Global variable on NGINX - nginx

Question

I'm using NGINX to serve static files, reverse proxy to Django and verify client certificates.
I don't want the certificate to be asked at the url root, so I created another server on Nginx.conf to ask for the certificate on port 8443. This server is intended just to ask for the certificate and redirect the client back to port 443, where the reverse proxy to Django occurs.
This is my Nginx.conf:
events {
worker_connections 1024;
}
http {
include mime.types;
default_type application/octet-stream;
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
sendfile on;
keepalive_timeout 65;
gzip on;
upstream app {
server django:8000;
}
# Redirect from HTTP to HTTPS
server {
listen *:80;
server_name localhost;
return 301 https://localhost$request_uri;
}
server {
listen *:443 ssl;
server_name localhost;
ssl_certificate /etc/nginx/ssl/certificate.pem;
ssl_certificate_key /etc/nginx/ssl/certificate.key;
ssl_password_file /etc/nginx/ssl/certificate.pass;
ssl_verify_client off;
ssl_client_certificate /etc/nginx/ssl/chain.cer;
ssl_verify_depth 3;
ssl_protocols TLSv1.1 TLSv1.2;
ssl_ciphers EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH;
ssl_prefer_server_ciphers on;
server_tokens off;
underscores_in_headers on;
location /static/ {
autoindex off;
alias /static_files/;
}
location / {
try_files $uri $uri/ #app_web;
}
location #app_web {
proxy_pass http://app;
proxy_pass_request_headers on;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header CERTINFO $http_certinfo;
proxy_redirect off;
}
}
server {
listen *:8443 ssl;
server_name localhost;
ssl_certificate /etc/nginx/ssl/certificate.pem;
ssl_certificate_key /etc/nginx/ssl/certificate.key;
ssl_password_file /etc/nginx/ssl/certificate.pass;
ssl_verify_client on;
ssl_client_certificate /etc/nginx/ssl/certificate.cer
ssl_verify_depth 3;
ssl_protocols TLSv1.1 TLSv1.2;
ssl_ciphers EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH;
ssl_prefer_server_ciphers on;
add_header CERTINFO $ssl_client_s_dn;
return 301 https://$host$request_uri;
}
}
When the client authenticates on port 8443 and I return him to port 443, I need to forward his certificate information, the $ssl_client_s_dn to be more specific. To do so, I'm trying to use the method add_header on the server of the port 8443 (CERTINFO) and the method proxy_set_header capturing the value with $http_certinfo on the server of the port 443. But this solution is not working. The header is not forwarded from port 8443 to port 443 server.
My question is: is there a way to do that? Can I set some kind of "global" variable on the http block, change its value on port 8443 and than use the updated value on port 443 to forward it to Django?
Thank you so much!