server {
    listen       80;
    server_name  localhost;

    #charset koi8-r;
    #access_log  /var/log/nginx/log/host.access.log  main;
    root /opt/app/code;

    location / {
        secure_link $arg_md5,$arg_expires;  # _md5,_expires 连接参数名对应的值  /download?md5=e4Nc3Rm01TBBNYw&expires=1539792000
        secure_link_md5(加密方式) "$secure_link_expires$uri imooc";  # 取expires和url  和 imooc字符串进行加密

        if ($secure_link = "") {
            return 403;
        }

        if ($secure_link = "0") {
            return 410;
        }
    }
}

servername="jeson.t.imooc.io"
download_file="/download/file.img"
time_num=$(date -d "2018-10-18 00:00:00" +%s)
secret_num="imoocc"

res=$(echo -n "${time_num}${download_file} ${secret_num}"|openssl md5 -binary | openssl base64 | tr +/ -_ | tr -d =)

echo "http://${servername}${download_file}?md5=${res}&expires=${time_num}"