How to design User authentication for 2 servers

Question

I need to authenticate a user from 2 servers. First, a user would be authenticated from Server A, on success, his AD (Active Directory) credentials would be authenticated to Server B (which is AD).

Should, server A, send an OKAY signal to Server B (Active Directory) that server A has done with authentication and its okay. I am confused about this part, since if I apply this security constraint then i have to do extra work on server side. I want to keep servers independent of this approach. The point is, Server A might be on Internet or some server which is not in the Network and Server B (the Active Directory) would be in the very network.

Need guidance

P.S:

A user credentials for Server A would be different from his Active Directory Credentials.

Answer 1

If you are doing this in C# code, why not just check each authorization in sequence? This is likely your best bet. For example maybe something similar to:

Private bool authenticateUser()
{
   if(authenticateWithServerA(username1, password1))
   {
     if(authenticateWithServerB(username2, password2))
       return true;
   }


   return false;
}