Microsoft KB Archive/927265

= Authentication fails when client computers use Internet Explorer 7 to authenticate with an upstream ISA Server computer through a downstream ISA Server computer that does not require authentication =

Article ID: 927265

Article Last Modified on 12/4/2007

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APPLIES TO


 * Microsoft Internet Security and Acceleration Server 2006 Standard Edition
 * Microsoft Internet Security and Acceleration Server 2006 Enterprise Edition
 * Microsoft Internet Security and Acceleration Server 2004 Standard Edition
 * Microsoft Internet Security and Acceleration Server 2004 Enterprise Edition

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SYMPTOMS
Consider the following scenario:
 * You configure an upstream Microsoft Internet Security and Acceleration (ISA) Server computer that requires authentication.
 * You configure a downstream ISA Server computer that does not require authentication.
 * Client computers that are connected to the downstream ISA Server computer are running Windows Internet Explorer 7.

In this scenario, the client computers cannot authenticate with the upstream ISA Server computer.



CAUSE
Client computers that are running Internet Explorer 7 obtain a Kerberos ticket that is valid for authentication with the downstream server. However, this Kerberos ticket is not validated by the authenticating upstream ISA Server computer.

Specifically, when the upstream ISA Server computer requests authentication, the client computer obtains a Kerberos ticket for the downstream server. This Kerberos ticket is valid for authentication with the downstream ISA Server computer. This ticket cannot be used to authenticate with the upstream ISA Server computer. When the Kerberos ticket is presented to the upstream ISA Server computer, the upstream ISA Server computer cannot validate the ticket. Therefore, authentication fails.

Notes
 * The downstream ISA Server computer is the proxy server with which the client computer is communicating.
 * Internet Explorer 7 includes support for Kerberos authentication against proxy servers.

NTLM authentication is the alternative authentication method for instances when Kerberos authentication fails. However, the client computer does not use NTLM authentication because the client computer has successfully obtained a Kerberos ticket for the proxy server.



Hotfix information
A supported hotfix is now 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 this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next service pack that contains this hotfix.

To resolve this problem, submit a request to Microsoft Online Customer Services to obtain the hotfix. To submit an online request to obtain the hotfix, visit the following Microsoft Web site:

http://go.microsoft.com/?linkid=6294451

Note If additional issues occur or 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. To create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Prerequisites
The computer must be running ISA Server 2004 Service Pack 2 (SP2) to apply the ISA Server 2004 version of this hotfix.

Restart requirement
After you apply this hotfix, the hotfix will restart ISA Server services.

Hotfix replacement information
This hotfix does not replace any other hotfixes.

File information
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.

Post-hotfix installation information
After you apply this hotfix, you must run the following Microsoft Visual Basic script to configure the upstream ISA Server computer to return NTLM authentication headers only when Windows Integrated authentication is used. To run this script, follow these steps:  Click Start, point to Programs, point to Accessories, and then click Notepad.  Copy the following code, and then paste it into Notepad.

 ' ' Copyright (c) Microsoft Corporation. All rights reserved. ' THIS CODE IS MADE AVAILABLE AS IS, WITHOUT WARRANTY OF ANY KIND. THE ENTIRE ' RISK OF THE USE OR THE RESULTS FROM THE USE OF THIS CODE REMAINS WITH THE ' USER. USE AND REDISTRIBUTION OF THIS CODE, WITH OR WITHOUT MODIFICATION, IS ' HEREBY PERMITTED. 

 ' This script sets authentication schemes that ISA will return for Integrated authentication. 

const USE_ONLY_NTLM_FOR_WINDOWS_AUTH_default = 0 ' Use Negotiate and Kerberos, too. const USE_ONLY_NTLM_FOR_WINDOWS_AUTH_Always = 1

Const SE_VPS_GUID = &quot;{143F5698-103B-12D4-FF34-1F34767DEabc}&quot; Const SE_VPS_NAME = &quot;UseOnlyNTLMForWindowsAuth&quot; Const SE_VPS_VALUE = 1

Sub SetValue

' Create the root object. Dim root ' The FPCLib.FPC root object Set root = CreateObject(&quot;FPC.Root&quot;)

'Declare the other objects that are needed. Dim array      ' An FPCArray object Dim VendorSets ' An FPCVendorParametersSets collection Dim VendorSet  ' An FPCVendorParametersSet object

' Get references to the array object ' and to the network rules collection. Set array = root.GetContainingArray Set VendorSets = array.VendorParametersSets

On Error Resume Next Set VendorSet = VendorSets.Item( SE_VPS_GUID )

If Err.Number <> 0 Then Err.Clear

' Add the item. Set VendorSet = VendorSets.Add( SE_VPS_GUID ) CheckError WScript.Echo &quot;New VendorSet added... &quot; & VendorSet.Name

Else WScript.Echo &quot;Existing VendorSet found... value- &quot; & VendorSet.Value(SE_VPS_NAME) End If

if VendorSet.Value(SE_VPS_NAME) <> SE_VPS_VALUE Then

Err.Clear VendorSet.Value(SE_VPS_NAME) = SE_VPS_VALUE

If Err.Number <> 0 Then CheckError Else VendorSets.Save false, true CheckError

If Err.Number = 0 Then WScript.Echo &quot;Done with &quot; & SE_VPS_NAME & &quot;, saved!&quot; End If       End If    Else WScript.Echo &quot;Done with &quot; & SE_VPS_NAME & &quot;, no change!&quot; End If

End Sub

Sub CheckError

If Err.Number <> 0 Then WScript.Echo &quot;An error occurred: 0x&quot; & Hex(Err.Number) & &quot; &quot; & Err.Description Err.Clear End If

End Sub

SetValue  Save this Notepad file as .vbs. Double-click the .vbs file to run the script.

Note To revert to the default time-out value, change the SE_VPS_VALUE to 0, and then rerun the script.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
An additional problem may occur after you enable this hotfix on the upstream server. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

938465 Error message when you try to access Web sites through a downstream server after you enable hotfix 927265 on an upstream server that is running ISA Server 2004: &quot;502 Proxy Error&quot;

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

824684Description of the standard terminology that is used to describe Microsoft software updates

Keywords: kbbug kbfix kbqfe kbpubtypekc kbexpertiseadvanced kbhotfixserver KB927265

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