X-Git-Url: https://git.openssl.org/?p=openssl.git;a=blobdiff_plain;f=crypto%2Fecdsa%2Fecs_ossl.c;h=50d02ed0691c8b9d85e8e5072ef3222de25389fd;hp=3518bb02e12350cace57f6c6e7ad05f2f56ebaf3;hb=992bdde62d2eea57bb85935a0c1a0ef0ca59b3da;hpb=bbcf3a9b300bc8109bb306a53f6f3445ba02e8e9

diff --git a/crypto/ecdsa/ecs_ossl.c b/crypto/ecdsa/ecs_ossl.c
index 3518bb02e1..50d02ed069 100644
--- a/crypto/ecdsa/ecs_ossl.c
+++ b/crypto/ecdsa/ecs_ossl.c
@@ -151,6 +151,16 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 			}
 		while (BN_is_zero(k));
 
+#ifdef ECDSA_POINT_MUL_NO_CONSTTIME
+		/* We do not want timing information to leak the length of k,
+		 * so we compute G*k using an equivalent scalar of fixed
+		 * bit-length. */
+
+		if (!BN_add(k, k, order)) goto err;
+		if (BN_num_bits(k) <= BN_num_bits(order))
+			if (!BN_add(k, k, order)) goto err;
+#endif /* def(ECDSA_POINT_MUL_NO_CONSTTIME) */
+
 		/* compute r the x-coordinate of generator * k */
 		if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx))
 		{