[apple/network_cmds.git] / unbound / compat / getentropy_linux.c

/*	$OpenBSD: getentropy_linux.c,v 1.20 2014/07/12 15:43:49 beck Exp $	*/

/*
 * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
 * Copyright (c) 2014 Bob Beck <beck@obtuse.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include "config.h"

/*
#define	_POSIX_C_SOURCE 199309L
#define	_GNU_SOURCE     1
*/
#include <sys/types.h>
#include <sys/param.h>
#include <sys/ioctl.h>
#include <sys/resource.h>
#include <sys/syscall.h>
#ifdef HAVE_SYS_SYSCTL_H
#include <sys/sysctl.h>
#endif
#include <sys/statvfs.h>
#include <sys/socket.h>
#include <sys/mount.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <termios.h>
#include <fcntl.h>
#include <signal.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <time.h>
#include <openssl/sha.h>

#include <linux/types.h>
#include <linux/random.h>
#include <linux/sysctl.h>
#ifdef HAVE_GETAUXVAL
#include <sys/auxv.h>
#endif
#include <sys/vfs.h>

#define REPEAT 5
#define min(a, b) (((a) < (b)) ? (a) : (b))

#define HX(a, b) \
	do { \
		if ((a)) \
			HD(errno); \
		else \
			HD(b); \
	} while (0)

#define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
#define HD(x)	 (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
#define HF(x)    (SHA512_Update(&ctx, (char *)&(x), sizeof (void*)))

int	getentropy(void *buf, size_t len);

#ifdef CAN_REFERENCE_MAIN
extern int main(int, char *argv[]);
#endif
static int gotdata(char *buf, size_t len);
static int getentropy_urandom(void *buf, size_t len);
#ifdef SYS__sysctl
static int getentropy_sysctl(void *buf, size_t len);
#endif
static int getentropy_fallback(void *buf, size_t len);

int
getentropy(void *buf, size_t len)
{
	int ret = -1;

	if (len > 256) {
		errno = EIO;
		return -1;
	}

	/*
	 * Try to get entropy with /dev/urandom
	 *
	 * This can fail if the process is inside a chroot or if file
	 * descriptors are exhausted.
	 */
	ret = getentropy_urandom(buf, len);
	if (ret != -1)
		return (ret);

#ifdef SYS__sysctl
	/*
	 * Try to use sysctl CTL_KERN, KERN_RANDOM, RANDOM_UUID.
	 * sysctl is a failsafe API, so it guarantees a result.  This
	 * should work inside a chroot, or when file descriptors are
	 * exhuasted.
	 *
	 * However this can fail if the Linux kernel removes support
	 * for sysctl.  Starting in 2007, there have been efforts to
	 * deprecate the sysctl API/ABI, and push callers towards use
	 * of the chroot-unavailable fd-using /proc mechanism --
	 * essentially the same problems as /dev/urandom.
	 *
	 * Numerous setbacks have been encountered in their deprecation
	 * schedule, so as of June 2014 the kernel ABI still exists on
	 * most Linux architectures. The sysctl() stub in libc is missing
	 * on some systems.  There are also reports that some kernels
	 * spew messages to the console.
	 */
	ret = getentropy_sysctl(buf, len);
	if (ret != -1)
		return (ret);
#endif /* SYS__sysctl */

	/*
	 * Entropy collection via /dev/urandom and sysctl have failed.
	 *
	 * No other API exists for collecting entropy.  See the large
	 * comment block above.
	 *
	 * We have very few options:
	 *     - Even syslog_r is unsafe to call at this low level, so
	 *	 there is no way to alert the user or program.
	 *     - Cannot call abort() because some systems have unsafe
	 *	 corefiles.
	 *     - Could raise(SIGKILL) resulting in silent program termination.
	 *     - Return EIO, to hint that arc4random's stir function
	 *       should raise(SIGKILL)
	 *     - Do the best under the circumstances....
	 *
	 * This code path exists to bring light to the issue that Linux
	 * does not provide a failsafe API for entropy collection.
	 *
	 * We hope this demonstrates that Linux should either retain their
	 * sysctl ABI, or consider providing a new failsafe API which
	 * works in a chroot or when file descriptors are exhausted.
	 */
#undef FAIL_INSTEAD_OF_TRYING_FALLBACK
#ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
	raise(SIGKILL);
#endif
	ret = getentropy_fallback(buf, len);
	if (ret != -1)
		return (ret);

	errno = EIO;
	return (ret);
}

/*
 * Basic sanity checking; wish we could do better.
 */
static int
gotdata(char *buf, size_t len)
{
	char	any_set = 0;
	size_t	i;

	for (i = 0; i < len; ++i)
		any_set |= buf[i];
	if (any_set == 0)
		return -1;
	return 0;
}

static int
getentropy_urandom(void *buf, size_t len)
{
	struct stat st;
	size_t i;
	int fd, cnt, flags;
	int save_errno = errno;

start:

	flags = O_RDONLY;
#ifdef O_NOFOLLOW
	flags |= O_NOFOLLOW;
#endif
#ifdef O_CLOEXEC
	flags |= O_CLOEXEC;
#endif
	fd = open("/dev/urandom", flags, 0);
	if (fd == -1) {
		if (errno == EINTR)
			goto start;
		goto nodevrandom;
	}
#ifndef O_CLOEXEC
	fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
#endif

	/* Lightly verify that the device node looks sane */
	if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode)) {
		close(fd);
		goto nodevrandom;
	}
	if (ioctl(fd, RNDGETENTCNT, &cnt) == -1) {
		close(fd);
		goto nodevrandom;
	}
	for (i = 0; i < len; ) {
		size_t wanted = len - i;
		ssize_t ret = read(fd, (char*)buf + i, wanted);

		if (ret == -1) {
			if (errno == EAGAIN || errno == EINTR)
				continue;
			close(fd);
			goto nodevrandom;
		}
		i += ret;
	}
	close(fd);
	if (gotdata(buf, len) == 0) {
		errno = save_errno;
		return 0;		/* satisfied */
	}
nodevrandom:
	errno = EIO;
	return -1;
}

#ifdef SYS__sysctl
static int
getentropy_sysctl(void *buf, size_t len)
{
	static int mib[] = { CTL_KERN, KERN_RANDOM, RANDOM_UUID };
	size_t i;
	int save_errno = errno;

	for (i = 0; i < len; ) {
		size_t chunk = min(len - i, 16);

		/* SYS__sysctl because some systems already removed sysctl() */
		struct __sysctl_args args = {
			.name = mib,
			.nlen = 3,
			.oldval = buf + i,
			.oldlenp = &chunk,
		};
		if (syscall(SYS__sysctl, &args) != 0)
			goto sysctlfailed;
		i += chunk;
	}
	if (gotdata(buf, len) == 0) {
		errno = save_errno;
		return (0);			/* satisfied */
	}
sysctlfailed:
	errno = EIO;
	return -1;
}
#endif /* SYS__sysctl */

static int cl[] = {
	CLOCK_REALTIME,
#ifdef CLOCK_MONOTONIC
	CLOCK_MONOTONIC,
#endif
#ifdef CLOCK_MONOTONIC_RAW
	CLOCK_MONOTONIC_RAW,
#endif
#ifdef CLOCK_TAI
	CLOCK_TAI,
#endif
#ifdef CLOCK_VIRTUAL
	CLOCK_VIRTUAL,
#endif
#ifdef CLOCK_UPTIME
	CLOCK_UPTIME,
#endif
#ifdef CLOCK_PROCESS_CPUTIME_ID
	CLOCK_PROCESS_CPUTIME_ID,
#endif
#ifdef CLOCK_THREAD_CPUTIME_ID
	CLOCK_THREAD_CPUTIME_ID,
#endif
};

static int
getentropy_fallback(void *buf, size_t len)
{
	uint8_t results[SHA512_DIGEST_LENGTH];
	int save_errno = errno, e, pgs = getpagesize(), faster = 0, repeat;
	static int cnt;
	struct timespec ts;
	struct timeval tv;
	struct rusage ru;
	sigset_t sigset;
	struct stat st;
	SHA512_CTX ctx;
	static pid_t lastpid;
	pid_t pid;
	size_t i, ii, m;
	char *p;

	pid = getpid();
	if (lastpid == pid) {
		faster = 1;
		repeat = 2;
	} else {
		faster = 0;
		lastpid = pid;
		repeat = REPEAT;
	}
	for (i = 0; i < len; ) {
		int j;
		SHA512_Init(&ctx);
		for (j = 0; j < repeat; j++) {
			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
			if (e != -1) {
				cnt += (int)tv.tv_sec;
				cnt += (int)tv.tv_usec;
			}

			for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
				HX(clock_gettime(cl[ii], &ts) == -1, ts);

			HX((pid = getpid()) == -1, pid);
			HX((pid = getsid(pid)) == -1, pid);
			HX((pid = getppid()) == -1, pid);
			HX((pid = getpgid(0)) == -1, pid);
			HX((e = getpriority(0, 0)) == -1, e);

			if (!faster) {
				ts.tv_sec = 0;
				ts.tv_nsec = 1;
				(void) nanosleep(&ts, NULL);
			}

			HX(sigpending(&sigset) == -1, sigset);
			HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
			    sigset);

#ifdef CAN_REFERENCE_MAIN
			HF(main);		/* an addr in program */
#endif
			HF(getentropy);	/* an addr in this library */
			HF(printf);		/* an addr in libc */
			p = (char *)&p;
			HD(p);		/* an addr on stack */
			p = (char *)&errno;
			HD(p);		/* the addr of errno */

			if (i == 0) {
				struct sockaddr_storage ss;
				struct statvfs stvfs;
				struct termios tios;
				struct statfs stfs;
				socklen_t ssl;
				off_t off;

				/*
				 * Prime-sized mappings encourage fragmentation;
				 * thus exposing some address entropy.
				 */
				struct mm {
					size_t	npg;
					void	*p;
				} mm[] =	 {
					{ 17, MAP_FAILED }, { 3, MAP_FAILED },
					{ 11, MAP_FAILED }, { 2, MAP_FAILED },
					{ 5, MAP_FAILED }, { 3, MAP_FAILED },
					{ 7, MAP_FAILED }, { 1, MAP_FAILED },
					{ 57, MAP_FAILED }, { 3, MAP_FAILED },
					{ 131, MAP_FAILED }, { 1, MAP_FAILED },
				};

				for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
					HX(mm[m].p = mmap(NULL,
					    mm[m].npg * pgs,
					    PROT_READ|PROT_WRITE,
					    MAP_PRIVATE|MAP_ANON, -1,
					    (off_t)0), mm[m].p);
					if (mm[m].p != MAP_FAILED) {
						size_t mo;

						/* Touch some memory... */
						p = mm[m].p;
						mo = cnt %
						    (mm[m].npg * pgs - 1);
						p[mo] = 1;
						cnt += (int)((long)(mm[m].p)
						    / pgs);
					}

					/* Check cnts and times... */
					for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
					    ii++) {
						HX((e = clock_gettime(cl[ii],
						    &ts)) == -1, ts);
						if (e != -1)
							cnt += (int)ts.tv_nsec;
					}

					HX((e = getrusage(RUSAGE_SELF,
					    &ru)) == -1, ru);
					if (e != -1) {
						cnt += (int)ru.ru_utime.tv_sec;
						cnt += (int)ru.ru_utime.tv_usec;
					}
				}

				for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
					if (mm[m].p != MAP_FAILED)
						munmap(mm[m].p, mm[m].npg * pgs);
					mm[m].p = MAP_FAILED;
				}

				HX(stat(".", &st) == -1, st);
				HX(statvfs(".", &stvfs) == -1, stvfs);
				HX(statfs(".", &stfs) == -1, stfs);

				HX(stat("/", &st) == -1, st);
				HX(statvfs("/", &stvfs) == -1, stvfs);
				HX(statfs("/", &stfs) == -1, stfs);

				HX((e = fstat(0, &st)) == -1, st);
				if (e == -1) {
					if (S_ISREG(st.st_mode) ||
					    S_ISFIFO(st.st_mode) ||
					    S_ISSOCK(st.st_mode)) {
						HX(fstatvfs(0, &stvfs) == -1,
						    stvfs);
						HX(fstatfs(0, &stfs) == -1,
						    stfs);
						HX((off = lseek(0, (off_t)0,
						    SEEK_CUR)) < 0, off);
					}
					if (S_ISCHR(st.st_mode)) {
						HX(tcgetattr(0, &tios) == -1,
						    tios);
					} else if (S_ISSOCK(st.st_mode)) {
						memset(&ss, 0, sizeof ss);
						ssl = sizeof(ss);
						HX(getpeername(0,
						    (void *)&ss, &ssl) == -1,
						    ss);
					}
				}

				HX((e = getrusage(RUSAGE_CHILDREN,
				    &ru)) == -1, ru);
				if (e != -1) {
					cnt += (int)ru.ru_utime.tv_sec;
					cnt += (int)ru.ru_utime.tv_usec;
				}
			} else {
				/* Subsequent hashes absorb previous result */
				HD(results);
			}

			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
			if (e != -1) {
				cnt += (int)tv.tv_sec;
				cnt += (int)tv.tv_usec;
			}

			HD(cnt);
		}
#ifdef AT_RANDOM
		/* Not as random as you think but we take what we are given */
		p = (char *) getauxval(AT_RANDOM);
		if (p)
			HR(p, 16);
#endif
#ifdef AT_SYSINFO_EHDR
		p = (char *) getauxval(AT_SYSINFO_EHDR);
		if (p)
			HR(p, pgs);
#endif
#ifdef AT_BASE
		p = (char *) getauxval(AT_BASE);
		if (p)
			HD(p);
#endif

		SHA512_Final(results, &ctx);
		memcpy((char*)buf + i, results, min(sizeof(results), len - i));
		i += min(sizeof(results), len - i);
	}
	memset(results, 0, sizeof results);
	if (gotdata(buf, len) == 0) {
		errno = save_errno;
		return 0;		/* satisfied */
	}
	errno = EIO;
	return -1;
}
Commit	Line	Data
89c4ed63 A	1	/* $OpenBSD: getentropy_linux.c,v 1.20 2014/07/12 15:43:49 beck Exp $ */
	2
	3	/*
	4	* Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
	5	* Copyright (c) 2014 Bob Beck <beck@obtuse.com>
	6	*
	7	* Permission to use, copy, modify, and distribute this software for any
	8	* purpose with or without fee is hereby granted, provided that the above
	9	* copyright notice and this permission notice appear in all copies.
	10	*
	11	* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	12	* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	13	* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	14	* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	15	* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	16	* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
	17	* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
	18	*/
	19	#include "config.h"
	20
	21	/*
	22	#define _POSIX_C_SOURCE 199309L
	23	#define _GNU_SOURCE 1
	24	*/
	25	#include <sys/types.h>
	26	#include <sys/param.h>
	27	#include <sys/ioctl.h>
	28	#include <sys/resource.h>
	29	#include <sys/syscall.h>
	30	#ifdef HAVE_SYS_SYSCTL_H
	31	#include <sys/sysctl.h>
	32	#endif
	33	#include <sys/statvfs.h>
	34	#include <sys/socket.h>
	35	#include <sys/mount.h>
	36	#include <sys/mman.h>
	37	#include <sys/stat.h>
	38	#include <sys/time.h>
	39	#include <stdlib.h>
	40	#include <stdint.h>
	41	#include <stdio.h>
	42	#include <termios.h>
	43	#include <fcntl.h>
	44	#include <signal.h>
	45	#include <string.h>
	46	#include <errno.h>
	47	#include <unistd.h>
	48	#include <time.h>
	49	#include <openssl/sha.h>
	50
	51	#include <linux/types.h>
	52	#include <linux/random.h>
	53	#include <linux/sysctl.h>
	54	#ifdef HAVE_GETAUXVAL
	55	#include <sys/auxv.h>
	56	#endif
	57	#include <sys/vfs.h>
	58
	59	#define REPEAT 5
	60	#define min(a, b) (((a) < (b)) ? (a) : (b))
	61
	62	#define HX(a, b) \
	63	do { \
	64	if ((a)) \
65	HD(errno); \
66	else \
67	HD(b); \
68	} while (0)
69
70	#define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
71	#define HD(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
72	#define HF(x) (SHA512_Update(&ctx, (char )&(x), sizeof (void)))
73
74	int getentropy(void *buf, size_t len);
75
76	#ifdef CAN_REFERENCE_MAIN
77	extern int main(int, char *argv[]);
78	#endif
79	static int gotdata(char *buf, size_t len);
80	static int getentropy_urandom(void *buf, size_t len);
81	#ifdef SYS__sysctl
82	static int getentropy_sysctl(void *buf, size_t len);
83	#endif
84	static int getentropy_fallback(void *buf, size_t len);
85
86	int
87	getentropy(void *buf, size_t len)
88	{
89	int ret = -1;
90
91	if (len > 256) {
92	errno = EIO;
93	return -1;
94	}
95
96	/*
97	* Try to get entropy with /dev/urandom
98	*
99	* This can fail if the process is inside a chroot or if file
100	* descriptors are exhausted.
101	*/
102	ret = getentropy_urandom(buf, len);
103	if (ret != -1)
104	return (ret);
105
106	#ifdef SYS__sysctl
107	/*
108	* Try to use sysctl CTL_KERN, KERN_RANDOM, RANDOM_UUID.
109	* sysctl is a failsafe API, so it guarantees a result. This
110	* should work inside a chroot, or when file descriptors are
111	* exhuasted.
112	*
113	* However this can fail if the Linux kernel removes support
114	* for sysctl. Starting in 2007, there have been efforts to
115	* deprecate the sysctl API/ABI, and push callers towards use
116	* of the chroot-unavailable fd-using /proc mechanism --
117	* essentially the same problems as /dev/urandom.
118	*
119	* Numerous setbacks have been encountered in their deprecation
120	* schedule, so as of June 2014 the kernel ABI still exists on
121	* most Linux architectures. The sysctl() stub in libc is missing
122	* on some systems. There are also reports that some kernels
123	* spew messages to the console.
124	*/
125	ret = getentropy_sysctl(buf, len);
126	if (ret != -1)
127	return (ret);
128	#endif /* SYS__sysctl */
129
130	/*
131	* Entropy collection via /dev/urandom and sysctl have failed.
132	*
133	* No other API exists for collecting entropy. See the large
134	* comment block above.
135	*
136	* We have very few options:
137	* - Even syslog_r is unsafe to call at this low level, so
138	* there is no way to alert the user or program.
139	* - Cannot call abort() because some systems have unsafe
140	* corefiles.
141	* - Could raise(SIGKILL) resulting in silent program termination.
142	* - Return EIO, to hint that arc4random's stir function
143	* should raise(SIGKILL)
144	* - Do the best under the circumstances....
145	*
146	* This code path exists to bring light to the issue that Linux
147	* does not provide a failsafe API for entropy collection.
148	*
149	* We hope this demonstrates that Linux should either retain their
150	* sysctl ABI, or consider providing a new failsafe API which
151	* works in a chroot or when file descriptors are exhausted.
152	*/
153	#undef FAIL_INSTEAD_OF_TRYING_FALLBACK
154	#ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
155	raise(SIGKILL);
156	#endif
157	ret = getentropy_fallback(buf, len);
158	if (ret != -1)
159	return (ret);
160
161	errno = EIO;
162	return (ret);
163	}
164
165	/*
166	* Basic sanity checking; wish we could do better.
167	*/
168	static int
169	gotdata(char *buf, size_t len)
170	{
171	char any_set = 0;
172	size_t i;
173
174	for (i = 0; i < len; ++i)
175	any_set \|= buf[i];
176	if (any_set == 0)
177	return -1;
178	return 0;
179	}
180
181	static int
182	getentropy_urandom(void *buf, size_t len)
183	{
184	struct stat st;
185	size_t i;
186	int fd, cnt, flags;
187	int save_errno = errno;
188
189	start:
190
191	flags = O_RDONLY;
192	#ifdef O_NOFOLLOW
193	flags \|= O_NOFOLLOW;
194	#endif
195	#ifdef O_CLOEXEC
196	flags \|= O_CLOEXEC;
197	#endif
198	fd = open("/dev/urandom", flags, 0);
199	if (fd == -1) {
200	if (errno == EINTR)
201	goto start;
202	goto nodevrandom;
203	}
204	#ifndef O_CLOEXEC
205	fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) \| FD_CLOEXEC);
206	#endif
207
208	/* Lightly verify that the device node looks sane */
209	if (fstat(fd, &st) == -1 \|\| !S_ISCHR(st.st_mode)) {
210	close(fd);
211	goto nodevrandom;
212	}
213	if (ioctl(fd, RNDGETENTCNT, &cnt) == -1) {
214	close(fd);
215	goto nodevrandom;
216	}
217	for (i = 0; i < len; ) {
218	size_t wanted = len - i;
219	ssize_t ret = read(fd, (char*)buf + i, wanted);
220
221	if (ret == -1) {
222	if (errno == EAGAIN \|\| errno == EINTR)
223	continue;
224	close(fd);
225	goto nodevrandom;
226	}
227	i += ret;
228	}
229	close(fd);
230	if (gotdata(buf, len) == 0) {
231	errno = save_errno;
232	return 0; /* satisfied */
233	}
234	nodevrandom:
235	errno = EIO;
236	return -1;
237	}
238
239	#ifdef SYS__sysctl
240	static int
241	getentropy_sysctl(void *buf, size_t len)
242	{
243	static int mib[] = { CTL_KERN, KERN_RANDOM, RANDOM_UUID };
244	size_t i;
245	int save_errno = errno;
246
247	for (i = 0; i < len; ) {
248	size_t chunk = min(len - i, 16);
249
250	/* SYS__sysctl because some systems already removed sysctl() */
251	struct __sysctl_args args = {
252	.name = mib,
253	.nlen = 3,
254	.oldval = buf + i,
255	.oldlenp = &chunk,
256	};
257	if (syscall(SYS__sysctl, &args) != 0)
258	goto sysctlfailed;
259	i += chunk;
260	}
261	if (gotdata(buf, len) == 0) {
262	errno = save_errno;
263	return (0); /* satisfied */
264	}
265	sysctlfailed:
266	errno = EIO;
267	return -1;
268	}
269	#endif /* SYS__sysctl */
270
271	static int cl[] = {
272	CLOCK_REALTIME,
273	#ifdef CLOCK_MONOTONIC
274	CLOCK_MONOTONIC,
275	#endif
276	#ifdef CLOCK_MONOTONIC_RAW
277	CLOCK_MONOTONIC_RAW,
278	#endif
279	#ifdef CLOCK_TAI
280	CLOCK_TAI,
281	#endif
282	#ifdef CLOCK_VIRTUAL
283	CLOCK_VIRTUAL,
284	#endif
285	#ifdef CLOCK_UPTIME
286	CLOCK_UPTIME,
287	#endif
288	#ifdef CLOCK_PROCESS_CPUTIME_ID
289	CLOCK_PROCESS_CPUTIME_ID,
290	#endif
291	#ifdef CLOCK_THREAD_CPUTIME_ID
292	CLOCK_THREAD_CPUTIME_ID,
293	#endif
294	};
295
296	static int
297	getentropy_fallback(void *buf, size_t len)
298	{
299	uint8_t results[SHA512_DIGEST_LENGTH];
300	int save_errno = errno, e, pgs = getpagesize(), faster = 0, repeat;
301	static int cnt;
302	struct timespec ts;
303	struct timeval tv;
304	struct rusage ru;
305	sigset_t sigset;
306	struct stat st;
307	SHA512_CTX ctx;
308	static pid_t lastpid;
309	pid_t pid;
310	size_t i, ii, m;
311	char *p;
312
313	pid = getpid();
314	if (lastpid == pid) {
315	faster = 1;
316	repeat = 2;
317	} else {
318	faster = 0;
319	lastpid = pid;
320	repeat = REPEAT;
321	}
322	for (i = 0; i < len; ) {
323	int j;
324	SHA512_Init(&ctx);
325	for (j = 0; j < repeat; j++) {
326	HX((e = gettimeofday(&tv, NULL)) == -1, tv);
327	if (e != -1) {
328	cnt += (int)tv.tv_sec;
329	cnt += (int)tv.tv_usec;
330	}
331
332	for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
333	HX(clock_gettime(cl[ii], &ts) == -1, ts);
334
335	HX((pid = getpid()) == -1, pid);
336	HX((pid = getsid(pid)) == -1, pid);
337	HX((pid = getppid()) == -1, pid);
338	HX((pid = getpgid(0)) == -1, pid);
339	HX((e = getpriority(0, 0)) == -1, e);
340
341	if (!faster) {
342	ts.tv_sec = 0;
343	ts.tv_nsec = 1;
344	(void) nanosleep(&ts, NULL);
345	}
346
347	HX(sigpending(&sigset) == -1, sigset);
348	HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
349	sigset);
350
351	#ifdef CAN_REFERENCE_MAIN
352	HF(main); /* an addr in program */
353	#endif
354	HF(getentropy); /* an addr in this library */
355	HF(printf); /* an addr in libc */
356	p = (char *)&p;
357	HD(p); /* an addr on stack */
358	p = (char *)&errno;
359	HD(p); /* the addr of errno */
360
361	if (i == 0) {
362	struct sockaddr_storage ss;
363	struct statvfs stvfs;
364	struct termios tios;
365	struct statfs stfs;
366	socklen_t ssl;
367	off_t off;
368
369	/*
370	* Prime-sized mappings encourage fragmentation;
371	* thus exposing some address entropy.
372	*/
373	struct mm {
374	size_t npg;
375	void *p;
376	} mm[] = {
377	{ 17, MAP_FAILED }, { 3, MAP_FAILED },
378	{ 11, MAP_FAILED }, { 2, MAP_FAILED },
379	{ 5, MAP_FAILED }, { 3, MAP_FAILED },
380	{ 7, MAP_FAILED }, { 1, MAP_FAILED },
381	{ 57, MAP_FAILED }, { 3, MAP_FAILED },
382	{ 131, MAP_FAILED }, { 1, MAP_FAILED },
383	};
384
385	for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
386	HX(mm[m].p = mmap(NULL,
387	mm[m].npg * pgs,
388	PROT_READ\|PROT_WRITE,
389	MAP_PRIVATE\|MAP_ANON, -1,
390	(off_t)0), mm[m].p);
391	if (mm[m].p != MAP_FAILED) {
392	size_t mo;
393
394	/* Touch some memory... */
395	p = mm[m].p;
396	mo = cnt %
397	(mm[m].npg * pgs - 1);
398	p[mo] = 1;
399	cnt += (int)((long)(mm[m].p)
400	/ pgs);
401	}
402
403	/* Check cnts and times... */
404	for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
405	ii++) {
406	HX((e = clock_gettime(cl[ii],
407	&ts)) == -1, ts);
408	if (e != -1)
409	cnt += (int)ts.tv_nsec;
410	}
411
412	HX((e = getrusage(RUSAGE_SELF,
413	&ru)) == -1, ru);
414	if (e != -1) {
415	cnt += (int)ru.ru_utime.tv_sec;
416	cnt += (int)ru.ru_utime.tv_usec;
417	}
418	}
419
420	for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
421	if (mm[m].p != MAP_FAILED)
422	munmap(mm[m].p, mm[m].npg * pgs);
423	mm[m].p = MAP_FAILED;
424	}
425
426	HX(stat(".", &st) == -1, st);
427	HX(statvfs(".", &stvfs) == -1, stvfs);
428	HX(statfs(".", &stfs) == -1, stfs);
429
430	HX(stat("/", &st) == -1, st);
431	HX(statvfs("/", &stvfs) == -1, stvfs);
432	HX(statfs("/", &stfs) == -1, stfs);
433
434	HX((e = fstat(0, &st)) == -1, st);
435	if (e == -1) {
436	if (S_ISREG(st.st_mode) \|\|
437	S_ISFIFO(st.st_mode) \|\|
438	S_ISSOCK(st.st_mode)) {
439	HX(fstatvfs(0, &stvfs) == -1,
440	stvfs);
441	HX(fstatfs(0, &stfs) == -1,
442	stfs);
443	HX((off = lseek(0, (off_t)0,
444	SEEK_CUR)) < 0, off);
445	}
446	if (S_ISCHR(st.st_mode)) {
447	HX(tcgetattr(0, &tios) == -1,
448	tios);
449	} else if (S_ISSOCK(st.st_mode)) {
450	memset(&ss, 0, sizeof ss);
451	ssl = sizeof(ss);
452	HX(getpeername(0,
453	(void *)&ss, &ssl) == -1,
454	ss);
455	}
456	}
457
458	HX((e = getrusage(RUSAGE_CHILDREN,
459	&ru)) == -1, ru);
460	if (e != -1) {
461	cnt += (int)ru.ru_utime.tv_sec;
462	cnt += (int)ru.ru_utime.tv_usec;
463	}
464	} else {
465	/* Subsequent hashes absorb previous result */
466	HD(results);
467	}
468
469	HX((e = gettimeofday(&tv, NULL)) == -1, tv);
470	if (e != -1) {
471	cnt += (int)tv.tv_sec;
472	cnt += (int)tv.tv_usec;
473	}
474
475	HD(cnt);
476	}
477	#ifdef AT_RANDOM
478	/* Not as random as you think but we take what we are given */
479	p = (char *) getauxval(AT_RANDOM);
480	if (p)
481	HR(p, 16);
482	#endif
483	#ifdef AT_SYSINFO_EHDR
484	p = (char *) getauxval(AT_SYSINFO_EHDR);
485	if (p)
486	HR(p, pgs);
487	#endif
488	#ifdef AT_BASE
489	p = (char *) getauxval(AT_BASE);
490	if (p)
491	HD(p);
492	#endif
493
494	SHA512_Final(results, &ctx);
495	memcpy((char*)buf + i, results, min(sizeof(results), len - i));
496	i += min(sizeof(results), len - i);
497	}
498	memset(results, 0, sizeof results);
499	if (gotdata(buf, len) == 0) {
500	errno = save_errno;
501	return 0; /* satisfied */
502	}
503	errno = EIO;
504	return -1;
505	}