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, 55 insertions, 1 deletions

diff --git a/src/regress/lib/libcrypto/exp/exptest.c b/src/regress/lib/libcrypto/exp/exptest.c
index 45ca5ac5f5..375628cb25 100644
--- a/src/regress/lib/libcrypto/exp/exptest.c
+++ b/src/regress/lib/libcrypto/exp/exptest.c
@@ -64,6 +64,15 @@
 #include <openssl/bn.h>
 #include <openssl/err.h>
 
+int BN_mod_exp_ct(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
+    const BIGNUM *m, BN_CTX *ctx);
+int BN_mod_exp_nonct(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
+    const BIGNUM *m, BN_CTX *ctx);
+int BN_mod_exp_mont_ct(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
+    const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
+int BN_mod_exp_mont_nonct(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
+    const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
+
 #define NUM_BITS        (BN_BITS*2)
 
 /*
@@ -116,6 +125,18 @@ static int test_exp_mod_zero(void)
         if (!a_is_zero_mod_one("BN_mod_exp", &r, &a))
                 failed = 1;
 
+        if (!BN_mod_exp_ct(&r, &a, &p, &m, ctx))
+                goto err;
+
+        if (!a_is_zero_mod_one("BN_mod_exp_ct", &r, &a))
+                failed = 1;
+
+        if (!BN_mod_exp_nonct(&r, &a, &p, &m, ctx))
+                goto err;
+
+        if (!a_is_zero_mod_one("BN_mod_exp_nonct", &r, &a))
+                failed = 1;
+
         if (!BN_mod_exp_recp(&r, &a, &p, &m, ctx))
                 goto err;
 
@@ -134,6 +155,18 @@ static int test_exp_mod_zero(void)
         if (!a_is_zero_mod_one("BN_mod_exp_mont", &r, &a))
                 failed = 1;
 
+        if (!BN_mod_exp_mont_ct(&r, &a, &p, &m, ctx, NULL))
+                goto err;
+
+        if (!a_is_zero_mod_one("BN_mod_exp_mont_ct", &r, &a))
+                failed = 1;
+
+        if (!BN_mod_exp_mont_nonct(&r, &a, &p, &m, ctx, NULL))
+                goto err;
+
+        if (!a_is_zero_mod_one("BN_mod_exp_mont_nonct", &r, &a))
+                failed = 1;
+
         if (!BN_mod_exp_mont_consttime(&r, &a, &p, &m, ctx, NULL)) {
                 goto err;
         }
@@ -175,7 +208,8 @@ int main(int argc, char *argv[])
         BIO *out = NULL;
         int i, ret;
         unsigned char c;
-        BIGNUM *r_mont, *r_mont_const, *r_recp, *r_simple, *a, *b, *m;
+        BIGNUM *r_mont, *r_mont_const, *r_recp, *r_simple,
+            *r_mont_ct, *r_mont_nonct, *a, *b, *m;
 
         ERR_load_BN_strings();
 
@@ -184,6 +218,8 @@ int main(int argc, char *argv[])
                 exit(1);
         r_mont = BN_new();
         r_mont_const = BN_new();
+        r_mont_ct = BN_new();
+        r_mont_nonct = BN_new();
         r_recp = BN_new();
         r_simple = BN_new();
         a = BN_new();
@@ -221,6 +257,20 @@ int main(int argc, char *argv[])
                         exit(1);
                 }
 
+                ret = BN_mod_exp_mont_ct(r_mont_ct, a, b, m, ctx, NULL);
+                if (ret <= 0) {
+                        printf("BN_mod_exp_mont_ct() problems\n");
+                        ERR_print_errors(out);
+                        exit(1);
+                }
+
+                ret = BN_mod_exp_mont_nonct(r_mont_nonct, a, b, m, ctx, NULL);
+                if (ret <= 0) {
+                        printf("BN_mod_exp_mont_nonct() problems\n");
+                        ERR_print_errors(out);
+                        exit(1);
+                }
+
                 ret = BN_mod_exp_recp(r_recp, a, b, m, ctx);
                 if (ret <= 0) {
                         printf("BN_mod_exp_recp() problems\n");
@@ -254,6 +304,10 @@ int main(int argc, char *argv[])
                                 printf("\nsimple and mont const time results differ\n");
                         if (BN_cmp(r_simple, r_recp) != 0)
                                 printf("\nsimple and recp results differ\n");
+                        if (BN_cmp(r_mont, r_mont_ct) != 0)
+                                printf("\nmont_ct and mont results differ\n");
+                        if (BN_cmp(r_mont_ct, r_mont_nonct) != 0)
+                                printf("\nmont_ct and mont_nonct results differ\n");
 
                         printf("a (%3d) = ", BN_num_bits(a));
                         BN_print(out, a);