Switch from serving a 400 to a 302

changelog.d/3896.add

@@ -1 +1 @@
-Validate Host header for MediaProxy and Uploads
+Validate Host header for MediaProxy and Uploads and return a 302 if the base_url has changed

lib/pleroma/web/media_proxy/media_proxy_controller.ex

@@ -207,12 +207,25 @@ defp media_proxy_opts do
   end
 
   defp validate_host(conn, _params) do
-    proxy_host = MediaProxy.base_url() |> URI.parse() |> Map.get(:host)
+    %{scheme: proxy_scheme, host: proxy_host, port: proxy_port} =
+      MediaProxy.base_url() |> URI.parse()
 
     if match?(^proxy_host, conn.host) do
       conn
     else
-      send_resp(conn, 400, Conn.Status.reason_phrase(400))
+      redirect_url =
+        %URI{
+          scheme: proxy_scheme,
+          host: proxy_host,
+          port: proxy_port,
+          path: conn.request_path,
+          query: conn.query_string
+        }
+        |> URI.to_string()
+        |> String.trim_trailing("?")
+
+      conn
+      |> Phoenix.Controller.redirect(external: redirect_url)
       |> halt()
     end
   end

lib/pleroma/web/plugs/uploaded_media.ex

@@ -46,7 +46,8 @@ def call(%{request_path: <<"/", @path, "/", file::binary>>} = conn, opts) do
 
     config = Pleroma.Config.get(Pleroma.Upload)
 
-    media_host = Pleroma.Upload.base_url() |> URI.parse() |> Map.get(:host)
+    %{scheme: media_scheme, host: media_host, port: media_port} =
+      Pleroma.Upload.base_url() |> URI.parse()
 
     with {:valid_host, true} <- {:valid_host, match?(^media_host, conn.host)},
          uploader <- Keyword.fetch!(config, :uploader),
@@ -56,7 +57,19 @@ def call(%{request_path: <<"/", @path, "/", file::binary>>} = conn, opts) do
       get_media(conn, get_method, proxy_remote, opts)
     else
       {:valid_host, false} ->
-        send_resp(conn, 400, Plug.Conn.Status.reason_phrase(400))
+        redirect_url =
+          %URI{
+            scheme: media_scheme,
+            host: media_host,
+            port: media_port,
+            path: conn.request_path,
+            query: conn.query_string
+          }
+          |> URI.to_string()
+          |> String.trim_trailing("?")
+
+        conn
+        |> Phoenix.Controller.redirect(external: redirect_url)
         |> halt()
 
       _ ->

test/pleroma/web/media_proxy/media_proxy_controller_test.exs

@@ -54,20 +54,37 @@ test "it returns 403 for invalid signature", %{conn: conn, url: url} do
              } = get(conn, "/proxy/hhgfh/eeee/fff")
     end
 
-    test "it returns a 400 for invalid host", %{conn: conn} do
+    test "it returns a 302 for invalid host", %{conn: conn} do
-      clear_config([:media_proxy, :base_url], "http://mp.localhost/")
+      new_proxy_base = "http://mp.localhost/"
 
-      url =
+      %{scheme: new_proxy_scheme, host: new_proxy_host, port: new_proxy_port} =
+        URI.parse(new_proxy_base)
+
+      clear_config([:media_proxy, :base_url], new_proxy_base)
+
+      proxy_url =
         MediaProxy.encode_url("https://pleroma.social/logo.jpeg")
         |> URI.parse()
         |> Map.put(:host, "wronghost")
         |> URI.to_string()
 
+      expected_url =
+        URI.parse(proxy_url)
+        |> Map.put(:host, new_proxy_host)
+        |> Map.put(:port, new_proxy_port)
+        |> Map.put(:scheme, new_proxy_scheme)
+        |> URI.to_string()
+
       with_mock Pleroma.ReverseProxy,
         call: fn _conn, _url, _opts -> %Conn{status: :success} end do
-        %{status: status} = get(conn, url)
+        %{resp_headers: resp_headers, status: status} = get(conn, proxy_url)
 
-        assert status == 400
+        assert status == 302
+
+        assert Enum.any?(
+                 resp_headers,
+                 &(&1 == {"location", expected_url})
+               )
       end
     end
 

test/pleroma/web/plugs/uploaded_media_plug_test.exs

@@ -48,10 +48,27 @@ test "denies access to media if wrong Host", %{
 
     assert conn.status == 200
 
-    clear_config([Pleroma.Upload, :base_url], "http://media.localhost/")
+    new_media_base = "http://media.localhost:8080"
+
+    %{scheme: new_media_scheme, host: new_media_host, port: new_media_port} =
+      URI.parse(new_media_base)
+
+    clear_config([Pleroma.Upload, :base_url], new_media_base)
 
     conn = get(build_conn(), attachment_url)
 
-    assert conn.status == 400
+    expected_url =
+      URI.parse(attachment_url)
+      |> Map.put(:host, new_media_host)
+      |> Map.put(:port, new_media_port)
+      |> Map.put(:scheme, new_media_scheme)
+      |> URI.to_string()
+
+    assert conn.status == 302
+
+    assert Enum.any?(
+             conn.resp_headers,
+             &(&1 == {"location", expected_url})
+           )
   end
 end