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

From: Alistair Francis
Date: Wed Feb 26 2025 - 22:11:05 EST


From: Lukas Wunner <lukas@xxxxxxxxx>

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@xxxxxxxxx>
Reviewed-by: Wilfred Mallawa <wilfred.mallawa@xxxxxxx>
Reviewed-by: Alistair Francis <alistair.francis@xxxxxxx>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Acked-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
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