activitypub: transmogrifier: make deletes secure

[akkoma] / lib / pleroma / web / activity_pub / transmogrifier.ex

diff --git a/lib/pleroma/web/activity_pub/transmogrifier.ex b/lib/pleroma/web/activity_pub/transmogrifier.ex
index 6a0fdb433098484bca261e94fdb94fec5eed130a..5864855b0bb8a8f420ec90c2fa3adc00f4b621ec 100644 (file)
--- a/lib/pleroma/web/activity_pub/transmogrifier.ex
+++ b/lib/pleroma/web/activity_pub/transmogrifier.ex
@@ -50,6 +50,19 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
     end
   end
 
+  def contain_origin_from_id(id, %{"id" => nil}), do: :error
+
+  def contain_origin_from_id(id, %{"id" => other_id} = params) do
+    id_uri = URI.parse(id)
+    other_uri = URI.parse(other_id)
+
+    if id_uri.host == other_uri.host do
+      :ok
+    else
+      :error
+    end
+  end
+
   @doc """
   Modifies an incoming AP object (mastodon format) to our internal format.
   """
@@ -454,15 +467,20 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
     end
   end
 
-  # TODO: Make secure.
+  # TODO: We presently assume that any actor on the same origin domain as the object being
+  # deleted has the rights to delete that object.  A better way to validate whether or not
+  # the object should be deleted is to refetch the object URI, which should return either
+  # an error or a tombstone.  This would allow us to verify that a deletion actually took
+  # place.
   def handle_incoming(
-        %{"type" => "Delete", "object" => object_id, "actor" => actor, "id" => _id} = data
+        %{"type" => "Delete", "object" => object_id, "actor" => _actor, "id" => _id} = data
       ) do
     object_id = Utils.get_ap_id(object_id)
 
     with actor <- get_actor(data),
-         %User{} = _actor <- User.get_or_fetch_by_ap_id(actor),
+         %User{} = actor <- User.get_or_fetch_by_ap_id(actor),
          {:ok, object} <- get_obj_helper(object_id) || fetch_obj_helper(object_id),
+         :ok <- contain_origin(actor.ap_id, object.data),
          {:ok, activity} <- ActivityPub.delete(object, false) do
       {:ok, activity}
     else
@@ -589,6 +607,8 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
     |> prepare_attachments
     |> set_conversation
     |> set_reply_to_uri
+    |> strip_internal_fields
+    |> strip_internal_tags
   end
 
   #  @doc
@@ -755,6 +775,29 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
     |> Map.put("attachment", attachments)
   end
 
+  defp strip_internal_fields(object) do
+    object
+    |> Map.drop([
+      "likes",
+      "like_count",
+      "announcements",
+      "announcement_count",
+      "emoji",
+      "context_id"
+    ])
+  end
+
+  defp strip_internal_tags(%{"tag" => tags} = object) do
+    tags =
+      tags
+      |> Enum.filter(fn x -> is_map(x) end)
+
+    object
+    |> Map.put("tag", tags)
+  end
+
+  defp strip_internal_tags(object), do: object
+
   defp user_upgrade_task(user) do
     old_follower_address = User.ap_followers(user)