Merge branch 'feature/hellthread-filter-improvements' into 'develop'

Improve hellthread filter

Closes #584

See merge request pleroma/pleroma!766

config/config.exs

@@ -227,7 +227,9 @@
   allow_followersonly: false,
   allow_direct: false
 
-config :pleroma, :mrf_hellthread, threshold: 10
+config :pleroma, :mrf_hellthread,
+  delist_threshold: 5,
+  reject_threshold: 10
 
 config :pleroma, :mrf_simple,
   media_removal: [],

docs/config.md

@@ -148,7 +148,8 @@ This section is used to configure Pleroma-FE, unless ``:managed_config`` in ``:i
 * `allow_direct`: whether to allow direct messages
 
 ## :mrf_hellthread
-* `threshold`: Number of mentioned users after which the message gets discarded as spam
+* `delist_threshold`: Number of mentioned users after which the message gets delisted (the message can still be seen, but it will not show up in public timelines and mentioned users won't get notifications about it). Set to 0 to disable.
+* `reject_threshold`: Number of mentioned users after which the messaged gets rejected. Set to 0 to disable.
 
 ## :media_proxy
 * `enabled`: Enables proxying of remote media to the instance’s proxy

lib/pleroma/config/deprecation_warnings.ex

@@ -12,6 +12,13 @@ def check_frontend_config_mechanism() do
       You are using the old configuration mechanism for the frontend. Please check config.md.
       """)
     end
+
+    if Pleroma.Config.get(:mrf_hellthread, :threshold) do
+      Logger.warn("""
+      !!!DEPRECATION WARNING!!!
+      You are using the old configuration mechanism for the hellthread filter. Please check config.md.
+      """)
+    end
   end
 
   def warn do

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

@@ -3,20 +3,46 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.ActivityPub.MRF.HellthreadPolicy do
+  alias Pleroma.User
   @behaviour Pleroma.Web.ActivityPub.MRF
 
+  defp delist_message(message) do
+    follower_collection = User.get_cached_by_ap_id(message["actor"]).follower_address
+
+    message
+    |> Map.put("to", [follower_collection])
+    |> Map.put("cc", ["https://www.w3.org/ns/activitystreams#Public"])
+  end
+
   @impl true
-  def filter(%{"type" => "Create"} = object) do
-    threshold = Pleroma.Config.get([:mrf_hellthread, :threshold])
-    recipients = (object["to"] || []) ++ (object["cc"] || [])
-
-    if length(recipients) > threshold do
-      {:reject, nil}
-    else
-      {:ok, object}
+  def filter(%{"type" => "Create"} = message) do
+    delist_threshold = Pleroma.Config.get([:mrf_hellthread, :delist_threshold])
+
+    reject_threshold =
+      Pleroma.Config.get(
+        [:mrf_hellthread, :reject_threshold],
+        Pleroma.Config.get([:mrf_hellthread, :threshold])
+      )
+
+    recipients = (message["to"] || []) ++ (message["cc"] || [])
+
+    cond do
+      length(recipients) > reject_threshold and reject_threshold > 0 ->
+        {:reject, nil}
+
+      length(recipients) > delist_threshold and delist_threshold > 0 ->
+        if Enum.member?(message["to"], "https://www.w3.org/ns/activitystreams#Public") or
+             Enum.member?(message["cc"], "https://www.w3.org/ns/activitystreams#Public") do
+          {:ok, delist_message(message)}
+        else
+          {:ok, message}
+        end
+
+      true ->
+        {:ok, message}
     end
   end
 
   @impl true
-  def filter(object), do: {:ok, object}
+  def filter(message), do: {:ok, message}
 end