I need a good advise and wanted to know whether a solution is feasible or not. Right now one of my customer has a common login application which is based on Forms authentication(ASP.NET) using membership provider. All internal users use their AD credentials to logon and external users use custom username and password. Both are wrapped via Forms authentication. Now the new proposal is to replace this Forms authentication with ADFS. I have gone through various articles over internet and not able to come to a conclusion. Let me list my findings so far with ADFS extension points.
1) It is possible to add a custom attribute to ADFS claims by the approach mentioned inhttps://blogs.technet.microsoft.com/cloudpfe/2013/12/27/how-to-create-a-custom-attribute-store-for-active-directory-federation-services-3-0/.
2) It is possible to add a second level of authentication( or multifactor authentication) via the approachhttps://blogs.msdn.microsoft.com/jenfieldmsft/2014/03/24/build-your-own-external-authentication-provider-for-ad-fs-in-windows-server-2012-r2-walk-through-part-1/. Here I understand that after first level authentication done by AD and after that only our external provider will come into picture.
So I have a general question that is it really possible to achieve what I am looking for with ADFS(Replacing current Forms authentications with ADFS). Please let me know.