SBSFU warning: Initialization with factory default values

Question

Posted on July 15, 2018 at 09:26Hi,SBSFU gives me the warning 'SECURE ENGINE INITIALIZATION WITH FACTORY DEFAULT VALUES' on every new power-up of the microcontroller. Is this behavior normal after a power-cycle or is anything not configure correctly?= [SBOOT] System Security Check successfully passed. Starting...======================================================================= (C) COPYRIGHT 2017 STMicroelectronics == == Secure Boot and Secure Firmware Update ======================================================================= = [SBOOT] STATE: WARNING: SECURE ENGINE INITIALIZATION WITH FACTORY DEFAULT VALUES!========= End of Execution =========== [SBOOT] System Security Check successfully passed. Starting...======================================================================= (C) COPYRIGHT 2017 STMicroelectronics == == Secure Boot and Secure Firmware Update ======================================================================= = [SBOOT] SECURE ENGINE INITIALIZATION SUCCESSFUL= [SBOOT] Waiting for USBD_STATE_CONFIGURED= [SBOOT] MX_USB_DEVICE_Init end= [SBOOT] STATE: CHECK STATUS ON RESET INFO: A Reboot has been triggered by a Software reset! Consecutive Boot on error counter = 0 INFO: Last execution detected error was:No error. Success.= [SBOOT] STATE: CHECK NEW FIRMWARE TO DOWNLOAD= [SBOOT] STATE: DOWNLOAD NEW USER FIRMWARE File> Transfer> YMODEM> SendMany thanks to ST for providing the SBSFU code. Delivering such great resources for free gives you a big advantage over other competitors.One last thing: I discovered a slight security issue in the post-build process. I use AES-CBC, which needs an initialization vector (IV). The IV is automatically created by the post-build tools and saved in iv.bin, but it is only generated once if the file doesn't exist. For safety reasons, it should be different for every single encryption. You can simply delete it before every build, so it is regenerated with a random number, but it would be better if the post-build tool did this automatically. Besides the convenience, you can easily forget to delete the file and make your firmware file more vulnerable than necessary.Probably the same applies to nonce.bin, but I didn't test that.Best regards,Moritz

Jocelyn RICARD · Accepted Answer

Hello Moritz,I'm sorry for this very long delay for answering. This is related to vacation period.yes this message is normal after a power on reset.The reason is that, after a power on reset, the secure engine lost its working data. These data are stored in RAM and protected by a CRC.So there is nothing to worry about this message.About this IV and nonce issue you raise, I agree this should be changed automatically. This point was already raised but the point here is not to provide a ready made solution but a base example on which you can build your system. Anyway I will ask again to dev team, just to make things cleaner!I hope this answers to your questionsBest regardsJocelyn

Tesla DeLorean · Answer

Can't help you, bumping you off my feed

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