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flash encryption: Add config option to disable any plaintext reflashes

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Enabled by default when Secure Boot is on, so Flash Encryption protection
is always available in case of a Secure Boot bypass.
This commit is contained in:
Angus Gratton
2019-06-12 11:03:42 +10:00
committed by Angus Gratton
parent cdabee59ef
commit 8df3c666db
5 changed files with 53 additions and 17 deletions
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5
components/bootloader_support/include/esp_flash_encrypt.h
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@@ -102,8 +102,9 @@ 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.
* should be permanently enabled. This should protect against serial
* re-flashing of an unauthorised code in absence of secure boot or if
* secure boot protection is bypassed.
*
* @return
*/

8
components/bootloader_support/src/flash_encrypt.c
View File

@@ -210,6 +210,14 @@ static esp_err_t encrypt_flash_contents(uint32_t flash_crypt_cnt, bool flash_cry
uint32_t new_flash_crypt_cnt = flash_crypt_cnt + (1 << (ffs_inv - 1));
ESP_LOGD(TAG, "FLASH_CRYPT_CNT 0x%x -> 0x%x", flash_crypt_cnt, new_flash_crypt_cnt);
REG_SET_FIELD(EFUSE_BLK0_WDATA0_REG, EFUSE_FLASH_CRYPT_CNT, new_flash_crypt_cnt);
#ifdef CONFIG_FLASH_ENCRYPTION_DISABLE_PLAINTEXT
ESP_LOGI(TAG, "Write protecting FLASH_CRYPT_CNT efuse...");
REG_SET_BIT(EFUSE_BLK0_WDATA0_REG, EFUSE_WR_DIS_FLASH_CRYPT_CNT);
#else
ESP_LOGW(TAG, "Not disabling FLASH_CRYPT_CNT - plaintext flashing is still possible");
#endif
esp_efuse_burn_new_values();
ESP_LOGI(TAG, "Flash encryption completed");