stdlib: Add arc4random tests

The basic tst-arc4random-chacha20.c checks if the output of ChaCha20
implementation matches the reference test vectors from RFC8439.

The tst-arc4random-fork.c check if subprocesses generate distinct
streams of randomness (if fork handling is done correctly).

The tst-arc4random-stats.c is a statistical test to the randomness of
arc4random, arc4random_buf, and arc4random_uniform.

The tst-arc4random-thread.c check if threads generate distinct streams
of randomness (if function are thread-safe).

Checked on x86_64-linux-gnu, aarch64-linux, and powerpc64le-linux-gnu.

Co-authored-by: Florian Weimer <fweimer@redhat.com>

Checked on x86_64-linux-gnu and aarch64-linux-gnu.

1 files changed, 198 insertions, 0 deletions

diff --git a/stdlib/tst-arc4random-fork.c b/stdlib/tst-arc4random-fork.c
new file mode 100644
index 0000000000..019c0a99de
--- /dev/null
+++ b/stdlib/tst-arc4random-fork.c
@@ -0,0 +1,198 @@
+/* Test that subprocesses generate distinct streams of randomness.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* Collect random data from subprocesses and check that all the
+   results are unique.  */
+
+#include <array_length.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xthread.h>
+#include <support/xunistd.h>
+#include <unistd.h>
+
+/* Perform multiple runs.  The subsequent runs start with an
+   already-initialized random number generator.  (The number 1500 was
+   seen to reproduce failures reliable in case of a race condition in
+   the fork detection code.)  */
+enum { runs = 1500 };
+
+/* One hundred processes in total.  This should be high enough to
+   expose any issues, but low enough not to tax the overall system too
+   much.  */
+enum { subprocesses = 49 };
+
+/* The total number of processes.  */
+enum { processes = subprocesses + 1 };
+
+/* Number of bytes of randomness to generate per process.  Large
+   enough to make false positive duplicates extremely unlikely.  */
+enum { random_size = 16 };
+
+/* Generated bytes of randomness.  */
+struct result
+{
+  unsigned char bytes[random_size];
+};
+
+/* Shared across all processes.  */
+static struct shared_data
+{
+  pthread_barrier_t barrier;
+  struct result results[runs][processes];
+} *shared_data;
+
+static void
+generate_arc4random (unsigned char *bytes)
+{
+  for (int i = 0; i < random_size / sizeof (uint32_t); i++)
+    {
+      uint32_t x = arc4random ();
+      memcpy (&bytes[4 * i], &x, sizeof x);
+    }
+}
+
+static void
+generate_arc4random_buf (unsigned char *bytes)
+{
+  arc4random_buf (bytes, random_size);
+}
+
+static void
+generate_arc4random_uniform (unsigned char *bytes)
+{
+  for (int i = 0; i < random_size; i++)
+    bytes[i] = arc4random_uniform (256);
+}
+
+/* Invoked to collect data from a subprocess.  */
+static void
+subprocess (int run, int process_index, void (*func)(unsigned char *))
+{
+  xpthread_barrier_wait (&shared_data->barrier);
+  func (shared_data->results[run][process_index].bytes);
+}
+
+/* Used to sort the results.  */
+struct index
+{
+  int run;
+  int process_index;
+};
+
+/* Used to sort an array of struct index values.  */
+static int
+index_compare (const void *left1, const void *right1)
+{
+  const struct index *left = left1;
+  const struct index *right = right1;
+
+  return memcmp (shared_data->results[left->run][left->process_index].bytes,
+                 shared_data->results[right->run][right->process_index].bytes,
+                 random_size);
+}
+
+static int
+do_test_func (void (*func)(unsigned char *bytes))
+{
+  /* Collect random data.  */
+  for (int run = 0; run < runs; ++run)
+    {
+      pid_t pids[subprocesses];
+      for (int process_index = 0; process_index < subprocesses;
+           ++process_index)
+        {
+          pids[process_index] = xfork ();
+          if (pids[process_index] == 0)
+            {
+              subprocess (run, process_index, func);
+              _exit (0);
+            }
+        }
+
+      /* Trigger all subprocesses.  Also add data from the parent
+         process.  */
+      subprocess (run, subprocesses, func);
+
+      for (int process_index = 0; process_index < subprocesses;
+           ++process_index)
+        {
+          int status;
+          xwaitpid (pids[process_index], &status, 0);
+          if (status != 0)
+            FAIL_EXIT1 ("subprocess index %d (PID %d) exit status %d\n",
+                        process_index, (int) pids[process_index], status);
+        }
+    }
+
+  /* Check for duplicates.  */
+  struct index indexes[runs * processes];
+  for (int run = 0; run < runs; ++run)
+    for (int process_index = 0; process_index < processes; ++process_index)
+      indexes[run * processes + process_index]
+        = (struct index) { .run = run, .process_index = process_index };
+  qsort (indexes, array_length (indexes), sizeof (indexes[0]), index_compare);
+  for (size_t i = 1; i < array_length (indexes); ++i)
+    {
+      if (index_compare (indexes + i - 1, indexes + i) == 0)
+        {
+          support_record_failure ();
+          unsigned char *bytes
+            = shared_data->results[indexes[i].run]
+                [indexes[i].process_index].bytes;
+          char *quoted = support_quote_blob (bytes, random_size);
+          printf ("error: duplicate randomness data: \"%s\"\n"
+                  "  run %d, subprocess %d\n"
+                  "  run %d, subprocess %d\n",
+                  quoted, indexes[i - 1].run, indexes[i - 1].process_index,
+                  indexes[i].run, indexes[i].process_index);
+          free (quoted);
+        }
+    }
+
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  shared_data = support_shared_allocate (sizeof (*shared_data));
+  {
+    pthread_barrierattr_t attr;
+    xpthread_barrierattr_init (&attr);
+    xpthread_barrierattr_setpshared (&attr, PTHREAD_PROCESS_SHARED);
+    xpthread_barrier_init (&shared_data->barrier, &attr, processes);
+    xpthread_barrierattr_destroy (&attr);
+  }
+
+  do_test_func (generate_arc4random);
+  do_test_func (generate_arc4random_buf);
+  do_test_func (generate_arc4random_uniform);
+
+  xpthread_barrier_destroy (&shared_data->barrier);
+  support_shared_free (shared_data);
+  shared_data = NULL;
+
+  return 0;
+}
+
+#define TIMEOUT 40
+#include <support/test-driver.c>