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/* Copyright (c) 2014, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#if !defined(_GNU_SOURCE)
#define _GNU_SOURCE // needed for syscall() on Linux.
#endif
#include <openssl/rand.h>
#if !defined(OPENSSL_WINDOWS) && !defined(OPENSSL_FUCHSIA) && \
!defined(BORINGSSL_UNSAFE_DETERMINISTIC_MODE) && !defined(OPENSSL_TRUSTY)
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#if defined(OPENSSL_LINUX)
#if defined(BORINGSSL_FIPS)
#include <linux/random.h>
#include <sys/ioctl.h>
#endif
#include <sys/syscall.h>
#endif
#include <openssl/thread.h>
#include <openssl/mem.h>
#include "internal.h"
#include "../delocate.h"
#include "../../internal.h"
#if defined(OPENSSL_LINUX)
#if defined(OPENSSL_X86_64)
#define EXPECTED_NR_getrandom 318
#elif defined(OPENSSL_X86)
#define EXPECTED_NR_getrandom 355
#elif defined(OPENSSL_AARCH64)
#define EXPECTED_NR_getrandom 278
#elif defined(OPENSSL_ARM)
#define EXPECTED_NR_getrandom 384
#elif defined(OPENSSL_PPC64LE)
#define EXPECTED_NR_getrandom 359
#endif
#if defined(EXPECTED_NR_getrandom)
#define USE_NR_getrandom
#if defined(__NR_getrandom)
#if __NR_getrandom != EXPECTED_NR_getrandom
#error "system call number for getrandom is not the expected value"
#endif
#else // __NR_getrandom
#define __NR_getrandom EXPECTED_NR_getrandom
#endif // __NR_getrandom
#endif // EXPECTED_NR_getrandom
#if !defined(GRND_NONBLOCK)
#define GRND_NONBLOCK 1
#endif
#endif // OPENSSL_LINUX
// rand_lock is used to protect the |*_requested| variables.
DEFINE_STATIC_MUTEX(rand_lock);
// The following constants are magic values of |urandom_fd|.
static const int kUnset = 0;
static const int kHaveGetrandom = -3;
// urandom_fd_requested is set by |RAND_set_urandom_fd|. It's protected by
// |rand_lock|.
DEFINE_BSS_GET(int, urandom_fd_requested);
// urandom_fd is a file descriptor to /dev/urandom. It's protected by |once|.
DEFINE_BSS_GET(int, urandom_fd);
DEFINE_STATIC_ONCE(rand_once);
#if defined(USE_NR_getrandom) || defined(BORINGSSL_FIPS)
// message writes |msg| to stderr. We use this because referencing |stderr|
// with |fprintf| generates relocations, which is a problem inside the FIPS
// module.
static void message(const char *msg) {
ssize_t r;
do {
r = write(2, msg, strlen(msg));
} while (r == -1 && errno == EINTR);
}
#endif
// init_once initializes the state of this module to values previously
// requested. This is the only function that modifies |urandom_fd| and
// |urandom_buffering|, whose values may be read safely after calling the
// once.
static void init_once(void) {
CRYPTO_STATIC_MUTEX_lock_read(rand_lock_bss_get());
int fd = *urandom_fd_requested_bss_get();
CRYPTO_STATIC_MUTEX_unlock_read(rand_lock_bss_get());
#if defined(USE_NR_getrandom)
uint8_t dummy;
long getrandom_ret =
syscall(__NR_getrandom, &dummy, sizeof(dummy), GRND_NONBLOCK);
if (getrandom_ret == 1) {
*urandom_fd_bss_get() = kHaveGetrandom;
return;
} else if (getrandom_ret == -1 && errno == EAGAIN) {
message(
"getrandom indicates that the entropy pool has not been initialized. "
"Rather than continue with poor entropy, this process will block until "
"entropy is available.\n");
do {
getrandom_ret =
syscall(__NR_getrandom, &dummy, sizeof(dummy), 0 /* no flags */);
} while (getrandom_ret == -1 && errno == EINTR);
if (getrandom_ret == 1) {
*urandom_fd_bss_get() = kHaveGetrandom;
return;
}
}
#endif // USE_NR_getrandom
if (fd == kUnset) {
do {
fd = open("/dev/urandom", O_RDONLY);
} while (fd == -1 && errno == EINTR);
}
if (fd < 0) {
abort();
}
assert(kUnset == 0);
if (fd == kUnset) {
// Because we want to keep |urandom_fd| in the BSS, we have to initialise
// it to zero. But zero is a valid file descriptor too. Thus if open
// returns zero for /dev/urandom, we dup it to get a non-zero number.
fd = dup(fd);
close(kUnset);
if (fd <= 0) {
abort();
}
}
#if defined(BORINGSSL_FIPS)
// In FIPS mode we ensure that the kernel has sufficient entropy before
// continuing. This is automatically handled by getrandom, which requires
// that the entropy pool has been initialised, but for urandom we have to
// poll.
for (;;) {
int entropy_bits;
if (ioctl(fd, RNDGETENTCNT, &entropy_bits)) {
message(
"RNDGETENTCNT on /dev/urandom failed. We cannot continue in this "
"case when in FIPS mode.\n");
abort();
}
static const int kBitsNeeded = 256;
if (entropy_bits >= kBitsNeeded) {
break;
}
usleep(250000);
}
#endif
int flags = fcntl(fd, F_GETFD);
if (flags == -1) {
// Native Client doesn't implement |fcntl|.
if (errno != ENOSYS) {
abort();
}
} else {
flags |= FD_CLOEXEC;
if (fcntl(fd, F_SETFD, flags) == -1) {
abort();
}
}
*urandom_fd_bss_get() = fd;
}
void RAND_set_urandom_fd(int fd) {
fd = dup(fd);
if (fd < 0) {
abort();
}
assert(kUnset == 0);
if (fd == kUnset) {
// Because we want to keep |urandom_fd| in the BSS, we have to initialise
// it to zero. But zero is a valid file descriptor too. Thus if dup
// returned zero we dup it again to get a non-zero number.
fd = dup(fd);
close(kUnset);
if (fd <= 0) {
abort();
}
}
CRYPTO_STATIC_MUTEX_lock_write(rand_lock_bss_get());
*urandom_fd_requested_bss_get() = fd;
CRYPTO_STATIC_MUTEX_unlock_write(rand_lock_bss_get());
CRYPTO_once(rand_once_bss_get(), init_once);
if (*urandom_fd_bss_get() == kHaveGetrandom) {
close(fd);
} else if (*urandom_fd_bss_get() != fd) {
abort(); // Already initialized.
}
}
#if defined(USE_NR_getrandom) && defined(OPENSSL_MSAN)
void __msan_unpoison(void *, size_t);
#endif
// fill_with_entropy writes |len| bytes of entropy into |out|. It returns one
// on success and zero on error.
static char fill_with_entropy(uint8_t *out, size_t len) {
while (len > 0) {
ssize_t r;
if (*urandom_fd_bss_get() == kHaveGetrandom) {
#if defined(USE_NR_getrandom)
do {
r = syscall(__NR_getrandom, out, len, 0 /* no flags */);
} while (r == -1 && errno == EINTR);
#if defined(OPENSSL_MSAN)
if (r > 0) {
// MSAN doesn't recognise |syscall| and thus doesn't notice that we
// have initialised the output buffer.
__msan_unpoison(out, r);
}
#endif // OPENSSL_MSAN
#else // USE_NR_getrandom
abort();
#endif
} else {
do {
r = read(*urandom_fd_bss_get(), out, len);
} while (r == -1 && errno == EINTR);
}
if (r <= 0) {
return 0;
}
out += r;
len -= r;
}
return 1;
}
// CRYPTO_sysrand puts |requested| random bytes into |out|.
void CRYPTO_sysrand(uint8_t *out, size_t requested) {
if (requested == 0) {
return;
}
CRYPTO_once(rand_once_bss_get(), init_once);
if (!fill_with_entropy(out, requested)) {
abort();
}
#if defined(BORINGSSL_FIPS_BREAK_CRNG)
// This breaks the "continuous random number generator test" defined in FIPS
// 140-2, section 4.9.2, and implemented in rand_get_seed().
OPENSSL_memset(out, 0, requested);
#endif
}
#endif /* !OPENSSL_WINDOWS && !defined(OPENSSL_FUCHSIA) && \
!BORINGSSL_UNSAFE_DETERMINISTIC_MODE && !OPENSSL_TRUSTY */