This changes the implementation of AndroidKeyStore-backed Cipher and
Mac to avoid throwing runtime exceptions during normal use. Runtime
exceptions will now be thrown only due to truly exceptional and
unrecoverable errors (e.g., keystore unreachable, or crypto primitive
not initialized).
This also changes the implementation of Cipher to cache any errors
encountered in Cipher.update until Cipher.doFinal which then throws
them as checked exceptions.
Bug: 20525947
Change-Id: I3c4ad57fe70abfbb817a79402f722a0208660727
This also adds the MAC length constraint on imported HMAC keys. HMAC
doesn't work without this constraint at the moment.
Bug: 18088752
Change-Id: I8613f58f5d2a84df00bcf6179d13e30619440330
