preventing rewrite loops with "index"

[Dennis J.]

On 01/23/2010 04:59 AM, Maxim Dounin wrote:
> 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:

With ~ the condition is false too after all I'm calling "/test.index.html" 
but if "if" is generally buggy then I gues that might be the problem.

> http://wiki.nginx.org/IfIsEvil

So how do I accomplish what I'm trying to do above with nginx?
For Apache this would look something like this:

RewriteCond %{HTTP_REFERER} !www.mydomain.com
RewriteCond %{HTTP_REFERER} !^$
RewriteRule \.(mpg|zip|avi)$ - [F]

What is the equivalent in nginx?

Regards,
   Dennis