === 'function') {
  cleanup.unref();
}