preventing rewrite loops with "index"

[Maxim Dounin]

Hello!

On Sat, Jan 23, 2010 at 02:47:12AM +0100, Dennis J. wrote:

> On 01/22/2010 04:01 PM, Igor Sysoev wrote:
> >On Fri, Jan 22, 2010 at 03:06:47PM +0100, Dennis J. wrote:
> >
> >>Hi,
> >>So with my first rewrite issue solved I now move closer towards the real
> >>configuration and run into a problem with the index directive.
> >>
> >>My location looks like this:
> >>
> >>location ~* ^/(([A-Za-z])([A-Za-z0-9])([A-Za-z0-9])[^/]*)(/.*)?$ {
> >>      root /web;
> >>      set $site_path /users/$2/$3/$4/$1/htdocs;
> >>      set $real_uri $5;
> >>      rewrite .* $site_path$real_uri break;
> >>}
> >>
> >>When I request "/test/index.html" the location matches and gets properly
> >>rewritten into a hashed form "/users/t/e/s/test/index.html". Then the root
> >>get prefixed resulting in the path "/web/users/t/e/s/test/index.html" which
> >>get correctly delivered by nginx. So far so good.
> >>
> >>The problem happens when I request "/test/" instead which should deliver
> >>the same index.html through the index directive. That doesn't happen though.
> >>
> >>Looking at the log what seems to happen is that nginx sees that
> >>"/web/users/t/e/s/test/" is a directory and issues a new request with the
> >>uri "/web/users/t/e/s/test/index.html". This however matches the above
> >>location again resulting in another rewrite that ends with a completely
> >>broken path and a 404.
> >>
> >>How can I get that the correct index processing for the first correctly
> >>rewritten path without triggering another round of location processing
> >>messing things up?
> >
> >  location ~* ^/(([A-Za-z])([A-Za-z0-9])([A-Za-z0-9])[^/]*)(/.*)?$ {
> >      alias  /web/users/$2/$3/$4/$1/htdocs$5;
> >  }
> 
> This works as intended, thanks!
> When I try to add a referrer check though I run into trouble. Adding
> the following after the alias directive makes nginx return a 404
> instead of index.html:
> 
>             if ($request_uri ~ zip) {
>             }
> 
> The log says that nginx cannot find the file
> "/web/users/////htdocs". When I change the ~ into a = then nginx
> returns index.html correctly.
> What I'm trying to get at is something similar to this:
> 
> valid_referers none www.mydomain.com;
> if ($request_uri ~* \.(mpg|zip|avi)$) {
>   if ($invalid_referer) {
>     return 405;
>   }
> }
> 
> I noticed that nested if's are not possible so I'm not sure how to
> handle such a case where multiple conditions have to be satisfied
> (name must match and $invalid_referer must be set). But right now
> I'm wondering why changing the "=" into "~" above suddenly results
> in a 404 and the captured variables all beeing empty.

With "=" condition is false.  And - no, there is no surprise here.  
See here for some more details:

http://wiki.nginx.org/IfIsEvil

Maxim Dounin