1 /* $OpenBSD: getentropy_solaris.c,v 1.3 2014/07/12 14:46:31 deraadt Exp $ */
4 * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
5 * Copyright (c) 2014 Bob Beck <beck@obtuse.com>
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.
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.
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>
43 #define SHA512_Init SHA512Init
44 #define SHA512_Update SHA512Update
45 #define SHA512_Final SHA512Final
48 #include <sys/statfs.h>
49 #include <sys/loadavg.h>
52 #define min(a, b) (((a) < (b)) ? (a) : (b))
62 #define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
63 #define HD(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
64 #define HF(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (void*)))
66 int getentropy(void *buf, size_t len);
68 #ifdef CAN_REFERENCE_MAIN
69 extern int main(int, char *argv[]);
71 static int gotdata(char *buf, size_t len);
72 static int getentropy_urandom(void *buf, size_t len, const char *path,
74 static int getentropy_fallback(void *buf, size_t len);
77 getentropy(void *buf, size_t len)
87 * Try to get entropy with /dev/urandom
89 * Solaris provides /dev/urandom as a symbolic link to
90 * /devices/pseudo/random@0:urandom which is provided by
91 * a devfs filesystem. Best practice is to use O_NOFOLLOW,
92 * so we must try the unpublished name directly.
94 * This can fail if the process is inside a chroot which lacks
95 * the devfs mount, or if file descriptors are exhausted.
97 ret = getentropy_urandom(buf, len,
98 "/devices/pseudo/random@0:urandom", 1);
103 * Unfortunately, chroot spaces on Solaris are sometimes setup
104 * with direct device node of the well-known /dev/urandom name
105 * (perhaps to avoid dragging all of devfs into the space).
107 * This can fail if the process is inside a chroot or if file
108 * descriptors are exhausted.
110 ret = getentropy_urandom(buf, len, "/dev/urandom", 0);
115 * Entropy collection via /dev/urandom has failed.
117 * No other API exists for collecting entropy, and we have
118 * no failsafe way to get it on Solaris that is not sensitive
119 * to resource exhaustion.
121 * We have very few options:
122 * - Even syslog_r is unsafe to call at this low level, so
123 * there is no way to alert the user or program.
124 * - Cannot call abort() because some systems have unsafe
126 * - Could raise(SIGKILL) resulting in silent program termination.
127 * - Return EIO, to hint that arc4random's stir function
128 * should raise(SIGKILL)
129 * - Do the best under the circumstances....
131 * This code path exists to bring light to the issue that Solaris
132 * does not provide a failsafe API for entropy collection.
134 * We hope this demonstrates that Solaris should consider
135 * providing a new failsafe API which works in a chroot or
136 * when file descriptors are exhausted.
138 #undef FAIL_INSTEAD_OF_TRYING_FALLBACK
139 #ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
142 ret = getentropy_fallback(buf, len);
151 * Basic sanity checking; wish we could do better.
154 gotdata(char *buf, size_t len)
159 for (i = 0; i < len; ++i)
167 getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck)
172 int save_errno = errno;
183 fd = open(path, flags, 0);
190 fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
193 /* Lightly verify that the device node looks sane */
194 if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode) ||
195 (devfscheck && (strcmp(st.st_fstype, "devfs") != 0))) {
199 for (i = 0; i < len; ) {
200 size_t wanted = len - i;
201 ssize_t ret = read(fd, (char*)buf + i, wanted);
204 if (errno == EAGAIN || errno == EINTR)
212 if (gotdata(buf, len) == 0) {
214 return 0; /* satisfied */
221 static const int cl[] = {
223 #ifdef CLOCK_MONOTONIC
226 #ifdef CLOCK_MONOTONIC_RAW
238 #ifdef CLOCK_PROCESS_CPUTIME_ID
239 CLOCK_PROCESS_CPUTIME_ID,
241 #ifdef CLOCK_THREAD_CPUTIME_ID
242 CLOCK_THREAD_CPUTIME_ID,
247 getentropy_fallback(void *buf, size_t len)
249 uint8_t results[SHA512_DIGEST_LENGTH];
250 int save_errno = errno, e, pgs = getpagesize(), faster = 0, repeat;
259 static pid_t lastpid;
265 if (lastpid == pid) {
273 for (i = 0; i < len; ) {
276 for (j = 0; j < repeat; j++) {
277 HX((e = gettimeofday(&tv, NULL)) == -1, tv);
279 cnt += (int)tv.tv_sec;
280 cnt += (int)tv.tv_usec;
283 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
284 HX(clock_gettime(cl[ii], &ts) == -1, ts);
286 HX((pid = getpid()) == -1, pid);
287 HX((pid = getsid(pid)) == -1, pid);
288 HX((pid = getppid()) == -1, pid);
289 HX((pid = getpgid(0)) == -1, pid);
290 HX((e = getpriority(0, 0)) == -1, e);
291 HX((getloadavg(loadavg, 3) == -1), loadavg);
296 (void) nanosleep(&ts, NULL);
299 HX(sigpending(&sigset) == -1, sigset);
300 HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
303 #ifdef CAN_REFERENCE_MAIN
304 HF(main); /* an addr in program */
306 HF(getentropy); /* an addr in this library */
307 HF(printf); /* an addr in libc */
309 HD(p); /* an addr on stack */
311 HD(p); /* the addr of errno */
314 struct sockaddr_storage ss;
315 struct statvfs stvfs;
321 * Prime-sized mappings encourage fragmentation;
322 * thus exposing some address entropy.
328 { 17, MAP_FAILED }, { 3, MAP_FAILED },
329 { 11, MAP_FAILED }, { 2, MAP_FAILED },
330 { 5, MAP_FAILED }, { 3, MAP_FAILED },
331 { 7, MAP_FAILED }, { 1, MAP_FAILED },
332 { 57, MAP_FAILED }, { 3, MAP_FAILED },
333 { 131, MAP_FAILED }, { 1, MAP_FAILED },
336 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
337 HX(mm[m].p = mmap(NULL,
339 PROT_READ|PROT_WRITE,
340 MAP_PRIVATE|MAP_ANON, -1,
342 if (mm[m].p != MAP_FAILED) {
345 /* Touch some memory... */
348 (mm[m].npg * pgs - 1);
350 cnt += (int)((long)(mm[m].p)
354 /* Check cnts and times... */
355 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
357 HX((e = clock_gettime(cl[ii],
360 cnt += (int)ts.tv_nsec;
363 HX((e = getrusage(RUSAGE_SELF,
366 cnt += (int)ru.ru_utime.tv_sec;
367 cnt += (int)ru.ru_utime.tv_usec;
371 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
372 if (mm[m].p != MAP_FAILED)
373 munmap(mm[m].p, mm[m].npg * pgs);
374 mm[m].p = MAP_FAILED;
377 HX(stat(".", &st) == -1, st);
378 HX(statvfs(".", &stvfs) == -1, stvfs);
380 HX(stat("/", &st) == -1, st);
381 HX(statvfs("/", &stvfs) == -1, stvfs);
383 HX((e = fstat(0, &st)) == -1, st);
385 if (S_ISREG(st.st_mode) ||
386 S_ISFIFO(st.st_mode) ||
387 S_ISSOCK(st.st_mode)) {
388 HX(fstatvfs(0, &stvfs) == -1,
390 HX((off = lseek(0, (off_t)0,
391 SEEK_CUR)) < 0, off);
393 if (S_ISCHR(st.st_mode)) {
394 HX(tcgetattr(0, &tios) == -1,
396 } else if (S_ISSOCK(st.st_mode)) {
397 memset(&ss, 0, sizeof ss);
400 (void *)&ss, &ssl) == -1,
405 HX((e = getrusage(RUSAGE_CHILDREN,
408 cnt += (int)ru.ru_utime.tv_sec;
409 cnt += (int)ru.ru_utime.tv_usec;
412 /* Subsequent hashes absorb previous result */
416 HX((e = gettimeofday(&tv, NULL)) == -1, tv);
418 cnt += (int)tv.tv_sec;
419 cnt += (int)tv.tv_usec;
424 SHA512_Final(results, &ctx);
425 memcpy((char*)buf + i, results, min(sizeof(results), len - i));
426 i += min(sizeof(results), len - i);
428 memset(results, 0, sizeof results);
429 if (gotdata(buf, len) == 0) {
431 return 0; /* satisfied */