From: K1 <dongbeiouba@gmail.com>
Date: Tue, 16 Jan 2024 13:07:38 +0000 (+0800)
Subject: Optimize the implementation of ec_field_size()
X-Git-Tag: openssl-3.3.0-alpha1~247
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9170cc0398222778065e098e396b8eb8cd0de1d3;p=thirdparty%2Fopenssl.git

Optimize the implementation of ec_field_size()

No need to create and copy BIGNUM p, a and b, just call
EC_GROUP_get0_field() instead.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Yang <kaishen.yy@antfin.com>
(Merged from https://github.com/openssl/openssl/pull/23313)
---

diff --git a/crypto/sm2/sm2_crypt.c b/crypto/sm2/sm2_crypt.c
index 971d348cce4..b2d048cb594 100644
--- a/crypto/sm2/sm2_crypt.c
+++ b/crypto/sm2/sm2_crypt.c
@@ -46,25 +46,12 @@ IMPLEMENT_ASN1_FUNCTIONS(SM2_Ciphertext)
 
 static size_t ec_field_size(const EC_GROUP *group)
 {
-    /* Is there some simpler way to do this? */
-    BIGNUM *p = BN_new();
-    BIGNUM *a = BN_new();
-    BIGNUM *b = BN_new();
-    size_t field_size = 0;
+    const BIGNUM *p = EC_GROUP_get0_field(group);
 
-    if (p == NULL || a == NULL || b == NULL)
-       goto done;
-
-    if (!EC_GROUP_get_curve(group, p, a, b, NULL))
-        goto done;
-    field_size = (BN_num_bits(p) + 7) / 8;
-
- done:
-    BN_free(p);
-    BN_free(a);
-    BN_free(b);
+    if (p == NULL)
+        return 0;
 
-    return field_size;
+    return BN_num_bytes(p);
 }
 
 int ossl_sm2_plaintext_size(const unsigned char *ct, size_t ct_size,