[Nginx] Bad Gateway

Bonjour,

J'ai installé un serveur nginx pour effectuer une terminaison SSL / TLS qui retransmet ensuite toutes les demandes à un serveur proxy interne pour faire de l'autentification avec auth0.
Le serveur nginx fonctionne, j'arrive à accèder à la pages d'accueil. J'ai installé nodejs et auth0, j'arrive à accèder à la page d'autentification. Tout fonctionne indépendamment ^^. Puis quand j'essaye de tout assembler ca ne marche pas.

Ce que je fais

/etc/nginx/nginx.conf

events {
}

http {
    map $http_upgrade $connection_upgrade {
        default upgrade;
        ''      close;
    }

    # Listen on port 80 and redirect all requests to the 
    # TLS enabled server (https, port 443)
    server {
        listen       *:80;

        # Your hostname should go here
        server_name  localhost;

        access_log   off;
        location / {
            rewrite ^ https://$host$request_uri? permanent;
        }
    }

    # TLS enabled server
    server {
        listen       443 ssl;

        # Your hostname should go here
        server_name localhost;

        # TLS/SSL certificates for your secure server should go here.
        ssl_certificate /etc/ssl/certs/nginx-selfsigned.crt;
        ssl_certificate_key /etc/ssl/private/nginx-selfsigned.key;

        # To enhance security, as long as you don't need to support older browsers
        # (and you probably don't), you should only enable the most secure 
        # ciphers and algorithms. This is a sane selection.
        ssl_ciphers ""EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH"";
        ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
        ssl_prefer_server_ciphers on;
        ssl_session_cache  builtin:1000  shared:SSL:10m;

        # This proxies requests to our shiny-auth0 authentication proxy. 
        # Requests are passed in plain HTTP, so TLS termination
        # is applied at this point.
        location / {
            proxy_set_header    Host $host;

            # This points to our shiny-auth0 authentication proxy,
            # change localhost:3000 to suit the configuration of 
            # your shiny-auth0 config
            proxy_pass          http://127.0.0.1:3000;
            proxy_redirect      http://127.0.0.1:3000/ $scheme://$host/;

            proxy_http_version  1.1;

            # The following lines enable WebSockets proxying, do not remove them
            # as they are used by Shiny Server to improve user experience
            proxy_set_header    Upgrade $http_upgrade;
            proxy_set_header    Connection $connection_upgrade;

            proxy_connect_timeout 3h;
            proxy_send_timeout 3h;
            proxy_read_timeout 3h;
        }
    }
}

Ce que je veux

Je voudrais quand on tape l'adresse du serveur nginx, il redirige vers la page d'autentification de auth0

Ce que j'obtiens

/var/log/nginx/error.log
2018/01/23 06:53:38 [crit] 1545#0: *3 connect() to 127.0.0.1:3000 failed (13: Permis
sion denied) while connecting to upstream, client: 191.250.99.150, server: $localho
st, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:3000/", host: "30.200.131
.212"