SeeCLRly

Fileless SQL Server CLR-based Custom Stored Procedure Command Execution

For more info about the techinque, please visit sekirkity.com

This techinque will allow for the execution of commands on a comprompised Microsoft SQL Server in a novel, fileless manner. The PowerShell module consists of two cmdlets:

1. New-CLRProcedure - This cmdlet enables CLR stored procedures on the SQL Server, reconfigures it, loads the Dot Net assembly into memory, then creates a stored procedure from the loaded assembly.
2. Invoke-CmdExec - This cmdlet passes a specified command to the previously created stored procedure, where it is then executed.

Instructions

First, import the module:

import-module SeeCLRly.ps1

Next, use the New-CLRProcedure cmdlet to create a custom stored procedure on the target SQL Server:

Add-CLRProcedure -Server MSSQL

Finally, use the Invoke-CmdExec cmdlet to execute commands on the target server:

Invoke-CmdExec -Server MSSQL -Command "mkdir c:\temp"

Roadmap

• Create another cmdlet to remove the custom stored procedure from the SQL Server
• Allow for the name of the assembly and the stored procedure to be changed via paramaters.

Acknowledgements

• Jourdan Templeton for his post on how to connect to a SQL Server in PowerShell.
• Andy Novik for his post on how to pass parameters to a custom stored procedure.
• wald0 for guidance.
• tifkin_ for doing it first.
• Scott Sutherland for his amazing work on PowerUpSQL.