我认为最好 SecureString 依赖函数将它们的依赖逻辑封装在匿名函数中，以便更好地控制内存中的解密字符串（一旦固定）。
在这个 sn-p 中解密 SecureStrings 的实现将：
- 将字符串固定在内存中（这是您想要做的，但这里的大多数答案似乎都缺少）。
- 将 its reference 传递给 Func/Action 委托。
- 从内存中清除它并释放
finally 块中的 GC。
与依赖不太理想的替代方案相比，这显然使“标准化”和维护调用者变得容易得多：
- 从
string DecryptSecureString(...) 帮助函数返回解密后的字符串。
- 在需要的地方复制此代码。
请注意，您有两种选择：
-
static T DecryptSecureString<T> 允许您从调用者访问Func 委托的结果（如DecryptSecureStringWithFunc 测试方法中所示）。
-
static void DecryptSecureString 只是一个“无效”版本，在您实际上不想/不需要返回任何东西的情况下使用 Action 委托（如 DecryptSecureStringWithAction 测试方法中所示）。
两者的示例用法可以在包含的StringsTest 类中找到。
Strings.cs
using System;
using System.Runtime.InteropServices;
using System.Security;
namespace SecurityUtils
{
public partial class Strings
{
/// <summary>
/// Passes decrypted password String pinned in memory to Func delegate scrubbed on return.
/// </summary>
/// <typeparam name="T">Generic type returned by Func delegate</typeparam>
/// <param name="action">Func delegate which will receive the decrypted password pinned in memory as a String object</param>
/// <returns>Result of Func delegate</returns>
public static T DecryptSecureString<T>(SecureString secureString, Func<string, T> action)
{
var insecureStringPointer = IntPtr.Zero;
var insecureString = String.Empty;
var gcHandler = GCHandle.Alloc(insecureString, GCHandleType.Pinned);
try
{
insecureStringPointer = Marshal.SecureStringToGlobalAllocUnicode(secureString);
insecureString = Marshal.PtrToStringUni(insecureStringPointer);
return action(insecureString);
}
finally
{
//clear memory immediately - don't wait for garbage collector
fixed(char* ptr = insecureString )
{
for(int i = 0; i < insecureString.Length; i++)
{
ptr[i] = '\0';
}
}
insecureString = null;
gcHandler.Free();
Marshal.ZeroFreeGlobalAllocUnicode(insecureStringPointer);
}
}
/// <summary>
/// Runs DecryptSecureString with support for Action to leverage void return type
/// </summary>
/// <param name="secureString"></param>
/// <param name="action"></param>
public static void DecryptSecureString(SecureString secureString, Action<string> action)
{
DecryptSecureString<int>(secureString, (s) =>
{
action(s);
return 0;
});
}
}
}
StringsTest.cs
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Security;
namespace SecurityUtils.Test
{
[TestClass]
public class StringsTest
{
[TestMethod]
public void DecryptSecureStringWithFunc()
{
// Arrange
var secureString = new SecureString();
foreach (var c in "UserPassword123".ToCharArray())
secureString.AppendChar(c);
secureString.MakeReadOnly();
// Act
var result = Strings.DecryptSecureString<bool>(secureString, (password) =>
{
return password.Equals("UserPassword123");
});
// Assert
Assert.IsTrue(result);
}
[TestMethod]
public void DecryptSecureStringWithAction()
{
// Arrange
var secureString = new SecureString();
foreach (var c in "UserPassword123".ToCharArray())
secureString.AppendChar(c);
secureString.MakeReadOnly();
// Act
var result = false;
Strings.DecryptSecureString(secureString, (password) =>
{
result = password.Equals("UserPassword123");
});
// Assert
Assert.IsTrue(result);
}
}
}
显然，这并不能防止以下列方式滥用此功能，因此请注意不要这样做：
[TestMethod]
public void DecryptSecureStringWithAction()
{
// Arrange
var secureString = new SecureString();
foreach (var c in "UserPassword123".ToCharArray())
secureString.AppendChar(c);
secureString.MakeReadOnly();
// Act
string copyPassword = null;
Strings.DecryptSecureString(secureString, (password) =>
{
copyPassword = password; // Please don't do this!
});
// Assert
Assert.IsNull(copyPassword); // Fails
}
编码愉快！