2 * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
3 * Copyright (c) 2014 Bob Beck <beck@obtuse.com>
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 * Emulation of getentropy(2) as documented at:
18 * http://man.openbsd.org/getentropy.2
23 #ifndef HAVE_GETENTROPY
25 #include <sys/param.h>
27 #include <sys/resource.h>
28 #include <sys/socket.h>
31 # include <sys/sysctl.h>
33 #ifdef HAVE_SYS_STATVFS_H
34 # include <sys/statvfs.h>
38 #ifdef HAVE_SYS_SYSCALL_H
39 # include <sys/syscall.h>
41 #ifdef HAVE_LINUX_RANDOM_H
42 # include <linux/types.h>
43 # include <linux/random.h>
54 #if defined(HAVE_STDINT_H)
56 #elif defined(HAVE_INTTYPES_H)
57 # include <inttypes.h>
60 # include <sys/auxv.h>
62 #ifdef HAVE_DL_ITERATE_PHDR
66 #include "sudo_compat.h"
67 #include "sudo_digest.h"
68 #include "sudo_rand.h"
70 #if !defined(MAP_ANON) && defined(MAP_ANONYMOUS)
71 # define MAP_ANON MAP_ANONYMOUS
75 #define min(a, b) (((a) < (b)) ? (a) : (b))
85 #define HR(x, l) (sudo_digest_update(ctx, (char *)(x), (l)))
86 #define HD(x) (sudo_digest_update(ctx, (char *)&(x), sizeof (x)))
87 #define HF(x) (sudo_digest_update(ctx, (char *)&(x), sizeof (void*)))
89 int sudo_getentropy(void *buf, size_t len);
91 static int getentropy_getrandom(void *buf, size_t len);
92 static int getentropy_sysctl(void *buf, size_t len);
93 static int getentropy_urandom(void *buf, size_t len, const char *path,
95 static int getentropy_fallback(void *buf, size_t len);
96 static int gotdata(char *buf, size_t len);
97 #ifdef HAVE_DL_ITERATE_PHDR
98 static int getentropy_phdr(struct dl_phdr_info *info, size_t size, void *data);
102 sudo_getentropy(void *buf, size_t len)
111 ret = getentropy_getrandom(buf, len);
115 ret = getentropy_sysctl(buf, len);
120 * Try to get entropy with /dev/urandom
122 ret = getentropy_urandom(buf, len, "/dev/urandom", 0);
127 * Entropy collection via /dev/urandom has failed.
129 * No other API exists for collecting entropy, and we have no
130 * failsafe way to get it that is not sensitive to resource exhaustion.
132 * We have very few options:
133 * - Even syslog_r is unsafe to call at this low level, so
134 * there is no way to alert the user or program.
135 * - Cannot call abort() because some systems have unsafe
137 * - Could raise(SIGKILL) resulting in silent program termination.
138 * - Return EIO, to hint that arc4random's stir function
139 * should raise(SIGKILL)
140 * - Do the best under the circumstances....
142 * This code path exists to bring light to the issue that the OS
143 * does not provide a failsafe API for entropy collection.
145 * We hope this demonstrates that the OS should consider
146 * providing a new failsafe API which works in a chroot or
147 * when file descriptors are exhausted.
149 #undef FAIL_INSTEAD_OF_TRYING_FALLBACK
150 #ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
153 ret = getentropy_fallback(buf, len);
162 * This is an open source non-commercial project. Dear PVS-Studio, please check it.
163 * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
167 * Basic sanity checking; wish we could do better.
170 gotdata(char *buf, size_t len)
175 for (i = 0; i < len; ++i)
183 getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck)
188 int save_errno = errno;
192 /* We do not use O_NOFOLLOW since /dev/urandom is a link on Solaris. */
197 fd = open(path, flags, 0);
204 fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
207 /* Lightly verify that the device node looks sane */
208 if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode)) {
212 for (i = 0; i < len; ) {
213 size_t wanted = len - i;
214 ssize_t ret = read(fd, (char *)buf + i, wanted);
217 if (errno == EAGAIN || errno == EINTR)
225 if (gotdata(buf, len) == 0) {
227 return (0); /* satisfied */
234 #if defined(HAVE_SYSCTL) && defined(KERN_ARND)
236 getentropy_sysctl(void *buf, size_t len)
238 int save_errno = errno;
245 for (i = 0; i < len; ) {
246 size_t chunk = len - i;
248 if (sysctl(mib, 2, (char *)buf + i, &chunk, NULL, 0) == -1)
252 if (gotdata(buf, len) == 0) {
254 return (0); /* satisfied */
260 #elif defined(SYS__sysctl) && defined(RANDOM_UUID)
262 getentropy_sysctl(void *buf, size_t len)
266 int save_errno = errno;
269 mib[1] = KERN_RANDOM;
270 mib[2] = RANDOM_UUID;
272 for (i = 0; i < len; ) {
273 size_t chunk = min(len - i, 16);
275 /* SYS__sysctl because some systems already removed sysctl() */
276 struct __sysctl_args args = {
279 .oldval = (char *)buf + i,
282 if (syscall(SYS__sysctl, &args) != 0)
286 if (gotdata(buf, len) == 0) {
288 return (0); /* satisfied */
296 getentropy_sysctl(void *buf, size_t len)
303 #if defined(SYS_getrandom) && defined(GRND_NONBLOCK)
305 getentropy_getrandom(void *buf, size_t len)
307 int pre_errno = errno;
311 * Try descriptor-less getrandom(), in non-blocking mode.
313 * The design of Linux getrandom is broken. It has an
314 * uninitialized phase coupled with blocking behaviour, which
315 * is unacceptable from within a library at boot time without
316 * possible recovery. See http://bugs.python.org/issue26839#msg267745
319 ret = syscall(SYS_getrandom, buf, len, GRND_NONBLOCK);
320 } while (ret == -1 && errno == EINTR);
322 if (ret < 0 || (size_t)ret != len)
329 getentropy_getrandom(void *buf, size_t len)
336 #ifdef HAVE_CLOCK_GETTIME
337 static const int cl[] = {
339 #ifdef CLOCK_MONOTONIC
342 #ifdef CLOCK_MONOTONIC_RAW
354 #ifdef CLOCK_PROCESS_CPUTIME_ID
355 CLOCK_PROCESS_CPUTIME_ID,
357 #ifdef CLOCK_THREAD_CPUTIME_ID
358 CLOCK_THREAD_CPUTIME_ID,
361 #endif /* HAVE_CLOCK_GETTIME */
363 #ifdef HAVE_DL_ITERATE_PHDR
365 getentropy_phdr(struct dl_phdr_info *info, size_t size, void *data)
367 struct sudo_digest *ctx = data;
369 sudo_digest_update(ctx, &info->dlpi_addr, sizeof (info->dlpi_addr));
375 getentropy_fallback(void *buf, size_t len)
377 unsigned char *results = NULL;
378 int save_errno = errno, e, pgs = sysconf(_SC_PAGESIZE), faster = 0, repeat;
386 struct sudo_digest *ctx;
387 static pid_t lastpid;
389 size_t i, ii, m, digest_len;
392 if ((ctx = sudo_digest_alloc(SUDO_DIGEST_SHA512)) == NULL)
394 digest_len = sudo_digest_getlen(SUDO_DIGEST_SHA512);
395 if (digest_len == (size_t)-1 || (results = malloc(digest_len)) == NULL)
399 if (lastpid == pid) {
407 for (i = 0; i < len; ) {
409 for (j = 0; j < repeat; j++) {
410 HX((e = gettimeofday(&tv, NULL)) == -1, tv);
412 cnt += (int)tv.tv_sec;
413 cnt += (int)tv.tv_usec;
415 #ifdef HAVE_DL_ITERATE_PHDR
416 dl_iterate_phdr(getentropy_phdr, ctx);
419 #ifdef HAVE_CLOCK_GETTIME
420 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
421 HX(clock_gettime(cl[ii], &ts) == -1, ts);
422 #endif /* HAVE_CLOCK_GETTIME */
424 HX((pid = getpid()) == -1, pid);
425 HX((pid = getsid(pid)) == -1, pid);
426 HX((pid = getppid()) == -1, pid);
427 HX((pid = getpgid(0)) == -1, pid);
428 HX((e = getpriority(0, 0)) == -1, e);
433 (void) nanosleep(&ts, NULL);
436 HX(sigpending(&sigset) == -1, sigset);
437 HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
440 HF(sudo_getentropy); /* an addr in this library */
441 HF(printf); /* an addr in libc */
443 HD(p); /* an addr on stack */
445 HD(p); /* the addr of errno */
448 #ifdef HAVE_SYS_STATVFS_H
449 struct statvfs stvfs;
455 * Prime-sized mappings encourage fragmentation;
456 * thus exposing some address entropy.
462 { 17, MAP_FAILED }, { 3, MAP_FAILED },
463 { 11, MAP_FAILED }, { 2, MAP_FAILED },
464 { 5, MAP_FAILED }, { 3, MAP_FAILED },
465 { 7, MAP_FAILED }, { 1, MAP_FAILED },
466 { 57, MAP_FAILED }, { 3, MAP_FAILED },
467 { 131, MAP_FAILED }, { 1, MAP_FAILED },
470 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
471 HX(mm[m].p = mmap(NULL,
473 PROT_READ|PROT_WRITE,
474 MAP_PRIVATE|MAP_ANON, -1,
476 if (mm[m].p != MAP_FAILED) {
479 /* Touch some memory... */
482 (mm[m].npg * pgs - 1);
484 cnt += (int)((long)(mm[m].p)
488 /* Check cnts and times... */
489 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
491 HX((e = clock_gettime(cl[ii],
494 cnt += (int)ts.tv_nsec;
497 HX((e = getrusage(RUSAGE_SELF,
500 cnt += (int)ru.ru_utime.tv_sec;
501 cnt += (int)ru.ru_utime.tv_usec;
505 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
506 if (mm[m].p != MAP_FAILED)
507 munmap(mm[m].p, mm[m].npg * pgs);
508 mm[m].p = MAP_FAILED;
511 HX(stat(".", &st) == -1, st);
512 HX(stat("/", &st) == -1, st);
514 #ifdef HAVE_SYS_STATVFS_H
515 HX(statvfs(".", &stvfs) == -1, stvfs);
516 HX(statvfs("/", &stvfs) == -1, stvfs);
518 HX((e = fstat(0, &st)) == -1, st);
520 if (S_ISREG(st.st_mode) ||
521 S_ISFIFO(st.st_mode) ||
522 S_ISSOCK(st.st_mode)) {
523 #ifdef HAVE_SYS_STATVFS_H
524 HX(fstatvfs(0, &stvfs) == -1,
527 HX((off = lseek(0, (off_t)0,
528 SEEK_CUR)) < 0, off);
530 if (S_ISCHR(st.st_mode)) {
531 HX(tcgetattr(0, &tios) == -1,
534 } else if (S_ISSOCK(st.st_mode)) {
535 struct sockaddr_storage ss;
537 memset(&ss, 0, sizeof ss);
540 (void *)&ss, &ssl) == -1,
546 HX((e = getrusage(RUSAGE_CHILDREN,
549 cnt += (int)ru.ru_utime.tv_sec;
550 cnt += (int)ru.ru_utime.tv_usec;
553 /* Subsequent hashes absorb previous result */
554 HR(results, digest_len);
557 HX((e = gettimeofday(&tv, NULL)) == -1, tv);
559 cnt += (int)tv.tv_sec;
560 cnt += (int)tv.tv_usec;
566 #ifdef HAVE_GETAUXVAL
568 /* Not as random as you think but we take what we are given */
569 p = (char *) getauxval(AT_RANDOM);
573 #ifdef AT_SYSINFO_EHDR
574 p = (char *) getauxval(AT_SYSINFO_EHDR);
579 p = (char *) getauxval(AT_BASE);
583 #endif /* HAVE_GETAUXVAL */
585 sudo_digest_final(ctx, results);
586 sudo_digest_reset(ctx);
587 memcpy((char *)buf + i, results, min(digest_len, len - i));
588 i += min(digest_len, len - i);
590 if (gotdata(buf, len) == 0) {
592 ret = 0; /* satisfied */
597 sudo_digest_free(ctx);
598 if (results != NULL) {
599 memset_s(results, sizeof(results), 0, sizeof(results));
605 #endif /* HAVE_GETENTROPY */