Return 404 when an activity is sent to a deactivated user's /inbox

Also return 404 when the user who sent the activity is believed to be
deactivated. It was already an error, now it just returns a better
reason than "Invalid request". Also send proper errors when either
user is not known at all.

test/pleroma/web/activity_pub/activity_pub_controller_test.exs

@@ -941,23 +941,6 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubControllerTest do
       assert Activity.get_by_ap_id(data["id"])
     end
 
-    test "it rejects an invalid incoming activity", %{conn: conn, data: data} do
-      user = insert(:user, is_active: false)
-
-      data =
-        data
-        |> Map.put("bcc", [user.ap_id])
-        |> Kernel.put_in(["object", "bcc"], [user.ap_id])
-
-      conn =
-        conn
-        |> assign(:valid_signature, true)
-        |> put_req_header("content-type", "application/activity+json")
-        |> post("/users/#{user.nickname}/inbox", data)
-
-      assert "Invalid request." == json_response(conn, 400)
-    end
-
     test "it accepts messages with to as string instead of array", %{conn: conn, data: data} do
       user = insert(:user)
 
@@ -1341,6 +1324,50 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubControllerTest do
       ObanHelpers.perform(all_enqueued(worker: ReceiverWorker))
       assert Activity.get_by_ap_id(data["id"])
     end
+
+    test "it returns an error when receiving an activity sent to a deactivated user", %{
+      conn: conn,
+      data: data
+    } do
+      user = insert(:user)
+      {:ok, _} = User.set_activation(user, false)
+
+      data =
+        data
+        |> Map.put("bcc", [user.ap_id])
+        |> Kernel.put_in(["object", "bcc"], [user.ap_id])
+
+      conn =
+        conn
+        |> assign(:valid_signature, true)
+        |> put_req_header("content-type", "application/activity+json")
+        |> post("/users/#{user.nickname}/inbox", data)
+
+      assert "User deactivated" == json_response(conn, 404)
+    end
+
+    test "it returns an error when receiving an activity sent from a deactivated user", %{
+      conn: conn,
+      data: data
+    } do
+      sender = insert(:user)
+      user = insert(:user)
+      {:ok, _} = User.set_activation(sender, false)
+
+      data =
+        data
+        |> Map.put("bcc", [user.ap_id])
+        |> Map.put("actor", sender.ap_id)
+        |> Kernel.put_in(["object", "bcc"], [user.ap_id])
+
+      conn =
+        conn
+        |> assign(:valid_signature, true)
+        |> put_req_header("content-type", "application/activity+json")
+        |> post("/users/#{user.nickname}/inbox", data)
+
+      assert "Sender deactivated" == json_response(conn, 404)
+    end
   end
 
   describe "GET /users/:nickname/outbox" do