From 0bddca361d12f347ca9907c5ddb5d1464a17b32a Mon Sep 17 00:00:00 2001 From: Mark Felder Date: Sun, 24 Jan 2021 14:56:45 -0600 Subject: [PATCH] DNSRBL in an MRF --- changelog.d/add-rbl-mrf.add | 1 + config/config.exs | 5 + .../web/activity_pub/mrf/dnsrbl_policy.ex | 142 ++++++++++++++++++ 3 files changed, 148 insertions(+) create mode 100644 changelog.d/add-rbl-mrf.add create mode 100644 lib/pleroma/web/activity_pub/mrf/dnsrbl_policy.ex diff --git a/changelog.d/add-rbl-mrf.add b/changelog.d/add-rbl-mrf.add new file mode 100644 index 000000000..363270fb9 --- /dev/null +++ b/changelog.d/add-rbl-mrf.add @@ -0,0 +1 @@ +Add DNSRBL MRF diff --git a/config/config.exs b/config/config.exs index b93de52e1..1fb0f3911 100644 --- a/config/config.exs +++ b/config/config.exs @@ -410,6 +410,11 @@ accept: [], reject: [] +config :pleroma, :mrf_dnsrbl, + nameserver: "127.0.0.1", + port: 53, + zone: "bl.pleroma.com" + # threshold of 7 days config :pleroma, :mrf_object_age, threshold: 604_800, diff --git a/lib/pleroma/web/activity_pub/mrf/dnsrbl_policy.ex b/lib/pleroma/web/activity_pub/mrf/dnsrbl_policy.ex new file mode 100644 index 000000000..9543cc545 --- /dev/null +++ b/lib/pleroma/web/activity_pub/mrf/dnsrbl_policy.ex @@ -0,0 +1,142 @@ +# Pleroma: A lightweight social networking server +# Copyright © 2017-2024 Pleroma Authors +# SPDX-License-Identifier: AGPL-3.0-only + +defmodule Pleroma.Web.ActivityPub.MRF.DNSRBLPolicy do + @moduledoc """ + Dynamic activity filtering based on an RBL database + + This MRF makes queries to a custom DNS server which will + respond with values indicating the classification of the domain + the activity originated from. This method has been widely used + in the email anti-spam industry for very fast reputation checks. + + e.g., if the DNS response is 127.0.0.1 or empty, the domain is OK + Other values such as 127.0.0.2 may be used for specific classifications. + + Information for why the host is blocked can be stored in a corresponding TXT record. + + This method is fail-open so if the queries fail the activites are accepted. + + An example of software meant for this purpsoe is rbldnsd which can be found + at http://www.corpit.ru/mjt/rbldnsd.html or mirrored at + https://git.pleroma.social/feld/rbldnsd + + It is highly recommended that you run your own copy of rbldnsd and use an + external mechanism to sync/share the contents of the zone file. This is + important to keep the latency on the queries as low as possible and prevent + your DNS server from being attacked so it fails and content is permitted. + """ + + @behaviour Pleroma.Web.ActivityPub.MRF.Policy + + alias Pleroma.Config + + require Logger + + @query_retries 1 + @query_timeout 500 + + @impl true + def filter(%{"actor" => actor} = object) do + actor_info = URI.parse(actor) + + with {:ok, object} <- check_rbl(actor_info, object) do + {:ok, object} + else + _ -> {:reject, "[DNSRBLPolicy]"} + end + end + + @impl true + def filter(object), do: {:ok, object} + + @impl true + def describe do + mrf_dnsrbl = + Config.get(:mrf_dnsrbl) + |> Enum.into(%{}) + + {:ok, %{mrf_dnsrbl: mrf_dnsrbl}} + end + + @impl true + def config_description do + %{ + key: :mrf_dnsrbl, + related_policy: "Pleroma.Web.ActivityPub.MRF.DNSRBLPolicy", + label: "MRF DNSRBL", + description: "DNS RealTime Blackhole Policy", + children: [ + %{ + key: :nameserver, + type: {:string}, + description: "DNSRBL Nameserver to Query (IP or hostame)", + suggestions: ["127.0.0.1"] + }, + %{ + key: :port, + type: {:string}, + description: "Nameserver port", + suggestions: ["53"] + }, + %{ + key: :zone, + type: {:string}, + description: "Root zone for querying", + suggestions: ["bl.pleroma.com"] + } + ] + } + end + + defp check_rbl(%{host: actor_host}, object) do + with false <- match?(^actor_host, Pleroma.Web.Endpoint.host()), + zone when not is_nil(zone) <- Keyword.get(Config.get([:mrf_dnsrbl]), :zone) do + query = + Enum.join([actor_host, zone], ".") + |> String.to_charlist() + + rbl_response = rblquery(query) + + if Enum.empty?(rbl_response) do + {:ok, object} + else + Task.start(fn -> + reason = rblquery(query, :txt) || "undefined" + + Logger.warning( + "DNSRBL Rejected activity from #{actor_host} for reason: #{inspect(reason)}" + ) + end) + + :error + end + else + _ -> {:ok, object} + end + end + + defp get_rblhost_ip(rblhost) do + case rblhost |> String.to_charlist() |> :inet_parse.address() do + {:ok, _} -> rblhost |> String.to_charlist() |> :inet_parse.address() + _ -> {:ok, rblhost |> String.to_charlist() |> :inet_res.lookup(:in, :a) |> Enum.random()} + end + end + + defp rblquery(query, type \\ :a) do + config = Config.get([:mrf_dnsrbl]) + + case get_rblhost_ip(config[:nameserver]) do + {:ok, rblnsip} -> + :inet_res.lookup(query, :in, type, + nameservers: [{rblnsip, config[:port]}], + timeout: @query_timeout, + retry: @query_retries + ) + + _ -> + [] + end + end +end