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: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/9463)

test/build.info

@@ -22,7 +22,7 @@ IF[{- !$disabled{tests} -}]
           testutil/format_output.c testutil/tap_bio.c \
           testutil/test_cleanup.c testutil/main.c testutil/init.c \
           testutil/options.c testutil/test_options.c \
-          testutil/apps_mem.c $LIBAPPSSRC
+          testutil/apps_mem.c testutil/random.c $LIBAPPSSRC
   INCLUDE[libtestutil.a]=../include ../apps/include ..
   DEPEND[libtestutil.a]=../libcrypto
 

test/testutil.h

@@ -537,4 +537,12 @@ 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

@@ -114,7 +114,7 @@ static void set_seed(int s)
         seed = (int)time(NULL);
     test_printf_stdout("%*s# RAND SEED %d\n", subtest_level(), "", seed);
     test_flush_stdout();
-    srand(seed);
+    test_random_seed(seed);
 }
 
 
@@ -326,7 +326,7 @@ 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;
@@ -373,7 +373,7 @@ 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

@@ -0,0 +1,40 @@
+/*
+ * 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();
+}