Add OnlyMedia Upload Filter to simplify restricting uploads to audio, image, and video types

Original: https://git.pleroma.social/pleroma/pleroma/-/merge_requests/3897

docs/docs/configuration/cheatsheet.md

@@ -615,6 +615,12 @@ This filter only strips the GPS and location metadata with Exiftool leaving colo
 
 No specific configuration.
 
+#### Pleroma.Upload.Filter.OnlyMedia
+
+This filter rejects uploads that are not identified with Content-Type matching audio/\*, image/\*, or video/\*
+
+No specific configuration.
+
 #### Pleroma.Upload.Filter.Mogrify
 
 * `args`: List of actions for the `mogrify` command like `"strip"` or `["strip", "auto-orient", {"implode", "1"}]`.

lib/pleroma/upload/filter.ex

@@ -38,9 +38,9 @@ defmodule Pleroma.Upload.Filter do
       {:ok, :noop} ->
         filter(rest, upload)
 
-      error ->
+      {:error, e} ->
-        Logger.error("#{__MODULE__}: Filter #{filter} failed: #{inspect(error)}")
+        Logger.error("#{__MODULE__}: Filter #{filter} failed: #{inspect(e)}")
-        error
+        {:error, e}
     end
   end
 end

lib/pleroma/upload/filter/only_media.ex

@@ -0,0 +1,20 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2023 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Upload.Filter.OnlyMedia do
+  @behaviour Pleroma.Upload.Filter
+  alias Pleroma.Upload
+
+  def filter(%Upload{content_type: content_type}) do
+    [type, _subtype] = String.split(content_type, "/")
+
+    if type in ["image", "video", "audio"] do
+      {:ok, :noop}
+    else
+      {:error, "Disallowed content-type: #{content_type}"}
+    end
+  end
+
+  def filter(_), do: {:ok, :noop}
+end

test/pleroma/upload/filter/only_media_test.exs

@@ -0,0 +1,32 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2023 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Upload.Filter.OnlyMediaTest do
+  use Pleroma.DataCase, async: true
+
+  alias Pleroma.Upload
+  alias Pleroma.Upload.Filter.OnlyMedia
+
+  test "Allows media Content-Type" do
+    ["audio/mpeg", "image/jpeg", "video/mp4"]
+    |> Enum.each(fn type ->
+      upload = %Upload{
+        content_type: type
+      }
+
+      assert {:ok, :noop} = OnlyMedia.filter(upload)
+    end)
+  end
+
+  test "Disallows non-media Content-Type" do
+    ["application/javascript", "application/pdf", "text/html"]
+    |> Enum.each(fn type ->
+      upload = %Upload{
+        content_type: type
+      }
+
+      assert {:error, _} = OnlyMedia.filter(upload)
+    end)
+  end
+end