我遇到了绑定到密码盒的问题。这似乎是一个安全风险，但我正在使用MVVM模式，所以我希望绕过这个。我在这里发现了一些有趣的代码(有人使用过这个或类似的代码吗?)
http://www.wpftutorial.net/PasswordBox.html
从技术上讲，它看起来很棒，但我不确定如何检索密码。
我基本上有属性在我的LoginViewModel用户名和密码。用户名是好的，正在工作，因为它是一个文本框。
我使用上面的代码，并输入这个
<PasswordBox ff:PasswordHelper.Attach="True"
ff:PasswordHelper.Password="{Binding Path=Password}" Width="130"/>
当我有PasswordBox作为一个文本框和绑定路径=密码，然后在我的LoginViewModel属性更新。
我的代码非常简单，基本上我有一个命令为我的按钮。当我按下它CanLogin被调用，如果它返回真，它调用Login。
你可以看到，我检查了我的用户名属性，这很好。
在登录我发送到我的服务的用户名和密码，用户名包含数据从我的视图，但密码是空|空
private DelegateCommand loginCommand;
public string Username { get; set; }
public string Password { get; set; }
public ICommand LoginCommand
{
get
{
if (loginCommand == null)
{
loginCommand = new DelegateCommand(
Login, CanLogin );
}
return loginCommand;
}
}
private bool CanLogin()
{
return !string.IsNullOrEmpty(Username);
}
private void Login()
{
bool result = securityService.IsValidLogin(Username, Password);
if (result) { }
else { }
}
这就是我正在做的
<TextBox Text="{Binding Path=Username, UpdateSourceTrigger=PropertyChanged}"
MinWidth="180" />
<PasswordBox ff:PasswordHelper.Attach="True"
ff:PasswordHelper.Password="{Binding Path=Password}" Width="130"/>
我有我的文本框，这是没有问题的，但在我的ViewModel密码是空的。
是我做错了什么还是漏了一步?
我放了一个断点，果然代码进入静态助手类，但它从不更新我的ViewModel中的密码。
我想我应该把我的解决方案放在一起，因为这是一个很常见的问题……拥有大量的选择总是一件好事。
I simply wrapped a PasswordBox in a UserControl and implemented a DependencyProperty to be able to bind. I'm doing everything I can to avoid storing any clear text in the memory, so everything is done through a SecureString and the PasswordBox.Password property. During the foreach loop, each character does get exposed, but it's very brief. Honestly, if you're worried about your WPF application to be compromised from this brief exposure, you've got bigger security issues that should be handled.
这样做的好处是你没有违反任何MVVM规则，即使是“最纯粹的”规则，因为这是一个UserControl，所以它允许有代码隐藏。当你使用它时，你可以在View和ViewModel之间进行纯通信，而你的VideModel不知道View的任何部分或密码的来源。只要确保你在ViewModel中绑定到SecureString。
BindablePasswordBox.xaml
<UserControl x:Class="BK.WPF.CustomControls.BindanblePasswordBox"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d" d:DesignHeight="22" d:DesignWidth="150">
<PasswordBox x:Name="PswdBox"/>
</UserControl>
BindablePasswordBox.xaml.cs(版本1 -不支持双向绑定)
using System.ComponentModel;
using System.Security;
using System.Windows;
using System.Windows.Controls;
namespace BK.WPF.CustomControls
{
public partial class BindanblePasswordBox : UserControl
{
public static readonly DependencyProperty PasswordProperty =
DependencyProperty.Register("Password", typeof(SecureString), typeof(BindanblePasswordBox));
public SecureString Password
{
get { return (SecureString)GetValue(PasswordProperty); }
set { SetValue(PasswordProperty, value); }
}
public BindanblePasswordBox()
{
InitializeComponent();
PswdBox.PasswordChanged += PswdBox_PasswordChanged;
}
private void PswdBox_PasswordChanged(object sender, RoutedEventArgs e)
{
var secure = new SecureString();
foreach (var c in PswdBox.Password)
{
secure.AppendChar(c);
}
Password = secure;
}
}
}
版本1的用法:
<local:BindanblePasswordBox Width="150" HorizontalAlignment="Center"
VerticalAlignment="Center"
Password="{Binding Password, Mode=OneWayToSource}"/>
BindablePasswordBox.xaml.cs(版本2 -支持双向绑定)
public partial class BindablePasswordBox : UserControl
{
public static readonly DependencyProperty PasswordProperty =
DependencyProperty.Register("Password", typeof(SecureString), typeof(BindablePasswordBox),
new PropertyMetadata(PasswordChanged));
public SecureString Password
{
get { return (SecureString)GetValue(PasswordProperty); }
set { SetValue(PasswordProperty, value); }
}
public BindablePasswordBox()
{
InitializeComponent();
PswdBox.PasswordChanged += PswdBox_PasswordChanged;
}
private void PswdBox_PasswordChanged(object sender, RoutedEventArgs e)
{
var secure = new SecureString();
foreach (var c in PswdBox.Password)
{
secure.AppendChar(c);
}
if (Password != secure)
{
Password = secure;
}
}
private static void PasswordChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var pswdBox = d as BindablePasswordBox;
if (pswdBox != null && e.NewValue != e.OldValue)
{
var newValue = e.NewValue as SecureString;
if (newValue == null)
{
return;
}
var unmanagedString = IntPtr.Zero;
string newString;
try
{
unmanagedString = Marshal.SecureStringToGlobalAllocUnicode(newValue);
newString = Marshal.PtrToStringUni(unmanagedString);
}
finally
{
Marshal.ZeroFreeGlobalAllocUnicode(unmanagedString);
}
var currentValue = pswdBox.PswdBox.Password;
if (currentValue != newString)
{
pswdBox.PswdBox.Password = newString;
}
}
}
}
版本2的用途:
<local:BindanblePasswordBox Width="150" HorizontalAlignment="Center"
VerticalAlignment="Center"
Password="{Binding Password, Mode=TwoWay}"/>
一个不违反MVVM模式的简单解决方案是在ViewModel中引入一个获取密码的事件(或委托)。
在ViewModel中:
public event eventandler <HarvestPasswordEventArgs> HarvestPassword;
使用这些EventArgs:
class HarvestPasswordEventArgs : EventArgs
{
public string Password;
}
在View中，订阅创建ViewModel时的事件，并填写密码值。
_viewModel.HarvestPassword += (sender, args) =>
args.Password = passwordBox1.Password;
在ViewModel中，当你需要密码时，你可以触发事件并从那里获取密码:
if (HarvestPassword == null)
//bah
return;
var pwargs = new HarvestPasswordEventArgs();
HarvestPassword(this, pwargs);
LoginHelpers.Login(Username, pwargs.Password);
我花了大量时间研究各种解决方案。我不喜欢装饰器的想法，行为弄乱了验证UI，背后的代码……真的吗?
最好的方法是坚持自定义附加属性，并绑定到视图模型中的SecureString属性。尽量把它放在里面。当你需要快速访问纯密码时，使用下面的代码将其临时转换为不安全的字符串:
namespace Namespace.Extensions
{
using System;
using System.Runtime.InteropServices;
using System.Security;
/// <summary>
/// Provides unsafe temporary operations on secured strings.
/// </summary>
[SuppressUnmanagedCodeSecurity]
public static class SecureStringExtensions
{
/// <summary>
/// Converts a secured string to an unsecured string.
/// </summary>
public static string ToUnsecuredString(this SecureString secureString)
{
// copy&paste from the internal System.Net.UnsafeNclNativeMethods
IntPtr bstrPtr = IntPtr.Zero;
if (secureString != null)
{
if (secureString.Length != 0)
{
try
{
bstrPtr = Marshal.SecureStringToBSTR(secureString);
return Marshal.PtrToStringBSTR(bstrPtr);
}
finally
{
if (bstrPtr != IntPtr.Zero)
Marshal.ZeroFreeBSTR(bstrPtr);
}
}
}
return string.Empty;
}
/// <summary>
/// Copies the existing instance of a secure string into the destination, clearing the destination beforehand.
/// </summary>
public static void CopyInto(this SecureString source, SecureString destination)
{
destination.Clear();
foreach (var chr in source.ToUnsecuredString())
{
destination.AppendChar(chr);
}
}
/// <summary>
/// Converts an unsecured string to a secured string.
/// </summary>
public static SecureString ToSecuredString(this string plainString)
{
if (string.IsNullOrEmpty(plainString))
{
return new SecureString();
}
SecureString secure = new SecureString();
foreach (char c in plainString)
{
secure.AppendChar(c);
}
return secure;
}
}
}
确保允许GC收集UI元素，因此不要为PasswordBox上的PasswordChanged事件使用静态事件处理程序。
我还发现了一个异常，当使用SecurePassword属性设置它时，控件没有更新UI，这就是为什么我将密码复制到password的原因。
namespace Namespace.Controls
{
using System.Security;
using System.Windows;
using System.Windows.Controls;
using Namespace.Extensions;
/// <summary>
/// Creates a bindable attached property for the <see cref="PasswordBox.SecurePassword"/> property.
/// </summary>
public static class PasswordBoxHelper
{
// an attached behavior won't work due to view model validation not picking up the right control to adorn
public static readonly DependencyProperty SecurePasswordBindingProperty = DependencyProperty.RegisterAttached(
"SecurePassword",
typeof(SecureString),
typeof(PasswordBoxHelper),
new FrameworkPropertyMetadata(new SecureString(),FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, AttachedPropertyValueChanged)
);
private static readonly DependencyProperty _passwordBindingMarshallerProperty = DependencyProperty.RegisterAttached(
"PasswordBindingMarshaller",
typeof(PasswordBindingMarshaller),
typeof(PasswordBoxHelper),
new PropertyMetadata()
);
public static void SetSecurePassword(PasswordBox element, SecureString secureString)
{
element.SetValue(SecurePasswordBindingProperty, secureString);
}
public static SecureString GetSecurePassword(PasswordBox element)
{
return element.GetValue(SecurePasswordBindingProperty) as SecureString;
}
private static void AttachedPropertyValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
// we'll need to hook up to one of the element's events
// in order to allow the GC to collect the control, we'll wrap the event handler inside an object living in an attached property
// don't be tempted to use the Unloaded event as that will be fired even when the control is still alive and well (e.g. switching tabs in a tab control)
var passwordBox = (PasswordBox)d;
var bindingMarshaller = passwordBox.GetValue(_passwordBindingMarshallerProperty) as PasswordBindingMarshaller;
if (bindingMarshaller == null)
{
bindingMarshaller = new PasswordBindingMarshaller(passwordBox);
passwordBox.SetValue(_passwordBindingMarshallerProperty, bindingMarshaller);
}
bindingMarshaller.UpdatePasswordBox(e.NewValue as SecureString);
}
/// <summary>
/// Encapsulated event logic
/// </summary>
private class PasswordBindingMarshaller
{
private readonly PasswordBox _passwordBox;
private bool _isMarshalling;
public PasswordBindingMarshaller(PasswordBox passwordBox)
{
_passwordBox = passwordBox;
_passwordBox.PasswordChanged += this.PasswordBoxPasswordChanged;
}
public void UpdatePasswordBox(SecureString newPassword)
{
if (_isMarshalling)
{
return;
}
_isMarshalling = true;
try
{
// setting up the SecuredPassword won't trigger a visual update so we'll have to use the Password property
_passwordBox.Password = newPassword.ToUnsecuredString();
// you may try the statement below, however the benefits are minimal security wise (you still have to extract the unsecured password for copying)
//newPassword.CopyInto(_passwordBox.SecurePassword);
}
finally
{
_isMarshalling = false;
}
}
private void PasswordBoxPasswordChanged(object sender, RoutedEventArgs e)
{
// copy the password into the attached property
if (_isMarshalling)
{
return;
}
_isMarshalling = true;
try
{
SetSecurePassword(_passwordBox, _passwordBox.SecurePassword.Copy());
}
finally
{
_isMarshalling = false;
}
}
}
}
}
以及XAML用法:
<PasswordBox controls:PasswordBoxHelper.SecurePassword="{Binding LogonPassword, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}">
我在视图模型中的属性是这样的:
[RequiredSecureString]
public SecureString LogonPassword
{
get
{
return _logonPassword;
}
set
{
_logonPassword = value;
NotifyPropertyChanged(nameof(LogonPassword));
}
}
RequiredSecureString只是一个简单的自定义验证器，它有以下逻辑:
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = true)]
public class RequiredSecureStringAttribute:ValidationAttribute
{
public RequiredSecureStringAttribute()
:base("Field is required")
{
}
public override bool IsValid(object value)
{
return (value as SecureString)?.Length > 0;
}
}
给你。一个完整的和经过测试的纯MVVM解决方案。
