I have a SharePoint 2010 web part and WCF service deployed to a web application using Kerberos authentication. The service was developed based on the walkthrough
from MSDN with the only difference that ClientCredentialType = HttpClientCredentialType.Windows so that Kerberos is used.
The web application is being reverse-published through ISA. However we've never had an issue with this before. We've also disabled the loopback check on the server.
When the web part calls the service, a 401 error occurs with the following exception message:
The HTTP request is unauthorized with client authentication scheme 'Negotiate'. The authentication header received from the server was 'NTLM'.
I configured Fiddler on the web application running the web part and found that both Kerberos and NTLM authentication headers are being returned:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: Negotiate oXsweaADCgEBoQsGCSqGSIL3EgECAqJlBGNgYQYJKoZIhvcSAQICAwB+UjBQoAMCAQWhAwIBHqQRGA8yMDEwMDkxNDA1MjY1NlqlBQIDDgespgMCASmpDBsKREVDUy5MT0NBTKoXMBWgAwIBAaEOMAwbCnNwX3dlYmFwcDE=
Date: Tue, 14 Sep 2010 05:26:56 GMT
Why then is the Kerberos authentication not a
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