trezor-firmware/norcow.c

/*
 * This file is part of the TREZOR project, https://trezor.io/
 *
 * Copyright (c) SatoshiLabs
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <string.h>

#include "norcow.h"
#include "flash.h"
#include "common.h"

// NRC2 = 4e524332
#define NORCOW_MAGIC      ((uint32_t)0x3243524e)
// NRCW = 4e524357
#define NORCOW_MAGIC_V0   ((uint32_t)0x5743524e)

#define NORCOW_WORD_SIZE  (sizeof(uint32_t))
#define NORCOW_PREFIX_LEN NORCOW_WORD_SIZE
#define NORCOW_MAGIC_LEN  NORCOW_WORD_SIZE
#define NORCOW_VERSION_LEN NORCOW_WORD_SIZE

// The key value which is used to indicate that the entry is not set.
#define NORCOW_KEY_FREE   (0xFFFF)

// The key value which is used to indicate that the entry has been deleted.
#define NORCOW_KEY_DELETED (0x0000)

// The offset from the beginning of the sector where stored items start.
#define NORCOW_STORAGE_START (NORCOW_HEADER_LEN + NORCOW_MAGIC_LEN + NORCOW_VERSION_LEN)

// Map from sector index to sector number.
static const uint8_t norcow_sectors[NORCOW_SECTOR_COUNT] = NORCOW_SECTORS;

// The index of the active reading sector and writing sector. These should be equal except when storage version upgrade or compaction is in progress.
static uint8_t norcow_active_sector = 0;
static uint8_t norcow_write_sector = 0;

// The norcow version of the reading sector.
static uint32_t norcow_active_version = 0;

// The offset of the first free item in the writing sector.
static uint32_t norcow_free_offset = 0;

/*
 * Returns pointer to sector, starting with offset
 * Fails when there is not enough space for data of given size
 */
static const void *norcow_ptr(uint8_t sector, uint32_t offset, uint32_t size)
{
    ensure(sectrue * (sector <= NORCOW_SECTOR_COUNT), "invalid sector");
    return flash_get_address(norcow_sectors[sector], offset, size);
}

/*
 * Writes data to given sector, starting from offset
 */
static secbool norcow_write(uint8_t sector, uint32_t offset, uint32_t prefix, const uint8_t *data, uint16_t len)
{
    if (sector >= NORCOW_SECTOR_COUNT) {
        return secfalse;
    }

    if (offset + NORCOW_PREFIX_LEN + len > NORCOW_SECTOR_SIZE) {
        return secfalse;
    }

    ensure(flash_unlock_write(), NULL);

    // write prefix
    ensure(flash_write_word(norcow_sectors[sector], offset, prefix), NULL);
    offset += NORCOW_PREFIX_LEN;

    if (data != NULL) {
        // write data
        for (uint16_t i = 0; i < len; i++, offset++) {
            ensure(flash_write_byte(norcow_sectors[sector], offset, data[i]), NULL);
        }
    } else {
        offset += len;
    }

    // pad with zeroes
    for (; offset % NORCOW_WORD_SIZE; offset++) {
        ensure(flash_write_byte(norcow_sectors[sector], offset, 0x00), NULL);
    }

    ensure(flash_lock_write(), NULL);
    return sectrue;
}

/*
 * Erases sector (and sets a magic)
 */
static void erase_sector(uint8_t sector, secbool set_magic)
{
#if NORCOW_HEADER_LEN > 0
    // Backup the sector header.
    uint32_t header_backup[NORCOW_HEADER_LEN/sizeof(uint32_t)];
    const void *sector_start = norcow_ptr(sector, 0, NORCOW_HEADER_LEN);
    memcpy(header_backup, sector_start, sizeof(header_backup));
#endif

    ensure(flash_erase(norcow_sectors[sector]), "erase failed");

#if NORCOW_HEADER_LEN > 0
    // Copy the sector header back.
    ensure(flash_unlock_write(), NULL);
    for (uint32_t i = 0; i < NORCOW_HEADER_LEN/sizeof(uint32_t); ++i) {
        ensure(flash_write_word(norcow_sectors[sector], i*sizeof(uint32_t), header_backup[i]), NULL);
    }
    ensure(flash_lock_write(), NULL);
#endif

    if (sectrue == set_magic) {
        ensure(norcow_write(sector, NORCOW_HEADER_LEN, NORCOW_MAGIC, NULL, 0), "set magic failed");
        ensure(norcow_write(sector, NORCOW_HEADER_LEN + NORCOW_MAGIC_LEN, ~NORCOW_VERSION, NULL, 0), "set version failed");
    }
}

#define ALIGN4(X) (X) = ((X) + 3) & ~3

/*
 * Reads one item starting from offset
 */
static secbool read_item(uint8_t sector, uint32_t offset, uint16_t *key, const void **val, uint16_t *len, uint32_t *pos)
{
    *pos = offset;

    const void *k = norcow_ptr(sector, *pos, 2);
    if (k == NULL) return secfalse;
    *pos += 2;
    memcpy(key, k, sizeof(uint16_t));
    if (*key == NORCOW_KEY_FREE) {
        return secfalse;
    }

    const void *l = norcow_ptr(sector, *pos, 2);
    if (l == NULL) return secfalse;
    *pos += 2;
    memcpy(len, l, sizeof(uint16_t));

    *val = norcow_ptr(sector, *pos, *len);
    if (*val == NULL) return secfalse;
    *pos += *len;
    ALIGN4(*pos);
    return sectrue;
}

/*
 * Writes one item starting from offset
 */
static secbool write_item(uint8_t sector, uint32_t offset, uint16_t key, const void *val, uint16_t len, uint32_t *pos)
{
    uint32_t prefix = ((uint32_t)len << 16) | key;
    *pos = offset + NORCOW_PREFIX_LEN + len;
    ALIGN4(*pos);
    return norcow_write(sector, offset, prefix, val, len);
}

/*
 * Finds the offset from the beginning of the sector where stored items start.
 */
static secbool find_start_offset(uint8_t sector, uint32_t *offset, uint32_t *version)
{
    const uint32_t *magic = norcow_ptr(sector, NORCOW_HEADER_LEN, NORCOW_MAGIC_LEN + NORCOW_VERSION_LEN);
    if (magic == NULL) {
        return secfalse;
    }

    if (*magic == NORCOW_MAGIC) {
        *offset = NORCOW_STORAGE_START;
        *version = ~(magic[1]);
    } else if (*magic == NORCOW_MAGIC_V0) {
        *offset = NORCOW_HEADER_LEN + NORCOW_MAGIC_LEN;
        *version = 0;
    } else {
        return secfalse;
    }

    return sectrue;
}

/*
 * Finds item in given sector
 */
static secbool find_item(uint8_t sector, uint16_t key, const void **val, uint16_t *len)
{
    *val = NULL;
    *len = 0;

    uint32_t offset;
    uint32_t version;
    if (sectrue != find_start_offset(sector, &offset, &version)) {
        return secfalse;
    }

    for (;;) {
        uint16_t k, l;
        const void *v;
        uint32_t pos;
        if (sectrue != read_item(sector, offset, &k, &v, &l, &pos)) {
            break;
        }
        if (key == k) {
            *val = v;
            *len = l;
        }
        offset = pos;
    }
    return sectrue * (*val != NULL);
}

/*
 * Finds first unused offset in given sector
 */
static uint32_t find_free_offset(uint8_t sector)
{
    uint32_t offset;
    uint32_t version;
    if (sectrue != find_start_offset(sector, &offset, &version)) {
        return secfalse;
    }

    for (;;) {
        uint16_t key, len;
        const void *val;
        uint32_t pos;
        if (sectrue != read_item(sector, offset, &key, &val, &len, &pos)) {
            break;
        }
        offset = pos;
    }
    return offset;
}

/*
 * Compacts active sector and sets new active sector
 */
static void compact(void)
{
    uint32_t offsetr;
    uint32_t version;
    if (sectrue != find_start_offset(norcow_active_sector, &offsetr, &version)) {
        return;
    }

    norcow_write_sector = (norcow_active_sector + 1) % NORCOW_SECTOR_COUNT;
    erase_sector(norcow_write_sector, sectrue);
    uint32_t offsetw = NORCOW_STORAGE_START;

    for (;;) {
        // read item
        uint16_t k, l;
        const void *v;
        uint32_t posr;
        secbool r = read_item(norcow_active_sector, offsetr, &k, &v, &l, &posr);
        if (sectrue != r) {
            break;
        }
        offsetr = posr;

        // skip deleted items
        if (k == NORCOW_KEY_DELETED) {
            continue;
        }

        // copy the item
        uint32_t posw;
        ensure(write_item(norcow_write_sector, offsetw, k, v, l, &posw), "compaction write failed");
        offsetw = posw;
    }

    erase_sector(norcow_active_sector, secfalse);
    norcow_active_sector = norcow_write_sector;
    norcow_active_version = NORCOW_VERSION;
    norcow_free_offset = find_free_offset(norcow_write_sector);
}

/*
 * Initializes storage
 */
void norcow_init(uint32_t *norcow_version)
{
    flash_init();
    secbool found = secfalse;
    *norcow_version = 0;
    // detect active sector - starts with magic and has highest version
    for (uint8_t i = 0; i < NORCOW_SECTOR_COUNT; i++) {
        uint32_t offset;
        if (sectrue == find_start_offset(i, &offset, &norcow_active_version) && norcow_active_version >= *norcow_version) {
            found = sectrue;
            norcow_active_sector = i;
            *norcow_version = norcow_active_version;
        }
    }

    // If no active sectors found or version downgrade, then erase.
    if (sectrue != found || *norcow_version > NORCOW_VERSION) {
        norcow_wipe();
        *norcow_version = NORCOW_VERSION;
    } else if (*norcow_version < NORCOW_VERSION) {
        // Prepare write sector for storage upgrade.
        norcow_write_sector = (norcow_active_sector + 1) % NORCOW_SECTOR_COUNT;
        erase_sector(norcow_write_sector, sectrue);
        norcow_free_offset = find_free_offset(norcow_write_sector);
    } else {
        norcow_write_sector = norcow_active_sector;
        norcow_free_offset = find_free_offset(norcow_write_sector);
    }
}

/*
 * Wipe the storage
 */
void norcow_wipe(void)
{
    erase_sector(0, sectrue);
    for (uint8_t i = 1; i < NORCOW_SECTOR_COUNT; i++) {
        erase_sector(i, secfalse);
    }
    norcow_active_sector = 0;
    norcow_active_version = NORCOW_VERSION;
    norcow_write_sector = 0;
    norcow_free_offset = NORCOW_STORAGE_START;
}

/*
 * Looks for the given key, returns status of the operation
 */
secbool norcow_get(uint16_t key, const void **val, uint16_t *len)
{
    return find_item(norcow_active_sector, key, val, len);
}

/*
 * Reads the next entry in the storage starting at offset. Returns secfalse if there is none.
 */
secbool norcow_get_next(uint32_t *offset, uint16_t *key, const void **val, uint16_t *len)
{
    if (*offset == 0) {
        uint32_t version;
        if (sectrue != find_start_offset(norcow_active_sector, offset, &version)) {
            return secfalse;
        }
    }

    for (;;) {
        uint32_t pos = 0;
        secbool ret = read_item(norcow_active_sector, *offset, key, val, len, &pos);
        if (sectrue != ret) {
            break;
        }
        *offset = pos;

        // Skip deleted items.
        if (*key == NORCOW_KEY_DELETED) {
            continue;
        }

        if (norcow_active_version == 0) {
            // Check whether the item is the latest instance.
            uint32_t offsetr = *offset;
            for (;;) {
                uint16_t k;
                uint16_t l;
                const void *v;
                ret = read_item(norcow_active_sector, offsetr, &k, &v, &l, &offsetr);
                if (sectrue != ret) {
                    // There is no newer instance of the item.
                    return sectrue;
                }
                if (*key == k) {
                    // There exists a newer instance of the item.
                    break;
                }
            }
        } else {
            return sectrue;
        }
    }
    return secfalse;
}

/*
 * Sets the given key, returns status of the operation. If NULL is passed
 * as val, then norcow_set allocates a new key of size len. The value should
 * then be written using norcow_update_bytes().
 */
secbool norcow_set(uint16_t key, const void *val, uint16_t len)
{
    secbool found;
    return norcow_set_ex(key, val, len, &found);
}

secbool norcow_set_ex(uint16_t key, const void *val, uint16_t len, secbool *found)
{
    // Key 0xffff is used as a marker to indicate that the entry is not set.
    if (key == NORCOW_KEY_FREE) {
        return secfalse;
    }

    const uint8_t sector_num = norcow_sectors[norcow_write_sector];
    secbool ret = secfalse;
    const void *ptr = NULL;
    uint16_t len_old = 0;
    *found = find_item(norcow_write_sector, key, &ptr, &len_old);

    // Try to update the entry if it already exists.
    uint32_t offset = 0;
    if (sectrue == *found) {
        offset = (const uint8_t*) ptr - (const uint8_t *)norcow_ptr(norcow_write_sector, 0, NORCOW_SECTOR_SIZE);
        if (val != NULL && len_old == len) {
            ret = sectrue;
            ensure(flash_unlock_write(), NULL);
            for (uint16_t i = 0; i < len; i++) {
                if (sectrue != flash_write_byte(sector_num, offset + i, ((const uint8_t*)val)[i])) {
                    ret = secfalse;
                    break;
                }
            }
            ensure(flash_lock_write(), NULL);
        }
    }

    // If the update was not possible then write the entry as a new item.
    if (secfalse == ret) {
        // Delete the old item.
        if (sectrue == *found) {
            ensure(flash_unlock_write(), NULL);

            // Update the prefix to indicate that the old item has been deleted.
            uint32_t prefix = (uint32_t)len_old << 16;
            ensure(flash_write_word(sector_num, offset - NORCOW_PREFIX_LEN, prefix), NULL);

            // Delete the old item data.
            uint32_t end = offset + len_old;
            while (offset < end) {
                ensure(flash_write_word(sector_num, offset, 0x00000000), NULL);
                offset += NORCOW_WORD_SIZE;
            }

            ensure(flash_lock_write(), NULL);
        }
        // Check whether there is enough free space and compact if full.
        if (norcow_free_offset + NORCOW_PREFIX_LEN + len > NORCOW_SECTOR_SIZE) {
            compact();
        }
        // Write new item.
        uint32_t pos;
        ret = write_item(norcow_write_sector, norcow_free_offset, key, val, len, &pos);
        if (sectrue == ret) {
            norcow_free_offset = pos;
        }
    }
    return ret;
}

/*
 * Deletes the given key, returns status of the operation.
 */
secbool norcow_delete(uint16_t key)
{
    // Key 0xffff is used as a marker to indicate that the entry is not set.
    if (key == NORCOW_KEY_FREE) {
        return secfalse;
    }

    const uint8_t sector_num = norcow_sectors[norcow_write_sector];
    const void *ptr = NULL;
    uint16_t len = 0;
    if (sectrue != find_item(norcow_write_sector, key, &ptr, &len)) {
        return secfalse;
    }

    uint32_t offset = (const uint8_t*) ptr - (const uint8_t *)norcow_ptr(norcow_write_sector, 0, NORCOW_SECTOR_SIZE);

    ensure(flash_unlock_write(), NULL);

    // Update the prefix to indicate that the item has been deleted.
    uint32_t prefix = (uint32_t)len << 16;
    ensure(flash_write_word(sector_num, offset - NORCOW_PREFIX_LEN, prefix), NULL);

    // Delete the item data.
    uint32_t end = offset + len;
    while (offset < end) {
        ensure(flash_write_word(sector_num, offset, 0x00000000), NULL);
        offset += NORCOW_WORD_SIZE;
    }

    ensure(flash_lock_write(), NULL);

    return sectrue;
}

/*
 * Update a word in flash at the given pointer.  The pointer must point
 * into the NORCOW area.
 */
secbool norcow_update_word(uint16_t key, uint16_t offset, uint32_t value)
{
    const void *ptr;
    uint16_t len;
    if (sectrue != find_item(norcow_write_sector, key, &ptr, &len)) {
        return secfalse;
    }
    if ((offset & 3) != 0 || offset >= len) {
        return secfalse;
    }
    uint32_t sector_offset = (const uint8_t*) ptr - (const uint8_t *)norcow_ptr(norcow_write_sector, 0, NORCOW_SECTOR_SIZE) + offset;
    ensure(flash_unlock_write(), NULL);
    ensure(flash_write_word(norcow_sectors[norcow_write_sector], sector_offset, value), NULL);
    ensure(flash_lock_write(), NULL);
    return sectrue;
}

/*
 * Update the value of the given key starting at the given offset.
 */
secbool norcow_update_bytes(const uint16_t key, const uint16_t offset, const uint8_t *data, const uint16_t len)
{
    const void *ptr;
    uint16_t allocated_len;
    if (sectrue != find_item(norcow_write_sector, key, &ptr, &allocated_len)) {
        return secfalse;
    }
    if (offset + len > allocated_len) {
        return secfalse;
    }
    uint32_t sector_offset = (const uint8_t*) ptr - (const uint8_t *)norcow_ptr(norcow_write_sector, 0, NORCOW_SECTOR_SIZE) + offset;
    uint8_t sector = norcow_sectors[norcow_write_sector];
    ensure(flash_unlock_write(), NULL);
    for (uint16_t i = 0; i < len; i++, sector_offset++) {
        ensure(flash_write_byte(sector, sector_offset, data[i]), NULL);
    }
    ensure(flash_lock_write(), NULL);
    return sectrue;
}

/*
 * Complete storage version upgrade
 */
secbool norcow_upgrade_finish(void)
{
    erase_sector(norcow_active_sector, secfalse);
    norcow_active_sector = norcow_write_sector;
    norcow_active_version = NORCOW_VERSION;
    return sectrue;
}