ec/ecp_nistz256.c: fix ecp_nistz256_set_from_affine.

ecp_nistz256_set_from_affine is called when application attempts to use
custom generator, i.e. rarely. Even though it was wrong, it didn't
affect point operations, they were just not as fast as expected.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6738)

diff --git a/crypto/ec/ecp_nistz256.c b/crypto/ec/ecp_nistz256.c
index 4b5fc62797516a10afbed016464cb534eb09c36b..54c9ed280808da97a55aac01964fb2e20eb91e73 100644 (file)
--- a/crypto/ec/ecp_nistz256.c
+++ b/crypto/ec/ecp_nistz256.c
@@ -1104,28 +1104,12 @@ __owur static int ecp_nistz256_set_from_affine(EC_POINT *out, const EC_GROUP *gr
                                                const P256_POINT_AFFINE *in,
                                                BN_CTX *ctx)
 {
-    BIGNUM *x, *y;
-    BN_ULONG d_x[P256_LIMBS], d_y[P256_LIMBS];
     int ret = 0;
 
-    x = BN_new();
-    if (x == NULL)
-        return 0;
-    y = BN_new();
-    if (y == NULL) {
-        BN_free(x);
-        return 0;
-    }
-    memcpy(d_x, in->X, sizeof(d_x));
-    bn_set_static_words(x, d_x, P256_LIMBS);
-
-    memcpy(d_y, in->Y, sizeof(d_y));
-    bn_set_static_words(y, d_y, P256_LIMBS);
-
-    ret = EC_POINT_set_affine_coordinates_GFp(group, out, x, y, ctx);
-
-    BN_free(x);
-    BN_free(y);
+    if ((ret = bn_set_words(out->X, in->X, P256_LIMBS))
+        && (ret = bn_set_words(out->Y, in->Y, P256_LIMBS))
+        && (ret = bn_set_words(out->Z, ONE, P256_LIMBS)))
+        out->Z_is_one = 1;
 
     return ret;
 }
@@ -1181,9 +1165,9 @@ __owur static int ecp_nistz256_points_mul(const EC_GROUP *group,
             if (pre_comp_generator == NULL)
                 goto err;
 
+            ecp_nistz256_gather_w7(&p.a, pre_comp->precomp[0], 1);
             if (!ecp_nistz256_set_from_affine(pre_comp_generator,
-                                              group, pre_comp->precomp[0],
-                                              ctx)) {
+                                              group, &p.a, ctx)) {
                 EC_POINT_free(pre_comp_generator);
                 goto err;
             }