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//
// Rfc2898DeriveBytes.cs: RFC2898 (PKCS#5 v2) Key derivation for Password Based Encryption
//
// Author:
// Sebastien Pouliot (sebastien@ximian.com)
//
// (C) 2003 Motus Technologies Inc. (http://www.motus.com)
// Copyright (C) 2004-2007 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
#if NET_2_0
using System.Runtime.InteropServices;
using System.Text;
using Mono.Security.Cryptography;
namespace System.Security.Cryptography {
[ComVisible (true)]
public class Rfc2898DeriveBytes : DeriveBytes {
private const int defaultIterations = 1000;
private int _iteration;
private byte[] _salt;
private HMACSHA1 _hmac;
private byte[] _buffer;
private int _pos;
private int _f;
// constructors
public Rfc2898DeriveBytes (string password, byte[] salt)
: this (password, salt, defaultIterations)
{
}
public Rfc2898DeriveBytes (string password, byte[] salt, int iterations)
{
if (password == null)
throw new ArgumentNullException ("password");
Salt = salt;
IterationCount = iterations;
_hmac = new HMACSHA1 (Encoding.UTF8.GetBytes (password));
}
public Rfc2898DeriveBytes (byte[] password, byte[] salt, int iterations)
{
if (password == null)
throw new ArgumentNullException ("password");
Salt = salt;
IterationCount = iterations;
_hmac = new HMACSHA1 (password);
}
public Rfc2898DeriveBytes (string password, int saltSize)
: this (password, saltSize, defaultIterations)
{
}
public Rfc2898DeriveBytes (string password, int saltSize, int iterations)
{
if (password == null)
throw new ArgumentNullException ("password");
if (saltSize < 0)
throw new ArgumentOutOfRangeException ("invalid salt length");
Salt = KeyBuilder.Key (saltSize);
IterationCount = iterations;
_hmac = new HMACSHA1 (Encoding.UTF8.GetBytes (password));
}
// properties
public int IterationCount {
get { return _iteration; }
set {
if (value < 1)
throw new ArgumentOutOfRangeException ("IterationCount < 1");
_iteration = value;
}
}
public byte[] Salt {
get { return (byte[]) _salt.Clone (); }
set {
if (value == null)
throw new ArgumentNullException ("Salt");
if (value.Length < 8)
throw new ArgumentException ("Salt < 8 bytes");
_salt = (byte[])value.Clone ();
}
}
// methods
private byte[] F (byte[] s, int c, int i)
{
s [s.Length - 4] = (byte)(i >> 24);
s [s.Length - 3] = (byte)(i >> 16);
s [s.Length - 2] = (byte)(i >> 8);
s [s.Length - 1] = (byte)i;
// this is like j=0
byte[] u1 = _hmac.ComputeHash (s);
byte[] data = u1;
// so we start at j=1
for (int j=1; j < c; j++) {
byte[] un = _hmac.ComputeHash (data);
// xor
for (int k=0; k < 20; k++)
u1 [k] = (byte)(u1 [k] ^ un [k]);
data = un;
}
return u1;
}
public override byte[] GetBytes (int cb)
{
if (cb < 1)
throw new ArgumentOutOfRangeException ("cb");
int l = cb / 20; // HMACSHA1 == 160 bits == 20 bytes
int r = cb % 20; // remainder
if (r != 0)
l++; // rounding up
byte[] result = new byte [cb];
int rpos = 0;
if (_pos > 0) {
int count = Math.Min (20 - _pos, cb);
Buffer.BlockCopy (_buffer, _pos, result, 0, count);
if (count >= cb)
return result;
_pos = 0;
rpos = count;
}
byte[] data = new byte [_salt.Length + 4];
Buffer.BlockCopy (_salt, 0, data, 0, _salt.Length);
for (int i=1; i <= l; i++) {
_buffer = F (data, _iteration, ++_f);
// we may not need the complete last block
int count = ((i == l) ? result.Length - rpos : 20);
Buffer.BlockCopy (_buffer, _pos, result, rpos, count);
rpos += _pos + count;
_pos = ((count == 20) ? 0 : count);
}
return result;
}
public override void Reset ()
{
_buffer = null;
_pos = 0;
_f = 0;
}
}
}
#endif
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