1 /*	$OpenBSD: getentropy_aix.c,v 1.5 2016/08/07 03:27:21 tb 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 psuedo 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 min(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 
61 int	getentropy(void *buf, size_t len);
62 
63 static int gotdata(char *buf, size_t len);
64 static int getentropy_urandom(void *buf, size_t len, const char *path,
65     int devfscheck);
66 static int getentropy_fallback(void *buf, size_t len);
67 
68 int
69 getentropy(void *buf, size_t len)
70 {
71 	int ret = -1;
72 
73 	if (len > 256) {
74 		errno = EIO;
75 		return (-1);
76 	}
77 
78 	/*
79 	 * Try to get entropy with /dev/urandom
80 	 */
81 	ret = getentropy_urandom(buf, len, "/dev/urandom", 0);
82 	if (ret != -1)
83 		return (ret);
84 
85 	/*
86 	 * Entropy collection via /dev/urandom has failed.
87 	 *
88 	 * No other API exists for collecting entropy, and we have
89 	 * no failsafe way to get it on AIX that is not sensitive
90 	 * to resource exhaustion.
91 	 *
92 	 * We have very few options:
93 	 *     - Even syslog_r is unsafe to call at this low level, so
94 	 *	 there is no way to alert the user or program.
95 	 *     - Cannot call abort() because some systems have unsafe
96 	 *	 corefiles.
97 	 *     - Could raise(SIGKILL) resulting in silent program termination.
98 	 *     - Return EIO, to hint that arc4random's stir function
99 	 *       should raise(SIGKILL)
100 	 *     - Do the best under the circumstances....
101 	 *
102 	 * This code path exists to bring light to the issue that AIX
103 	 * does not provide a failsafe API for entropy collection.
104 	 *
105 	 * We hope this demonstrates that AIX should consider
106 	 * providing a new failsafe API which works in a chroot or
107 	 * when file descriptors are exhausted.
108 	 */
109 #undef FAIL_INSTEAD_OF_TRYING_FALLBACK
110 #ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
111 	raise(SIGKILL);
112 #endif
113 	ret = getentropy_fallback(buf, len);
114 	if (ret != -1)
115 		return (ret);
116 
117 	errno = EIO;
118 	return (ret);
119 }
120 
121 /*
122  * Basic sanity checking; wish we could do better.
123  */
124 static int
125 gotdata(char *buf, size_t len)
126 {
127 	char	any_set = 0;
128 	size_t	i;
129 
130 	for (i = 0; i < len; ++i)
131 		any_set |= buf[i];
132 	if (any_set == 0)
133 		return (-1);
134 	return (0);
135 }
136 
137 static int
138 getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck)
139 {
140 	struct stat st;
141 	size_t i;
142 	int fd, flags;
143 	int save_errno = errno;
144 
145 start:
146 
147 	flags = O_RDONLY;
148 #ifdef O_NOFOLLOW
149 	flags |= O_NOFOLLOW;
150 #endif
151 #ifdef O_CLOEXEC
152 	flags |= O_CLOEXEC;
153 #endif
154 	fd = open(path, flags, 0);
155 	if (fd == -1) {
156 		if (errno == EINTR)
157 			goto start;
158 		goto nodevrandom;
159 	}
160 #ifndef O_CLOEXEC
161 	fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
162 #endif
163 
164 	/* Lightly verify that the device node looks sane */
165 	if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode)) {
166 		close(fd);
167 		goto nodevrandom;
168 	}
169 	for (i = 0; i < len; ) {
170 		size_t wanted = len - i;
171 		ssize_t ret = read(fd, (char *)buf + i, wanted);
172 
173 		if (ret == -1) {
174 			if (errno == EAGAIN || errno == EINTR)
175 				continue;
176 			close(fd);
177 			goto nodevrandom;
178 		}
179 		i += ret;
180 	}
181 	close(fd);
182 	if (gotdata(buf, len) == 0) {
183 		errno = save_errno;
184 		return (0);		/* satisfied */
185 	}
186 nodevrandom:
187 	errno = EIO;
188 	return (-1);
189 }
190 
191 static const int cl[] = {
192 	CLOCK_REALTIME,
193 #ifdef CLOCK_MONOTONIC
194 	CLOCK_MONOTONIC,
195 #endif
196 #ifdef CLOCK_MONOTONIC_RAW
197 	CLOCK_MONOTONIC_RAW,
198 #endif
199 #ifdef CLOCK_TAI
200 	CLOCK_TAI,
201 #endif
202 #ifdef CLOCK_VIRTUAL
203 	CLOCK_VIRTUAL,
204 #endif
205 #ifdef CLOCK_UPTIME
206 	CLOCK_UPTIME,
207 #endif
208 #ifdef CLOCK_PROCESS_CPUTIME_ID
209 	CLOCK_PROCESS_CPUTIME_ID,
210 #endif
211 #ifdef CLOCK_THREAD_CPUTIME_ID
212 	CLOCK_THREAD_CPUTIME_ID,
213 #endif
214 };
215 
216 static int
217 getentropy_fallback(void *buf, size_t len)
218 {
219 	uint8_t results[SHA512_DIGEST_LENGTH];
220 	int save_errno = errno, e, pgs = sysconf(_SC_PAGESIZE), faster = 0, repeat;
221 	static int cnt;
222 	struct timespec ts;
223 	struct timeval tv;
224 	perfstat_cpu_total_t cpustats;
225 #ifdef _AIX61
226 	perfstat_cpu_total_wpar_t cpustats_wpar;
227 #endif
228 	perfstat_partition_total_t lparstats;
229 	perfstat_disk_total_t diskinfo;
230 	perfstat_netinterface_total_t netinfo;
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(perfstat_cpu_total(NULL, &cpustats,
260 			    sizeof(cpustats), 1) == -1, cpustats);
261 
262 #ifdef _AIX61
263 			HX(perfstat_cpu_total_wpar(NULL, &cpustats_wpar,
264 			    sizeof(cpustats_wpar), 1) == -1, cpustats_wpar);
265 #endif
266 
267 			HX(perfstat_partition_total(NULL, &lparstats,
268 			    sizeof(lparstats), 1) == -1, lparstats);
269 
270 			HX(perfstat_disk_total(NULL, &diskinfo,
271 			    sizeof(diskinfo), 1) == -1, diskinfo);
272 
273 			HX(perfstat_netinterface_total(NULL, &netinfo,
274 			    sizeof(netinfo), 1) == -1, netinfo);
275 
276 			for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
277 				HX(clock_gettime(cl[ii], &ts) == -1, ts);
278 
279 			HX((pid = getpid()) == -1, pid);
280 			HX((pid = getsid(pid)) == -1, pid);
281 			HX((pid = getppid()) == -1, pid);
282 			HX((pid = getpgid(0)) == -1, pid);
283 			HX((e = getpriority(0, 0)) == -1, e);
284 
285 			if (!faster) {
286 				ts.tv_sec = 0;
287 				ts.tv_nsec = 1;
288 				(void) nanosleep(&ts, NULL);
289 			}
290 
291 			HX(sigpending(&sigset) == -1, sigset);
292 			HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
293 			    sigset);
294 
295 			HF(getentropy);	/* an addr in this library */
296 			HF(printf);		/* an addr in libc */
297 			p = (char *)&p;
298 			HD(p);		/* an addr on stack */
299 			p = (char *)&errno;
300 			HD(p);		/* the addr of errno */
301 
302 			if (i == 0) {
303 				struct sockaddr_storage ss;
304 				struct statvfs stvfs;
305 				struct termios tios;
306 				socklen_t ssl;
307 				off_t off;
308 
309 				/*
310 				 * Prime-sized mappings encourage fragmentation;
311 				 * thus exposing some address entropy.
312 				 */
313 				struct mm {
314 					size_t	npg;
315 					void	*p;
316 				} mm[] =	 {
317 					{ 17, MAP_FAILED }, { 3, MAP_FAILED },
318 					{ 11, MAP_FAILED }, { 2, MAP_FAILED },
319 					{ 5, MAP_FAILED }, { 3, MAP_FAILED },
320 					{ 7, MAP_FAILED }, { 1, MAP_FAILED },
321 					{ 57, MAP_FAILED }, { 3, MAP_FAILED },
322 					{ 131, MAP_FAILED }, { 1, MAP_FAILED },
323 				};
324 
325 				for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
326 					HX(mm[m].p = mmap(NULL,
327 					    mm[m].npg * pgs,
328 					    PROT_READ|PROT_WRITE,
329 					    MAP_PRIVATE|MAP_ANON, -1,
330 					    (off_t)0), mm[m].p);
331 					if (mm[m].p != MAP_FAILED) {
332 						size_t mo;
333 
334 						/* Touch some memory... */
335 						p = mm[m].p;
336 						mo = cnt %
337 						    (mm[m].npg * pgs - 1);
338 						p[mo] = 1;
339 						cnt += (int)((long)(mm[m].p)
340 						    / pgs);
341 					}
342 
343 					/* Check cnts and times... */
344 					for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
345 					    ii++) {
346 						HX((e = clock_gettime(cl[ii],
347 						    &ts)) == -1, ts);
348 						if (e != -1)
349 							cnt += (int)ts.tv_nsec;
350 					}
351 
352 					HX((e = getrusage(RUSAGE_SELF,
353 					    &ru)) == -1, ru);
354 					if (e != -1) {
355 						cnt += (int)ru.ru_utime.tv_sec;
356 						cnt += (int)ru.ru_utime.tv_usec;
357 					}
358 				}
359 
360 				for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
361 					if (mm[m].p != MAP_FAILED)
362 						munmap(mm[m].p, mm[m].npg * pgs);
363 					mm[m].p = MAP_FAILED;
364 				}
365 
366 				HX(stat(".", &st) == -1, st);
367 				HX(statvfs(".", &stvfs) == -1, stvfs);
368 
369 				HX(stat("/", &st) == -1, st);
370 				HX(statvfs("/", &stvfs) == -1, stvfs);
371 
372 				HX((e = fstat(0, &st)) == -1, st);
373 				if (e == -1) {
374 					if (S_ISREG(st.st_mode) ||
375 					    S_ISFIFO(st.st_mode) ||
376 					    S_ISSOCK(st.st_mode)) {
377 						HX(fstatvfs(0, &stvfs) == -1,
378 						    stvfs);
379 						HX((off = lseek(0, (off_t)0,
380 						    SEEK_CUR)) < 0, off);
381 					}
382 					if (S_ISCHR(st.st_mode)) {
383 						HX(tcgetattr(0, &tios) == -1,
384 						    tios);
385 					} else if (S_ISSOCK(st.st_mode)) {
386 						memset(&ss, 0, sizeof ss);
387 						ssl = sizeof(ss);
388 						HX(getpeername(0,
389 						    (void *)&ss, &ssl) == -1,
390 						    ss);
391 					}
392 				}
393 
394 				HX((e = getrusage(RUSAGE_CHILDREN,
395 				    &ru)) == -1, ru);
396 				if (e != -1) {
397 					cnt += (int)ru.ru_utime.tv_sec;
398 					cnt += (int)ru.ru_utime.tv_usec;
399 				}
400 			} else {
401 				/* Subsequent hashes absorb previous result */
402 				HD(results);
403 			}
404 
405 			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
406 			if (e != -1) {
407 				cnt += (int)tv.tv_sec;
408 				cnt += (int)tv.tv_usec;
409 			}
410 
411 			HD(cnt);
412 		}
413 		SHA512_Final(results, &ctx);
414 		memcpy((char *)buf + i, results, min(sizeof(results), len - i));
415 		i += min(sizeof(results), len - i);
416 	}
417 	explicit_bzero(&ctx, sizeof ctx);
418 	explicit_bzero(results, sizeof results);
419 	if (gotdata(buf, len) == 0) {
420 		errno = save_errno;
421 		return (0);		/* satisfied */
422 	}
423 	errno = EIO;
424 	return (-1);
425 }
426