From: Bernd Edlinger <bernd.edlinger@hotmail.de>
Date: Fri, 6 Sep 2019 06:46:46 +0000 (+0200)
Subject: Fix a SCA leak in BN_generate_dsa_nonce
X-Git-Tag: OpenSSL_1_1_1d~28
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=9e1403d91a42d917e684a37a99fa98a0025253c0;p=oweals%2Fopenssl.git

Fix a SCA leak in BN_generate_dsa_nonce

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/9782)

(cherry picked from commit 31ca19403d56ad71d823cf62990518dfc6905bb4)
---

diff --git a/crypto/bn/bn_rand.c b/crypto/bn/bn_rand.c
index c0d1a32292..214768311a 100644
--- a/crypto/bn/bn_rand.c
+++ b/crypto/bn/bn_rand.c
@@ -225,8 +225,7 @@ int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
         goto err;
 
     /* We copy |priv| into a local buffer to avoid exposing its length. */
-    todo = sizeof(priv->d[0]) * priv->top;
-    if (todo > sizeof(private_bytes)) {
+    if (BN_bn2binpad(priv, private_bytes, sizeof(private_bytes)) < 0) {
         /*
          * No reasonable DSA or ECDSA key should have a private key this
          * large and we don't handle this case in order to avoid leaking the
@@ -235,8 +234,6 @@ int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
         BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_PRIVATE_KEY_TOO_LARGE);
         goto err;
     }
-    memcpy(private_bytes, priv->d, todo);
-    memset(private_bytes + todo, 0, sizeof(private_bytes) - todo);
 
     for (done = 0; done < num_k_bytes;) {
         if (RAND_priv_bytes(random_bytes, sizeof(random_bytes)) != 1)