Mitigation for APPPROTECT attack?

[jeremyherbert]

Hi,

I’m looking at starting a new design that would be based on the nrf52840, however it seems that the flash readout protection is now fairly broken on this device. Are there any mitigation strategies planned or proposed ? Otherwise I may need to look at using another IC (or the nrf5340, but that isn’t technically ready for production yet).

[Jørgen Holmefjord]

Hi,

The available information can be found in IN133 Informational Notice v1.0. For questions about roadmaps and future plans, please contact your regional sales manager.

If you do not have the contact details, please send me a private message with your location and I will provide you with the information.

Best regards,
Jørgen

[Vincent Belaïche]

Dear Jørgen Holmefjord ,

I have a similar question concerning the AppProtect attack mitigation as described by In 141 v1.1. If I use SDK 17.1.0 for the Application but the booloader is not upgraded and is still based on SDK 15.x.x, will my product benefit from the mitigation. The international notice says « 4. Perform a hard reset to protect the device. The programmed code from step 2 will write APPROTECT.FORCEPROTECT to Force (0x00). », but if the bootloader is based on SDK 15.x.x, the SystemInit of the bootloader will not call nrf52_handle_approtect(), it will be called only when the SystemInit of the App is called, but then you have had some sort of SoftReset when the bootloader starts the App, so you are not directly after a hard reset. Does it matter ?

One more question : does it mean that during the execution of the bootloader the attack mitigation is not done,so there is still some time gap in which the attack would be possible (said otherwise upgrading the bootloader to SDK 17.1.0 would be advisable).

[Jørgen Holmefjord]

but if the bootloader is based on SDK 15.x.x, the SystemInit of the bootloader will not call nrf52_handle_approtect(), it will be called only when the SystemInit of the App is called, but then you have had some sort of SoftReset when the bootloader starts the App, so you are not directly after a hard reset. Does it matter ?

Correct, the full protection will not be enabled until the application code runs, meaning that the bootloader is not protected.

One more question : does it mean that during the execution of the bootloader the attack mitigation is not done,so there is still some time gap in which the attack would be possible (said otherwise upgrading the bootloader to SDK 17.1.0 would be advisable).

Yes, upgrading the bootloader to SDK17.1.0 or the required MDK version is definitely advisable.

[Vincent Belaïche]

Thank you for your reply, it is crystal clear.