Add emoji policy to remove emojis matching certain urls

https://git.pleroma.social/pleroma/pleroma/-/issues/2775

config/config.exs

@@ -408,6 +408,12 @@ config :pleroma, :mrf_keyword,
   federated_timeline_removal: [],
   replace: []
 
+config :pleroma, :mrf_emoji,
+  remove_url: [],
+  remove_shortcode: [],
+  federated_timeline_removal_url: [],
+  federated_timeline_removal_shortcode: []
+
 config :pleroma, :mrf_hashtag,
   sensitive: ["nsfw"],
   reject: [],

lib/pleroma/web/activity_pub/emoji_policy.ex

@@ -0,0 +1,158 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2023 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.EmojiPolicy do
+  require Pleroma.Constants
+
+  @moduledoc "Reject or force-unlisted emojis with certain URLs or names"
+
+  @behaviour Pleroma.Web.ActivityPub.MRF.Policy
+
+  defp config_remove_url do
+    Pleroma.Config.get([:mrf_emoji, :remove_url], [])
+  end
+
+  @impl Pleroma.Web.ActivityPub.MRF.Policy
+  def filter(%{"type" => type, "object" => %{} = object} = message)
+      when type in ["Create", "Update"] do
+    with object <- process_remove(object, :url, config_remove_url()) do
+      {:ok, Map.put(message, "object", object)}
+    end
+  end
+
+  @impl Pleroma.Web.ActivityPub.MRF.Policy
+  def filter(%{"type" => type} = object) when type in Pleroma.Constants.actor_types() do
+    with object <- process_remove(object, :url, config_remove_url()) do
+      {:ok, object}
+    end
+  end
+
+  @impl Pleroma.Web.ActivityPub.MRF.Policy
+  def filter(message) do
+    {:ok, message}
+  end
+
+  defp match_string?(string, pattern) when is_binary(pattern) do
+    string == pattern
+  end
+
+  defp match_string?(string, %Regex{} = pattern) do
+    String.match?(string, pattern)
+  end
+
+  defp match_any?(string, patterns) do
+    Enum.any?(patterns, &match_string?(string, &1))
+  end
+
+  defp process_remove(object, :url, patterns) do
+    processed_tag =
+      Enum.filter(
+        object["tag"],
+        fn
+          %{"type" => "Emoji", "icon" => %{"url" => url}} when is_binary(url) ->
+            not match_any?(url, patterns)
+
+          _ ->
+            true
+        end
+      )
+
+    processed_emoji =
+      if object["emoji"] do
+        object["emoji"]
+        |> Enum.reduce(%{}, fn {name, url}, acc ->
+          if not match_any?(url, patterns) do
+            Map.put(acc, name, url)
+          else
+            acc
+          end
+        end)
+      else
+        nil
+      end
+
+    if processed_emoji do
+      object
+      |> Map.put("tag", processed_tag)
+      |> Map.put("emoji", processed_emoji)
+    else
+      object
+      |> Map.put("tag", processed_tag)
+    end
+  end
+
+  @impl Pleroma.Web.ActivityPub.MRF.Policy
+  def describe do
+    # This horror is needed to convert regex sigils to strings
+    mrf_emoji =
+      Pleroma.Config.get(:mrf_emoji, [])
+      |> Enum.map(fn {key, value} ->
+        {key,
+         Enum.map(value, fn
+           pattern ->
+             if not is_binary(pattern) do
+               inspect(pattern)
+             else
+               pattern
+             end
+         end)}
+      end)
+      |> Enum.into(%{})
+
+    {:ok, %{mrf_emoji: mrf_emoji}}
+  end
+
+  @impl Pleroma.Web.ActivityPub.MRF.Policy
+  def config_description do
+    %{
+      key: :mrf_emoji,
+      related_policy: "Pleroma.Web.ActivityPub.MRF.EmojiPolicy",
+      label: "MRF Emoji",
+      description:
+        "Reject or force-unlisted emojis whose URLs or names match a keyword or [Regex](https://hexdocs.pm/elixir/Regex.html).",
+      children: [
+        %{
+          key: :remove_url,
+          type: {:list, :string},
+          description: """
+            A list of patterns which result in emoji whose URL matches being removed from the message. This will apply to both statuses and user profiles.
+
+            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: :remove_shortcode,
+          type: {:list, :string},
+          description: """
+            A list of patterns which result in emoji whose shortcode matches being removed from the message. This will apply to both statuses and user profiles.
+
+            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_url,
+          type: {:list, :string},
+          description: """
+            A list of patterns which result in message with emojis whose URLs match being removed from federated timelines (a.k.a unlisted). This will apply only to statuses.
+
+            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_shortcode,
+          type: {:list, :string},
+          description: """
+            A list of patterns which result in message with emojis whose shortcodes match being removed from federated timelines (a.k.a unlisted). This will apply only to statuses.
+
+            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]
+        }
+      ]
+    }
+  end
+end

test/pleroma/web/activity_pub/mrf/emoji_policy_test.exs

@@ -0,0 +1,123 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2023 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.EmojiPolicyTest do
+  use Pleroma.DataCase
+
+  alias Pleroma.Web.ActivityPub.MRF
+  alias Pleroma.Web.ActivityPub.MRF.EmojiPolicy
+
+  setup do: clear_config(:mrf_emoji)
+
+  setup do
+    clear_config([:mrf_emoji], %{
+      remove_url: [],
+      remove_shortcode: [],
+      federated_timeline_removal_url: [],
+      federated_timeline_removal_shortcode: []
+    })
+  end
+
+  @emoji_tags [
+    %{
+      "icon" => %{
+        "type" => "Image",
+        "url" => "https://example.org/emoji/biribiri/mikoto_smile2.png"
+      },
+      "id" => "https://example.org/emoji/biribiri/mikoto_smile2.png",
+      "name" => ":mikoto_smile2:",
+      "type" => "Emoji",
+      "updated" => "1970-01-01T00:00:00Z"
+    },
+    %{
+      "icon" => %{
+        "type" => "Image",
+        "url" => "https://example.org/emoji/biribiri/mikoto_smile3.png"
+      },
+      "id" => "https://example.org/emoji/biribiri/mikoto_smile3.png",
+      "name" => ":mikoto_smile3:",
+      "type" => "Emoji",
+      "updated" => "1970-01-01T00:00:00Z"
+    },
+    %{
+      "icon" => %{
+        "type" => "Image",
+        "url" => "https://example.org/emoji/nekomimi_girl_emoji/nekomimi_girl_emoji_007.png"
+      },
+      "id" => "https://example.org/emoji/nekomimi_girl_emoji/nekomimi_girl_emoji_007.png",
+      "name" => ":nekomimi_girl_emoji_007:",
+      "type" => "Emoji",
+      "updated" => "1970-01-01T00:00:00Z"
+    },
+    %{
+      "icon" => %{
+        "type" => "Image",
+        "url" => "https://example.org/test.png"
+      },
+      "id" => "https://example.org/test.png",
+      "name" => ":test:",
+      "type" => "Emoji",
+      "updated" => "1970-01-01T00:00:00Z"
+    }
+  ]
+
+  @misc_tags [%{"type" => "Placeholder"}]
+
+  @user_data %{
+    "type" => "Person",
+    "id" => "https://example.org/placeholder",
+    "name" => "lol",
+    "tag" => @emoji_tags ++ @misc_tags
+  }
+
+  @status_data %{
+    "type" => "Create",
+    "object" => %{
+      "type" => "Note",
+      "id" => "https://example.org/placeholder",
+      "content" => "lol",
+      "tag" => @emoji_tags ++ @misc_tags,
+      "emoji" => %{
+        "mikoto_smile2" => "https://example.org/emoji/biribiri/mikoto_smile2.png",
+        "mikoto_smile3" => "https://example.org/emoji/biribiri/mikoto_smile3.png",
+        "nekomimi_girl_emoji_007" =>
+          "https://example.org/emoji/nekomimi_girl_emoji/nekomimi_girl_emoji_007.png",
+        "test" => "https://example.org/test.png"
+      }
+    }
+  }
+
+  describe "remove_url" do
+    setup do
+      clear_config([:mrf_emoji, :remove_url], [
+        "https://example.org/test.png",
+        ~r{/biribiri/mikoto_smile[23]\.png},
+        "nekomimi_girl_emoji"
+      ])
+
+      :ok
+    end
+
+    test "processes user" do
+      {:ok, filtered} = MRF.filter_one(EmojiPolicy, @user_data)
+
+      expected_tags = [@emoji_tags |> Enum.at(2)] ++ @misc_tags
+
+      assert %{"tag" => ^expected_tags} = filtered
+    end
+
+    test "processes status" do
+      {:ok, filtered} = MRF.filter_one(EmojiPolicy, @status_data)
+
+      expected_tags = [@emoji_tags |> Enum.at(2)] ++ @misc_tags
+
+      expected_emoji = %{
+        "nekomimi_girl_emoji_007" =>
+          "https://example.org/emoji/nekomimi_girl_emoji/nekomimi_girl_emoji_007.png"
+      }
+
+      assert %{"object" => %{"tag" => ^expected_tags, "emoji" => ^expected_emoji}} = filtered
+    end
+  end
+end