x509: Detect sm2 keys by their parameters OID

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@redhat.com>
Cc: keyrings@vger.kernel.org
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Tested-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 24 insertions, 0 deletions

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