OpenIDConnectAuthenticator.cs

using System.Linq;
using Agresso.Foundation;
using Agresso.Interface.Authentication;
using Agresso.Interface.Authentication.SingleStage;
using Agresso.Interface.CoreServices;
using System;
using System.Web;

namespace OpenIdConnectAuthenticator
{
    [Authenticator("U4A_OPENID", "OpenID Connect-based authentication", false, PlatformConstant.Web)]
    public class OpenIdConnectAuthenticator : Authenticator
    {
        private IUsers _users;

        private IUsers Users
        {
            get
            {
                if (_users == null)
                {
                    _users = ObjectFactory.CreateInstance<IUsers>();
                }

                return _users;
            }
        }

        public override Response Authenticate(Credentials credentials)
        {
            Response response = new Response();
            
            string code = Request.QueryString["code"];

            if (!string.IsNullOrEmpty(code))
            {
                object state = HttpContext.Current.Session["state"];
                HttpContext.Current.Session.Remove("state");

                if (state == null || Request.QueryString["state"] != state.ToString())
                {
                    response.DenyAccess("Request is not valid. Please try again.");
                    return response;
                }

                string verifiedEmail = OAuth2.GetVerifiedEmail(code);
                if (string.IsNullOrEmpty(verifiedEmail))
                {
                    response.DenyAccess("Could complete authentication.");
                    return response;
                }

                IUserInfo user = Users.GetByDomainUser(verifiedEmail);
                if (user != null && Users.AllowedAccessClient(user.UserId, user.DefaultClient))
                {
                    response.GrantAccess(user.UserId, user.DefaultClient);
                    return response;
                }

                response.DenyAccess("User is not mapped");
                return response;
            }

            string random = Random(32);

            string getCode = string.Format("{0}?response_type={1}&scope={2}&client_id={3}&redirect_uri={4}&state={5}", 
                Settings.AuthorizationEndpoint, 
                "code",
                "openid email", 
                Settings.ClientId, 
                Settings.RedirectUri, 
                random);

            HttpContext.Current.Session["state"] = random;
            HttpContext.Current.Response.Redirect(getCode);

            return response;
        }

        private string Random(int size)
        {
            const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
            var random = new Random();
            return new string(
                Enumerable.Repeat(chars, size)
                          .Select(s => s[random.Next(s.Length)])
                          .ToArray());
        }
    }

}