Rate Limiting API Protection

Rate Limiting & API Protection

Complete documentation for the nself-chat rate limiting and API protection system.

Overview

The application implements a comprehensive multi-layered security approach:

1. IP Blocking - Whitelist/blacklist management with automatic abuse detection
2. Rate Limiting - Sliding window algorithm with Redis support
3. CSRF Protection - Double-submit cookie pattern
4. Authentication - JWT-based auth with role-based access control

Architecture

Request Flow:
┌─────────────────────────────────────────────────────────────────┐
│                         Client Request                          │
└─────────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│              Layer 1: Next.js Middleware (Edge)                 │
│  • IP Blocking Check (whitelist/blacklist)                      │
│  • Penalty Box Check (temporary blocks)                         │
│  • Rate Limiting (edge-compatible)                              │
│  • Security Headers (CSP, HSTS)                                 │
└─────────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│           Layer 2: API Route Middleware (Server)                │
│  • Error Handling (withErrorHandler)                            │
│  • Logging (withLogging)                                        │
│  • CSRF Protection (withCsrfProtection)                         │
│  • Authentication (withAuth)                                    │
│  • Rate Limiting (withRateLimit)                                │
└─────────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│                     Business Logic Handler                      │
└─────────────────────────────────────────────────────────────────┘

Rate Limiting

Algorithms

1. Sliding Window (Default)

The sliding window algorithm provides smooth rate limiting by tracking individual request timestamps:

import { rateLimiter, RATE_LIMIT_PRESETS } from '@/lib/api/rate-limiter'

// Check rate limit
const result = await rateLimiter.check('user:123', RATE_LIMIT_PRESETS.MESSAGE_SEND)

if (!result.allowed) {
  // Rate limited - return 429
  return Response.json(
    { error: 'Too many requests' },
    {
      status: 429,
      headers: {
        'Retry-After': result.retryAfter.toString(),
      },
    }
  )
}

How it works:

• Stores timestamp for each request in a sorted set (Redis) or array (in-memory)
• Removes requests outside the time window
• Counts remaining requests in the current window
• Smooth rate limiting without sudden resets

2. Token Bucket

The token bucket algorithm allows controlled bursts:

const result = await rateLimiter.checkTokenBucket('user:123', {
  maxRequests: 10,
  windowSeconds: 60,
  burst: 5, // Allow bursts up to 15 total
})

How it works:

• Tokens refill at a constant rate
• Each request consumes 1 token
• Allows bursts when tokens are available
• Better UX for bursty traffic patterns

Rate Limit Presets

Pre-configured rate limits for common scenarios:

// Authentication endpoints
RATE_LIMIT_PRESETS.AUTH // 5/min
RATE_LIMIT_PRESETS.AUTH_SIGNUP // 3/hour
RATE_LIMIT_PRESETS.AUTH_RESET // 3/15min

// Message operations
RATE_LIMIT_PRESETS.MESSAGE_SEND // 10/min + 5 burst
RATE_LIMIT_PRESETS.MESSAGE_EDIT // 20/min

// File uploads
RATE_LIMIT_PRESETS.FILE_UPLOAD // 5/min
RATE_LIMIT_PRESETS.FILE_UPLOAD_LARGE // 2/5min

// Search
RATE_LIMIT_PRESETS.SEARCH // 20/min + 10 burst

// AI operations
RATE_LIMIT_PRESETS.AI_QUERY // 10/min

// General API
RATE_LIMIT_PRESETS.API_USER // 100/min + 20 burst
RATE_LIMIT_PRESETS.API_IP // 500/min

// Other
RATE_LIMIT_PRESETS.GRAPHQL // 100/min
RATE_LIMIT_PRESETS.WEBHOOK // 50/min
RATE_LIMIT_PRESETS.EMAIL_SEND // 10/hour
RATE_LIMIT_PRESETS.EXPORT // 3/hour

Usage in API Routes

Basic Rate Limiting

import { applyRateLimit, RATE_LIMIT_PRESETS } from '@/lib/api/rate-limiter'

export async function POST(request: NextRequest) {
  // Apply rate limit
  const result = await applyRateLimit(
    request,
    RATE_LIMIT_PRESETS.MESSAGE_SEND,
    'user:123' // Optional custom identifier
  )

  if (!result.allowed) {
    return Response.json(
      {
        error: 'Too many requests',
        retryAfter: result.retryAfter,
      },
      {
        status: 429,
        headers: {
          'X-RateLimit-Limit': result.limit.toString(),
          'X-RateLimit-Remaining': '0',
          'X-RateLimit-Reset': result.reset.toString(),
          'Retry-After': result.retryAfter?.toString() || '60',
        },
      }
    )
  }

  // Continue with business logic...
}

Using Middleware

import { compose, withAuth, withRateLimit } from '@/lib/api/middleware'

export const POST = compose(
  withErrorHandler,
  withRateLimit({ limit: 10, window: 60 }),
  withAuth
)(async (request, context) => {
  // Your handler code - rate limit already applied
  return Response.json({ success: true })
})

Custom Rate Limits

const customLimit: RateLimitConfig = {
  maxRequests: 50,
  windowSeconds: 300, // 5 minutes
  burst: 10,
  keyPrefix: 'rl:custom',
}

const result = await rateLimiter.check('identifier', customLimit)

Redis vs In-Memory

The rate limiter automatically uses Redis if available, falling back to in-memory:

# .env.local
REDIS_URL=redis://localhost:6379
# OR
UPSTASH_REDIS_URL=rediss://...

Redis Benefits:

• Distributed rate limiting across multiple servers
• Persistent rate limits (survive server restarts)
• Better performance for high-traffic scenarios
• Atomic operations with Lua scripts

In-Memory Benefits:

• No external dependencies
• Zero latency
• Good for development and low-traffic scenarios
• Automatic cleanup

CSRF Protection

Double-Submit Cookie Pattern

The application uses the secure double-submit cookie pattern:

import { withCsrfProtection } from '@/lib/security/csrf'

export const POST = compose(
  withErrorHandler,
  withCsrfProtection, // Validates CSRF token
  withAuth
)(async (request, context) => {
  // CSRF token validated - safe to proceed
})

Getting CSRF Token

Client-side:

// 1. Get CSRF token
const response = await fetch('/api/csrf')
const { csrfToken, headerName } = await response.json()

// 2. Include in state-changing requests
await fetch('/api/protected', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    [headerName]: csrfToken, // Usually 'X-CSRF-Token'
  },
  body: JSON.stringify({ data: 'example' }),
})

Configuration

# .env.local

# CSRF secret (required in production, auto-generated in dev)
CSRF_SECRET=your-32-character-secret-here

# Skip CSRF validation in development (optional)
SKIP_CSRF=true

Token Lifecycle

• Generation: Random 32-byte token, HMAC-signed
• Storage: HTTP-only cookie (secure in production)
• Validation: Header token must match cookie token
• Expiry: 24 hours
• Refresh: Call /api/csrf to get new token

IP Blocking

Automatic Abuse Detection

The IP blocker automatically blocks IPs based on configurable rules:

import { ipBlocker, DEFAULT_BLOCK_RULES } from '@/lib/security/ip-blocker'

// Automatically applied in middleware
// Triggers based on abuse patterns:
// - Failed login attempts
// - Rate limit violations
// - CSRF violations
// - SQL injection attempts
// - XSS attempts

Block Rules

DEFAULT_BLOCK_RULES = {
  FAILED_LOGIN: {
    threshold: 10, // 10 failed attempts
    windowSeconds: 900, // in 15 minutes
    blockDurationSeconds: 3600, // block for 1 hour
  },
  RATE_LIMIT_ABUSE: {
    threshold: 50, // 50 rate limit hits
    windowSeconds: 300, // in 5 minutes
    blockDurationSeconds: 7200, // block for 2 hours
  },
  SQL_INJECTION: {
    threshold: 1, // immediate block
    windowSeconds: 60,
    blockDurationSeconds: 0, // permanent
  },
  // ... more rules
}

Manual IP Management

import { ipBlocker } from '@/lib/security/ip-blocker'

// Block an IP
await ipBlocker.blockIP(
  '192.168.1.1',
  'Suspicious activity',
  3600 // 1 hour (0 = permanent)
)

// Unblock an IP
await ipBlocker.unblockIP('192.168.1.1')

// Whitelist (never block)
await ipBlocker.addToWhitelist('192.168.1.100')

// Blacklist (always block)
await ipBlocker.addToBlacklist('192.168.1.200')

// Check if blocked
const blocked = await ipBlocker.isBlocked('192.168.1.1')
if (blocked) {
  console.log(blocked.reason)
  console.log(blocked.expiresAt)
}

// Get all blocked IPs
const allBlocked = await ipBlocker.getAllBlockedIPs()

Recording Abuse

import { recordAbuseFromRequest } from '@/lib/security/ip-blocker'

// In your API route
const wasBlocked = await recordAbuseFromRequest(
  request,
  'FAILED_LOGIN',
  'medium' // severity: low | medium | high | critical
)

if (wasBlocked) {
  // IP was automatically blocked due to threshold
  console.log('IP blocked due to abuse')
}

Penalty Box

Temporary blocks for immediate abuse:

import { addToPenaltyBox, isInPenaltyBox, removeFromPenaltyBox } from '@/middleware/rate-limit'

// Add IP to penalty box (1 hour)
addToPenaltyBox('192.168.1.1', 3600)

// Check
if (isInPenaltyBox('192.168.1.1')) {
  // Blocked temporarily
}

// Remove
removeFromPenaltyBox('192.168.1.1')

Response Headers

Rate Limit Headers

All rate-limited responses include:

X-RateLimit-Limit: 100          // Max requests in window
X-RateLimit-Remaining: 95       // Remaining requests
X-RateLimit-Reset: 1640000000   // Unix timestamp when limit resets
Retry-After: 60                 // Seconds to wait (if rate limited)

Security Headers

Applied by middleware:

Content-Security-Policy: ...
X-Frame-Options: DENY
X-Content-Type-Options: nosniff
Referrer-Policy: strict-origin-when-cross-origin
Strict-Transport-Security: max-age=63072000; includeSubDomains; preload

Error Responses

429 Too Many Requests

{
  "error": "Too Many Requests",
  "message": "Rate limit exceeded. Try again in 60 seconds.",
  "code": "RATE_LIMIT_EXCEEDED",
  "retryAfter": 60
}

403 Forbidden (IP Blocked)

{
  "error": "Access Denied",
  "message": "Your IP address has been blocked",
  "code": "IP_BLOCKED",
  "reason": "FAILED_LOGIN (10 violations)",
  "blockedAt": "2024-01-01T00:00:00.000Z",
  "retryAfter": 3600
}

403 Forbidden (CSRF)

{
  "error": "Forbidden",
  "message": "Invalid or missing CSRF token",
  "code": "CSRF_VALIDATION_FAILED"
}

Best Practices

1. Layer Your Protection

// Use multiple layers of protection
export const POST = compose(
  withErrorHandler,      // Handle errors gracefully
  withLogging,          // Log all requests
  withCsrfProtection,   // Prevent CSRF attacks
  withAuth,             // Require authentication
  withRateLimit(...)    // Prevent abuse
)(async (request, context) => {
  // Your secure handler
})

2. Use Appropriate Rate Limits

• Auth endpoints: Very strict (3-5/min)
• Read operations: Lenient (100/min)
• Write operations: Moderate (10-20/min)
• Expensive operations: Strict (5/min)

3. Provide Clear Error Messages

if (!result.allowed) {
  return Response.json(
    {
      error: 'Too Many Requests',
      message: `You've sent too many messages. Please wait ${result.retryAfter} seconds.`,
      retryAfter: result.retryAfter,
      helpUrl: 'https://docs.example.com/rate-limits',
    },
    { status: 429 }
  )
}

4. Monitor and Alert

// Log rate limit violations
if (!result.allowed) {
  console.warn('[RateLimit]', {
    identifier: 'user:123',
    endpoint: '/api/messages',
    limit: result.limit,
    timestamp: new Date().toISOString(),
  })

  // Send to monitoring service
  captureMessage('Rate limit exceeded', {
    tags: { endpoint: '/api/messages' },
    extra: { identifier: 'user:123', limit: result.limit },
  })
}

5. Test Rate Limits

// __tests__/rate-limit.test.ts
import { clearAllRateLimits } from '@/middleware/rate-limit'

describe('Rate Limiting', () => {
  beforeEach(() => {
    clearAllRateLimits() // Clear between tests
  })

  it('should block after limit exceeded', async () => {
    // Make 11 requests (limit is 10)
    for (let i = 0; i < 11; i++) {
      const response = await fetch('/api/test')
      if (i < 10) {
        expect(response.status).toBe(200)
      } else {
        expect(response.status).toBe(429)
      }
    }
  })
})

Environment Variables

# Redis (optional, falls back to in-memory)
REDIS_URL=redis://localhost:6379
UPSTASH_REDIS_URL=rediss://...

# CSRF Protection
CSRF_SECRET=your-32-character-secret-minimum
SKIP_CSRF=true  # Development only

# Skip validation during build
SKIP_ENV_VALIDATION=true

Monitoring

Rate Limit Status Endpoint

// GET /api/rate-limit-status
import { getRateLimitStatus } from '@/middleware/rate-limit'

export async function GET(request: NextRequest) {
  const pathname = request.nextUrl.searchParams.get('path') || '/api/messages'
  const status = getRateLimitStatus(request, pathname)

  return Response.json({
    limit: status.limit,
    remaining: status.remaining,
    reset: new Date(status.reset * 1000).toISOString(),
    allowed: status.allowed,
  })
}

Blocked IPs Dashboard

// GET /api/admin/blocked-ips
import { ipBlocker } from '@/lib/security/ip-blocker'

export async function GET() {
  const blocked = await ipBlocker.getAllBlockedIPs()
  const whitelist = await ipBlocker.getWhitelist()
  const blacklist = await ipBlocker.getBlacklist()

  return Response.json({
    blocked: blocked.map((b) => ({
      ip: b.ip,
      reason: b.reason,
      blockedAt: new Date(b.blockedAt).toISOString(),
      expiresAt: b.expiresAt ? new Date(b.expiresAt).toISOString() : null,
      type: b.blockType,
    })),
    whitelist,
    blacklist,
    stats: {
      totalBlocked: blocked.length,
      totalWhitelisted: whitelist.length,
      totalBlacklisted: blacklist.length,
    },
  })
}

Example: Complete Protected Endpoint

See /src/app/api/example-protected/route.ts for a complete example implementing all protections.

Troubleshooting

Rate Limit Not Working

1. Check Redis connection:

   # Test Redis connection
   redis-cli ping

2. Check logs for errors:

   # Look for [RateLimiter] errors

3. Verify environment variables

False Positives

If legitimate users are being blocked:

1. Adjust rate limit thresholds
2. Add to whitelist:

   await ipBlocker.addToWhitelist('trusted-ip')

3. Review block rules

Performance Issues

1. Use Redis for distributed systems
2. Adjust cleanup intervals
3. Consider using edge middleware only
4. Monitor Redis memory usage

Security Considerations

1. Always use HTTPS in production - Required for secure cookies
2. Set strong CSRF_SECRET - Minimum 32 characters
3. Monitor rate limit violations - Alert on suspicious patterns
4. Regularly review blocked IPs - Clean up expired blocks
5. Test your limits - Ensure they work as expected
6. Use whitelisting carefully - Only for trusted IPs
7. Log security events - For audit and forensics

Migration Guide

From Basic to Advanced

// Before
export async function POST(request: NextRequest) {
  // No protection
  return Response.json({ success: true })
}

// After
export const POST = compose(
  withErrorHandler,
  withLogging,
  withCsrfProtection,
  withAuth,
  withRateLimit({ limit: 10, window: 60 })
)(async (request: AuthenticatedRequest, context) => {
  return successResponse({ success: true })
})

Related Documentation

• Next.js Middleware
• OWASP Rate Limiting
• CSRF Protection