nginx error_page redirect retaining header - nginx

Question

I am trying to write an nginx configuration for authentication, but I am unsure of how to retain headers when using a 302 redirect.
Below is an example of how the server is setup.
location / {
#send to /auth/ for authentication
request_auth /auth/;
#upon failure, redirect to login
error_page 401 404 = #noaccess;
...
}
location #noaccess {
return 302 /login/;
}
location /auth/ {
internal;
proxy_pass http://127.0.0.1:8888/;
proxy_pass_request_body off;
proxy_set_header Content-Length "";
#The header set here is what I would like to retain
proxy_set_header X-Original-URI $request_uri;
}
location /login/ {
proxy_pass http://127.0.0.1:9000/;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
#by the time 302 redirect, $request_uri is no longer the original...
proxy_set_header X-Target $request_uri;
}
Essentially all requests to the server must first be authenticated in the /auth/ location. This location will generally possess the $request_uri that I care about in its sub request. However, whenever the requeset_auth directive fails, and we are redirected with the #noaccess location, nginx makes a new request to /login/.
Is there a way for me to retain the original $request_uri such that it is sent as a header to the /login/ location? (this is needed in order to do a redirect later upon successful authentication).
I've seen some users talk about the auth_request_set directive, but I honestly do not understand how to use it effectively and how the headers of the sub request are renamed or made available.

Answer 1

Yes. With cookies.
Browser state is managed with cookies, so you need to be sending a Set-Cookie header with the 302 that has $request_uri and then convert the cookie to a header in the /login/ location.