Harden web push notifications (#24715)

* reject push endpoints that crash the vapid audience parse

The validator accepted hostnames like "." so https://./x passed, and check_registrations then raised ValueError slicing the endpoint, killing the dispatcher's IPC thread. The validator now rejects empty hostname labels and lives in webpush.py, the audience comes from urlparse, and _build_web_pushers skips stored rows whose endpoint fails validation.

* keep the ipc thread alive when a handler raises

An exception from any dispatcher handler escaped InterProcessCommunicator.read, which only caught ZMQError. The REP thread died owing a reply, so every InterProcessRequestor blocked forever. read now logs the error and replies with an empty response, and Dispatcher.publish and publish_local catch per communicator so one failing communicator can't take down the rest.

* stop push sends from reaching internal addresses

pywebpush posts through requests with redirects enabled, so an endpoint could answer 307 to http://127.0.0.1:5000/api/restart and the sender would follow it into the internal admin port on every alert. Pushers now use a session that never follows redirects, and each send first resolves the endpoint host and skips it unless every address is global.

* keep the previous region grid when the refresh request fails

The IPC reader now replies [] when a handler raises, and process_frames assigned that reply to region_grid unconditionally. The next region lookup then indexed into an empty list and killed the camera's detect process. An empty reply now keeps the current grid until the next daily refresh.

* drop the send-time public address check

Refusing non-global resolved addresses broke Tailscale (100.64.0.0/10), split-horizon DNS and HTTPS_PROXY-only setups, and added little once redirects are no longer followed and TLS verification stays on.

* only skip stored push rows that break the vapid audience

Running the full registration validator over stored rows dropped self-hosted endpoints registered before 0.18 with a non-443 port or a bare / path. _build_web_pushers now skips only non-dict rows, rows with no endpoint, unparsable endpoints and hosts with empty labels, and the warning names the host so the row can be found. Registration still uses the full validator.

frigate/comms/dispatcher.py

@@ -490,7 +490,12 @@ class Dispatcher:
     def publish(self, topic: str, payload: Any, retain: bool = False) -> None:
         """Handle publishing to communicators."""
         for comm in self.comms:
-            comm.publish(topic, payload, retain)
+            try:
+                comm.publish(topic, payload, retain)
+            except Exception:
+                logger.exception(
+                    "Error publishing %s to %s", topic, type(comm).__name__
+                )
 
     def publish_local(self, topic: str, payload: Any) -> None:
         """Publish to every communicator except MQTT.
@@ -501,7 +506,12 @@ class Dispatcher:
             if isinstance(comm, MqttClient):
                 continue
 
-            comm.publish(topic, payload, False)
+            try:
+                comm.publish(topic, payload, False)
+            except Exception:
+                logger.exception(
+                    "Error publishing %s to %s", topic, type(comm).__name__
+                )
 
     def _publish_notices(self) -> None:
         if self.notice_registry is None:

frigate/comms/inter_process.py

@@ -50,7 +50,13 @@ class InterProcessCommunicator(Communicator):
 
                     if isinstance(raw, list):
                         (topic, value) = raw
-                        response = self._dispatcher(topic, value)
+
+                        # REP owes a reply, so a handler error must not end the thread
+                        try:
+                            response = self._dispatcher(topic, value)
+                        except Exception:
+                            logger.exception("Error handling IPC topic %s", topic)
+                            response = None
                     else:
                         logging.warning(
                             f"Received unexpected data type in ZMQ recv_json: {type(raw)}"

frigate/comms/webpush.py

@@ -1,6 +1,7 @@
 """Handle sending notifications for Frigate via Firebase."""
 
 import datetime
+import ipaddress
 import json
 import logging
 import os
@@ -10,7 +11,9 @@ from collections.abc import Callable, Iterator
 from dataclasses import dataclass
 from multiprocessing.synchronize import Event as MpEvent
 from typing import Any
+from urllib.parse import urlparse
 
+import requests
 from py_vapid import Vapid01
 from pywebpush import WebPusher
 from titlecase import titlecase
@@ -41,14 +44,124 @@ class PushNotification:
     ttl: int = 0
 
 
+# Push endpoints are opaque URLs but stay well under this in practice
+MAX_ENDPOINT_LENGTH = 2048
+
+# Suffixes that only ever resolve on the local network
+INTERNAL_HOST_SUFFIXES = (".local", ".localdomain", ".internal", ".home.arpa")
+
+
+def validate_push_endpoint(endpoint: Any) -> str | None:
+    """Return a reason the endpoint is unusable, or None when it is valid.
+
+    Subscriptions are issued by the browser vendor's push service, so a valid
+    endpoint is always a public https URL. Anything else is either a broken
+    registration or an attempt to aim the notification sender somewhere it
+    should not reach.
+    """
+    if not isinstance(endpoint, str) or not endpoint:
+        return "endpoint must be a url"
+
+    if len(endpoint) > MAX_ENDPOINT_LENGTH:
+        return "endpoint is too long"
+
+    try:
+        parsed = urlparse(endpoint)
+        port = parsed.port
+    except ValueError:
+        return "endpoint is not a valid url"
+
+    if parsed.scheme != "https":
+        return "endpoint must use https"
+
+    if parsed.username or parsed.password:
+        return "endpoint must not include credentials"
+
+    if port is not None and port != 443:
+        return "endpoint must use the default https port"
+
+    hostname = parsed.hostname
+
+    if not hostname:
+        return "endpoint must include a hostname"
+
+    try:
+        address = ipaddress.ip_address(hostname)
+    except ValueError:
+        address = None
+
+    if address is not None:
+        # A push service is never reachable at an address only this network can
+        # route, so anything non-global is a misconfiguration at best
+        if not address.is_global:
+            return "endpoint must not use a private address"
+    elif hostname == "localhost" or "." not in hostname:
+        return "endpoint must use a fully qualified hostname"
+    elif "" in hostname.split("."):
+        return "endpoint hostname must not contain empty labels"
+    elif hostname.endswith(INTERNAL_HOST_SUFFIXES):
+        return "endpoint must not use an internal hostname"
+
+    # The subscription token lives in the path
+    if len(parsed.path) <= 1:
+        return "endpoint must include a subscription path"
+
+    return None
+
+
+class _NoRedirectSession(requests.Session):
+    """Session that never follows redirects.
+
+    A push endpoint could otherwise redirect the send to an internal URL.
+    """
+
+    def request(self, *args: Any, **kwargs: Any) -> requests.Response:
+        kwargs["allow_redirects"] = False
+        return super().request(*args, **kwargs)
+
+
+_push_session = _NoRedirectSession()
+
+
+def _vapid_audience(endpoint: str) -> str:
+    parsed = urlparse(endpoint)
+    return f"{parsed.scheme}://{parsed.netloc}"
+
+
 def _build_web_pushers(user: str, subs: list[dict[str, Any]]) -> list[WebPusher]:
     """Build pushers for a user's stored subscriptions, skipping unusable ones."""
     pushers: list[WebPusher] = []
 
     for sub in subs:
+        # Stored rows may predate registration validation, so only skip the
+        # endpoints that would break building the VAPID audience
+        endpoint = sub.get("endpoint") if isinstance(sub, dict) else None
+
+        if not isinstance(endpoint, str):
+            logger.warning(
+                "Skipping notification subscription for %s: no endpoint", user
+            )
+            continue
+
+        try:
+            hostname = urlparse(endpoint).hostname or ""
+        except ValueError:
+            logger.warning(
+                "Skipping notification subscription for %s: unparsable endpoint", user
+            )
+            continue
+
+        if "" in hostname.split("."):
+            logger.warning(
+                "Skipping notification subscription for %s: invalid endpoint host %r",
+                user,
+                hostname,
+            )
+            continue
+
         # WebPusher decodes the stored keys and raises on malformed ones
         try:
-            pushers.append(WebPusher(sub))
+            pushers.append(WebPusher(sub, requests_session=_push_session))
         except Exception:
             logger.warning("Skipping invalid notification subscription for %s", user)
 
@@ -131,7 +244,7 @@ class WebPushClient(Communicator):
             for pushers in self.web_pushers.values():
                 for push in pushers:
                     endpoint: str = push.subscription_info["endpoint"]
-                    endpoints.add(endpoint[0 : endpoint.index("/", 10)])
+                    endpoints.add(_vapid_audience(endpoint))
 
             # create new claim
             for endpoint in endpoints:
@@ -320,9 +433,8 @@ class WebPushClient(Communicator):
 
                 for pusher in self.web_pushers[notification.user]:
                     endpoint = pusher.subscription_info["endpoint"]
-                    headers = self.claim_headers[
-                        endpoint[: endpoint.index("/", 10)]
-                    ].copy()
+
+                    headers = self.claim_headers[_vapid_audience(endpoint)].copy()
                     headers["urgency"] = "high"
 
                     resp = pusher.send(