SHA-256 comparison failed: [...] attempting to boot anyway...

[jessebraham]

When the app image header is updated with new flash configuration values, output like the following can be seen in the bootloader messages:

SHA-256 comparison failed:
Calculated: bf6e7aa7738b60d6b15de2bea35979ca40a8a94224f3c78ef00f19a96becf599
Expected: c279089098b4d648c53538bb1dfba7caa16140817d4be0ee4394fe6967e6813d
Attempting to boot anyway...

While the application still executes as expected, we will need to address this. This is not an issue unless you plan to use Secure Boot, which we do not presently support anyways. I have a local branch in-progress but it still needs some work.

[SergioGasquez]

I did some investigations for this issue using an esp-idf example with esptool and espflash, here are my initial findings:
If we use:

esptool.py -p /dev/ttyACM0 -b 460800 --before default_reset --after hard_reset --chip esp32c3  write_flash --flash_mode dio --flash_size 2MB --flash_freq 80m 0x0 build/bootloader/bootloader.bin 0x8000 build/partition_table/partition-table.bin 0x10000 build/blink.bin

espflash monitor

Or the espflash equivalent:

espflash flash -M --port /dev/ttyACM0 -b 460800 --chip esp32c3 --flash-mode dio --flash-size 2mb --flash-freq 80mhz --bootloader build/bootloader/bootloader.bin --partition-table build/partition_table/partition-table.bin build/blink.elf

We don't get the comparison failed message. Note that we are using --flash-mode dio --flash-size 2mb --flash-freq 80mhz in both commands.

From esptool docs:

In espflash, we are not using the same defaults FlashSettings, for example, for C3, we use 40MHz as default flash freq (while esptool default is 80MHz). If you try to use this freq in esptool:

esptool.py -p /dev/ttyACM0 -b 460800 --before default_reset --after hard_reset --chip esp32c3  write_flash --flash_mode dio --flash_size 2MB --flash_freq 40m 0x0 build/bootloader/bootloader.bin 0x8000 build/partition_table/partition-table.bin 0x10000 build/blink.bin

We get the following warning:

Warning: Image file at 0x0 is protected with a hash checksum, so not changing the flash frequency setting. Use the --flash_frequency=keep option instead of --flash_frequency=40m in order to remove this warning, or use the --dont-append-digest option for the elf2image command in order to generate an image file without a hash checksum

Possible workarounds:

• Print a warning to the user when he is not using the defaults FlashSettings. Possibly also update default values to avoid the issue if we dont modify any FlashSettings param.
• Create a --dont-append-digest option for save-image arg and print a similar warning as esptool.

We can do one or both workarounds, any input or suggestions on how to proceed @esp-rs/espressif ?

[Vollbrecht]

related info maybe -> general description from esp-idf

in esp-idf-sys we provide a macro to override the app_description via a weak link into the app binary here, but on default its filled by the esp-idf build system

[bjoernQ]

I think I have something .... will create a PR soonish