Microsoft KB Archive/885436

= You may be continually prompted to authenticate in Internet Explorer 6 when you browse Web sites that you already logged on to in Windows Server 2003 =

Article ID: 885436

Article Last Modified on 11/15/2007

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APPLIES TO


 * Microsoft Internet Explorer 6.0
 * Microsoft Internet Explorer 6.0 Service Pack 1, when used with:
 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)

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Important This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry



SYMPTOMS
When you connect through a caching ISA Proxy that has anonymous access, and you try to perform NTLM authentication with an Microsoft Internet Information Services (IIS) 5.0-based Web server, Microsoft Internet Explorer 6 may not automatically authenticate with NTLM pre-authorization (PreAuth). Instead, you may be continually prompted to authenticate.



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
No prerequisites are required to install this hotfix.

Restart requirement
You do not have to restart your computer after you apply this hotfix.

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

Hotfix 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 tool in Control Panel.

Windows Server 2003, 32-Bit Edition
  Date         Time   Version       Size     File name --   23-Sep-2004  22:06  6.0.3790.216  625,152  Wininet.dll

Windows Server 2003, 64-Bit Edition
  Date         Time   Version       Size       File name     Platform ---  23-Sep-2004  20:02  6.0.3790.216  1,503,744  Wininet.dll   IA-64 23-Sep-2004 20:06  6.0.3790.216    625,152  Wwininet.dll  x86

Additional steps
This hotfix uses the following registry information to determine how to treat the socket during a 401 Authentication. To use the hotfix, set the registry value to 0. To turn off the hotfix and to revert to the original behavior, set the value to 1. By default, the installation of this hotfix package sets the value to 0.

To set the registry value to 0, follow these steps:

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.  Exit Internet Explorer 6.0. Click Start, click Run, type regedit, and then click OK. Locate and then click to select the following registry subkey:

 On the Edit menu, point to New, and then click DWORD Value. Type ReleaseSocketDuring401Auth, and then press ENTER. Right-click ReleaseSocketDuring401Auth, and then click Modify.</li> In the Value data box, type 0, and then click OK.</li> On the File menu, click Exit to exit Registry Editor.</li></ol>

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WORKAROUND
To work around this problem, edit all the &quot;401&quot; response pages in your IIS deployment so they are larger than 1,460 bytes. 1,460 bytes is the size of one TCP packet.

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

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MORE INFORMATION
If the &quot;401&quot; response page content is smaller than 1,460 bytes, Internet Explorer closes the current connection and tries to reuse a previous connection from the keep-alive pool for that server. Because the ISA proxy, or any other proxy, has closed the related connection between the ISA proxy and the IIS server, you cannot reuse the Internet Explorer connection. Therefore, Internet Explorer produces an authentication prompt.

When the &quot;401&quot; response page is larger than 1,460 bytes, Internet Explorer must maintain the current connection so that it can drain the socket of all pending data. This behavior causes Internet Explorer to reuse this socket for the later NTLM authentication traffic. Therefore, the connection works seamlessly.

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