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esp_flash_encrypt.h
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esp_flash_encrypt.h
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// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef __ESP32_FLASH_ENCRYPT_H
#define __ESP32_FLASH_ENCRYPT_H
#include <stdbool.h>
#include "esp_attr.h"
#include "esp_err.h"
#ifndef BOOTLOADER_BUILD
#include "esp_spi_flash.h"
#endif
#include "soc/efuse_reg.h"
/**
* @file esp_partition.h
* @brief Support functions for flash encryption features
*
* Can be compiled as part of app or bootloader code.
*/
/** @brief Is flash encryption currently enabled in hardware?
*
* Flash encryption is enabled if the FLASH_CRYPT_CNT efuse has an odd number of bits set.
*
* @return true if flash encryption is enabled.
*/
static inline /** @cond */ IRAM_ATTR /** @endcond */ bool esp_flash_encryption_enabled(void) {
uint32_t flash_crypt_cnt = REG_GET_FIELD(EFUSE_BLK0_RDATA0_REG, EFUSE_RD_FLASH_CRYPT_CNT);
/* __builtin_parity is in flash, so we calculate parity inline */
bool enabled = false;
while(flash_crypt_cnt) {
if (flash_crypt_cnt & 1) {
enabled = !enabled;
}
flash_crypt_cnt >>= 1;
}
return enabled;
}
/* @brief Update on-device flash encryption
*
* Intended to be called as part of the bootloader process if flash
* encryption is enabled in device menuconfig.
*
* If FLASH_CRYPT_CNT efuse parity is 1 (ie odd number of bits set),
* then return ESP_OK immediately (indicating flash encryption is enabled
* and functional).
*
* If FLASH_CRYPT_CNT efuse parity is 0 (ie even number of bits set),
* assume the flash has just been written with plaintext that needs encrypting.
*
* The following regions of flash are encrypted in place:
*
* - The bootloader image, if a valid plaintext image is found.[*]
* - The partition table, if a valid plaintext table is found.
* - Any app partition that contains a valid plaintext app image.
* - Any other partitions with the "encrypt" flag set. [**]
*
* After the re-encryption process completes, a '1' bit is added to the
* FLASH_CRYPT_CNT value (setting the parity to 1) and the EFUSE is re-burned.
*
* [*] If reflashing bootloader with secure boot enabled, pre-encrypt
* the bootloader before writing it to flash or secure boot will fail.
*
* [**] For this reason, if serial re-flashing a previous flashed
* device with secure boot enabled and using FLASH_CRYPT_CNT to
* trigger re-encryption, you must simultaneously re-flash plaintext
* content to all partitions with the "encrypt" flag set or this
* data will be corrupted (encrypted twice).
*
* @note The post-condition of this function is that all
* partitions that should be encrypted are encrypted.
*
* @note Take care not to power off the device while this function
* is running, or the partition currently being encrypted will be lost.
*
* @note RTC_WDT will reset while encryption operations will be performed (if RTC_WDT is configured).
*
* @return ESP_OK if all operations succeeded, ESP_ERR_INVALID_STATE
* if a fatal error occured during encryption of all partitions.
*/
esp_err_t esp_flash_encrypt_check_and_update(void);
/** @brief Encrypt-in-place a block of flash sectors
*
* @note This function resets RTC_WDT between operations with sectors.
* @param src_addr Source offset in flash. Should be multiple of 4096 bytes.
* @param data_length Length of data to encrypt in bytes. Will be rounded up to next multiple of 4096 bytes.
*
* @return ESP_OK if all operations succeeded, ESP_ERR_FLASH_OP_FAIL
* if SPI flash fails, ESP_ERR_FLASH_OP_TIMEOUT if flash times out.
*/
esp_err_t esp_flash_encrypt_region(uint32_t src_addr, size_t data_length);
/** @brief Write protect FLASH_CRYPT_CNT
*
* Intended to be called as a part of boot process if flash encryption
* is enabled but secure boot is not used. This should protect against
* serial re-flashing of an unauthorised code in absence of secure boot.
*
* @return
*/
void esp_flash_write_protect_crypt_cnt();
#endif