Now all keys are encrypted when they're not in use to thwart cold-boot
attacks. Furthermore, all unlocking messages are sent in bulk to avoid
fragmentation and improve performance.
Previously, we wrote the passphrase contents to a temporary file on
/dev/shm and then wiped it afterwards. This is odd, why don't we use a
pipe for this purpose, like it's intended to be used? Replace all of
that previous code by piped IPC.
We'll now parse the response messages on the client side, abort after a
previously defined timeout and trigger the LUKS unlocking process, if
requested (although the latter isn't fully implemented yet).
Clients now broadcast their host UUID and magic number via UDP, but the
server does not respond nor would the client trigger anything if the
server did.
TLSv1.3 behaves differently in how PSK identity/PSK identity hints are
exchanged, at least in regards to OpenSSL. This caused the TLS client to
not send their TLS identity to the server, which rejected the connection
(it expected "luksrku v1"). Couldn't solve it with TLSv1.3, so we're now
simply forcing TLSv1.2.
Can now unlock a specified number of hosts as specified on the command
line (e.g., if you want a luksrku client run indefinitely) and also used
the already implemented blacklisting functionality (i.e., if an
unlocking is unsuccessful, it is retried in 120 seconds, not
immediately, as not to spam servers with illegal credentials).
