diff --git a/app/core/middleware.py b/app/core/middleware.py index 075bb64..7749d26 100644 --- a/app/core/middleware.py +++ b/app/core/middleware.py @@ -1,23 +1,32 @@ -"""CSRF middleware — Origin header validation for POST/PATCH/DELETE.""" +"""CSRF middleware — Origin header + CSRF token validation for state-changing requests.""" from __future__ import annotations +import json +import logging + from fastapi import Request, status from starlette.middleware.base import BaseHTTPMiddleware from starlette.responses import JSONResponse from app.config import get_settings +logger = logging.getLogger(__name__) + class CSRFMiddleware(BaseHTTPMiddleware): - """Validate Origin header on all state-changing requests. - SameSite=Strict cookie + Origin validation = CSRF protection. + """Validate Origin header and CSRF token on all state-changing requests. + + SameSite=Strict cookie + Origin validation + double-submit CSRF token. + The CSRF token is generated at login and stored in the Redis session. + The client must send it via the X-CSRF-Token header on unsafe methods. """ UNSAFE_METHODS = {"POST", "PATCH", "PUT", "DELETE"} async def dispatch(self, request: Request, call_next): if request.method in self.UNSAFE_METHODS: + # 1. Origin header check origin = request.headers.get("origin") if not origin: return JSONResponse( @@ -27,11 +36,54 @@ class CSRFMiddleware(BaseHTTPMiddleware): settings = get_settings() allowed = settings.cors_origin_list - # In production, same-origin is enforced; in dev, explicit origins if origin not in allowed: return JSONResponse( status_code=status.HTTP_403_FORBIDDEN, content={"detail": "Invalid Origin", "code": "csrf_invalid_origin"}, ) + # 2. CSRF token validation (double-submit pattern) + # Skip CSRF token check for auth endpoints (login/password-reset) + path = request.url.path + if path.endswith("/auth/login") or path.endswith("/auth/logout") or "/password-reset" in path: + return await call_next(request) + + csrf_header = request.headers.get("x-csrf-token") + if not csrf_header: + return JSONResponse( + status_code=status.HTTP_403_FORBIDDEN, + content={"detail": "Missing X-CSRF-Token header", "code": "csrf_missing_token"}, + ) + + # Get session ID from cookie to look up stored CSRF token + session_id = request.cookies.get(settings.session_cookie_name) + if not session_id: + return JSONResponse( + status_code=status.HTTP_403_FORBIDDEN, + content={"detail": "No session for CSRF validation", "code": "csrf_no_session"}, + ) + + # Look up CSRF token from Redis session + import redis.asyncio as aioredis + + redis = aioredis.from_url(settings.redis_url, decode_responses=True) + try: + raw = await redis.get(f"session:{session_id}") + if raw is None: + return JSONResponse( + status_code=status.HTTP_403_FORBIDDEN, + content={"detail": "Session expired for CSRF validation", "code": "csrf_session_expired"}, + ) + + session_data = json.loads(raw) + stored_token = session_data.get("csrf_token") + + if not stored_token or stored_token != csrf_header: + return JSONResponse( + status_code=status.HTTP_403_FORBIDDEN, + content={"detail": "CSRF token mismatch", "code": "csrf_token_mismatch"}, + ) + finally: + await redis.close() + return await call_next(request)