Crypto Manager Code

#region License
//    CryptoManager - Logiciel de chiffrement de fichiers
//    Copyright (C) 2008  G. Villard
//
//    This program is free software; you can redistribute it and/or modify
//    it under the terms of the GNU General Public License as published by
//    the Free Software Foundation; either version 2 of the License, or
//    (at your option) any later version.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU General Public License for more details.
//
//    You should have received a copy of the GNU General Public License along
//    with this program; if not, write to the Free Software Foundation, Inc.,
//    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#endregion

using System;
using System.Runtime.InteropServices;
using System.Security;
using System.Windows.Forms;

namespace CryptoManager {
	
	internal partial class GetSecureString : Form {
		
		#region Constructeur
		public GetSecureString() {
			InitializeComponent();
		}
		#endregion
		
		#region Variables
		private SecureString _password = new SecureString();
		private SecureString _check = new SecureString();
		#endregion
		
		#region Gestion de l'entrée clavier
		private void TextboxKeyDown(object sender, KeyEventArgs e) {
			TextBox tb = sender as TextBox;
			if(tb == null)
				return;
			SecureString ss = tb == tbPass ? _password : _check;
			
			char c = (char)e.KeyValue;
			int start = tb.SelectionStart;
			int len = tb.SelectionLength;
			
			switch(e.KeyCode) {
				case Keys.Back:
					e.SuppressKeyPress = true;
					e.Handled = true;
					if(start == 0) {
						return;
					}
					if(tb.SelectionLength > 0) {
						for(int i = 0; i < len; i++)
							ss.RemoveAt(start);
						tb.Text = new string('*', ss.Length);
						tb.SelectionStart = start;
					} else {
						ss.RemoveAt(--start);
						tb.Text = new string('*', ss.Length);
						tb.SelectionStart = start;
					}
					return;
					
				case Keys.Delete:
					e.SuppressKeyPress = true;
					e.Handled = true;
					if(start == ss.Length) {
						return;
					}
					if(tb.SelectionLength > 0) {
						for(int i = 0; i < len; i++)
							ss.RemoveAt(start);
						tb.Text = new string('*', ss.Length);
						tb.SelectionStart = start;
					} else {
						ss.RemoveAt(start);
						tb.Text = new string('*', ss.Length);
						tb.SelectionStart = start;
					}
					return;
					
				case Keys.Left:
					e.SuppressKeyPress = true;
					e.Handled = true;
					if(start > 0)
						tb.SelectionStart = --start;
					return;
					
				case Keys.Right:
					e.SuppressKeyPress = true;
					e.Handled = true;
					if(start < tb.Text.Length)
						tb.SelectionStart = ++start;
					return;
					
				case Keys.Home:
					e.SuppressKeyPress = true;
					e.Handled = true;
					tb.SelectionStart = 0;
					return;
					
				case Keys.End:
					e.SuppressKeyPress = true;
					e.Handled = true;
					tb.SelectionStart = tb.Text.Length;
					return;
					
				case Keys.Enter:
					e.SuppressKeyPress = true;
					e.Handled = true;
					_password.MakeReadOnly();
					_check.MakeReadOnly();
					this.DialogResult = DialogResult.OK;
					return;
					
				case Keys.Escape:
					e.SuppressKeyPress = true;
					e.Handled = true;
					_password.MakeReadOnly();
					_check.MakeReadOnly();
					this.DialogResult = DialogResult.Cancel;
					return;
					
					// Les touches à annuler le traitement
				case Keys.Up:
				case Keys.Down:
				case Keys.PageDown:
				case Keys.PageUp:
				case Keys.Insert:
					e.SuppressKeyPress = true;
					e.Handled = true;
					break;
					
				default:
					if(!char.IsLetterOrDigit(c) && !char.IsPunctuation(c) && !char.IsWhiteSpace(c))
						return;
					break;
			}
			
			if(char.IsDigit(c) || char.IsPunctuation(c) || char.IsLetter(c) || char.IsWhiteSpace(c)) {
				e.SuppressKeyPress = true;
				e.Handled = true;
				if(char.IsLetterOrDigit(c) || char.IsPunctuation(c)) {
					if(Control.IsKeyLocked(Keys.CapsLock) ^ e.Shift)
						c = char.ToUpper(c);
					else
						c = char.ToLower(c);
				}
				if(tb.SelectionLength > 0) {
					for(int i = 0; i < len; i++)
						ss.RemoveAt(start);
				}
				ss.InsertAt(start, c);
				tb.Text = new string('*', ss.Length);
				tb.SelectionStart = start + 1;
			}
		}
		#endregion
		
		#region Chargement
		private void Chargement(object sender, EventArgs e) {
			this.TopMost = true;
			this.Activate();
		}
		#endregion
		
		#region Demande de password
		public SecureString ShowDialog(bool withCheck) {
			// On cache le champ de vérificatino si nécessaire
			if(!withCheck) {
				tbVerif.Hide();
				tbValider.Top -= 26;
				tbCancel.Top -= 26;
				this.Height -= 8;
			}
			
			if(base.ShowDialog() != DialogResult.OK)
				return null;
			
			if(_password.Length == 0) {
				MessageBox.Show("pwdempty".GetResString(), "err".GetResString(), MessageBoxButtons.OK, MessageBoxIcon.Error);
				return null;
			}
			
			// Si on demande une vérification de password, il faut faire les tests
			if(withCheck) {
				if(_password.Length != _check.Length) {
					MessageBox.Show("pwdcheckfail".GetResString(), "err".GetResString(), MessageBoxButtons.OK, MessageBoxIcon.Error);
					return null;
				}
				byte[] pass = new byte[_password.Length], check = new byte[_check.Length];
				IntPtr p1 = IntPtr.Zero, p2 = IntPtr.Zero;
				bool rst = true;
				try {
					p1 = Marshal.SecureStringToBSTR(_password);
					p2 = Marshal.SecureStringToBSTR(_check);
					Marshal.Copy(p1, pass, 0, _password.Length);
					Marshal.Copy(p2, check, 0, _check.Length);
					for(int i = 0; i < _password.Length; i++) {
						if(pass[i] != check[i])
							rst = false;
					}
				} catch(Exception ex) {
					MessageBox.Show(ex.Message);
					MessageBox.Show(ex.StackTrace);
				}
				finally {
					if(p1 != IntPtr.Zero)
						Marshal.ZeroFreeBSTR(p1);
					if(p2 != IntPtr.Zero)
						Marshal.ZeroFreeBSTR(p2);
					if(pass != null)
						pass.FillWithZero();
					if(check != null)
						check.FillWithZero();
				}
				if(!rst) {
					MessageBox.Show("pwdcheckfail".GetResString(), "err".GetResString(), MessageBoxButtons.OK, MessageBoxIcon.Error);
					return null;
				}
			}
			return _password.Copy();
		}
		public static SecureString Demand(bool withCheck = true) {
			GetSecureString gss = new GetSecureString();
			SecureString rst = gss.ShowDialog(withCheck);
			gss.Dispose();
			return rst;
		}
		#endregion
		
		#region Bouttons de validation/annulation
		private void Valider(object sender, EventArgs e) {
			_password.MakeReadOnly();
			_check.MakeReadOnly();
			this.DialogResult = DialogResult.OK;
		}
		
		private void Annuler(object sender, EventArgs e) {
			_password.MakeReadOnly();
			_check.MakeReadOnly();
			this.DialogResult = DialogResult.Cancel;
		}
		#endregion
		
	}
	
}