1/*	$OpenBSD: getentropy_solaris.c,v 1.4 2014/07/12 20:41:47 wouter 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#include <sys/types.h>
22#include <sys/param.h>
23#include <sys/ioctl.h>
24#include <sys/resource.h>
25#include <sys/syscall.h>
26#include <sys/statvfs.h>
27#include <sys/socket.h>
28#include <sys/mount.h>
29#include <sys/mman.h>
30#include <sys/stat.h>
31#include <sys/time.h>
32#include <stdlib.h>
33#ifdef HAVE_STDINT_H
34#include <stdint.h>
35#endif
36#include <stdio.h>
37#include <termios.h>
38#include <fcntl.h>
39#include <signal.h>
40#include <string.h>
41#include <errno.h>
42#include <unistd.h>
43#include <time.h>
44#ifdef HAVE_SYS_SHA2_H
45#include <sys/sha2.h>
46#define SHA512_Init SHA512Init
47#define SHA512_Update SHA512Update
48#define SHA512_Final SHA512Final
49#else
50#include <openssl/sha.h>
51#endif
52
53#include <sys/vfs.h>
54#include <sys/statfs.h>
55#include <sys/loadavg.h>
56
57#define REPEAT 5
58#define min(a, b) (((a) < (b)) ? (a) : (b))
59
60#define HX(a, b) \
61	do { \
62		if ((a)) \
63			HD(errno); \
64		else \
65			HD(b); \
66	} while (0)
67
68#define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
69#define HD(x)	 (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
70#define HF(x)	 (SHA512_Update(&ctx, (char *)&(x), sizeof (void*)))
71
72int	getentropy(void *buf, size_t len);
73
74#ifdef CAN_REFERENCE_MAIN
75extern int main(int, char *argv[]);
76#endif
77static int gotdata(char *buf, size_t len);
78static int getentropy_urandom(void *buf, size_t len, const char *path,
79    int devfscheck);
80static int getentropy_fallback(void *buf, size_t len);
81
82int
83getentropy(void *buf, size_t len)
84{
85	int ret = -1;
86
87	if (len > 256) {
88		errno = EIO;
89		return -1;
90	}
91
92	/*
93	 * Try to get entropy with /dev/urandom
94	 *
95	 * Solaris provides /dev/urandom as a symbolic link to
96	 * /devices/pseudo/random@0:urandom which is provided by
97	 * a devfs filesystem.  Best practice is to use O_NOFOLLOW,
98	 * so we must try the unpublished name directly.
99	 *
100	 * This can fail if the process is inside a chroot which lacks
101	 * the devfs mount, or if file descriptors are exhausted.
102	 */
103	ret = getentropy_urandom(buf, len,
104	    "/devices/pseudo/random@0:urandom", 1);
105	if (ret != -1)
106		return (ret);
107
108	/*
109	 * Unfortunately, chroot spaces on Solaris are sometimes setup
110	 * with direct device node of the well-known /dev/urandom name
111	 * (perhaps to avoid dragging all of devfs into the space).
112	 *
113	 * This can fail if the process is inside a chroot or if file
114	 * descriptors are exhausted.
115	 */
116	ret = getentropy_urandom(buf, len, "/dev/urandom", 0);
117	if (ret != -1)
118		return (ret);
119
120	/*
121	 * Entropy collection via /dev/urandom has failed.
122	 *
123	 * No other API exists for collecting entropy, and we have
124	 * no failsafe way to get it on Solaris that is not sensitive
125	 * to resource exhaustion.
126	 *
127	 * We have very few options:
128	 *     - Even syslog_r is unsafe to call at this low level, so
129	 *	 there is no way to alert the user or program.
130	 *     - Cannot call abort() because some systems have unsafe
131	 *	 corefiles.
132	 *     - Could raise(SIGKILL) resulting in silent program termination.
133	 *     - Return EIO, to hint that arc4random's stir function
134	 *       should raise(SIGKILL)
135	 *     - Do the best under the circumstances....
136	 *
137	 * This code path exists to bring light to the issue that Solaris
138	 * does not provide a failsafe API for entropy collection.
139	 *
140	 * We hope this demonstrates that Solaris should consider
141	 * providing a new failsafe API which works in a chroot or
142	 * when file descriptors are exhausted.
143	 */
144#undef FAIL_INSTEAD_OF_TRYING_FALLBACK
145#ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
146	raise(SIGKILL);
147#endif
148	ret = getentropy_fallback(buf, len);
149	if (ret != -1)
150		return (ret);
151
152	errno = EIO;
153	return (ret);
154}
155
156/*
157 * Basic sanity checking; wish we could do better.
158 */
159static int
160gotdata(char *buf, size_t len)
161{
162	char	any_set = 0;
163	size_t	i;
164
165	for (i = 0; i < len; ++i)
166		any_set |= buf[i];
167	if (any_set == 0)
168		return -1;
169	return 0;
170}
171
172static int
173getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck)
174{
175	struct stat st;
176	size_t i;
177	int fd, flags;
178	int save_errno = errno;
179
180start:
181
182	flags = O_RDONLY;
183#ifdef O_NOFOLLOW
184	flags |= O_NOFOLLOW;
185#endif
186#ifdef O_CLOEXEC
187	flags |= O_CLOEXEC;
188#endif
189	fd = open(path, flags, 0);
190	if (fd == -1) {
191		if (errno == EINTR)
192			goto start;
193		goto nodevrandom;
194	}
195#ifndef O_CLOEXEC
196	fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
197#endif
198
199	/* Lightly verify that the device node looks sane */
200	if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode) ||
201	    (devfscheck && (strcmp(st.st_fstype, "devfs") != 0))) {
202		close(fd);
203		goto nodevrandom;
204	}
205	for (i = 0; i < len; ) {
206		size_t wanted = len - i;
207		ssize_t ret = read(fd, (char *)buf + i, wanted);
208
209		if (ret == -1) {
210			if (errno == EAGAIN || errno == EINTR)
211				continue;
212			close(fd);
213			goto nodevrandom;
214		}
215		i += ret;
216	}
217	close(fd);
218	if (gotdata(buf, len) == 0) {
219		errno = save_errno;
220		return 0;		/* satisfied */
221	}
222nodevrandom:
223	errno = EIO;
224	return -1;
225}
226
227static const int cl[] = {
228	CLOCK_REALTIME,
229#ifdef CLOCK_MONOTONIC
230	CLOCK_MONOTONIC,
231#endif
232#ifdef CLOCK_MONOTONIC_RAW
233	CLOCK_MONOTONIC_RAW,
234#endif
235#ifdef CLOCK_TAI
236	CLOCK_TAI,
237#endif
238#ifdef CLOCK_VIRTUAL
239	CLOCK_VIRTUAL,
240#endif
241#ifdef CLOCK_UPTIME
242	CLOCK_UPTIME,
243#endif
244#ifdef CLOCK_PROCESS_CPUTIME_ID
245	CLOCK_PROCESS_CPUTIME_ID,
246#endif
247#ifdef CLOCK_THREAD_CPUTIME_ID
248	CLOCK_THREAD_CPUTIME_ID,
249#endif
250};
251
252static int
253getentropy_fallback(void *buf, size_t len)
254{
255	uint8_t results[SHA512_DIGEST_LENGTH];
256	int save_errno = errno, e, pgs = getpagesize(), faster = 0, repeat;
257	static int cnt;
258	struct timespec ts;
259	struct timeval tv;
260	double loadavg[3];
261	struct rusage ru;
262	sigset_t sigset;
263	struct stat st;
264	SHA512_CTX ctx;
265	static pid_t lastpid;
266	pid_t pid;
267	size_t i, ii, m;
268	char *p;
269
270	pid = getpid();
271	if (lastpid == pid) {
272		faster = 1;
273		repeat = 2;
274	} else {
275		faster = 0;
276		lastpid = pid;
277		repeat = REPEAT;
278	}
279	for (i = 0; i < len; ) {
280		int j;
281		SHA512_Init(&ctx);
282		for (j = 0; j < repeat; j++) {
283			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
284			if (e != -1) {
285				cnt += (int)tv.tv_sec;
286				cnt += (int)tv.tv_usec;
287			}
288
289			for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
290				HX(clock_gettime(cl[ii], &ts) == -1, ts);
291
292			HX((pid = getpid()) == -1, pid);
293			HX((pid = getsid(pid)) == -1, pid);
294			HX((pid = getppid()) == -1, pid);
295			HX((pid = getpgid(0)) == -1, pid);
296			HX((e = getpriority(0, 0)) == -1, e);
297			HX((getloadavg(loadavg, 3) == -1), loadavg);
298
299			if (!faster) {
300				ts.tv_sec = 0;
301				ts.tv_nsec = 1;
302				(void) nanosleep(&ts, NULL);
303			}
304
305			HX(sigpending(&sigset) == -1, sigset);
306			HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
307			    sigset);
308
309#ifdef CAN_REFERENCE_MAIN
310			HF(main);		/* an addr in program */
311#endif
312			HF(getentropy);	/* an addr in this library */
313			HF(printf);		/* an addr in libc */
314			p = (char *)&p;
315			HD(p);		/* an addr on stack */
316			p = (char *)&errno;
317			HD(p);		/* the addr of errno */
318
319			if (i == 0) {
320				struct sockaddr_storage ss;
321				struct statvfs stvfs;
322				struct termios tios;
323				socklen_t ssl;
324				off_t off;
325
326				/*
327				 * Prime-sized mappings encourage fragmentation;
328				 * thus exposing some address entropy.
329				 */
330				struct mm {
331					size_t	npg;
332					void	*p;
333				} mm[] =	 {
334					{ 17, MAP_FAILED }, { 3, MAP_FAILED },
335					{ 11, MAP_FAILED }, { 2, MAP_FAILED },
336					{ 5, MAP_FAILED }, { 3, MAP_FAILED },
337					{ 7, MAP_FAILED }, { 1, MAP_FAILED },
338					{ 57, MAP_FAILED }, { 3, MAP_FAILED },
339					{ 131, MAP_FAILED }, { 1, MAP_FAILED },
340				};
341
342				for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
343					HX(mm[m].p = mmap(NULL,
344					    mm[m].npg * pgs,
345					    PROT_READ|PROT_WRITE,
346					    MAP_PRIVATE|MAP_ANON, -1,
347					    (off_t)0), mm[m].p);
348					if (mm[m].p != MAP_FAILED) {
349						size_t mo;
350
351						/* Touch some memory... */
352						p = mm[m].p;
353						mo = cnt %
354						    (mm[m].npg * pgs - 1);
355						p[mo] = 1;
356						cnt += (int)((long)(mm[m].p)
357						    / pgs);
358					}
359
360					/* Check cnts and times... */
361					for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
362					    ii++) {
363						HX((e = clock_gettime(cl[ii],
364						    &ts)) == -1, ts);
365						if (e != -1)
366							cnt += (int)ts.tv_nsec;
367					}
368
369					HX((e = getrusage(RUSAGE_SELF,
370					    &ru)) == -1, ru);
371					if (e != -1) {
372						cnt += (int)ru.ru_utime.tv_sec;
373						cnt += (int)ru.ru_utime.tv_usec;
374					}
375				}
376
377				for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
378					if (mm[m].p != MAP_FAILED)
379						munmap(mm[m].p, mm[m].npg * pgs);
380					mm[m].p = MAP_FAILED;
381				}
382
383				HX(stat(".", &st) == -1, st);
384				HX(statvfs(".", &stvfs) == -1, stvfs);
385
386				HX(stat("/", &st) == -1, st);
387				HX(statvfs("/", &stvfs) == -1, stvfs);
388
389				HX((e = fstat(0, &st)) == -1, st);
390				if (e == -1) {
391					if (S_ISREG(st.st_mode) ||
392					    S_ISFIFO(st.st_mode) ||
393					    S_ISSOCK(st.st_mode)) {
394						HX(fstatvfs(0, &stvfs) == -1,
395						    stvfs);
396						HX((off = lseek(0, (off_t)0,
397						    SEEK_CUR)) < 0, off);
398					}
399					if (S_ISCHR(st.st_mode)) {
400						HX(tcgetattr(0, &tios) == -1,
401						    tios);
402					} else if (S_ISSOCK(st.st_mode)) {
403						memset(&ss, 0, sizeof ss);
404						ssl = sizeof(ss);
405						HX(getpeername(0,
406						    (void *)&ss, &ssl) == -1,
407						    ss);
408					}
409				}
410
411				HX((e = getrusage(RUSAGE_CHILDREN,
412				    &ru)) == -1, ru);
413				if (e != -1) {
414					cnt += (int)ru.ru_utime.tv_sec;
415					cnt += (int)ru.ru_utime.tv_usec;
416				}
417			} else {
418				/* Subsequent hashes absorb previous result */
419				HD(results);
420			}
421
422			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
423			if (e != -1) {
424				cnt += (int)tv.tv_sec;
425				cnt += (int)tv.tv_usec;
426			}
427
428			HD(cnt);
429		}
430		SHA512_Final(results, &ctx);
431		memcpy((char *)buf + i, results, min(sizeof(results), len - i));
432		i += min(sizeof(results), len - i);
433	}
434	memset(results, 0, sizeof results);
435	if (gotdata(buf, len) == 0) {
436		errno = save_errno;
437		return 0;		/* satisfied */
438	}
439	errno = EIO;
440	return -1;
441}
442