The "401 Authentication Required" response that is sent by a Web site is dropped when you use ISA Server 2004 or ISA Server 2006 as a Web proxy

Symptoms

Consider the following scenario:

• You use Microsoft Internet Security and Acceleration (ISA) Server 2004 or ISA Server 2006 as a Web proxy to access a Web site.

• You perform a POST operation on the Web site.

• The Web site sends a "401 Authentication Required" response to the client.

However, ISA Server drops the "401 Authentication Required" response instead of forwarding the response to the client. This problem may cause the Web access attempt to fail. For example, when you try to upload a large file to the Web site, the upload operation may time out.

Resolution

To resolve this problem, follow these steps:

1. If you are running ISA Server 2004, apply the hotfix package that is described in the following Microsoft Knowledge Base article:

   940709 Description of the ISA Server 2004 hotfix package: July 25, 2007
   
   
   If you are running ISA Server 2006, apply the last ISA Server service pack. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
   
   

   954258 How to obtain the latest Internet Security and Acceleration (ISA) Server 2006 service pack
   
   

2. Start Notepad.

3. Copy the following code, and then paste it into Notepad.

   Const SE_VPS_GUID = "{143F5698-103B-12D4-FF34-1F34767DEabc}"
   Const SE_VPS_NAME = "AllowPrematureServerResponse"
   Const SE_VPS_VALUE = true
   
   Sub SetValue()
   
       ' Create the root object.
       Dim root  ' The FPCLib.FPC root object
       Set root = CreateObject("FPC.Root")
   
       '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 "New VendorSet added... " & VendorSet.Name
   
       Else
           WScript.Echo "Existing VendorSet found... value- " &  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 "Done with " & SE_VPS_NAME & ", saved!"
               End If
           End If
       Else
           WScript.Echo "Done with " & SE_VPS_NAME & ", no change!"
       End If
   
   End Sub
   
   Sub CheckError()
   
       If Err.Number <> 0 Then
           WScript.Echo "An error occurred: 0x" & Hex(Err.Number) & " " & Err.Description
           Err.Clear
       End If
   
   End Sub
   
   SetValue
   

4. Save the file as a Microsoft Visual Basic script file by using the .vbs file name extension. For example, use the following name to save the file:

   AllowPrematureServerResponse.vbs

5. Start a command prompt, change to the location at which you saved the AllowPrematureServerResponse.vbs file, and then run the following command:

   cscript AllowPrematureServerResponse.vbs

Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information

For more information about how to install ISA Server hotfixes and updates, click the following article number to view the article in the Microsoft Knowledge Base:

885957 How to install ISA Server hotfixes and updates