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Q269868: How to Bypass the Authentication Prompt When You Use OWA

Article: Q269868
Product(s): Internet Information Server
Version(s): 3.0,4.0,5.0,5.5
Operating System(s): 
Keyword(s): 
Last Modified: 13-MAY-2002

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The information in this article applies to:

- Microsoft Internet Information Services version 5.0 
- Microsoft Internet Information Server versions 3.0, 4.0 
- Microsoft Outlook Web Access, version 5.5 
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SUMMARY
=======

By default, Outlook Web Access (OWA) forces an incoming client to log on to the
site. In most cases, the IIS computer is configured to use Basic authentication
with SSL. Because OWA forces the client to log on and the server requires Basic
authentication, a dialog box appears to the client to enter his or her
credentials when they attempt to access OWA from the Logon.asp page
(http://servername/exchange/logon.asp).

MORE INFORMATION
================

In instances where a site is required to present authentication at the root of
the site (for example, http://servername), and then go to the Exchange directory
after authentication, it may be necessary to avoid the force of authentication
that OWA initiates. In these situations, when the user tries to log on to the
page (Logon.asp), they are presented with another dialog box to gain
authentication to the OWA mailbox even though they have already provided them
previously.

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  http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

To work around this, you need to modify the following section of code, which is
located in Logonfrm.asp:

  '=======================
  ' MainLogon
  ' Authenticates, and logs on user
  '
  '=======================
   Sub MainLogon
   
   	On Error Goto 0
   
       urlIsNewWindow = Request.QueryString("isnewwindow")
   	CheckSession
   
       ' Logoff if already logged on
   	ClearSession
       SetSessionStuff
   
   	bstrMailbox = Request.QueryString("mailbox")
   <BR/>

   	If Session(CURRENT_MAILBOX) <> bstrMailbox Then
           Session(CURRENT_MAILBOX) = bstrMailbox
   		Response.Buffer = TRUE
   		Response.Status = ("401 Unauthorized")
   		Response.end
   	End If

The section of this code that must be modified is the following "If...then"
statement:

   	If Session(CURRENT_MAILBOX) <> bstrMailbox Then
           Session(CURRENT_MAILBOX) = bstrMailbox
   		Response.Buffer = TRUE
   		'Response.Status = ("401 Unauthorized")
   		'Response.end
   	End If

Both the 'Response.Status = ("401 Unauthorized")' and Response.end statements
need to be remarked (') out. The "401 Unauthorized" error message that is being
set is sent back to the client the first time regardless of whether the client
has already logged on successfully to the Web site. This is the statement that
actually forces the second authentication prompt. The last statement
(Response.end) stops any further code execution from occurring.

The OWA code will still properly assign the variables that are needed to bring up
the appropriate mailbox without another authentication dialog box.

Additional query words: owa authentication 401 force

======================================================================
Keywords          :  
Technology        : kbOutlookSearch kbiisSearch kbiis500 kbiis400 kbiis300 kbOWASearch kbOWA550
Version           : :3.0,4.0,5.0,5.5
Issue type        : kbhowto

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