Make explicit _ct and _nonct versions of bn_mod_exp funcitons that

matter for constant time, and make the public interface only used
external to the library.

This moves us to a model where the important things are constant time
versions unless you ask for them not to be, rather than the opposite.
I'll continue with this method by method.

Add regress tests for same.
ok jsing@

1 files changed, 4 insertions, 2 deletions

diff --git a/src/lib/libcrypto/dsa/dsa_ossl.c b/src/lib/libcrypto/dsa/dsa_ossl.c
index a28d3e9d1a..3f01a83a44 100644
--- a/src/lib/libcrypto/dsa/dsa_ossl.c
+++ b/src/lib/libcrypto/dsa/dsa_ossl.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: dsa_ossl.c,v 1.26 2016/06/21 04:16:53 bcook Exp $ */
+/* $OpenBSD: dsa_ossl.c,v 1.27 2017/01/21 09:38:59 beck Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -66,6 +66,8 @@
 #include <openssl/err.h>
 #include <openssl/sha.h>
 
+#include "bn_lcl.h"
+
 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
             BIGNUM **rp);
@@ -238,7 +240,7 @@ dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
                                         dsa->method_mont_p))
                         goto err;
         } else {
-                if (!BN_mod_exp_mont(r, dsa->g, &k, dsa->p, ctx, dsa->method_mont_p))
+                if (!BN_mod_exp_mont_ct(r, dsa->g, &k, dsa->p, ctx, dsa->method_mont_p))
                         goto err;
         }