Media proxy: fix url encoding

lib/pleroma/web/media_proxy/controller.ex

@@ -24,7 +24,12 @@ defmodule Pleroma.Web.MediaProxy.MediaProxyController do
   end
 
   def filename_matches(has_filename, path, url) do
-    filename = MediaProxy.filename(url)
+    filename =
+      url
+      |> MediaProxy.filename()
+      |> URI.decode()
+
+    path = URI.decode(path)
 
     cond do
       has_filename && filename && Path.basename(path) != filename -> {:wrong_filename, filename}

lib/pleroma/web/media_proxy/media_proxy.ex

@@ -14,7 +14,14 @@ defmodule Pleroma.Web.MediaProxy do
       url
     else
       secret = Application.get_env(:pleroma, Pleroma.Web.Endpoint)[:secret_key_base]
-      base64 = Base.url_encode64(url, @base64_opts)
+
+      # The URL is url-decoded and encoded again to ensure it is correctly encoded and not twice.
+      base64 =
+        url
+        |> URI.decode()
+        |> URI.encode()
+        |> Base.url_encode64(@base64_opts)
+
       sig = :crypto.hmac(:sha, secret, base64)
       sig64 = sig |> Base.url_encode64(@base64_opts)