1 files changed, 97 insertions, 0 deletions
diff --git a/lib/pleroma/web/activity_pub/mrf/steal_emoji_policy.ex b/lib/pleroma/web/activity_pub/mrf/steal_emoji_policy.ex
new file mode 100644
index 000000000..2858af9eb
--- /dev/null
+++ b/lib/pleroma/web/activity_pub/mrf/steal_emoji_policy.ex
@@ -0,0 +1,97 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.StealEmojiPolicy do
+  require Logger
+
+  alias Pleroma.Config
+
+  @moduledoc "Detect new emojis by their shortcode and steals them"
+  @behaviour Pleroma.Web.ActivityPub.MRF
+
+  defp remote_host?(host), do: host != Config.get([Pleroma.Web.Endpoint, :url, :host])
+
+  defp accept_host?(host), do: host in Config.get([:mrf_steal_emoji, :hosts], [])
+
+  defp steal_emoji({shortcode, url}) do
+    url = Pleroma.Web.MediaProxy.url(url)
+    {:ok, response} = Pleroma.HTTP.get(url)
+    size_limit = Config.get([:mrf_steal_emoji, :size_limit], 50_000)
+
+    if byte_size(response.body) <= size_limit do
+      emoji_dir_path =
+        Config.get(
+          [:mrf_steal_emoji, :path],
+          Path.join(Config.get([:instance, :static_dir]), "emoji/stolen")
+        )
+
+      extension =
+        url
+        |> URI.parse()
+        |> Map.get(:path)
+        |> Path.basename()
+        |> Path.extname()
+
+      file_path = Path.join([emoji_dir_path, shortcode <> (extension || ".png")])
+
+      try do
+        :ok = File.write(file_path, response.body)
+
+        shortcode
+      rescue
+        e ->
+          Logger.warn("MRF.StealEmojiPolicy: Failed to write to #{file_path}: #{inspect(e)}")
+          nil
+      end
+    else
+      Logger.debug(
+        "MRF.StealEmojiPolicy: :#{shortcode}: at #{url} (#{byte_size(response.body)} B) over size limit (#{
+          size_limit
+        } B)"
+      )
+
+      nil
+    end
+  rescue
+    e ->
+      Logger.warn("MRF.StealEmojiPolicy: Failed to fetch #{url}: #{inspect(e)}")
+      nil
+  end
+
+  @impl true
+  def filter(%{"object" => %{"emoji" => foreign_emojis, "actor" => actor}} = message) do
+    host = URI.parse(actor).host
+
+    if remote_host?(host) and accept_host?(host) do
+      installed_emoji = Pleroma.Emoji.get_all() |> Enum.map(fn {k, _} -> k end)
+
+      new_emojis =
+        foreign_emojis
+        |> Enum.filter(fn {shortcode, _url} -> shortcode not in installed_emoji end)
+        |> Enum.filter(fn {shortcode, _url} ->
+          reject_emoji? =
+            Config.get([:mrf_steal_emoji, :rejected_shortcodes], [])
+            |> Enum.find(false, fn regex -> String.match?(shortcode, regex) end)
+
+          !reject_emoji?
+        end)
+        |> Enum.map(&steal_emoji(&1))
+        |> Enum.filter(& &1)
+
+      if !Enum.empty?(new_emojis) do
+        Logger.info("Stole new emojis: #{inspect(new_emojis)}")
+        Pleroma.Emoji.reload()
+      end
+    end
+
+    {:ok, message}
+  end
+
+  def filter(message), do: {:ok, message}
+
+  @impl true
+  def describe do
+    {:ok, %{}}
+  end
+end