28 February 2011

Fixing IIS Error 401.2 - Unauthorized Access

I have developed several applications in Ext JS and recently noticed that all my server calls for a grid made two calls to the server. The first call was a fail, but the second call succeeded. This happens so quickly that the user is not even aware of the issue, but I wanted to track it down anyway.

I examined the HTTP traffic using Fiddler, and found this error in the header of the failed call:

You are not authorized to view this page
You do not have permission to view this directory or page using the credentials that you supplied because your Web browser is sending a WWW-Authenticate header field that the Web server is not configured to accept.

Please try the following:

  • Contact the Web site administrator if you believe you should be able to view this directory or page.
  • Click the Refresh button to try again with different credentials.
HTTP Error 401.2 - Unauthorized: Access is denied due to server configuration.
Internet Information Services (IIS)


Technical Information (for support personnel)

  • Go to Microsoft Product Support Services and perform a title search for the words HTTP and 401.
  • Open IIS Help, which is accessible in IIS Manager (inetmgr),
    and search for topics titled About Security, Authentication, and About Custom Error Messages.

This problem was happening in IIS6 on Win2K3, but I actually observed it happening on II7 on Win2K8 R2. I found a clue on this website, which recommended changing the order of IIS's method for authentication. Unfortunately for me, this post talked about a UI fix that does not appear to be valid for my version of IIS.

Changing the order of authentication is the answer however, although it needs to be done directly in the ApplicationHost.config file. The fix for this issue is as follows:
  1. Find the ApplicationHost.config file in C:\Windows\System32\inetserv\config.
  2. Copy file to new folder.
  3. Open config file in Notepad. Search for NTLM. You will find it in the windowsAuthentication/providers section of the file. The value "Negotiate" will be listed ABOVE NTLM
  4. Copy the entire XML line so that NTLM is the first on the list of providers.
  5. Restart the World Wide Web Publishing service. Once that is done, the issue goes away.