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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
   3 # SPDX-License-Identifier: AGPL-3.0-only
   4
   5 defmodule Pleroma.Web.ActivityPub.MRF.ObjectAgePolicy do
   6   alias Pleroma.Config
   7   alias Pleroma.User
   8
   9   require Pleroma.Constants
  10
  11   @moduledoc "Filter activities depending on their age"
  12   @behaviour Pleroma.Web.ActivityPub.MRF
  13
  14   defp check_date(%{"object" => %{"published" => published}} = message) do
  15     with %DateTime{} = now <- DateTime.utc_now(),
  16          {:ok, %DateTime{} = then, _} <- DateTime.from_iso8601(published),
  17          max_ttl <- Config.get([:mrf_object_age, :threshold]),
  18          {:ttl, false} <- {:ttl, DateTime.diff(now, then) > max_ttl} do
  19       {:ok, message}
  20     else
  21       {:ttl, true} ->
  22         {:reject, nil}
  23
  24       e ->
  25         {:error, e}
  26     end
  27   end
  28
  29   defp check_reject(message, actions) do
  30     if :reject in actions do
  31       {:reject, "[ObjectAgePolicy]"}
  32     else
  33       {:ok, message}
  34     end
  35   end
  36
  37   defp check_delist(message, actions) do
  38     if :delist in actions do
  39       with %User{} = user <- User.get_cached_by_ap_id(message["actor"]) do
  40         to = List.delete(message["to"], Pleroma.Constants.as_public()) ++ [user.follower_address]
  41         cc = List.delete(message["cc"], user.follower_address) ++ [Pleroma.Constants.as_public()]
  42
  43         message =
  44           message
  45           |> Map.put("to", to)
  46           |> Map.put("cc", cc)
  47
  48         {:ok, message}
  49       else
  50         _e ->
  51           {:reject, "[ObjectAgePolicy] Unhandled error"}
  52       end
  53     else
  54       {:ok, message}
  55     end
  56   end
  57
  58   defp check_strip_followers(message, actions) do
  59     if :strip_followers in actions do
  60       with %User{} = user <- User.get_cached_by_ap_id(message["actor"]) do
  61         to = List.delete(message["to"], user.follower_address)
  62         cc = List.delete(message["cc"], user.follower_address)
  63
  64         message =
  65           message
  66           |> Map.put("to", to)
  67           |> Map.put("cc", cc)
  68
  69         {:ok, message}
  70       else
  71         _e ->
  72           {:reject, "[ObjectAgePolicy] Unhandled error"}
  73       end
  74     else
  75       {:ok, message}
  76     end
  77   end
  78
  79   @impl true
  80   def filter(%{"type" => "Create", "published" => _} = message) do
  81     with actions <- Config.get([:mrf_object_age, :actions]),
  82          {:reject, _} <- check_date(message),
  83          {:ok, message} <- check_reject(message, actions),
  84          {:ok, message} <- check_delist(message, actions),
  85          {:ok, message} <- check_strip_followers(message, actions) do
  86       {:ok, message}
  87     else
  88       # check_date() is allowed to short-circuit the pipeline
  89       e -> e
  90     end
  91   end
  92
  93   @impl true
  94   def filter(message), do: {:ok, message}
  95
  96   @impl true
  97   def describe do
  98     mrf_object_age =
  99       Config.get(:mrf_object_age)
 100       |> Enum.into(%{})
 101
 102     {:ok, %{mrf_object_age: mrf_object_age}}
 103   end
 104 end