[PATCH v3 03/10] KEYS: X.509: Parse Basic Constraints for CA

Eric Snowberg
2022-12-14T00:35:05Z

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 x509_certificate. 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>
---
crypto/asymmetric_keys/x509_cert_parser.c | 9 +++++++++
crypto/asymmetric_keys/x509_parser.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 7a9b084e2043..b4443e507153 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -586,6 +586,15 @@ int x509_process_extension(void *context, size_t hdrlen,
return 0;
}

+ if (ctx->last_oid == OID_basicConstraints) {
+ if (vlen < 2 || v[0] != (ASN1_CONS_BIT | ASN1_SEQ))
+ return -EBADMSG;
+ if (v[1] != vlen - 2)
+ return -EBADMSG;
+ if (vlen >= 4 && v[1] != 0 && v[2] == ASN1_BOOL && v[3] == 1)
+ ctx->cert->root_ca = true;
+ }
+
return 0;
}

diff --git a/crypto/asymmetric_keys/x509_parser.h b/crypto/asymmetric_keys/x509_parser.h
index a299c9c56f40..7c5c0ad1c22e 100644
--- a/crypto/asymmetric_keys/x509_parser.h
+++ b/crypto/asymmetric_keys/x509_parser.h
@@ -38,6 +38,7 @@ struct x509_certificate {
bool self_signed; /* T if self-signed (check unsupported_sig too) */
bool unsupported_sig; /* T if signature uses unsupported crypto */
bool blacklisted;
+ bool root_ca; /* T if basic constraints CA is set */
};

/*
--
2.27.0