Add weak platform independent PRNG to test framework.

Implement the GNU C library's random(3) pseudorandom number generator.
The algorithm is described: https://www.mscs.dal.ca/~selinger/random/

The rationale is to make the tests repeatable across differing platforms with
different underlying implementations of the random(3) library call.

More specifically: when executing tests with random ordering.

[extended tests]
Reviewed-by: NBernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/9463)

(cherry picked from commit e9a5932d04f6b7dd25b39a8ff9dc162d64a78c22)

test/build.info

@@ -12,7 +12,8 @@ IF[{- !$disabled{tests} -}]
   SOURCE[libtestutil.a]=testutil/basic_output.c testutil/output_helpers.c \
           testutil/driver.c testutil/tests.c testutil/cb.c testutil/stanza.c \
           testutil/format_output.c testutil/tap_bio.c \
-          testutil/test_cleanup.c testutil/main.c testutil/init.c
+          testutil/test_cleanup.c testutil/main.c testutil/init.c \
+          testutil/random.c
   INCLUDE[libtestutil.a]=../include
   DEPEND[libtestutil.a]=../libcrypto
 

test/testutil.h

@@ -454,4 +454,12 @@ void test_clearstanza(STANZA *s);
  */
 char *glue_strings(const char *list[], size_t *out_len);
 
+/*
+ * Pseudo random number generator of low quality but having repeatability
+ * across platforms.  The two calls are replacements for random(3) and
+ * srandom(3).
+ */
+uint32_t test_random(void);
+void test_random_seed(uint32_t sd);
+
 #endif                          /* HEADER_TESTUTIL_H */

test/testutil/driver.c

@@ -112,7 +112,7 @@ void setup_test_framework()
             seed = (int)time(NULL);
         test_printf_stdout("%*s# RAND SEED %d\n", subtest_level(), "", seed);
         test_flush_stdout();
-        srand(seed);
+        test_random_seed(seed);
     }
 
 #ifndef OPENSSL_NO_CRYPTO_MDEBUG
@@ -190,7 +190,7 @@ int run_tests(const char *test_prog_name)
         permute[i] = i;
     if (seed != 0)
         for (i = num_tests - 1; i >= 1; i--) {
-            j = rand() % (1 + i);
+            j = test_random() % (1 + i);
             ii = permute[j];
             permute[j] = permute[i];
             permute[i] = ii;
@@ -228,7 +228,7 @@ int run_tests(const char *test_prog_name)
                 jstep = 1;
             else
                 do
-                    jstep = rand() % all_tests[i].num;
+                    jstep = test_random() % all_tests[i].num;
                 while (jstep == 0 || gcd(all_tests[i].num, jstep) != 1);
 
             for (jj = 0; jj < all_tests[i].num; jj++) {

test/testutil/random.c

+/*
+ * Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include "../testutil.h"
+
+/*
+ * This is an implementation of the algorithm used by the GNU C library's
+ * random(3) pseudorandom number generator as described:
+ *      https://www.mscs.dal.ca/~selinger/random/
+ */
+static uint32_t test_random_state[31];
+
+uint32_t test_random(void) {
+    static unsigned int pos = 3;
+
+    if (pos == 31)
+        pos = 0;
+    test_random_state[pos] += test_random_state[(pos + 28) % 31];
+    return test_random_state[pos++] / 2;
+}
+
+void test_random_seed(uint32_t sd) {
+    int i;
+    int32_t s;
+    const unsigned int mod = (1u << 31) - 1;
+
+    test_random_state[0] = sd;
+    for (i = 1; i < 31; i++) {
+        s = (int32_t)test_random_state[i - 1];
+        test_random_state[i] = (uint32_t)((16807 * (int64_t)s) % mod);
+    }
+    for (i = 34; i < 344; i++)
+        test_random();
+}