DeleteValidator: Don't federate local deletions of remote objects.

Closes #1497

lib/pleroma/web/activity_pub/object_validator.ex

@@ -19,11 +19,11 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidator do
   def validate(object, meta)
 
   def validate(%{"type" => "Delete"} = object, meta) do
-    with {:ok, object} <-
+    with cng <- DeleteValidator.cast_and_validate(object),
-           object
+         do_not_federate <- DeleteValidator.do_not_federate?(cng),
-           |> DeleteValidator.cast_and_validate()
+         {:ok, object} <- Ecto.Changeset.apply_action(cng, :insert) do
-           |> Ecto.Changeset.apply_action(:insert) do
       object = stringify_keys(object)
+      meta = Keyword.put(meta, :do_not_federate, do_not_federate)
       {:ok, object, meta}
     end
   end

lib/pleroma/web/activity_pub/object_validators/delete_validator.ex

@@ -6,6 +6,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.DeleteValidator do
   use Ecto.Schema
 
   alias Pleroma.Activity
+  alias Pleroma.User
   alias Pleroma.Web.ActivityPub.ObjectValidators.Types
 
   import Ecto.Changeset
@@ -45,12 +46,17 @@ def validate_data(cng) do
     cng
     |> validate_required([:id, :type, :actor, :to, :cc, :object])
     |> validate_inclusion(:type, ["Delete"])
-    |> validate_same_domain()
+    |> validate_actor_presence()
+    |> validate_deletion_rights()
     |> validate_object_or_user_presence()
     |> add_deleted_activity_id()
   end
 
-  def validate_same_domain(cng) do
+  def do_not_federate?(cng) do
+    !same_domain?(cng)
+  end
+
+  defp same_domain?(cng) do
     actor_domain =
       cng
       |> get_field(:actor)
@@ -63,11 +69,17 @@ def validate_same_domain(cng) do
       |> URI.parse()
       |> (& &1.host).()
 
-    if object_domain != actor_domain do
+    object_domain == actor_domain
+  end
+
+  def validate_deletion_rights(cng) do
+    actor = User.get_cached_by_ap_id(get_field(cng, :actor))
+
+    if User.superuser?(actor) || same_domain?(cng) do
       cng
-      |> add_error(:actor, "is not allowed to delete object")
     else
       cng
+      |> add_error(:actor, "is not allowed to delete object")
     end
   end
 

lib/pleroma/web/activity_pub/pipeline.ex

@@ -29,7 +29,9 @@ def common_pipeline(object, meta) do
 
   defp maybe_federate(activity, meta) do
     with {:ok, local} <- Keyword.fetch(meta, :local) do
-      if local do
+      do_not_federate = meta[:do_not_federate]
+
+      if !do_not_federate && local do
         Federator.publish(activity)
         {:ok, :federated}
       else

test/web/activity_pub/object_validator_test.exs

@@ -52,9 +52,11 @@ test "it's invalid if the object doesn't exist", %{valid_post_delete: valid_post
 
     test "it's invalid if the actor of the object and the actor of delete are from different domains",
          %{valid_post_delete: valid_post_delete} do
+      valid_user = insert(:user)
+
       valid_other_actor =
         valid_post_delete
-        |> Map.put("actor", valid_post_delete["actor"] <> "1")
+        |> Map.put("actor", valid_user.ap_id)
 
       assert match?({:ok, _, _}, ObjectValidator.validate(valid_other_actor, []))
 
@@ -66,6 +68,19 @@ test "it's invalid if the actor of the object and the actor of delete are from d
 
       assert {:actor, {"is not allowed to delete object", []}} in cng.errors
     end
+
+    test "it's valid if the actor of the object is a local superuser",
+         %{valid_post_delete: valid_post_delete} do
+      user =
+        insert(:user, local: true, is_moderator: true, ap_id: "https://gensokyo.2hu/users/raymoo")
+
+      valid_other_actor =
+        valid_post_delete
+        |> Map.put("actor", user.ap_id)
+
+      {:ok, _, meta} = ObjectValidator.validate(valid_other_actor, [])
+      assert meta[:do_not_federate]
+    end
   end
 
   describe "likes" do

test/web/common_api/common_api_test.exs

@@ -9,11 +9,13 @@ defmodule Pleroma.Web.CommonAPITest do
   alias Pleroma.Object
   alias Pleroma.User
   alias Pleroma.Web.ActivityPub.ActivityPub
+  alias Pleroma.Web.ActivityPub.Transmogrifier
   alias Pleroma.Web.ActivityPub.Visibility
   alias Pleroma.Web.AdminAPI.AccountView
   alias Pleroma.Web.CommonAPI
 
   import Pleroma.Factory
+  import Mock
 
   require Pleroma.Constants
 
@@ -21,6 +23,84 @@ defmodule Pleroma.Web.CommonAPITest do
   setup do: clear_config([:instance, :limit])
   setup do: clear_config([:instance, :max_pinned_statuses])
 
+  describe "deletion" do
+    test "it allows users to delete their posts" do
+      user = insert(:user)
+
+      {:ok, post} = CommonAPI.post(user, %{"status" => "namu amida butsu"})
+
+      with_mock Pleroma.Web.Federator,
+        publish: fn _ -> nil end do
+        assert {:ok, delete} = CommonAPI.delete(post.id, user)
+        assert delete.local
+        assert called(Pleroma.Web.Federator.publish(delete))
+      end
+
+      refute Activity.get_by_id(post.id)
+    end
+
+    test "it does not allow a user to delete their posts" do
+      user = insert(:user)
+      other_user = insert(:user)
+
+      {:ok, post} = CommonAPI.post(user, %{"status" => "namu amida butsu"})
+
+      assert {:error, "Could not delete"} = CommonAPI.delete(post.id, other_user)
+      assert Activity.get_by_id(post.id)
+    end
+
+    test "it allows moderators to delete other user's posts" do
+      user = insert(:user)
+      moderator = insert(:user, is_moderator: true)
+
+      {:ok, post} = CommonAPI.post(user, %{"status" => "namu amida butsu"})
+
+      assert {:ok, delete} = CommonAPI.delete(post.id, moderator)
+      assert delete.local
+
+      refute Activity.get_by_id(post.id)
+    end
+
+    test "it allows admins to delete other user's posts" do
+      user = insert(:user)
+      moderator = insert(:user, is_admin: true)
+
+      {:ok, post} = CommonAPI.post(user, %{"status" => "namu amida butsu"})
+
+      assert {:ok, delete} = CommonAPI.delete(post.id, moderator)
+      assert delete.local
+
+      refute Activity.get_by_id(post.id)
+    end
+
+    test "superusers deleting non-local posts won't federate the delete" do
+      # This is the user of the ingested activity
+      _user =
+        insert(:user,
+          local: false,
+          ap_id: "http://mastodon.example.org/users/admin",
+          last_refreshed_at: NaiveDateTime.utc_now()
+        )
+
+      moderator = insert(:user, is_admin: true)
+
+      data =
+        File.read!("test/fixtures/mastodon-post-activity.json")
+        |> Jason.decode!()
+
+      {:ok, post} = Transmogrifier.handle_incoming(data)
+
+      with_mock Pleroma.Web.Federator,
+        publish: fn _ -> nil end do
+        assert {:ok, delete} = CommonAPI.delete(post.id, moderator)
+        assert delete.local
+        refute called(Pleroma.Web.Federator.publish(:_))
+      end
+
+      refute Activity.get_by_id(post.id)
+    end
+  end
+
   test "favoriting race condition" do
     user = insert(:user)
     users_serial = insert_list(10, :user)