2 * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
15 #include "internal/cryptlib.h"
16 #include <openssl/rand.h>
18 #include "internal/rand_int.h"
20 #include "internal/dso.h"
22 # include <sys/syscall.h>
24 #if defined(__FreeBSD__)
25 # include <sys/types.h>
26 # include <sys/sysctl.h>
27 # include <sys/param.h>
29 #if defined(__OpenBSD__) || defined(__NetBSD__)
30 # include <sys/param.h>
33 #if defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__)
34 # include <sys/types.h>
35 # include <sys/stat.h>
38 # include <sys/time.h>
40 static uint64_t get_time_stamp(void);
41 static uint64_t get_timer_bits(void);
43 /* Macro to convert two thirty two bit values into a sixty four bit one */
44 # define TWO32TO64(a, b) ((((uint64_t)(a)) << 32) + (b))
47 * Check for the existence and support of POSIX timers. The standard
48 * says that the _POSIX_TIMERS macro will have a positive value if they
51 * However, we want an additional constraint: that the timer support does
52 * not require an extra library dependency. Early versions of glibc
53 * require -lrt to be specified on the link line to access the timers,
54 * so this needs to be checked for.
56 * It is worse because some libraries define __GLIBC__ but don't
57 * support the version testing macro (e.g. uClibc). This means
58 * an extra check is needed.
60 * The final condition is:
61 * "have posix timers and either not glibc or glibc without -lrt"
63 * The nested #if sequences are required to avoid using a parameterised
64 * macro that might be undefined.
66 # undef OSSL_POSIX_TIMER_OKAY
67 # if defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0
68 # if defined(__GLIBC__)
69 # if defined(__GLIBC_PREREQ)
70 # if __GLIBC_PREREQ(2, 17)
71 # define OSSL_POSIX_TIMER_OKAY
75 # define OSSL_POSIX_TIMER_OKAY
78 #endif /* defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__) */
80 #if defined(OPENSSL_RAND_SEED_NONE)
81 /* none means none. this simplifies the following logic */
82 # undef OPENSSL_RAND_SEED_OS
83 # undef OPENSSL_RAND_SEED_GETRANDOM
84 # undef OPENSSL_RAND_SEED_LIBRANDOM
85 # undef OPENSSL_RAND_SEED_DEVRANDOM
86 # undef OPENSSL_RAND_SEED_RDTSC
87 # undef OPENSSL_RAND_SEED_RDCPU
88 # undef OPENSSL_RAND_SEED_EGD
91 #if (defined(OPENSSL_SYS_VXWORKS) || defined(OPENSSL_SYS_UEFI)) && \
92 !defined(OPENSSL_RAND_SEED_NONE)
93 # error "UEFI and VXWorks only support seeding NONE"
96 #if !(defined(OPENSSL_SYS_WINDOWS) || defined(OPENSSL_SYS_WIN32) \
97 || defined(OPENSSL_SYS_VMS) || defined(OPENSSL_SYS_VXWORKS) \
98 || defined(OPENSSL_SYS_UEFI))
100 # if defined(OPENSSL_SYS_VOS)
102 # ifndef OPENSSL_RAND_SEED_OS
103 # error "Unsupported seeding method configured; must be os"
106 # if defined(OPENSSL_SYS_VOS_HPPA) && defined(OPENSSL_SYS_VOS_IA32)
107 # error "Unsupported HP-PA and IA32 at the same time."
109 # if !defined(OPENSSL_SYS_VOS_HPPA) && !defined(OPENSSL_SYS_VOS_IA32)
110 # error "Must have one of HP-PA or IA32"
114 * The following algorithm repeatedly samples the real-time clock (RTC) to
115 * generate a sequence of unpredictable data. The algorithm relies upon the
116 * uneven execution speed of the code (due to factors such as cache misses,
117 * interrupts, bus activity, and scheduling) and upon the rather large
118 * relative difference between the speed of the clock and the rate at which
119 * it can be read. If it is ported to an environment where execution speed
120 * is more constant or where the RTC ticks at a much slower rate, or the
121 * clock can be read with fewer instructions, it is likely that the results
122 * would be far more predictable. This should only be used for legacy
125 * As a precaution, we assume only 2 bits of entropy per byte.
127 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
134 # ifdef OPENSSL_SYS_VOS_HPPA
136 extern void s$sleep(long *_duration, short int *_code);
139 extern void s$sleep2(long long *_duration, short int *_code);
142 bytes_needed = rand_pool_bytes_needed(pool, 4 /*entropy_factor*/);
144 for (i = 0; i < bytes_needed; i++) {
146 * burn some cpu; hope for interrupts, cache collisions, bus
149 for (k = 0; k < 99; k++)
150 ts.tv_nsec = random();
152 # ifdef OPENSSL_SYS_VOS_HPPA
153 /* sleep for 1/1024 of a second (976 us). */
155 s$sleep(&duration, &code);
157 /* sleep for 1/65536 of a second (15 us). */
159 s$sleep2(&duration, &code);
162 /* Get wall clock time, take 8 bits. */
163 clock_gettime(CLOCK_REALTIME, &ts);
164 v = (unsigned char)(ts.tv_nsec & 0xFF);
165 rand_pool_add(pool, arg, &v, sizeof(v) , 2);
167 return rand_pool_entropy_available(pool);
170 void rand_pool_cleanup(void)
174 void rand_pool_keep_random_devices_open(int keep)
180 # if defined(OPENSSL_RAND_SEED_EGD) && \
181 (defined(OPENSSL_NO_EGD) || !defined(DEVRANDOM_EGD))
182 # error "Seeding uses EGD but EGD is turned off or no device given"
185 # if defined(OPENSSL_RAND_SEED_DEVRANDOM) && !defined(DEVRANDOM)
186 # error "Seeding uses urandom but DEVRANDOM is not configured"
189 # if defined(OPENSSL_RAND_SEED_OS)
190 # if !defined(DEVRANDOM)
191 # error "OS seeding requires DEVRANDOM to be configured"
193 # define OPENSSL_RAND_SEED_GETRANDOM
194 # define OPENSSL_RAND_SEED_DEVRANDOM
197 # if defined(OPENSSL_RAND_SEED_LIBRANDOM)
198 # error "librandom not (yet) supported"
201 # if (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
203 * sysctl_random(): Use sysctl() to read a random number from the kernel
204 * Returns the number of bytes returned in buf on success, -1 on failure.
206 static ssize_t sysctl_random(char *buf, size_t buflen)
213 * Note: sign conversion between size_t and ssize_t is safe even
214 * without a range check, see comment in syscall_random()
218 * On FreeBSD old implementations returned longs, newer versions support
219 * variable sizes up to 256 byte. The code below would not work properly
220 * when the sysctl returns long and we want to request something not a
221 * multiple of longs, which should never be the case.
223 if (!ossl_assert(buflen % sizeof(long) == 0)) {
229 * On NetBSD before 4.0 KERN_ARND was an alias for KERN_URND, and only
230 * filled in an int, leaving the rest uninitialized. Since NetBSD 4.0
231 * it returns a variable number of bytes with the current version supporting
233 * Just return an error on older NetBSD versions.
235 #if defined(__NetBSD__) && __NetBSD_Version__ < 400000000
245 if (sysctl(mib, 2, buf, &len, NULL, 0) == -1)
246 return done > 0 ? done : -1;
250 } while (buflen > 0);
256 # if defined(OPENSSL_RAND_SEED_GETRANDOM)
258 * syscall_random(): Try to get random data using a system call
259 * returns the number of bytes returned in buf, or < 0 on error.
261 static ssize_t syscall_random(void *buf, size_t buflen)
264 * Note: 'buflen' equals the size of the buffer which is used by the
265 * get_entropy() callback of the RAND_DRBG. It is roughly bounded by
267 * 2 * RAND_POOL_FACTOR * (RAND_DRBG_STRENGTH / 8) = 2^14
269 * which is way below the OSSL_SSIZE_MAX limit. Therefore sign conversion
270 * between size_t and ssize_t is safe even without a range check.
274 * Do runtime detection to find getentropy().
276 * Known OSs that should support this:
277 * - Darwin since 16 (OSX 10.12, IOS 10.0).
278 * - Solaris since 11.3
279 * - OpenBSD since 5.6
280 * - Linux since 3.17 with glibc 2.25
281 * - FreeBSD since 12.0 (1200061)
283 # if defined(__GNUC__) && __GNUC__>=2 && defined(__ELF__) && !defined(__hpux)
284 extern int getentropy(void *buffer, size_t length) __attribute__((weak));
286 if (getentropy != NULL)
287 return getentropy(buf, buflen) == 0 ? (ssize_t)buflen : -1;
291 int (*f)(void *buffer, size_t length);
295 * We could cache the result of the lookup, but we normally don't
296 * call this function often.
299 p_getentropy.p = DSO_global_lookup("getentropy");
301 if (p_getentropy.p != NULL)
302 return p_getentropy.f(buf, buflen) == 0 ? (ssize_t)buflen : -1;
305 /* Linux supports this since version 3.17 */
306 # if defined(__linux) && defined(SYS_getrandom)
307 return syscall(SYS_getrandom, buf, buflen, 0);
308 # elif (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
309 return sysctl_random(buf, buflen);
315 # endif /* defined(OPENSSL_RAND_SEED_GETRANDOM) */
317 # if defined(OPENSSL_RAND_SEED_DEVRANDOM)
318 static const char *random_device_paths[] = { DEVRANDOM };
319 static struct random_device {
325 } random_devices[OSSL_NELEM(random_device_paths)];
326 static int keep_random_devices_open = 1;
329 * Verify that the file descriptor associated with the random source is
330 * still valid. The rationale for doing this is the fact that it is not
331 * uncommon for daemons to close all open file handles when daemonizing.
332 * So the handle might have been closed or even reused for opening
335 static int check_random_device(struct random_device * rd)
340 && fstat(rd->fd, &st) != -1
341 && rd->dev == st.st_dev
342 && rd->ino == st.st_ino
343 && ((rd->mode ^ st.st_mode) & ~(S_IRWXU | S_IRWXG | S_IRWXO)) == 0
344 && rd->rdev == st.st_rdev;
348 * Open a random device if required and return its file descriptor or -1 on error
350 static int get_random_device(size_t n)
353 struct random_device * rd = &random_devices[n];
355 /* reuse existing file descriptor if it is (still) valid */
356 if (check_random_device(rd))
359 /* open the random device ... */
360 if ((rd->fd = open(random_device_paths[n], O_RDONLY)) == -1)
363 /* ... and cache its relevant stat(2) data */
364 if (fstat(rd->fd, &st) != -1) {
367 rd->mode = st.st_mode;
368 rd->rdev = st.st_rdev;
378 * Close a random device making sure it is a random device
380 static void close_random_device(size_t n)
382 struct random_device * rd = &random_devices[n];
384 if (check_random_device(rd))
389 static void open_random_devices(void)
393 for (i = 0; i < OSSL_NELEM(random_devices); i++)
394 (void)get_random_device(i);
397 int rand_pool_init(void)
401 for (i = 0; i < OSSL_NELEM(random_devices); i++)
402 random_devices[i].fd = -1;
403 open_random_devices();
407 void rand_pool_cleanup(void)
411 for (i = 0; i < OSSL_NELEM(random_devices); i++)
412 close_random_device(i);
415 void rand_pool_keep_random_devices_open(int keep)
418 open_random_devices();
421 keep_random_devices_open = keep;
424 # else /* !defined(OPENSSL_RAND_SEED_DEVRANDOM) */
426 int rand_pool_init(void)
431 void rand_pool_cleanup(void)
435 void rand_pool_keep_random_devices_open(int keep)
439 # endif /* defined(OPENSSL_RAND_SEED_DEVRANDOM) */
442 * Try the various seeding methods in turn, exit when successful.
444 * TODO(DRBG): If more than one entropy source is available, is it
445 * preferable to stop as soon as enough entropy has been collected
446 * (as favored by @rsalz) or should one rather be defensive and add
447 * more entropy than requested and/or from different sources?
449 * Currently, the user can select multiple entropy sources in the
450 * configure step, yet in practice only the first available source
451 * will be used. A more flexible solution has been requested, but
452 * currently it is not clear how this can be achieved without
453 * overengineering the problem. There are many parameters which
454 * could be taken into account when selecting the order and amount
455 * of input from the different entropy sources (trust, quality,
456 * possibility of blocking).
458 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
460 # if defined(OPENSSL_RAND_SEED_NONE)
461 return rand_pool_entropy_available(pool);
464 size_t entropy_available = 0;
465 unsigned char *buffer;
467 # if defined(OPENSSL_RAND_SEED_GETRANDOM)
470 /* Maximum allowed number of consecutive unsuccessful attempts */
473 bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
474 while (bytes_needed != 0 && attempts-- > 0) {
475 buffer = rand_pool_add_begin(pool, bytes_needed);
476 bytes = syscall_random(buffer, bytes_needed);
478 rand_pool_add_end(pool, bytes, 8 * bytes);
479 bytes_needed -= bytes;
480 attempts = 3; /* reset counter after successful attempt */
481 } else if (bytes < 0 && errno != EINTR) {
486 entropy_available = rand_pool_entropy_available(pool);
487 if (entropy_available > 0)
488 return entropy_available;
491 # if defined(OPENSSL_RAND_SEED_LIBRANDOM)
493 /* Not yet implemented. */
497 # if defined(OPENSSL_RAND_SEED_DEVRANDOM)
498 bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
502 for (i = 0; bytes_needed > 0 && i < OSSL_NELEM(random_device_paths); i++) {
504 /* Maximum allowed number of consecutive unsuccessful attempts */
506 const int fd = get_random_device(i);
511 while (bytes_needed != 0 && attempts-- > 0) {
512 buffer = rand_pool_add_begin(pool, bytes_needed);
513 bytes = read(fd, buffer, bytes_needed);
516 rand_pool_add_end(pool, bytes, 8 * bytes);
517 bytes_needed -= bytes;
518 attempts = 3; /* reset counter after successful attempt */
519 } else if (bytes < 0 && errno != EINTR) {
523 if (bytes < 0 || !keep_random_devices_open)
524 close_random_device(i);
526 bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
528 entropy_available = rand_pool_entropy_available(pool);
529 if (entropy_available > 0)
530 return entropy_available;
534 # if defined(OPENSSL_RAND_SEED_RDTSC)
535 entropy_available = rand_acquire_entropy_from_tsc(pool);
536 if (entropy_available > 0)
537 return entropy_available;
540 # if defined(OPENSSL_RAND_SEED_RDCPU)
541 entropy_available = rand_acquire_entropy_from_cpu(pool);
542 if (entropy_available > 0)
543 return entropy_available;
546 # if defined(OPENSSL_RAND_SEED_EGD)
547 bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
548 if (bytes_needed > 0) {
549 static const char *paths[] = { DEVRANDOM_EGD, NULL };
552 for (i = 0; paths[i] != NULL; i++) {
553 buffer = rand_pool_add_begin(pool, bytes_needed);
554 if (buffer != NULL) {
556 int num = RAND_query_egd_bytes(paths[i],
557 buffer, (int)bytes_needed);
558 if (num == (int)bytes_needed)
559 bytes = bytes_needed;
561 rand_pool_add_end(pool, bytes, 8 * bytes);
562 entropy_available = rand_pool_entropy_available(pool);
564 if (entropy_available > 0)
565 return entropy_available;
570 return rand_pool_entropy_available(pool);
576 #if defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__)
577 int rand_pool_add_nonce_data(RAND_POOL *pool)
581 CRYPTO_THREAD_ID tid;
586 * Add process id, thread id, and a high resolution timestamp to
587 * ensure that the nonce is unique with high probability for
588 * different process instances.
591 data.tid = CRYPTO_THREAD_get_current_id();
592 data.time = get_time_stamp();
594 return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
597 int rand_pool_add_additional_data(RAND_POOL *pool)
600 CRYPTO_THREAD_ID tid;
605 * Add some noise from the thread id and a high resolution timer.
606 * The thread id adds a little randomness if the drbg is accessed
607 * concurrently (which is the case for the <master> drbg).
609 data.tid = CRYPTO_THREAD_get_current_id();
610 data.time = get_timer_bits();
612 return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
617 * Get the current time with the highest possible resolution
619 * The time stamp is added to the nonce, so it is optimized for not repeating.
620 * The current time is ideal for this purpose, provided the computer's clock
623 static uint64_t get_time_stamp(void)
625 # if defined(OSSL_POSIX_TIMER_OKAY)
629 if (clock_gettime(CLOCK_REALTIME, &ts) == 0)
630 return TWO32TO64(ts.tv_sec, ts.tv_nsec);
633 # if defined(__unix__) \
634 || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
638 if (gettimeofday(&tv, NULL) == 0)
639 return TWO32TO64(tv.tv_sec, tv.tv_usec);
646 * Get an arbitrary timer value of the highest possible resolution
648 * The timer value is added as random noise to the additional data,
649 * which is not considered a trusted entropy sourec, so any result
652 static uint64_t get_timer_bits(void)
654 uint64_t res = OPENSSL_rdtsc();
659 # if defined(__sun) || defined(__hpux)
665 read_wall_time(&t, TIMEBASE_SZ);
666 return TWO32TO64(t.tb_high, t.tb_low);
668 # elif defined(OSSL_POSIX_TIMER_OKAY)
672 # ifdef CLOCK_BOOTTIME
673 # define CLOCK_TYPE CLOCK_BOOTTIME
674 # elif defined(_POSIX_MONOTONIC_CLOCK)
675 # define CLOCK_TYPE CLOCK_MONOTONIC
677 # define CLOCK_TYPE CLOCK_REALTIME
680 if (clock_gettime(CLOCK_TYPE, &ts) == 0)
681 return TWO32TO64(ts.tv_sec, ts.tv_nsec);
684 # if defined(__unix__) \
685 || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
689 if (gettimeofday(&tv, NULL) == 0)
690 return TWO32TO64(tv.tv_sec, tv.tv_usec);
695 #endif /* defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__) */