Security OTA Sketch

[Anticimex]

@Anduril well, you can always rewrite the personalizer to not use a setup() function.

[Anduril]

I think that's a little beyond my skills :-)

[Anduril]

@Anticimex still the question: is there a way to find out a nodes whitelist serial later?

[Anticimex]

@Anduril that depend on your backend. For software signing the serial is stored in eeprom. For atsha204a it is only readable from the device itself.

[Anduril]

that's sad.
Maybe it would be possible to write a sketch to read out the atsha serial and transmit it via mysensors... I will be looking into this further when in need of whitelisting. Until then I will just leave it as it is and only use signing and maybe encryption.

[Anticimex]

@Anduril I'd prefer not as the serial is also considered a semi-secret to maintain the integrity of the security infrastructure. It should not be thrown around the network unprotected.

[Anduril]

I understand that. Two questions:
what about updating via OTA with whitelisting enabled? Everyone could sniff the new hexfile and read the serial of the whitelisted node, correct?
what about activating encryption? Would that prevent both of these cases? No one could read the hexfile or the send serial without knowing the AES key before.

[Anticimex]

@Anduril if encrypted the data "cannot" be decoded. The serial is not stored in any firmware. The only exception being a personalizer sketch that will personalize for software signing.
For atsha204a based signing, serial is never stored in sketch, only in runtime.

[Anduril]

Just in the rare case I want to use it later (and I have encryption enabled in the whole mysensors network) I could theoretically write a sketch inspired by the personalizer to read the serial and send this as a payload to the gateway without anyone out there able to read.

[Anticimex]

@Anduril Well, its all opensource, so you are free to do whatever you want. Just remember that if you are starting to alter the behaviour and use of the security infrastructure, you could potentially compromise it for yourself and those that use your code.