On Nov 18, 2021, at 3:59 PM, Mimi Zohar [off-list ref] wrote:

Hi Eric,

On Mon, 2021-11-15 at 19:15 -0500, Eric Snowberg wrote:

quoted

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 a new public_key field call key_is_ca.
This will be used in a follow on patch that requires knowing if the
public key is a CA.

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
---
v7: Initial version
---
crypto/asymmetric_keys/x509_cert_parser.c | 9 +++++++++
include/crypto/public_key.h               | 1 +
2 files changed, 10 insertions(+)

diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index 6d003096b5bc..f4299b8a4926 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c

@@ -571,6 +571,15 @@ int x509_process_extension(void *context, size_t hdrlen,

		return 0;
	}

+	if (ctx->last_oid == OID_basicConstraints) {
+		if (v[0] != (ASN1_CONS_BIT | ASN1_SEQ))
+			return -EBADMSG;
+		if (v[1] != vlen - 2)
+			return -EBADMSG;
+		if (v[1] != 0 && v[2] == ASN1_BOOL && v[3] == 1)
+			ctx->cert->pub->key_is_ca = true;
+	}
+
	return 0;
}

diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
index a9b2e600b7cc..61c66be80995 100644
--- a/include/crypto/public_key.h
+++ b/include/crypto/public_key.h

@@ -28,6 +28,7 @@ struct public_key {

	bool key_is_private;
	const char *id_type;
	const char *pkey_algo;
+	bool key_is_ca;

David added "key_is_private" intentionally where he did.  Adding the
"key_is_ca" immediately afterwards doesn't change the struct size.

Ok, I’ll change that in the next round.  Thanks.