Rails - Jun 2009 - request.host, proxy chains and HTTP_X_FORWARDED_HOST

Hi,

We''ve an application that uses url_for in controllers and views. In
views, url_for generates a relative url (as if :only_path where used).
All is fine there.

However, in controllers, url_for generates a full url, with the host
name. This causes problems when we have a chain of Apache proxy
servers:

My Browser ---> Proxy 1 ----> Proxy 2 ----> Phusion Deployment Server.

In this scenario, the request header item HTTP_X_FORWARDED_HOST
contains the following:

proxy1:81, proxy2

Rails extracts the host by splitting this string and getting the last
item:

(actionpack-2.3.2\lib\action_controller\request.rb line 271)

    def raw_host_with_port
      if forwarded = env["HTTP_X_FORWARDED_HOST"]
        forwarded.split(/,\s?/).last
      else
        env[''HTTP_HOST''] ||
"#{env[''SERVER_NAME''] || env
[''SERVER_ADDR'']}:#{env[''SERVER_PORT'']}"
      end
    end

What happens is that we get proxy2 as the host.

Shouldn''t it be trying to get the first item instead -

        forwarded.split(/,\s?/).first

giving us proxy1:81 instead?

Is this a bug? If not, is there reasoning behind this?

Derek.

Actually, I''ve just seen the following in the Django mailing lists:

http://www.mail-archive.com/django-updates-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org/msg33992.html

Looks like the option to select the last item is deliberate.

On Jun 25, 3:15 pm, delboy
<derek.mclough...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Hi,
>
> We''ve an application that uses url_for in controllers and views.
In
> views, url_for generates a relative url (as if :only_path where used).
> All is fine there.
>
> However, in controllers, url_for generates a full url, with the host
> name. This causes problems when we have a chain of Apache proxy
> servers:
>
> My Browser ---> Proxy 1 ----> Proxy 2 ----> Phusion Deployment
Server.
>
> In this scenario, the request header item HTTP_X_FORWARDED_HOST
> contains the following:
>
> proxy1:81, proxy2
>
> Rails extracts the host by splitting this string and getting the last
> item:
>
> (actionpack-2.3.2\lib\action_controller\request.rb line 271)
>
>     def raw_host_with_port
>       if forwarded = env["HTTP_X_FORWARDED_HOST"]
>         forwarded.split(/,\s?/).last
>       else
>         env[''HTTP_HOST''] ||
"#{env[''SERVER_NAME''] || env
>
[''SERVER_ADDR'']}:#{env[''SERVER_PORT'']}"
>       end
>     end
>
> What happens is that we get proxy2 as the host.
>
> Shouldn''t it be trying to get the first item instead -
>
>         forwarded.split(/,\s?/).first
>
> giving us proxy1:81 instead?
>
> Is this a bug? If not, is there reasoning behind this?
>
> Derek.