Create NsfwApiPolicy

config/config.exs

@@ -404,6 +404,13 @@ config :pleroma, :mrf_object_age,
   threshold: 604_800,
   actions: [:delist, :strip_followers]
 
+config :pleroma, :mrf_nsfw_api,
+  url: "http://127.0.0.1:5000/",
+  threshold: 0.7,
+  mark_sensitive: true,
+  unlist: false,
+  reject: false
+
 config :pleroma, :rich_media,
   enabled: true,
   ignore_hosts: [],

lib/pleroma/web/activity_pub/mrf/nsfw_api_policy.ex

@@ -0,0 +1,185 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.NsfwApiPolicy do
+  @moduledoc """
+  Hide, delete, or mark sensitive NSFW content with artificial intelligence.
+
+  Requires a NSFW API server, configured like so:
+
+      config :pleroma, Pleroma.Web.ActivityPub.MRF.NsfwMRF,
+        url: "http://127.0.0.1:5000/",
+        threshold: 0.8,
+        mark_sensitive: true,
+        unlist: false,
+        reject: false
+
+  The NSFW API server must implement an HTTP endpoint like this:
+
+      curl http://localhost:5000/?url=https://fedi.com/images/001.jpg
+
+  Returning a response like this:
+
+      {"score", 0.314}
+
+  Where a score is 0-1, with `1` being definitely NSFW.
+
+  A good API server is here: https://github.com/EugenCepoi/nsfw_api
+  You can run it with Docker with a one-liner:
+
+      docker run -it -p 127.0.0.1:5000:5000/tcp --env PORT=5000 eugencepoi/nsfw_api:latest
+
+  Options:
+
+  - `url`: Base URL of the API server. Default: "http://127.0.0.1:5000/"
+  - `threshold`: Lowest score to take action on. Default: `0.7`
+  - `mark_sensitive`: Mark sensitive all detected NSFW content? Default: `true`
+  - `unlist`: Unlist all detected NSFW content? Default: `false`
+  - `reject`: Reject all detected NSFW content (takes precedence)? Default: `false`
+  """
+  alias Pleroma.Config
+  alias Pleroma.Constants
+  alias Pleroma.HTTP
+  alias Pleroma.User
+
+  require Logger
+  require Pleroma.Constants
+
+  @behaviour Pleroma.Web.ActivityPub.MRF
+  @policy :mrf_nsfw_api
+
+  defp build_request_url(url) do
+    Config.get([@policy, :url])
+    |> URI.parse()
+    |> Map.put(:query, "url=#{url}")
+    |> URI.to_string()
+  end
+
+  defp parse_url(url) do
+    request = build_request_url(url)
+
+    with {:ok, %Tesla.Env{body: body}} <- HTTP.get(request) do
+      Jason.decode(body)
+    else
+      error ->
+        Logger.warn("""
+        [NsfwApiPolicy]: The API server failed. Skipping.
+        #{inspect(error)}
+        """)
+
+        error
+    end
+  end
+
+  defp check_url_nsfw(url) when is_binary(url) do
+    threshold = Config.get([@policy, :threshold])
+
+    case parse_url(url) do
+      {:ok, %{"score" => score}} when score >= threshold ->
+        {:nsfw, %{url: url, score: score, threshold: threshold}}
+
+      _ ->
+        {:sfw, url}
+    end
+  end
+
+  defp check_url_nsfw(%{"href" => url}) when is_binary(url) do
+    check_url_nsfw(url)
+  end
+
+  defp check_attachment_nsfw(%{"url" => urls} = attachment) when is_list(urls) do
+    if Enum.all?(urls, &match?({:sfw, _}, check_url_nsfw(&1))) do
+      {:sfw, attachment}
+    else
+      {:nsfw, attachment}
+    end
+  end
+
+  defp check_object_nsfw(%{"attachment" => attachments} = object) when is_list(attachments) do
+    if Enum.all?(attachments, &match?({:sfw, _}, check_attachment_nsfw(&1))) do
+      {:sfw, object}
+    else
+      {:nsfw, object}
+    end
+  end
+
+  defp check_object_nsfw(%{"object" => %{} = child_object} = object) do
+    case check_object_nsfw(child_object) do
+      {:sfw, _} -> {:sfw, object}
+      {:nsfw, _} -> {:nsfw, object}
+    end
+  end
+
+  defp check_object_nsfw(object), do: {:sfw, object}
+
+  @impl true
+  def filter(object) do
+    with {:sfw, object} <- check_object_nsfw(object) do
+      {:ok, object}
+    else
+      {:nsfw, _data} -> handle_nsfw(object)
+      _ -> {:reject, "NSFW: Attachment rejected"}
+    end
+  end
+
+  defp handle_nsfw(object) do
+    if Config.get([@policy, :reject]) do
+      {:reject, object}
+    else
+      {:ok,
+       object
+       |> maybe_unlist()
+       |> maybe_mark_sensitive()}
+    end
+  end
+
+  defp maybe_unlist(object) do
+    if Config.get([@policy, :unlist]) do
+      unlist(object)
+    else
+      object
+    end
+  end
+
+  defp maybe_mark_sensitive(object) do
+    if Config.get([@policy, :mark_sensitive]) do
+      mark_sensitive(object)
+    else
+      object
+    end
+  end
+
+  defp unlist(%{"to" => to, "cc" => cc, "actor" => actor} = object) do
+    with %User{} = user <- User.get_cached_by_ap_id(actor) do
+      to =
+        [user.follower_address | to]
+        |> List.delete(Constants.as_public())
+        |> Enum.uniq()
+
+      cc =
+        [Constants.as_public() | cc]
+        |> List.delete(user.follower_address)
+        |> Enum.uniq()
+
+      object
+      |> Map.put("to", to)
+      |> Map.put("cc", cc)
+    end
+  end
+
+  defp mark_sensitive(%{"object" => child_object} = object) when is_map(child_object) do
+    Map.put(object, "object", mark_sensitive(child_object))
+  end
+
+  defp mark_sensitive(object) when is_map(object) do
+    tags = (object["tag"] || []) ++ ["nsfw"]
+
+    object
+    |> Map.put("tag", tags)
+    |> Map.put("sensitive", true)
+  end
+
+  @impl true
+  def describe, do: {:ok, %{}}
+end