Re: [PATCH v6 2/4] x509: Detect sm2 keys by their parameters OID

[Tianjia Zhang]

On 2/1/21 7:32 AM, Stefan Berger wrote:
> 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.
>
> Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> Cc: David Howells <dhowells@xxxxxxxxxx>
> Cc: keyrings@xxxxxxxxxxxxxxx
> ---
>   crypto/asymmetric_keys/x509_cert_parser.c | 12 +++++++++++-
>   include/linux/oid_registry.h              |  1 +
>   lib/oid_registry.c                        | 13 +++++++++++++
>   3 files changed, 25 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 4462ed2c18cd..d4982e42c0d2 100644
> --- a/include/linux/oid_registry.h
> +++ b/include/linux/oid_registry.h
> @@ -117,6 +117,7 @@ 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..508e0b34b5f0 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 +93,18 @@ enum OID look_up_OID(const void *data, size_t datasize)
>   }
>   EXPORT_SYMBOL_GPL(look_up_OID);
>   
> +int parse_OID(const void *data, size_t datasize, enum OID *oid)
> +{
> +	const unsigned char *v = data;
> +
> +	if (datasize < 2 || 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

Great job, I'm just curious why we need to add a new function, this 
seems unnecessary, if possible, please add

Reviewed-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>

Best regards,
Tianjia