2 * Copyright 1995-2020 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>
17 #include <openssl/crypto.h>
18 #include "rand_local.h"
19 #include "crypto/rand.h"
21 #include "internal/dso.h"
23 # include <sys/syscall.h>
24 # ifdef DEVRANDOM_WAIT
26 # include <sys/utsname.h>
29 #if defined(__FreeBSD__) && !defined(OPENSSL_SYS_UEFI)
30 # include <sys/types.h>
31 # include <sys/sysctl.h>
32 # include <sys/param.h>
34 #if defined(__OpenBSD__) || defined(__NetBSD__)
35 # include <sys/param.h>
38 #if defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__)
39 # include <sys/types.h>
40 # include <sys/stat.h>
43 # include <sys/time.h>
45 static uint64_t get_time_stamp(void);
46 static uint64_t get_timer_bits(void);
48 /* Macro to convert two thirty two bit values into a sixty four bit one */
49 # define TWO32TO64(a, b) ((((uint64_t)(a)) << 32) + (b))
52 * Check for the existence and support of POSIX timers. The standard
53 * says that the _POSIX_TIMERS macro will have a positive value if they
56 * However, we want an additional constraint: that the timer support does
57 * not require an extra library dependency. Early versions of glibc
58 * require -lrt to be specified on the link line to access the timers,
59 * so this needs to be checked for.
61 * It is worse because some libraries define __GLIBC__ but don't
62 * support the version testing macro (e.g. uClibc). This means
63 * an extra check is needed.
65 * The final condition is:
66 * "have posix timers and either not glibc or glibc without -lrt"
68 * The nested #if sequences are required to avoid using a parameterised
69 * macro that might be undefined.
71 # undef OSSL_POSIX_TIMER_OKAY
72 # if defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0
73 # if defined(__GLIBC__)
74 # if defined(__GLIBC_PREREQ)
75 # if __GLIBC_PREREQ(2, 17)
76 # define OSSL_POSIX_TIMER_OKAY
80 # define OSSL_POSIX_TIMER_OKAY
83 #endif /* (defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_SYS_VXWORKS))
84 || defined(__DJGPP__) */
86 #if defined(OPENSSL_RAND_SEED_NONE)
87 /* none means none. this simplifies the following logic */
88 # undef OPENSSL_RAND_SEED_OS
89 # undef OPENSSL_RAND_SEED_GETRANDOM
90 # undef OPENSSL_RAND_SEED_LIBRANDOM
91 # undef OPENSSL_RAND_SEED_DEVRANDOM
92 # undef OPENSSL_RAND_SEED_RDTSC
93 # undef OPENSSL_RAND_SEED_RDCPU
94 # undef OPENSSL_RAND_SEED_EGD
97 #if (defined(OPENSSL_SYS_VXWORKS) || defined(OPENSSL_SYS_UEFI)) && \
98 !defined(OPENSSL_RAND_SEED_NONE)
99 # error "UEFI and VXWorks only support seeding NONE"
102 #if defined(OPENSSL_SYS_VXWORKS)
103 /* empty implementation */
104 int rand_pool_init(void)
109 void rand_pool_cleanup(void)
113 void rand_pool_keep_random_devices_open(int keep)
117 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
119 return rand_pool_entropy_available(pool);
123 #if !(defined(OPENSSL_SYS_WINDOWS) || defined(OPENSSL_SYS_WIN32) \
124 || defined(OPENSSL_SYS_VMS) || defined(OPENSSL_SYS_VXWORKS) \
125 || defined(OPENSSL_SYS_UEFI))
127 # if defined(OPENSSL_SYS_VOS)
129 # ifndef OPENSSL_RAND_SEED_OS
130 # error "Unsupported seeding method configured; must be os"
133 # if defined(OPENSSL_SYS_VOS_HPPA) && defined(OPENSSL_SYS_VOS_IA32)
134 # error "Unsupported HP-PA and IA32 at the same time."
136 # if !defined(OPENSSL_SYS_VOS_HPPA) && !defined(OPENSSL_SYS_VOS_IA32)
137 # error "Must have one of HP-PA or IA32"
141 * The following algorithm repeatedly samples the real-time clock (RTC) to
142 * generate a sequence of unpredictable data. The algorithm relies upon the
143 * uneven execution speed of the code (due to factors such as cache misses,
144 * interrupts, bus activity, and scheduling) and upon the rather large
145 * relative difference between the speed of the clock and the rate at which
146 * it can be read. If it is ported to an environment where execution speed
147 * is more constant or where the RTC ticks at a much slower rate, or the
148 * clock can be read with fewer instructions, it is likely that the results
149 * would be far more predictable. This should only be used for legacy
152 * As a precaution, we assume only 2 bits of entropy per byte.
154 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
161 # ifdef OPENSSL_SYS_VOS_HPPA
163 extern void s$sleep(long *_duration, short int *_code);
166 extern void s$sleep2(long long *_duration, short int *_code);
169 bytes_needed = rand_pool_bytes_needed(pool, 4 /*entropy_factor*/);
171 for (i = 0; i < bytes_needed; i++) {
173 * burn some cpu; hope for interrupts, cache collisions, bus
176 for (k = 0; k < 99; k++)
177 ts.tv_nsec = random();
179 # ifdef OPENSSL_SYS_VOS_HPPA
180 /* sleep for 1/1024 of a second (976 us). */
182 s$sleep(&duration, &code);
184 /* sleep for 1/65536 of a second (15 us). */
186 s$sleep2(&duration, &code);
189 /* Get wall clock time, take 8 bits. */
190 clock_gettime(CLOCK_REALTIME, &ts);
191 v = (unsigned char)(ts.tv_nsec & 0xFF);
192 rand_pool_add(pool, arg, &v, sizeof(v) , 2);
194 return rand_pool_entropy_available(pool);
197 void rand_pool_cleanup(void)
201 void rand_pool_keep_random_devices_open(int keep)
207 # if defined(OPENSSL_RAND_SEED_EGD) && \
208 (defined(OPENSSL_NO_EGD) || !defined(DEVRANDOM_EGD))
209 # error "Seeding uses EGD but EGD is turned off or no device given"
212 # if defined(OPENSSL_RAND_SEED_DEVRANDOM) && !defined(DEVRANDOM)
213 # error "Seeding uses urandom but DEVRANDOM is not configured"
216 # if defined(OPENSSL_RAND_SEED_OS)
217 # if !defined(DEVRANDOM)
218 # error "OS seeding requires DEVRANDOM to be configured"
220 # define OPENSSL_RAND_SEED_GETRANDOM
221 # define OPENSSL_RAND_SEED_DEVRANDOM
224 # if defined(OPENSSL_RAND_SEED_LIBRANDOM)
225 # error "librandom not (yet) supported"
228 # if (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
230 * sysctl_random(): Use sysctl() to read a random number from the kernel
231 * Returns the number of bytes returned in buf on success, -1 on failure.
233 static ssize_t sysctl_random(char *buf, size_t buflen)
240 * Note: sign conversion between size_t and ssize_t is safe even
241 * without a range check, see comment in syscall_random()
245 * On FreeBSD old implementations returned longs, newer versions support
246 * variable sizes up to 256 byte. The code below would not work properly
247 * when the sysctl returns long and we want to request something not a
248 * multiple of longs, which should never be the case.
250 if (!ossl_assert(buflen % sizeof(long) == 0)) {
256 * On NetBSD before 4.0 KERN_ARND was an alias for KERN_URND, and only
257 * filled in an int, leaving the rest uninitialized. Since NetBSD 4.0
258 * it returns a variable number of bytes with the current version supporting
260 * Just return an error on older NetBSD versions.
262 #if defined(__NetBSD__) && __NetBSD_Version__ < 400000000
272 if (sysctl(mib, 2, buf, &len, NULL, 0) == -1)
273 return done > 0 ? done : -1;
277 } while (buflen > 0);
283 # if defined(OPENSSL_RAND_SEED_GETRANDOM)
285 # if defined(__linux) && !defined(__NR_getrandom)
286 # if defined(__arm__)
287 # define __NR_getrandom (__NR_SYSCALL_BASE+384)
288 # elif defined(__i386__)
289 # define __NR_getrandom 355
290 # elif defined(__x86_64__)
291 # if defined(__ILP32__)
292 # define __NR_getrandom (__X32_SYSCALL_BIT + 318)
294 # define __NR_getrandom 318
296 # elif defined(__xtensa__)
297 # define __NR_getrandom 338
298 # elif defined(__s390__) || defined(__s390x__)
299 # define __NR_getrandom 349
300 # elif defined(__bfin__)
301 # define __NR_getrandom 389
302 # elif defined(__powerpc__)
303 # define __NR_getrandom 359
304 # elif defined(__mips__) || defined(__mips64)
305 # if _MIPS_SIM == _MIPS_SIM_ABI32
306 # define __NR_getrandom (__NR_Linux + 353)
307 # elif _MIPS_SIM == _MIPS_SIM_ABI64
308 # define __NR_getrandom (__NR_Linux + 313)
309 # elif _MIPS_SIM == _MIPS_SIM_NABI32
310 # define __NR_getrandom (__NR_Linux + 317)
312 # elif defined(__hppa__)
313 # define __NR_getrandom (__NR_Linux + 339)
314 # elif defined(__sparc__)
315 # define __NR_getrandom 347
316 # elif defined(__ia64__)
317 # define __NR_getrandom 1339
318 # elif defined(__alpha__)
319 # define __NR_getrandom 511
320 # elif defined(__sh__)
321 # if defined(__SH5__)
322 # define __NR_getrandom 373
324 # define __NR_getrandom 384
326 # elif defined(__avr32__)
327 # define __NR_getrandom 317
328 # elif defined(__microblaze__)
329 # define __NR_getrandom 385
330 # elif defined(__m68k__)
331 # define __NR_getrandom 352
332 # elif defined(__cris__)
333 # define __NR_getrandom 356
334 # elif defined(__aarch64__)
335 # define __NR_getrandom 278
337 # define __NR_getrandom 278
342 * syscall_random(): Try to get random data using a system call
343 * returns the number of bytes returned in buf, or < 0 on error.
345 static ssize_t syscall_random(void *buf, size_t buflen)
348 * Note: 'buflen' equals the size of the buffer which is used by the
349 * get_entropy() callback of the RAND_DRBG. It is roughly bounded by
351 * 2 * RAND_POOL_FACTOR * (RAND_DRBG_STRENGTH / 8) = 2^14
353 * which is way below the OSSL_SSIZE_MAX limit. Therefore sign conversion
354 * between size_t and ssize_t is safe even without a range check.
358 * Do runtime detection to find getentropy().
360 * Known OSs that should support this:
361 * - Darwin since 16 (OSX 10.12, IOS 10.0).
362 * - Solaris since 11.3
363 * - OpenBSD since 5.6
364 * - Linux since 3.17 with glibc 2.25
365 * - FreeBSD since 12.0 (1200061)
367 # if defined(__GNUC__) && __GNUC__>=2 && defined(__ELF__) && !defined(__hpux)
368 extern int getentropy(void *buffer, size_t length) __attribute__((weak));
370 if (getentropy != NULL)
371 return getentropy(buf, buflen) == 0 ? (ssize_t)buflen : -1;
375 int (*f)(void *buffer, size_t length);
379 * We could cache the result of the lookup, but we normally don't
380 * call this function often.
383 p_getentropy.p = DSO_global_lookup("getentropy");
385 if (p_getentropy.p != NULL)
386 return p_getentropy.f(buf, buflen) == 0 ? (ssize_t)buflen : -1;
389 /* Linux supports this since version 3.17 */
390 # if defined(__linux) && defined(__NR_getrandom)
391 return syscall(__NR_getrandom, buf, buflen, 0);
392 # elif (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
393 return sysctl_random(buf, buflen);
399 # endif /* defined(OPENSSL_RAND_SEED_GETRANDOM) */
401 # if defined(OPENSSL_RAND_SEED_DEVRANDOM)
402 static const char *random_device_paths[] = { DEVRANDOM };
403 static struct random_device {
409 } random_devices[OSSL_NELEM(random_device_paths)];
410 static int keep_random_devices_open = 1;
412 # if defined(__linux) && defined(DEVRANDOM_WAIT)
413 static void *shm_addr;
415 static void cleanup_shm(void)
421 * Ensure that the system randomness source has been adequately seeded.
422 * This is done by having the first start of libcrypto, wait until the device
423 * /dev/random becomes able to supply a byte of entropy. Subsequent starts
424 * of the library and later reseedings do not need to do this.
426 static int wait_random_seeded(void)
428 static int seeded = OPENSSL_RAND_SEED_DEVRANDOM_SHM_ID < 0;
429 static const int kernel_version[] = { DEVRANDOM_SAFE_KERNEL };
437 /* See if anything has created the global seeded indication */
438 if ((shm_id = shmget(OPENSSL_RAND_SEED_DEVRANDOM_SHM_ID, 1, 0)) == -1) {
440 * Check the kernel's version and fail if it is too recent.
442 * Linux kernels from 4.8 onwards do not guarantee that
443 * /dev/urandom is properly seeded when /dev/random becomes
444 * readable. However, such kernels support the getentropy(2)
445 * system call and this should always succeed which renders
446 * this alternative but essentially identical source moot.
448 if (uname(&un) == 0) {
449 kernel[0] = atoi(un.release);
450 p = strchr(un.release, '.');
451 kernel[1] = p == NULL ? 0 : atoi(p + 1);
452 if (kernel[0] > kernel_version[0]
453 || (kernel[0] == kernel_version[0]
454 && kernel[1] >= kernel_version[1])) {
458 /* Open /dev/random and wait for it to be readable */
459 if ((fd = open(DEVRANDOM_WAIT, O_RDONLY)) != -1) {
460 if (DEVRANDM_WAIT_USE_SELECT && fd < FD_SETSIZE) {
463 while ((r = select(fd + 1, &fds, NULL, NULL, NULL)) < 0
466 while ((r = read(fd, &c, 1)) < 0 && errno == EINTR);
471 /* Create the shared memory indicator */
472 shm_id = shmget(OPENSSL_RAND_SEED_DEVRANDOM_SHM_ID, 1,
473 IPC_CREAT | S_IRUSR | S_IRGRP | S_IROTH);
480 * Map the shared memory to prevent its premature destruction.
481 * If this call fails, it isn't a big problem.
483 shm_addr = shmat(shm_id, NULL, SHM_RDONLY);
484 if (shm_addr != (void *)-1)
485 OPENSSL_atexit(&cleanup_shm);
490 # else /* defined __linux */
491 static int wait_random_seeded(void)
498 * Verify that the file descriptor associated with the random source is
499 * still valid. The rationale for doing this is the fact that it is not
500 * uncommon for daemons to close all open file handles when daemonizing.
501 * So the handle might have been closed or even reused for opening
504 static int check_random_device(struct random_device * rd)
509 && fstat(rd->fd, &st) != -1
510 && rd->dev == st.st_dev
511 && rd->ino == st.st_ino
512 && ((rd->mode ^ st.st_mode) & ~(S_IRWXU | S_IRWXG | S_IRWXO)) == 0
513 && rd->rdev == st.st_rdev;
517 * Open a random device if required and return its file descriptor or -1 on error
519 static int get_random_device(size_t n)
522 struct random_device * rd = &random_devices[n];
524 /* reuse existing file descriptor if it is (still) valid */
525 if (check_random_device(rd))
528 /* open the random device ... */
529 if ((rd->fd = open(random_device_paths[n], O_RDONLY)) == -1)
532 /* ... and cache its relevant stat(2) data */
533 if (fstat(rd->fd, &st) != -1) {
536 rd->mode = st.st_mode;
537 rd->rdev = st.st_rdev;
547 * Close a random device making sure it is a random device
549 static void close_random_device(size_t n)
551 struct random_device * rd = &random_devices[n];
553 if (check_random_device(rd))
558 int rand_pool_init(void)
562 for (i = 0; i < OSSL_NELEM(random_devices); i++)
563 random_devices[i].fd = -1;
568 void rand_pool_cleanup(void)
572 for (i = 0; i < OSSL_NELEM(random_devices); i++)
573 close_random_device(i);
576 void rand_pool_keep_random_devices_open(int keep)
581 keep_random_devices_open = keep;
584 # else /* !defined(OPENSSL_RAND_SEED_DEVRANDOM) */
586 int rand_pool_init(void)
591 void rand_pool_cleanup(void)
595 void rand_pool_keep_random_devices_open(int keep)
599 # endif /* defined(OPENSSL_RAND_SEED_DEVRANDOM) */
602 * Try the various seeding methods in turn, exit when successful.
604 * TODO(DRBG): If more than one entropy source is available, is it
605 * preferable to stop as soon as enough entropy has been collected
606 * (as favored by @rsalz) or should one rather be defensive and add
607 * more entropy than requested and/or from different sources?
609 * Currently, the user can select multiple entropy sources in the
610 * configure step, yet in practice only the first available source
611 * will be used. A more flexible solution has been requested, but
612 * currently it is not clear how this can be achieved without
613 * overengineering the problem. There are many parameters which
614 * could be taken into account when selecting the order and amount
615 * of input from the different entropy sources (trust, quality,
616 * possibility of blocking).
618 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
620 # if defined(OPENSSL_RAND_SEED_NONE)
621 return rand_pool_entropy_available(pool);
623 size_t entropy_available;
625 # if defined(OPENSSL_RAND_SEED_GETRANDOM)
628 unsigned char *buffer;
630 /* Maximum allowed number of consecutive unsuccessful attempts */
633 bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
634 while (bytes_needed != 0 && attempts-- > 0) {
635 buffer = rand_pool_add_begin(pool, bytes_needed);
636 bytes = syscall_random(buffer, bytes_needed);
638 rand_pool_add_end(pool, bytes, 8 * bytes);
639 bytes_needed -= bytes;
640 attempts = 3; /* reset counter after successful attempt */
641 } else if (bytes < 0 && errno != EINTR) {
646 entropy_available = rand_pool_entropy_available(pool);
647 if (entropy_available > 0)
648 return entropy_available;
651 # if defined(OPENSSL_RAND_SEED_LIBRANDOM)
653 /* Not yet implemented. */
657 # if defined(OPENSSL_RAND_SEED_DEVRANDOM)
658 if (wait_random_seeded()) {
660 unsigned char *buffer;
663 bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
664 for (i = 0; bytes_needed > 0 && i < OSSL_NELEM(random_device_paths);
667 /* Maximum number of consecutive unsuccessful attempts */
669 const int fd = get_random_device(i);
674 while (bytes_needed != 0 && attempts-- > 0) {
675 buffer = rand_pool_add_begin(pool, bytes_needed);
676 bytes = read(fd, buffer, bytes_needed);
679 rand_pool_add_end(pool, bytes, 8 * bytes);
680 bytes_needed -= bytes;
681 attempts = 3; /* reset counter on successful attempt */
682 } else if (bytes < 0 && errno != EINTR) {
686 if (bytes < 0 || !keep_random_devices_open)
687 close_random_device(i);
689 bytes_needed = rand_pool_bytes_needed(pool, 1);
691 entropy_available = rand_pool_entropy_available(pool);
692 if (entropy_available > 0)
693 return entropy_available;
697 # if defined(OPENSSL_RAND_SEED_RDTSC)
698 entropy_available = rand_acquire_entropy_from_tsc(pool);
699 if (entropy_available > 0)
700 return entropy_available;
703 # if defined(OPENSSL_RAND_SEED_RDCPU)
704 entropy_available = rand_acquire_entropy_from_cpu(pool);
705 if (entropy_available > 0)
706 return entropy_available;
709 # if defined(OPENSSL_RAND_SEED_EGD)
711 static const char *paths[] = { DEVRANDOM_EGD, NULL };
713 unsigned char *buffer;
716 bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
717 for (i = 0; bytes_needed > 0 && paths[i] != NULL; i++) {
721 buffer = rand_pool_add_begin(pool, bytes_needed);
722 num = RAND_query_egd_bytes(paths[i],
723 buffer, (int)bytes_needed);
724 if (num == (int)bytes_needed)
725 bytes = bytes_needed;
727 rand_pool_add_end(pool, bytes, 8 * bytes);
728 bytes_needed = rand_pool_bytes_needed(pool, 1);
730 entropy_available = rand_pool_entropy_available(pool);
731 if (entropy_available > 0)
732 return entropy_available;
736 return rand_pool_entropy_available(pool);
742 #if defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__)
743 int rand_pool_add_nonce_data(RAND_POOL *pool)
747 CRYPTO_THREAD_ID tid;
752 * Add process id, thread id, and a high resolution timestamp to
753 * ensure that the nonce is unique with high probability for
754 * different process instances.
757 data.tid = CRYPTO_THREAD_get_current_id();
758 data.time = get_time_stamp();
760 return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
763 int rand_pool_add_additional_data(RAND_POOL *pool)
767 CRYPTO_THREAD_ID tid;
772 * Add some noise from the thread id and a high resolution timer.
773 * The fork_id adds some extra fork-safety.
774 * The thread id adds a little randomness if the drbg is accessed
775 * concurrently (which is the case for the <master> drbg).
777 data.fork_id = openssl_get_fork_id();
778 data.tid = CRYPTO_THREAD_get_current_id();
779 data.time = get_timer_bits();
781 return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
786 * Get the current time with the highest possible resolution
788 * The time stamp is added to the nonce, so it is optimized for not repeating.
789 * The current time is ideal for this purpose, provided the computer's clock
792 static uint64_t get_time_stamp(void)
794 # if defined(OSSL_POSIX_TIMER_OKAY)
798 if (clock_gettime(CLOCK_REALTIME, &ts) == 0)
799 return TWO32TO64(ts.tv_sec, ts.tv_nsec);
802 # if defined(__unix__) \
803 || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
807 if (gettimeofday(&tv, NULL) == 0)
808 return TWO32TO64(tv.tv_sec, tv.tv_usec);
815 * Get an arbitrary timer value of the highest possible resolution
817 * The timer value is added as random noise to the additional data,
818 * which is not considered a trusted entropy sourec, so any result
821 static uint64_t get_timer_bits(void)
823 uint64_t res = OPENSSL_rdtsc();
828 # if defined(__sun) || defined(__hpux)
834 read_wall_time(&t, TIMEBASE_SZ);
835 return TWO32TO64(t.tb_high, t.tb_low);
837 # elif defined(OSSL_POSIX_TIMER_OKAY)
841 # ifdef CLOCK_BOOTTIME
842 # define CLOCK_TYPE CLOCK_BOOTTIME
843 # elif defined(_POSIX_MONOTONIC_CLOCK)
844 # define CLOCK_TYPE CLOCK_MONOTONIC
846 # define CLOCK_TYPE CLOCK_REALTIME
849 if (clock_gettime(CLOCK_TYPE, &ts) == 0)
850 return TWO32TO64(ts.tv_sec, ts.tv_nsec);
853 # if defined(__unix__) \
854 || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
858 if (gettimeofday(&tv, NULL) == 0)
859 return TWO32TO64(tv.tv_sec, tv.tv_usec);
864 #endif /* (defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_SYS_VXWORKS))
865 || defined(__DJGPP__) */