[PATCH v4 4/6] KEYS: X.509: Parse Key Usage

[Mimi Zohar]

On Mon, 2023-02-06 at 21:59 -0500, Eric Snowberg wrote:
> Parse the X.509 Key Usage.  The key usage extension defines the purpose of
> the key contained in the certificate.
> 
>    id-ce-keyUsage OBJECT IDENTIFIER ::=  { id-ce 15 }
> 
>       KeyUsage ::= BIT STRING {
>            digitalSignature        (0),
>            contentCommitment       (1),
>            keyEncipherment         (2),
>            dataEncipherment        (3),
>            keyAgreement            (4),
>            keyCertSign             (5),
>            cRLSign                 (6),
>            encipherOnly            (7),
>            decipherOnly            (8) }
> 
> If the keyCertSign or digitalSignature is set, store it in the
> public_key structure.  This will be used in a follow on patch that
> requires knowing the certificate key usage type.
> 
> Link: https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.3
> Signed-off-by: Eric Snowberg <eric.snowberg at oracle.com>

Reviewed-by: Mimi Zohar <zohar at linux.ibm.com>