Generate SSL key and csr on device and support installing a certificate via MQTT #15
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This is step 1 towards providing an improved "first boot with SSL" experience.
Struggling with stack size here...
Generating a key requires a reasonable number of multi-kb buffers. If we naively put those on the stack we have to enlarge the stack size for the MQTT task, which permanently denies other tasks use of that memory, even though it's going to be almost always unused in the MQTT stack given key generation is a very rare operation. Allocating these buffers explicitly on the heap means the memory is free for everything else to use the rest of the time.
This allows the server to pass back a signed certificate for the monitor, which will check it is signed by the trusted CA and matches the private key previously generated by a requestCert/regenerateKey command and then install it and reboot. This is fully functional for bootstrapping SSL on a device now, but not yet production ready - need further support for updating config, etc first.
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Can you give this branch a try please? |
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What are the changes? It's a bit tedious to get a diff between what's in this pull request and what's in the branch because of the changed filenames, etc. |
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I'd like to be able to have new devices self-register for secure MQTT without having to generate and transfer keys/certs off the device and then flash them on via a full filesytem update.
This adds the necessary logic to have the device itself generate a new key and associated CSR which it will submit via MQTT, and then await receipt of a signed certificate via a return MQTT message. How and if the server actually signs/generates the certs and sends it back is left up to the user, as its likely to be highly context specific.