.

lib/pleroma/web/plugs/uploaded_media.ex

@@ -11,6 +11,7 @@ defmodule Pleroma.Web.Plugs.UploadedMedia do
   require Logger
 
   alias Pleroma.Web.MediaProxy
+  alias Pleroma.Web.Plugs.Utils
 
   @behaviour Plug
   # no slashes
@@ -28,7 +29,9 @@ defmodule Pleroma.Web.Plugs.UploadedMedia do
       |> Keyword.put(:at, "/__unconfigured_media_plug")
       |> Plug.Static.init()
 
-    %{static_plug_opts: static_plug_opts}
+    allowed_mime_types = Pleroma.Config.get([Pleroma.Upload, :allowed_mime_types])
+
+    %{static_plug_opts: static_plug_opts, allowed_mime_types: allowed_mime_types}
   end
 
   def call(%{request_path: <<"/", @path, "/", file::binary>>} = conn, opts) do
@@ -69,13 +72,23 @@ defmodule Pleroma.Web.Plugs.UploadedMedia do
 
   defp media_is_banned(_, _), do: false
 
+  defp set_content_type(conn, opts, filepath) do
+    real_mime = MIME.from_path(filepath)
+    clean_mime = Utils.get_safe_mime_type(opts, real_mime)
+    put_resp_header(conn, "content-type", clean_mime)
+  end
+
   defp get_media(conn, {:static_dir, directory}, _, opts) do
     static_opts =
       Map.get(opts, :static_plug_opts)
       |> Map.put(:at, [@path])
       |> Map.put(:from, directory)
+      |> Map.put(:content_type, false)
 
-    conn = Plug.Static.call(conn, static_opts)
+    conn =
+      conn
+      |> set_content_type(opts, conn.request_path)
+      |> Plug.Static.call(static_opts)
 
     if conn.halted do
       conn

lib/pleroma/web/plugs/utils.ex

@@ -0,0 +1,14 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.Plugs.Utils do
+  @moduledoc """
+  Some helper functions shared across several plugs
+  """
+
+  def get_safe_mime_type(%{allowed_mime_types: allowed_mime_types} = _opts, mime) do
+    [maintype | _] = String.split(mime, "/", parts: 2)
+    if maintype in allowed_mime_types, do: mime, else: "application/octet-stream"
+  end
+end