Custom headers - Is it a bug or what?

[Ruslan Ermilov]

On Mon, Dec 05, 2011 at 10:23:41PM -0200, Henrique Carvalho Alves wrote:
> Em 05/12/2011, às 22:17, Maxim Dounin escreveu:
> 
> > Hello!
> > 
> > On Mon, Dec 05, 2011 at 10:13:47PM -0200, Henrique Carvalho Alves wrote:
> > 
> >> Hi everybody. I have a very simple question to what is possibly a bug.
> >> 
> >> In nginx 1.0.5, given the following nginx.conf:
> >> 
> >> ---
> >> server {
> >> 	server_name myserver;
> >> 
> >> 	location / {
> >> 		uwsgi_pass 127.0.0.1:5001;
> >> 		uwsgi_param HTTP_MY_CUSTOM_HEADER $http_my_custom_header;
> >> 		include uwsgi_params;		
> >> 	}
> >> }
> >> ---
> >> 
> >> Why does this works as expected...
> >> 
> >> $ curl -H "My-Custom-Header: Yes" http://myserver/
> >> 
> >> ...but this doesn't.
> >> 
> >> $ curl -H "MY_CUSTOM_HEADER: Yes" http://myserver/
> >> 
> >> In the latter case, the parameter is passed to my uwsgi application, but it's just an empty string. I know HTTP headers are supposed to be  case-insensitive, but nginx behavior is unexpected when the header doesn't follow the usual format (title-cased, underscores instead of dashes).
> >> 
> >> Anyone had similar need to capture custom headers? Any nginx.conf examples?
> > 
> > http://nginx.org/en/docs/http/ngx_http_core_module.html#underscores_in_headers
> > 
> 
> I knew it should be something stupid. Thank you!

To expand on this, it's actually subject to two directives, the
above mentioned "underscores_in_headers", and "ignore_invalid_headers":
http://nginx.org/en/docs/http/ngx_http_core_module.html#ignore_invalid_headers

The default "underscores_in_headers on" marks headers with underscores
as invalid (I've just updated the documentation to mention this), and
default "ignore_invalid_headers on" ignores them.  Currently nginx is
too restrictive to the headers syntax, so some setups may require
setting this directive to the value "off".