Nginx 如何代理需要验证的地址 http://user:password@host/

server {
    listen       80;
    server_name  localhost;

    location /sk {
        proxy_pass       http://host:9000/xxx;
        proxy_set_header Authorization "Basic Z3Vlc3Q6Z3Vlc3Q";
    }

返回: 400 Bad Request nginx 日志: No connection could be made because the target machine actively refused it

直接写 proxy_pass http://user:password@host:9000/xxx; nginx 甚至无法启动

代理这种需要验证的地址, 该怎么配置的?