/*
* mkm.c
* -----
* Master Key Memory functions.
*
* Copyright (c) 2016-2019, NORDUnet A/S All rights reserved.
* Copyright: 2020, The Commons Conservancy Cryptech Project
* SPDX-License-Identifier: BSD-3-Clause
*
* 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.
*/
/*
* Code to load the Master key (Key Encryption Key) from either the volatile MKM
* (by asking the FPGA to provide it, using the mkmif) or from the last sector in
* the keystore flash.
*
* Storing the master key in flash is a pretty Bad Idea, but since the Alpha board
* doesn't have a battery mounted (only pin headers for attaching one), it might
* help in non-production use where one doesn't have tamper protection anyways.
*
* For production use on the Alpha, one option is to have the Master Key on paper
* and enter it into volatile RAM after each power on.
*
* In both volatile memory and flash, the data is stored as a 32 bit status to
* know if the memory is initialized or not, followed by 32 bytes (256 bits) of
* Master Key.
*/
#include "hal.h"
#include "hal_internal.h"
#include <string.h>
#define MKM_VOLATILE_STATUS_ADDRESS 0
#define MKM_VOLATILE_SCLK_DIV 0x20
#define MKM_FLASH_STATUS_ADDRESS (KEYSTORE_SECTOR_SIZE * (KEYSTORE_NUM_SECTORS - 1))
/*
* Match uninitialized flash for the "not set" value.
* Leave some bits at 1 for the "set" value to allow
* for adding more values later, if needed.
*/
#define MKM_STATUS_NOT_SET 0xffffffff
#define MKM_STATUS_SET 0x0000ffff
#define MKM_STATUS_ERASED 0x00000000
static hal_error_t hal_mkm_volatile_init(void)
{
static int volatile_init = 0;
if (volatile_init)
return HAL_OK;
hal_error_t err;
uint32_t status;
hal_core_t *core = NULL;
if ((err = hal_core_alloc(MKMIF_NAME, &core, NULL)) != HAL_OK)
return err;
if ((err = hal_mkmif_set_clockspeed(core, MKM_VOLATILE_SCLK_DIV)) != HAL_OK ||
(err = hal_mkmif_init(core)) != HAL_OK ||
(err = hal_mkmif_read_word(core, MKM_VOLATILE_STATUS_ADDRESS, &status)) != HAL_OK)
goto out;
if (status != MKM_STATUS_SET && status != MKM_STATUS_NOT_SET) {
/*
* XXX Something is a bit fishy here. If we just write the status word, it reads back wrong sometimes,
* while if we write the full buf too it is consistently right afterwards.
*/
uint8_t buf[KEK_LENGTH] = {0};
if ((err = hal_mkmif_write(core, MKM_VOLATILE_STATUS_ADDRESS + 4, buf, sizeof(buf))) != HAL_OK ||
(err = hal_mkmif_write_word(core, MKM_VOLATILE_STATUS_ADDRESS, MKM_STATUS_NOT_SET)) != HAL_OK)
goto out;
}
volatile_init = 1;
out:
hal_core_free(core);
return err;
}
hal_error_t hal_mkm_volatile_read(uint8_t *buf, const size_t len)
{
hal_error_t err;
uint32_t status;
hal_core_t *core = NULL;
if (len && len != KEK_LENGTH)
return HAL_ERROR_MASTERKEY_BAD_LENGTH;
if ((err = hal_mkm_volatile_init()) != HAL_OK ||
(err = hal_core_alloc(MKMIF_NAME, &core, NULL)) != HAL_OK)
return err;
if ((err = hal_mkmif_read_word(core, MKM_VOLATILE_STATUS_ADDRESS, &status)) != HAL_OK)
goto out;
if (buf != NULL && len) {
/*
* Don't return the random bytes in the RAM memory in case it isn't initialized.
* Or maybe we should fill the buffer with proper random data in that case... hmm.
*/
if (status != MKM_STATUS_SET)
memset(buf, 0x0, len);
else
err = hal_mkmif_read(core, MKM_VOLATILE_STATUS_ADDRESS + 4, buf, len);
}
out:
hal_core_free(core);
if (err != HAL_OK)
return err;
if (status == MKM_STATUS_SET)
return HAL_OK;
if (status == MKM_STATUS_NOT_SET)
return HAL_ERROR_MASTERKEY_NOT_SET;
return HAL_ERROR_MASTERKEY_FAIL;
}
hal_error_t hal_mkm_volatile_write(const uint8_t * const buf, const size_t len)
{
hal_error_t err;
hal_core_t *core = NULL;
if (len != KEK_LENGTH)
return HAL_ERROR_MASTERKEY_BAD_LENGTH;
if (buf == NULL)
return HAL_ERROR_MASTERKEY_FAIL;
if ((err = hal_mkm_volatile_init()) != HAL_OK ||
(err = hal_core_alloc(MKMIF_NAME, &core, NULL)) != HAL_OK)
return err;
if ((err = hal_mkmif_write(core, MKM_VOLATILE_STATUS_ADDRESS + 4, buf, len)) == HAL_OK)
err = hal_mkmif_write_word(core, MKM_VOLATILE_STATUS_ADDRESS, MKM_STATUS_SET);
hal_core_free(core);
return err;
}
hal_error_t hal_mkm_volatile_erase(const size_t len)
{
uint8_t buf[KEK_LENGTH] = {0};
hal_error_t err;
hal_core_t *core = NULL;
if (len != KEK_LENGTH)
return HAL_ERROR_MASTERKEY_BAD_LENGTH;
if ((err = hal_mkm_volatile_init()) != HAL_OK ||
(err = hal_core_alloc(MKMIF_NAME, &core, NULL)) != HAL_OK)
return err;
if ((err = hal_mkmif_write(NULL, MKM_VOLATILE_STATUS_ADDRESS + 4, buf, sizeof(buf))) == HAL_OK)
err = hal_mkmif_write_word(NULL, MKM_VOLATILE_STATUS_ADDRESS, MKM_STATUS_NOT_SET);
hal_core_free(core);
return err;
}
/*
* hal_mkm_flash_*() functions moved to ks_flash.c, to keep all the code that
* knows intimate details of the keystore flash layout in one place.
*/
hal_error_t hal_mkm_get_kek(uint8_t *kek,
size_t *kek_len,
const size_t kek_max)
{
if (kek == NULL || kek_len == NULL || kek_max < bitsToBytes(128))
return HAL_ERROR_BAD_ARGUMENTS;
const size_t len = ((kek_max < bitsToBytes(192)) ? bitsToBytes(128) :
(kek_max < bitsToBytes(256)) ? bitsToBytes(192) :
bitsToBytes(256));
hal_error_t err = hal_mkm_volatile_read(kek, len);
if (err == HAL_OK) {
*kek_len = len;
return HAL_OK;
}
#if HAL_MKM_FLASH_BACKUP_KLUDGE
/*
* It turns out that, in every case where this function is called,
* we already hold the keystore lock, so attempting to grab it again
* would deadlock. This almost never happens when the volatile MKM
* is set, but there's a race condition that might drop us here if
* hal_mkm_volatile_read() returns HAL_ERROR_CORE_BUSY. Whee!
*/
if (hal_mkm_flash_read_no_lock(kek, len) == HAL_OK) {
*kek_len = len;
return HAL_OK;
}
#endif
/*
* Both keystores returned an error, probably HAL_ERROR_MASTERKEY_NOT_SET.
* I could try to be clever and compare the errors, but really the volatile
* keystore is the important one (you shouldn't store the master key in
* flash), so return that error.
*/
return err;
}
/*
* "Any programmer who fails to comply with the standard naming, formatting,
* or commenting conventions should be shot. If it so happens that it is
* inconvenient to shoot him, then he is to be politely requested to recode
* his program in adherence to the above standard."
* -- Michael Spier, Digital Equipment Corporation
*
* Local variables:
* indent-tabs-mode: nil
* End:
*/
