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Who Changed my LCM Configuration?

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Tonight I am in Toronto delivering PowerShell.  Yes, this is a far cry from the flip flops that I was wearing in Phoenix just a few days ago.  This class is a little more difficult for reasons other than the snow fall that is coming over the next 24 hours. Instead of 5 days, I only have 3 days to complete this class.  I have to be a little bit picky on the amount of depth that I can go into.  One area that I did not want to skimp on, is the creation of custom properties with Select-Object.

The creation of a hash table is used in other areas of PowerShell, so I took them through the full lesson.  We left off there this evening.  Tomorrow, I’m going to show them a more real life application to show the importance of this skill that many do not care to learn. At least not at first.

Who changed the configuration of my Local Configuration Manager on one of my servers?  As we begin our shift into the DSC world, good practices may be a bit lagging.  One server admin could configure DSC to pull, and then later another one could inadvertently set it back to push.  Hey, crazy things happen, but who did it?

On the server, take a look at the DSC log for event ID 4102 where the message property contains “Operation Set-DscLocalConfigurationManager started”. Oh yeah, I’m going to take the time to do that.  That violates my rule on working harder, not smarter.  Take a look at this.

PS C:\> Invoke-Command -ComputerName S1 -ScriptBlock {
    Get-WinEvent -FilterHashtable @{Logname="Microsoft-Windows-DSC/Operational"
                                    ID=4102} |
        Where-Object Message -like "*Operation Set-DscLocalConfigurationManager started*" |
        Select-Object -ExpandProperty Message}
                                   
Job {2A7444A3-DE29-11E5-80BA-00155D130217} :
Operation Set-DscLocalConfigurationManager started by user sid S-1-5-21-2015014380-1
668822753-3530896179-500 from computer DC.

The SID of the user is in the message property. That is nice, but now you need to translate that SID into a user’s name.   That is where this goes back to my PowerShell class.  What you are about to see is not pretty, but it shows how the skill set of creating custom properties can be very useful.

Invoke-Command -ComputerName S1 -ScriptBlock {
    Get-WinEvent -FilterHashtable @{Logname="Microsoft-Windows-DSC/Operational"
                                    ID=4102}} |
    Where-Object Message -like "*Operation Set-DscLocalConfigurationManager started*" |
    Select-Object -Property TimeCreated, @{
        N="User"
        E={Get-ADUser -filter "SID -eq '$($Data.Message.Split("`n")[1].
            Remove($Data.Message.Split("`n")[1].LastIndexOf("from")).
            Replace("Operation Set-DscLocalConfigurationManager started by user sid ",$Null).
            Trim())'" |
        Select-Object -ExpandProperty Name}
        } 

Um…Wow!  What was I thinking?  Well, here is the result.

TimeCreated          User        
-----------          ----        
2/28/2016 6:40:10 AM Administrator

I see who did it and when.  In the expression attribute, I used the result of the Get-ADUser cmdlet and Select-Object to extract out just the Name property’s value.  The ugly part was all the string manipulation that was required to get just the SID from the message property of the event record.  I needed just the SID value to provide Get-ADUser’s –Filter parameter so PowerShell does the work of tracking this user down for me..

Not all code is going to be good looking, but now you have the code to figure out who caused your server to fall out of compliance. That should make the code a lot better than the 5 to 7.5 inches of snow that I will be driving through tomorrow.


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