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Diffstat (limited to 'ks_token.c')
| -rw-r--r-- | ks_token.c | 665 |
1 files changed, 665 insertions, 0 deletions
diff --git a/ks_token.c b/ks_token.c new file mode 100644 index 0000000..1676bc0 --- /dev/null +++ b/ks_token.c @@ -0,0 +1,665 @@ +/* + * ks_token.c + * ---------- + * Keystore implementation in flash memory. + * + * Authors: Rob Austein, Fredrik Thulin + * Copyright (c) 2015-2017, 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. + */ + +/* + * This keystore driver operates over bare flash, versus over a flash file + * system or flash translation layer. The block size is large enough to + * hold an AES-keywrapped 4096-bit RSA key. Any remaining space in the key + * block may be used to store attributes (opaque TLV blobs). If the + * attributes overflow the key block, additional blocks may be added, but + * no attribute may exceed the block size. + */ + +#include <stddef.h> +#include <string.h> +#include <assert.h> + +#include "hal.h" +#include "hal_internal.h" +#include "ks.h" + +#include "last_gasp_pin_internal.h" + +#define HAL_OK CMSIS_HAL_OK +#include "stm-keystore.h" +#undef HAL_OK + +#ifndef KS_TOKEN_CACHE_SIZE +#define KS_TOKEN_CACHE_SIZE 4 +#endif + +#if HAL_KS_BLOCK_SIZE % KEYSTORE_SUBSECTOR_SIZE != 0 +#error Keystore block size is not a multiple of flash subsector size +#endif + +#define NUM_FLASH_BLOCKS ((KEYSTORE_NUM_SUBSECTORS * KEYSTORE_SUBSECTOR_SIZE) / HAL_KS_BLOCK_SIZE) +#define SUBSECTORS_PER_BLOCK (HAL_KS_BLOCK_SIZE / KEYSTORE_SUBSECTOR_SIZE) + +/* + * Keystore database. + */ + +typedef struct { + hal_ks_t ks; /* Must be first (C "subclassing") */ + hal_ks_pin_t wheel_pin; + hal_ks_pin_t so_pin; + hal_ks_pin_t user_pin; +} ks_token_db_t; + +/* + * This is a bit silly, but it's safe enough, and it lets us avoid a + * nasty mess of forward references. + */ + +#define db ((ks_token_db_t * const) hal_ks_token) + +/* + * Calculate offset of the block in the flash address space. + */ + +static inline uint32_t ks_token_offset(const unsigned blockno) +{ + return blockno * HAL_KS_BLOCK_SIZE; +} + +/* + * Read a flash block. + * + * Flash read on the Alpha is slow enough that it pays to check the + * first page before reading the rest of the block. + */ + +static hal_error_t ks_token_read(hal_ks_t *ks, const unsigned blockno, hal_ks_block_t *block) +{ + if (ks != hal_ks_token || block == NULL || blockno >= NUM_FLASH_BLOCKS || sizeof(*block) != HAL_KS_BLOCK_SIZE) + return HAL_ERROR_IMPOSSIBLE; + + if (keystore_read_data(ks_token_offset(blockno), + block->bytes, + KEYSTORE_PAGE_SIZE) != CMSIS_HAL_OK) + return HAL_ERROR_KEYSTORE_ACCESS; + + switch (hal_ks_block_get_type(block)) { + case HAL_KS_BLOCK_TYPE_ERASED: + case HAL_KS_BLOCK_TYPE_ZEROED: + return HAL_OK; + case HAL_KS_BLOCK_TYPE_KEY: + case HAL_KS_BLOCK_TYPE_PIN: + break; + default: + return HAL_ERROR_KEYSTORE_BAD_BLOCK_TYPE; + } + + switch (hal_ks_block_get_status(block)) { + case HAL_KS_BLOCK_STATUS_LIVE: + case HAL_KS_BLOCK_STATUS_TOMBSTONE: + break; + default: + return HAL_ERROR_KEYSTORE_BAD_BLOCK_TYPE; + } + + if (keystore_read_data(ks_token_offset(blockno) + KEYSTORE_PAGE_SIZE, + block->bytes + KEYSTORE_PAGE_SIZE, + sizeof(*block) - KEYSTORE_PAGE_SIZE) != CMSIS_HAL_OK) + return HAL_ERROR_KEYSTORE_ACCESS; + + if (hal_ks_block_calculate_crc(block) != block->header.crc) + return HAL_ERROR_KEYSTORE_BAD_CRC; + + return HAL_OK; +} + +/* + * Convert a live block into a tombstone. Caller is responsible for + * making sure that the block being converted is valid; since we don't + * need to update the CRC for this, we just modify the first page. + */ + +static hal_error_t ks_token_deprecate(hal_ks_t *ks, const unsigned blockno) +{ + if (ks != hal_ks_token || blockno >= NUM_FLASH_BLOCKS) + return HAL_ERROR_IMPOSSIBLE; + + uint8_t page[KEYSTORE_PAGE_SIZE]; + hal_ks_block_header_t *header = (void *) page; + uint32_t offset = ks_token_offset(blockno); + + if (keystore_read_data(offset, page, sizeof(page)) != CMSIS_HAL_OK) + return HAL_ERROR_KEYSTORE_ACCESS; + + header->block_status = HAL_KS_BLOCK_STATUS_TOMBSTONE; + + if (keystore_write_data(offset, page, sizeof(page)) != CMSIS_HAL_OK) + return HAL_ERROR_KEYSTORE_ACCESS; + + return HAL_OK; +} + +/* + * Zero (not erase) a flash block. Just need to zero the first page. + */ + +static hal_error_t ks_token_zero(hal_ks_t *ks, const unsigned blockno) +{ + if (ks != hal_ks_token || blockno >= NUM_FLASH_BLOCKS) + return HAL_ERROR_IMPOSSIBLE; + + uint8_t page[KEYSTORE_PAGE_SIZE] = {0}; + + if (keystore_write_data(ks_token_offset(blockno), page, sizeof(page)) != CMSIS_HAL_OK) + return HAL_ERROR_KEYSTORE_ACCESS; + + return HAL_OK; +} + +/* + * Erase a flash block. Also see ks_token_erase_maybe(), below. + */ + +static hal_error_t ks_token_erase(hal_ks_t *ks, const unsigned blockno) +{ + if (ks != hal_ks_token || blockno >= NUM_FLASH_BLOCKS) + return HAL_ERROR_IMPOSSIBLE; + + unsigned subsector = blockno * SUBSECTORS_PER_BLOCK; + const unsigned end = (blockno + 1) * SUBSECTORS_PER_BLOCK; + + do { + if (keystore_erase_subsector(subsector) != CMSIS_HAL_OK) + return HAL_ERROR_KEYSTORE_ACCESS; + } while (++subsector < end); + + return HAL_OK; +} + +/* + * Erase a flash block if it hasn't already been erased. + * May not be necessary, trying to avoid unnecessary wear. + * + * Unclear whether there's any sane reason why this needs to be + * constant time, given how slow erasure is. But side channel attacks + * can be tricky things, and it's theoretically possible that we could + * leak information about, eg, key length, so we do constant time. + */ + +static hal_error_t ks_token_erase_maybe(hal_ks_t *ks, const unsigned blockno) +{ + if (ks != hal_ks_token || blockno >= NUM_FLASH_BLOCKS) + return HAL_ERROR_IMPOSSIBLE; + + uint8_t mask = 0xFF; + + for (uint32_t a = ks_token_offset(blockno); a < ks_token_offset(blockno + 1); a += KEYSTORE_PAGE_SIZE) { + uint8_t page[KEYSTORE_PAGE_SIZE]; + if (keystore_read_data(a, page, sizeof(page)) != CMSIS_HAL_OK) + return HAL_ERROR_KEYSTORE_ACCESS; + for (int i = 0; i < KEYSTORE_PAGE_SIZE; i++) + mask &= page[i]; + } + + return mask == 0xFF ? HAL_OK : ks_token_erase(ks, blockno); +} + +/* + * Write a flash block, calculating CRC when appropriate. + */ + +static hal_error_t ks_token_write(hal_ks_t *ks, const unsigned blockno, hal_ks_block_t *block) +{ + if (ks != hal_ks_token || block == NULL || blockno >= NUM_FLASH_BLOCKS || sizeof(*block) != HAL_KS_BLOCK_SIZE) + return HAL_ERROR_IMPOSSIBLE; + + hal_error_t err = ks_token_erase_maybe(ks, blockno); + + if (err != HAL_OK) + return err; + + switch (hal_ks_block_get_type(block)) { + case HAL_KS_BLOCK_TYPE_KEY: + case HAL_KS_BLOCK_TYPE_PIN: + block->header.crc = hal_ks_block_calculate_crc(block); + break; + default: + break; + } + + if (keystore_write_data(ks_token_offset(blockno), block->bytes, sizeof(*block)) != CMSIS_HAL_OK) + return HAL_ERROR_KEYSTORE_ACCESS; + + return HAL_OK; +} + +/* + * The token keystore doesn't implement per-session objects, so these are no-ops. + */ + +static hal_error_t ks_token_set_owner(hal_ks_t *ks, + const unsigned blockno, + const hal_client_handle_t client, + const hal_session_handle_t session) +{ + return HAL_OK; +} + +static hal_error_t ks_token_test_owner(hal_ks_t *ks, + const unsigned blockno, + const hal_client_handle_t client, + const hal_session_handle_t session) +{ + return HAL_OK; +} + +static hal_error_t ks_token_copy_owner(hal_ks_t *ks, + const unsigned source, + const unsigned target) +{ + return HAL_OK; +} + +static hal_error_t ks_token_logout(hal_ks_t *ks, + hal_client_handle_t client) +{ + return HAL_OK; +} + +/* + * Forward reference. + */ + +static hal_error_t fetch_pin_block(unsigned *b, hal_ks_block_t **block); + +/* + * Initialize keystore. + */ + +static hal_error_t ks_token_init(hal_ks_t *ks, const int alloc) +{ + if (ks != hal_ks_token) + return HAL_ERROR_IMPOSSIBLE; + + hal_ks_block_t *block = NULL; + hal_error_t err = HAL_OK; + + if (alloc && (err = hal_ks_alloc_common(ks, NUM_FLASH_BLOCKS, KS_TOKEN_CACHE_SIZE, NULL, 0)) != HAL_OK) + return err; + + if ((err = hal_ks_init_common(ks)) != HAL_OK) + return err; + + /* + * Fetch or create the PIN block. + */ + + memset(&db->wheel_pin, 0, sizeof(db->wheel_pin)); + memset(&db->so_pin, 0, sizeof(db->so_pin)); + memset(&db->user_pin, 0, sizeof(db->user_pin)); + + err = fetch_pin_block(NULL, &block); + + if (err == HAL_OK) { + db->wheel_pin = block->pin.wheel_pin; + db->so_pin = block->pin.so_pin; + db->user_pin = block->pin.user_pin; + } + + else if (err == HAL_ERROR_KEY_NOT_FOUND) { + /* + * We found no PIN block, so create one, with the user and so PINs + * cleared and the wheel PIN set to the last-gasp value. The + * last-gasp WHEEL PIN is a terrible answer, but we need some kind + * of bootstrapping mechanism when all else fails. If you have a + * better suggestion, we'd love to hear it. + */ + + unsigned b; + + if ((block = hal_ks_cache_pick_lru(ks)) == NULL) + return HAL_ERROR_IMPOSSIBLE; + + memset(block, 0xFF, sizeof(*block)); + + block->header.block_type = HAL_KS_BLOCK_TYPE_PIN; + block->header.block_status = HAL_KS_BLOCK_STATUS_LIVE; + + block->pin.wheel_pin = db->wheel_pin = hal_last_gasp_pin; + block->pin.so_pin = db->so_pin; + block->pin.user_pin = db->user_pin; + + if ((err = hal_ks_index_add(ks, &hal_ks_pin_uuid, &b, NULL)) != HAL_OK) + return err; + + hal_ks_cache_mark_used(ks, block, b); + + err = ks_token_write(ks, b, block); + + hal_ks_cache_release(ks, block); + } + + return err; +} + +/* + * Dispatch vector and keystore definition, now that we've defined all + * the driver functions. + */ + +static const hal_ks_driver_t ks_token_driver = { + .init = ks_token_init, + .read = ks_token_read, + .write = ks_token_write, + .deprecate = ks_token_deprecate, + .zero = ks_token_zero, + .erase = ks_token_erase, + .erase_maybe = ks_token_erase_maybe, + .set_owner = ks_token_set_owner, + .test_owner = ks_token_test_owner, + .copy_owner = ks_token_copy_owner, + .logout = ks_token_logout +}; + +static ks_token_db_t _db = { .ks.driver = &ks_token_driver }; + +hal_ks_t * const hal_ks_token = &_db.ks; + +/* + * The remaining functions aren't really part of the keystore API per se, + * but they all involve non-key data which we keep in the keystore + * because it's the flash we've got. + */ + +/* + * Special bonus init routine used only by the bootloader, so that it + * can read PINs set by the main firmware. Yes, this is a kludge. We + * could of course call the real ks_init() routine instead, but it's + * slow, and we don't want to allow anything that would modify the + * flash here, so having a special entry point for this kludge is + * simplest, overall. Sigh. + */ + +void hal_ks_init_read_only_pins_only(void) +{ + unsigned b, best_seen = NUM_FLASH_BLOCKS; + hal_ks_block_t block[1]; + + hal_ks_lock(); + + for (b = 0; b < NUM_FLASH_BLOCKS; b++) { + if (hal_ks_block_read(hal_ks_token, b, block) != HAL_OK || + hal_ks_block_get_type(block) != HAL_KS_BLOCK_TYPE_PIN) + continue; + best_seen = b; + if (hal_ks_block_get_status(block) == HAL_KS_BLOCK_STATUS_LIVE) + break; + } + + if (b != best_seen && best_seen != NUM_FLASH_BLOCKS && + hal_ks_block_read(hal_ks_token, best_seen, block) != HAL_OK) + best_seen = NUM_FLASH_BLOCKS; + + if (best_seen == NUM_FLASH_BLOCKS) { + memset(block, 0xFF, sizeof(*block)); + block->pin.wheel_pin = hal_last_gasp_pin; + } + + db->wheel_pin = block->pin.wheel_pin; + db->so_pin = block->pin.so_pin; + db->user_pin = block->pin.user_pin; + + hal_ks_unlock(); +} + +/* + * Fetch PIN. This is always cached, so just returned cached value. + */ + +hal_error_t hal_get_pin(const hal_user_t user, + const hal_ks_pin_t **pin) +{ + if (pin == NULL) + return HAL_ERROR_BAD_ARGUMENTS; + + hal_error_t err = HAL_OK; + + hal_ks_lock(); + + switch (user) { + case HAL_USER_WHEEL: *pin = &db->wheel_pin; break; + case HAL_USER_SO: *pin = &db->so_pin; break; + case HAL_USER_NORMAL: *pin = &db->user_pin; break; + default: err = HAL_ERROR_BAD_ARGUMENTS; + } + + hal_ks_unlock(); + + return err; +} + +/* + * Fetch PIN block. hint = 0 because we know that the all-zeros UUID + * should always sort to first slot in the index. + */ + +static hal_error_t fetch_pin_block(unsigned *b, hal_ks_block_t **block) +{ + if (block == NULL) + return HAL_ERROR_IMPOSSIBLE; + + hal_error_t err; + int hint = 0; + unsigned b_; + + if (b == NULL) + b = &b_; + + if ((err = hal_ks_index_find(hal_ks_token, &hal_ks_pin_uuid, b, &hint)) != HAL_OK || + (err = hal_ks_block_read_cached(hal_ks_token, *b, block)) != HAL_OK) + return err; + + hal_ks_cache_mark_used(hal_ks_token, *block, *b); + + if (hal_ks_block_get_type(*block) != HAL_KS_BLOCK_TYPE_PIN) + return HAL_ERROR_IMPOSSIBLE; + + return HAL_OK; +} + +/* + * Update the PIN block. This block should always be present, but we + * have to do the zombie jamboree to make sure we write the new PIN + * block before destroying the old one. hint = 0 because we know that + * the all-zeros UUID should always sort to first slot in the index. + */ + +static hal_error_t update_pin_block(const unsigned b, + hal_ks_block_t *block, + const hal_ks_pin_block_t * const new_data) +{ + if (block == NULL || new_data == NULL || hal_ks_block_get_type(block) != HAL_KS_BLOCK_TYPE_PIN) + return HAL_ERROR_IMPOSSIBLE; + + int hint = 0; + + block->pin = *new_data; + + return hal_ks_block_update(hal_ks_token, b, block, &hal_ks_pin_uuid, &hint); +} + +/* + * Change a PIN. + */ + +hal_error_t hal_set_pin(const hal_user_t user, + const hal_ks_pin_t * const pin) +{ + if (pin == NULL) + return HAL_ERROR_BAD_ARGUMENTS; + + hal_ks_block_t *block; + hal_error_t err; + unsigned b; + + hal_ks_lock(); + + if ((err = fetch_pin_block(&b, &block)) != HAL_OK) + goto done; + + hal_ks_pin_block_t new_data = block->pin; + hal_ks_pin_t *dp, *bp; + + switch (user) { + case HAL_USER_WHEEL: bp = &new_data.wheel_pin; dp = &db->wheel_pin; break; + case HAL_USER_SO: bp = &new_data.so_pin; dp = &db->so_pin; break; + case HAL_USER_NORMAL: bp = &new_data.user_pin; dp = &db->user_pin; break; + default: err = HAL_ERROR_BAD_ARGUMENTS; goto done; + } + + const hal_ks_pin_t old_pin = *dp; + *dp = *bp = *pin; + + if ((err = update_pin_block(b, block, &new_data)) != HAL_OK) + *dp = old_pin; + + done: + hal_ks_unlock(); + return err; +} + +#if HAL_MKM_FLASH_BACKUP_KLUDGE + +/* + * Horrible insecure kludge in lieu of a battery for the MKM. + * + * API here is a little strange: all calls pass a length parameter, + * but any length other than the compiled in constant just returns an + * immediate error, there's no notion of buffer max length vs buffer + * used length, querying for the size of buffer really needed, or + * anything like that. + * + * We might want to rewrite this some day, if we don't replace it with + * a battery first. For now we just preserve the API as we found it + * while re-implementing it on top of the new keystore. + */ + +hal_error_t hal_mkm_flash_read_no_lock(uint8_t *buf, const size_t len) +{ + if (buf != NULL && len != KEK_LENGTH) + return HAL_ERROR_MASTERKEY_BAD_LENGTH; + + hal_ks_block_t *block; + hal_error_t err; + unsigned b; + + if ((err = fetch_pin_block(&b, &block)) != HAL_OK) + return err; + + if (block->pin.kek_set != FLASH_KEK_SET) + return HAL_ERROR_MASTERKEY_NOT_SET; + + if (buf != NULL) + memcpy(buf, block->pin.kek, len); + + return HAL_OK; +} + +hal_error_t hal_mkm_flash_read(uint8_t *buf, const size_t len) +{ + hal_ks_lock(); + const hal_error_t err = hal_mkm_flash_read_no_lock(buf, len); + hal_ks_unlock(); + return err; +} + +hal_error_t hal_mkm_flash_write(const uint8_t * const buf, const size_t len) +{ + if (buf == NULL) + return HAL_ERROR_BAD_ARGUMENTS; + + if (len != KEK_LENGTH) + return HAL_ERROR_MASTERKEY_BAD_LENGTH; + + hal_ks_block_t *block; + hal_error_t err; + unsigned b; + + hal_ks_lock(); + + if ((err = fetch_pin_block(&b, &block)) != HAL_OK) + goto done; + + hal_ks_pin_block_t new_data = block->pin; + + new_data.kek_set = FLASH_KEK_SET; + memcpy(new_data.kek, buf, len); + + err = update_pin_block(b, block, &new_data); + + done: + hal_ks_unlock(); + return err; +} + +hal_error_t hal_mkm_flash_erase(const size_t len) +{ + if (len != KEK_LENGTH) + return HAL_ERROR_MASTERKEY_BAD_LENGTH; + + hal_ks_block_t *block; + hal_error_t err; + unsigned b; + + hal_ks_lock(); + + if ((err = fetch_pin_block(&b, &block)) != HAL_OK) + goto done; + + hal_ks_pin_block_t new_data = block->pin; + + new_data.kek_set = FLASH_KEK_NOT_SET; + memset(new_data.kek, 0, len); + + err = update_pin_block(b, block, &new_data); + + done: + hal_ks_unlock(); + return err; +} + +#endif /* HAL_MKM_FLASH_BACKUP_KLUDGE */ + +/* + * Local variables: + * indent-tabs-mode: nil + * End: + */ |