From: Emilia Kasper <emilia@openssl.org>
Date: Fri, 24 Apr 2015 13:19:15 +0000 (+0200)
Subject: Correctly set Z_is_one on the return value in the NISTZ256 implementation.
X-Git-Tag: OpenSSL_1_1_0-pre1~1286
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=c028254b12a8ea0d0f8a677172eda2e2d78073f3;p=oweals%2Fopenssl.git

Correctly set Z_is_one on the return value in the NISTZ256 implementation.

Also add a few comments about constant-timeness.

Thanks to Brian Smith for reporting this issue.

Reviewed-by: Rich Salz <rsalz@openssl.org>
---

diff --git a/crypto/ec/ecp_nistz256.c b/crypto/ec/ecp_nistz256.c
index de9fbea515..b6eec7dc2c 100644
--- a/crypto/ec/ecp_nistz256.c
+++ b/crypto/ec/ecp_nistz256.c
@@ -587,6 +587,7 @@ static void ecp_nistz256_windowed_mul(const EC_GROUP *group,
     for (i = 0; i < num; i++) {
         P256_POINT *row = table[i];
 
+        /* This is an unusual input, we don't guarantee constant-timeness. */
         if ((BN_num_bits(scalar[i]) > 256) || BN_is_negative(scalar[i])) {
             BIGNUM *mod;
 
@@ -1331,9 +1332,11 @@ static int ecp_nistz256_points_mul(const EC_GROUP *group,
     bn_set_data(r->X, p.p.X, sizeof(p.p.X));
     bn_set_data(r->Y, p.p.Y, sizeof(p.p.Y));
     bn_set_data(r->Z, p.p.Z, sizeof(p.p.Z));
+    /* Not constant-time, but we're only operating on the public output. */
     bn_correct_top(r->X);
     bn_correct_top(r->Y);
     bn_correct_top(r->Z);
+    r->Z_is_one = is_one(p.p.Z);
 
     ret = 1;