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/*
* Copyright (c) 2010 SURFnet bv
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
* IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
* IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*****************************************************************************
RFC4880.cpp
Implements a secure password-based key derivation scheme. It is not a generic
implementation of the RFC but only generates 256-bit AES keys according to
the "iterated and salted" scheme.
*****************************************************************************/
#include "config.h"
#include "RFC4880.h"
#include "CryptoFactory.h"
#include "HashAlgorithm.h"
// This function derives a 256-bit AES key from the supplied password data
bool RFC4880::PBEDeriveKey(const ByteString& password, ByteString& salt, AESKey** ppKey)
{
// Check that a proper salt value was supplied; it should be at least 8 bytes long
if (salt.size() < 8)
{
ERROR_MSG("Insufficient salt data supplied for password-based encryption");
return false;
}
// Check other parameters
if ((password.size() == 0) || (ppKey == NULL))
{
return false;
}
// Determine the iteration count based on the last byte of the salt
unsigned int iter = PBE_ITERATION_BASE_COUNT + salt[salt.size() - 1];
// Get a hash instance
HashAlgorithm* hash = CryptoFactory::i()->getHashAlgorithm(HashAlgo::SHA256);
if (hash == NULL)
{
ERROR_MSG("Could not get a SHA-256 instance");
return false;
}
// Perform the first iteration which takes as input the salt value and
// the password
ByteString intermediate;
if (!hash->hashInit() ||
!hash->hashUpdate(salt) ||
!hash->hashUpdate(password) ||
!hash->hashFinal(intermediate))
{
ERROR_MSG("Hashing failed");
CryptoFactory::i()->recycleHashAlgorithm(hash);
return false;
}
// Perform the remaining iteration
while (--iter > 0)
{
if (!hash->hashInit() ||
!hash->hashUpdate(intermediate) ||
!hash->hashFinal(intermediate))
{
ERROR_MSG("Hashing failed");
CryptoFactory::i()->recycleHashAlgorithm(hash);
return false;
}
}
// Create the AES key instance
*ppKey = new AESKey(256);
(*ppKey)->setKeyBits(intermediate);
// Release the hash instance
CryptoFactory::i()->recycleHashAlgorithm(hash);
return true;
}
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