Hide a request cookie in proxy_pass

Server NGINX
1

Hi,

is it possible to hide one request cookie (but not all, so
proxy_set_header
Cookie “” is not the way) when proxying to an upstream server?

The use case is:

  • website foo.com uses a hosted service on a subdomain, e.g.
    blog.foo.com
    hosted by Wordpress.com

  • horror: MSIE will send all foo.com cookies to the subdomain too,
    leaking
    sessions (not just to Wordpress.com but to everyone because blog.foo.com
    does not support HTTPS), and there’s no way to tell it not to

  • proposed workaround: serve blog.foo.com yourself, using Nginx,
    HTTPS-only,
    proxying to the hosted service (as foo.wordpress.com, which does support
    HTTPS), and stripping out the parent-domain request cookies

Is there a way to do this with Nginx? A way to rewrite the Cookie header
to
strip out selected cookies?

Or is the only way out of this to avoid the subdomain cookie situation
altogether, either by running www.foo.com instead of foo.com, or by
abandoning the subdomain and using e.g. foo.com/blog/ instead?

Thanks,

Gulli

Posted at Nginx Forum:

2

Hello!

On Fri, Aug 29, 2014 at 11:55:08AM -0400, gthb wrote:

  • horror: MSIE will send all foo.com cookies to the subdomain too, leaking
    sessions (not just to Wordpress.com but to everyone because blog.foo.com
    does not support HTTPS), and there’s no way to tell it not to

  • proposed workaround: serve blog.foo.com yourself, using Nginx, HTTPS-only,
    proxying to the hosted service (as foo.wordpress.com, which does support
    HTTPS), and stripping out the parent-domain request cookies

Is there a way to do this with Nginx? A way to rewrite the Cookie header to
strip out selected cookies?

With proxy_set_header you can change the header to any value,
including one with a particular cookie removed. The tricky part
is to construct new value for the original header. Something like
this should work:

set $new_cookie $http_cookie;

if ($http_cookie ~ "(.*)(?:^|;)\s*secret=[^;]+(.*)") {
    set $new_cookie $1$2;
}

proxy_pset_header Cookie $new_cookie;

(Note that the above is completely untested.)

–
Maxim D.
http://nginx.org/

3

Yep, works like a charm, thank you! And two consecutive ifs to strip two
cookies works as well:

set $stripped_cookie $http_cookie;
if ($http_cookie ~ "(.*)(?:^|;)\s*sessionid=[^;]+(.*)$") {
    set $stripped_cookie $1$2;
}
if ($stripped_cookie ~ "(.*)(?:^|;)\s*csrftoken=[^;]+(.*)$") {
    set $stripped_cookie $1$2;
}

Cheers,

Gulli

Posted at Nginx Forum: