Bring back the functionality whereby an asymmetric key can be matched with a
partial match on one of its IDs.

Whilst we're at it, allow for the possibility of having an increased number of
IDs.
Reported-by: NDmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: NDmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Implement the first step in using binary key IDs for asymmetric keys rather
than hex string keys.

The previously added match data preparsing will be able to convert hex
criterion strings into binary which can then be compared more rapidly.

Further, we actually want more then one ID string per public key.  The problem
is that X.509 certs refer to other X.509 certs by matching Issuer + AuthKeyId
to Subject + SubjKeyId, but PKCS#7 messages match against X.509 Issuer +
SerialNumber.

This patch just provides facilities for a later patch to make use of.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>

Create a key type that can be used to represent an asymmetric key type for use
in appropriate cryptographic operations, such as encryption, decryption,
signature generation and signature verification.

The key type is "asymmetric" and can provide access to a variety of
cryptographic algorithms.

Possibly, this would be better as "public_key" - but that has the disadvantage
that "public key" is an overloaded term.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>