Share ecc point validation function in testutils.c.

* testsuite/testutils.c (test_ecc_point_valid_p): New function,
moved from...
* testsuite/ecdsa-keygen-test.c (ecc_valid_p): ... old copy.
* testsuite/gostdsa-keygen-test.c (ecc_valid_p): ... old copy.
* testsuite/testutils.h: Declare it.

1 files changed, 70 insertions, 0 deletions

diff --git a/testsuite/testutils.c b/testsuite/testutils.c
index 9bb250b4..b3ca8043 100644
--- a/testsuite/testutils.c
+++ b/testsuite/testutils.c
@@ -1745,6 +1745,76 @@ const struct ecc_curve * const ecc_curves[] = {
   NULL
 };
 
+int
+test_ecc_point_valid_p (struct ecc_point *pub)
+{
+  mpz_t t, x, y;
+  mpz_t lhs, rhs;
+  int res;
+  mp_size_t size;
+
+  size = pub->ecc->p.size;
+
+  /* First check range */
+  if (mpn_cmp (pub->p, pub->ecc->p.m, size) >= 0
+      || mpn_cmp (pub->p + size, pub->ecc->p.m, size) >= 0)
+    return 0;
+
+  mpz_init (lhs);
+  mpz_init (rhs);
+
+  mpz_roinit_n (x, pub->p, size);
+  mpz_roinit_n (y, pub->p + size, size);
+
+  mpz_mul (lhs, y, y);
+
+  if (pub->ecc->p.bit_size == 255)
+    {
+      /* Check that
+	 121666 (1 + x^2 - y^2) = 121665 x^2 y^2 */
+      mpz_t x2;
+      mpz_init (x2);
+      mpz_mul (x2, x, x); /* x^2 */
+      mpz_mul (rhs, x2, lhs); /* x^2 y^2 */
+      mpz_sub (lhs, x2, lhs); /* x^2 - y^2 */
+      mpz_add_ui (lhs, lhs, 1); /* 1 + x^2 - y^2 */
+      mpz_mul_ui (lhs, lhs, 121666);
+      mpz_mul_ui (rhs, rhs, 121665);
+
+      mpz_clear (x2);
+    }
+  else if (pub->ecc->p.bit_size == 448)
+    {
+      /* Check that
+	 x^2 + y^2 = 1 - 39081 x^2 y^2 */
+      mpz_t x2, d;
+      mpz_init (x2);
+      mpz_init_set_ui (d, 39081);
+      mpz_mul (x2, x, x); /* x^2 */
+      mpz_mul (d, d, x2); /* 39081 x^2 */
+      mpz_set_ui (rhs, 1);
+      mpz_submul (rhs, d, lhs); /* 1 - 39081 x^2 y^2 */
+      mpz_add (lhs, x2, lhs);	/* x^2 + y^2 */
+
+      mpz_clear (d);
+      mpz_clear (x2);
+    }
+  else
+    {
+      /* Check y^2 = x^3 - 3 x + b */
+      mpz_mul (rhs, x, x);
+      mpz_sub_ui (rhs, rhs, 3);
+      mpz_mul (rhs, rhs, x);
+      mpz_add (rhs, rhs, mpz_roinit_n (t, pub->ecc->b, size));
+    }
+  res = mpz_congruent_p (lhs, rhs, mpz_roinit_n (t, pub->ecc->p.m, size));
+
+  mpz_clear (lhs);
+  mpz_clear (rhs);
+
+  return res;
+}
+
 static int
 test_mpn (const char *ref, const mp_limb_t *xp, mp_size_t n)
 {