"crypt-util.c" is such a generic name, let's avoid that, in particular
as libc's/libcrypt's crypt() function is so generically named too that
one might thing this is about that. Let's hence be more precise, and
make clear that this is about cryptsetup, and nothing else.
We already had cryptsetup-util.[ch] in src/cryptsetup/ doing keyfile
management. To avoid the needless confusion, let's rename that file to
cryptsetup-keyfile.[ch].
Let's make loading of keys a bit more automatic and define a common
place where key files can be placed. Specifically, whenever a volume of
name "foo" is attempted, search for a key file in
/etc/cryptsetup-keys.d/foo.key and /run/cryptsetup-keys.d/foo.key,
unless a key file is declared explicitly.
With this scheme we have a simple discovery in place that should make it
more straightfoward wher to place keys, and requires no explicit
configuration to be used.
This adds a new crypttab option for volumes "pkcs11-uri=" which takes a
PKCS#11 URI. When used the key stored in the line's key file is
decrypted with the private key the PKCS#11 URI indiciates.
This means any smartcard that can store private RSA keys is usable for
unlocking LUKS devices.
