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 @@ def validate(
       )
       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 @@ def validate(
           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 @@ test "returns object_data in meta for a remote Update" 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