Merge tag 'keys-pkcs7-20140916' into keys-next

Changes for next to improve the matching of asymmetric keys and to improve the
handling of PKCS#7 certificates:

 (1) Provide a method to preparse the data supplied for matching a key.  This
     permits they key type to extract out the bits it needs for matching once
     only.

     Further, the type of search (direct lookup or iterative) can be set and
     the function used to actually check the match can be set by preparse
     rather than being hard coded for the type.

 (2) Improves asymmetric keys identification.

     Keys derived from X.509 certs now get labelled with IDs derived from their
     issuer and certificate number (required to match PKCS#7) and from their
     SKID and subject (required to match X.509).

     IDs are now binary and match criterion preparsing is provided so that
     criteria can be turned into binary blobs to make matching faster.

 (3) Improves PKCS#7 message handling to permit PKCS#7 messages without X.509
     cert lists to be matched to trusted keys, thereby allowing minimally sized
     PKCS#7 certs to be used.

 (4) Improves PKCS#7 message handling to better handle certificate chains that
     are broken due to unsupported crypto that can otherwise by used to
     intersect a trust keyring.

These must go on top of the PKCS#7 parser cleanup fixes.

Signed-off-by: David Howells <dhowells@redhat.com>