There are a lot of hints & tips out there for troubleshooting SPNs, or Service Principal Names. Listing duplicate SPNs is fairly easy, just use setspn -X on your command-line and you’ll find out. But how do you find out which SPNs are used for which users and computers are used for this?

An SPN or Service Principal Name is a unique identity for a service, mapped with a specific account (mostly service account). Using an SPN, you can create multiple aliases for a service mapped with a domain account.

SetSPN command-line

To set, list or delete the SPN, we use an in-built command line tool SETSPN provided by Microsoft.

Quite some scripts assume you’re looking for a specific SPN (HTTP/…), a specific user, or a specific computer. For example, using setspn to find SPNs linked to a certain computer:

setspn -L <ServerName>

Or setspn to find SPNs linked to a certain user account:

setspn -L <domain\user>

And now you need a general script to list all SPNs, for all users and all computers…

Nice fact to know, SPNs are set as an attribute on the user or computer accounts. That makes it fairly ease to query for that attribute.

And modern admins do PowerShell, right?

List SPNs using Powershell

So… Save the following code into a new PowerShell .ps1 file and run it in your domain. It’ll list the SPNs.

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# Source / credit:
# https://social.technet.microsoft.com/wiki/contents/articles/18996.active-directory-powershell-script-to-list-all-spns-used.aspx

cls
$search = New-Object DirectoryServices.DirectorySearcher([ADSI]"")
$search.filter = "(servicePrincipalName=*)"

## You can use this to filter for OU's:
## $results = $search.Findall() | ?{ $_.path -like '*OU=whatever,DC=whatever,DC=whatever*' }
$results = $search.Findall()

foreach( $result in $results ) {
	$userEntry = $result.GetDirectoryEntry()
	Write-host "Object Name = " $userEntry.name -backgroundcolor "yellow" -foregroundcolor "black"
	Write-host "DN      =      "  $userEntry.distinguishedName
	Write-host "Object Cat. = "  $userEntry.objectCategory
	Write-host "servicePrincipalNames"

	$i=1
	foreach( $SPN in $userEntry.servicePrincipalName ) {
		Write-host "SPN(" $i ")   =      " $SPN
		$i+=1
	}
	Write-host ""
}

Or use dsquery on your CMD.exe command-line:

dsquery * "ou=domain controllers,dc=yourdomain,dc=com" -filter "(&(objectcategory=computer)
(servicePrincipalName=*))" -attr distinguishedName servicePrincipalName > spns.txt

This is a valuable script and information reference for your own documentation.


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