Over on the Geneva forums a question was asked:

Does anyone have an example of how to change the HomeRealmDiscovery Page in ADFSv2 to accept an e-mail address in a text field and based upon that (actually the domain suffix) select the correct Claims/Identity Provider?

It’s pretty easy to modify the HomeRealmDiscovery page, so I thought I’d give it a go.

Based on the question, two things need to be known: the email address and the home realm URI.  Then we need to translate the email address to a home realm URI and pass it on to ADFS.

This could be done a couple ways.  First it could be done by keeping a list of email addresses and their related home realms, or a list of email domains and their related home realms.  For the sake of this being an example, lets do both.

I’ve created a simple SQL database with three tables:

image

Each entry in the EmailAddress and Domain table have a pointer to the home realm URI (you can find the schema in the zip file below).

Then I created a new ADFS web project and added a new entity model to it:

image

From there I modified the HomeRealmDiscovery page to do the check:

//------------------------------------------------------------
// Copyright (c) Microsoft Corporation.  All rights reserved.
//------------------------------------------------------------

using System;

using Microsoft.IdentityServer.Web.Configuration;
using Microsoft.IdentityServer.Web.UI;
using AdfsHomeRealm.Data;
using System.Linq;

public partial class HomeRealmDiscovery : Microsoft.IdentityServer.Web.UI.HomeRealmDiscoveryPage
{
    protected void Page_Init(object sender, EventArgs e)
    {
    }

    protected void PassiveSignInButton_Click(object sender, EventArgs e)
    {
        string email = txtEmail.Text;

        if (string.IsNullOrWhiteSpace(email))
        {
            SetError("Please enter an email address");
            return;
        }

        try
        {
            SelectHomeRealm(FindHomeRealmByEmail(email));
        }
        catch (ApplicationException)
        {
            SetError("Cannot find home realm based on email address");
        }
    }

    private string FindHomeRealmByEmail(string email)
    {
        using (AdfsHomeRealmDiscoveryEntities en = new AdfsHomeRealmDiscoveryEntities())
        {
            var emailRealms = from e in en.EmailAddresses where e.EmailAddress1.Equals(email) select e;

            if (emailRealms.Any()) // email address exists
                return emailRealms.First().HomeRealm.HomeRealmUri;

            // email address does not exist
            string domain = ParseDomain(email);

            var domainRealms = from d in en.Domains where d.DomainAddress.Equals(domain) select d;

            if (domainRealms.Any()) // domain exists
                return domainRealms.First().HomeRealm.HomeRealmUri;

            // neither email nor domain exist
            throw new ApplicationException();
        }
    }

    private string ParseDomain(string email)
    {
        if (!email.Contains("@"))
            return email;

        return email.Substring(email.IndexOf("@") + 1);
    }

    private void SetError(string p)
    {
        lblError.Text = p;
    }
}

 

If you compare the original code, there was some changes.  I removed the code that loaded the original home realm drop down list, and removed the code to choose the home realm based on the drop down list’s selected value.

You can find my code here: http://www.syfuhs.net/AdfsHomeRealm.zip

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