Building Security Awareness in .NET Assemblies : Part 1 - Learn to break a .NET Assembly

////////////////////////////////////////////////////////////////////////////
/// Building Security Awareness in .Net Assemblies 
/// Part 1
/// CrackingIL.sln
/// Developed by: Chua Wen Ching
/// Email me: chuawenching@necoders.com
/// Visit us: http://www.necoders.com
////////////////////////////////////////////////////////////////////////////

using System;
using System.ComponentModel;
using System.Security.Permissions;
using System.Windows.Forms;

// need this to call the RegistryKey
using Microsoft.Win32;

[assembly: IsolatedStorageFilePermission(SecurityAction.RequestMinimum, UserQuota=1048576)]
namespace CrackingIL
{
	/// <summary>
	/// Summary description for Form1.
	/// </summary>
	public class FrmSecureApp : Form
	{
		private Label lblHeader;
		/// <summary>
		/// Required designer variable.
		/// </summary>
		private Container components = null;

		public FrmSecureApp()
		{
			//
			// Required for Windows Form Designer support
			//
			InitializeComponent();

			//
			// TODO: Add any constructor code after InitializeComponent call
			//
		}

		/// <summary>
		/// Clean up any resources being used.
		/// </summary>
		protected override void Dispose( bool disposing )
		{
			if( disposing )
			{
				if (components != null) 
				{
					components.Dispose();
				}
			}
			base.Dispose( disposing );
		}

		#region Windows Form Designer generated code
		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{
			this.lblHeader = new System.Windows.Forms.Label();
			this.SuspendLayout();
			// 
			// lblHeader
			// 
			this.lblHeader.Font = new System.Drawing.Font("Arial", 15.75F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0)));
			this.lblHeader.Location = new System.Drawing.Point(24, 16);
			this.lblHeader.Name = "lblHeader";
			this.lblHeader.Size = new System.Drawing.Size(216, 136);
			this.lblHeader.TabIndex = 0;
			this.lblHeader.Text = "Welcome To NeCoders";
			// 
			// FrmSecureApp
			// 
			this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
			this.ClientSize = new System.Drawing.Size(292, 173);
			this.Controls.Add(this.lblHeader);
			this.Name = "FrmSecureApp";
			this.Text = "Secure App v1.0";
			this.Load += new System.EventHandler(this.FrmSecureApp_Load);
			this.ResumeLayout(false);

		}
		#endregion

		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main() 
		{
			Application.Run(new FrmSecureApp());
		}

		/// <summary>
		/// Verifies the registry to make sure the serial number is in there
		/// </summary>
		/// <param name="sender"></param>
		/// <param name="e"></param>
		private void FrmSecureApp_Load(object sender, EventArgs e)
		{
			RegistryKey key = Registry.LocalMachine.OpenSubKey(@"Software\Necoders");

			if (key == null)
			{
				MessageBox.Show("Please acquire a license to run this!");
				this.Dispose(true);				
			}
			else
			{
				string validSerial = "1111-1111-1111-1111";

				if ((string)key.GetValue("serial") == validSerial)
				{
					return;
				}
				else if (key.GetValue("serial") == null)
				{
					MessageBox.Show("Please acquire a license to run this!");
					this.Dispose(true);
				}
				else
				{
					MessageBox.Show("Wrong serial number");
					this.Dispose(true);
				}
			}
		}
	}
}