curl 			nginx(proxy_connect)			nginx(NAS)
	 |  					  |							  |
	 |  					  |							  |
(1)	 |-- CONNECT 443 -> 	  |							  |
	 |  					  |							  |
	 |						  |---- [ TCP connection ]--->|
	 |  					  |							  |
	 |  					  |							  |
(2)  |<- HTTP/1.1 200 --------|							  |
	 |  					  |							  |
	 | 建立连接成功 |							  |
	 |  					  							  |
	 　　========= 内网隧道通讯（依赖组件，我这里使用n2n) =======
	 |  					    						  |
	 |  					  							  |
	 |  					  |							  |
	 |   [ SSL stream  ]      |							  |
(3)  |---[ GET / HTTP/1.1] -->|     [ SSL stream ]  	  |
	 |   [ Host: xxxx.com]    |---  [ GET / HTTP/1.1 ] -->.
	 |  					  |		[ Host: xxxx.com ]	  |
	 |  					  |							  |
	 |  					  |							  |
	 |  					  |							  |
	 |  					  |							  |
	 |  					  |		[ SSL stream ]		  |
	 |  [ SSL stream ]	  	  |	<--[ HTTP/1.1 200 OK  ]---'
	 |<--[ HTTP/1.1 200 OK ]--|		[ < html page >    ]  |
	 |  [ < html page > ]     |							  |
	 |  					  |							  |
	 |  					  |							  |

server {
    listen       80;
    server_name  xxx.com www.xxx.com;
    return       301 https://www.xxx.com$request_uri;
}

server {
    listen      443 ssl;
    server_name  xxx.com;
    return       301 https://www.xxx.com$request_uri;

    ssl on;
    ssl_session_cache    shared:SSL:1m;
    ssl_session_timeout  5m;

    ssl_ciphers  HIGH:!aNULL:!MD5;
    ssl_prefer_server_ciphers  on;
    ssl_certificate /usr/local/nginx/conf/keys/xxx.com.pem;
    ssl_certificate_key /usr/local/nginx/conf/xxx.com.key;
}

server {
    listen      443 ssl;
    server_name  www.xxx.com;
    charset utf-8;

    error_log /var/log/nginx/xxx.com.error_log info;
    access_log /var/log/nginx/xxx.com.access_log json_log;

    allow  all;
    autoindex off;
    concat on;
    concat_max_files 40;

    ssl on;
    ssl_session_cache    shared:SSL:1m;
    ssl_session_timeout  5m;

    ssl_ciphers  HIGH:!aNULL:!MD5;
    ssl_prefer_server_ciphers  on;
    ssl_certificate /usr/local/nginx/conf/keys/xxx.com.pem;
    ssl_certificate_key /usr/local/nginx/conf/keys/xxx.com.key;
    location / {
        proxy_pass https://www.xxx.com:443;
    }
}