Instead of relying on openssl code for certificate parsing, use the
ASN.1 representation directly. All previous features are supported. Not
all the extensions are full parsed yet, but the code doesn't require
them for now.
The code makes accessing and modifying the certificate structure simpler
and requires less error checking than the original version. The code
leaves few TODOs, but nothing that destroys previous behaviour.
It still uses the cryptography.io backend for loading keys and producing
signatures for the certificates.
Implements: blueprint direct-asn1
Change-Id: Ic555d3d056ca8da7016e2d8b434506cf214d06a1
ef390f5f54