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# Pleroma: A lightweight social networking server
# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Web.ActivityPub.MRF.HellthreadPolicy do
alias Pleroma.User
require Pleroma.Constants
@moduledoc "Block messages with too much mentions (configurable)"
@behaviour Pleroma.Web.ActivityPub.MRF.Policy
defp delist_message(message, threshold) when threshold > 0 do
follower_collection = User.get_cached_by_ap_id(message["actor"]).follower_address
to = message["to"] || []
cc = message["cc"] || []
follower_collection? = Enum.member?(to ++ cc, follower_collection)
message =
case get_recipient_count(message) do
{:public, recipients}
when follower_collection? and recipients > threshold ->
message
|> Map.put("to", [follower_collection])
|> Map.put("cc", [Pleroma.Constants.as_public()])
{:public, recipients} when recipients > threshold ->
message
|> Map.put("to", [])
|> Map.put("cc", [Pleroma.Constants.as_public()])
_ ->
message
end
{:ok, message}
end
defp delist_message(message, _threshold), do: {:ok, message}
defp reject_message(message, threshold) when threshold > 0 do
with {_, recipients} <- get_recipient_count(message) do
if recipients > threshold do
{:reject, "[HellthreadPolicy] #{recipients} recipients is over the limit of #{threshold}"}
else
{:ok, message}
end
end
end
defp reject_message(message, _threshold), do: {:ok, message}
defp get_recipient_count(message) do
recipients = (message["to"] || []) ++ (message["cc"] || [])
follower_collection = User.get_cached_by_ap_id(message["actor"]).follower_address
if Enum.member?(recipients, Pleroma.Constants.as_public()) do
recipients =
recipients
|> List.delete(Pleroma.Constants.as_public())
|> List.delete(follower_collection)
{:public, length(recipients)}
else
recipients =
recipients
|> List.delete(follower_collection)
{:not_public, length(recipients)}
end
end
@impl true
def filter(%{"type" => "Create", "object" => %{"type" => object_type}} = message)
when object_type in ~w{Note Article} do
reject_threshold =
Pleroma.Config.get(
[:mrf_hellthread, :reject_threshold],
Pleroma.Config.get([:mrf_hellthread, :threshold])
)
delist_threshold = Pleroma.Config.get([:mrf_hellthread, :delist_threshold])
with {:ok, message} <- reject_message(message, reject_threshold),
{:ok, message} <- delist_message(message, delist_threshold) do
{:ok, message}
else
e -> e
end
end
@impl true
def filter(message), do: {:ok, message}
@impl true
def describe,
do: {:ok, %{mrf_hellthread: Pleroma.Config.get(:mrf_hellthread) |> Enum.into(%{})}}
@impl true
def config_description do
%{
key: :mrf_hellthread,
related_policy: "Pleroma.Web.ActivityPub.MRF.HellthreadPolicy",
label: "MRF Hellthread",
description: "Block messages with excessive user mentions",
children: [
%{
key: :delist_threshold,
type: :integer,
description:
"Number of mentioned users after which the message gets removed from timelines and" <>
"disables notifications. Set to 0 to disable.",
suggestions: [10]
},
%{
key: :reject_threshold,
type: :integer,
description:
"Number of mentioned users after which the messaged gets rejected. Set to 0 to disable.",
suggestions: [20]
}
]
}
end
end
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