ReverseProxy: Sanitize content.

lib/pleroma/reverse_proxy.ex

@@ -17,6 +17,8 @@ defmodule Pleroma.ReverseProxy do
   @failed_request_ttl :timer.seconds(60)
   @methods ~w(GET HEAD)
 
+  @allowed_mime_types Pleroma.Config.get([Pleroma.Upload, :allowed_mime_types], [])
+
   @cachex Pleroma.Config.get([:cachex, :provider], Cachex)
 
   def max_read_duration_default, do: @max_read_duration
@@ -301,10 +303,26 @@ defmodule Pleroma.ReverseProxy do
     headers
     |> Enum.filter(fn {k, _} -> k in @keep_resp_headers end)
     |> build_resp_cache_headers(opts)
+    |> sanitise_content_type()
     |> build_resp_content_disposition_header(opts)
     |> Keyword.merge(Keyword.get(opts, :resp_headers, []))
   end
 
+  defp sanitise_content_type(headers) do
+    original_ct = get_content_type(headers)
+
+    safe_ct =
+      Pleroma.Web.Plugs.Utils.get_safe_mime_type(
+        %{allowed_mime_types: @allowed_mime_types},
+        original_ct
+      )
+
+    [
+      {"content-type", safe_ct}
+      | Enum.filter(headers, fn {k, _v} -> k != "content-type" end)
+    ]
+  end
+
   defp build_resp_cache_headers(headers, _opts) do
     has_cache? = Enum.any?(headers, fn {k, _} -> k in @resp_cache_headers end)