From 54ec6d09b012e90cd42c00e218df4cc7b99410a4 Mon Sep 17 00:00:00 2001
From: William Pitcock <nenolod@dereferenced.org>
Date: Thu, 24 Jan 2019 09:35:19 +0000
Subject: [PATCH 1/2] mrf: add anti-followbot policy

---
 .../activity_pub/mrf/anti_followbot_policy.ex | 57 +++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 lib/pleroma/web/activity_pub/mrf/anti_followbot_policy.ex

diff --git a/lib/pleroma/web/activity_pub/mrf/anti_followbot_policy.ex b/lib/pleroma/web/activity_pub/mrf/anti_followbot_policy.ex
new file mode 100644
index 000000000..7c6ad582a
--- /dev/null
+++ b/lib/pleroma/web/activity_pub/mrf/anti_followbot_policy.ex
@@ -0,0 +1,57 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.AntiFollowbotPolicy do
+  alias Pleroma.User
+
+  @behaviour Pleroma.Web.ActivityPub.MRF
+
+  # XXX: this should become User.normalize_by_ap_id() or similar, really.
+  defp normalize_by_ap_id(%{"id" => id}), do: User.get_cached_by_ap_id(id)
+  defp normalize_by_ap_id(uri) when is_binary(uri), do: User.get_cached_by_ap_id(uri)
+  defp normalize_by_ap_id(_), do: nil
+
+  defp score_nickname("followbot@" <> _), do: 1.0
+  defp score_nickname("federationbot@" <> _), do: 1.0
+  defp score_nickname("federation_bot@" <> _), do: 1.0
+  defp score_nickname(_), do: 0.0
+
+  defp score_displayname("federation bot"), do: 1.0
+  defp score_displayname("federationbot"), do: 1.0
+  defp score_displayname("fedibot"), do: 1.0
+  defp score_displayname(_), do: 0.0
+
+  defp determine_if_followbot(%User{nickname: nickname, name: displayname}) do
+    nick_score =
+      nickname
+      |> String.downcase()
+      |> score_nickname()
+
+    name_score =
+      displayname
+      |> String.downcase()
+      |> score_displayname()
+
+    nick_score + name_score
+  end
+
+  defp determine_if_followbot(_), do: 0.0
+
+  @impl true
+  def filter(%{"type" => "Follow", "actor" => actor_id} = message) do
+    %User{} = actor = normalize_by_ap_id(actor_id)
+
+    score = determine_if_followbot(actor)
+
+    # TODO: scan biography data for keywords and score it somehow.
+    if score < 0.8 do
+      {:ok, message}
+    else
+      {:reject, nil}
+    end
+  end
+
+  @impl true
+  def filter(message), do: {:ok, message}
+end

From 13d72826dfe3eab3b08f58800c63effb1e3cdfd6 Mon Sep 17 00:00:00 2001
From: William Pitcock <nenolod@dereferenced.org>
Date: Thu, 24 Jan 2019 09:50:40 +0000
Subject: [PATCH 2/2] test: add anti-followbot policy tests

---
 .../mrf/anti_followbot_policy_test.exs        | 57 +++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 test/web/activity_pub/mrf/anti_followbot_policy_test.exs

diff --git a/test/web/activity_pub/mrf/anti_followbot_policy_test.exs b/test/web/activity_pub/mrf/anti_followbot_policy_test.exs
new file mode 100644
index 000000000..2ea4f9d3f
--- /dev/null
+++ b/test/web/activity_pub/mrf/anti_followbot_policy_test.exs
@@ -0,0 +1,57 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.AntiFollowbotPolicyTest do
+  use Pleroma.DataCase
+  import Pleroma.Factory
+
+  alias Pleroma.Web.ActivityPub.MRF.AntiFollowbotPolicy
+
+  describe "blocking based on attributes" do
+    test "matches followbots by nickname" do
+      actor = insert(:user, %{nickname: "followbot@example.com"})
+      target = insert(:user)
+
+      message = %{
+        "@context" => "https://www.w3.org/ns/activitystreams",
+        "type" => "Follow",
+        "actor" => actor.ap_id,
+        "object" => target.ap_id,
+        "id" => "https://example.com/activities/1234"
+      }
+
+      {:reject, nil} = AntiFollowbotPolicy.filter(message)
+    end
+
+    test "matches followbots by display name" do
+      actor = insert(:user, %{name: "Federation Bot"})
+      target = insert(:user)
+
+      message = %{
+        "@context" => "https://www.w3.org/ns/activitystreams",
+        "type" => "Follow",
+        "actor" => actor.ap_id,
+        "object" => target.ap_id,
+        "id" => "https://example.com/activities/1234"
+      }
+
+      {:reject, nil} = AntiFollowbotPolicy.filter(message)
+    end
+  end
+
+  test "it allows non-followbots" do
+    actor = insert(:user)
+    target = insert(:user)
+
+    message = %{
+      "@context" => "https://www.w3.org/ns/activitystreams",
+      "type" => "Follow",
+      "actor" => actor.ap_id,
+      "object" => target.ap_id,
+      "id" => "https://example.com/activities/1234"
+    }
+
+    {:ok, _} = AntiFollowbotPolicy.filter(message)
+  end
+end