diff --git a/CHANGELOG.md b/CHANGELOG.md
index c5632f273..0d91ad817 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
### Added
- MRF: Support for priming the mediaproxy cache (`Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicy`)
- MRF: Support for excluding specific domains from Transparency.
+- MRF: Support for filtering posts based on who they mention (`Pleroma.Web.ActivityPub.MRF.MentionPolicy`)
- Configuration: `federation_incoming_replies_max_depth` option
- Mastodon API: Support for the [`tagged` filter](https://github.com/tootsuite/mastodon/pull/9755) in [`GET /api/v1/accounts/:id/statuses`](https://docs.joinmastodon.org/api/rest/accounts/#get-api-v1-accounts-id-statuses)
- Mastodon API, streaming: Add support for passing the token in the `Sec-WebSocket-Protocol` header
diff --git a/docs/config.md b/docs/config.md
index 346b8cda2..42556a0be 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -101,6 +101,7 @@ config :pleroma, Pleroma.Emails.Mailer,
* `Pleroma.Web.ActivityPub.MRF.EnsureRePrepended`: Rewrites posts to ensure that replies to posts with subjects do not have an identical subject and instead begin with re:.
* `Pleroma.Web.ActivityPub.MRF.AntiLinkSpamPolicy`: Rejects posts from likely spambots by rejecting posts from new users that contain links.
* `Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicy`: Crawls attachments using their MediaProxy URLs so that the MediaProxy cache is primed.
+ * `Pleroma.Web.ActivityPub.MRF.MentionPolicy`: Drops posts mentioning configurable users. (see `:mrf_mention` section)
* `public`: Makes the client API in authentificated mode-only except for user-profiles. Useful for disabling the Local Timeline and The Whole Known Network.
* `quarantined_instances`: List of ActivityPub instances where private(DMs, followers-only) activities will not be send.
* `managed_config`: Whenether the config for pleroma-fe is configured in this config or in ``static/config.json``
@@ -271,6 +272,9 @@ config :pleroma, :mrf_subchain,
* `federated_timeline_removal`: A list of patterns which result in message being removed from federated timelines (a.k.a unlisted), each pattern can be a string or a [regular expression](https://hexdocs.pm/elixir/Regex.html)
* `replace`: A list of tuples containing `{pattern, replacement}`, `pattern` can be a string or a [regular expression](https://hexdocs.pm/elixir/Regex.html)
+## :mrf_mention
+* `actors`: A list of actors, for which to drop any posts mentioning.
+
## :media_proxy
* `enabled`: Enables proxying of remote media to the instance’s proxy
* `base_url`: The base URL to access a user-uploaded file. Useful when you want to proxy the media files via another host/CDN fronts.
diff --git a/lib/pleroma/web/activity_pub/mrf/mention_policy.ex b/lib/pleroma/web/activity_pub/mrf/mention_policy.ex
new file mode 100644
index 000000000..1842e1aeb
--- /dev/null
+++ b/lib/pleroma/web/activity_pub/mrf/mention_policy.ex
@@ -0,0 +1,24 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.MentionPolicy do
+ @moduledoc "Block messages which mention a user"
+
+ @behaviour Pleroma.Web.ActivityPub.MRF
+
+ @impl true
+ def filter(%{"type" => "Create"} = message) do
+ reject_actors = Pleroma.Config.get([:mrf_mention, :actors], [])
+ recipients = (message["to"] || []) ++ (message["cc"] || [])
+
+ if Enum.any?(recipients, fn recipient -> Enum.member?(reject_actors, recipient) end) do
+ {:reject, nil}
+ else
+ {:ok, message}
+ end
+ end
+
+ @impl true
+ def filter(message), do: {:ok, message}
+end
diff --git a/test/web/activity_pub/mrf/mention_policy_test.exs b/test/web/activity_pub/mrf/mention_policy_test.exs
new file mode 100644
index 000000000..9fd9c31df
--- /dev/null
+++ b/test/web/activity_pub/mrf/mention_policy_test.exs
@@ -0,0 +1,92 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.MentionPolicyTest do
+ use Pleroma.DataCase
+
+ alias Pleroma.Web.ActivityPub.MRF.MentionPolicy
+
+ test "pass filter if allow list is empty" do
+ Pleroma.Config.delete([:mrf_mention])
+
+ message = %{
+ "type" => "Create",
+ "to" => ["https://example.com/ok"],
+ "cc" => ["https://example.com/blocked"]
+ }
+
+ assert MentionPolicy.filter(message) == {:ok, message}
+ end
+
+ describe "allow" do
+ test "empty" do
+ Pleroma.Config.put([:mrf_mention], %{actors: ["https://example.com/blocked"]})
+
+ message = %{
+ "type" => "Create"
+ }
+
+ assert MentionPolicy.filter(message) == {:ok, message}
+ end
+
+ test "to" do
+ Pleroma.Config.put([:mrf_mention], %{actors: ["https://example.com/blocked"]})
+
+ message = %{
+ "type" => "Create",
+ "to" => ["https://example.com/ok"]
+ }
+
+ assert MentionPolicy.filter(message) == {:ok, message}
+ end
+
+ test "cc" do
+ Pleroma.Config.put([:mrf_mention], %{actors: ["https://example.com/blocked"]})
+
+ message = %{
+ "type" => "Create",
+ "cc" => ["https://example.com/ok"]
+ }
+
+ assert MentionPolicy.filter(message) == {:ok, message}
+ end
+
+ test "both" do
+ Pleroma.Config.put([:mrf_mention], %{actors: ["https://example.com/blocked"]})
+
+ message = %{
+ "type" => "Create",
+ "to" => ["https://example.com/ok"],
+ "cc" => ["https://example.com/ok2"]
+ }
+
+ assert MentionPolicy.filter(message) == {:ok, message}
+ end
+ end
+
+ describe "deny" do
+ test "to" do
+ Pleroma.Config.put([:mrf_mention], %{actors: ["https://example.com/blocked"]})
+
+ message = %{
+ "type" => "Create",
+ "to" => ["https://example.com/blocked"]
+ }
+
+ assert MentionPolicy.filter(message) == {:reject, nil}
+ end
+
+ test "cc" do
+ Pleroma.Config.put([:mrf_mention], %{actors: ["https://example.com/blocked"]})
+
+ message = %{
+ "type" => "Create",
+ "to" => ["https://example.com/ok"],
+ "cc" => ["https://example.com/blocked"]
+ }
+
+ assert MentionPolicy.filter(message) == {:reject, nil}
+ end
+ end
+end