1  /*-
  2   * Copyright (c) 2011 David Schultz
  3   * All rights reserved.
  4   *
  5   * Redistribution and use in source and binary forms, with or without
  6   * modification, are permitted provided that the following conditions
  7   * are met:
  8   * 1. Redistributions of source code must retain the above copyright
  9   *    notice, this list of conditions and the following disclaimer.
 10   * 2. Redistributions in binary form must reproduce the above copyright
 11   *    notice, this list of conditions and the following disclaimer in the
 12   *    documentation and/or other materials provided with the distribution.
 13   *
 14   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 15   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 16   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 17   * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 18   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 19   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 20   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 21   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 22   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 23   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 24   * SUCH DAMAGE.
 25   */
 26  
 27  #include <stdio.h>
 28  #include <stdlib.h>
 29  #include <stdint.h>
 30  #include <string.h>
 31  #include <math.h>
 32  #include <unistd.h>
 33  #include <pthread.h>
 34  #include <sys/cdefs.h>
 35  #include <sys/types.h>
 36  #include <sys/mman.h>
 37  #include <sys/wait.h>
 38  
 39  #include <darwintest.h>
 40  #include <darwintest_utils.h>
 41  
 42  #define LEN (1024 * 32)
 43  static void * stress(void *ptr __unused)
 44  {
 45  	uint32_t value;
 46  	uint8_t buf[LEN + 1];
 47  	buf[LEN] = 0;
 48  	for (int i = 0; i < LEN; i++){
 49  		value = arc4random();
 50  		if (value % 100 == 0)
 51  			arc4random_stir();
 52  		if ((value & 0x70) == 0)
 53  			arc4random_uniform(value);
 54  		if ((value & 0x7) == 0)
 55  			arc4random_buf(buf, (size_t)i);
 56  	}
 57  	T_ASSERT_EQ(buf[LEN], 0, NULL);
 58  
 59  	return NULL;
 60  }
 61  
 62  T_DECL(arc4random_stress, "arc4random() stress")
 63  {
 64  	const int ncpu = dt_ncpu();
 65  
 66  	pthread_t thr[ncpu];
 67  	for (int i = 0; i < ncpu; i++){
 68  		T_ASSERT_POSIX_ZERO(pthread_create(&thr[i], NULL, stress, NULL), NULL);
 69  	}
 70  	for (int i = 0; i < ncpu; i++){
 71  		T_ASSERT_POSIX_ZERO(pthread_join(thr[i], NULL), NULL);
 72  	}
 73  }
 74  
 75  /*
 76   * BUFSIZE is the number of bytes of rc4 output to compare.  The probability
 77   * that this test fails spuriously is 2**(-BUFSIZE * 8).
 78   */
 79  #define	BUFSIZE		8
 80  
 81  T_DECL(arc4random_fork, "arc4random() shouldn't return the same sequence in child post-fork()")
 82  {
 83  	struct shared_page {
 84  		char parentbuf[BUFSIZE];
 85  		char childbuf[BUFSIZE];
 86  	} *page;
 87  	pid_t pid;
 88  	char c;
 89  
 90  	page = mmap(NULL, sizeof(struct shared_page), PROT_READ | PROT_WRITE,
 91  		    MAP_ANON | MAP_SHARED, -1, 0);
 92  	T_ASSERT_NE(page, MAP_FAILED, "mmap()");
 93  
 94  	arc4random_buf(&c, 1);
 95  
 96  	pid = fork();
 97  	if (pid < 0) {
 98  		T_ASSERT_FAIL("fork() failed");
 99  	} else if (pid == 0) {
100  		/* child */
101  		arc4random_buf(page->childbuf, BUFSIZE);
102  		exit(0);
103  	} else {
104  		/* parent */
105  		int status;
106  		arc4random_buf(page->parentbuf, BUFSIZE);
107  		T_ASSERT_EQ(wait(&status), pid, "wait() returns child pid");
108  	}
109  	T_EXPECT_NE(memcmp(page->parentbuf, page->childbuf, BUFSIZE), 0, "sequences are distinct");
110  }
111  
112  #define  ARC4_EXPECTATION ((2u << 31)  - 1)/2
113  #define  ITER 10000000
114  #define  PROB_THRESH sqrt(6*log2(ITER)/(ITER*1.0))
115  /* Simple randomness test using a chernoff bound
116   * If this fails with probability (1 - 2/(ITER)^{4})
117   *  arc4random is NOT a uniform distribution between
118   *  0 and 2**32 - 1. Note that this test does not guarantee
119   *  that arc4random. Is correct, just that it isn't terribly
120   *  wrong.
121   * */
122  T_DECL(arc4random_stats, "ensure arc4random() is random")
123  {
124  	int i;
125  	int total = 0;
126  	for (i = 0; i < ITER; i++) {
127  		total += arc4random() > ARC4_EXPECTATION;
128  	}
129  	double prob = total/(ITER*1.0);
130  	T_EXPECT_LT(fabs(prob - 0.5), PROB_THRESH, "probability is within threshold");
131  }