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/*
* pbkdf2.c
* --------
* PBKDF2 (RFC 2898) on top of HAL interface to Cryptech hash cores.
*
* Authors: Rob Austein
* Copyright (c) 2015, SUNET
*
* 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 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 OWNER 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 <assert.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include "cryptech.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(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)
{
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(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(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 statebuf[1024]; /* C99 may let us clean this up */
uint32_t block_count;
if (descriptor == NULL || password == NULL || salt == NULL ||
derived_key == NULL || derived_key_length == 0 ||
iterations_desired == 0)
return HAL_ERROR_BAD_ARGUMENTS;
assert(sizeof(statebuf) >= descriptor->hmac_state_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;
/*
* 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_count = 1; ; block_count++) {
uint8_t accumulator[HAL_MAX_HASH_DIGEST_LENGTH], mac[HAL_MAX_HASH_DIGEST_LENGTH];
unsigned iteration;
hal_error_t err;
int i;
/*
* Initialize the accumulator with the HMAC of the salt
* concatenated with the block count.
*/
if ((err = do_hmac(descriptor, password, password_length, salt, salt_length,
block_count, accumulator, sizeof(accumulator))) != HAL_OK)
return err;
/*
* Now iterate however many times the caller requested, XORing the
* result back into the accumulator on each iteration.
* Initializing the accumulator counts as iteration 1, so we start
* with iteration 2.
*/
for (iteration = 2; iteration <= iterations_desired; iteration++) {
if ((err = do_hmac(descriptor, password, password_length,
accumulator, descriptor->digest_length,
0, mac, sizeof(mac))) != HAL_OK)
return err;
for (i = 0; i < descriptor->digest_length; i++)
accumulator[i] ^= mac[i];
}
/*
* Accumulator holds the generated block. Save it, then exit or
* loop for another block.
*/
if (derived_key_length > descriptor->digest_length) {
memcpy(derived_key, accumulator, descriptor->digest_length);
derived_key += descriptor->digest_length;
derived_key_length -= descriptor->digest_length;
}
else {
memcpy(derived_key, accumulator, derived_key_length);
return HAL_OK;
}
}
}
/*
* Local variables:
* indent-tabs-mode: nil
* End:
*/
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