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NTLM and Kerberos Authentication

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Default NTLM authentication and Kerberos authentication use the Microsoft Windows user credentials associated with the calling application to attempt authentication with the server. When using non-default NTLM authentication, the application sets the authentication type to NTLM and uses a NetworkCredential object to pass the user name, password, and domain to the host, as shown in the following example.

Dim myUri As String = "http://www.contoso.com/"  
Using handler As New HttpClientHandler()
    With handler
        .Credentials = New NetworkCredential(UserName, SecurelyStoredPassword, Domain)
    End With
    Using client As New HttpClient(handler)
        Dim result As String = Await client.GetStringAsync(myUri)
        ' Do Other Stuff...
    End Using
End Using

string myUri = "http://www.contoso.com/";
using HttpClientHandler handler = new()
{
    Credentials = new NetworkCredential(UserName, SecurelyStoredPassword, Domain),
};
using HttpClient client = new(handler);
string result = await client.GetStringAsync(myUri);
// Do Other Stuff...

Applications that need to connect to Internet services using the credentials of the application user can do so with the user's default credentials, as shown in the following example.

Dim myUri As String = "http://www.contoso.com/"  
Using handler As New HttpClientHandler()
    With handler
        .Credentials = CredentialCache.DefaultCredentials
    End With
    Using client As New HttpClient(handler)
        Dim result As String = Await client.GetStringAsync(myUri)
        ' Do Other Stuff...
    End Using
End Using 

string myUri = "http://www.contoso.com/";
using HttpClientHandler handler = new()
{
    Credentials = CredentialCache.DefaultCredentials,
};
using HttpClient client = new(handler);
string result = await client.GetStringAsync(myUri);
// Do Other Stuff...

The negotiate authentication module determines whether the remote server is using NTLM or Kerberos authentication, and sends the appropriate response.

Note

NTLM authentication does not work through a proxy server.

See also