BMC Image Signing Proposal

[Lei YU]

I'd like to bring this topic again.

As I know image signing feature is completed for both BMC and PNOR:
https://github.com/openbmc/phosphor-bmc-code-mgmt
https://github.com/openbmc/openpower-pnor-code-mgmt

However, the above repos are only for systems with UBI-FS feature.
Most of machines are still using the "legacy" obmc flash layout, and thus
they do not have image singing feature.

So I would like to ask for ideas about how to support image signing feature
for machines with "legacy" flash layout?
1. Should we use UBI-FS for machines that requires image signing feature?
2. Or should we implement image signing feature on "legacy" flash layout as
well?

Thanks!