User accounts are not authenticated by the domain controllers that are in the child domain if "The other domain supports Kerberos AES Encryption" check box is selected

Consider the following scenario:

• You set the forest functional level of an Active Directory forest to Windows Server 2003.
• You set the domain functional level of a parent domain to Windows Server 2003. The parent domain contains one or more domain controllers that are running Windows Server 2008.
• You set the domain functional level of a child domain to Windows Server 2008. The child domain contains one or more domain controllers that are running Windows Server 2008.
• You install hotfix 959517 or Windows Server 2008 Service Pack 2 (SP2) on all these domain controllers that are running Windows Server 2008.
• You click to select The other domain supports Kerberos AES Encryption check box for the trust relationship between the parent domain and the child domain.

In this scenario, the user accounts that are in the parent domain are not authenticated by the domain controllers in the child domain. Therefore, these user accounts cannot access resources in the child domain.

Additionally, the following event is logged in the System log on a domain controller that is in the child domain:

Source: Microsoft-Windows-Kerberos-Key-Distribution-Center
Date: <date>
Event ID: 18
Task Category: None
Level: Error
Keywords: Classic
User: N/A
Computer: <computer>
Description: During TGS processing, the KDC was unable to verify the signature on the PAC from <the partent domain name>. This indicates the PAC was modified.

This issue occurs because the Windows Server 2008-based Key Distribution Center (KDC) uses an incorrect key type to verify the privilege attribute certificate (PAC) in the scenario that is described in the "Symptoms" section.

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

To apply this hotfix, your computer must be running Windows Server 2008 or Windows Server 2008 Service Pack 2 (SP2). Additionally, the Active Directory Domain Service (AD DS) role must be installed.

For more information about how to obtain a Windows Server 2008 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix replaces the previously released hotfix 959517

File information

The English (United States) version of this hotfix installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.

Windows Server 2008 file information notes

• The files that apply to a specific product, SR_Level (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table.

  Version	Product	SR_Level	Service branch
  6.0.600 1 . 22xxx	Windows Server 2008	SP1	LDR
  6.0.600 2 . 22xxx	Windows Server 2008	SP2	LDR

• Service Pack 1 is integrated into the release version of Windows Server 2008. Therefore, RTM milestone files apply only to Windows Vista. RTM milestone files have a 6.0.0000.xxxxxx version number.
• The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information for Windows Server 2008" section. MUM and MANIFEST files, and the associated security catalog (.cat) files, are extremely important to maintaining the state of the updated component. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows Server 2008

For all supported x64-based versions of Windows Server 2008

Workaround for Windows Server 2008

To work around this issue, click to clear The other domain supports Kerberos AES Encryption check box for the parent and child trust.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

To select or clear The other domain supports Kerberos AES Encryption check box, follow these steps:

1. Open the Active Directory Domains and Trusts Microsoft Management console (MMC) snap-in on a domain controller that is in the parent domain.
2. Right-click the domain name of this parent domain to open the Properties dialog box.
3. On the Trusts tab, select the trust between the parent domain and the child domain, and then click Properties.
4. Click to select or clear The other domain supports Kerberos AES Encryption option check box.
5. Click OK, and then restart the domain controllers that are in both domains to apply the setting.

For more information, click the following article number to view the article in the Microsoft Knowledge Base:
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:

Additional file information

Additional file information for Windows Server 2008

Additional files for all supported x86-based versions of Windows Server 2008

Additional files for all supported x64-based versions of Windows Server 2008