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/*
* pbkdf2.c
* --------
* PBKDF2 (RFC 2898) on top of HAL interface to Cryptech hash cores.
*
* Authors: Rob Austein
* Copyright (c) 2015, NORDUnet A/S
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - 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.
*
* - Neither the name of the NORDUnet nor the names of its contributors may
* be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT
* HOLDER OR CONTRIBUTORS 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.
*/
#include <string.h>
#include <stdint.h>
#include "hal.h"
#include "hal_internal.h"
/*
* Utility to encapsulate the HMAC operations. May need refactoring
* if and when we get clever about reusing HMAC state for speed.
*/
static hal_error_t do_hmac(hal_core_t *core,
const hal_hash_descriptor_t * const d,
const uint8_t * const pw, const size_t pw_len,
const uint8_t * const data, const size_t data_len,
const uint32_t block,
uint8_t * mac, const size_t mac_len)
{
hal_assert(d != NULL && pw != NULL && data != NULL && mac != NULL);
uint8_t sb[d->hmac_state_length];
hal_hmac_state_t *s;
hal_error_t err;
if ((err = hal_hmac_initialize(core, d, &s, sb, sizeof(sb), pw, pw_len)) != HAL_OK)
return err;
if ((err = hal_hmac_update(s, data, data_len)) != HAL_OK)
return err;
if (block > 0) {
uint8_t b[4] = { (block >> 24) & 0xFF, (block >> 16) & 0xFF, (block >> 8) & 0xFF, (block >> 0) & 0xFF };
if ((err = hal_hmac_update(s, b, sizeof(b))) != HAL_OK)
return err;
}
return hal_hmac_finalize(s, mac, mac_len);
}
/*
* Derive a key from a passphrase using the PBKDF2 algorithm.
*/
hal_error_t hal_pbkdf2(hal_core_t *core,
const hal_hash_descriptor_t * const descriptor,
const uint8_t * const password, const size_t password_length,
const uint8_t * const salt, const size_t salt_length,
uint8_t * derived_key, size_t derived_key_length,
unsigned iterations_desired)
{
uint8_t result[HAL_MAX_HASH_DIGEST_LENGTH], mac[HAL_MAX_HASH_DIGEST_LENGTH];
uint8_t statebuf[1024];
unsigned iteration;
hal_error_t err;
uint32_t block;
if (descriptor == NULL || password == NULL || salt == NULL ||
derived_key == NULL || derived_key_length == 0 ||
iterations_desired == 0)
return HAL_ERROR_BAD_ARGUMENTS;
hal_assert(sizeof(statebuf) >= descriptor->hmac_state_length);
hal_assert(sizeof(result) >= descriptor->digest_length);
hal_assert(sizeof(mac) >= descriptor->digest_length);
/* Output length check per RFC 2989 5.2. */
if ((uint64_t) derived_key_length > ((uint64_t) 0xFFFFFFFF) * descriptor->block_length)
return HAL_ERROR_UNSUPPORTED_KEY;
memset(result, 0, sizeof(result));
memset(mac, 0, sizeof(mac));
/*
* We probably should check here to see whether the password is
* longer than the HMAC block size, and, if so, we should hash the
* password here to avoid having recomputing that every time through
* the loops below. There are other optimizations we'd like to
* make, but this one doesn't require being able to save and restore
* the hash state.
*/
/*
* Generate output blocks until we reach the requested length.
*/
for (block = 1; ; block++) {
/*
* Initial HMAC is of the salt concatenated with the block count.
* This seeds the result, and constitutes iteration one.
*/
if ((err = do_hmac(core, descriptor, password, password_length,
salt, salt_length, block, mac, sizeof(mac))) != HAL_OK)
return err;
memcpy(result, mac, descriptor->digest_length);
/*
* Now iterate however many times the caller requested, XORing the
* HMAC back into the result on each iteration.
*/
for (iteration = 2; iteration <= iterations_desired; iteration++) {
if ((err = do_hmac(core, descriptor, password, password_length,
mac, descriptor->digest_length,
0, mac, sizeof(mac))) != HAL_OK)
return err;
for (size_t i = 0; i < descriptor->digest_length; i++)
result[i] ^= mac[i];
}
/*
* Save result block, then exit or loop for another block.
*/
if (derived_key_length > descriptor->digest_length) {
memcpy(derived_key, result, descriptor->digest_length);
derived_key += descriptor->digest_length;
derived_key_length -= descriptor->digest_length;
}
else {
memcpy(derived_key, result, derived_key_length);
return HAL_OK;
}
}
}
/*
* Local variables:
* indent-tabs-mode: nil
* End:
*/
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