On Tue, 2022-04-05 at 21:53 -0400, 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 is set, store it in the x509_certificate structure.
> This will be used in a follow on patch that requires knowing the
> certificate key usage type.
>
> Signed-off-by: Eric Snowberg <eric.snowberg@xxxxxxxxxx>
> ---
> crypto/asymmetric_keys/x509_cert_parser.c | 20 ++++++++++++++++++++
> crypto/asymmetric_keys/x509_parser.h | 1 +
> 2 files changed, 21 insertions(+)
>
> diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
> index 30f7374ea9c0..a89f1e0c8a0f 100644
> --- a/crypto/asymmetric_keys/x509_cert_parser.c
> +++ b/crypto/asymmetric_keys/x509_cert_parser.c
> @@ -576,6 +576,26 @@ int x509_process_extension(void *context, size_t hdrlen,
> return 0;
> }
>
> + if (ctx->last_oid == OID_keyUsage) {
> + /*
> + * Get hold of the keyUsage bit string to validate keyCertSign
> + * v[1] is the encoding size
> + * (Expect either 0x02 or 0x03, making it 1 or 2 bytes)
> + * v[2] is the number of unused bits in the bit string
> + * (If >= 3 keyCertSign is missing)
> + * v[3] and possibly v[4] contain the bit string
> + * 0x04 is where KeyCertSign lands in this bit string (from
> + * RFC 5280 4.2.1.3)
> + */
> + if (v[0] != ASN1_BTS || vlen < 4)
> + return -EBADMSG;
> + if (v[1] == 0x02 && v[2] <= 2 && (v[3] & 0x04))
> + ctx->cert->is_kcs_set = true;
> + else if (vlen > 4 && v[1] == 0x03 && (v[3] & 0x04))
> + ctx->cert->is_kcs_set = true;
> + return 0;
> + }
> +
> if (ctx->last_oid == OID_authorityKeyIdentifier) {
> /* Get hold of the CA key fingerprint */
> ctx->raw_akid = v;
> diff --git a/crypto/asymmetric_keys/x509_parser.h b/crypto/asymmetric_keys/x509_parser.h
> index dc45df9f6594..d6ac0985d8a5 100644
> --- a/crypto/asymmetric_keys/x509_parser.h
> +++ b/crypto/asymmetric_keys/x509_parser.h
> @@ -39,6 +39,7 @@ struct x509_certificate {
> bool unsupported_sig; /* T if signature uses unsupported crypto */
> bool blacklisted;
> bool is_root_ca; /* T if basic constraints CA is set */
> + bool is_kcs_set; /* T if keyCertSign is set */
> };
Again there is no need to prefix the variable with "is_" or suffix it
with "set". Simply naming the variable "cert_signing" or
"keycertsign", like "self_signed", will improve code readability.
thanks,
Mimi
