Test that a ^ 0 mod -1 is always 0
Check all functions that do this.
@@ -2063,6 +2063,53 @@ err:
return st;
}
+static int test_expmodone(void)
+{
+ int ret = 0, i;
+ BIGNUM *r = BN_new();
+ BIGNUM *a = BN_new();
+ BIGNUM *p = BN_new();
+ BIGNUM *m = BN_new();
+
+ if (!TEST_ptr(r)
+ || !TEST_ptr(a)
+ || !TEST_ptr(p)
+ || !TEST_ptr(p)
+ || !TEST_ptr(m)
+ || !TEST_true(BN_set_word(a, 1))
+ || !TEST_true(BN_set_word(p, 0))
+ || !TEST_true(BN_set_word(m, 1)))
+ goto err;
+
+ /* Calculate r = 1 ^ 0 mod 1, and check the result is always 0 */
+ for (i = 0; i < 2; i++) {
+ if (!TEST_true(BN_mod_exp(r, a, p, m, NULL))
+ || !TEST_BN_eq_zero(r)
+ || !TEST_true(BN_mod_exp_mont(r, a, p, m, NULL, NULL))
+ || !TEST_BN_eq_zero(r)
+ || !TEST_true(BN_mod_exp_mont_consttime(r, a, p, m, NULL, NULL))
+ || !TEST_BN_eq_zero(r)
+ || !TEST_true(BN_mod_exp_mont_word(r, 1, p, m, NULL, NULL))
+ || !TEST_BN_eq_zero(r)
+ || !TEST_true(BN_mod_exp_simple(r, a, p, m, NULL))
+ || !TEST_BN_eq_zero(r)
+ || !TEST_true(BN_mod_exp_recp(r, a, p, m, NULL))
+ || !TEST_BN_eq_zero(r))
+ goto err;
+ /* Repeat for r = 1 ^ 0 mod -1 */
+ if (i == 0)
+ BN_set_negative(m, 1);
+ }
+
+ ret = 1;
+err:
+ BN_free(r);
+ BN_free(a);
+ BN_free(p);
+ BN_free(m);
+ return ret;
+}
+
static int test_smallprime(void)
{
static const int kBits = 10;
@@ -2189,6 +2236,7 @@ int setup_tests(void)
ADD_TEST(test_negzero);
ADD_TEST(test_badmod);
ADD_TEST(test_expmodzero);
+ ADD_TEST(test_expmodone);
ADD_TEST(test_smallprime);
ADD_TEST(test_swap);
#ifndef OPENSSL_NO_EC2M
