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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
   3 # SPDX-License-Identifier: AGPL-3.0-only
   4
   5 defmodule Pleroma.Web.ActivityPub.MRF.HellthreadPolicy do
   6   alias Pleroma.User
   7   @behaviour Pleroma.Web.ActivityPub.MRF
   8
   9   defp delist_message(message) do
  10     delist_threshold = Pleroma.Config.get([:mrf_hellthread, :delist_threshold])
  11     follower_collection = User.get_cached_by_ap_id(message["actor"]).follower_address
  12
  13     follower_collection? = Enum.member?(message["to"] ++ message["cc"], follower_collection)
  14
  15     message =
  16       case recipients = get_recipient_count(message) do
  17         {:public, _} when follower_collection? and recipients > delist_threshold ->
  18           message
  19           |> Map.put("to", [follower_collection])
  20           |> Map.put("cc", ["https://www.w3.org/ns/activitystreams#Public"])
  21
  22         {:public, _} when recipients > delist_threshold ->
  23           message
  24           |> Map.put("to", [])
  25           |> Map.put("cc", ["https://www.w3.org/ns/activitystreams#Public"])
  26
  27         _ ->
  28           message
  29       end
  30
  31     {:ok, message}
  32   end
  33
  34   defp reject_message(message) do
  35     reject_threshold =
  36       Pleroma.Config.get(
  37         [:mrf_hellthread, :reject_threshold],
  38         Pleroma.Config.get([:mrf_hellthread, :threshold])
  39       )
  40
  41     with {_, recipients} <- get_recipient_count(message) do
  42       if recipients > reject_threshold and reject_threshold > 0 do
  43         {:reject, nil}
  44       else
  45         {:ok, message}
  46       end
  47     end
  48   end
  49
  50   defp get_recipient_count(message) do
  51     recipients = (message["to"] || []) ++ (message["cc"] || [])
  52     follower_collection = User.get_cached_by_ap_id(message["actor"]).follower_address
  53
  54     if Enum.member?(recipients, "https://www.w3.org/ns/activitystreams#Public") do
  55       recipients =
  56         recipients
  57         |> List.delete("https://www.w3.org/ns/activitystreams#Public")
  58         |> List.delete(follower_collection)
  59
  60       {:public, length(recipients)}
  61     else
  62       recipients =
  63         recipients
  64         |> List.delete(follower_collection)
  65
  66       {:not_public, length(recipients)}
  67     end
  68   end
  69
  70   @impl true
  71   def filter(%{"type" => "Create"} = message) do
  72     with {:ok, message} <- reject_message(message),
  73          {:ok, message} <- delist_message(message) do
  74       {:ok, message}
  75     else
  76       _e -> {:reject, nil}
  77     end
  78   end
  79
  80   @impl true
  81   def filter(message), do: {:ok, message}
  82 end