Marshal.SecureStringToGlobalAllocAnsi(SecureString) Method

Definition

Namespace:

System.Runtime.InteropServices

Assemblies:

netstandard.dll, System.Runtime.InteropServices.dll

Source:

Marshal.cs

Important

This API is not CLS-compliant.

Copies the contents of a managed SecureString into unmanaged memory, converting into ANSI format as it copies.

C#

public static IntPtr SecureStringToGlobalAllocAnsi(System.Security.SecureString s);

Parameters

s

SecureString

The managed object to copy.

Returns

IntPtr

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

Exceptions

ArgumentNullException

The s parameter is null.

OutOfMemoryException

There is insufficient memory available.

Examples

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

C#

using System;
using System.Runtime.InteropServices;
using System.Security;

class Example
{
    static void Main()
    {
        IntPtr unmanagedRef = IntPtr.Zero;

        // 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.SecureStringToGlobalAllocAnsi(passWord);
        passWord.Dispose();

        if (unmanagedRef != IntPtr.Zero) {
            Console.WriteLine("Zeroing out unmanaged memory...");
            Marshal.ZeroFreeGlobalAllocAnsi(unmanagedRef);
        }
        Console.WriteLine("Done.");
    }

    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;
    }
}
// The example displays output like the following:
//       Please enter your password: ********
//       Copying and decrypting the string to unmanaged memory...
//       Zeroing out unmanaged memory...
//       Done.

Remarks

The SecureStringToGlobalAllocAnsi 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 the ZeroFreeGlobalAllocAnsi method.

Applies to