Signed Firmware for Arduino OTA / X.509 / RFC3161 -- working code

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As we all know - the Arduino OTA updating process is not very secure - with the key (or an MD5 which you can use as a key) hardcoded in the firmware and on the ESP32.

We needed something a bit better over here.

So not sure how useful this is to folks - but on the principle of share early and often; you can find it at:

and on

a fully functional secure/signed ArduinoOTA (also for SD cards and webintefaces) public/private key-pair based security for the firmware updates. This version leaves is ESP32 specific (the ESP8662 version is heavy for that sort of flash sizes).

It (should) work(s) for both a hobby setup (local, single key, self-signed, no governance/administrative info) and for a normal enterprise style setup, with backup keys, master keys, delegation that different for production and test/developer firmware (and all that X509, and what not net you) and so on.

We have a variant that does S/MIME - but settled for now on this -as https://tools.ietf.org/html/rfc8576, https://hal.inria.fr/hal-02351794/file/HAL-version.pdf and so on make a solid case for needing a timestamp (while keeping it simple). And with Redwax Server – Timestamp Demo/Interop it is as trivial as 'running a webserver' to integrate this into a CI / CD system.

Any and all feedback welcome !

Dw.

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I think it would be better I you would create a new standalone OTA library over Updater library for esp32.

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So Updater is also used by the Flash update and the HTTP Updater/upload via the web option.

This code/signing also works with these methods.

I.e. the same file can be distributed over SD card or as a HTTP upload and have the signature checked as the process. So the distribution process can be 'insecure'.

So that was why it was done this way.

But happy to change of course !