If BLK2 is empty then it's OK to continue with a warning (otherwise it may spook users into thinking
something this is wrong, but this is the expected workflow.)
If BLK2 is not empty and doesn't match then we need to fail because it won't be possible to
trust the signature.
In commit 02d2903e39, mbedtls was
updated to release v2.16.5, where it was made mandatory to initialize
mbedtls_ctr_drbg_context before using same. It was fixed in wpa supplicant
but missed out in secure boot v2 verification code. This commit
fixes that.
Goal is that multiple faults would be required to bypass a boot-time signature check.
- Also strengthens some address range checks for safe app memory addresses
- Change pre-enable logic to also check the bootloader signature before enabling SBV2 on ESP32
Add some additional checks for invalid sections:
- Sections only partially in DRAM or IRAM are invalid
- If a section is in D/IRAM, allow the possibility only some is in D/IRAM
- Only pass sections that are entirely in the same type of RTC memory region
and all ECDSA to be disabled if secure boot is not enabled
Previously if ECDSA disabled in config then secure_boot_signatures.c would
fail to build (whether or not secure boot was enabled).
To avoid breaking apps that might be using the signature scheme with custom OTA
without enabling secure boot signatures in config, this change just disables
this functionality if unavailable in mbedTLS config.
Possible fix for root cause of https://github.com/espressif/esp-idf/pull/3703
Angus Gratton