Subject: [RFC PATCH v4 06/14] X.509: Parse Subject Alternative Name in certificates

From: "Aneesh Kumar K.V (Arm)" <[email-masked]>
Date: Mon, 27 Apr 2026 12:21:13 +0530

From: Lukas Wunner <[email-masked]>

The upcoming support for PCI device authentication with CMA-SPDM
(PCIe r6.1 sec 6.31) requires validating the Subject Alternative Name
in X.509 certificates.

Store a pointer to the Subject Alternative Name upon parsing for
consumption by CMA-SPDM.

Signed-off-by: Lukas Wunner <[email-masked]>
Reviewed-by: Wilfred Mallawa <[email-masked]>
Reviewed-by: Ilpo Järvinen <[email-masked]>
Reviewed-by: Jonathan Cameron <[email-masked]>
Acked-by: Dan Williams <[email-masked]>
Signed-off-by: Aneesh Kumar K.V (Arm) <[email-masked]>
---
 crypto/asymmetric_keys/x509_cert_parser.c | 9 +++++++++
 include/keys/x509-parser.h                | 2 ++
 2 files changed, 11 insertions(+)

diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index 37e4fb9da106..d81b7de4236c 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -596,6 +596,15 @@ int x509_process_extension(void *context, size_t hdrlen,
 		return 0;
 	}
 
+	if (ctx->last_oid == OID_subjectAltName) {
+		if (ctx->cert->raw_san)
+			return -EBADMSG;
+
+		ctx->cert->raw_san = v;
+		ctx->cert->raw_san_size = vlen;
+		return 0;
+	}
+
 	if (ctx->last_oid == OID_keyUsage) {
 		/*
 		 * Get hold of the keyUsage bit string
diff --git a/include/keys/x509-parser.h b/include/keys/x509-parser.h
index 8b68e720693a..4e6a05a8c7a6 100644
--- a/include/keys/x509-parser.h
+++ b/include/keys/x509-parser.h
@@ -38,6 +38,8 @@ struct x509_certificate {
 	unsigned	raw_subject_size;
 	unsigned	raw_skid_size;
 	const void	*raw_skid;		/* Raw subjectKeyId in ASN.1 */
+	const void	*raw_san;		/* Raw subjectAltName in ASN.1 */
+	unsigned	raw_san_size;
 	unsigned	index;
 	bool		seen;			/* Infinite recursion prevention */
 	bool		verified;
-- 
2.43.0