Forum: NGINX embedded variable $cookie_YYY and "-" symbol.

Hi all. I observe unexpected behavior when trying to use $cookie_YYY
embended variable when cookie name include "-" symbol.

set $uwaver $cookie_un-uwa-version;

$uwaver always equal to "-uwa-version" string instead of real cookie 
value.

maybe i should use some kind of escaping here?

nginx -v
nginx version: nginx/1.2.7

uname -a
Linux cabal 3.2.0-37-generic #58-Ubuntu SMP Thu Jan 24 15:28:10 UTC 2013
x86_64 x86_64 x86_64 GNU/Linux

On Mon, Feb 18, 2013 at 03:54:33PM +0400, Igor Karymov wrote:

Hi there,

> set $uwaver $cookie_un-uwa-version;
>
> $uwaver always equal to "-uwa-version" string instead of real cookie value.
>
> maybe i should use some kind of escaping here?

I believe that the reason is that there are some characters which are
valid in cookie names, but which are not valid in nginx variable names;
and I believe that the only way to access them in nginx.conf is to parse
$http_cookie yourself.

There is a similar problem with the $arg_* variables.

Both the $cookie_ and the $arg_ variables are convenience features,
and they work well provided that you restrict your inputs appropriately.

I'm not sure how much work it would be to create a patch allow, for
example, ${var.iab-le} as a way of accessing a variable named like that;
but I guess that it has been "more work than just avoiding or working
around those variable names" for everyone who has hit the issue so far.

  f
--
Francis Daly        francis@daoine.org

Francis Daly wrote in post #1097580:
> On Mon, Feb 18, 2013 at 03:54:33PM +0400, Igor Karymov wrote:
>
> Hi there,
>
>> set $uwaver $cookie_un-uwa-version;
>>
>> $uwaver always equal to "-uwa-version" string instead of real cookie value.
>>
>> maybe i should use some kind of escaping here?
>
> I believe that the reason is that there are some characters which are
> valid in cookie names, but which are not valid in nginx variable names;
> and I believe that the only way to access them in nginx.conf is to parse
> $http_cookie yourself.
>
> There is a similar problem with the $arg_* variables.
>
> Both the $cookie_ and the $arg_ variables are convenience features,
> and they work well provided that you restrict your inputs appropriately.
>
> I'm not sure how much work it would be to create a patch allow, for
> example, ${var.iab-le} as a way of accessing a variable named like that;
> but I guess that it has been "more work than just avoiding or working
> around those variable names" for everyone who has hit the issue so far.
>
>   f
> --
> Francis Daly        francis@daoine.org

You can work around this for now with a quirk of the way the map module 
works.  It treats any value beginning with $ as a variable name and 
skips some of the validation, so you can:

# The first variable is irrelevant, $is_args just doesn't
# do much processing.
map $is_args $uwaver {
  default $cookie_un-uwa-version;
}

This workaround may become invalid if the map module is ever extended to 
accept complex values, but it just worked in a test for me.

Jon

This workaround has solve my issues. Thank you!