Question about RewriteRule and HTTP_HOST server variable

apache-2.2mod-rewriterewrite

In evaluating a rewrite rule that redirects to a specific URL and say the rewrite condition is met, would it be possible to use HTTP_HOST as part of the URL to be redirected to?

Example in question: 

RewriteRule .*\.(jpg|jpe?g|gif|png|bmp)$ http://%{HTTP_HOST}/no-leech.jpg [R,NC]

The motive behind this question is a desire to create a single htaccess file that would match against an addon domain (on a shared hosting account) and an infinite amount of subdomains below it to prevent hotlinking of images.

Best Answer

You can use %1 (and %2, etc) to access matches in preceding RewriteCond statements:

RewriteEngine On
# don't redirect no-leech.jpg or we'll end up in a loop
RewriteCond %{REQUEST_URI} !^/no-leech.jpg$
# match Host header and store
RewriteCond %{HTTP_HOST} (.*)
RewriteRule \.(jpg|jpe?g|gif|png|bmp)$ http://%1/no-leech.jpg [R,NC,L]

Test:

# GET -Sd http://localhost/foo.jpg
GET http://localhost/foo.jpg --> 302 Found
GET http://localhost/no-leech.jpg --> 200 OK

And with a different Host header:

# GET -SedH 'Host: foo.bar.com' http://localhost/foo.jpg
GET http://localhost/foo.jpg --> 302 Found
GET http://foo.bar.com/no-leech.jpg --> 200 OK
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