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Authentication failure from non-Windows NTLM or Kerberos servers
Article ID: 976918 - View products that this article applies to.
Important This is a rapid publishing article. For more information, refer to the “Disclaimer” section.
This article provides a fix for several authentication failure issues in which NTLM and Kerberos servers cannot authenticate Windows 7 and Windows Server 2008 R2-based computers. This is caused by differences in the way that Channel Binding Tokens are handles. For detailed information, see the “Symptoms,” “Cause,” and “Resolution” sections of this article.
To download the fix for this issue, click the View and request hotfix downloads link that is located on the upper-left of the screen.
Windows 7 and Windows Server 2008 R2 support Extended Protection for Integrated Authentication which includes support for Channel Binding Token (CBT) by default.
You may experience one or more of the following symptoms:
Windows 7 and Windows Server 2008 R2 support Extended Protection for Integrated Authentication. This feature enhances the protection and handling of credentials when authenticating network connections using Integrated Windows Authentication (IWA).
This is ON by default. When a client attempts to connect to a server, the authentication request is bound to the Service Principal Name (SPN) used. Also when the authentication takes place inside a Transport Layer Security (TLS) channel, it can be bound to that channel. NTLM and Kerberos provide additional information in their messages to support this functionality.
Also, Windows 7 and Windows 2008 R2 computers disable LMv2.
For failures where non-Windows NTLM or Kerberos servers are failing when receiving CBT, check with the vendor for a version which handles CBT correctly.
For failures where non-Windows NTLM servers or proxy servers require LMv2, check with the vendor for a version which supports NTLMv2.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
To control the extended protection behavior, create the following registry subkey:
Key Name: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\LSAFor Windows clients that support channel binding that are failing to be authenticated by non-Windows Kerberos servers that do not handle the CBT correctly:
Value Name: SuppressExtendedProtection
What is CBT (Channel Binding Token)?Channel Binding Token (CBT) is a part of Extended Protection for Authentication. CBT is a mechanism to bind an outer TLS secure channel to inner channel authentication such as Kerberos or NTLM.
CBT is a property of the outer secure channel used to bind authentication to the channel.
Extended protection is accomplished by the client communicating the SPN and the CBT to the server in a tamperproof fashion. The server validates the extended protection information in accordance with its policy and rejects authentication attempts for which it does not believe itself to have been the intended target. This way, the two channels become cryptographically bound together.
Extended protection is now supported in Windows XP, Windows Vista, Windows Server 2003 and Windows Server 2008.
For more information about extended protection for authentication in Windows, visit the following Microsoft Web site:
Information about extended protection for authentication in Windows
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Article ID: 976918 - Last Review: February 12, 2011 - Revision: 2.0