Voir : https://www.digitalocean.com/community/tutorials/how-to-set-up-http-authentication-with-nginx-on-ubuntu-12-10

sudo apt-get install apache2-utils

$ sudo htpasswd -c /etc/nginx/.htpasswd exampleuser
New password: 
Re-type new password: 
Adding password for user exampleuser

chmod 640 /etc/nginx/.htpasswd exampleuser
chown www-data:www-data /etc/nginx/.htpasswd

La structure du fichier htpasswd est sous la forme suivante :

login:Hash_mdp

/etc/nginx/sites-available/website_nginx.conf

auth_basic "Restricted";
auth_basic_user_file /etc/nginx/.htpasswd;

Exemple :

/etc/nginx/sites-available/website_nginx.conf

server {
  listen       portnumber;
  server_name  ip_address;
  location / {
      root   /var/www/mywebsite.com;
      index  index.html index.htm;
      auth_basic "Restricted";                    #For Basic Auth
      auth_basic_user_file /etc/nginx/.htpasswd;  #For Basic Auth
  }
}

On vérifie la configuration de Nginx.

nginx -t

Si ok, on la recharge

service nginx reload

Appliquez cette configuration que pour les sites en HTTPS seulement. Sinon, le mot de passe sera envoyé en clair !