custom 403 error page quirk

[megamic]

Maxim Dounin Wrote:
-------------------------------------------------------
> Hello!
> 
> On Mon, Nov 01, 2010 at 03:02:21AM -0400, megamic
> wrote:
> 
> > Hi
> > 
> > I have been trying to imlement a custom 403
> error page  - to be
> > triggered when the request method is not in
> HEAD,GET,POST. I started
> > with something like this (note I was
> specifically triggering the 403
> > error for GET requests for testing):
> > 
> >   root /htdocs
> > 
> >   location = /403.html {
> >         internal;
> >   }
> > 
> >   error_page 403 = /403.html;
> > 
> >   if ($request_method !~ ^(POST)$ ) {
> >      return 403;
> >   }
> > 
> >     location / {
> >         index index.html;
> >     }
> > 
> > For some reason, the above config *always*
> caused nginx internal 403
> > error page to be generated - instead of my
> custom page at
> > /htdoc/403.html.
> > 
> > After scouring forums and whatnot, I found a
> suggestion, which is to put
> > the if() inside the location block - like:
> > 
> >     location / {
> >         index index.html;
> > 
> >          if ($request_method !~ ^(POST)$ ) {
> >              return 403;
> >         }
> >     }
> > 
> > Doing this and everything seemed to work. I just
> don't understand why -
> > can someone explain this?
> 
> http://nginx.org/pipermail/nginx/2010-October/0233
> 53.html

Thanks for this link, it does seem to explain things if I understood it
correctly. So basically what was going on in this:

1) The return 403 in the server{} body caused 403 to be return on every
internal redirect where method != POST
2) The first one was the actual request, which returned 403 as the
method was not POST
3) We then tried to access location /403.html, however this was also
checked against the 403 rule, and as the method was != POST, we return
another 403
4) As you said in the last response..."wow, we've already done
error_page redirection and 
  this resulted in another error, return default error page"

So...I guess my next question would be how to elegantly apply a rule
like this against all locations (or a number of selected locations),
without having to copy it into the location{} body for each one?

Cheers

> 
> Maxim Dounin
> 
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Posted at Nginx Forum: http://forum.nginx.org/read.php?2,146462,146489#msg-146489