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/* Test that subprocesses generate distinct streams of randomness.
Copyright (C) 2022-2025 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. */
enum { runs = 10 };
/* Total number of spawned processes on each run. */
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>
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