Apache mod_rewrite: explain me %{HTTP_HOST} especially when using addon domains

Question

Apache mod_rewrite: explain me %{HTTP_HOST} expecially when using addon domains

Situation (directories tree) on an Apache server with addon domains:

main-domain.com/ 
| 
|_ .htaccess (just an empty file, no rule in here) 
|_ index.html (shown when accessing http://main-domain.com)
| 
|_ addon-domain-1.com/ 
|  | 
|  |_ .htaccess 
|  |_ index.html (shown when accessing http://addon-domain-1.com or http://main-domain.com/addon-domain-1.com/)
| 
|_ addon-domain-2.com/ 
   | 
   |_ .htaccess 
   |_ index.html (shown when accessing http://addon-domain-2.com or http://main-domain.com/addon-domain-2.com/)

Let's say in "addon-domain-1.com/.htaccess" file I have some rule using %{HTTP_HOST} like:

RewriteCond %{HTTP_HOST} ^something$

Does %{HTTP_HOST} evaluates to the domain of the currently requested url on server???

So if asking for:

http://addon-domain-1.com/

%{HTTP_HOST} will be "addon-domain-1.com"?

http://addon-domain-1.com (without final slash)

%{HTTP_HOST} will still be "addon-domain-1.com"?

http://www.addon-domain-1.com

%{HTTP_HOST} will still be "www.addon-domain-1.com"?

And when asking for:

http://main-domain.com/addon-domain-1.com

%{HTTP_HOST} will be "main-domain.com"???
or "main-domain.com/addon-domain-1.com"???

Seema

Answer 1

You pretty much guessed them all right! The last one would be;

main-domain.com

Seale

Answer 2

%{HTTP_*} evaluates to the HTTP header with the name given after the prefix shown. In HTTP 1.1, the host being accessed is given in the Host header, so yes.

Stephen

And this means, that the client sends the contents of the variable. You can not trust anything from the client. And you should not use untrusted data in a rewrite rule. – Kusin