Unable to get windows authentication to work through local IIS

Question

So I've created a new ASP.NET MVC project using the intranet template. web.config contains the appropriate values (e.g. <authentication mode="windows"/>).

If I fire up the web app using the VS webserver, it all looks fine - the page shows my Windows domain and username and all. However, this works in Opera and Safari as well as IE and FF, which says to me it's not using Windows auth at all (since to the best of my knowledge this doesn't work in any browser except IE/FF).

Next step is to get it working through local IIS. I create a hosts file entry pointing www.mysite.mydomain to 127.0.0.1. So in IIS I create website with a binding to www.mysite.mydomain and enable Windows authentication and disable anonymous authentication.

I have set up IE and FF to enable Windows auth as follows:

IE

1. Add URL to intranet group
2. Ensure Windows auth is enabled in the advanced settings

FF

Put 'www.mysite.mydomain' into network.automatic-ntlm-auth.trusted-uris config setting.

But when I dial up www.mysite.mydomain in IE / FF I get a login prompt. Interestingly, even when I type in my Windows login here, it still fails and shows me the login prompt again.

We don't have active directory here but my understanding is that it should work fine with a local account.

I can't think of anything else I need to do. Any suggestions?

Edit: we've recently switched to using Active Directory and the problem remains.

Edit: when I cancel the login prompt, I get taken to an 'IIS 7.5 Detailed Error' page with the following information:

HTTP Error 401.2 - Unauthorized You are not authorized to view this page due to invalid authentication headers.**

Answer 1

You have to whitelist a domain specified in the hosts file in order for windows authentication to work:

1. Click Start, click Run, type regedit, and then click OK.
2. In Registry Editor, locate the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters
3. Right-click Parameters, click New, and then click DWORD (32-bit) Value.
4. Type DisableStrictNameChecking and press ENTER.
5. Double-click the DisableStrictNameChecking registry value and type 1 in the Value data box, click OK
6. In Registry Editor, locate and then click the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0
7. Right-click MSV1_0, point to New, and then click Multi-String Value.
8. Type BackConnectionHostNames, and then press ENTER.
9. Right-click BackConnectionHostNames, and then click Modify.
10. In the Value data box, type the host name or the host names for the sites that are on the local computer, and then click OK.
11. Quit Registry Editor, and then restart the IISAdmin service.

NOTE: The original Microsoft KB links on this answer were broken and have been removed. This article provided the instructions for setting DisableStrictNameChecking.

Answer 2

I recently spent three days trying to solve the same problem and it drove me crazy. It was happening on a load-balanced setup where one of the servers was authenticating correctly while the other failed. Investigating the problem - and eventually solving it - it turned out to be unrelated to the load-balanced environment, it could happen with any server when authenticating using Windows Authentication and the server is called with a name other than the one recognized by Active Directory

1. Enable Kerberos logging

To correctly diagnose your issue, you will need to enable Kerberos logging on the machine hosting your IIS site. To do so, add the following registry entry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

Add Registry Value LogLevel with ValueType REG_DWORD and value 0x1.

Once you turn on logging, then you try to authenticate, you will get errors logged in your Windows Application Log. You can ignore the error KDC_ERR_PREAUTH_REQUIRED (this is just part of the handshake) but if you get the error KDC_ERR_C_PRINCIPAL_UNKNOWN that means your AD controller doesn't recognize your server therefore you need to follow the steps below.

2. KDC_ERR_C_PRINCIPAL_UNKNOWN

if you're getting KDC_ERR_C_PRINCIPAL_UNKNOWN, that means the name "mysite.mydomain.com" is different from how the AD recognizes your machine so it's unable to provide a valid kerberos ticket. In that case, you need to register a Service Principal Name (SPN) for " 'www.mysite.mydomain" on the AD.

On your AD controller, run this command - you will need Domain Admin privilege:

Setspn -A HTTP/mysite.mydomain YOUR_MACHINE_HOSTNAME

3. Use a custom identity for your Application pool

Finally, make you Application pool use a custom account that belongs to the Active Directory instead of using NetworkService. This can be done in advanced settings of your application pool.

and .. voila.

---

Notes: The problem could (unlikely) be related to having multiple SPNs registered to the same machine, in that case you will need to run a command to remove duplicate SPNs, but I doubt this is the case. Also try adding a different binding to your site (that doesn't use a custom name) something like htttp://localhost:custom_port_number and see if authentication works. If it works, this is an extra indication that you're suffering from the same problem I had.

Answer 3

Did you try putting the domain in front of the user name?

DOMAIN\username

If you don't have a domain account, try prefixing your username with the machine name:

MYCOMPUTER\myusername

Answer 4

You should check to see if you have Windows Authentication installed/enabled. That may sound weird but in IIS 7 you have to install and enable the various authentication methods. Check out http://support.microsoft.com/kb/942043/ for more info, see quoted section below.

Cause 1
The Web application is configured to use Integrated Windows authentication. However, the Windows Authentication feature is not turned on. Or, the Integrated Windows authentication native module section of the ApplicationHost.config file or of the Web.config file is not valid. To resolve this problem, see Resolution 1.

Original
Usually when you try to view an asp.net web page hosted on IIS and receive a login prompt it doesn't mean your credentials weren't received or that you aren't authenticated. What it means is that the account that your website is running under doesn't have the right permissions to work with the files.

In IIS 6 and 7 you can easily change the user account that your app pool runs under. Try changing the app pool identity to an account with more access specifically designed for this. Or if you want to stick with the existing account (IUSR_? Network Service?) you can grant that account more permissions on the directory where your website is stored.

This article is specifically targeted at BizTalk but has almost no references to it and focuses on troubleshooting permissions issues with IIS and app pools: http://msdn.microsoft.com/en-us/library/aa954062.aspx

Answer 5

Why local IIS? Can you use local IIS Express?

If so, try this. It seems that IIS Express by default has Windows Authentication set to false.

Change

<windowsAuthentication enabled="false">

to "true" in applicationhost.config file (under 'C:\Users[Profile]\Documents\IISExpress\config' folder). This works for me.

Answer 6

To ensure that IIS uses Windows Authentication, I think you should try to turn of other authtentication methods. If Anonymous Authentication is enabled, Windows authentication will not work. You can also read this Microsoft Support Article which describes IE and IIS requirements in details.

Answer 7

I got this error when I enabled Windows authentication. I wanted to authorize the user based on Windows login and there is no login page in my application.

I got the error fixed by adding the below in my Web config file. Under the tag system.web, I changed authentication mode="None" to authentication mode="Forms".

Under the tag appSettings, I added add key="owin:AutomaticAppStartup" value="false"

Answer 8

After reading the answer of Espen Burud, I solved my problem by changing in the root's web.config:

<allow users="*" />

to

<deny users="?" />

The page that needs Windows Authentication is not in the root, but in a sub directory with its own web.config with deny users ? but that did not make Windows Authentication working. Apparently, you need to deny users in the root for that to work.

The IIS config has Anonymous Authentication enabled; that did not matter. After the above change of web.config, Windows Authentication worked.

Answer 9

For Dot Net Core 2.2 and running on IIS, I was having issues with 401.2 Unauthorized when I would check the Enable Windows Authentication within my application. It was a exceedingly simple test website that did basically nothing, just to try and get windows authentication to work. I finally got the auth to work, and here's what you'll need:

Within Startup ConfigureServices:

services.AddAuthentication(IISDefaults.AuthenticationScheme);

Open the application's Properties, click Debug option on the left and make sure you check Enable Windows Authentication.

But here's the kicker that I had forgotten... Configure your system to have Windows Authentication installed on IIS. This was never setup on my machine, and regardless what I did, I would always get a 401 unauthorized error. After installing this (Win 10, IIS v10.0.18362.1) I now get a login prompt. This isn't exactly what I need at this point, but at least it's not the unauthorized error. Good luck and hopefully this helps.