linux-kernel - [RFC v2 02/20] X.509: Parse Subject Alternative Name in certificates

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Message-ID: <20250227030952.2319050-3-alistair@alistair23.me>
Date: Thu, 27 Feb 2025 13:09:34 +1000
From: Alistair Francis <alistair@...stair23.me>
To: linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lukas@...ner.de,
	linux-pci@...r.kernel.org,
	bhelgaas@...gle.com,
	Jonathan.Cameron@...wei.com,
	rust-for-linux@...r.kernel.org,
	akpm@...ux-foundation.org
Cc: boqun.feng@...il.com,
	bjorn3_gh@...tonmail.com,
	wilfred.mallawa@....com,
	aliceryhl@...gle.com,
	ojeda@...nel.org,
	alistair23@...il.com,
	a.hindborg@...nel.org,
	tmgross@...ch.edu,
	gary@...yguo.net,
	alex.gaynor@...il.com,
	benno.lossin@...ton.me,
	Alistair Francis <alistair.francis@....com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Dan Williams <dan.j.williams@...el.com>
Subject: [RFC v2 02/20] X.509: Parse Subject Alternative Name in certificates

From: Lukas Wunner <lukas@...ner.de>

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 <lukas@...ner.de>
Reviewed-by: Wilfred Mallawa <wilfred.mallawa@....com>
Reviewed-by: Alistair Francis <alistair.francis@....com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Acked-by: Dan Williams <dan.j.williams@...el.com>
---
 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 ee2fdab42334..ff1db59d4037 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -572,6 +572,15 @@ 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 37436a5c7526..8e450befe3b9 100644
--- a/include/keys/x509-parser.h
+++ b/include/keys/x509-parser.h
@@ -36,6 +36,8 @@ 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;
-- 
2.48.1