leocrm/app/core/middleware.py

"""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 SecurityHeadersMiddleware(BaseHTTPMiddleware):
    """Add security headers to all responses."""

    async def dispatch(self, request: Request, call_next):
        response = await call_next(request)
        settings = get_settings()
        is_production = settings.environment == "production"

        # HSTS — only in production (HTTPS assumed behind proxy)
        if is_production:
            response.headers["Strict-Transport-Security"] = (
                "max-age=63072000; includeSubDomains; preload"
            )

        # Prevent MIME type sniffing
        response.headers["X-Content-Type-Options"] = "nosniff"

        # Prevent clickjacking
        response.headers["X-Frame-Options"] = "DENY"

        # Content Security Policy — restrictive but allows inline styles for SPA
        response.headers["Content-Security-Policy"] = (
            "default-src 'self'; "
            "script-src 'self'; "
            "style-src 'self' 'unsafe-inline'; "
            "img-src 'self' data: blob:; "
            "font-src 'self'; "
            "connect-src 'self' wss: ws:; "
            "frame-ancestors 'none'; "
            "base-uri 'self'; "
            "form-action 'self'"
        )

        # Referrer policy
        response.headers["Referrer-Policy"] = "strict-origin-when-cross-origin"

        # Permissions policy
        response.headers["Permissions-Policy"] = (
            "geolocation=(), microphone=(), camera=()"
        )

        return response


class CSRFMiddleware(BaseHTTPMiddleware):
    """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):
        # Skip WebSocket upgrade requests — they use GET and are handled separately
        if request.headers.get("upgrade", "").lower() == "websocket":
            return await call_next(request)

        if request.method in self.UNSAFE_METHODS:
            # 1. Origin header check
            origin = request.headers.get("origin")
            if not origin:
                return JSONResponse(
                    status_code=status.HTTP_403_FORBIDDEN,
                    content={"detail": "Missing Origin header", "code": "csrf_missing_origin"},
                )

            settings = get_settings()
            allowed = settings.cors_origin_list
            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 or path.endswith("/api/v1/errors") or path == "/api/v1/errors":
                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 (use singleton)
            from app.core.auth import get_redis

            redis = get_redis()
            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"},
                )

            # Sliding session: also extend TTL on CSRF-validated unsafe requests
            await redis.expire(f"session:{session_id}", settings.session_ttl_seconds)

        return await call_next(request)