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Marshal.SecureStringToCoTaskMemAnsi Method

.NET Framework 2.0

Note: This method is new in the .NET Framework version 2.0.

Copies the contents of a managed SecureString object to a block of memory allocated from the unmanaged COM task allocator.

Namespace: System.Runtime.InteropServices
Assembly: mscorlib (in mscorlib.dll)

Syntax

C++

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public static IntPtr SecureStringToCoTaskMemAnsi (
	SecureString s
)

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public static IntPtr SecureStringToCoTaskMemAnsi (
	SecureString s
)

JScript

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public static function SecureStringToCoTaskMemAnsi (
	s : SecureString
) : IntPtr

Parameters

s: The managed SecureString object to copy.

Return Value

The address, in unmanaged memory, where the s parameter was copied to, or 0 if a null SecureString object was supplied.

Exceptions

Exception type	Condition
ArgumentNullException	The s parameter is a null reference (Nothing in Visual Basic).
NotSupportedException	The current computer is not running Microsoft Windows 2000 Service Pack 3 or later.
OutOfMemoryException	There is insufficient memory available.

Remarks

The SecureStringToCoTaskMemAnsi method is useful for custom marshaling or when mixing managed and unmanaged code. Because this method allocates the unmanaged memory required for a string, always free the memory by calling ZeroFreeCoTaskMemAnsi. The characters of the string are copied as ANSI characters.

Note
This method uses SecurityAction.LinkDemand to prevent it from being called from untrusted code; only the immediate caller is required to have SecurityPermissionAttribute.UnmanagedCode permission. If your code can be called from partially trusted code, do not pass user input to Marshal class methods without validation. For important limitations on using the LinkDemand member, see Demand vs. LinkDemand.

Note

This method uses SecurityAction.LinkDemand to prevent it from being called from untrusted code; only the immediate caller is required to have SecurityPermissionAttribute.UnmanagedCode permission. If your code can be called from partially trusted code, do not pass user input to Marshal class methods without validation. For important limitations on using the LinkDemand member, see Demand vs. LinkDemand.

Notes to Callers This method is supported only on computers running Microsoft Windows 2000 Service Pack 3 or later.

Example

The following code example uses the SecureStringToCoTaskMemAnsi method to marshal and decrypt the contents of a SecureString object to a block of unmanaged memory. It then uses the ZeroFreeCoTaskMemAnsi method to zero out and dispose the unmanaged block.

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using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Principal;
using System.Text;

namespace SecureStringExample
{

    class MarshalExample
    {


        static void Main(string[] args)
        {
            IntPtr unmanagedRef = IntPtr.Zero;

            try
            {
                // Ask the user for a password.
                Console.Write("Please enter your password:");

                SecureString passWord = GetPassword();

                Console.WriteLine("Copying and decrypting the string to unmanaged memory...");

                // Copy the Secure string to unmanaged memory (and decrypt it).
                unmanagedRef = Marshal.SecureStringToCoTaskMemAnsi(passWord);


            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            finally
            {
                if (unmanagedRef != IntPtr.Zero)
                {
                    Console.WriteLine("Zeroing out unmanaged memory...");

                    Marshal.ZeroFreeCoTaskMemAnsi(unmanagedRef);
                }

            }

            Console.WriteLine("Done.");

            Console.ReadLine();


        }

        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;
        }
    }
}

.NET Framework Security

SecurityPermission for permission to call unmanaged code. Associated enumeration: UnmanagedCode Security action: LinkDemand

Platforms

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

Version Information

.NET Framework

Supported in: 2.0

Reference

Marshal Class
Marshal Members
System.Runtime.InteropServices Namespace

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