AP C2S: Restrict creation to `Note`s for now.

lib/pleroma/web/activity_pub/activity_pub_controller.ex

@@ -396,7 +396,10 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubController do
     |> json(err)
   end
 
-  defp handle_user_activity(%User{} = user, %{"type" => "Create"} = params) do
+  defp handle_user_activity(
+         %User{} = user,
+         %{"type" => "Create", "object" => %{"type" => "Note"}} = params
+       ) do
     object =
       params["object"]
       |> Map.merge(Map.take(params, ["to", "cc"]))

test/web/activity_pub/activity_pub_controller_test.exs

@@ -815,6 +815,21 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubControllerTest do
       assert object["content"] == activity["object"]["content"]
     end
 
+    test "it rejects anything beyond 'Note' creations", %{conn: conn, activity: activity} do
+      user = insert(:user)
+
+      activity =
+        activity
+        |> put_in(["object", "type"], "Benis")
+
+      _result =
+        conn
+        |> assign(:user, user)
+        |> put_req_header("content-type", "application/activity+json")
+        |> post("/users/#{user.nickname}/outbox", activity)
+        |> json_response(400)
+    end
+
     test "it inserts an incoming sensitive activity into the database", %{
       conn: conn,
       activity: activity