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# Pleroma: A lightweight social networking server
# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Web.ActivityPub.MRF.KeywordPolicy do
require Pleroma.Constants
@moduledoc "Reject or Word-Replace messages with a keyword or regex"
@behaviour Pleroma.Web.ActivityPub.MRF.Policy
defp string_matches?(string, _) when not is_binary(string) do
false
end
defp string_matches?(string, pattern) when is_binary(pattern) do
String.contains?(string, pattern)
end
defp string_matches?(string, pattern) do
String.match?(string, pattern)
end
defp object_payload(%{} = object) do
[object["content"], object["summary"], object["name"]]
|> Enum.filter(& &1)
|> Enum.join("\n")
end
defp check_reject(%{"object" => %{} = object} = message) do
with {:ok, _new_object} <-
Pleroma.Object.Updater.do_with_history(object, fn object ->
payload = object_payload(object)
if Enum.any?(Pleroma.Config.get([:mrf_keyword, :reject]), fn pattern ->
string_matches?(payload, pattern)
end) do
{:reject, "[KeywordPolicy] Matches with rejected keyword"}
else
{:ok, message}
end
end) do
{:ok, message}
else
e -> e
end
end
defp check_ftl_removal(%{"type" => "Create", "to" => to, "object" => %{} = object} = message) do
check_keyword = fn object ->
payload = object_payload(object)
if Enum.any?(Pleroma.Config.get([:mrf_keyword, :federated_timeline_removal]), fn pattern ->
string_matches?(payload, pattern)
end) do
{:should_delist, nil}
else
{:ok, %{}}
end
end
should_delist? = fn object ->
with {:ok, _} <- Pleroma.Object.Updater.do_with_history(object, check_keyword) do
false
else
_ -> true
end
end
if Pleroma.Constants.as_public() in to and should_delist?.(object) do
to = List.delete(to, Pleroma.Constants.as_public())
cc = [Pleroma.Constants.as_public() | message["cc"] || []]
message =
message
|> Map.put("to", to)
|> Map.put("cc", cc)
{:ok, message}
else
{:ok, message}
end
end
defp check_ftl_removal(message) do
{:ok, message}
end
defp check_replace(%{"object" => %{} = object} = message) do
replace_kw = fn object ->
["content", "name", "summary"]
|> Enum.filter(fn field -> Map.has_key?(object, field) && object[field] end)
|> Enum.reduce(object, fn field, object ->
data =
Enum.reduce(
Pleroma.Config.get([:mrf_keyword, :replace]),
object[field],
fn {pat, repl}, acc -> String.replace(acc, pat, repl) end
)
Map.put(object, field, data)
end)
|> (fn object -> {:ok, object} end).()
end
{:ok, object} = Pleroma.Object.Updater.do_with_history(object, replace_kw)
message = Map.put(message, "object", object)
{:ok, message}
end
@impl true
def filter(%{"type" => type, "object" => %{"content" => _content}} = message)
when type in ["Create", "Update"] do
with {:ok, message} <- check_reject(message),
{:ok, message} <- check_ftl_removal(message),
{:ok, message} <- check_replace(message) do
{:ok, message}
else
{:reject, nil} -> {:reject, "[KeywordPolicy] "}
{:reject, _} = e -> e
_e -> {:reject, "[KeywordPolicy] "}
end
end
@impl true
def filter(message), do: {:ok, message}
@impl true
def describe do
# This horror is needed to convert regex sigils to strings
mrf_keyword =
Pleroma.Config.get(:mrf_keyword, [])
|> Enum.map(fn {key, value} ->
{key,
Enum.map(value, fn
{pattern, replacement} ->
%{
"pattern" =>
if not is_binary(pattern) do
inspect(pattern)
else
pattern
end,
"replacement" => replacement
}
pattern ->
if not is_binary(pattern) do
inspect(pattern)
else
pattern
end
end)}
end)
|> Enum.into(%{})
{:ok, %{mrf_keyword: mrf_keyword}}
end
@impl true
def config_description do
%{
key: :mrf_keyword,
related_policy: "Pleroma.Web.ActivityPub.MRF.KeywordPolicy",
label: "MRF Keyword",
description:
"Reject or Word-Replace messages matching a keyword or [Regex](https://hexdocs.pm/elixir/Regex.html).",
children: [
%{
key: :reject,
type: {:list, :string},
description: """
A list of patterns which result in message being rejected.
Each pattern can be a string or [Regex](https://hexdocs.pm/elixir/Regex.html) in the format of `~r/PATTERN/`.
""",
suggestions: ["foo", ~r/foo/iu]
},
%{
key: :federated_timeline_removal,
type: {:list, :string},
description: """
A list of patterns which result in message being removed from federated timelines (a.k.a unlisted).
Each pattern can be a string or [Regex](https://hexdocs.pm/elixir/Regex.html) in the format of `~r/PATTERN/`.
""",
suggestions: ["foo", ~r/foo/iu]
},
%{
key: :replace,
type: {:list, :tuple},
key_placeholder: "instance",
value_placeholder: "reason",
description: """
**Pattern**: a string or [Regex](https://hexdocs.pm/elixir/Regex.html) in the format of `~r/PATTERN/`.
**Replacement**: a string. Leaving the field empty is permitted.
"""
}
]
}
end
end
|
