Disable DSA_FLAG_NO_EXP_CONSTTIME, always enable constant-time behavior.

Improved patch from Cesar Pereida. See
https://github.com/libressl-portable/openbsd/pull/61 for more details.

ok beck@

1 files changed, 10 insertions, 10 deletions

diff --git a/src/lib/libcrypto/dsa/dsa_key.c b/src/lib/libcrypto/dsa/dsa_key.c
index eaf6da8de7..4732c471ed 100644
--- a/src/lib/libcrypto/dsa/dsa_key.c
+++ b/src/lib/libcrypto/dsa/dsa_key.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: dsa_key.c,v 1.20 2014/10/18 17:20:40 jsing Exp $ */
+/* $OpenBSD: dsa_key.c,v 1.21 2016/06/21 04:16:53 bcook Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -104,18 +104,18 @@ dsa_builtin_keygen(DSA *dsa)
                 pub_key=dsa->pub_key;
         
         {
-                BIGNUM local_prk;
-                BIGNUM *prk;
+                BIGNUM *prk = BN_new();
 
-                if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
-                        BN_init(&local_prk);
-                        prk = &local_prk;
-                        BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
-                } else
-                        prk = priv_key;
+                if (prk == NULL)
+                        goto err;
+
+                BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
 
-                if (!BN_mod_exp(pub_key, dsa->g, prk, dsa->p, ctx))
+                if (!BN_mod_exp(pub_key, dsa->g, prk, dsa->p, ctx)) {
+                        BN_free(prk);
                         goto err;
+                }
+                BN_free(prk);
         }
 
         dsa->priv_key = priv_key;