bool esp32_fs_crypt_init(void) {
uint8_t tmp[32];
uint32_t addr = 0;
for (addr = 0; addr < spi_flash_get_chip_size(); addr += 32) {
mgos_wdt_feed();
if (spi_flash_read(addr, tmp, sizeof(tmp)) != ESP_OK) {
LOG(LL_ERROR, ("SPI read error at 0x%x", addr));
return false;
}
int j;
for (j = 0; j < sizeof(tmp); j++) {
if (tmp[j] != 0xff) break;
}
if (j < sizeof(tmp)) continue;
/* Found a suitably empty location, now decrypt it. */
if (spi_flash_read_encrypted(addr, tmp, sizeof(tmp)) != ESP_OK) {
LOG(LL_ERROR, ("SPI encrypted read error at 0x%x", addr));
return false;
}
/* Now in tmp we have 32 x 0xff processed with the flash encryption key. */
mbedtls_aes_init(&s_aes_ctx_enc);
mbedtls_aes_setkey_enc(&s_aes_ctx_enc, tmp, 256);
mbedtls_aes_init(&s_aes_ctx_dec);
mbedtls_aes_setkey_dec(&s_aes_ctx_dec, tmp, 256);
LOG(LL_INFO, ("FS encryption key set up, seed @ 0x%x", addr));
return true;
}
LOG(LL_ERROR, ("Could not a suitable seed area for FS encryption"));
return false;
}
esp_err_t IRAM_ATTR spi_flash_write_encrypted(size_t dest_addr, const void *src, size_t size)
{
CHECK_WRITE_ADDRESS(dest_addr, size);
const uint8_t *ssrc = (const uint8_t *)src;
if ((dest_addr % 16) != 0) {
return ESP_ERR_INVALID_ARG;
}
if ((size % 16) != 0) {
return ESP_ERR_INVALID_SIZE;
}
COUNTER_START();
esp_rom_spiflash_result_t rc;
rc = spi_flash_unlock();
if (rc == ESP_ROM_SPIFLASH_RESULT_OK) {
/* esp_rom_spiflash_write_encrypted encrypts data in RAM as it writes,
so copy to a temporary buffer - 32 bytes at a time.
Each call to esp_rom_spiflash_write_encrypted takes a 32 byte "row" of
data to encrypt, and each row is two 16 byte AES blocks
that share a key (as derived from flash address).
*/
uint8_t encrypt_buf[32] __attribute__((aligned(4)));
uint32_t row_size;
for (size_t i = 0; i < size; i += row_size) {
uint32_t row_addr = dest_addr + i;
if (i == 0 && (row_addr % 32) != 0) {
/* writing to second block of a 32 byte row */
row_size = 16;
row_addr -= 16;
/* copy to second block in buffer */
memcpy(encrypt_buf + 16, ssrc + i, 16);
/* decrypt the first block from flash, will reencrypt to same bytes */
spi_flash_read_encrypted(row_addr, encrypt_buf, 16);
} else if (size - i == 16) {
/* 16 bytes left, is first block of a 32 byte row */
row_size = 16;
/* copy to first block in buffer */
memcpy(encrypt_buf, ssrc + i, 16);
/* decrypt the second block from flash, will reencrypt to same bytes */
spi_flash_read_encrypted(row_addr + 16, encrypt_buf + 16, 16);
} else {
/* Writing a full 32 byte row (2 blocks) */
row_size = 32;
memcpy(encrypt_buf, ssrc + i, 32);
}
spi_flash_guard_start();
rc = esp_rom_spiflash_write_encrypted(row_addr, (uint32_t *)encrypt_buf, 32);
spi_flash_guard_end();
if (rc != ESP_ROM_SPIFLASH_RESULT_OK) {
break;
}
}
bzero(encrypt_buf, sizeof(encrypt_buf));
}
COUNTER_ADD_BYTES(write, size);
COUNTER_STOP(write);
spi_flash_guard_op_lock();
spi_flash_mark_modified_region(dest_addr, size);
spi_flash_guard_op_unlock();
return spi_flash_translate_rc(rc);
}