[PATCH v12 06/10] x509: Detect sm2 keys by their parameters OID

[Stefan Berger]

Detect whether a key is an sm2 type of key by its OID in the parameters
array rather than assuming that everything under OID_id_ecPublicKey
is sm2, which is not the case.

Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: keyrings@xxxxxxxxxxxxxxx
Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
Reviewed-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
Tested-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
---
 crypto/asymmetric_keys/x509_cert_parser.c | 12 +++++++++++-
 include/linux/oid_registry.h              |  1 +
 lib/oid_registry.c                        | 24 +++++++++++++++++++++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index 52c9b455fc7d..1621ceaf5c95 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -459,6 +459,7 @@ int x509_extract_key_data(void *context, size_t hdrlen,
 			  const void *value, size_t vlen)
 {
 	struct x509_parse_context *ctx = context;
+	enum OID oid;
 
 	ctx->key_algo = ctx->last_oid;
 	switch (ctx->last_oid) {
@@ -470,7 +471,16 @@ int x509_extract_key_data(void *context, size_t hdrlen,
 		ctx->cert->pub->pkey_algo = "ecrdsa";
 		break;
 	case OID_id_ecPublicKey:
-		ctx->cert->pub->pkey_algo = "sm2";
+		if (parse_OID(ctx->params, ctx->params_size, &oid) != 0)
+			return -EBADMSG;
+
+		switch (oid) {
+		case OID_sm2:
+			ctx->cert->pub->pkey_algo = "sm2";
+			break;
+		default:
+			return -ENOPKG;
+		}
 		break;
 	default:
 		return -ENOPKG;
diff --git a/include/linux/oid_registry.h b/include/linux/oid_registry.h
index b504e2f36b25..f32d91895e4d 100644
--- a/include/linux/oid_registry.h
+++ b/include/linux/oid_registry.h
@@ -121,6 +121,7 @@ enum OID {
 };
 
 extern enum OID look_up_OID(const void *data, size_t datasize);
+extern int parse_OID(const void *data, size_t datasize, enum OID *oid);
 extern int sprint_oid(const void *, size_t, char *, size_t);
 extern int sprint_OID(enum OID, char *, size_t);
 
diff --git a/lib/oid_registry.c b/lib/oid_registry.c
index f7ad43f28579..3dfaa836e7c5 100644
--- a/lib/oid_registry.c
+++ b/lib/oid_registry.c
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/bug.h>
+#include <linux/asn1.h>
 #include "oid_registry_data.c"
 
 MODULE_DESCRIPTION("OID Registry");
@@ -92,6 +93,29 @@ enum OID look_up_OID(const void *data, size_t datasize)
 }
 EXPORT_SYMBOL_GPL(look_up_OID);
 
+/**
+ * parse_OID - Parse an OID from a bytestream
+ * @data: Binary representation of the header + OID
+ * @datasize: Size of the binary representation
+ * @oid: Pointer to oid to return result
+ *
+ * Parse an OID from a bytestream that holds the OID in the format
+ * ASN1_OID | length | oid. The length indicator must equal to datasize - 2.
+ * -EBADMSG is returned if the bytestream is too short.
+ */
+int parse_OID(const void *data, size_t datasize, enum OID *oid)
+{
+	const unsigned char *v = data;
+
+	/* we need 2 bytes of header and at least 1 byte for oid */
+	if (datasize < 3 || v[0] != ASN1_OID || v[1] != datasize - 2)
+		return -EBADMSG;
+
+	*oid = look_up_OID(data + 2, datasize - 2);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(parse_OID);
+
 /*
  * sprint_OID - Print an Object Identifier into a buffer
  * @data: The encoded OID to print
-- 
2.29.2