NGINX - Limit access to folder to a list of user from ldap authentication - authentication

Question

A have an nginx reverse proxy behind ldap authentication.
I can read username in php from variable $_SERVER['PHP_AUTH_USER']. I think this means that username is passed from ldap to nginx and than to php.
Is it possible in nginx configuration to allow access to a folder only to a list of users?
UPDATE
In nginx the user is stored in $remote_user variable. Is it possible to compare $remote_user with a list of users stored in a file? And then deny or allow access to a folder?
UPDATE
Probably I have to use map directive, for example:
map $remote_user $allowed_user {
default 0;
user1 1;
user2 1;
}
and then test it in the appropriate location:
location /folder/ {
if($allowed_user != 1){
return 403;
}
proxy_pass http://site;
}
but when I do sudo nginx -t, I receive the following error:
nginx: [emerg] unknown directive "if($allowed_user" in /etc/nginx/nginx.conf:104
nginx: configuration file /etc/nginx/nginx.conf test failed

Answer 1

You can do it via map directive (please note that map translate definitions block should be placed in the http context outside the server block):
map $remote_user $deny
username1 0;
username2 0;
...
usernameN 0;
default 1;
}
server {
...
location /folder/ {
if ($deny) { return 403; }
...
}
}
You can pre-generate users list in the above form (username1 0; username 2 0; ...) and then include this list to the nginx configuration:
map $remote_user $deny {
include /path/userlist.txt;
default 1;
}
Whenever this user list file get changed you'd need to reload nginx configuration (nginx -s reload).