On Mon, Feb 06, 2023 at 09:59:55PM -0500, Eric Snowberg wrote:
> Parse the X.509 Basic Constraints. The basic constraints extension
> identifies whether the subject of the certificate is a CA.
>
> BasicConstraints ::= SEQUENCE {
> cA BOOLEAN DEFAULT FALSE,
> pathLenConstraint INTEGER (0..MAX) OPTIONAL }
>
> If the CA is true, store it in the public_key. This will be used
> in a follow on patch that requires knowing if the public key is a CA.
>
> Link: https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.9
> Signed-off-by: Eric Snowberg <eric.snowberg@xxxxxxxxxx>
> ---
> crypto/asymmetric_keys/x509_cert_parser.c | 22 ++++++++++++++++++++++
> include/crypto/public_key.h | 2 ++
> 2 files changed, 24 insertions(+)
>
> diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
> index 7a9b084e2043..77547d4bd94d 100644
> --- a/crypto/asymmetric_keys/x509_cert_parser.c
> +++ b/crypto/asymmetric_keys/x509_cert_parser.c
> @@ -586,6 +586,28 @@ int x509_process_extension(void *context, size_t hdrlen,
> return 0;
> }
>
> + if (ctx->last_oid == OID_basicConstraints) {
> + /*
> + * Get hold of the basicConstraints
> + * v[1] is the encoding size
> + * (Expect 0x2 or greater, making it 1 or more bytes)
> + * v[2] is the encoding type
> + * (Expect an ASN1_BOOL for the CA)
> + * v[3] is the contents of the ASN1_BOOL
> + * (Expect 1 if the CA is TRUE)
> + * vlen should match the entire extension size
> + */
> + if (v[0] != (ASN1_CONS_BIT | ASN1_SEQ))
> + return -EBADMSG;
> + if (vlen < 2)
> + return -EBADMSG;
> + if (v[1] != vlen - 2)
> + return -EBADMSG;
> + if (vlen >= 4 && v[1] != 0 && v[2] == ASN1_BOOL && v[3] == 1)
> + ctx->cert->pub->key_eflags |= 1 << KEY_EFLAG_CA;
> + return 0;
> + }
> +
> return 0;
> }
>
> diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
> index 6d61695e1cde..c401762850f2 100644
> --- a/include/crypto/public_key.h
> +++ b/include/crypto/public_key.h
> @@ -28,6 +28,8 @@ struct public_key {
> bool key_is_private;
> const char *id_type;
> const char *pkey_algo;
> + unsigned long key_eflags; /* key extension flags */
> +#define KEY_EFLAG_CA 0 /* set if the CA basic constraints is set */
> };
>
> extern void public_key_free(struct public_key *key);
> --
> 2.27.0
>
Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
BR, Jarkko
