Any way to have the default HTTP Authentication redirect to a template when user fails to authenticate?

Question

Referring to https://ellislab.com/expressionengine/user-guide/cp/design/templates/template_access.html#http-authentication

Right now a failed or canceled authentication redirects to the standard server 401 page.

Is there any way to have this redirect to a specific url?

Answer 1

If you look in the EE source (v.2.10.1) you will see the following in system/expressionengine/libraries/Auth.php (line numbers on the left):

156                 if ($authed === FALSE)
157                 {
158                         @header('WWW-Authenticate: Basic realm="'.$realm.'"');
159                         ee()->output->set_status_header(401);
160                         @header("Date: ".gmdate("D, d M Y H:i:s")." GMT");
161                         exit("HTTP/1.0 401 Unauthorized");
162                 }

EE's authentication hijacks the 401 response, dumping out a header and using PHP's exit() function to dump out an "helpful" text string. AFAIK, and based on this evidence, there is no way to catch a 401 HTTP error code in a template, or even a raw Apache directive, without hacking the EE source, which is not recommended.

I have submitted this as a bug to Ellis Labs but have no heard anything back yet. If I do, I will add it to my own SO question that is similar to this.