Marshal.ZeroFreeGlobalAllocUnicode-Methode: (IntPtr)
Veröffentlicht: Oktober 2016
Hinweis
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Gibt einen nicht verwalteten Zeichenfolgenzeiger frei, der mit der SecureStringToGlobalAllocUnicode-Methode reserviert wurde.
Namespace: System.Runtime.InteropServices
Assembly: mscorlib (in mscorlib.dll)
Syntax
[SecurityCriticalAttribute]
public static void ZeroFreeGlobalAllocUnicode(
IntPtr s
)
public:
[SecurityCriticalAttribute]
static void ZeroFreeGlobalAllocUnicode(
IntPtr s
)
[<SecurityCriticalAttribute>]
static member ZeroFreeGlobalAllocUnicode :
s:nativeint -> unit
<SecurityCriticalAttribute>
Public Shared Sub ZeroFreeGlobalAllocUnicode (
s As IntPtr
)
Parameter
s
Type: System.IntPtrDie Adresse der nicht verwalteten Zeichenfolge, die freigegeben werden soll.
Hinweise
Die ZeroFreeGlobalAllocUnicode Methode zuerst Nullen und dann freigegeben nicht verwalteten Speicher, der belegt wurde mithilfe der SecureStringToGlobalAllocUnicode Methode.
Beispiele
Im folgenden Beispiel wird veranschaulicht, wie die SecureStringToGlobalAllocUnicode Methode mit dem nicht verwalteten LogonUser Funktion zum Ausführen der Identitätswechsel mit den SecureString Klasse. Anschließend wird die ZeroFreeGlobalAllocUnicode Methode 0 (null) und des Verweis nicht verwalteten Zeichenfolge.
using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Principal;
class Example
{
// Define the Windows LogonUser and CloseHandle functions.
[DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
internal static extern bool LogonUser(String username, String domain, IntPtr password,
int logonType, int logonProvider, ref IntPtr token);
[DllImport("kernel32.dll", CharSet = CharSet.Auto)]
public extern static bool CloseHandle(IntPtr handle);
// Define the required LogonUser enumerations.
const int LOGON32_PROVIDER_DEFAULT = 0;
const int LOGON32_LOGON_INTERACTIVE = 2;
static void Main()
{
// Display the current user before impersonation.
Console.WriteLine("Before impersonation: {0}",
WindowsIdentity.GetCurrent().Name);
// Ask the user for a network domain.
Console.Write("Please enter your domain: ");
string domain = Console.ReadLine();
// Ask the user for a user name.
Console.Write("Please enter your user name: ");
string username = Console.ReadLine();
// Ask the user for a password.
Console.Write("Please enter your password: ");
SecureString passWord = GetPassword();
// Impersonate the account provided by the user.
try {
WindowsImpersonationContext userContext =
ImpersonateUser(passWord, username, domain);
// Display the current user after impersonation.
Console.WriteLine("After impersonation: {0}",
WindowsIdentity.GetCurrent().Name);
}
catch (ArgumentException e) {
Console.WriteLine("{0}: {1}", e.GetType().Name, e.Message);
}
catch (Win32Exception e) {
Console.WriteLine("{0}: {1}", e.GetType().Name, e.Message);
}
finally {
passWord.Dispose();
}
}
public static SecureString GetPassword()
{
SecureString password = new SecureString();
// get the first character of the password
ConsoleKeyInfo nextKey = Console.ReadKey(true);
while (nextKey.Key != ConsoleKey.Enter) {
if (nextKey.Key == ConsoleKey.Backspace) {
if (password.Length > 0) {
password.RemoveAt(password.Length - 1);
// erase the last * as well
Console.Write(nextKey.KeyChar);
Console.Write(" ");
Console.Write(nextKey.KeyChar);
}
}
else {
password.AppendChar(nextKey.KeyChar);
Console.Write("*");
}
nextKey = Console.ReadKey(true);
}
Console.WriteLine();
// lock the password down
password.MakeReadOnly();
return password;
}
public static WindowsImpersonationContext ImpersonateUser(SecureString password, string userName, string domainName)
{
IntPtr tokenHandle = IntPtr.Zero;
IntPtr passwordPtr = IntPtr.Zero;
bool returnValue = false;
int error = 0;
// Marshal the SecureString to unmanaged memory.
passwordPtr = Marshal.SecureStringToGlobalAllocUnicode(password);
// Pass LogonUser the unmanaged (and decrypted) copy of the password.
returnValue = LogonUser(userName, domainName, passwordPtr,
LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,
ref tokenHandle);
if (!returnValue && tokenHandle == IntPtr.Zero)
error = Marshal.GetLastWin32Error();
// Perform cleanup whether or not the call succeeded.
// Zero-out and free the unmanaged string reference.
Marshal.ZeroFreeGlobalAllocUnicode(passwordPtr);
// Close the token handle.
CloseHandle(tokenHandle);
// Throw an exception if an error occurred.
if (error != 0) {
throw new System.ComponentModel.Win32Exception(error);
}
// The token that is passed to the following constructor must
// be a primary token in order to use it for impersonation.
WindowsIdentity newId = new WindowsIdentity(tokenHandle);
return newId.Impersonate();
}
}
Imports System
Imports System.ComponentModel
Imports System.Runtime.InteropServices
Imports System.Security
Imports System.Security.Principal
Module Example
' PInvoke into the Win32 API to provide access to the
' LogonUser and CloseHandle functions.
<DllImport("advapi32.dll", SetLastError:=True, CharSet:=CharSet.Unicode)> _
Function LogonUser(ByVal username As String, ByVal domain As String, _
ByVal password As IntPtr, ByVal logonType As Integer, _
ByVal logonProvider As Integer, ByRef token As IntPtr) _
As Boolean
End Function
<DllImport("kernel32.dll", CharSet:=CharSet.Auto)> _
Function CloseHandle(ByVal handle As IntPtr) As Boolean
End Function
' Define the required LogonUser enumerations.
Const LOGON32_PROVIDER_DEFAULT As Integer = 0
Const LOGON32_LOGON_INTERACTIVE As Integer = 2
Sub Main(ByVal args() As String)
' Display the current user before impersonation.
Console.WriteLine("Before impersonation: {0}",
WindowsIdentity.GetCurrent().Name)
' Ask the user for a network domain.
Console.Write("Please enter your domain:")
Dim domain As String = Console.ReadLine()
' Ask the user for a user name.
Console.Write("Please enter your user name:")
Dim username As String = Console.ReadLine()
' Ask the user for a password.
Console.Write("Please enter your password:")
Dim passWord As SecureString = GetPassword()
' Impersonate the account provided by the user.
Try
Dim userContext As WindowsImpersonationContext =
ImpersonateUser(passWord, username, domain)
' Display the current user after impersonation.
Console.WriteLine("After impersonation: {0}",
WindowsIdentity.GetCurrent().Name)
Catch e As ArgumentException
Console.WriteLine(e.Message)
Console.WriteLine("{0}: {1}", e.GetType().Name, e.Message)
Catch e As Win32Exception
Console.WriteLine("{0}: {1}", e.GetType().Name, e.Message)
Finally
passWord.Dispose()
End Try
End Sub
Function GetPassword() As SecureString
Dim password As New SecureString()
' get the first character of the password
Dim nextKey As ConsoleKeyInfo = Console.ReadKey(True)
While nextKey.Key <> ConsoleKey.Enter
If nextKey.Key = ConsoleKey.BackSpace Then
If password.Length > 0 Then
password.RemoveAt(password.Length - 1)
' erase the last * as well
Console.Write(nextKey.KeyChar)
Console.Write(" ")
Console.Write(nextKey.KeyChar)
End If
Else
password.AppendChar(nextKey.KeyChar)
Console.Write("*")
End If
nextKey = Console.ReadKey(True)
End While
Console.WriteLine()
' lock the password down
password.MakeReadOnly()
Return password
End Function
Function ImpersonateUser(ByVal password As SecureString,
ByVal userName As String,
ByVal domainName As String) As WindowsImpersonationContext
Dim tokenHandle As IntPtr = IntPtr.Zero
Dim passwordPtr As IntPtr = IntPtr.Zero
Dim returnValue As Boolean = False
Dim err As Integer = 0
' Marshal the SecureString to unmanaged memory.
passwordPtr = Marshal.SecureStringToGlobalAllocUnicode(password)
' Pass LogonUser the unmanaged (and decrypted) copy of the password.
returnValue = LogonUser(userName, domainName, passwordPtr,
LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,
tokenHandle)
If Not returnValue AndAlso tokenHandle = IntPtr.Zero Then
err = Marshal.GetLastWin32Error()
End If
' Perform cleanup whether or not the call succeeded.
' Zero-out and free the unmanaged string reference.
Marshal.ZeroFreeGlobalAllocUnicode(passwordPtr)
' Close the token handle.
CloseHandle(tokenHandle)
' Throw an exception if an error occurred.
If err <> 0 Then
Throw New System.ComponentModel.Win32Exception(err)
End If
' The token that is passed to the following constructor must
' be a primary token in order to use it for impersonation.
Dim newId As New WindowsIdentity(tokenHandle)
Return newId.Impersonate()
End Function
End Module
Sicherheit
requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.
Versionsinformationen
Universelle Windows-Plattform
Verfügbar seit 8
.NET Framework
Verfügbar seit 2.0
Portierbare Klassenbibliothek
Unterstützt in: portierbare .NET-Plattformen
Windows Phone
Verfügbar seit 8.1
Siehe auch
Marshal-Klasse
System.Runtime.InteropServices-Namespace
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