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//
// Mono.Security.Protocol.Ntlm.ChallengeResponse
// Implements Challenge Response for NTLM v1
//
// Author:
// Sebastien Pouliot <sebastien@ximian.com>
//
// (C) 2003 Motus Technologies Inc. (http://www.motus.com)
// (C) 2004 Novell (http://www.novell.com)
//
// References
// a. NTLM Authentication Scheme for HTTP, Ronald Tschalär
// http://www.innovation.ch/java/ntlm.html
// b. The NTLM Authentication Protocol, Copyright © 2003 Eric Glass
// http://davenport.sourceforge.net/ntlm.html
//
using System;
using System.Globalization;
using System.Security.Cryptography;
using System.Text;
using Mono.Security.Cryptography;
namespace Mono.Security.Protocol.Ntlm {
public class ChallengeResponse : IDisposable {
static private byte[] magic = { 0x4B, 0x47, 0x53, 0x21, 0x40, 0x23, 0x24, 0x25 };
// This is the pre-encrypted magic value with a null DES key (0xAAD3B435B51404EE)
// Ref: http://packetstormsecurity.nl/Crackers/NT/l0phtcrack/l0phtcrack2.5-readme.html
static private byte[] nullEncMagic = { 0xAA, 0xD3, 0xB4, 0x35, 0xB5, 0x14, 0x04, 0xEE };
private bool _disposed;
private byte[] _challenge;
private byte[] _lmpwd;
private byte[] _ntpwd;
// constructors
public ChallengeResponse ()
{
_disposed = false;
_lmpwd = new byte [21];
_ntpwd = new byte [21];
}
public ChallengeResponse (string password, byte[] challenge) : this ()
{
Password = password;
Challenge = challenge;
}
~ChallengeResponse ()
{
if (!_disposed)
Dispose ();
}
// properties
public string Password {
get { return null; }
set {
if (_disposed)
throw new ObjectDisposedException ("too late");
// create Lan Manager password
DES des = DES.Create ();
des.Mode = CipherMode.ECB;
ICryptoTransform ct = null;
// Note: In .NET DES cannot accept a weak key
// this can happen for a null password
if ((value == null) || (value.Length < 1)) {
Buffer.BlockCopy (nullEncMagic, 0, _lmpwd, 0, 8);
}
else {
des.Key = PasswordToKey (value, 0);
ct = des.CreateEncryptor ();
ct.TransformBlock (magic, 0, 8, _lmpwd, 0);
}
// and if a password has less than 8 characters
if ((value == null) || (value.Length < 8)) {
Buffer.BlockCopy (nullEncMagic, 0, _lmpwd, 8, 8);
}
else {
des.Key = PasswordToKey (value, 7);
ct = des.CreateEncryptor ();
ct.TransformBlock (magic, 0, 8, _lmpwd, 8);
}
// create NT password
MD4 md4 = MD4.Create ();
byte[] data = ((value == null) ? (new byte [0]) : (Encoding.Unicode.GetBytes (value)));
byte[] hash = md4.ComputeHash (data);
Buffer.BlockCopy (hash, 0, _ntpwd, 0, 16);
// clean up
Array.Clear (data, 0, data.Length);
Array.Clear (hash, 0, hash.Length);
des.Clear ();
}
}
public byte[] Challenge {
get { return null; }
set {
if (value == null)
throw new ArgumentNullException ("Challenge");
if (_disposed)
throw new ObjectDisposedException ("too late");
// we don't want the caller to modify the value afterward
_challenge = (byte[]) value.Clone ();
}
}
public byte[] LM {
get {
if (_disposed)
throw new ObjectDisposedException ("too late");
return GetResponse (_lmpwd);
}
}
public byte[] NT {
get {
if (_disposed)
throw new ObjectDisposedException ("too late");
return GetResponse (_ntpwd);
}
}
// IDisposable method
public void Dispose ()
{
Dispose (true);
GC.SuppressFinalize (this);
}
private void Dispose (bool disposing)
{
if (!_disposed) {
// cleanup our stuff
Array.Clear (_lmpwd, 0, _lmpwd.Length);
Array.Clear (_ntpwd, 0, _ntpwd.Length);
if (_challenge != null)
Array.Clear (_challenge, 0, _challenge.Length);
_disposed = true;
}
}
// private methods
private byte[] GetResponse (byte[] pwd)
{
byte[] response = new byte [24];
DES des = DES.Create ();
des.Mode = CipherMode.ECB;
des.Key = PrepareDESKey (pwd, 0);
ICryptoTransform ct = des.CreateEncryptor ();
ct.TransformBlock (_challenge, 0, 8, response, 0);
des.Key = PrepareDESKey (pwd, 7);
ct = des.CreateEncryptor ();
ct.TransformBlock (_challenge, 0, 8, response, 8);
des.Key = PrepareDESKey (pwd, 14);
ct = des.CreateEncryptor ();
ct.TransformBlock (_challenge, 0, 8, response, 16);
return response;
}
private byte[] PrepareDESKey (byte[] key56bits, int position)
{
// convert to 8 bytes
byte[] key = new byte [8];
key [0] = key56bits [position];
key [1] = (byte) ((key56bits [position] << 7) | (key56bits [position + 1] >> 1));
key [2] = (byte) ((key56bits [position + 1] << 6) | (key56bits [position + 2] >> 2));
key [3] = (byte) ((key56bits [position + 2] << 5) | (key56bits [position + 3] >> 3));
key [4] = (byte) ((key56bits [position + 3] << 4) | (key56bits [position + 4] >> 4));
key [5] = (byte) ((key56bits [position + 4] << 3) | (key56bits [position + 5] >> 5));
key [6] = (byte) ((key56bits [position + 5] << 2) | (key56bits [position + 6] >> 6));
key [7] = (byte) (key56bits [position + 6] << 1);
return key;
}
private byte[] PasswordToKey (string password, int position)
{
byte[] key7 = new byte [7];
int len = System.Math.Min (password.Length - position, 7);
Encoding.ASCII.GetBytes (password.ToUpper (CultureInfo.CurrentCulture), position, len, key7, 0);
byte[] key8 = PrepareDESKey (key7, 0);
// cleanup intermediate key material
Array.Clear (key7, 0, key7.Length);
return key8;
}
}
}
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