tests/random/arc4random_fork.c

/*
 * This file and its contents are supplied under the terms of the
 * Common Development and Distribution License ("CDDL"), version 1.0.
 * You may only use this file in accordance with the terms of version
 * 1.0 of the CDDL.
 *
 * A full copy of the text of the CDDL should have accompanied this
 * source.  A copy of the CDDL is also available via the Internet at
 * http://www.illumos.org/license/CDDL.
 */

/*
 * Copyright (c) 2015, Joyent, Inc.
 */

/*
 * Tests to make sure that a parent and child do not get the same arc4random
 * state across a fork. This source file is used to make two tests. One which
 * initializes the data in advance, one of which does not.
 */

#include <stdlib.h>
#include <sys/mman.h>
#include <assert.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>

typedef struct arc4_fork {
    uint32_t    af_parent;
    uint32_t    af_child;
    uint8_t     af_pbuf[4096];
    uint8_t     af_cbuf[4096];
} arc4_fork_t;

arc4_fork_t *fork_data;

int
main(void)
{
    int e, i;
    pid_t p, child;

#ifdef  ARC4_PREINIT
    (void) arc4random();
#endif

    fork_data = (arc4_fork_t *)mmap(NULL, sizeof (arc4_fork_t),
        PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
    assert(fork_data != MAP_FAILED);

    p = fork();
    assert(p != -1);
    if (p == 0) {
        fork_data->af_child = arc4random();
        arc4random_buf(fork_data->af_cbuf, sizeof (fork_data->af_cbuf));
        exit(0);
    }

    fork_data->af_parent = arc4random();
    arc4random_buf(fork_data->af_pbuf, sizeof (fork_data->af_pbuf));
    do {
        child = wait(&e);
    } while (child == -1 && errno == EINTR);
    assert(child == p);

    /* Now verify our data doesn't match */
    assert(fork_data->af_parent != fork_data->af_child);

    /*
     * For the buffer here, we're mostly concerned that they aren't somehow
     * getting the same stream.
     */
    for (i = 0; i < sizeof (fork_data->af_pbuf); i++) {
        if (fork_data->af_pbuf[i] != fork_data->af_cbuf[i])
            break;
    }
    assert(i != sizeof (fork_data->af_pbuf));

    return (0);
}