Validate object data for incoming Update activities

In Create validator we do not validate the object data,
but that is because the object itself will go through the
pipeline again, which is not the case for Update. Thus,
we added validation for objects in Update activities.

lib/pleroma/web/activity_pub/object_validator.ex

@@ -135,8 +135,8 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidator do
       )
       when objtype in ~w[Question Answer Audio Video Event Article Note Page] do
     with {_, false} <- {:local, Access.get(meta, :local, false)},
-         {:ok, object_data} <- cast_and_apply(object),
-         meta = Keyword.put(meta, :object_data, object_data |> stringify_keys),
+         {_, {:ok, object_data, _}} <- {:object_validation, validate(object, meta)},
+         meta = Keyword.put(meta, :object_data, object_data),
          {:ok, update_activity} <-
            update_activity
            |> UpdateValidator.cast_and_validate()
@@ -152,6 +152,9 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidator do
           object = stringify_keys(object)
           {:ok, object, meta}
         end
+
+      {:object_validation, e} ->
+        e
     end
   end
 

test/pleroma/web/activity_pub/object_validators/update_handling_test.exs

@@ -127,4 +127,42 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.UpdateHandlingTest do
       assert meta[:object_data]
     end
   end
+
+  describe "update with history" do
+    setup do
+      user = insert(:user)
+      {:ok, activity} = Pleroma.Web.CommonAPI.post(user, %{status: "mew mew :dinosaur:"})
+      {:ok, edit} = Pleroma.Web.CommonAPI.update(user, activity, %{status: "edited :blank:"})
+      {:ok, external_rep} = Pleroma.Web.ActivityPub.Transmogrifier.prepare_outgoing(edit.data)
+      %{external_rep: external_rep}
+    end
+
+    test "edited note", %{external_rep: external_rep} do
+      {:ok, _validate_res, meta} = ObjectValidator.validate(external_rep, [])
+
+      assert %{"formerRepresentations" => %{"orderedItems" => [%{"emoji" => %{"dinosaur" => _}}]}} =
+               meta[:object_data]
+    end
+
+    test "edited note, badly-formed formerRepresentations", %{external_rep: external_rep} do
+      external_rep = put_in(external_rep, ["object", "formerRepresentations"], %{})
+
+      assert {:error, _} = ObjectValidator.validate(external_rep, [])
+    end
+
+    test "edited note, badly-formed history item", %{external_rep: external_rep} do
+      history_item =
+        Enum.at(external_rep["object"]["formerRepresentations"]["orderedItems"], 0)
+        |> Map.put("type", "Foo")
+
+      external_rep =
+        put_in(
+          external_rep,
+          ["object", "formerRepresentations", "orderedItems"],
+          [history_item]
+        )
+
+      assert {:error, _} = ObjectValidator.validate(external_rep, [])
+    end
+  end
 end