Re: Delegation in ASP.NET

From: Ken Schaefer (kenREMOVE_at_THISadOpenStatic.com)
Date: 09/14/04 

Date: Tue, 14 Sep 2004 13:21:35 +1000

Hi,

If the website is in the Internet security zone, Internet Explorer will not
use Kerberos (it will not attempt Kerberos authentication). Kerberos
authentication requires the browser to be able to access both the
webserver -and- the KDC (which are domain controllers in the Windows world),
and this typically isn't possible in an internet scenario. So, IE doesn't
attempt something that is most likely going to fail.

Solution? Add sites that use fully qualified domain names or IP addresses to
IE's Intranet zone. Also, ensure that you have an SPN registered for this
address.

Cheers
Ken

"matthewt" <matthewt@nospam.nospam> wrote in message
news:91175990-829B-44FD-BB4B-78BC757DEE78@microsoft.com...
> Hi,
>
> As the title suggests I have a question about delegation in ASP.NET.
>
> We have an ASP.NET application running on a web server which requires
> clients to authenticate via Windows Integrated authentication. We're
> running
> in a Win2K native-mode domain and the clients are IE6 so we should be
> using
> Kerberos to authenticate.
>
> At some points the application needs to send an email on behalf of the
> client; this it achieves by impersonating the remote user and using WebDAV
> to
> talk to the exchange server running on the DC (which is a physically
> separate
> box from the web server).
>
> This is working in the main and the credentials appear to flow from the
> browser, through the web-app to the exchange server.
>
> However, it only hangs together with a certain set of *browser* settings
> :s
>
> If the site is configured to live in a zone (e.g. Intranet or Trusted
> Sites
> etc.) that has either of the "automatic logon..." options in the IE custom
> security level dialog selected then all is well.
>
> As soon as this isn't true and we manually enter the credentials when
> prompted, we authenticate with the web-server OK, but then the ASP.NET app
> can't authenicate with the exchange box on the client's behalf (its as if
> we're back to impersonation rather than delegation).
>
> We believe that we've all the accounts are correctly configured for
> delegation (i.e. user accounts are *not* marked as sensitive, app account
> is
> marked as trusted for delegation, machine account trusted for delegation).
>
> Does anyone have any ideas about what this browser option is actually
> doing
> that makes the whole thing work?
>
> The application only supports windows integrated authentication so it
> can't
> be "falling back" to basic - is it falling back to NTLM though?
>
> Any help will be much appreciated.
>
> cheers,
> Matt
>

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