vbookie

private Task SecurityTokenValidatedInternal(SecurityTokenValidatedNotification<OpenIdConnectMessage, OpenIdConnectAuthenticationOptions> notification)
{
    var identity = notification.AuthenticationTicket.Identity;

    // Instead of getting the email claim, get another claim to identify the user and generate a unique email
    var externalUserUniqueClaim = identity.FindFirst("someuniqueclaim");
    if (externalUserUniqueClaim != null)
    {
        var userEmail = externalUserUniqueClaim.Value + "@somedomain.test";

vbookie

using System;
using System.Collections.Generic;
using System.Security.Claims;
using System.Threading.Tasks;
using Microsoft.IdentityModel.Protocols;
using Microsoft.Owin;
using Microsoft.Owin.Security.Notifications;
using Microsoft.Owin.Security.OpenIdConnect;
using Owin;
using Telerik.Sitefinity.Authentication;

vbookie

public class CustomGoogleAuthenticationProvider : SitefinityGoogleAuthenticationProvider
{
    public override Task Authenticated(GoogleOAuth2AuthenticatedContext context)
    {
        var isIdentityValid = YourCustomCheck();
        if (!isIdentityValid)
        {
            context.Identity = null;
            return Task.FromResult(0);
        }