From: Niels Möller <nisse@lysator.liu.se>
Date: Fri, 22 Oct 2021 07:46:03 +0000 (+0200)
Subject: Extend ecc-mod-test, with improved coverage of corner cases.
X-Git-Tag: nettle_3.8_release_20220602~88
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=45028ff232dd90fd2afce6e1550a4ca3b0844612;p=thirdparty%2Fnettle.git

Extend ecc-mod-test, with improved coverage of corner cases.
---

diff --git a/ChangeLog b/ChangeLog
index c3bae072..64d2b311 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2021-10-06  Niels Möller  <nisse@lysator.liu.se>
+
+	* testsuite/ecc-mod-test.c: Extend tests to give better coverage
+	of corner cases, with input close to a multiple of the modulo.
+
 2021-09-21  Niels Möller  <nisse@lysator.liu.se>
 
 	* Makefile.in (nettle.pdf): Generate pdf manual using texi2pdf,
diff --git a/testsuite/ecc-mod-test.c b/testsuite/ecc-mod-test.c
index 8a074c7d..719789c0 100644
--- a/testsuite/ecc-mod-test.c
+++ b/testsuite/ecc-mod-test.c
@@ -122,10 +122,39 @@ test_modulo (gmp_randstate_t rands, const char *name,
 
   for (j = 0; j < count; j++)
     {
-      if (j & 1)
-	mpz_rrandomb (r, rands, 2*m->size * GMP_NUMB_BITS);
+      if (j & 2)
+	{
+	  if (j & 1)
+	    mpz_rrandomb (r, rands, 2*m->size * GMP_NUMB_BITS);
+	  else
+	    mpz_urandomb (r, rands, 2*m->size * GMP_NUMB_BITS);
+	}
       else
-	mpz_urandomb (r, rands, 2*m->size * GMP_NUMB_BITS);
+	{
+	  /* Test inputs close to a multiple of m. */
+	  mpz_t q;
+	  unsigned q_size;
+	  int diff;
+
+	  mpz_urandomb(r, rands, 30);
+	  q_size = 11 + mpz_get_ui(r) % (m->size * GMP_NUMB_BITS - 10);
+	  mpz_urandomb(r, rands, 30);
+	  diff = mpz_get_si(r) % 20 - 10;
+
+	  if (j & 1)
+	    mpz_rrandomb (r, rands, q_size);
+	  else
+	    mpz_urandomb (r, rands, q_size);
+
+	  mpz_mul (r, r, mpz_roinit_n(q, m->m, m->size));
+	  if (diff >= 0)
+	    mpz_add_ui (r, r, diff);
+	  else
+	    mpz_sub_ui (r, r, -diff);
+
+	  if (mpz_sgn(r) < 0)
+	    continue;
+	}
 
       test_one (name, m, r);
     }
@@ -173,9 +202,14 @@ test_patterns (const char *name,
 
   for (j = m->bit_size; j < 2*m->bit_size; j++)
     {
+      /* Single one bit */
       mpz_set_ui (r, 1);
       mpz_mul_2exp (r, r, j);
+      test_one (name, m, r);
 
+      /* All ones. */
+      mpz_mul_2exp (r, r, 1);
+      mpz_sub_ui (r, r, 1);
       test_one (name, m, r);
     }
   mpz_clear (r);