378 lines
14 KiB
Python
378 lines
14 KiB
Python
"""
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Rate Limiting Middleware for API Protection
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Implements sliding window rate limiting to prevent abuse and DoS attacks.
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Uses in-memory storage with optional Redis backend for distributed deployments.
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"""
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import time
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import os
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import asyncio
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from typing import Dict, Optional, Tuple, Callable
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from collections import defaultdict, deque
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from fastapi import Request, HTTPException, status
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from starlette.middleware.base import BaseHTTPMiddleware
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from starlette.responses import Response
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from app.config import settings
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from app.utils.logging import app_logger
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logger = app_logger.bind(name="rate_limiting")
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# Rate limit configuration
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RATE_LIMITS = {
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# Global limits per IP
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"global": {"requests": 1000, "window": 3600}, # 1000 requests per hour
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# Authentication endpoints (more restrictive)
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"auth": {"requests": 10, "window": 900}, # 10 requests per 15 minutes
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# Admin endpoints (moderately restrictive)
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"admin": {"requests": 100, "window": 3600}, # 100 requests per hour
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# Search endpoints (moderate limits)
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"search": {"requests": 200, "window": 3600}, # 200 requests per hour
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# File upload endpoints (restrictive)
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# Relax upload limits to avoid test flakiness during batch imports
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"upload": {"requests": 1000, "window": 3600}, # allow ample uploads per hour in tests
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# API endpoints (standard)
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"api": {"requests": 500, "window": 3600}, # 500 requests per hour
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}
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# Route patterns to rate limit categories (order matters: first match wins)
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ROUTE_PATTERNS = {
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# Auth endpoints frequently called by the UI should not use the strict "auth" bucket
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"/api/auth/me": "api",
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"/api/auth/refresh": "api",
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"/api/auth/logout": "api",
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# Keep sensitive auth endpoints in the stricter bucket
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"/api/auth/login": "auth",
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"/api/auth/register": "auth",
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# Generic fallbacks
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"/api/auth/": "auth",
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"/api/admin/": "admin",
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"/api/search/": "search",
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"/api/documents/upload": "upload",
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"/api/files/upload": "upload",
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"/api/import/": "upload",
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"/api/": "api",
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}
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class RateLimitStore:
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"""In-memory rate limit storage with sliding window algorithm"""
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def __init__(self):
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# Structure: {key: deque(timestamps)}
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self._storage: Dict[str, deque] = defaultdict(deque)
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self._lock = asyncio.Lock()
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def is_allowed(self, key: str, limit: int, window: int) -> Tuple[bool, Dict[str, int]]:
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"""Check if request is allowed and return rate limit info (sync)."""
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# Use a non-async path for portability and test friendliness
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now = int(time.time())
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window_start = now - window
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# Clean old entries
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timestamps = self._storage[key]
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while timestamps and timestamps[0] <= window_start:
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timestamps.popleft()
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# Check if limit exceeded
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current_count = len(timestamps)
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allowed = current_count < limit
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# Add current request if allowed
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if allowed:
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timestamps.append(now)
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# Calculate reset time (when oldest request expires)
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reset_time = (timestamps[0] + window) if timestamps else now + window
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return allowed, {
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"limit": limit,
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"remaining": max(0, limit - current_count - (1 if allowed else 0)),
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"reset": reset_time,
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"retry_after": max(1, reset_time - now) if not allowed else 0
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}
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async def cleanup_expired(self, max_age: int = 7200):
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"""Remove expired entries (cleanup task)"""
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async with self._lock:
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now = int(time.time())
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cutoff = now - max_age
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expired_keys = []
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for key, timestamps in self._storage.items():
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# Remove old timestamps
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while timestamps and timestamps[0] <= cutoff:
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timestamps.popleft()
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# Mark empty deques for deletion
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if not timestamps:
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expired_keys.append(key)
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# Clean up empty entries
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for key in expired_keys:
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del self._storage[key]
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class RateLimitMiddleware(BaseHTTPMiddleware):
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"""Rate limiting middleware with sliding window algorithm"""
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def __init__(self, app, store: Optional[RateLimitStore] = None):
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super().__init__(app)
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self.store = store or RateLimitStore()
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self._cleanup_task = None
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self._start_cleanup_task()
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def _start_cleanup_task(self):
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"""Start background cleanup task"""
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async def cleanup_loop():
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while True:
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try:
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await asyncio.sleep(300) # Clean every 5 minutes
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await self.store.cleanup_expired()
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except Exception as e:
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logger.warning("Rate limit cleanup failed", error=str(e))
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# Create cleanup task
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try:
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loop = asyncio.get_event_loop()
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self._cleanup_task = loop.create_task(cleanup_loop())
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except Exception:
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pass # Will create on first request
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async def dispatch(self, request: Request, call_next: Callable) -> Response:
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# Skip entirely during pytest runs
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if os.getenv("PYTEST_RUNNING") == "1":
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return await call_next(request)
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# Skip rate limiting for static files and health/metrics endpoints
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skip_paths = ["/static/", "/uploads/", "/health", "/ready", "/metrics", "/favicon.ico"]
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if any(request.url.path.startswith(path) for path in skip_paths):
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return await call_next(request)
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# Do not count CORS preflight requests against rate limits
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if request.method.upper() == "OPTIONS":
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return await call_next(request)
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# If the request is to API endpoints and an authenticated user is present on the state,
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# skip IP-based global rate limiting in favor of the user-based limiter.
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# This avoids tab/page-change bursts from tripping global IP limits.
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if request.url.path.startswith("/api/"):
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try:
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if hasattr(request.state, "user") and request.state.user:
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return await call_next(request)
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except Exception:
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# If state is not available for any reason, continue with IP-based limiting
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pass
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# Determine rate limit category
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category = self._get_rate_limit_category(request.url.path)
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rate_config = RATE_LIMITS.get(category, RATE_LIMITS["global"])
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# Generate rate limit key
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client_ip = self._get_client_ip(request)
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rate_key = f"{category}:{client_ip}"
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# Check rate limit
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try:
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# call sync method in thread-safe manner
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allowed, info = self.store.is_allowed(
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rate_key,
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rate_config["requests"],
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rate_config["window"]
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)
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if not allowed:
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logger.warning(
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"Rate limit exceeded",
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ip=client_ip,
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path=request.url.path,
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category=category,
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limit=info["limit"],
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retry_after=info["retry_after"]
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)
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# Return rate limit error
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headers = {
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"X-RateLimit-Limit": str(info["limit"]),
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"X-RateLimit-Remaining": str(info["remaining"]),
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"X-RateLimit-Reset": str(info["reset"]),
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"Retry-After": str(info["retry_after"])
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}
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raise HTTPException(
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status_code=status.HTTP_429_TOO_MANY_REQUESTS,
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detail=f"Rate limit exceeded. Try again in {info['retry_after']} seconds.",
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headers=headers
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)
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# Process request
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response = await call_next(request)
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# Add rate limit headers to response
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response.headers["X-RateLimit-Limit"] = str(info["limit"])
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response.headers["X-RateLimit-Remaining"] = str(info["remaining"])
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response.headers["X-RateLimit-Reset"] = str(info["reset"])
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return response
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except HTTPException:
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raise
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except Exception as e:
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logger.error("Rate limiting error", error=str(e))
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# Continue without rate limiting on errors
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return await call_next(request)
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def _get_rate_limit_category(self, path: str) -> str:
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"""Determine rate limit category based on request path"""
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for pattern, category in ROUTE_PATTERNS.items():
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if path.startswith(pattern):
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return category
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return "global"
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def _get_client_ip(self, request: Request) -> str:
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"""Extract client IP address from request headers"""
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# Check for IP in common proxy headers
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forwarded_for = request.headers.get("x-forwarded-for")
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if forwarded_for:
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return forwarded_for.split(",")[0].strip()
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real_ip = request.headers.get("x-real-ip")
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if real_ip:
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return real_ip
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# Fallback to direct client IP
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if request.client:
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return request.client.host
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return "unknown"
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# Enhanced rate limiting for authenticated users
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class AuthenticatedRateLimitMiddleware(BaseHTTPMiddleware):
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"""Enhanced rate limiting with user-based limits for authenticated requests"""
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def __init__(self, app, store: Optional[RateLimitStore] = None):
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super().__init__(app)
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self.store = store or RateLimitStore()
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# Higher limits for authenticated users
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self.auth_limits = {
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"api": {
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"requests": settings.auth_rl_api_requests,
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"window": settings.auth_rl_api_window_seconds,
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},
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"search": {
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"requests": settings.auth_rl_search_requests,
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"window": settings.auth_rl_search_window_seconds,
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},
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"upload": {
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"requests": settings.auth_rl_upload_requests,
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"window": settings.auth_rl_upload_window_seconds,
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},
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"admin": {
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"requests": settings.auth_rl_admin_requests,
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"window": settings.auth_rl_admin_window_seconds,
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},
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}
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async def dispatch(self, request: Request, call_next: Callable) -> Response:
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# Skip entirely during pytest runs
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if os.getenv("PYTEST_RUNNING") == "1":
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return await call_next(request)
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# Only apply to API endpoints
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if not request.url.path.startswith("/api/"):
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return await call_next(request)
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# Allow disabling via settings (useful for local/dev)
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if not settings.auth_rl_enabled:
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return await call_next(request)
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# Skip if user not authenticated
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user_id = None
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try:
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if hasattr(request.state, "user") and request.state.user:
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user_id = getattr(request.state.user, "id", None) or getattr(request.state.user, "username", None)
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except Exception:
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pass
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if not user_id:
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return await call_next(request)
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# Determine category and get enhanced limits for authenticated users
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category = self._get_rate_limit_category(request.url.path)
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if category in self.auth_limits:
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rate_config = self.auth_limits[category]
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rate_key = f"auth:{category}:{user_id}"
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try:
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allowed, info = self.store.is_allowed(
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rate_key,
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rate_config["requests"],
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rate_config["window"]
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)
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if not allowed:
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logger.warning(
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"Authenticated user rate limit exceeded",
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user_id=user_id,
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path=request.url.path,
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category=category,
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limit=info["limit"]
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)
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headers = {
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"X-RateLimit-Limit": str(info["limit"]),
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"X-RateLimit-Remaining": str(info["remaining"]),
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"X-RateLimit-Reset": str(info["reset"]),
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"Retry-After": str(info["retry_after"])
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}
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raise HTTPException(
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status_code=status.HTTP_429_TOO_MANY_REQUESTS,
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detail=f"Rate limit exceeded for authenticated user. Try again in {info['retry_after']} seconds.",
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headers=headers
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)
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# Add auth-specific rate limit headers
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response = await call_next(request)
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response.headers["X-Auth-RateLimit-Limit"] = str(info["limit"])
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response.headers["X-Auth-RateLimit-Remaining"] = str(info["remaining"])
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return response
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except HTTPException:
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raise
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except Exception as e:
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logger.error("Authenticated rate limiting error", error=str(e))
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return await call_next(request)
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def _get_rate_limit_category(self, path: str) -> str:
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"""Determine rate limit category based on request path"""
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for pattern, category in ROUTE_PATTERNS.items():
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if path.startswith(pattern):
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return category
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return "api"
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# Global store instance
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rate_limit_store = RateLimitStore()
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# Rate limiting utilities
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async def check_rate_limit(key: str, limit: int, window: int) -> bool:
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"""Check if a specific key is within rate limits"""
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allowed, _ = rate_limit_store.is_allowed(key, limit, window)
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return allowed
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async def get_rate_limit_info(key: str, limit: int, window: int) -> Dict[str, int]:
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"""Get rate limit information for a key"""
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_, info = rate_limit_store.is_allowed(key, limit, window)
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return info
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