Signature Authentication for Nerves Firmware Upload

It looks like this would require in-sync time clocks on the host machine and target. I’m developing several systems that do not rely on NTP being available on the target machine.

I could see this being very useful for systems that do require NTP however.

It might be interesting to go a PKI route for encrypting/decrypting the firmware. Which wouldn’t require the systems to be in sync.

Also the nerves team is working on a solution for this that would use a PKI system to mange signing at the Fwup level. Initial pass at using fwup's signing process. by ConnorRigby · Pull Request #8 · nerves-project-attic/nerves_firmware · GitHub

Anything beyond the pure signature verification is controlled by the service being protected. The purpose of pre_verification callback implementation is to hand off that responsibility to the actual implementation.

The implementation in the fork is calling a convenience function check_expiration. This function performs expiration check only when expiration time is included the request (X-Amz-Expires). If expiration is not included in the signed request, the request doesn’t expire.

You can replace that check_expiration call with something of your own. You can even remove it and not worry about the signing timestamp/expiration.

In fact, the actual callback name is pre_verification. What goes on in that callback is upto the implementaion.

Hope that clarifies.