Getting the resolved Sitecore username corresponding to a facebook account on successful login

Question

I have social log in set up with federated authentication on a Sitecore 9 instance. I am able to login with facebook from my front end site:

Where can a capture this 'hVEQItzjCrLQI1Fuc0v3pQ' on login? I looked up this blog post: http://blog.nikkipunjabi.com/2018/03/sitecore-federated-authentication-part-2-google-and-facebook-app-and-the-custom-processor.html

And the ProcessCore method does provide me with OnAuthenticated handler, but I dont see this sitecore generated user id in any object. I only see the claims data returned from facebook - I also checked in the handler for OnReturnEndpoint - and dont see it there too.

I am pretty much using the same code as in the example. Just added some code to show the login buttons on the front end site.

public class FacebookAuthentication : IdentityProvidersProcessor
{
    public FacebookAuthentication(FederatedAuthenticationConfiguration federatedAuthenticationConfiguration) : base(federatedAuthenticationConfiguration)
    {
    }

    protected override string IdentityProviderName => "Facebook";

    protected override void ProcessCore(IdentityProvidersArgs args)
    {
        Assert.ArgumentNotNull(args, "args");
        IdentityProvider identityProvider = GetIdentityProvider();
        GetAuthenticationType();

        FacebookAuthenticationProvider facebookProvider = new FacebookAuthenticationProvider
        {
            OnAuthenticated = context =>
            {
                // transform all claims
                ClaimsIdentity identity = context.Identity;
                foreach (Transformation current in identityProvider.Transformations)
                {
                    current.Transform(identity, new TransformationContext(FederatedAuthenticationConfiguration, identityProvider));
                }
                return System.Threading.Tasks.Task.FromResult(0);
            },

            OnReturnEndpoint = (context) =>
            {
                if (context.Request.Query["state"] != null)
                {
                    var state = HttpUtility.ParseQueryString(context.Request.Query["state"]);
                    //Tring stuff here, trying to resolve the sitecore user name hash from facebook info??
                    IOwinContext context1 = HttpContext.Current.GetOwinContext();
                    UserManager<ApplicationUser> userManager = context1.GetUserManager();
                }

                return System.Threading.Tasks.Task.FromResult(0);
            }
        };

        IdentifyProviderCredentials credentials = IdentityProviderConfiguration.Current.GetCredentials(GetType().Name);

        FacebookAuthenticationOptions options = new FacebookAuthenticationOptions
        {
            AppId = credentials.AppId,
            AppSecret = credentials.AppSecret,
            Provider = facebookProvider
        };
        options.Fields.Add("name");
        options.Fields.Add("email");
        options.Scope.Add("email");
        args.App.UseFacebookAuthentication(options);
    }
}

Any ideas?

Answer 1

The username is generated by Sitecore via Sitecore.Owin.Authentication.Services.DefaultExternalUserBuilder.

User names must be unique across a Sitecore instance. You cannot use user names from different external providers as Sitecore user names because this does not guarantee that the user names are unique. The DefaultExternalUserBuilder class creates a sequence of user names for a given external user name. It then uses the first of these names that does not already exist in Sitecore. The values in the sequence depend only on the external username and the Sitecore domain configured for the given identity provider.

You can change this functionality by patching the config to use your own username builder like:

<identityProvidersPerSites hint="list:AddIdentityProvidersPerSites">
<mapEntry name="visitors" type="Sitecore.Owin.Authentication.Collections.IdentityProvidersPerSitesMapEntry, Sitecore.Owin.Authentication">
 <externalUserBuilder type="MyNamespace.ExternalUserBuilder, MyLibrary">
    <param desc="isPersistentUser">false</param>
  </externalUserBuilder>
</mapEntry>

And the implementation:

public class ExternalUserBuilder : Sitecore.Owin.Authentication.Services.DefaultExternalUserBuilder
{        
    protected override string CreateUniqueUserName(UserManager<ApplicationUser> userManager, ExternalLoginInfo externalLoginInfo)
    {        
        return externalLoginInfo.ExternalIdentity.FindFirstValue("FullName");
    }
}