htaccess: How to redirect to 404 if url parameter is missing or invalid?

Question

Assume the following folder structure on the webserver (Apache): https://somedomain.com/parentfolder/childfolder.

Using .htaccess, I'd like to display the childfolder and any of it's children (files as well as folders) only the URL contains a certain parameter. For example, the page should be shown if it's requested by:

https://somedomain.com/parentfolder/childfolder?secretparameter=secretvalue123 

However if

• the value of parameter secretparameter is not exactly secretvalue123 or
• the parameter secretparameter is missing,

then a 404 error should be returned.

Do you have any ideas how the .htaccess rules would look like to accomplish this? Your help is greatly appreciated, thank you.

Answer 1

So, if the query string is not secretparameter=secretvalue123 when requesting a resource within the childfolder then issue a 404 not found. You can do something like the following at the top of the .htaccess file in the document root using mod_rewrite:

RewriteEngine On RewriteCond %{QUERY_STRING} !=secretparameter=secretvalue123 RewriteRule ^parentfolder/childfolder - [R=404] 

This blocks the request if the query string is not exactly equal to secretparameter=secretvalue123. (You don't need the L flag here when specifying a non-3xx code as it is implied.)

You could simplify the RewriteRule slightly if instead, you placed these directives in the subdirectory you want to protect. ie. at /parentfolder/childfolder/.htaccess. For example:

RewriteRule ^ - [R=404]