Windows LAPS Under the Hood Part 2: Defuncted!

Last Updated on February 21, 2024 by rudyooms

This blog is going to show you how the new Automatic Account Management feature in Windows LAPS in combination with another new “hidden” feature, is going to deal with already existing administrator accounts.

I will divide this blog into multiple parts:

  1. Introduction
  2. Duplicate Accounts
  3. Defunct it!
  4. The Flow

1. Introduction

In one of my latest blog posts, I showed you how the new LAPS automatic account management feature is going to make sure that you won’t need to manually create the managed LAPS account any longer. This Automatic Account Management feature is going to do this for you!

Afbeelding met tekst, schermopname, Lettertype, nummer

Automatisch gegenereerde beschrijving

LAPS | Automatic Account Management | WlapsPending (call4cloud.nl)

As shown above, with just some simple settings we could define the managed account name (or name prefix) we want to create with the automatic account management feature.

You can even decide to keep the managed account turned off and just enable it on the fly without changing anything else. Isn’t that awesome? But what if… what if we are turning on this feature, specifying an account name without having looked at other policies first?

2. Duplicate Accounts

For fun, let’s say we are specifying, “admin” as the automatic account that needs to be created by Windows LAPS.

I guess it’s best practice before deploying this policy above, to first take a good look at what configuration policies you already have deployed in your organization.

For now, let’s skip best practices because a long time ago we deployed a CSP to configure the managed account on our own.

This CSP above is creating a new local user and with a second CSP, we are adding it to the local administrator group. All good right?

With that CSP we now have a local admin on the device with the account name: admin but what if we totally forgot about this CSP and we just configure the new LAPS automatic account feature and define the same account name?

If we configure the same account name in the new LAPS feature, I guess we are going to end up with some collisions?

3. Defunct it!

If mister Jay Simmons wasn’t aware of this, we could have ended up with some serious issues. We could have ended up with some nice collisions with the previously created account. Luckily, he was aware! By the looks of it, he added the “defunctAccount” function in the LAPS.DLL

This defunct function is added to the Automatic Account Management flow itself and will guarantee that the LAPS-managed account we specified is always going to be available for its intended purpose. Without this function, we could have ended up in a world of pain when we needed to log in with the WLAPs account

If we take a look at the DefunctAccount function as shown below, we will notice some simple steps that it will take to make sure the account we specified in the Automatic Account management policy is the one that survives the battle.

We will notice that the process kicks off the same way we noticed in the blog I wrote about the automatic account creation process. It will create a WlapsPending user and will try to add it to the local administrator’s group.

From there on it will determine if there is another account with the same name in play. If that’s the case it will first defunct the existing account name. The old admin account will be renamed to wlapsdefuncted(randomized)

Once the account is renamed, LAPS will also make sure that the defuncted account is disabled

From there on the regular Automatic Account Creation flow kicks in again and would rename the WLapsPending account to the account name we configured: admin.

With it, we will end up with a “new” admin account that is managed by WLAPS and the old admin account that is being renamed to defuncted!

As shown above, the new admin one is the ruler of the world and the defuncted one lost its job!!

4. The Flow

I guess I don’t need to introduce the world’s most famous flow any longer… so here it is!

Afbeelding met tekst, schermopname, diagram, Parallel

Automatisch gegenereerde beschrijving

Conclusion

With all the new features popping up in the canary build, the automatic account management feature is one of the most asked-for. Luckily Jay also thought about some collisions that could occur when we already had an account with the same name in play

Leave a Reply

Your email address will not be published. Required fields are marked *

  +  49  =  50