/* pwdbased.hpp                                
 *
 * Copyright (C) 2003 Sawtooth Consulting Ltd.
 *
 * This file is part of yaSSL.
 *
 * yaSSL 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.
 *
 * There are special exceptions to the terms and conditions of the GPL as it
 * is applied to yaSSL. View the full text of the exception in the file
 * FLOSS-EXCEPTIONS in the directory of this software distribution.
 *
 * yaSSL 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

/* pwdbased.hpp defines PBKDF2 from PKCS #5
*/


#ifndef TAO_CRYPT_PWDBASED_HPP
#define TAO_CRYPT_PWDBASED_HPP

#include <string.h>
#include "misc.hpp"
#include "block.hpp"
#include "hmac.hpp"

namespace TaoCrypt {


// From PKCS #5, T must be type suitable for HMAC<T> 
template <class T>
class PBKDF2_HMAC {
public:
    word32 MaxDerivedKeyLength() const { return 0xFFFFFFFFU;} // avoid overflow

    word32 DeriveKey(byte* derived, word32 dLen, const byte* pwd, word32 pLen,
                     const byte* salt, word32 sLen, word32 iterations) const;
}; 



template <class T>
word32 PBKDF2_HMAC<T>::DeriveKey(byte* derived, word32 dLen, const byte* pwd,
                                 word32 pLen, const byte* salt, word32 sLen,
                                 word32 iterations) const
{
	assert(dLen <= MaxDerivedKeyLength());
	assert(iterations > 0);

    ByteBlock buffer(T::DIGEST_SIZE);
	HMAC<T>   hmac;

    hmac.SetKey(pwd, pLen);

	word32 i = 1;

	while (dLen > 0) {
		hmac.Update(salt, sLen);
		word32 j;
		for (j = 0; j < 4; j++) {
			byte b = i >> ((3-j)*8);
			hmac.Update(&b, 1);
		}
		hmac.Final(buffer.get_buffer());

		word32 segmentLen = min(dLen, buffer.size());
		memcpy(derived, buffer.get_buffer(), segmentLen);

		for (j = 1; j < iterations; j++) {
			hmac.Update(buffer.get_buffer(), buffer.size());
            hmac.Final(buffer.get_buffer());
			xorbuf(derived, buffer.get_buffer(), segmentLen);
		}
		derived += segmentLen;
		dLen    -= segmentLen;
		i++;
	}
	return iterations;
}




} // naemspace

#endif // TAO_CRYPT_PWDBASED_HPP