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)

(cherry picked from commit 8fc4aeb9521270ac74b29ce7f569939b0b39e685)

diff --git a/crypto/ec/ecp_nistz256.c b/crypto/ec/ecp_nistz256.c
index 153f39012a18cdc6ee5b7a5afee97ca4de23e1c0..0dbcfc2f3248b825585f004a2bb1d9e8f0913490 100644 (file)
--- a/crypto/ec/ecp_nistz256.c
+++ b/crypto/ec/ecp_nistz256.c
@@ -1110,28 +1110,12 @@ __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;
 }
@@ -1210,9 +1194,9 @@ __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;
             }