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
72 int getentropy(void *buf, size_t len);
73
74 #ifdef CAN_REFERENCE_MAIN
75 extern int main(int, char *argv[]);
76 #endif
77 static int gotdata(char *buf, size_t len);
78 static int getentropy_urandom(void *buf, size_t len, const char *path,
79 int devfscheck);
80 static int getentropy_fallback(void *buf, size_t len);
81
82 int
getentropy(void * buf,size_t len)83 getentropy(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 */
159 static int
gotdata(char * buf,size_t len)160 gotdata(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
172 static int
getentropy_urandom(void * buf,size_t len,const char * path,int devfscheck)173 getentropy_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
180 start:
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 }
222 nodevrandom:
223 errno = EIO;
224 return -1;
225 }
226
227 static 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
252 static int
getentropy_fallback(void * buf,size_t len)253 getentropy_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