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FIX: Users are prompted to authenticate when the ReturnAuthRequiredIfAuthUserDenied property is set to True, and users are denied access by an "All Users" rule in a Forefront Threat Management Gateway 2010 environment
Article ID: 2518670 - View products that this article applies to.
When Microsoft Forefront Threat Management Gateway (TMG) 2010 denies a request for an authenticated user, the user receives a "502" error message to inform the user that he or she is denied access. Additionally, the user is not prompted to provide alternative credentials.
The ReturnAuthRequiredIfAuthUserDenied property can be set so that when an authenticated user is denied by the TMG policy, the user receives a "407 Proxy Authentication Required" message. This allows for the user to provide alternative credentials.
For more information about the ReturnAuthRequiredIfAuthUserDenied property, visit the following Microsoft Developer Network (MSDN) website:
ReturnAuthRequiredIfAuthUserDenied Property of the IFPCWebListenerProperties InterfaceIf an administrator creates a deny rule that applies to all users and sets the ReturnAuthRequiredIfAuthUserDenied property to True, a user who is denied by such a rule receives a "407 Proxy Authentication Required" message. This behavior occurs even though all users would be denied by this rule. This behavior may not be desired and could lead to unnecessary authentication prompts.
This behavior is by design. But this behavior may not be the desired behavior because an All Users deny rule blocks all users. Additionally, the prompts for alternative credentials does not resolve this issue.
To resolve this issue, install the software update that is described in the following Microsoft Knowledge Base article:
2517957After you apply this software update, run the script that is provided in the "More Information" section on one of the TMG array members to set the SkipReauthWhenNonDefaultRule property to True.
(http://support.microsoft.com/kb/2517957/ )Software Update 1 Rollup 4 for Forefront Threat Management Gateway (TMG) 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This software update introduces a new property, SkipReauthWhenNonDefaultRule. This property provides new behavior. For example, consider the following scenarios.
An administrator creates an All Users rule that denies access to an authenticated user, and the ReturnAuthRequiredIfAuthUserDenied property is set to True. In this scenario, if the SkipReauthWhenNonDefaultRule property is set to True, the user receives a "502" error message and is not prompted to provide alternative credentials.
Scenario 2After you apply this software update, run the following script on one of the TMG array members to set the SkipReauthWhenNonDefaultRule property to True. The default setting for the SkipReauthWhenNonDefaultRule property is False.
The default rule is applied, and the rule denies the request. Also, the ReturnAuthRequiredIfAuthUserDenied property is set to True. In this scenario, the user receives the "407 Proxy Authentication Required" message as expected.
Note This script will only change the behavior when the ReturnAuthRequiredIfAuthUserDenied property is also set to True.
Note To revert to the default behavior, follow these steps:
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/824684/ )Description of the standard terminology that is used to describe Microsoft software updates
Article ID: 2518670 - Last Review: June 15, 2011 - Revision: 1.0