WindowsImpersonationContext Classe

Definição

Namespace:

System.Security.Principal

Assembly:

mscorlib.dll

Representa o usuário do Windows antes de uma operação de representação.

public ref class WindowsImpersonationContext : IDisposable

[System.Runtime.InteropServices.ComVisible(true)]
public class WindowsImpersonationContext : IDisposable

[<System.Runtime.InteropServices.ComVisible(true)>]
type WindowsImpersonationContext = class
    interface IDisposable

Public Class WindowsImpersonationContext
Implements IDisposable

Herança

Object

WindowsImpersonationContext

Atributos

ComVisibleAttribute

Implementações

IDisposable

Exemplos

O exemplo a seguir demonstra como representar um usuário e, em seguida, reverter para a identidade original.

// This sample demonstrates the use of the WindowsIdentity class to impersonate a user.
// IMPORTANT NOTES: 
// This sample requests the user to enter a password on the console screen.
// Because the console window does not support methods allowing the password to be masked,
// it will be visible to anyone viewing the screen.
// On Windows Vista and later this sample must be run as an administrator. 

#using <System.dll>

using namespace System;
using namespace System::Runtime::InteropServices;
using namespace System::Security::Principal;
using namespace System::Security::Permissions;


[DllImport("advapi32.dll",SetLastError=true)]
bool LogonUser( String^ lpszUsername, String^ lpszDomain, String^ lpszPassword, int dwLogonType, int dwLogonProvider, IntPtr * phToken );

[DllImport("kernel32.dll",CharSet=CharSet::Auto)]
bool CloseHandle( IntPtr handle );

// Test harness.
// If you incorporate this code into a DLL, be sure to demand FullTrust.

[PermissionSetAttribute(SecurityAction::Demand,Name="FullTrust")]
int main()
{
   IntPtr tokenHandle = IntPtr(0);

   try
   {
      String^ userName;
      String^ domainName;
      
      // Get the user token for the specified user, domain, and password using the 
      // unmanaged LogonUser method.  
      // The local machine name can be used for the domain name to impersonate a user on this machine.
      Console::Write( "Enter the name of the domain on which to log on: " );
      domainName = Console::ReadLine();
      Console::Write( "Enter the login of a user on {0} that you wish to impersonate: ", domainName );
      userName = Console::ReadLine();
      Console::Write( "Enter the password for {0}: ", userName );
      const int LOGON32_PROVIDER_DEFAULT = 0;
      
      //This parameter causes LogonUser to create a primary token.
      const int LOGON32_LOGON_INTERACTIVE = 2;
      const int SecurityImpersonation = 2;
      tokenHandle = IntPtr::Zero;
      
      // Call LogonUser to obtain a handle to an access token.
      bool returnValue = LogonUser( userName, domainName, Console::ReadLine(), LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,  &tokenHandle );
      Console::WriteLine( "LogonUser called." );
      if ( false == returnValue )
      {
         int ret = Marshal::GetLastWin32Error();
         Console::WriteLine( "LogonUser failed with error code : {0}", ret );
         throw gcnew System::ComponentModel::Win32Exception( ret );
      }
      Console::WriteLine( "Did LogonUser Succeed? {0}", (returnValue ? (String^)"Yes" : "No") );
      Console::WriteLine( "Value of Windows NT token: {0}", tokenHandle );
      
      // Check the identity.
      Console::WriteLine( "Before impersonation: {0}", WindowsIdentity::GetCurrent()->Name );
      
      // The token that is passed to the following constructor must 
      // be a primary token in order to use it for impersonation.
      WindowsIdentity^ newId = gcnew WindowsIdentity( tokenHandle );
      WindowsImpersonationContext^ impersonatedUser = newId->Impersonate();
      
      // Check the identity.
      Console::WriteLine( "After impersonation: {0}", WindowsIdentity::GetCurrent()->Name );
      
      // Stop impersonating the user.
      impersonatedUser->Undo();
      
      // Check the identity.
      Console::WriteLine( "After Undo: {0}", WindowsIdentity::GetCurrent()->Name );
      
      // Free the tokens.
      if ( tokenHandle != IntPtr::Zero )
            CloseHandle( tokenHandle );
   }
   catch ( Exception^ ex ) 
   {
      Console::WriteLine( "Exception occurred. {0}", ex->Message );
   }

}

// This sample demonstrates the use of the WindowsIdentity class to impersonate a user.
// IMPORTANT NOTES:
// This sample requests the user to enter a password on the console screen.
// Because the console window does not support methods allowing the password to be masked,
// it will be visible to anyone viewing the screen.
// On Windows Vista and later this sample must be run as an administrator.

using System;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.Security.Permissions;
using Microsoft.Win32.SafeHandles;
using System.Runtime.ConstrainedExecution;
using System.Security;

public class ImpersonationDemo
{
    [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    public static extern bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword,
        int dwLogonType, int dwLogonProvider, out SafeTokenHandle phToken);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
    public extern static bool CloseHandle(IntPtr handle);

    // Test harness.
    // If you incorporate this code into a DLL, be sure to demand FullTrust.
    [PermissionSetAttribute(SecurityAction.Demand, Name = "FullTrust")]
    public static void Main(string[] args)
    {
        SafeTokenHandle safeTokenHandle;
        try
        {
            string userName, domainName;
            // Get the user token for the specified user, domain, and password using the
            // unmanaged LogonUser method.
            // The local machine name can be used for the domain name to impersonate a user on this machine.
            Console.Write("Enter the name of the domain on which to log on: ");
            domainName = Console.ReadLine();

            Console.Write("Enter the login of a user on {0} that you wish to impersonate: ", domainName);
            userName = Console.ReadLine();

            Console.Write("Enter the password for {0}: ", userName);

            const int LOGON32_PROVIDER_DEFAULT = 0;
            //This parameter causes LogonUser to create a primary token.
            const int LOGON32_LOGON_INTERACTIVE = 2;

            // Call LogonUser to obtain a handle to an access token.
            bool returnValue = LogonUser(userName, domainName, Console.ReadLine(),
                LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,
                out safeTokenHandle);

            Console.WriteLine("LogonUser called.");

            if (false == returnValue)
            {
                int ret = Marshal.GetLastWin32Error();
                Console.WriteLine("LogonUser failed with error code : {0}", ret);
                throw new System.ComponentModel.Win32Exception(ret);
            }
            using (safeTokenHandle)
            {
                Console.WriteLine("Did LogonUser Succeed? " + (returnValue ? "Yes" : "No"));
                Console.WriteLine("Value of Windows NT token: " + safeTokenHandle);

                // Check the identity.
                Console.WriteLine("Before impersonation: "
                    + WindowsIdentity.GetCurrent().Name);
                // Use the token handle returned by LogonUser.
                using (WindowsIdentity newId = new WindowsIdentity(safeTokenHandle.DangerousGetHandle()))
                {
                    using (WindowsImpersonationContext impersonatedUser = newId.Impersonate())
                    {

                        // Check the identity.
                        Console.WriteLine("After impersonation: "
                            + WindowsIdentity.GetCurrent().Name);
                    }
                }
                // Releasing the context object stops the impersonation
                // Check the identity.
                Console.WriteLine("After closing the context: " + WindowsIdentity.GetCurrent().Name);
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("Exception occurred. " + ex.Message);
        }
    }
}
public sealed class SafeTokenHandle : SafeHandleZeroOrMinusOneIsInvalid
{
    private SafeTokenHandle()
        : base(true)
    {
    }

    [DllImport("kernel32.dll")]
    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
    [SuppressUnmanagedCodeSecurity]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool CloseHandle(IntPtr handle);

    protected override bool ReleaseHandle()
    {
        return CloseHandle(handle);
    }
}

' This sample demonstrates the use of the WindowsIdentity class to impersonate a user.
' IMPORTANT NOTES: 
' This sample requests the user to enter a password on the console screen.
' Because the console window does not support methods allowing the password to be masked,
' it will be visible to anyone viewing the screen.
' On Windows Vista and later this sample must be run as an administrator. 

Imports System.Runtime.InteropServices
Imports System.Security.Principal
Imports System.Security.Permissions
Imports Microsoft.Win32.SafeHandles
Imports System.Runtime.ConstrainedExecution
Imports System.Security

Module Module1

    Public Class ImpersonationDemo

        'Private Declare Auto Function LogonUser Lib "advapi32.dll" (ByVal lpszUsername As [String], _
        '    ByVal lpszDomain As [String], ByVal lpszPassword As [String], _
        '    ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, _
        '    ByRef phToken As IntPtr) As Boolean

        Private Declare Auto Function LogonUser Lib "advapi32.dll" (ByVal lpszUsername As [String], _
            ByVal lpszDomain As [String], ByVal lpszPassword As [String], _
            ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, _
            <Out()> ByRef phToken As SafeTokenHandle) As Boolean

        Public Declare Auto Function CloseHandle Lib "kernel32.dll" (ByVal handle As IntPtr) As Boolean

        ' Test harness.
        ' If you incorporate this code into a DLL, be sure to demand FullTrust.
        <PermissionSetAttribute(SecurityAction.Demand, Name:="FullTrust")> _
        Public Overloads Shared Sub Main(ByVal args() As String)
            Dim safeTokenHandle As SafeTokenHandle = Nothing
            Dim tokenHandle As New IntPtr(0)
            Try


                Dim userName, domainName As String

                ' Get the user token for the specified user, domain, and password using the 
                ' unmanaged LogonUser method.  
                ' The local machine name can be used for the domain name to impersonate a user on this machine.
                Console.Write("Enter the name of a domain on which to log on: ")
                domainName = Console.ReadLine()

                Console.Write("Enter the login of a user on {0} that you wish to impersonate: ", domainName)
                userName = Console.ReadLine()

                Console.Write("Enter the password for {0}: ", userName)

                Const LOGON32_PROVIDER_DEFAULT As Integer = 0
                'This parameter causes LogonUser to create a primary token.
                Const LOGON32_LOGON_INTERACTIVE As Integer = 2

                ' Call LogonUser to obtain a handle to an access token.
                Dim returnValue As Boolean = LogonUser(userName, domainName, Console.ReadLine(), LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, safeTokenHandle)

                Console.WriteLine("LogonUser called.")

                If False = returnValue Then
                    Dim ret As Integer = Marshal.GetLastWin32Error()
                    Console.WriteLine("LogonUser failed with error code : {0}", ret)
                    Throw New System.ComponentModel.Win32Exception(ret)

                    Return
                End If
                Using safeTokenHandle
                    Dim success As String
                    If returnValue Then success = "Yes" Else success = "No"
                    Console.WriteLine(("Did LogonUser succeed? " + success))
                    Console.WriteLine(("Value of Windows NT token: " + safeTokenHandle.DangerousGetHandle().ToString()))

                    ' Check the identity.
                    Console.WriteLine(("Before impersonation: " + WindowsIdentity.GetCurrent().Name))

                    ' Use the token handle returned by LogonUser.
                    Using newId As New WindowsIdentity(safeTokenHandle.DangerousGetHandle())
                        Using impersonatedUser As WindowsImpersonationContext = newId.Impersonate()

                            ' Check the identity.
                            Console.WriteLine(("After impersonation: " + WindowsIdentity.GetCurrent().Name))

                            ' Free the tokens.
                        End Using
                    End Using
                End Using
            Catch ex As Exception
                Console.WriteLine(("Exception occurred. " + ex.Message))
            End Try
        End Sub
    End Class
End Module

Public NotInheritable Class SafeTokenHandle
    Inherits SafeHandleZeroOrMinusOneIsInvalid

    Private Sub New()
        MyBase.New(True)

    End Sub

    Private Declare Auto Function LogonUser Lib "advapi32.dll" (ByVal lpszUsername As [String], _
            ByVal lpszDomain As [String], ByVal lpszPassword As [String], _
            ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, _
            ByRef phToken As IntPtr) As Boolean
    <DllImport("kernel32.dll"), ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success), SuppressUnmanagedCodeSecurity()> _
    Private Shared Function CloseHandle(ByVal handle As IntPtr) As <MarshalAs(UnmanagedType.Bool)> Boolean

    End Function
    Protected Overrides Function ReleaseHandle() As Boolean
        Return CloseHandle(handle)

    End Function 'ReleaseHandle
End Class

Comentários

Essa classe reverte a identidade de um usuário depois que o usuário representa outro usuário.

Importante

Esse tipo implementa a interface IDisposable. Quando você terminar de usar o tipo, deverá descartá-lo direta ou indiretamente. Para descartar o tipo diretamente, chame o método Dispose dele em um bloco try/catch. Para descartá-lo indiretamente, use um constructo de linguagem como using ( em C#) ou Using (em Visual Basic). Saiba mais na seção "Como usar um objeto que implementa IDisposable" no tópico da interface IDisposable.

Métodos

Dispose()	Libera todos os recursos usados pelo WindowsImpersonationContext.
Dispose(Boolean)	Libera os recursos não gerenciados usados pelo WindowsImpersonationContext e opcionalmente libera os recursos gerenciados.
Equals(Object)	Determina se o objeto especificado é igual ao objeto atual. (Herdado de Object)
GetHashCode()	Serve como a função de hash padrão. (Herdado de Object)
GetType()	Obtém o Type da instância atual. (Herdado de Object)
MemberwiseClone()	Cria uma cópia superficial do Object atual. (Herdado de Object)
ToString()	Retorna uma cadeia de caracteres que representa o objeto atual. (Herdado de Object)
Undo()	Reverte o contexto de usuário para o usuário do Windows representado por este objeto.