getentropy_hpux.c revision 1.4 
1/*	$OpenBSD: getentropy_hpux.c,v 1.4 2015/09/11 11:52:55 deraadt 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 * Emulation of getentropy(2) as documented at:
20 * http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man2/getentropy.2
21 */
22
23#include <sys/types.h>
24#include <sys/param.h>
25#include <sys/ioctl.h>
26#include <sys/resource.h>
27#include <sys/syscall.h>
28#include <sys/statvfs.h>
29#include <sys/socket.h>
30#include <sys/mount.h>
31#include <sys/mman.h>
32#include <sys/stat.h>
33#include <sys/time.h>
34#include <stdlib.h>
35#include <stdint.h>
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#include <openssl/sha.h>
45
46#include <sys/vfs.h>
47
48#include <sys/pstat.h>
49
50#define REPEAT 5
51#define min(a, b) (((a) < (b)) ? (a) : (b))
52
53#define HX(a, b) \
54	do { \
55		if ((a)) \
56			HD(errno); \
57		else \
58			HD(b); \
59	} while (0)
60
61#define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
62#define HD(x)	 (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
63#define HF(x)    (SHA512_Update(&ctx, (char *)&(x), sizeof (void*)))
64
65int	getentropy(void *buf, size_t len);
66
67static int gotdata(char *buf, size_t len);
68static int getentropy_urandom(void *buf, size_t len, const char *path,
69    int devfscheck);
70static int getentropy_fallback(void *buf, size_t len);
71
72int
73getentropy(void *buf, size_t len)
74{
75	int ret = -1;
76
77	if (len > 256) {
78		errno = EIO;
79		return (-1);
80	}
81
82	/*
83	 * Try to get entropy with /dev/urandom
84	 */
85	ret = getentropy_urandom(buf, len, "/dev/urandom", 0);
86	if (ret != -1)
87		return (ret);
88
89	/*
90	 * Entropy collection via /dev/urandom has failed.
91	 *
92	 * No other API exists for collecting entropy, and we have
93	 * no failsafe way to get it on hpux that is not sensitive
94	 * to resource exhaustion.
95	 *
96	 * We have very few options:
97	 *     - Even syslog_r is unsafe to call at this low level, so
98	 *	 there is no way to alert the user or program.
99	 *     - Cannot call abort() because some systems have unsafe
100	 *	 corefiles.
101	 *     - Could raise(SIGKILL) resulting in silent program termination.
102	 *     - Return EIO, to hint that arc4random's stir function
103	 *       should raise(SIGKILL)
104	 *     - Do the best under the circumstances....
105	 *
106	 * This code path exists to bring light to the issue that hpux
107	 * does not provide a failsafe API for entropy collection.
108	 *
109	 * We hope this demonstrates that hpux should consider
110	 * providing a new failsafe API which works in a chroot or
111	 * when file descriptors are exhausted.
112	 */
113#undef FAIL_INSTEAD_OF_TRYING_FALLBACK
114#ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
115	raise(SIGKILL);
116#endif
117	ret = getentropy_fallback(buf, len);
118	if (ret != -1)
119		return (ret);
120
121	errno = EIO;
122	return (ret);
123}
124
125/*
126 * Basic sanity checking; wish we could do better.
127 */
128static int
129gotdata(char *buf, size_t len)
130{
131	char	any_set = 0;
132	size_t	i;
133
134	for (i = 0; i < len; ++i)
135		any_set |= buf[i];
136	if (any_set == 0)
137		return (-1);
138	return (0);
139}
140
141static int
142getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck)
143{
144	struct stat st;
145	size_t i;
146	int fd, flags;
147	int save_errno = errno;
148
149start:
150
151	flags = O_RDONLY;
152#ifdef O_NOFOLLOW
153	flags |= O_NOFOLLOW;
154#endif
155#ifdef O_CLOEXEC
156	flags |= O_CLOEXEC;
157#endif
158	fd = open(path, flags, 0);
159	if (fd == -1) {
160		if (errno == EINTR)
161			goto start;
162		goto nodevrandom;
163	}
164#ifndef O_CLOEXEC
165	fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
166#endif
167
168	/* Lightly verify that the device node looks sane */
169	if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode)) {
170		close(fd);
171		goto nodevrandom;
172	}
173	for (i = 0; i < len; ) {
174		size_t wanted = len - i;
175		ssize_t ret = read(fd, (char *)buf + i, wanted);
176
177		if (ret == -1) {
178			if (errno == EAGAIN || errno == EINTR)
179				continue;
180			close(fd);
181			goto nodevrandom;
182		}
183		i += ret;
184	}
185	close(fd);
186	if (gotdata(buf, len) == 0) {
187		errno = save_errno;
188		return (0);		/* satisfied */
189	}
190nodevrandom:
191	errno = EIO;
192	return (-1);
193}
194
195static const int cl[] = {
196	CLOCK_REALTIME,
197#ifdef CLOCK_MONOTONIC
198	CLOCK_MONOTONIC,
199#endif
200#ifdef CLOCK_MONOTONIC_RAW
201	CLOCK_MONOTONIC_RAW,
202#endif
203#ifdef CLOCK_TAI
204	CLOCK_TAI,
205#endif
206#ifdef CLOCK_VIRTUAL
207	CLOCK_VIRTUAL,
208#endif
209#ifdef CLOCK_UPTIME
210	CLOCK_UPTIME,
211#endif
212#ifdef CLOCK_PROCESS_CPUTIME_ID
213	CLOCK_PROCESS_CPUTIME_ID,
214#endif
215#ifdef CLOCK_THREAD_CPUTIME_ID
216	CLOCK_THREAD_CPUTIME_ID,
217#endif
218};
219
220static int
221getentropy_fallback(void *buf, size_t len)
222{
223	uint8_t results[SHA512_DIGEST_LENGTH];
224	int save_errno = errno, e, pgs = sysconf(_SC_PAGESIZE), faster = 0, repeat;
225	static int cnt;
226	struct timespec ts;
227	struct timeval tv;
228	struct pst_vminfo pvi;
229	struct pst_vm_status pvs;
230	struct pst_dynamic pdy;
231	struct rusage ru;
232	sigset_t sigset;
233	struct stat st;
234	SHA512_CTX ctx;
235	static pid_t lastpid;
236	pid_t pid;
237	size_t i, ii, m;
238	char *p;
239
240	pid = getpid();
241	if (lastpid == pid) {
242		faster = 1;
243		repeat = 2;
244	} else {
245		faster = 0;
246		lastpid = pid;
247		repeat = REPEAT;
248	}
249	for (i = 0; i < len; ) {
250		int j;
251		SHA512_Init(&ctx);
252		for (j = 0; j < repeat; j++) {
253			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
254			if (e != -1) {
255				cnt += (int)tv.tv_sec;
256				cnt += (int)tv.tv_usec;
257			}
258
259			HX(pstat_getvminfo(&pvi, sizeof(pvi), 1, 0) != 1, pvi);
260			HX(pstat_getprocvm(&pvs, sizeof(pvs), 0, 0) != 1, pvs);
261
262			for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
263				HX(clock_gettime(cl[ii], &ts) == -1, ts);
264
265			HX((pid = getpid()) == -1, pid);
266			HX((pid = getsid(pid)) == -1, pid);
267			HX((pid = getppid()) == -1, pid);
268			HX((pid = getpgid(0)) == -1, pid);
269			HX((e = getpriority(0, 0)) == -1, e);
270
271			if(pstat_getdynamic(&pdy, sizeof(pdy), 1, 0) != 1) {
272				HD(errno);
273			} else {
274				HD(pdy.psd_avg_1_min);
275				HD(pdy.psd_avg_5_min);
276				HD(pdy.psd_avg_15_min);
277			}
278
279			if (!faster) {
280				ts.tv_sec = 0;
281				ts.tv_nsec = 1;
282				(void) nanosleep(&ts, NULL);
283			}
284
285			HX(sigpending(&sigset) == -1, sigset);
286			HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
287			    sigset);
288
289			HF(getentropy);	/* an addr in this library */
290			HF(printf);		/* an addr in libc */
291			p = (char *)&p;
292			HD(p);		/* an addr on stack */
293			p = (char *)&errno;
294			HD(p);		/* the addr of errno */
295
296			if (i == 0) {
297				struct sockaddr_storage ss;
298				struct statvfs stvfs;
299				struct termios tios;
300				socklen_t ssl;
301				off_t off;
302
303				/*
304				 * Prime-sized mappings encourage fragmentation;
305				 * thus exposing some address entropy.
306				 */
307				struct mm {
308					size_t	npg;
309					void	*p;
310				} mm[] =	 {
311					{ 17, MAP_FAILED }, { 3, MAP_FAILED },
312					{ 11, MAP_FAILED }, { 2, MAP_FAILED },
313					{ 5, MAP_FAILED }, { 3, MAP_FAILED },
314					{ 7, MAP_FAILED }, { 1, MAP_FAILED },
315					{ 57, MAP_FAILED }, { 3, MAP_FAILED },
316					{ 131, MAP_FAILED }, { 1, MAP_FAILED },
317				};
318
319				for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
320					HX(mm[m].p = mmap(NULL,
321					    mm[m].npg * pgs,
322					    PROT_READ|PROT_WRITE,
323					    MAP_PRIVATE|MAP_ANON, -1,
324					    (off_t)0), mm[m].p);
325					if (mm[m].p != MAP_FAILED) {
326						size_t mo;
327
328						/* Touch some memory... */
329						p = mm[m].p;
330						mo = cnt %
331						    (mm[m].npg * pgs - 1);
332						p[mo] = 1;
333						cnt += (int)((long)(mm[m].p)
334						    / pgs);
335					}
336
337					/* Check cnts and times... */
338					for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
339					    ii++) {
340						HX((e = clock_gettime(cl[ii],
341						    &ts)) == -1, ts);
342						if (e != -1)
343							cnt += (int)ts.tv_nsec;
344					}
345
346					HX((e = getrusage(RUSAGE_SELF,
347					    &ru)) == -1, ru);
348					if (e != -1) {
349						cnt += (int)ru.ru_utime.tv_sec;
350						cnt += (int)ru.ru_utime.tv_usec;
351					}
352				}
353
354				for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
355					if (mm[m].p != MAP_FAILED)
356						munmap(mm[m].p, mm[m].npg * pgs);
357					mm[m].p = MAP_FAILED;
358				}
359
360				HX(stat(".", &st) == -1, st);
361				HX(statvfs(".", &stvfs) == -1, stvfs);
362
363				HX(stat("/", &st) == -1, st);
364				HX(statvfs("/", &stvfs) == -1, stvfs);
365
366				HX((e = fstat(0, &st)) == -1, st);
367				if (e == -1) {
368					if (S_ISREG(st.st_mode) ||
369					    S_ISFIFO(st.st_mode) ||
370					    S_ISSOCK(st.st_mode)) {
371						HX(fstatvfs(0, &stvfs) == -1,
372						    stvfs);
373						HX((off = lseek(0, (off_t)0,
374						    SEEK_CUR)) < 0, off);
375					}
376					if (S_ISCHR(st.st_mode)) {
377						HX(tcgetattr(0, &tios) == -1,
378						    tios);
379					} else if (S_ISSOCK(st.st_mode)) {
380						memset(&ss, 0, sizeof ss);
381						ssl = sizeof(ss);
382						HX(getpeername(0,
383						    (void *)&ss, &ssl) == -1,
384						    ss);
385					}
386				}
387
388				HX((e = getrusage(RUSAGE_CHILDREN,
389				    &ru)) == -1, ru);
390				if (e != -1) {
391					cnt += (int)ru.ru_utime.tv_sec;
392					cnt += (int)ru.ru_utime.tv_usec;
393				}
394			} else {
395				/* Subsequent hashes absorb previous result */
396				HD(results);
397			}
398
399			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
400			if (e != -1) {
401				cnt += (int)tv.tv_sec;
402				cnt += (int)tv.tv_usec;
403			}
404
405			HD(cnt);
406		}
407		SHA512_Final(results, &ctx);
408		memcpy((char *)buf + i, results, min(sizeof(results), len - i));
409		i += min(sizeof(results), len - i);
410	}
411	explicit_bzero(&ctx, sizeof ctx);
412	explicit_bzero(results, sizeof results);
413	if (gotdata(buf, len) == 0) {
414		errno = save_errno;
415		return (0);		/* satisfied */
416	}
417	errno = EIO;
418	return (-1);
419}
420