- adds API for retrieving & setting the ephemeral key. This is
a key that is erased by a power-on reset, but is preserved between
deep-sleep sleep/wake cycles. It is intended for securing a lock
PIN, and can be up to 192 bits long.
- adds API for checking the warm boot flags, which are also stored
in the backup registers.
The keystore is a sensitive server, and the one-way counters
have security-critical propoerties. So instead of revealing a
generic one-way counter API to the world, specific, limited
requests to do things are going to be created for the keystore.
In this case, the bootwait flag would be convenient to be able
to set from userspace. The motivation for this requirement is
actually continuous integration - a normal human could just
hold down a button while turning on power, but in CI, I don't
have a robotic thumb (or an alternative electrical signal) to
simulate the nerve-pinch on boot.
Previously I was "cheating" and simulating this by nuking the
loader, which effectively forces a bootwait.
However, in production, this is *not possible* because the JTAG
port is sealed off. Thus, this may be the first of a series
of small PRs to incorporate CI tooling that clears up tech
debt like nuking the loader to get into boot wait.
have to absorb a version change due to xous-semver change
might as well also update the utra/svd generator dependencies
since that's been held off for a long time now.
