Domain join hardening changes

Hi everyone

Today I wanted to talk a change that Microsoft did for domain join.

After the 11 October 2022 the KB5020276 introduce some concept change that will help a lot to make domain join error free.

I will quote the legacy behavior;

Before you install the October 11, 2022, or later cumulative updates, the client computer queries Active Directory for an existing account with the same name. This query occurs during domain join and computer account provisioning. If such an account exists, the client will automatically attempt to reuse it.

Note The reuse attempt will fail if the user who attempts the domain join operation does not have the appropriate write permissions. However, if the user has enough permissions the domain join will succeed.

There are two scenarios for domain join with respective default behaviors and flags as follows:

Domain Join (NetJoinDomain)

Defaults to account reuse (unless NETSETUP_NO_ACCT_REUSE flag is specified)

Account provisioning (NetProvisionComputerAccountNetCreateProvisioningPackage).

Defaults to NO reuse (unless NETSETUP_PROVISION_REUSE_ACCOUNT is specified.)

After the change there is an addional security check that is done.

• Account reuse will be permitted if done by the account creator.
• Account reuse will be permitted if done by a member of the domain admin’s group.

That way if you have delegated the domain join task it enforce more security for account name.

Following that change you can see that error message; which would be normal if the two conditions are not met.

Error 0xaac (2732): NERR_AccountReuseBlockedByPolicy: “An account with the same name exists in Active Directory. Re-using the account was blocked by security policy.”

Some more information on additional’s step that can be done;

Take Action
Review computer account provisioning workflows and understand if changes are required.

Perform the join operation using the same account that created the computer account in the target domain.

If the existing account is stale (unused), delete it before attempting to join the domain again.

Rename the computer and join using a different account that doesn’t already exist.

If the existing account is owned by a trusted security principal and an administrator wants to reuse the account, they might do so by temporarily setting the following registry key at the individual client computer level. Then immediately remove the registry setting after the join operation is complete. No restart is necessary for changes to the registry key to take effect.

Path

HKLM\System\CurrentControlSet\Control\LSA

Type

REG_DWORD

Name

NetJoinLegacyAccountReuse

Value

1

Other values are ignored.

Important guidance for using option 4
Caution: If you choose to set this key to work around these protections, you will leave your environment vulnerable to CVE-2022-38042 unless your scenario is referenced below as appropriate. Do not use this method without confirmation that the Creator/Owner of the existing computer object is a secure and trusted security principal.

It is appropriate to use solution 4 in the following scenarios:

An IT admin with delegated permissions needs to rejoin a computer to the target domain for troubleshooting purposes and the original account creator is a trusted account.

OR

A deployment scenario in which computer accounts are created before using a dedicated service account (such as SCCM or other software) and the domain join is performed by a second dedicated account with delegated domain-join permissions (for example, “This account is allowed to join this computer to the domain”).

Microsoft might remove support for the NetJoinLegacyAccountReuse registry setting in a future update and replace it with an alternative method. This article will be updated if and when such changes take place.

Nonsolutions
Do not add service accounts or provisioning accounts to the Domain Admins security group.

Do not manually edit the security descriptor on computer accounts in an attempt to redefine the ownership of such accounts. While editing the owner will enable the new checks to succeed, the computer account might retain the same potentially risky, unwanted permissions for the original owner unless explicitly reviewed and removed.

Do not add the NetJoinLegacyAccountReuse registry key to base OS images because the key should only be temporarily added and then removed directly after the domain join completes.

The article in reference is; KB5020276—Netjoin: Domain join hardening changes

Advertisement

Windows Update Error 80072F8F

Hi everyone

Today I wanted to talk about a error that can happen in Windows Update.

It’s the error 0x80072F8F.

That error is pointing to an error of the update client. There is two possible causes;

First: The update client is outdated, due possibly to a lack of update done over time. This tend to happen more on older OS like in Windows Server 2012 in example.

To resolve such case you can download a updated client from Microsoft;

Update to Microsoft Update client (https://support.microsoft.com/en-us/topic/update-to-microsoft-update-client-80891e31-29ed-510d-819b-a4c4ee4aa1b7)

After the update just re-run Windows Update to have it work.

Second: An error in the time set inside the computer with a huge offset will cause the update client to fail to get any information. Make sure the computer time is correct.

Wait for printer(s) Mapping on RemoteApp publication

Hi ! Today I wanted to share a small tip if you need to wait for the printer mapping to map before openning a RemoteApp.

This tip is handy in case where the application doesn’t refresh it’s internal list of printer when it start.

Microsoft Office suite is done perfect for that matter, as you can open it, as the list of printer just update when it’s ready to be used.

Some older applications (even newer) are done in more primitive’s way need the printer to be there when it start.

Sage 50 is a good example, and there is some in like FoxPro language, so the tip is still valid today.

The tip is to publish a command file, .cmd or .bat that launch the application, but inside the script you can enter that before launching the app;

@echo off
ping -n 3 127.0.0.1>null

That example will add a 3 second delay before openning the application.

Account lockout available for built-in local administrators

Hi

Today I wanted to share a nice new change Microsoft introduced in the 11 October 2022 cumulative update.

Account lockout are available for built-in local administrators for any network service (RDP, etc..) but not for Console access.

If you want to see where it’s;

It’s a nice way to be able to block password bruteforce tip.

The location is Local Computer Policy\Computer Configuration\Windows Settings\Security Settings\Account Policies\Account Lockout Policies

To note if you use a Windows build 22H2 with the newer update to deploy computer the option will be Enabled by default, and Microsoft will enable the use of complex password at the same time. You can unset the later setting, but it can be a security risk. (Local Computer Policy\Computer Configuration\Windows Settings\Security Settings\Account Policies\Password Policy)

You can read more on the topic are; KB5020282

PacRequestorEnforcement Enforcement date

Hi everyone

I wanted to share that soon enformement of the PAC inside a KRB ticket will be active. (22 October 2022)

If in your enviromment you still see such error;

The KDC encounters a TGT or other evidence ticket without a PAC. This prevents the KDC from enforcing security checks on the ticket.

That can have an impact if you have older domain controler, like a 2008R2 without the extended support option, as such the fix is not available for them.

A registry key exist, but after the 22 October 2022 it will no longer be checked;

To quote the registry key information;

Registry subkey	HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Kdc
Value	PacRequestorEnforcement
Data type	REG_DWORD
Data	1: Add the new PAC to users who authenticated using an Active Directory domain controller that has the November 9, 2021 or later updates installed. When authenticating, if the user has the new PAC, the PAC is validated. If the user does not have the new PAC, no further action is taken. Active Directory domain controllers in this mode are in the Deployment phase.2: Add the new PAC to users who authenticated using an Active Directory domain controller that has the November 9, 2021 or later updates installed. When authenticating, if the user has the new PAC, the PAC is validated. If the user does not have the new PAC, the authentication is denied. Active Directory domain controllers in this mode are in the Enforcement phase.0: Disables the registry key. Not recommended. Active Directory domain controllers in this mode are in the Disabled phase. This value will not exist after the July 12, 2022 or later updates.Important Setting 0 is not compatible with setting 2. Intermittent failures might occur if both settings are used within a forest. If setting 0 is used, we recommend that you transition setting 0 (Disable) to setting 1 (Deployment) for at least a week before moving to setting 2 (Enforcement mode).
Default	1 (when registry key is not set)
Is a restart required?	No

This come from KB5008380—Authentication updates (CVE-2021-42287) patch.

I suggest to quickly remove those older DC if you can, else just make sure you are updated.

Removing Team from autostarting GPO

Today I wanted to share a small tip if you need to remove Team from autostarting when the session start for your users.

The easiest way if you have installed it to your user without the autostart at off is to remove by GPO the run command.

The path is;

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run

com.squirrel.Teams.Teams

At the next logon your user will not see the Teams application loading, which can help on load time 🙂

Upgrading HP Thin Client T420

Hi

Today I wanted to share a tip if someday you want to upgrade the hard disk that Thin Client terminal. As by default it come with a 32 or 64 g HDD.

The terminal come with Windows 10 LTSB 2016 by default, which can be upgraded to LTSC 2019 with added licensing from HP, but it can be hard to do the update with the smaller SSD that the unit has, so the upgrade can be necessary in the end. (I didn’t tried Windows 11 in it)

The interior look that way;

As you can see we have not much room for improvement, but in that specific case I would be using the WiFi pciex connector to connect the new SSD.

I remove the card;

The goal will be to put an adapter;

In the end it look that way;

I recommend to use a small SSD, to be able to close back the case.

After that we can boot, and install the OS inside the SSD 🙂

Windows Azure AD Join missing option

Hi everyone !

Today I wanted to talk a small issue that can happen if you try to join a machine to Azure AD. The issue is the Join Azure AD’s option is just not displayed in the Account’s windows but would work in OOBE.

That would show that way;

The error can come if the computer got no internet access, as it can’t log into Azure at all. The error can come too if you have a Microsoft Account too into the computer, like there;

For that computer I was able to log to an Microsoft Account AND an Azure AD account, but the computer was forced to stay inside a unmanaged state as the option to join the Azure AD was just not there.

To allow the computer to join the Azure AD you need in that case to remove the Microsoft’s account. That will allow you to join the Azure AD, like shown there after the removal of the Microsoft’s account;

After you can join completely;

GPO WMI Filter Trick – No clause and multiple query(s)

Hi everyone !

Today I wanted to share a tip for creating more complex group policy.

WMI filter come handy to target the needed computer in group policy. Adding a NOT LIKE clause like in SQL can be there important.

Creating multiple query help to make a full target.

Keep in note that in multiple query EACH query must be TRUE. So if you do two query, both need to be evaluated as TRUE for the filter to apply.

I will start with the NO clause. If inside your WMI filter you need to use a NO clause please remember that it must be wrote select * … WHERE NOT ….

An example that do a compare on the version;

select * from Win32_OperatingSystem WHERE NOT Version like “10.0.14393%”

Now time to talk on how to make multiple WMI check filter.

I would show an example of how it can be useful; if in example your GPO must target all Windows 10, except a LTSB version. That would look that way;

select * from Win32_OperatingSystem WHERE NOT Version like “10.0.14393%”

select * from Win32_OperatingSystem WHERE Version like “10.%” AND ProductType=”1″