Nginx 403 forbidden on static files using link_secure with grafana

I am trying to configure auto login using nginx as auth proxy, I am successfully able to authenticate but my problem comes when grafana loads all static files are 401.

my nginx configuration

#i also tried /grafana by enabling it in the grafana.ini  
  location / {
        secure_link $arg_md5,$arg_expires;
        secure_link_md5 "$secure_link_expires$uri enigma";
        if ($secure_link = "") { return 403; }
        if ($secure_link = "0") { return 410; }
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Session-Token $http_x_session_token;
        proxy_set_header X-WEBAUTH-USER $arg_user;
        proxy_set_header Authorization "";
        #rewrite ^/auth(.*)$ /$1;       

as you can see all of resources are 401 below is link that i use for authentication