reject cross-origin websocket handshakes

Neither /ws nor the jsmpeg websockets checked Origin, and the internal port grants admin to everyone, so any page a LAN user visited could open ws://frigate:5000/ws and send commands or read streams. Both servers now reject a browser handshake whose Origin host matches neither Host nor X-Forwarded-Host, and allow handshakes without an Origin for non-browser clients. nginx now forwards an outer proxy's X-Forwarded-Host instead of overwriting it, so proxies that rewrite Host and the Home Assistant integration's proxy still match.

docker/main/rootfs/usr/local/nginx/conf/nginx.conf

@@ -54,6 +54,13 @@ http {
         default 1;
     }
 
+    # keep an outer proxy's X-Forwarded-Host so the websocket servers can
+    # match a browser's Origin when that proxy rewrites Host
+    map $http_x_forwarded_host $forwarded_host {
+        "" $http_host;
+        default $http_x_forwarded_host;
+    }
+
     upstream frigate_api {
         server 127.0.0.1:5001;
         keepalive 1024;

docker/main/rootfs/usr/local/nginx/conf/proxy.conf

@@ -4,7 +4,7 @@ proxy_set_header Upgrade $http_upgrade;
 proxy_set_header Connection "Upgrade";
 proxy_set_header X-Original-URL $request_uri;
 proxy_set_header X-Forwarded-Proto $scheme;
-proxy_set_header X-Forwarded-Host $http_host;
+proxy_set_header X-Forwarded-Host $forwarded_host;
 proxy_set_header X-Forwarded-URI $request_uri;
 proxy_set_header X-Forwarded-Ssl on;
 proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

docs/docs/guides/reverse_proxy.md

@@ -37,6 +37,8 @@ Your reverse proxy must be configured to forward the `Upgrade` and `Connection`
 
 Note that some proxies disable WebSocket support by default. For example, Nginx Proxy Manager has a "Websockets Support" toggle that must be enabled.
 
+Frigate rejects WebSocket connections opened from a page on another site. Your proxy must either preserve the original `Host` header or send it in `X-Forwarded-Host`, otherwise Frigate cannot tell the connection came from its own UI.
+
 ## Proxies
 
 There are many solutions available to implement reverse proxies and the community is invited to help out documenting others through a contribution to this page.

frigate/comms/ws.py

@@ -9,6 +9,7 @@ import struct
 import threading
 from collections.abc import Callable
 from typing import Any
+from urllib.parse import urlsplit
 from wsgiref.simple_server import make_server
 
 from ws4py.server.wsgirefserver import (
@@ -472,6 +473,52 @@ def _materialize_for_ws(
     return None
 
 
+def _hostname(value: str) -> str | None:
+    try:
+        return urlsplit(value).hostname
+    except ValueError:
+        return None
+
+
+def ws_origin_allowed(environ: dict[str, Any]) -> bool:
+    """Return True unless a browser opened the handshake from a foreign origin.
+
+    Browsers always send Origin on a WebSocket handshake and cannot add custom
+    headers to one, so a missing Origin means a non-browser client and a proxy
+    supplied X-Forwarded-Host cannot be forged by the page. Ports are ignored
+    because nginx forwards Host without one.
+    """
+    origin = environ.get("HTTP_ORIGIN")
+    if origin is None:
+        return True
+
+    origin_host = _hostname(origin)
+    if not origin_host:
+        return False
+
+    forwarded_host = environ.get("HTTP_X_FORWARDED_HOST", "").split(",")[0].strip()
+    hosts = (forwarded_host, environ.get("HTTP_HOST", ""))
+    return any(origin_host == _hostname(f"//{host}") for host in hosts if host)
+
+
+class OriginCheckedWebSocketApplication(WebSocketWSGIApplication):  # type: ignore[misc]
+    """ws4py application that rejects cross-origin browser handshakes."""
+
+    def __call__(self, environ: dict[str, Any], start_response: Callable) -> Any:
+        if not ws_origin_allowed(environ):
+            logger.warning(
+                "Rejected cross-origin websocket handshake: origin=%s, host=%s, "
+                "x-forwarded-host=%s",
+                environ.get("HTTP_ORIGIN"),
+                environ.get("HTTP_HOST"),
+                environ.get("HTTP_X_FORWARDED_HOST"),
+            )
+            start_response("403 Forbidden", [("Content-Length", "0")])
+            return []
+
+        return super().__call__(environ, start_response)
+
+
 class WebSocket(WebSocket_):  # type: ignore[misc]
     def __init__(self, *args: Any, **kwargs: Any) -> None:
         super().__init__(*args, **kwargs)
@@ -621,7 +668,7 @@ class WebSocketClient(Communicator):
             5002,
             server_class=WSGIServer,
             handler_class=WebSocketWSGIRequestHandler,
-            app=WebSocketWSGIApplication(handler_cls=_WebSocketHandler),
+            app=OriginCheckedWebSocketApplication(handler_cls=_WebSocketHandler),
         )
         self.websocket_server.initialize_websockets_manager()
         self.websocket_thread = threading.Thread(

frigate/output/output.py

@@ -14,11 +14,10 @@ from ws4py.server.wsgirefserver import (
     WebSocketWSGIRequestHandler,
     WSGIServer,
 )
-from ws4py.server.wsgiutils import WebSocketWSGIApplication
 
 from frigate.comms.config_updater import ConfigSubscriber
 from frigate.comms.detections_updater import DetectionSubscriber, DetectionTypeEnum
-from frigate.comms.ws import WebSocket
+from frigate.comms.ws import OriginCheckedWebSocketApplication, WebSocket
 from frigate.config import FrigateConfig
 from frigate.config.camera.updater import (
     CameraConfigUpdateEnum,
@@ -136,7 +135,7 @@ class OutputProcess(FrigateProcess):
             8082,
             server_class=WSGIServer,
             handler_class=WebSocketWSGIRequestHandler,
-            app=WebSocketWSGIApplication(handler_cls=WebSocket),
+            app=OriginCheckedWebSocketApplication(handler_cls=WebSocket),
         )
         websocket_server.initialize_websockets_manager()
         websocket_thread = threading.Thread(target=websocket_server.serve_forever)

frigate/test/test_ws_origin.py

@@ -0,0 +1,121 @@
+"""Tests for the WebSocket handshake Origin check."""
+
+import unittest
+from unittest.mock import MagicMock
+
+from frigate.comms.ws import (
+    OriginCheckedWebSocketApplication,
+    WebSocket,
+    ws_origin_allowed,
+)
+
+
+class TestWsOriginAllowed(unittest.TestCase):
+    def test_missing_origin_allowed(self):
+        self.assertTrue(ws_origin_allowed({"HTTP_HOST": "frigate.lan"}))
+
+    def test_direct_access_same_origin(self):
+        # nginx forwards Host without the port and X-Forwarded-Host with it
+        environ = {
+            "HTTP_ORIGIN": "http://192.168.1.10:5000",
+            "HTTP_HOST": "192.168.1.10",
+            "HTTP_X_FORWARDED_HOST": "192.168.1.10:5000",
+        }
+        self.assertTrue(ws_origin_allowed(environ))
+
+    def test_default_port_origin(self):
+        environ = {
+            "HTTP_ORIGIN": "https://frigate.example.com",
+            "HTTP_HOST": "frigate.example.com",
+        }
+        self.assertTrue(ws_origin_allowed(environ))
+
+    def test_host_comparison_is_case_insensitive(self):
+        environ = {
+            "HTTP_ORIGIN": "https://Frigate.Example.com",
+            "HTTP_HOST": "frigate.example.COM",
+        }
+        self.assertTrue(ws_origin_allowed(environ))
+
+    def test_ipv6_host(self):
+        environ = {"HTTP_ORIGIN": "http://[::1]:8971", "HTTP_HOST": "[::1]"}
+        self.assertTrue(ws_origin_allowed(environ))
+
+    def test_cross_origin_rejected(self):
+        environ = {
+            "HTTP_ORIGIN": "https://evil.example",
+            "HTTP_HOST": "frigate.lan",
+            "HTTP_X_FORWARDED_HOST": "frigate.lan:5000",
+        }
+        self.assertFalse(ws_origin_allowed(environ))
+
+    def test_null_origin_rejected(self):
+        self.assertFalse(
+            ws_origin_allowed({"HTTP_ORIGIN": "null", "HTTP_HOST": "frigate.lan"})
+        )
+
+    def test_proxy_rewriting_host_with_forwarded_host(self):
+        environ = {
+            "HTTP_ORIGIN": "https://frigate.example.com",
+            "HTTP_HOST": "10.0.0.5",
+            "HTTP_X_FORWARDED_HOST": "frigate.example.com",
+        }
+        self.assertTrue(ws_origin_allowed(environ))
+
+    def test_forwarded_host_list_uses_first_entry(self):
+        environ = {
+            "HTTP_ORIGIN": "https://frigate.example.com",
+            "HTTP_HOST": "10.0.0.5",
+            "HTTP_X_FORWARDED_HOST": "frigate.example.com, proxy.internal",
+        }
+        self.assertTrue(ws_origin_allowed(environ))
+
+        environ["HTTP_ORIGIN"] = "https://proxy.internal"
+        self.assertFalse(ws_origin_allowed(environ))
+
+    def test_home_assistant_ingress(self):
+        # HA core copies Host and sets X-Forwarded-Host to its own host
+        environ = {
+            "HTTP_ORIGIN": "https://ha.example.com:8123",
+            "HTTP_HOST": "ha.example.com",
+            "HTTP_X_FORWARDED_HOST": "ha.example.com:8123",
+            "HTTP_X_INGRESS_PATH": "/api/hassio_ingress/abc123",
+        }
+        self.assertTrue(ws_origin_allowed(environ))
+
+    def test_ingress_path_does_not_bypass_origin_check(self):
+        environ = {
+            "HTTP_ORIGIN": "https://evil.example",
+            "HTTP_HOST": "frigate.example.com",
+            "HTTP_X_INGRESS_PATH": "/frigate",
+        }
+        self.assertFalse(ws_origin_allowed(environ))
+
+    def test_home_assistant_integration_proxy(self):
+        # hass-web-proxy-lib drops Host, so Host is the integration's Frigate URL
+        environ = {
+            "HTTP_ORIGIN": "https://ha.example.com:8123",
+            "HTTP_HOST": "frigate.lan",
+            "HTTP_X_FORWARDED_HOST": "ha.example.com:8123",
+        }
+        self.assertTrue(ws_origin_allowed(environ))
+
+
+class TestOriginCheckedWebSocketApplication(unittest.TestCase):
+    def test_cross_origin_handshake_gets_403(self):
+        app = OriginCheckedWebSocketApplication(handler_cls=WebSocket)
+        start_response = MagicMock()
+        environ = {
+            "REQUEST_METHOD": "GET",
+            "HTTP_ORIGIN": "https://evil.example",
+            "HTTP_HOST": "frigate.lan",
+        }
+
+        self.assertEqual(app(environ, start_response), [])
+        start_response.assert_called_once()
+        self.assertEqual(start_response.call_args.args[0], "403 Forbidden")
+        self.assertNotIn("ws4py.websocket", environ)
+
+
+if __name__ == "__main__":
+    unittest.main()

web/vite.config.ts

@@ -28,7 +28,6 @@ export default defineConfig({
       },
       "/live": {
         target: `ws://${proxyHost}`,
-        changeOrigin: true,
         ws: true,
       },
     },