.htaccess：重写时将请求设置为允许

Question

I'm sure this must have been asked many times but I can't find anything about this on internet or in the doc. I want to deny everything except some requests that are rewrited using RewriteRule.

Currently I'm using this .htaccess:

RewriteEngine On
RewriteRule ^req$ file.php?a=b
<Files *>
    Order Deny,Allow
    Deny from all
</Files>
<Files file.php>
    Order Allow,Deny
    Allow from all
</Files>

I would have liked this .htaccess to allow all requests to file.php, including req as it's rewrited to it. Instead, it won't allow req except if I explicitly mention req in the allowed files:

<Files req>
    Order Allow,Deny
    Allow from all
</Files>

Is it possible to avoid this behaviour, something like the opposite of the F flag?