[PATCH] crypto: sm2 - remove unnecessary reset operations

From: Tianjia Zhang
Date: Thu Oct 15 2020 - 05:24:45 EST


This is an algorithm optimization. The reset operation when
setting the public key is repeated and redundant, so remove it.
At the same time, `sm2_ecc_os2ec()` is optimized to make the
function more simpler and more in line with the Linux code style.

Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
---
crypto/sm2.c | 75 ++++++++++++++++++++--------------------------------
1 file changed, 29 insertions(+), 46 deletions(-)

diff --git a/crypto/sm2.c b/crypto/sm2.c
index 767e160333f6..b21addc3ac06 100644
--- a/crypto/sm2.c
+++ b/crypto/sm2.c
@@ -119,12 +119,6 @@ static void sm2_ec_ctx_deinit(struct mpi_ec_ctx *ec)
memset(ec, 0, sizeof(*ec));
}

-static int sm2_ec_ctx_reset(struct mpi_ec_ctx *ec)
-{
- sm2_ec_ctx_deinit(ec);
- return sm2_ec_ctx_init(ec);
-}
-
/* RESULT must have been initialized and is set on success to the
* point given by VALUE.
*/
@@ -132,55 +126,48 @@ static int sm2_ecc_os2ec(MPI_POINT result, MPI value)
{
int rc;
size_t n;
- const unsigned char *buf;
- unsigned char *buf_memory;
+ unsigned char *buf;
MPI x, y;

- n = (mpi_get_nbits(value)+7)/8;
- buf_memory = kmalloc(n, GFP_KERNEL);
- rc = mpi_print(GCRYMPI_FMT_USG, buf_memory, n, &n, value);
- if (rc) {
- kfree(buf_memory);
- return rc;
- }
- buf = buf_memory;
+ n = MPI_NBYTES(value);
+ buf = kmalloc(n, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;

- if (n < 1) {
- kfree(buf_memory);
- return -EINVAL;
- }
- if (*buf != 4) {
- kfree(buf_memory);
- return -EINVAL; /* No support for point compression. */
- }
- if (((n-1)%2)) {
- kfree(buf_memory);
- return -EINVAL;
- }
- n = (n-1)/2;
+ rc = mpi_print(GCRYMPI_FMT_USG, buf, n, &n, value);
+ if (rc)
+ goto err_freebuf;
+
+ rc = -EINVAL;
+ if (n < 1 || ((n - 1) % 2))
+ goto err_freebuf;
+ /* No support for point compression */
+ if (*buf != 0x4)
+ goto err_freebuf;
+
+ rc = -ENOMEM;
+ n = (n - 1) / 2;
x = mpi_read_raw_data(buf + 1, n);
- if (!x) {
- kfree(buf_memory);
- return -ENOMEM;
- }
+ if (!x)
+ goto err_freebuf;
y = mpi_read_raw_data(buf + 1 + n, n);
- kfree(buf_memory);
- if (!y) {
- mpi_free(x);
- return -ENOMEM;
- }
+ if (!y)
+ goto err_freex;

mpi_normalize(x);
mpi_normalize(y);
-
mpi_set(result->x, x);
mpi_set(result->y, y);
mpi_set_ui(result->z, 1);

- mpi_free(x);
- mpi_free(y);
+ rc = 0;

- return 0;
+ mpi_free(y);
+err_freex:
+ mpi_free(x);
+err_freebuf:
+ kfree(buf);
+ return rc;
}

struct sm2_signature_ctx {
@@ -399,10 +386,6 @@ static int sm2_set_pub_key(struct crypto_akcipher *tfm,
MPI a;
int rc;

- rc = sm2_ec_ctx_reset(ec);
- if (rc)
- return rc;
-
ec->Q = mpi_point_new(0);
if (!ec->Q)
return -ENOMEM;
--
2.19.1.3.ge56e4f7