I am doing a rewrite, in an .htaccess file, to another domain like so:
RewriteEngine On
RewriteRule folder/(.*) http://newdomain.com/folder/$1
http://newdomain.com/folder is password protected.
I get an authentication popup from newdomain when the rewrite happens. When I enter credentials, it authenticates them against the server doing the rewrite, not newdomain. The browser just hangs, and in my server error logs it continuously writes "user x not found" until I stop the connection.