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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.KeywordPolicy do
   6   @behaviour Pleroma.Web.ActivityPub.MRF
   7   defp string_matches?(string, pattern) when is_binary(pattern) do
   8     String.contains?(string, pattern)
   9   end
  10
  11   defp string_matches?(string, pattern) do
  12     String.match?(string, pattern)
  13   end
  14
  15   defp check_reject(%{"object" => %{"content" => content, "summary" => summary}} = message) do
  16     if Enum.any?(Pleroma.Config.get([:mrf_keyword, :reject]), fn pattern ->
  17          string_matches?(content, pattern) or string_matches?(summary, pattern)
  18        end) do
  19       {:reject, nil}
  20     else
  21       {:ok, message}
  22     end
  23   end
  24
  25   defp check_ftl_removal(
  26          %{"to" => to, "object" => %{"content" => content, "summary" => summary}} = message
  27        ) do
  28     if "https://www.w3.org/ns/activitystreams#Public" in to and
  29          Enum.any?(Pleroma.Config.get([:mrf_keyword, :federated_timeline_removal]), fn pattern ->
  30            string_matches?(content, pattern) or string_matches?(summary, pattern)
  31          end) do
  32       to = List.delete(to, "https://www.w3.org/ns/activitystreams#Public")
  33       cc = ["https://www.w3.org/ns/activitystreams#Public" | message["cc"] || []]
  34
  35       message =
  36         message
  37         |> Map.put("to", to)
  38         |> Map.put("cc", cc)
  39
  40       {:ok, message}
  41     else
  42       {:ok, message}
  43     end
  44   end
  45
  46   defp check_replace(%{"object" => %{"content" => content, "summary" => summary}} = message) do
  47     {content, summary} =
  48       Enum.reduce(
  49         Pleroma.Config.get([:mrf_keyword, :replace]),
  50         {content, summary},
  51         fn {pattern, replacement}, {content_acc, summary_acc} ->
  52           {String.replace(content_acc, pattern, replacement),
  53            String.replace(summary_acc, pattern, replacement)}
  54         end
  55       )
  56
  57     {:ok,
  58      message
  59      |> put_in(["object", "content"], content)
  60      |> put_in(["object", "summary"], summary)}
  61   end
  62
  63   @impl true
  64   def filter(%{"object" => %{"content" => nil}} = message) do
  65     {:ok, message}
  66   end
  67
  68   @impl true
  69   def filter(%{"type" => "Create", "object" => %{"content" => _content}} = message) do
  70     with {:ok, message} <- check_reject(message),
  71          {:ok, message} <- check_ftl_removal(message),
  72          {:ok, message} <- check_replace(message) do
  73       {:ok, message}
  74     else
  75       _e ->
  76         {:reject, nil}
  77     end
  78   end
  79
  80   @impl true
  81   def filter(message), do: {:ok, message}
  82 end