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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}} = message) do
  16     if Enum.any?(Pleroma.Config.get([:mrf_keyword, :reject]), fn pattern ->
  17          string_matches?(content, pattern)
  18        end) do
  19       {:reject, nil}
  20     else
  21       {:ok, message}
  22     end
  23   end
  24
  25   defp check_ftl_removal(%{"to" => to, "object" => %{"content" => content}} = message) do
  26     if "https://www.w3.org/ns/activitystreams#Public" in to and
  27          Enum.any?(Pleroma.Config.get([:mrf_keyword, :federated_timeline_removal]), fn pattern ->
  28            string_matches?(content, pattern)
  29          end) do
  30       to = List.delete(to, "https://www.w3.org/ns/activitystreams#Public")
  31       cc = ["https://www.w3.org/ns/activitystreams#Public" | message["cc"] || []]
  32
  33       message =
  34         message
  35         |> Map.put("to", to)
  36         |> Map.put("cc", cc)
  37
  38       {:ok, message}
  39     else
  40       {:ok, message}
  41     end
  42   end
  43
  44   defp check_replace(%{"object" => %{"content" => content}} = message) do
  45     content =
  46       Enum.reduce(Pleroma.Config.get([:mrf_keyword, :replace]), content, fn {pattern, replacement},
  47                                                                             acc ->
  48         String.replace(acc, pattern, replacement)
  49       end)
  50
  51     {:ok, put_in(message["object"]["content"], content)}
  52   end
  53
  54   @impl true
  55   def filter(%{"object" => %{"content" => nil}} = message) do
  56     {:ok, message}
  57   end
  58
  59   @impl true
  60   def filter(%{"type" => "Create", "object" => %{"content" => _content}} = message) do
  61     with {:ok, message} <- check_reject(message),
  62          {:ok, message} <- check_ftl_removal(message),
  63          {:ok, message} <- check_replace(message) do
  64       {:ok, message}
  65     else
  66       _e ->
  67         {:reject, nil}
  68     end
  69   end
  70
  71   @impl true
  72   def filter(message), do: {:ok, message}
  73 end