MRF: Add filtering against AP id

changelog.d/mrf-id_filter.add

@@ -0,0 +1 @@
+Add `id_filter` to MRF to filter URLs and their domain prior to fetching

lib/pleroma/web/activity_pub/mrf.ex

@@ -108,6 +108,14 @@ defmodule Pleroma.Web.ActivityPub.MRF do
 
   def filter(%{} = object), do: get_policies() |> filter(object)
 
+  def id_filter(policies, id) when is_binary(id) do
+    policies
+    |> Enum.filter(&function_exported?(&1, :id_filter, 1))
+    |> Enum.all?(& &1.id_filter(id))
+  end
+
+  def id_filter(id) when is_binary(id), do: get_policies() |> id_filter(id)
+
   @impl true
   def pipeline_filter(%{} = message, meta) do
     object = meta[:object_data]

lib/pleroma/web/activity_pub/mrf/policy.ex

@@ -4,6 +4,7 @@
 
 defmodule Pleroma.Web.ActivityPub.MRF.Policy do
   @callback filter(Pleroma.Activity.t()) :: {:ok | :reject, Pleroma.Activity.t()}
+  @callback id_filter(String.t()) :: boolean()
   @callback describe() :: {:ok | :error, map()}
   @callback config_description() :: %{
               optional(:children) => [map()],
@@ -13,5 +14,5 @@ defmodule Pleroma.Web.ActivityPub.MRF.Policy do
               description: String.t()
             }
   @callback history_awareness() :: :auto | :manual
-  @optional_callbacks config_description: 0, history_awareness: 0
+  @optional_callbacks config_description: 0, history_awareness: 0, id_filter: 1
 end