1/*	$OpenBSD: getentropy_aix.c,v 1.9 2022/12/26 07:18:50 jmc Exp $	*/
2
3/*
4 * Copyright (c) 2015 Michael Felt <aixtools@gmail.com>
5 * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
6 * Copyright (c) 2014 Bob Beck <beck@obtuse.com>
7 *
8 * Permission to use, copy, modify, and distribute this software for any
9 * purpose with or without fee is hereby granted, provided that the above
10 * copyright notice and this permission notice appear in all copies.
11 *
12 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
13 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
14 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
15 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
16 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
17 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
18 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
19 *
20 * Emulation of getentropy(2) as documented at:
21 * http://man.openbsd.org/getentropy.2
22 */
23/*
24 * -lperfstat is needed for the pseudo entropy data
25 */
26
27#include <sys/mman.h>
28#include <sys/procfs.h>
29#include <sys/protosw.h>
30#include <sys/resource.h>
31#include <sys/socket.h>
32#include <sys/stat.h>
33#include <sys/statvfs.h>
34#include <sys/timers.h>
35#include <errno.h>
36#include <fcntl.h>
37#include <signal.h>
38#include <stdio.h>
39#include <string.h>
40#include <termios.h>
41
42#include <openssl/sha.h>
43
44#include <libperfstat.h>
45
46#define REPEAT 5
47#define MINIMUM(a, b) (((a) < (b)) ? (a) : (b))
48
49#define HX(a, b) \
50	do { \
51		if ((a)) \
52			HD(errno); \
53		else \
54			HD(b); \
55	} while (0)
56
57#define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
58#define HD(x)	 (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
59#define HF(x)    (SHA512_Update(&ctx, (char *)&(x), sizeof (void*)))
60
61int	getentropy(void *buf, size_t len);
62
63static int getentropy_urandom(void *buf, size_t len, const char *path,
64    int devfscheck);
65static int getentropy_fallback(void *buf, size_t len);
66
67int
68getentropy(void *buf, size_t len)
69{
70	int ret = -1;
71
72	if (len > 256) {
73		errno = EIO;
74		return (-1);
75	}
76
77	/*
78	 * Try to get entropy with /dev/urandom
79	 */
80	ret = getentropy_urandom(buf, len, "/dev/urandom", 0);
81	if (ret != -1)
82		return (ret);
83
84	/*
85	 * Entropy collection via /dev/urandom has failed.
86	 *
87	 * No other API exists for collecting entropy, and we have
88	 * no failsafe way to get it on AIX that is not sensitive
89	 * to resource exhaustion.
90	 *
91	 * We have very few options:
92	 *     - Even syslog_r is unsafe to call at this low level, so
93	 *	 there is no way to alert the user or program.
94	 *     - Cannot call abort() because some systems have unsafe
95	 *	 corefiles.
96	 *     - Could raise(SIGKILL) resulting in silent program termination.
97	 *     - Return EIO, to hint that arc4random's stir function
98	 *       should raise(SIGKILL)
99	 *     - Do the best under the circumstances....
100	 *
101	 * This code path exists to bring light to the issue that AIX
102	 * does not provide a failsafe API for entropy collection.
103	 *
104	 * We hope this demonstrates that AIX should consider
105	 * providing a new failsafe API which works in a chroot or
106	 * when file descriptors are exhausted.
107	 */
108#undef FAIL_INSTEAD_OF_TRYING_FALLBACK
109#ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
110	raise(SIGKILL);
111#endif
112	ret = getentropy_fallback(buf, len);
113	if (ret != -1)
114		return (ret);
115
116	errno = EIO;
117	return (ret);
118}
119
120static int
121getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck)
122{
123	struct stat st;
124	size_t i;
125	int fd, flags;
126	int save_errno = errno;
127
128start:
129
130	flags = O_RDONLY;
131#ifdef O_NOFOLLOW
132	flags |= O_NOFOLLOW;
133#endif
134#ifdef O_CLOEXEC
135	flags |= O_CLOEXEC;
136#endif
137	fd = open(path, flags);
138	if (fd == -1) {
139		if (errno == EINTR)
140			goto start;
141		goto nodevrandom;
142	}
143#ifndef O_CLOEXEC
144	fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
145#endif
146
147	/* Lightly verify that the device node looks sane */
148	if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode)) {
149		close(fd);
150		goto nodevrandom;
151	}
152	for (i = 0; i < len; ) {
153		size_t wanted = len - i;
154		ssize_t ret = read(fd, (char *)buf + i, wanted);
155
156		if (ret == -1) {
157			if (errno == EAGAIN || errno == EINTR)
158				continue;
159			close(fd);
160			goto nodevrandom;
161		}
162		i += ret;
163	}
164	close(fd);
165	errno = save_errno;
166	return (0);		/* satisfied */
167nodevrandom:
168	errno = EIO;
169	return (-1);
170}
171
172static const int cl[] = {
173	CLOCK_REALTIME,
174#ifdef CLOCK_MONOTONIC
175	CLOCK_MONOTONIC,
176#endif
177#ifdef CLOCK_MONOTONIC_RAW
178	CLOCK_MONOTONIC_RAW,
179#endif
180#ifdef CLOCK_TAI
181	CLOCK_TAI,
182#endif
183#ifdef CLOCK_VIRTUAL
184	CLOCK_VIRTUAL,
185#endif
186#ifdef CLOCK_UPTIME
187	CLOCK_UPTIME,
188#endif
189#ifdef CLOCK_PROCESS_CPUTIME_ID
190	CLOCK_PROCESS_CPUTIME_ID,
191#endif
192#ifdef CLOCK_THREAD_CPUTIME_ID
193	CLOCK_THREAD_CPUTIME_ID,
194#endif
195};
196
197static int
198getentropy_fallback(void *buf, size_t len)
199{
200	uint8_t results[SHA512_DIGEST_LENGTH];
201	int save_errno = errno, e, pgs = sysconf(_SC_PAGESIZE), faster = 0, repeat;
202	static int cnt;
203	struct timespec ts;
204	struct timeval tv;
205	perfstat_cpu_total_t cpustats;
206#ifdef _AIX61
207	perfstat_cpu_total_wpar_t cpustats_wpar;
208#endif
209	perfstat_partition_total_t lparstats;
210	perfstat_disk_total_t diskinfo;
211	perfstat_netinterface_total_t netinfo;
212	struct rusage ru;
213	sigset_t sigset;
214	struct stat st;
215	SHA512_CTX ctx;
216	static pid_t lastpid;
217	pid_t pid;
218	size_t i, ii, m;
219	char *p;
220
221	pid = getpid();
222	if (lastpid == pid) {
223		faster = 1;
224		repeat = 2;
225	} else {
226		faster = 0;
227		lastpid = pid;
228		repeat = REPEAT;
229	}
230	for (i = 0; i < len; ) {
231		int j;
232		SHA512_Init(&ctx);
233		for (j = 0; j < repeat; j++) {
234			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
235			if (e != -1) {
236				cnt += (int)tv.tv_sec;
237				cnt += (int)tv.tv_usec;
238			}
239
240			HX(perfstat_cpu_total(NULL, &cpustats,
241			    sizeof(cpustats), 1) == -1, cpustats);
242
243#ifdef _AIX61
244			HX(perfstat_cpu_total_wpar(NULL, &cpustats_wpar,
245			    sizeof(cpustats_wpar), 1) == -1, cpustats_wpar);
246#endif
247
248			HX(perfstat_partition_total(NULL, &lparstats,
249			    sizeof(lparstats), 1) == -1, lparstats);
250
251			HX(perfstat_disk_total(NULL, &diskinfo,
252			    sizeof(diskinfo), 1) == -1, diskinfo);
253
254			HX(perfstat_netinterface_total(NULL, &netinfo,
255			    sizeof(netinfo), 1) == -1, netinfo);
256
257			for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
258				HX(clock_gettime(cl[ii], &ts) == -1, ts);
259
260			HX((pid = getpid()) == -1, pid);
261			HX((pid = getsid(pid)) == -1, pid);
262			HX((pid = getppid()) == -1, pid);
263			HX((pid = getpgid(0)) == -1, pid);
264			HX((e = getpriority(0, 0)) == -1, e);
265
266			if (!faster) {
267				ts.tv_sec = 0;
268				ts.tv_nsec = 1;
269				(void) nanosleep(&ts, NULL);
270			}
271
272			HX(sigpending(&sigset) == -1, sigset);
273			HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
274			    sigset);
275
276			HF(getentropy);	/* an addr in this library */
277			HF(printf);		/* an addr in libc */
278			p = (char *)&p;
279			HD(p);		/* an addr on stack */
280			p = (char *)&errno;
281			HD(p);		/* the addr of errno */
282
283			if (i == 0) {
284				struct sockaddr_storage ss;
285				struct statvfs stvfs;
286				struct termios tios;
287				socklen_t ssl;
288				off_t off;
289
290				/*
291				 * Prime-sized mappings encourage fragmentation;
292				 * thus exposing some address entropy.
293				 */
294				struct mm {
295					size_t	npg;
296					void	*p;
297				} mm[] =	 {
298					{ 17, MAP_FAILED }, { 3, MAP_FAILED },
299					{ 11, MAP_FAILED }, { 2, MAP_FAILED },
300					{ 5, MAP_FAILED }, { 3, MAP_FAILED },
301					{ 7, MAP_FAILED }, { 1, MAP_FAILED },
302					{ 57, MAP_FAILED }, { 3, MAP_FAILED },
303					{ 131, MAP_FAILED }, { 1, MAP_FAILED },
304				};
305
306				for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
307					HX(mm[m].p = mmap(NULL,
308					    mm[m].npg * pgs,
309					    PROT_READ|PROT_WRITE,
310					    MAP_PRIVATE|MAP_ANON, -1,
311					    (off_t)0), mm[m].p);
312					if (mm[m].p != MAP_FAILED) {
313						size_t mo;
314
315						/* Touch some memory... */
316						p = mm[m].p;
317						mo = cnt %
318						    (mm[m].npg * pgs - 1);
319						p[mo] = 1;
320						cnt += (int)((long)(mm[m].p)
321						    / pgs);
322					}
323
324					/* Check cnts and times... */
325					for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
326					    ii++) {
327						HX((e = clock_gettime(cl[ii],
328						    &ts)) == -1, ts);
329						if (e != -1)
330							cnt += (int)ts.tv_nsec;
331					}
332
333					HX((e = getrusage(RUSAGE_SELF,
334					    &ru)) == -1, ru);
335					if (e != -1) {
336						cnt += (int)ru.ru_utime.tv_sec;
337						cnt += (int)ru.ru_utime.tv_usec;
338					}
339				}
340
341				for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
342					if (mm[m].p != MAP_FAILED)
343						munmap(mm[m].p, mm[m].npg * pgs);
344					mm[m].p = MAP_FAILED;
345				}
346
347				HX(stat(".", &st) == -1, st);
348				HX(statvfs(".", &stvfs) == -1, stvfs);
349
350				HX(stat("/", &st) == -1, st);
351				HX(statvfs("/", &stvfs) == -1, stvfs);
352
353				HX((e = fstat(0, &st)) == -1, st);
354				if (e == -1) {
355					if (S_ISREG(st.st_mode) ||
356					    S_ISFIFO(st.st_mode) ||
357					    S_ISSOCK(st.st_mode)) {
358						HX(fstatvfs(0, &stvfs) == -1,
359						    stvfs);
360						HX((off = lseek(0, (off_t)0,
361						    SEEK_CUR)) < 0, off);
362					}
363					if (S_ISCHR(st.st_mode)) {
364						HX(tcgetattr(0, &tios) == -1,
365						    tios);
366					} else if (S_ISSOCK(st.st_mode)) {
367						memset(&ss, 0, sizeof ss);
368						ssl = sizeof(ss);
369						HX(getpeername(0,
370						    (void *)&ss, &ssl) == -1,
371						    ss);
372					}
373				}
374
375				HX((e = getrusage(RUSAGE_CHILDREN,
376				    &ru)) == -1, ru);
377				if (e != -1) {
378					cnt += (int)ru.ru_utime.tv_sec;
379					cnt += (int)ru.ru_utime.tv_usec;
380				}
381			} else {
382				/* Subsequent hashes absorb previous result */
383				HD(results);
384			}
385
386			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
387			if (e != -1) {
388				cnt += (int)tv.tv_sec;
389				cnt += (int)tv.tv_usec;
390			}
391
392			HD(cnt);
393		}
394		SHA512_Final(results, &ctx);
395		memcpy((char *)buf + i, results, MINIMUM(sizeof(results), len - i));
396		i += MINIMUM(sizeof(results), len - i);
397	}
398	explicit_bzero(&ctx, sizeof ctx);
399	explicit_bzero(results, sizeof results);
400	errno = save_errno;
401	return (0);		/* satisfied */
402}
403