5686cbb1d7
When the flash encryption is enabled then we do not need to change the partition table. The partition_example.csv should not have fixed offsets for partitions because we want to move the whole table. The fixed offsets in the table were cleared.
4.8 KiB
Flash Encryption
The example checks if the flash encryption feature is enabled/disabled and if enabled prints the flash encryption mode (DEVELOPMENT / RELEASE) and FLASH_CRYPT_CNT eFuse value.
The example also demonstrates writing and reading encrypted partitions in flash.
How to use example
Hardware Required
Configure the project
idf.py menuconfig
- Enable the flash encryption mode (Development or Release) under Security Features. Default usage mode is Development (recommended during test and development phase).
Note: After enabling flash encryption, the bootloader size increases, which means that the offset of the partition table must be changed to 0x9000 from 0x8000 to prevent the bootloader from overlapping with the partition table. In this example, the default offset of the partition table is 0x9000.
Build and Flash
When building the project and flashing it to the board FOR THE FIRST TIME after enabling flash encryption feature in menuconfig, run following command to program ESP32 and monitor the output:
idf.py -p PORT flash monitor
(To exit the serial monitor, type Ctrl-].)
See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
When reprogramming the device subsequently use following command for encrypted write of new plaintext application:
idf.py -p PORT encrypted-app-flash monitor
Please note above command programs only the app partition. In order to reprogram all partitions (bootloader, partition table and application) in encrypted form use:
idf.py -p PORT encrypted-flash monitor
Example Output
When running the example without enabling flash encryption, the output would be as follows:
Example to check Flash Encryption status
This is ESP32 chip with 2 CPU cores, WiFi/BT/BLE, silicon revision 0, 2MB external flash
FLASH_CRYPT_CNT eFuse value is 0
Flash encryption feature is disabled
Erasing partition "storage" (0x1000 bytes)
Writing data with esp_partition_write:
I (378) example: 0x3ffb4dc0 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
I (378) example: 0x3ffb4dd0 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |................|
Reading with esp_partition_read:
I (388) example: 0x3ffb4da0 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
I (398) example: 0x3ffb4db0 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |................|
Reading with spi_flash_read:
I (408) example: 0x3ffb4da0 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
I (418) example: 0x3ffb4db0 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |................|
After enabling flash encryption in Development mode, the output shows the process of enabling the flash encryption:
I (168) boot: Checking flash encryption...
I (168) flash_encrypt: Generating new flash encryption key...
I (187) flash_encrypt: Read & write protecting new key...
I (187) flash_encrypt: Setting CRYPT_CONFIG efuse to 0xF
W (188) flash_encrypt: Not disabling UART bootloader encryption
I (195) flash_encrypt: Disable UART bootloader decryption...
I (201) flash_encrypt: Disable UART bootloader MMU cache...
I (208) flash_encrypt: Disable JTAG...
I (212) flash_encrypt: Disable ROM BASIC interpreter fallback...
....
....
....
I (13229) flash_encrypt: Flash encryption completed
I (13229) boot: Resetting with flash encryption enabled...
Once the flash encryption is enabled the device will reset itself. At this stage the flash contents are in encrypted form. The output would be similar to:
Example to check Flash Encryption status
This is ESP32 chip with 2 CPU cores, WiFi/BT/BLE, silicon revision 0, 4MB external flash
FLASH_CRYPT_CNT eFuse value is 1
Flash encryption feature is enabled in DEVELOPMENT mode
Erasing partition "storage" (0x1000 bytes)
Writing data with esp_partition_write:
I (451) example: 0x3ffb4dc0 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
I (451) example: 0x3ffb4dd0 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |................|
Reading with esp_partition_read:
I (461) example: 0x3ffb4da0 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
I (471) example: 0x3ffb4db0 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |................|
Reading with spi_flash_read:
I (491) example: 0x3ffb4da0 29 68 2e 13 88 a0 5b 7f cc 6b 39 f9 d7 7b 32 2f |)h....[..k9..{2/|
I (491) example: 0x3ffb4db0 9f e6 55 37 4b 91 b0 83 cd a6 e9 4e cd fa b4 c7 |..U7K......N....|
Troubleshooting
It is also possible to use esptool.py utility to read the eFuse values and check if flash encryption is enabled or not
python $IDF_PATH/components/esptool_py/esptool/espefuse.py --port PORT summary
If FLASH_CRYPT_CNT eFuse value is non-zero flash encryption is enabled