Configure the Nginx server's anti-theft chain function through LUA _nginx

The download server is often hotlinking, and the time has long caused the server to waste a lot of resources, because the server uses Nginx as a Web server. Nginx anti-theft Chain Method There are many, can use off-the-shelf anti-theft chain module nginx-accesskey-2.0.3, compile ningx Add this module can.
Because of the other business needs of the service, Nginx compiles the LUA module, so I want to implement the Anti-Theft chain feature of the download server via LUA (through LUA's Nginx module Lua_nginx_module, where the configuration process is no longer detailed), This eliminates the accesskey module. The principle is to generate a processed download link, and then download the server processing this download link, the success of the download, failure is blocked. The following are detailed configuration examples:
Nginx configuration of the link generated on the download page
Download.jb51.net configuration:

Server  
{  
    listen    ;  
    server_name download.jb51.net;  
    Index index.htm index.html;  
    Root/data/www/download;  
    SSI on;  
 
    Location/  
    {  
        Set_by_lua $downkey ' return  
            ngx.md5 ("Encryption" ... ngx.var.remote_addr. "suffix")  
        ';  
    }  
} 

Note: To open SSI to get nginx custom variable Downkey in an HTML page, you can generate a processed URL in which the strings encryption and suffix are custom and can be arbitrarily changed to other characters, in order to generate a string that is not easily guessed by others.
To test index.html code:
Second, download server Nginx configuration:

Server  
{  
    listen    ;  
    server_name down.jb51.net;  
    Index index.htm index.html;  
    Root/data/www/down;  
    Limit_conn one  1;  
    Set $limit _rate 1000k;  
 
  Location/  
    {  
        Set_by_lua $foo '  
            if String.sub (Ngx.var.uri, 2,) = = NGX.MD5 ("Encryption"). Ngx.var.remote_addr.. "suffix") then return  
                1 
            else return 
                0 
            end  
        ';  
 
        if ($foo = 1)  
        {  
            rewrite "^/([0-9a-z]{32}) (. *?) $ "$ break    ;  
        }  
        " if ($foo = 0)  
        {  
            rewrite ^/http://download.jb51.net/404.htm redirect;  
        }  
    }  
} 

When you copy the link to another machine, you will open the prompt error page.