The HomeController

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Mvc.Ajax;
using System.Configuration;
using Microsoft.AspNet.Identity.EntityFramework;
using Microsoft.AspNet.Identity;
using Amazon;
using Amazon.Runtime;
using Amazon.CognitoIdentityProvider;
using Amazon.CognitoIdentityProvider.Model;
using Amazon.CognitoIdentity;
using Amazon.CognitoSync;
using System.Threading.Tasks;
using MasterBuilder.Helpers;
using MasterBuilder.Models;

namespace MasterBuilder.Controllers
{
    //
    //GET /HOME/Index.cshtml
        public class HomeController : Controller
    {
        // /Home/SignUp
        [HttpPost]
        public ActionResult SignUp(string name, string pass, string email)
        {

            CognitoUser user = new CognitoUser()
            {
                UserName = name,
                Password = pass,
                Email = email
            };

            //Create user
            new CognitoUserStore()
             .CreateAsync(user);
            return View("Success");
        }

        [HttpGet]
        public ActionResult SignUp()
        {

            return View();
        }
        //-----------------------------/Home/SignUp

        // /Home/Login
        [HttpGet]
        public ActionResult Index()
        {

            return View();
        }

        [HttpPost]
        public ActionResult Index(string name, string pass)
        {

            //var authReq = new AdminInitiateAuthRequest();


            var cognitoStore = new CognitoUserStore();

            var cognitoManager = new CognitoUserManager(new UserStore<CognitoUser>());

            CognitoUser user = new CognitoUser()
            {
                UserName = name
            };

            if (cognitoManager.CheckPasswordAsync(user, pass).Result)
                ViewBag.Message = "Usuário Valido";

            else
                ViewBag.Message = "Usuário Inválido";

            return View();

        }
        //-----------------------------/Home/Login


    }
}
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The Helpers

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using System;
using Microsoft.AspNet.Identity.EntityFramework;

namespace MasterBuilder.Helpers
{
    public class CognitoUser : IdentityUser
    {
        public string Password { get; set; }
        public Amazon.CognitoIdentityProvider.UserStatusType Status { get; set; }
    }
}
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using System;
using System.Configuration;
using System.Threading.Tasks;
using Microsoft.AspNet.Identity;
using Amazon.CognitoIdentityProvider;
using Amazon.CognitoIdentityProvider.Model;

namespace MasterBuilder.Helpers
{
    public class CognitoUserStore : IUserStore<CognitoUser>,
                                  IUserLockoutStore<CognitoUser, string>,
                                  IUserTwoFactorStore<CognitoUser, string>
    {
        private readonly AmazonCognitoIdentityProviderClient _client =
            new AmazonCognitoIdentityProviderClient();
        private readonly string _clientId = ConfigurationManager.AppSettings["CLIENT_ID"];
        private readonly string _poolId = ConfigurationManager.AppSettings["USERPOOL_ID"];

        public Task CreateAsync(CognitoUser user)
        {
            // Register the user using Cognito
            var signUpRequest = new SignUpRequest
            {
                ClientId = ConfigurationManager.AppSettings["CLIENT_ID"],
                Password = user.Password,
                Username = user.Email,

            };

            var emailAttribute = new AttributeType
            {
                Name = "email",
                Value = user.Email
            };
            signUpRequest.UserAttributes.Add(emailAttribute);

            return _client.SignUpAsync(signUpRequest);
        }

        public Task DeleteAsync(CognitoUser user)
        {
            throw new NotImplementedException();
        }

        public void Dispose()
        {
            throw new NotImplementedException();
        }

        public Task<CognitoUser> FindByIdAsync(string userId)
        {
            throw new NotImplementedException();
        }

        public Task<CognitoUser> FindByNameAsync(string userName)
        {
            throw new NotImplementedException();
        }

        public Task<int> GetAccessFailedCountAsync(CognitoUser user)
        {
            throw new NotImplementedException();
        }

        public Task<bool> GetLockoutEnabledAsync(CognitoUser user)
        {
            throw new NotImplementedException();
        }

        public Task<DateTimeOffset> GetLockoutEndDateAsync(CognitoUser user)
        {
            throw new NotImplementedException();
        }

        public Task<bool> GetTwoFactorEnabledAsync(CognitoUser user)
        {
            throw new NotImplementedException();
        }

        public Task<int> IncrementAccessFailedCountAsync(CognitoUser user)
        {
            throw new NotImplementedException();
        }

        public Task ResetAccessFailedCountAsync(CognitoUser user)
        {
            throw new NotImplementedException();
        }

        public Task SetLockoutEnabledAsync(CognitoUser user, bool enabled)
        {
            throw new NotImplementedException();
        }

        public Task SetLockoutEndDateAsync(CognitoUser user, DateTimeOffset lockoutEnd)
        {
            throw new NotImplementedException();
        }

        public Task SetTwoFactorEnabledAsync(CognitoUser user, bool enabled)
        {
            throw new NotImplementedException();
        }

        public Task UpdateAsync(CognitoUser user)
        {
            throw new NotImplementedException();
        }
    }
}
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using System.Configuration;
using Microsoft.AspNet.Identity;
using Amazon.CognitoIdentityProvider.Model;
using Amazon.CognitoIdentityProvider;
using System.Threading.Tasks;

namespace MasterBuilder.Helpers
{
    public class CognitoUserManager : UserManager<CognitoUser>
    {

        private readonly AmazonCognitoIdentityProviderClient _client =
            new AmazonCognitoIdentityProviderClient();
        private readonly string _clientId = ConfigurationManager.AppSettings["CLIENT_ID"];
        private readonly string _poolId = ConfigurationManager.AppSettings["USERPOOL_ID"];

        public CognitoUserManager(IUserStore<CognitoUser> store)
            : base(store)
        {
        }

        public override Task<bool> CheckPasswordAsync(CognitoUser user, string password)
        {
            return CheckPasswordAsync(user.UserName, password);
        }

        private async Task<bool> CheckPasswordAsync(string userName, string password)
        {
            try
            {
                var authReq = new AdminInitiateAuthRequest
                {
                    UserPoolId = ConfigurationManager.AppSettings["USERPOOL_ID"],
                    ClientId = ConfigurationManager.AppSettings["CLIENT_ID"],
                    AuthFlow = AuthFlowType.ADMIN_NO_SRP_AUTH
                };
                authReq.AuthParameters.Add("USERNAME", userName);
                authReq.AuthParameters.Add("PASSWORD", password);

                AdminInitiateAuthResponse authResp = await _client.AdminInitiateAuthAsync(authReq);

                return true;
            }
            catch
            {
                return false;
            }
        }
    }
}

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