C# ASP.NET Single Sign-On Implementation

I am tasked with implementing single sign-on for our customers as part of our next release. The flow exists as follows:

1. User logs into their school's main portal system using a student id/password provided to him/her by the school.
2. User clicks the link to my company's product.
3. User is automatically taken to the dashboard page as if they had just logged in through the login form on our site.

Thus, there are two mechanisms by which a user can be authenticated into our site:

1. Coming to our product's home page, and logging in using the email/password that we store in our local system.
2. Using the single sign-on where the student has already logged into the school's main system with a student id and password.

If our product's implementation is in ASP.NET (as opposed to Java/Ruby), should we be using CAS, JOSSO, or some other third party single sign-on product? Or is there something available to a .NET environment which would be simpler for us as a .NET company?

There are multiple options to implement SSO for a .NET application.

Check out the following tutorials online:

Basics of Single Sign on, July 2012

http://www.codeproject.com/Articles/429166/Basics-of-Single-Sign-on-SSO

GaryMcAllisterOnline: ASP.NET MVC 4, ADFS 2.0 and 3rd party STS integration (IdentityServer2), Jan 2013

http://garymcallisteronline.blogspot.com/2013/01/aspnet-mvc-4-adfs-20-and-3rd-party-sts.html

The first one uses ASP.NET Web Forms, while the second one uses ASP.NET MVC4.

If your requirements allow you to use a third-party solution, also consider OpenID. There's an open source library called DotNetOpenAuth.

For further information, read MSDN blog post Integrate OpenAuth/OpenID with your existing ASP.NET application using Universal Providers.

Hope this helps!

I am late to the party, but for option #1, I would go with IdentityServer3(.NET 4.6 or below) or IdentityServer4 (compatible with Core) .

You can reuse your existing user store in your app and plug that to be IdentityServer's User Store. Then the clients must be pointed to your IdentityServer as the open id provider.

There are several Identity providers with SSO support out of the box, also some third-party** services.

** The only problem with third-party services is that they might charge per user/month, which can be pretty expensive.

Some of the tools available and with APIs for .NET are:

• Auth0
• IdentityExpress (with Admin UI) by IdentityServer
• Centrify Identity Service
• Okta Identity (SAML 2.0)
• OneLogin

If you decide to go with your implementation, you could use the frameworks below categorized by programming language.

C#:

• IdentityServer3 (OAuth/OpenID protocols, OWIN/Katana)
• IdentityServer4 (OAuth/OpenID protocols, ASP.NET Core)
• OAuth 2.0 by Okta

JavaScript:

• passport-openidconnect (node.js)
• oidc-provider (node.js)
• openid-client (node.js)

Python:

• pyoidc
• Django OIDC Provider

I would go with Auth0 as a service, as it's free for the first 7000 users, supports many languages, and not much needs to be done. However, if you need a more robust, manage yourself, and cheaper solution, I would configure IdentityServer4 and ASP.NET Core application and add authentication providers as necessary.

Both Auth0 and IdentityServer4 solutions use OAuth/OpenID protocols, supporting also WS-Federation and SAML 2.0 integration.

[disclaimer: I'm one of the contributors]

We built a very simple free/opensource component that adds SAML support for ASP.NET apps https://github.com/jitbit/AspNetSaml

Basically it's just one short C# file you can throw into your project (or install via Nuget) and use it with your app

UltimateSAML SSO is an OASIS SAML v1.x and v2.0 specifications compliant .NET toolkit. It offers an elegant and easy way to add support for Single Sign-On and Single-Logout SAML to your ASP.NET, ASP.NET MVC, ASP.NET Core, Desktop, and Service applications. The lightweight library helps you provide SSO access to cloud and intranet websites using a single credentials entry.

Detailed UltimateSAML SSO review can be found here