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@

4 files changed, 13 insertions, 9 deletions

diff --git a/src/lib/libcrypto/dsa/dsa_ameth.c b/src/lib/libcrypto/dsa/dsa_ameth.c
index 3e434701aa..92ad02e187 100644
--- a/src/lib/libcrypto/dsa/dsa_ameth.c
+++ b/src/lib/libcrypto/dsa/dsa_ameth.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: dsa_ameth.c,v 1.20 2016/10/19 16:49:11 jsing Exp $ */
+/* $OpenBSD: dsa_ameth.c,v 1.21 2017/01/21 09:38:59 beck Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2006.
  */
@@ -66,8 +66,8 @@
 #include <openssl/err.h>
 #include <openssl/x509.h>
 
-
 #include "asn1_locl.h"
+#include "bn_lcl.h"
 
 static int
 dsa_pub_decode(EVP_PKEY *pkey, X509_PUBKEY *pubkey)
@@ -224,7 +224,7 @@ dsa_priv_decode(EVP_PKEY *pkey, PKCS8_PRIV_KEY_INFO *p8)
                 goto dsaerr;
         }
 
-        if (!BN_mod_exp(dsa->pub_key, dsa->g, dsa->priv_key, dsa->p, ctx)) {
+        if (!BN_mod_exp_ct(dsa->pub_key, dsa->g, dsa->priv_key, dsa->p, ctx)) {
                 DSAerr(DSA_F_DSA_PRIV_DECODE,DSA_R_BN_ERROR);
                 goto dsaerr;
         }
diff --git a/src/lib/libcrypto/dsa/dsa_gen.c b/src/lib/libcrypto/dsa/dsa_gen.c
index 7ddb7fec5e..d627e5ae9c 100644
--- a/src/lib/libcrypto/dsa/dsa_gen.c
+++ b/src/lib/libcrypto/dsa/dsa_gen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: dsa_gen.c,v 1.22 2015/07/15 18:34:37 miod Exp $ */
+/* $OpenBSD: dsa_gen.c,v 1.23 2017/01/21 09:38:59 beck Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -68,6 +68,7 @@
 #include <openssl/evp.h>
 #include <openssl/sha.h>
 
+#include "bn_lcl.h"
 #include "dsa_locl.h"
 
 int
@@ -315,7 +316,7 @@ end:
 
         for (;;) {
                 /* g=test^r0%p */
-                if (!BN_mod_exp_mont(g, test, r0, p, ctx, mont))
+                if (!BN_mod_exp_mont_ct(g, test, r0, p, ctx, mont))
                         goto err;
                 if (!BN_is_one(g))
                         break;
diff --git a/src/lib/libcrypto/dsa/dsa_key.c b/src/lib/libcrypto/dsa/dsa_key.c
index fc4eb9c433..cb95e1369c 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 1.22 2016/06/30 02:02:06 bcook Exp $ */
+/* $OpenBSD: dsa_key.c,v 1.23 2017/01/21 09:38:59 beck Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -65,6 +65,7 @@
 
 #include <openssl/bn.h>
 #include <openssl/dsa.h>
+#include "bn_lcl.h"
 
 static int dsa_builtin_keygen(DSA *dsa);
 
@@ -108,7 +109,7 @@ dsa_builtin_keygen(DSA *dsa)
 
                 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_ct(pub_key, dsa->g, &prk, dsa->p, ctx))
                         goto err;
         }
 
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;
         }