Identity Impersonation with ASP.NET 4 MVC not working as expected - asp.net-mvc

Question

I am in the process of building a Intranet MVC 4 application for our analysts. The goal is to allow internal users access to this application without having to sign on given they are part of our internal network. When they access the application I want to be able to capture their windows user name and check against the active directory using LDAP and retrieve the department they belong to and display the relevant details on the screen. Based on the advice from different fora, I have chosen Windows Authentication for this application and I was able to test the app successfully running from Visual Studio. The trouble I am having is when I deploy this to our UAT server running IIS 7.5.
<authentication mode="Windows">
</authentication>
<identity impersonate="false" />
This is the current state of my Web.config file. Irrespective of whether impersonate is true or false, the application seems to not capture the windows username of the browser from which the application is accessed. Is
impersonate = true
required for this at all? In the Welcome message on the homepage, I always see the windows user name of the computer where the application is hosted/IIS is running. I have tried a wide variety of ways to capture the Windows User name of the incoming user request.
string name = System.Web.HttpContext.Current.User.Identity.Name;
string name = System.Web.HttpContext.Current.Request.LogonUserIdentity.Name;
string name = System.Security.Principal.WindowsIdentity.GetCurrent().Name;
string name = System.Web.HttpContext.Current.Request.ServerVariables["LOGON_USER"].Name;
etc. I also looked into several other posts here like this. But I am unable to get it to work. I am afraid that I am trying to achieve this by accident rather than really understanding what is going on? Could someone please guide me in the right direction?

Answer 1

No, you misunderstand the purpose of impersonation.
First, Impersonation is no longer supported in IIS 7 or greater running in integrated mode.
Second, the purpose of impersonation is to change the "user" the worker process runs under at runtime, specifically to allow access to filesystem or database resources as that user. It has nothing to do with authentication in general, and is not particularly useful for most web applications.
You want to use Windows Authentication, however you should know that this will only work with Internet Explorer. It will also only work with servers that are joined to your domain, and do not have any intermediary Kerberos authentication issues. (these are often known as "double hop" problems). Other browsers do not, by default, provide Active Directory account information automatically, although some may be configured to allow it to do so, others do not.
If you are using a properly configured server with Windows Authentication, and you are using a browser that supports ActiveDirectory Kerberos ticket passthrough, and there are no network issues that would cause problems with this passthrough, then you can use HttpContext.Current.User.Identity.Name to get the users name.
Don't use LogonName or anything like that, as those will just give you the worker process, not the authenticated users name.