VBScript: Kerberos, Delegation, IIS and User Authentication

Recently, I wanted to write a web-based front end to AD User Management for our help desk. The way that I set it up apparently broke some Kerberos delegation rules and even though Microsoft wrote a step-by-step guide on how to get IIS and Kerberos delegation going, the solution didn’t work for me. If I turned off Anonymous access and authenticated as myself against a remote webserver (local webserver totally worked), I would get the error 0x80040E37 – Table Does Not Exist. The table does exist, of course, I just don’t have the rights to see it. Well, I do but not in the “double hop” manner that I’m attempting it. Kerberos sees that IIS != me.. IIS is only pretending to be me and it doesn’t approve.

After a few days of tinkering, this is the solution I decided on. I set the ASP page in IIS to Anonymous Access but ran that access as a user with the privleges to make changes to user accounts. This can be dangerous in more than one way — if a lesser-privleged user were to somehow have the ability to edit that page, he or she could use it to run any script under the power of that user. So I ensured that unauthorized users were not able to access that file. But now how can I detect who’s running that page? Request.servervariables(“REMOTE_USER”) would be useless since the page is running as that privleged user. I considered what client variables I did have access to and realized that request.servervariables(“REMOTE_HOST”) would be the handiest. I figured that, using WMI and the IP address, it would be possible to figure out what user is actively logged into the client machine. Sure enough…

Function getLoggedInUser(ipaddr)
Set objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!"& ipaddr & "\root\cimv2")
Set colSessions = objWMIService.ExecQuery("Select * from Win32_LogonSession Where LogonType = 2 OR LogonType = 10" )

For Each objSession in colSessions
Set colList = objWMIService.ExecQuery("Associators of {Win32_LogonSession.LogonId=" & objSession.LogonId & "} Where AssocClass=Win32_LoggedOnUser Role=Dependent")
For Each objItem in colList
getLoggedInUser = lcase(objItem.Name)
Next
Next
End Function

This script, which was derived from a tek-tips.com post, worked flawlessly! FWIT, LoginType 2 is console and 10 is remote desktop.

Chrissy has worked in IT for nearly 20 years, and currently serves as a Sr. Systems Engineer for a federal contractor in Belgium. Always an avid scripter, she attended the Monad session at Microsoft’s Professional Developers Conference in Los Angeles back in 2005 and has worked and played with PowerShell ever since. Chrissy is currently pursuing an MS in Systems Engineering at Regis University and helps maintain RealCajunRecipes.com in her spare time. She holds a number of certifications, including those relating to SQL Server, SuSE Linux, SharePoint and network security. She recently became a Microsoft PowerShell MVP. You can follow her on Twitter at @cl.

Posted in Active Directory, IIS, VBScript

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