教學：建立 Windows Hello 登入服務

這是完整攻略的第二部分，說明如何在包裝的 Windows 應用程式中，使用 Windows Hello 作為傳統使用者名稱與密碼驗證系統的替代方案。本文接續第一部分 Windows Hello 登入應用程式的部分，並擴充功能，示範如何將Windows Hello整合進現有應用程式。

要建立這個 project，你需要一些 C# 和 XAML 的經驗。你還需要在 Windows 10 或 Windows 11 電腦上使用 Visual Studio 2022。如需設定開發環境的完整指示，請參閱開始開發 Windows 應用程式。

練習 1：伺服器端邏輯

在這個練習中，你將從第一個實驗室建置的 Windows Hello 應用程式開始，並建立本地的模擬伺服器和資料庫。這個實作實驗室旨在教導如何將 Windows Hello 整合進現有系統。藉由使用模擬伺服器和模擬資料庫，會消除許多不相關的設定。在您自己的應用程式中，您必須將模擬物件取代為實際的服務和資料庫。

首先，打開第一個 Windows Hello Hands On Lab 中的 WindowsHelloLogin 解決方案。
您一開始會實作模擬伺服器和模擬資料庫。建立名為「AuthService」的新資料夾。在Solution Explorer中，右鍵點擊 WindowsHelloLogin project，選擇 Add>New Folder。
建立 UserAccount 和 WindowsHelloDevices 類別，以作為要儲存在模擬資料庫中之數據的模型。 UserAccount 會類似於在傳統驗證伺服器上實作的使用者模型。以滑鼠右鍵按兩下 AuthService 資料夾，然後新增名為「UserAccount」的新類別。

建立 Windows Hello 授權資料夾的截圖
將類別範圍變更為 public，併為 UserAccount 類別新增下列公用屬性。您必須為 System.ComponentModel.DataAnnotations 命名空間新增using語句。
```
using System;
using System.ComponentModel.DataAnnotations;

namespace WindowsHelloLogin.AuthService
{
    public class UserAccount
    {
        [Key, Required]
        public Guid UserId { get; set; }
        [Required]
        public string Username { get; set; }
        public string Password { get; set; }
        // public List<WindowsHelloDevice> WindowsHelloDevices = new();
    }
}
```
您可能已經注意到已批注的 WindowsHelloDevices 清單。這是您必須在目前實作中對現有使用者模型所做的修改。 WindowsHelloDevices 清單會包含一個 deviceID、由 Windows Hello 製作的公鑰，以及一個 KeyCredentialAttestationResult。在這個練習中，你需要實作 keyAttestationResult，因為這功能只在搭載 TPM（可信平台模組）晶片的裝置上由 Windows Hello 提供。 KeyCredentialAttestationResult 結合了多個屬性，需要拆分，才能透過資料庫儲存和載入它們。

在名為「WindowsHelloDevice.cs」的 AuthService 資料夾中建立新的類別。這就是上述 Windows Hello 裝置的型號。將類別範圍變更為公用，並新增下列屬性。

using System;

namespace WindowsHelloLogin.AuthService
{
    public class WindowsHelloDevice
    {
        // These are the new variables that will need to be added to the existing UserAccount in the Database
        // The DeviceName is used to support multiple devices for the one user.
        // This way the correct public key is easier to find as a new public key is made for each device.
        // The KeyAttestationResult is only used if the User device has a TPM (Trusted Platform Module) chip, 
        // in most cases it will not. So will be left out for this hands on lab.
        public Guid DeviceId { get; set; }
        public byte[] PublicKey { get; set; }
        // public KeyCredentialAttestationResult KeyAttestationResult { get; set; }
    }
}

回到UserAccount.cs並取消Windows Hello裝置清單的評論。

using System.Collections.Generic;

namespace WindowsHelloLogin.AuthService
{
    public class UserAccount
    {
        [Key, Required]
        public Guid UserId { get; set; }
        [Required]
        public string Username { get; set; }
        public string Password { get; set; }
        public List<WindowsHelloDevice> WindowsHelloDevices = new();
    }
}

建立 UserAccount 和 WindowsHelloDevice 的模型後，您必須在 AuthService 資料夾中建立另一個新類別，以作為模擬資料庫，因為這是模擬資料庫，而您將從本機儲存和載入用戶帳戶清單。在真實世界中，這會是您的資料庫實作。在名為「MockStore.cs」的 AuthService 資料夾中建立新的類別。將類別範圍變更為 public。

當模擬存放區會在本機儲存及載入使用者帳戶清單時，您可以實作邏輯，以使用 XmlSerializer 儲存和載入該清單。您也必須記住檔名和儲存位置。在 MockStore.cs中實作下列專案：

using System.Collections.Generic;
using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Serialization;
using Windows.Storage;

namespace WindowsHelloLogin.AuthService
{
    public class MockStore
    {
        private const string USER_ACCOUNT_LIST_FILE_NAME = "userAccountsList.txt";
        // This cannot be a const because the LocalFolder is accessed at runtime
        private string _userAccountListPath = Path.Combine(
            ApplicationData.Current.LocalFolder.Path, USER_ACCOUNT_LIST_FILE_NAME);
        private List<UserAccount> _mockDatabaseUserAccountsList;

#region Save and Load Helpers
        /// <summary>
        /// Create and save a useraccount list file. (Replacing the old one)
        /// </summary>
        private async Task SaveAccountListAsync()
        {
            string accountsXml = SerializeAccountListToXml();

            if (File.Exists(_userAccountListPath))
            {
                StorageFile accountsFile = await StorageFile.GetFileFromPathAsync(_userAccountListPath);
                await FileIO.WriteTextAsync(accountsFile, accountsXml);
            }
            else
            {
                StorageFile accountsFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(USER_ACCOUNT_LIST_FILE_NAME);
                await FileIO.WriteTextAsync(accountsFile, accountsXml);
            }
        }

        /// <summary>
        /// Gets the useraccount list file and deserializes it from XML to a list of useraccount objects.
        /// </summary>
        /// <returns>List of useraccount objects</returns>
        private async Task LoadAccountListAsync()
        {
            if (File.Exists(_userAccountListPath))
            {
                StorageFile accountsFile = await StorageFile.GetFileFromPathAsync(_userAccountListPath);

                string accountsXml = await FileIO.ReadTextAsync(accountsFile);
                DeserializeXmlToAccountList(accountsXml);
            }

            // If the UserAccountList does not contain the sampleUser Initialize the sample users
            // This is only needed as it in a Hand on Lab to demonstrate a user being migrated.
            // In the real world, user accounts would just be in a database.
            if (!_mockDatabaseUserAccountsList.Any(f => f.Username.Equals("sampleUsername")))
            {
                //If the list is empty, call InitializeSampleAccounts and return the list
                //await InitializeSampleUserAccountsAsync();
            }
        }

        /// <summary>
        /// Uses the local list of accounts and returns an XML formatted string representing the list
        /// </summary>
        /// <returns>XML formatted list of accounts</returns>
        private string SerializeAccountListToXml()
        {
            var xmlizer = new XmlSerializer(typeof(List<UserAccount>));
            var writer = new StringWriter();
            xmlizer.Serialize(writer, _mockDatabaseUserAccountsList);
            return writer.ToString();
        }

        /// <summary>
        /// Takes an XML formatted string representing a list of accounts and returns a list object of accounts
        /// </summary>
        /// <param name="listAsXml">XML formatted list of accounts</param>
        /// <returns>List object of accounts</returns>
        private List<UserAccount> DeserializeXmlToAccountList(string listAsXml)
        {
            var xmlizer = new XmlSerializer(typeof(List<UserAccount>));
            TextReader textreader = new StreamReader(new MemoryStream(Encoding.UTF8.GetBytes(listAsXml)));
            return _mockDatabaseUserAccountsList = (xmlizer.Deserialize(textreader)) as List<UserAccount>;
        }
#endregion
    }
}

在 LoadAccountListAsync 方法中，您可能已經注意到 InitializeSampleUserAccountsAsync 方法被註解掉了。您必須在 MockStore.cs 中建立這個方法。這個方法會填入使用者帳戶清單，以便進行登入。在真實世界中，用戶資料庫已經填滿。在此步驟中，您也將建立建構函式，以初始化使用者清單並呼叫 LoadAccountListAsync。

namespace WindowsHelloLogin.AuthService
{
    public class MockStore
    {
        private const string USER_ACCOUNT_LIST_FILE_NAME = "userAccountsList.txt";
        // This cannot be a const because the LocalFolder is accessed at runtime
        private string _userAccountListPath = Path.Combine(
            ApplicationData.Current.LocalFolder.Path, USER_ACCOUNT_LIST_FILE_NAME);
        private List<UserAccount> _mockDatabaseUserAccountsList;

        public MockStore()
        {
            _mockDatabaseUserAccountsList = new List<UserAccount>();
            _ = LoadAccountListAsync();
        }

        private async Task InitializeSampleUserAccountsAsync()
        {
            // Create a sample Traditional User Account that only has a Username and Password
            // This will be used initially to demonstrate how to migrate to use Windows Hello

            var sampleUserAccount = new UserAccount()
            {
                UserId = Guid.NewGuid(),
                Username = "sampleUsername",
                Password = "samplePassword",
            };

            // Add the sampleUserAccount to the _mockDatabase
            _mockDatabaseUserAccountsList.Add(sampleUserAccount);
            await SaveAccountListAsync();
        }
    }
}

現在 InitializeSampleUserAccountsAsync 方法已存在，取消 LoadAccountListAsync 方法中的方法呼叫的批注。

private async Task LoadAccountListAsync()
{
    if (File.Exists(_userAccountListPath))
    {
        StorageFile accountsFile = await StorageFile.GetFileFromPathAsync(_userAccountListPath);

        string accountsXml = await FileIO.ReadTextAsync(accountsFile);
        DeserializeXmlToAccountList(accountsXml);
    }

    // If the UserAccountList does not contain the sampleUser Initialize the sample users
    // This is only needed as it in a Hand on Lab to demonstrate a user migrating
    // In the real world user accounts would just be in a database
    if (!_mockDatabaseUserAccountsList.Any(f = > f.Username.Equals("sampleUsername")))
            {
        //If the list is empty InitializeSampleUserAccountsAsync and return the list
        await InitializeSampleUserAccountsAsync();
    }
}

模擬存放區中的用戶帳戶清單現在可以儲存和載入。應用程式的其他部分需要access這個清單，因此需要一些方法來取得這些資料。在 InitializeSampleUserAccountsAsync 方法底下，新增下列方法來取得數據。它們會讓你取得使用者ID、單一使用者、特定Windows Hello裝置的使用者清單，並且取得該裝置使用者的公開金鑰。

public Guid GetUserId(string username)
{
    if (_mockDatabaseUserAccountsList.Any())
    {
        UserAccount account = _mockDatabaseUserAccountsList.FirstOrDefault(f => f.Username.Equals(username));
        if (account != null)
        {
            return account.UserId;
        }
    }
    return Guid.Empty;
}

public UserAccount GetUserAccount(Guid userId)
{
    return _mockDatabaseUserAccountsList.FirstOrDefault(f => f.UserId.Equals(userId));
}

public List<UserAccount> GetUserAccountsForDevice(Guid deviceId)
{
    var usersForDevice = new List<UserAccount>();

    foreach (UserAccount account in _mockDatabaseUserAccountsList)
    {
        if (account.WindowsHelloDevices.Any(f => f.DeviceId.Equals(deviceId)))
        {
            usersForDevice.Add(account);
        }
    }

    return usersForDevice;
}

public byte[] GetPublicKey(Guid userId, Guid deviceId)
{
    UserAccount account = _mockDatabaseUserAccountsList.FirstOrDefault(f => f.UserId.Equals(userId));
    if (account != null)
    {
        if (account.WindowsHelloDevices.Any())
        {
            return account.WindowsHelloDevices.FirstOrDefault(p => p.DeviceId.Equals(deviceId)).PublicKey;
        }
    }
    return null;
}

要實作的下一個方法會處理簡單的作業，以新增帳戶、移除帳戶，以及移除裝置。移除裝置是必要的，因為 Windows Hello 是針對特定裝置設計的。每台你登入的裝置，Windows Hello 都會建立一組新的公鑰與私鑰對。就像針對您登入的每個裝置使用不同的密碼，唯一的一件事就是您不需要記住所有這些密碼;伺服器會執行此工作。將下列方法新增至MockStore.cs。

public async Task<UserAccount> AddAccountAsync(string username)
{
    UserAccount newAccount = null;
    try
    {
        newAccount = new UserAccount()
        {
            UserId = Guid.NewGuid(),
            Username = username,
        };

        _mockDatabaseUserAccountsList.Add(newAccount);
        await SaveAccountListAsync();
    }
    catch (Exception)
    {
        throw;
    }
    return newAccount;
}

public async Task<bool> RemoveAccountAsync(Guid userId)
{
    UserAccount userAccount = GetUserAccount(userId);
    if (userAccount != null)
    {
        _mockDatabaseUserAccountsList.Remove(userAccount);
        await SaveAccountListAsync();
        return true;
    }
    return false;
}

public async Task<bool> RemoveDeviceAsync(Guid userId, Guid deviceId)
{
    UserAccount userAccount = GetUserAccount(userId);
    WindowsHelloDevice deviceToRemove = null;
    if (userAccount != null)
    {
        foreach (WindowsHelloDevice device in userAccount.WindowsHelloDevices)
        {
            if (device.DeviceId.Equals(deviceId))
            {
                deviceToRemove = device;
                break;
            }
        }
    }

    if (deviceToRemove != null)
    {
        //Remove the WindowsHelloDevice
        userAccount.WindowsHelloDevices.Remove(deviceToRemove);
        await SaveAccountListAsync();
    }

    return true;
}

在 MockStore 類別中，新增一個方法，將Windows Hello相關資訊加入現有的 UserAccount。此方法稱為「WindowsHelloUpdateDetailsAsync」，會取得參數來識別使用者及 Windows Hello 的詳細資訊。在真實世界的應用程式中建立 WindowsHelloDevice 時，KeyAttestationResult 已被註解掉，但在實際應用中是需要的。

using System.Threading.Tasks;
using Windows.Security.Credentials;

public async Task WindowsHelloUpdateDetailsAsync(Guid userId, Guid deviceId, byte[] publicKey, 
    KeyCredentialAttestationResult keyAttestationResult)
{
    UserAccount existingUserAccount = GetUserAccount(userId);
    if (existingUserAccount != null)
    {
        if (!existingUserAccount.WindowsHelloDevices.Any(f => f.DeviceId.Equals(deviceId)))
        {
            existingUserAccount.WindowsHelloDevices.Add(new WindowsHelloDevice()
            {
                DeviceId = deviceId,
                PublicKey = publicKey,
                // KeyAttestationResult = keyAttestationResult
            });
        }
    }
    await SaveAccountListAsync();
}

MockStore 類別現在已完成，因為這代表資料庫應該視為私用。為了access MockStore，需要一個 AuthService類別來操作資料庫資料。在 AuthService 資料夾中，建立名為「AuthService.cs」的新類別。將類別範圍變更為公用，並新增單一實例模式，以確保只會建立一個實例。

namespace WindowsHelloLogin.AuthService
{
    public class AuthService
    {
        // Singleton instance of the AuthService
        // The AuthService is a mock of what a real world server and service implementation would be
        private static AuthService _instance;
        public static AuthService Instance
        {
            get
            {
                if (null == _instance)
                {
                    _instance = new AuthService();
                }
                return _instance;
            }
        }

        private AuthService()
        { }
    }
}

AuthService 類別需要建立 MockStore 類別的一個實例，並提供對 MockStore 物件屬性的存取。

namespace WindowsHelloLogin.AuthService
{
    public class AuthService
    {
        //Singleton instance of the AuthService
        //The AuthService is a mock of what a real world server and database implementation would be
        private static AuthService _instance;
        public static AuthService Instance
        {
            get
            {
                if (null == _instance)
                {
                    _instance = new AuthService();
                }
                return _instance;
            }
        }

        private AuthService()
        { }

        private MockStore _mockStore = new();

        public Guid GetUserId(string username)
        {
            return _mockStore.GetUserId(username);
        }

        public UserAccount GetUserAccount(Guid userId)
        {
            return _mockStore.GetUserAccount(userId);
        }

        public List<UserAccount> GetUserAccountsForDevice(Guid deviceId)
        {
            return _mockStore.GetUserAccountsForDevice(deviceId);
        }
    }
}

你需要在 AuthService 類別中設置方法，以便訪問 MockStore 物件中用於新增、移除和更新 Windows Hello 詳細資料的方法。在 AuthService 類別定義的結尾，新增下列方法。

using System.Threading.Tasks;
using Windows.Security.Credentials;

public async Task RegisterAsync(string username)
{
    await _mockStore.AddAccountAsync(username);
}

public async Task<bool> WindowsHelloRemoveUserAsync(Guid userId)
{
    return await _mockStore.RemoveAccountAsync(userId);
}

public async Task<bool> WindowsHelloRemoveDeviceAsync(Guid userId, Guid deviceId)
{
    return await _mockStore.RemoveDeviceAsync(userId, deviceId);
}

public async Task WindowsHelloUpdateDetailsAsync(Guid userId, Guid deviceId, byte[] publicKey, 
    KeyCredentialAttestationResult keyAttestationResult)
{
    await _mockStore.WindowsHelloUpdateDetailsAsync(userId, deviceId, publicKey, keyAttestationResult);
}

AuthService 類別必須提供方法來驗證認證。此方法會採用使用者名稱和密碼，並確定帳戶存在且密碼有效。現有的系統會有與這個相等的方法，可檢查使用者是否已獲得授權。將下列 ValidateCredentials 方法新增至AuthService.cs檔案。

public bool ValidateCredentials(string username, string password)
{
    if (!string.IsNullOrEmpty(username) && !string.IsNullOrEmpty(password))
    {
        // This would be used for existing accounts migrating to use Windows Hello
        Guid userId = GetUserId(username);
        if (userId != Guid.Empty)
        {
            UserAccount account = GetUserAccount(userId);
            if (account != null)
            {
                if (string.Equals(password, account.Password))
                {
                    return true;
                }
            }
        }
    }
    return false;
}

AuthService 類別需要要求挑戰方法，以將挑戰傳回給用戶端，以驗證使用者是否為他們聲稱的身分。然後需要在 AuthService 類別中加入另一種方法，以接收來自用戶端的簽署過的挑戰。針對這個實作課程，用來判斷已簽署的挑戰是否完成的方法尚未提供。每次將 Windows Hello 實作到現有的認證系統中都會略有不同。儲存在伺服器上的公鑰必須與用戶端傳回伺服器的結果相符。將這兩種方法新增至 AuthService.cs。

using Windows.Security.Cryptography;
using Windows.Storage.Streams;

public IBuffer WindowsHelloRequestChallenge()
{
    return CryptographicBuffer.ConvertStringToBinary("ServerChallenge", BinaryStringEncoding.Utf8);
}

public bool SendServerSignedChallenge(Guid userId, Guid deviceId, byte[] signedChallenge)
{
    // Depending on your company polices and procedures this step will be different
    // It is at this point you will need to validate the signedChallenge that is sent back from the client.
    // Validation is used to ensure the correct user is trying to access this account. 
    // The validation process will use the signedChallenge and the stored PublicKey 
    // for the username and the specific device signin is called from.
    // Based on the validation result you will return a bool value to allow access to continue or to block the account.

    // For this sample validation will not happen as a best practice solution does not apply and will need to 
       // be configured for each company.
    // Simply just return true.

    // You could get the User's Public Key with something similar to the following:
    byte[] userPublicKey = _mockStore.GetPublicKey(userId, deviceId);
    return true;
}

練習 2：客戶端邏輯

在此練習中，您將把第一個實驗室的客戶端視圖和輔助類別變更為使用 AuthService 類別。在真實世界中， AuthService 會是驗證伺服器，而您必須使用 Web API 從伺服器傳送和接收數據。在這個實際操作實驗中，為了簡化操作，用戶端和伺服器都是設置為本地。目標是學會如何使用 Windows Hello API。

在MainPage.xaml.cs中，您可以在載入的方法中移除 AccountHelper.LoadAccountListAsync 方法呼叫，因為 AuthService 類別會建立 MockStore 的實例以載入帳戶清單。方法 Loaded 現在看起來應該像下面的代碼段。請注意，因為沒有等待任何操作，異步方法的定義已被移除。
```
private void MainPage_Loaded(object sender, RoutedEventArgs e)
{
    Frame.Navigate(typeof(UserSelection));
}
```

更新 [登入 ] 頁面介面，以要求輸入密碼。這個實作實驗室示範如何將現有系統遷移至使用 Windows Hello，現有帳號將擁有使用者名稱和密碼。同時更新 XAML 底部的說明，以包含預設密碼。在 Login.xaml 中更新下列 XAML。

<Grid>
  <StackPanel>
    <TextBlock Text="Login" FontSize="36" Margin="4" TextAlignment="Center"/>

    <TextBlock x:Name="ErrorMessage" Text="" FontSize="20" Margin="4" Foreground="Red" TextAlignment="Center"/>

    <TextBlock Text="Enter your credentials below" Margin="0,0,0,20"
               TextWrapping="Wrap" Width="300"
               TextAlignment="Center" VerticalAlignment="Center" FontSize="16"/>

    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
      <!-- Username Input -->
      <TextBlock x:Name="UserNameTextBlock" Text="Username: "
                 FontSize="20" Margin="4" Width="100"/>
      <TextBox x:Name="UsernameTextBox" PlaceholderText="sampleUsername" Width="200" Margin="4"/>
    </StackPanel>

    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
      <!-- Password Input -->
      <TextBlock x:Name="PasswordTextBlock" Text="Password: "
                 FontSize="20" Margin="4" Width="100"/>
      <PasswordBox x:Name="PasswordBox" PlaceholderText="samplePassword" Width="200" Margin="4"/>
    </StackPanel>

    <Button x:Name="LoginButton" Content="Login" Background="DodgerBlue" Foreground="White"
            Click="LoginButton_Click" Width="80" HorizontalAlignment="Center" Margin="0,20"/>

    <TextBlock Text="Don't have an account?"
               TextAlignment="Center" VerticalAlignment="Center" FontSize="16"/>
    <TextBlock x:Name="RegisterButtonTextBlock" Text="Register now"
               PointerPressed="RegisterButtonTextBlock_OnPointerPressed"
               Foreground="DodgerBlue"
               TextAlignment="Center" VerticalAlignment="Center" FontSize="16"/>

    <Border x:Name="WindowsHelloStatus" Background="#22B14C"
            Margin="0,20" Height="100">
      <TextBlock x:Name="WindowsHelloStatusText" Text="Windows Hello is ready to use!"
                 Margin="4" TextAlignment="Center" VerticalAlignment="Center" FontSize="20"/>
    </Border>

    <TextBlock x:Name="LoginExplanation" FontSize="24" TextAlignment="Center" TextWrapping="Wrap" 
               Text="Please Note: To demonstrate a login, validation will only occur using the default username 'sampleUsername' and default password 'samplePassword'"/>
  </StackPanel>
</Grid>

在 Login 類別的程式代碼後置檔案中，您必須將類別頂端的私用變數變更 Account 為 UserAccount。將OnNavigateTo事件變更為將型別轉換成UserAccount的形式。您還需要以下的 using 語句。

using WindowsHelloLogin.AuthService;

namespace WindowsHelloLogin.Views
{
    public sealed partial class Login : Page
    {
        private UserAccount _account;
        private bool _isExistingAccount;

        public Login()
        {
            this.InitializeComponent();
        }

        protected override async void OnNavigatedTo(NavigationEventArgs e)
        {
            //Check Windows Hello is setup and available on this machine
            if (await WindowsHelloHelper.WindowsHelloAvailableCheckAsync())
            {
                if (e.Parameter != null)
                {
                    _isExistingAccount = true;
                    //Set the account to the existing account being passed in
                    _account = (UserAccount)e.Parameter;
                    UsernameTextBox.Text = _account.Username;
                    await SignInWindowsHelloAsync();
                }
            }
        }

        private async void LoginButton_Click(object sender, RoutedEventArgs e)
        {
            ErrorMessage.Text = "";
            await SignInWindowsHelloAsync();
        }
    }
}

由於登入頁面使用UserAccount物件而非Account物件，因此WindowsHelloHelper.cs需要更新為某些方法的參數類型使用UserAccount。您必須變更 CreateWindowsHelloKeyAsync、RemoveWindowsHelloAccountAsync 和 GetWindowsHelloAuthenticationMessageAsync 方法的下列參數。由於 UserAccount 類別包含 Guid 的 UserId，因此您將在更多地方開始使用該識別碼，以提高準確性。

public static async Task<bool> CreateWindowsHelloKeyAsync(Guid userId, string username)
{
    KeyCredentialRetrievalResult keyCreationResult = await KeyCredentialManager.RequestCreateAsync(username, KeyCredentialCreationOption.ReplaceExisting);

    return true;
}

public static async Task RemoveWindowsHelloAccountAsync(UserAccount account)
{

}
public static async Task<bool> GetWindowsHelloAuthenticationMessageAsync(UserAccount account)
{
    KeyCredentialRetrievalResult openKeyResult = await KeyCredentialManager.OpenAsync(account.Username);
    //Calling OpenAsync will allow the user access to what is available in the app and will not require user credentials again.
    //If you wanted to force the user to sign in again you can use the following:
    //var consentResult = await Windows.Security.Credentials.UI.UserConsentVerifier.RequestVerificationAsync(account.Username);
    //This will ask for the either the password of the currently signed in Microsoft Account or the PIN used for Windows Hello.

    if (openKeyResult.Status == KeyCredentialStatus.Success)
    {
        //If OpenAsync has succeeded, the next thing to think about is whether the client application requires access to backend services.
        //If it does here you would Request a challenge from the Server. The client would sign this challenge and the server
        //would check the signed challenge. If it is correct it would allow the user access to the backend.
        //You would likely make a new method called RequestSignAsync to handle all this
        //for example, RequestSignAsync(openKeyResult);
        //Refer to the second Windows Hello sample for information on how to do this.

        //For this sample there is not concept of a server implemented so just return true.
        return true;
    }
    else if (openKeyResult.Status == KeyCredentialStatus.NotFound)
    {
        //If the _account is not found at this stage. It could be one of two errors. 
        //1. Windows Hello has been disabled
        //2. Windows Hello has been disabled and re-enabled cause the Windows Hello Key to change.
        //Calling CreateWindowsHelloKeyAsync and passing through the account will attempt to replace the existing Windows Hello Key for that account.
        //If the error really is that Windows Hello is disabled then the CreateWindowsHelloKeyAsync method will output that error.
        if (await CreateWindowsHelloKeyAsync(account.UserId, account.Username))
        {
            //If the Windows Hello Key was again successfully created, Windows Hello has just been reset.
            //Now that the Windows Hello Key has been reset for the account retry sign in.
            return await GetWindowsHelloAuthenticationMessageAsync(account);
        }
    }

    // Can't use Windows Hello right now, try again later
    return false;
}

Login.xaml.cs 檔案中的 SignInWindowsHelloAsync 方法必須更新，才能使用 AuthService ，而不是 AccountHelper。驗證認證將會透過 AuthService 進行。對於這個實際作實驗室，唯一設定的帳戶是 “sampleUsername”。此帳戶是在 MockStore.cs 的 InitializeSampleUserAccountsAsync 方法中建立。更新 Login.xaml.cs 中的 SignInWindowsHelloAsync 方法，以反映下列代碼段。

private async Task SignInWindowsHelloAsync()
{
    if (_isExistingAccount)
    {
        if (await WindowsHelloHelper.GetWindowsHelloAuthenticationMessageAsync(_account))
        {
            Frame.Navigate(typeof(Welcome), _account);
        }
    }
    else if (AuthService.AuthService.Instance.ValidateCredentials(UsernameTextBox.Text, PasswordBox.Password))
    {
        Guid userId = AuthService.AuthService.Instance.GetUserId(UsernameTextBox.Text);

        if (userId != Guid.Empty)
        {
            //Now that the account exists on server try and create the necessary details and add them to the account
            if (await WindowsHelloHelper.CreateWindowsHelloKeyAsync(userId, UsernameTextBox.Text))
            {
                Debug.WriteLine("Successfully signed in with Windows Hello!");
                //Navigate to the Welcome Screen. 
                _account = AuthService.AuthService.Instance.GetUserAccount(userId);
                Frame.Navigate(typeof(Welcome), _account);
            }
            else
            {
                //The Windows Hello account creation failed.
                //Remove the account from the server as the details were not configured
                await AuthService.AuthService.Instance.WindowsHelloRemoveUserAsync(userId);

                ErrorMessage.Text = "Account Creation Failed";
            }
        }
    }
    else
    {
        ErrorMessage.Text = "Invalid Credentials";
    }
}

由於Windows Hello會在每個裝置上為每個帳號建立不同的公鑰與私鑰配對，Welcome頁面需要顯示已登入帳號的註冊裝置清單，並允許每一個裝置被遺忘。請在 Welcome.xaml 中的 ForgetButton 下方添加以下 XAML。這會實作忘記裝置按鈕、錯誤文字區域和清單以顯示所有裝置。

<Grid>
  <StackPanel>
    <TextBlock x:Name="Title" Text="Welcome" FontSize="40" TextAlignment="Center"/>
    <TextBlock x:Name="UserNameText" FontSize="28" TextAlignment="Center"/>

    <Button x:Name="BackToUserListButton" Content="Back to User List" Click="Button_Restart_Click"
            HorizontalAlignment="Center" Margin="0,20" Foreground="White" Background="DodgerBlue"/>

    <Button x:Name="ForgetButton" Content="Forget Me" Click="Button_Forget_User_Click"
            Foreground="White"
            Background="Gray"
            HorizontalAlignment="Center"/>

    <Button x:Name="ForgetDeviceButton" Content="Forget Device" Click="Button_Forget_Device_Click"
            Foreground="White"
            Background="Gray"
            Margin="0,40,0,20"
            HorizontalAlignment="Center"/>

    <TextBlock x:Name="ForgetDeviceErrorTextBlock" Text="Select a device first"
               TextWrapping="Wrap" Width="300" Foreground="Red"
               TextAlignment="Center" VerticalAlignment="Center" FontSize="16" Visibility="Collapsed"/>

    <ListView x:Name="UserListView" MaxHeight="500" MinWidth="350" Width="350" HorizontalAlignment="Center">
      <ListView.ItemTemplate>
        <DataTemplate>
          <Grid Background="Gray" Height="50" Width="350" HorizontalAlignment="Center" VerticalAlignment="Stretch" >
            <TextBlock Text="{Binding DeviceId}" HorizontalAlignment="Center" TextAlignment="Center" VerticalAlignment="Center"
                       Foreground="White"/>
          </Grid>
        </DataTemplate>
      </ListView.ItemTemplate>
    </ListView>
  </StackPanel>
</Grid>

在Welcome.xaml.cs檔案中，您必須將類別頂端的私 Account 用變數變更為私用 UserAccount 變數。然後更新 OnNavigatedTo 方法以使用 AuthService 並擷取目前帳戶的資訊。當您有帳戶資訊時，您可以設定ItemsSource清單以顯示裝置。您必須新增 AuthService 命名空間的參考。

using WindowsHelloLogin.AuthService;

namespace WindowsHelloLogin.Views
{
    public sealed partial class Welcome : Page
    {
        private UserAccount _activeAccount;

        public Welcome()
        {
            InitializeComponent();
        }

        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            _activeAccount = (UserAccount)e.Parameter;
            if (_activeAccount != null)
            {
                UserAccount account = AuthService.AuthService.Instance.GetUserAccount(_activeAccount.UserId);
                if (account != null)
                {
                    UserListView.ItemsSource = account.WindowsHelloDevices;
                    UserNameText.Text = account.Username;
                }
            }
        }
    }
}

當您移除帳戶時將使用 AuthService，因此可以在方法中移除對 Button_Forget_User_Click 的參考。方法現在應該如下所示。

private async void Button_Forget_User_Click(object sender, RoutedEventArgs e)
{
    //Remove it from Windows Hello
    await WindowsHelloHelper.RemoveWindowsHelloAccountAsync(_activeAccount);

    Debug.WriteLine($"User {_activeAccount.Username} deleted.");

    //Navigate back to UserSelection page.
    Frame.Navigate(typeof(UserSelection));
}

WindowsHelloHelper 方法未使用 AuthService 來移除帳戶。您必須呼叫 AuthService 並傳遞 userId。

public static async Task RemoveWindowsHelloAccountAsync(UserAccount account)
{
    //Open the account with Windows Hello
    KeyCredentialRetrievalResult keyOpenResult = await KeyCredentialManager.OpenAsync(account.Username);

    if (keyOpenResult.Status == KeyCredentialStatus.Success)
    {
        // In the real world you would send key information to server to unregister
        await AuthService.AuthService.Instance.WindowsHelloRemoveUserAsync(account.UserId);
    }

    //Then delete the account from the machines list of Windows Hello Accounts
    await KeyCredentialManager.DeleteAsync(account.Username);
}

在完成實作歡迎頁面之前，您必須在 WindowsHelloHelper.cs 中建立方法，以允許移除裝置。建立新的方法，以在 AuthService 中呼叫 WindowsHelloRemoveDeviceAsync。

public static async Task RemoveWindowsHelloDeviceAsync(UserAccount account, Guid deviceId)
{
    await AuthService.AuthService.Instance.WindowsHelloRemoveDeviceAsync(account.UserId, deviceId);
}

在 Welcome.xaml.cs 中，實作 Button_Forget_Device_Click 事件處理程式。這會使用從裝置清單中選定的裝置，並使用 Windows Hello 助手來呼叫移除裝置。請記得將事件處理程式設為異步。

private async void Button_Forget_Device_Click(object sender, RoutedEventArgs e)
{
    WindowsHelloDevice selectedDevice = UserListView.SelectedItem as WindowsHelloDevice;
    if (selectedDevice != null)
    {
        //Remove it from Windows Hello
        await WindowsHelloHelper.RemoveWindowsHelloDeviceAsync(_activeAccount, selectedDevice.DeviceId);

        Debug.WriteLine($"User {_activeAccount.Username} deleted.");

        if (!UserListView.Items.Any())
        {
            //Navigate back to UserSelection page.
            Frame.Navigate(typeof(UserSelection));
        }
    }
    else
    {
        ForgetDeviceErrorTextBlock.Visibility = Visibility.Visible;
    }
}

您要更新的下一個頁面是 UserSelection 頁面。 UserSelection 頁面必須使用 AuthService 來擷取目前裝置的所有用戶帳戶。目前，您無法取得裝置標識碼來傳遞至 AuthService ，以便傳回該裝置的用戶帳戶。在 Utils 資料夾中，建立名為「Helpers.cs」的新類別。將類別範圍變更為公用靜態，然後新增下列方法，讓您擷取目前的裝置標識碼。
```
using System;
using Windows.Security.ExchangeActiveSyncProvisioning;

namespace WindowsHelloLogin.Utils
{
    public static class Helpers
    {
        public static Guid GetDeviceId()
        {
            //Get the Device ID to pass to the server
            var deviceInformation = new EasClientDeviceInformation();
            return deviceInformation.Id;
        }
    }
}
```

在 UserSelection 頁面類別中，只有程式代碼後置需要變更，而不是使用者介面。在 UserSelection.xaml.cs中，更新 UserSelection_Loaded 方法和 UserSelectionChanged 方法，以使用 UserAccount 類別，而不是 Account 類別。您還需要透過 AuthService 取得此裝置的所有使用者。

using System.Linq;
using WindowsHelloLogin.AuthService;

namespace WindowsHelloLogin.Views
{
    public sealed partial class UserSelection : Page
    {
        public UserSelection()
        {
            InitializeComponent();
            Loaded += UserSelection_Loaded;
        }

        private void UserSelection_Loaded(object sender, RoutedEventArgs e)
        {
            List<UserAccount> accounts = AuthService.AuthService.Instance.GetUserAccountsForDevice(Helpers.GetDeviceId());

            if (accounts.Any())
            {
                UserListView.ItemsSource = accounts;
                UserListView.SelectionChanged += UserSelectionChanged;
            }
            else
            {
                //If there are no accounts navigate to the Login page
                Frame.Navigate(typeof(Login));
            }
        }

        /// <summary>
        /// Function called when an account is selected in the list of accounts
        /// Navigates to the Login page and passes the chosen account
        /// </summary>
        private void UserSelectionChanged(object sender, RoutedEventArgs e)
        {
            if (((ListView)sender).SelectedValue != null)
            {
                UserAccount account = (UserAccount)((ListView)sender).SelectedValue;
                if (account != null)
                {
                    Debug.WriteLine($"Account {account.Username} selected!");
                }
                Frame.Navigate(typeof(Login), account);
            }
        }
    }
}

WindowsHelloRegister 頁面必須更新程序代碼後置檔案。使用者介面不需要任何變更。在 WindowsHelloRegister.xaml.cs中，移除類別頂端的私 Account 用變數，因為不再需要它。更新 RegisterButton_Click_Async 事件處理程式以使用 AuthService。此方法會建立新的 UserAccount ，然後嘗試更新其帳戶詳細數據。如果 Windows Hello 未能建立金鑰，該帳號會因註冊失敗而被移除。

private async void RegisterButton_Click_Async(object sender, RoutedEventArgs e)
{
    ErrorMessage.Text = "";

    //Validate entered credentials are acceptable
    if (!string.IsNullOrEmpty(UsernameTextBox.Text))
    {
        //Register an Account on the AuthService so that we can get back a userId
        await AuthService.AuthService.Instance.RegisterAsync(UsernameTextBox.Text);
        Guid userId = AuthService.AuthService.Instance.GetUserId(UsernameTextBox.Text);

        if (userId != Guid.Empty)
        {
            //Now that the account exists on server try and create the necessary details and add them to the account
            if (await WindowsHelloHelper.CreateWindowsHelloKeyAsync(userId, UsernameTextBox.Text))
            {
                //Navigate to the Welcome Screen. 
                Frame.Navigate(typeof(Welcome), AuthService.AuthService.Instance.GetUserAccount(userId));
            }
            else
            {
                //The Windows Hello account creation failed.
                //Remove the account from the server as the details were not configured
                await AuthService.AuthService.Instance.WindowsHelloRemoveUserAsync(userId);

                ErrorMessage.Text = "Account Creation Failed";
            }
        }
    }
    else
    {
        ErrorMessage.Text = "Please enter a username";
    }
}

建置並執行應用程式。使用認證「sampleUsername」和「samplePassword」登入範例用戶帳戶。在歡迎畫面上，您可能會注意到雖然顯示了 [忘記裝置] 按鈕，但沒有任何裝置。當你建立或遷移使用者到Windows Hello時，帳號資訊不會被推送到AuthService。

Windows Hello登入畫面截圖

要將Windows Hello帳號資訊傳送到 AuthService，WindowsHelloHelper.cs 需要更新。在CreateWindowsHelloKeyAsync方法中，您不僅要在成功的情況下傳回true，而是需要呼叫一個新的方法，該方法將嘗試獲取KeyAttestation。即使這個實作實驗課程沒有在 AuthService 中記錄相關資訊，您將會了解到如何在用戶端取得這些資訊。更新 CreateWindowsHelloKeyAsync 方法，如下所示：

public static async Task<bool> CreateWindowsHelloKeyAsync(Guid userId, string username)
{
    KeyCredentialRetrievalResult keyCreationResult = await KeyCredentialManager.RequestCreateAsync(username, KeyCredentialCreationOption.ReplaceExisting);

    switch (keyCreationResult.Status)
    {
        case KeyCredentialStatus.Success:
            Debug.WriteLine("Successfully made key");
            await GetKeyAttestationAsync(userId, keyCreationResult);
            return true;
        case KeyCredentialStatus.UserCanceled:
            Debug.WriteLine("User cancelled sign-in process.");
            break;
        case KeyCredentialStatus.NotFound:
            // User needs to setup Windows Hello
            Debug.WriteLine($"Windows Hello is not set up!{Environment.NewLine}Please go to Windows Settings and set up a PIN to use it.");
            break;
        default:
            break;
    }

    return false;
}

在 WindowsHelloHelper.cs 中建立 GetKeyAttestationAsync 方法。此方法將示範如何取得 Windows Hello 在特定裝置上每個帳號所能提供的所有必要資訊。

using Windows.Storage.Streams;

private static async Task GetKeyAttestationAsync(Guid userId, KeyCredentialRetrievalResult keyCreationResult)
{
    KeyCredential userKey = keyCreationResult.Credential;
    IBuffer publicKey = userKey.RetrievePublicKey();
    KeyCredentialAttestationResult keyAttestationResult = await userKey.GetAttestationAsync();
    IBuffer keyAttestation = null;
    IBuffer certificateChain = null;
    bool keyAttestationIncluded = false;
    bool keyAttestationCanBeRetrievedLater = false;
    KeyCredentialAttestationStatus keyAttestationRetryType = 0;

    if (keyAttestationResult.Status == KeyCredentialAttestationStatus.Success)
    {
        keyAttestationIncluded = true;
        keyAttestation = keyAttestationResult.AttestationBuffer;
        certificateChain = keyAttestationResult.CertificateChainBuffer;
        Debug.WriteLine("Successfully made key and attestation");
    }
    else if (keyAttestationResult.Status == KeyCredentialAttestationStatus.TemporaryFailure)
    {
        keyAttestationRetryType = KeyCredentialAttestationStatus.TemporaryFailure;
        keyAttestationCanBeRetrievedLater = true;
        Debug.WriteLine("Successfully made key but not attestation");
    }
    else if (keyAttestationResult.Status == KeyCredentialAttestationStatus.NotSupported)
    {
        keyAttestationRetryType = KeyCredentialAttestationStatus.NotSupported;
        keyAttestationCanBeRetrievedLater = false;
        Debug.WriteLine("Key created, but key attestation not supported");
    }

    Guid deviceId = Helpers.GetDeviceId();

    //Update the Windows Hello details with the information we have just fetched above.
    //await UpdateWindowsHelloDetailsAsync(userId, deviceId, publicKey.ToArray(), keyAttestationResult);
}

你可能注意到在 GetKeyAttestationAsync 方法中，你剛剛新增的最後一行被註解掉了。這最後一行會是你建立的新方法，會把所有Windows Hello資訊傳送到 AuthService。在真實世界中，您必須透過 Web API 將此內容傳送至實際伺服器。

using System.Runtime.InteropServices.WindowsRuntime;
using System.Threading.Tasks;

public static async Task<bool> UpdateWindowsHelloDetailsAsync(Guid userId, Guid deviceId, byte[] publicKey, KeyCredentialAttestationResult keyAttestationResult)
{
    //In the real world, you would use an API to add Windows Hello signing info to server for the signed in account.
    //For this tutorial, we do not implement a Web API for our server and simply mock the server locally.
    //The CreateWindowsHelloKey method handles adding the Windows Hello account locally to the device using the KeyCredential Manager

    //Using the userId the existing account should be found and updated.
    await AuthService.AuthService.Instance.WindowsHelloUpdateDetailsAsync(userId, deviceId, publicKey, keyAttestationResult);
    return true;
}

在 GetKeyAttestationAsync 方法中取消註解最後一行，讓Windows Hello資訊傳送到 AuthService。
建置並執行應用程式，並使用預設認證登入，如同先前一樣。在 [ 歡迎使用 ] 頁面上，您現在會看到裝置標識碼已顯示。如果您在另一個裝置上登入，那麼該裝置也會顯示在此處（如果您使用雲端託管的驗證服務）。針對這個動手實驗室，將顯示裝置ID。在實際的實作中，您會想要顯示易記名稱，讓人員瞭解並使用來識別每個裝置。

為了完成這個實作實驗室，當您從用戶選擇頁面中選擇並重新登入時，需要執行對使用者的請求和挑戰。 AuthService 有您設計用來發出挑戰請求的兩個方法，其中一個是使用已簽署挑戰的方式。在 WindowsHelloHelper.cs中，建立名為 RequestSignAsync 的新方法。這會向 AuthService 請求挑戰，並用 Windows Hello API 本地簽署該挑戰，並將簽署的挑戰傳送至 AuthService。在此實作實驗課中，AuthService 將會收到已簽署的挑戰並傳回 true。在實際的實作中，您必須實作驗證機制，以判斷挑戰是否已由正確裝置上的正確用戶簽署。將下列方法新增至WindowsHelloHelper.cs

private static async Task<bool> RequestSignAsync(Guid userId, KeyCredentialRetrievalResult openKeyResult)
{
    // Calling userKey.RequestSignAsync() prompts the uses to enter the PIN or use Biometrics (Windows Hello).
    // The app would use the private key from the user account to sign the sign-in request (challenge)
    // The client would then send it back to the server and await the servers response.
    IBuffer challengeMessage = AuthService.AuthService.Instance.WindowsHelloRequestChallenge();
    KeyCredential userKey = openKeyResult.Credential;
    KeyCredentialOperationResult signResult = await userKey.RequestSignAsync(challengeMessage);

    if (signResult.Status == KeyCredentialStatus.Success)
    {
        // If the challenge from the server is signed successfully
        // send the signed challenge back to the server and await the servers response
        return AuthService.AuthService.Instance.SendServerSignedChallenge(
            userId, Helpers.GetDeviceId(), signResult.Result.ToArray());
    }
    else if (signResult.Status == KeyCredentialStatus.UserCanceled)
    {
        // User cancelled the Windows Hello PIN entry.
    }
    else if (signResult.Status == KeyCredentialStatus.NotFound)
    {
        // Must recreate Windows Hello key
    }
    else if (signResult.Status == KeyCredentialStatus.SecurityDeviceLocked)
    {
        // Can't use Windows Hello right now, remember that hardware failed and suggest restart
    }
    else if (signResult.Status == KeyCredentialStatus.UnknownError)
    {
        // Can't use Windows Hello right now, try again later
    }

    return false;
}

在 WindowsHelloHelper 類別中，從 GetWindowsHelloAuthenticationMessageAsync 方法呼叫 RequestSignAsync 方法。

public static async Task<bool> GetWindowsHelloAuthenticationMessageAsync(UserAccount account)
{
    KeyCredentialRetrievalResult openKeyResult = await KeyCredentialManager.OpenAsync(account.Username);
    // Calling OpenAsync will allow the user access to what is available in the app and will not require user credentials again.
    // If you wanted to force the user to sign in again you can use the following:
    // var consentResult = await Windows.Security.Credentials.UI.UserConsentVerifier.RequestVerificationAsync(account.Username);
    // This will ask for the either the password of the currently signed in Microsoft Account or the PIN used for Windows Hello.

    if (openKeyResult.Status == KeyCredentialStatus.Success)
    {
        //If OpenAsync has succeeded, the next thing to think about is whether the client application requires access to backend services.
        //If it does here you would Request a challenge from the Server. The client would sign this challenge and the server
        //would check the signed challenge. If it is correct it would allow the user access to the backend.
        //You would likely make a new method called RequestSignAsync to handle all this
        //for example, RequestSignAsync(openKeyResult);
        //Refer to the second Windows Hello sample for information on how to do this.

        return await RequestSignAsync(account.UserId, openKeyResult);
    }
    else if (openKeyResult.Status == KeyCredentialStatus.NotFound)
    {
        //If the _account is not found at this stage. It could be one of two errors. 
        //1. Windows Hello has been disabled
        //2. Windows Hello has been disabled and re-enabled cause the Windows Hello Key to change.
        //Calling CreateWindowsHelloKeyAsync and passing through the account will attempt to replace the existing Windows Hello Key for that account.
        //If the error really is that Windows Hello is disabled then the CreateWindowsHelloKeyAsync method will output that error.
        if (await CreateWindowsHelloKeyAsync(account.UserId, account.Username))
        {
            //If the Windows Hello Key was again successfully created, Windows Hello has just been reset.
            //Now that the Windows Hello Key has been reset for the _account retry sign in.
            return await GetWindowsHelloAuthenticationMessageAsync(account);
        }
    }

    // Can't use Windows Hello right now, try again later
    return false;
}

在此練習中，您已更新用戶端應用程式以使用 AuthService。如此一來，您就能夠消除 Account 類別和 AccountHelper 類別的需求。刪除 Utils 資料夾中的 Account 類別、Models 資料夾和 AccountHelper 類別。在解決方案成功建置之前，您必須移除整個應用程式中所有對 WindowsHelloLogin.Models 命名空間的參考。
建立並執行應用程式，享受使用 Windows Hello 與模擬服務與資料庫的樂趣。

在這個實作實驗室中，你學會了如何使用 Windows Hello API 來取代在 Windows 機器上使用驗證時的密碼需求。當你考慮到人們維護密碼和支援現有系統遺失密碼所花費的精力時，你應該能理解這套新的 Windows Hello 認證系統帶來的好處。

我們將如何在服務和伺服器端實作驗證的詳情留給您處理。預計大多數開發者會有現有系統需要遷移，才能開始使用 Windows Hello。每個系統的詳細數據將會有所不同。

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Last updated on 2026-03-11

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