Build a web application using OpenID Connect with AD FS 2016

02/22/2018
3 minutes to read
Contributors

Applies To: Windows Server 2016

Building on the initial Oauth support in AD FS in Windows Server 2012 R2, AD FS 2016 introduces support for using the OpenId Connect sign-on.

Pre-requisites

The following are a list of pre-requisites that are required prior to completing this document. This document assumes that AD FS has been installed and an AD FS farm has been created.

GitHub client tools
AD FS in Windows Server 2016 TP4 or later
Visual Studio 2013 or later.

Create an Application Group in AD FS 2016

The following section describes how to configure the application group in AD FS 2016.

Create Application Group

In AD FS Management, right-click on Application Groups and select Add Application Group.
On the Application Group Wizard, for the name enter ADFSSSO and under Standalone applications select the Server application or Website template. Click Next.
Copy the Client Identifier value. It will be used later as the value for ida:ClientId in the applications web.config file.
Enter the following for Redirect URI: - https://localhost:44320/. Click Add. Click Next.
On the Configure Application Credentials screen, place a check in Generate a shared secret and copy the secret. Click Next
On the Summary screen, click Next.
On the Complete screen, click Close.
Now, on the right-click the new Application Group and select Properties.
On the ADFSSSO Properties click Add application.
On the Add a new application to Sample Application select Web API and click Next.
On the Configure Web API screen, enter the following for Identifier - https://contoso.com/WebApp. Click Add. Click Next.
On the Choose Access Control Policy screen, select Permit everyone and click Next.
On the Configure Application Permissions screen, make sure openid is selected and click Next.
On the Summary screen, click Next.
On the Complete screen, click Close.
On the Sample Application Properties click OK.

Download and Modify MVP App to Authenticate via OpenId Connect and AD FS

This section discusses how to download the sample Web API and modify it in Visual Studio. We will be using the Azure AD sample that is here.

To download the sample project, use Git Bash and type the following:

git clone https://github.com/Azure-Samples/active-directory-dotnet-webapp-openidconnect

AD FS OpenID

To Modify the app

Open the sample using Visual Studio.
Compile the app so that all of the missing NuGets are restored.

Open the web.config file. Modify the following values so the look like the following:

<add key="ida:ClientId" value="8219ab4a-df10-4fbd-b95a-8b53c1d8669e" />  
<add key="ida:ADFSDiscoveryDoc" value="https://adfs.contoso.com/adfs/.well-known/openid-configuration" />  
<!--<add key="ida:Tenant" value="[Enter tenant name, e.g. contoso.onmicrosoft.com]" />      
<add key="ida:ResourceID" value="https://contoso.com/WebApp"  
<add key="ida:AADInstance" value="https://login.microsoftonline.com/{0}" />-->  
<add key="ida:PostLogoutRedirectUri" value="https://localhost:44320/" />

AD FS OpenID

Open the Startup.Auth.cs file and make the following changes:

Comment out the following:

//public static readonly string Authority = String.Format(CultureInfo.InvariantCulture, aadInstance, tenant);

Tweak the OpenId Connect middleware initialization logic with the following changes:

private static string clientId = ConfigurationManager.AppSettings["ida:ClientId"];  
//private static string aadInstance = ConfigurationManager.AppSettings["ida:AADInstance"];  
//private static string tenant = ConfigurationManager.AppSettings["ida:Tenant"];  
private static string metadataAddress = ConfigurationManager.AppSettings["ida:ADFSDiscoveryDoc"];  
private static string postLogoutRedirectUri = ConfigurationManager.AppSettings["ida:PostLogoutRedirectUri"];

AD FS OpenID

Farther down, modify the OpenId Connect middleware options as in the following:
```
app.UseOpenIdConnectAuthentication(  
    new OpenIdConnectAuthenticationOptions  
    {  
        ClientId = clientId,  
        //Authority = authority,  
        MetadataAddress = metadataAddress,  
        RedirectUri = postLogoutRedirectUri,  
        PostLogoutRedirectUri = postLogoutRedirectUri 
```
By changing the above we are doing the following:
- Instead of using the Authority for communicating data about the trusted issuer, we specify the discovery doc location directly via MetadataAddress
- Azure AD does not enforce the presence of a redirect_uri in the request, but ADFS does. So, we need to add it here