I have an Apache (2.2) serving a web-app on example.com. That web-app has a debug-page reachable via example.com/debug. /debug is currently protected with a HTTP basic auth. As there is only a very small user-base who has access to the debug-page, I would like to hide it based on IP address and return 404 to clients not accessing from our VPN.

Serving a 404 based on IP-address only is easy and is described in http://serverfault.com/a/13071. But as soon I add authentication, the users see a 401 instead of a 404.

Basically, what I need is:

if ($REMOTE_ADDR ~ 10.11.12.*):
  do_basic_auth (aka return 401)
else:
  return 404