Set Incoming Request Headers (similar to mod_headers)

[W. Andrew Loe III]

I am trying to emulate an Apache mod_headers feature
(http://httpd.apache.org/docs/2.2/mod/mod_headers.html#requestheader).
I would like to set some headers before my content handler is run.
Specifically SSL related headers that I would like set before my
Passenger process picks up the request. I could do this with
proxy_set_header, but I am not proxying, the request is being picked
up and executed by Passenger.

Config looks like this:

  location / {
    proxy_redirect      off;
    proxy_set_header    Host             $host;
    proxy_set_header    X-Real-IP        $remote_addr;
    proxy_set_header    X-Forwarded-For  $proxy_add_x_forwarded_for;
    proxy_set_header    X-Client-Verify  $ssl_client_verify;
    proxy_set_header    X-Client-DN      $ssl_client_i_dn;
    proxy_set_header    X-SSL-Subject    $ssl_client_s_dn;
    proxy_read_timeout  75;

   passenger_enabled on;
}

This however will not work, the headers are not set when the backend
runs. Do I need to setup a second server block listening on a
different port and then proxy the request to that so I can take
advantage of proxy_set_header, or is there a way to do it like Apache.