Re: [PATCH V4 02/15] asymmetric keys: implement EMSA_PKCS1-v1_5-ENCODE in rsa

Hi Phil, 

First! Thanks for your time to review my patch!

於 一，2013-09-23 於 19:49 +0300，Phil Carmody 提到：

On Sun, Sep 15, 2013 at 08:56:48AM +0800, Lee, Chun-Yi wrote:

quoted

Implement EMSA_PKCS1-v1_5-ENCODE [RFC3447 sec 9.2] in rsa.c. It's the
first step of signature generation operation (RSASSA-PKCS1-v1_5-SIGN).

This patch is temporary set emLen to pks->k, and temporary set EM to
pks->S for debugging. We will replace the above values to real signature
after implement RSASP1.

The naming of EMSA_PKCS1_v1_5_ENCODE and the variables used in this function
accord PKCS#1 spec but not follow kernel naming convention, it useful when look
at them with spec.

Reference: ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1v2/pkcs1ietffinal.txt
Reference: http://www.emc.com/collateral/white-papers/h11300-pkcs-1v2-2-rsa-cryptography-standard-wp.pdf

V2:

You're now at V4.

The V4 is for whole patchset, I didn't do any modify in this patch in
this version.
The version define maybe confuse between separate and whole patchset, I
will avoid it.

quoted

- Clean up naming of variable: replace _EM by EM, replace EM by EM_tmp.
- Add comment to EMSA_PKCS1-v1_5-ENCODE function.

Cc: Pavel Machek <redacted>
Reviewed-by: Jiri Kosina <redacted>
Signed-off-by: Lee, Chun-Yi <jlee-IBi9RG/b67k@public.gmane.org>
---
 crypto/asymmetric_keys/rsa.c |  163 +++++++++++++++++++++++++++++++++++++++++-
 include/crypto/public_key.h  |    2 +
 2 files changed, 164 insertions(+), 1 deletions(-)

diff --git a/crypto/asymmetric_keys/rsa.c b/crypto/asymmetric_keys/rsa.c
index 47f3be4..352ba45 100644
--- a/crypto/asymmetric_keys/rsa.c
+++ b/crypto/asymmetric_keys/rsa.c

@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
+#include <crypto/hash.h>
 #include "public_key.h"
 #include "private_key.h"
 

@@ -152,6 +153,132 @@ static int RSA_I2OSP(MPI x, size_t xLen, u8 **_X)
 }
 
 /*
+ * EMSA_PKCS1-v1_5-ENCODE [RFC3447 sec 9.2]
+ * @M: message to be signed, an octet string
+ * @emLen: intended length in octets of the encoded message
+ * @hash_algo: hash function (option)
+ * @hash: true means hash M, otherwise M is already a digest
+ * @EM: encoded message, an octet string of length emLen
+ *
+ * This function is a implementation of the EMSA-PKCS1-v1_5 encoding operation
+ * in RSA PKCS#1 spec. It used by the signautre generation operation of
+ * RSASSA-PKCS1-v1_5 to encode message M to encoded message EM.
+ *
+ * The variables used in this function accord PKCS#1 spec but not follow kernel
+ * naming convention, it useful when look at them with spec.
+ */
+static int EMSA_PKCS1_v1_5_ENCODE(const u8 *M, size_t emLen,
+		enum pkey_hash_algo hash_algo, const bool hash,
+		u8 **EM, struct public_key_signature *pks)
+{
+	u8 *digest;
+	struct crypto_shash *tfm;
+	struct shash_desc *desc;
+	size_t digest_size, desc_size;
+	size_t tLen;
+	u8 *T, *PS, *EM_tmp;
+	int i, ret;
+
+	pr_info("EMSA_PKCS1_v1_5_ENCODE start\n");
+
+	if (!RSA_ASN1_templates[hash_algo].data)
+		ret = -ENOTSUPP;

...

quoted

+	else
+		pks->pkey_hash_algo = hash_algo;
+
+	/* 1) Apply the hash function to the message M to produce a hash value H */
+	tfm = crypto_alloc_shash(pkey_hash_algo[hash_algo], 0, 0);
+	if (IS_ERR(tfm))
+		return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
+
+	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
+	digest_size = crypto_shash_digestsize(tfm);
+
+	ret = -ENOMEM;

The earlier "ret = -ENOTSUPP;" is either unused because you return at the IS_ERR,
or unused because you overwrite it here. I'm a little disappointed that
the compiler didn't recognise that something was assigned to a value that 
is never used.

Phil

Yes, Dmitry also pointed out this issue, I should not go on the hash
process if the hash algorithm didn't support.

I will change fix this problem in next version. 


Thanks a lot!
Joey Lee

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