The hotfix that is described in this article supersedes the hotfixes that are described in Microsoft Knowledge Base articles that are listed in this section.
Kerberos uses the Privilege Attribute Certificate (PAC) field of the Kerberos packet to transport Active Directory Group membership. Starting with Windows Server 2012, this also applies to the Active Directory Claims information (Dynamic Access Control) field. If there are many group memberships for the user, and if there are many claims for the user or the device that is being used, these fields can occupy lots of space in the packet.
If a user is a member of more than 120 groups, the buffer that is determined by the MaxTokenSize value is not large enough. Therefore, users cannot authenticate, and they may receive an "out of memory" error message. Before you apply the hotfix that is described in this article, every group that is added to a user account increases this buffer by 40 bytes.
Note In many scenarios, Windows NTLM authentication works as expected. You may not see the Kerberos authentication problem without analysis. However, scenarios in which Group Policy settings are applied may not work as expected.
Note The following Windows versions include a fix for this problem:
- Windows 8
- Windows Server 2012
- Windows 7
- Windows Server 2008 R2
- Windows Server 2003
- Windows Vista
- Windows Server 2008
- Windows XP Professional
Service pack informationTo resolve this problem, obtain the latest service pack for Microsoft Windows 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
Hotfix informationA supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Windows 2000 service pack that contains this hotfix.
To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, go to the following Microsoft website:Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.
Token Size Calculation Windows 2000 to Windows Server 2008 R2If you use the hotfix that is described in this article, you do not have to modify the MaxTokenSize registry value in most cases. However, there are some scenarios in which you have to modify the MaxTokenSize registry value after you apply this hotfix. After you apply this hotfix to all the domain controllers, use the following formula to determine whether you have to modify the MaxTokenSize value:
- d: The number of domain local groups a user is a member of plus the number of universal groups outside the user's account domain that the user is a member of plus the number of groups represented in security ID (SID) history.
- s: The number of security global groups that a user is a member of plus the number of universal groups in a user's account domain that the user is a member of.
- 1200: The estimated value for ticket overhead. This value can vary, depending on factors such as DNS domain name length, client name, and other factors.
When to set the registry entryIf the token size that you calculate by using this formula is less than 12,000 bytes (the default size), you do not have to modify the MaxTokenSize registry value on domain clients. If the value is more than 12,000 bytes, see the following Microsoft Knowledge Base article for a description of how to adjust the MaxTokenSize registry value:
- When you change the MaxTokenSize value, you must restart the computer so that the change is effective.
To use a safe size, you can choose to set MaxTokenSize to 48000, following the discussion about a limitation introduced by HTTP header size later in this article. Depending on what value you are using, you first encounter a problem with Kerberos error events, or IIS HTTP 400 errors.
Known issues that you may encounterKnown issues for the Access Token size:
The Local Security Authority (LSA) service generates the user Access Token from this SID buffer. The hard-coded limit of customer definable SIDs for this token is 1,015, see this KB article:
328889 Users who are members of more than 1,015 groups may fail logon authentication
Therefore, a MaxTokenSize value for more than 1015 effective SIDs is not useful. In the following formula:
Therefore, if you have a MaxTokenSize value of 0x0000FFFF (64K), you may be able to buffer approximately 1600 Domain Local Group SIDs or approximately 8000 Domain Global/Universal Group SIDs. If you use "trusted for delegation" accounts, the buffer requirement for each SID may be doubled. In these scenarios, you can only store approximately 800 Domain Local Group SIDs when a MaxTokenSize value of 64K is used. However, having only Domain Local Group SIDs is not a typical scenario. A value of 64K should be sufficient even for delegation scenarios.
Known issues when using values of MaxTokenSize larger than 65535
Previous versions of this article discussed values of up to 100000 bytes for MaxTokenSize. We have found that versions of SMS Administrator have problems when the MaxTokenSize is 100000 or larger. We have also identified that the IPSEC IKE protocol does not allow a security BLOB to become larger than 66536 bytes, and it would also fail when MaxTokenSize is set to a larger value.
Known issues for the Internet Information Server HTTP receive buffer
The Internet Information Server (IIS) uses a reduced request buffer size to mitigate a denial of service attack vector of 64 KB. However, a Kerberos Ticket in an HTTP request is encoded as Base64 (six bits expanded to eight bits). Additionally, and the Kerberos Ticket is using 133 percent of its original size. Therefore, when the maximum buffer size is 64 KB in IIS, 48 KB of a Kerberos Ticket can be used.
If you set the MaxTokenSize registry entry to a value that is larger than 48000, and the buffer space is used for SIDs, an IIS error may occur. However, if you set the MaxTokenSize registry entry to 48000, a Kerberos error may occur.
For more information about IIS buffer sizes, click the following article numbers to view the articles in the Microsoft Knowledge Base:
Windows Server 2012 changesWindows Server 2012 introduced the following changes to the considerations about this buffer:
- The default for MaxTokenSize changes to 48,000 bytes.
- There is a new scheme for compressing the sids in the PAC.
- Dynamic Access Control adds Active Directory Claims to the Ticket. Therefore, calculating the expected ticket sizes is no longer straightforward. The expectation is that tickets that are issued by Windows Server 2012 domain controllers are smaller than the same tickets that are issued from older operating system versions. Claims add to the ticket size. However, after Windows Server 2012 file servers are using claims broadly, you can expect to phase out a significant number of your groups that control file access to trim ticket sizes.
For more information about Windows Server 2012 changes, go to the following Microsoft TechNet website:
Examples of problems when the ticket size is exceededFor more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
Because you may have cross-domain logon scenarios in your forest, the value should be set forest-wide on all Windows-based systems. Therefore, we recommend that the maximum value for the MaxTokenSize value be 64K.
Important On SQL Server clients, you may receive the following error message when this problem occurs: