fix: Prevent empty topics (#1245)

README.md

@@ -188,6 +188,7 @@ This is the list of operational codes that can help you understand your deployme
 
 | Code                               | Description                                                                                                                         |
 | ---------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------- |
+| TopicNameRequired                  | You are trying to use Realtime without a topic name set                                                                             |
 | RealtimeDisabledForConfiguration   | The configuration provided to Realtime on connect will not be able to provide you any Postgres Changes                              |
 | TenantNotFound                     | The tenant you are trying to connect to does not exist                                                                              |
 | ErrorConnectingToWebsocket         | Error when trying to connect to the WebSocket server                                                                                |

lib/realtime_web/channels/realtime_channel.ex

@@ -29,6 +29,10 @@ defmodule RealtimeWeb.RealtimeChannel do
   @confirm_token_ms_interval :timer.minutes(5)
 
   @impl true
+  def join("realtime:", _params, _socket) do
+    Logging.log_error_message(:error, "TopicNameRequired", "You must provide a topic name")
+  end
+
   def join("realtime:" <> sub_topic = topic, params, socket) do
     %{
       assigns: %{tenant: tenant_id, log_level: log_level, postgres_cdc_module: module},

mix.exs

@@ -4,7 +4,7 @@ defmodule Realtime.MixProject do
   def project do
     [
       app: :realtime,
-      version: "2.33.66",
+      version: "2.33.67",
       elixir: "~> 1.17.3",
       elixirc_paths: elixirc_paths(Mix.env()),
       start_permanent: Mix.env() == :prod,

test/integration/rt_channel_test.exs

@@ -951,6 +951,22 @@ defmodule Realtime.Integration.RtChannelTest do
     end
   end
 
+  test "handle empty topic by closing the socket" do
+    {socket, _} = get_connection("authenticated")
+    config = %{broadcast: %{self: true}, private: false}
+    realtime_topic = "realtime:"
+
+    WebsocketClient.join(socket, realtime_topic, %{config: config})
+
+    assert_receive %Phoenix.Socket.Message{
+      event: "phx_reply",
+      payload: %{
+        "response" => %{"reason" => "You must provide a topic name"},
+        "status" => "error"
+      }
+    }
+  end
+
   defp token_valid(role), do: generate_token(%{role: role})
   defp token_no_role(), do: generate_token()