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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. */
#include <openssl/rand.h>
#if !defined(OPENSSL_WINDOWS)
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <openssl/thread.h>
#include <openssl/mem.h>
#include "internal.h"
#include "../internal.h"
/* This file implements a PRNG by reading from /dev/urandom, optionally with a
* buffer, which is unsafe across |fork|. */
#define BUF_SIZE 4096
/* rand_buffer contains unused, random bytes, some of which may have been
* consumed already. */
struct rand_buffer {
size_t used;
uint8_t rand[BUF_SIZE];
};
/* requested_lock is used to protect the |*_requested| variables. */
static struct CRYPTO_STATIC_MUTEX requested_lock = CRYPTO_STATIC_MUTEX_INIT;
/* urandom_fd_requested is set by |RAND_set_urandom_fd|. It's protected by
* |requested_lock|. */
static int urandom_fd_requested = -2;
/* urandom_fd is a file descriptor to /dev/urandom. It's protected by |once|. */
static int urandom_fd = -2;
/* urandom_buffering_requested is set by |RAND_enable_fork_unsafe_buffering|.
* It's protected by |requested_lock|. */
static int urandom_buffering_requested = 0;
/* urandom_buffering controls whether buffering is enabled (1) or not (0). This
* is protected by |once|. */
static int urandom_buffering = 0;
static CRYPTO_once_t once = CRYPTO_ONCE_INIT;
/* 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(&requested_lock);
urandom_buffering = urandom_buffering_requested;
int fd = urandom_fd_requested;
CRYPTO_STATIC_MUTEX_unlock(&requested_lock);
if (fd == -2) {
do {
fd = open("/dev/urandom", O_RDONLY);
} while (fd == -1 && errno == EINTR);
}
if (fd < 0) {
abort();
}
int flags = fcntl(fd, F_GETFD);
if (flags == -1) {
abort();
}
flags |= FD_CLOEXEC;
if (fcntl(fd, F_SETFD, flags) == -1) {
abort();
}
urandom_fd = fd;
}
void RAND_cleanup(void) {}
void RAND_set_urandom_fd(int fd) {
fd = dup(fd);
if (fd < 0) {
abort();
}
CRYPTO_STATIC_MUTEX_lock_write(&requested_lock);
urandom_fd_requested = fd;
CRYPTO_STATIC_MUTEX_unlock(&requested_lock);
CRYPTO_once(&once, init_once);
if (urandom_fd != fd) {
abort(); // Already initialized.
}
}
void RAND_enable_fork_unsafe_buffering(int fd) {
if (fd >= 0) {
fd = dup(fd);
if (fd < 0) {
abort();
}
} else {
fd = -2;
}
CRYPTO_STATIC_MUTEX_lock_write(&requested_lock);
urandom_buffering_requested = 1;
urandom_fd_requested = fd;
CRYPTO_STATIC_MUTEX_unlock(&requested_lock);
CRYPTO_once(&once, init_once);
if (urandom_buffering != 1 || (fd >= 0 && urandom_fd != fd)) {
abort(); // Already initialized.
}
}
static struct rand_buffer *get_thread_local_buffer(void) {
struct rand_buffer *buf =
CRYPTO_get_thread_local(OPENSSL_THREAD_LOCAL_URANDOM_BUF);
if (buf != NULL) {
return buf;
}
buf = OPENSSL_malloc(sizeof(struct rand_buffer));
if (buf == NULL) {
return NULL;
}
buf->used = BUF_SIZE; /* To trigger a |read_full| on first use. */
if (!CRYPTO_set_thread_local(OPENSSL_THREAD_LOCAL_URANDOM_BUF, buf,
OPENSSL_free)) {
OPENSSL_free(buf);
return NULL;
}
return buf;
}
/* read_full reads exactly |len| bytes from |fd| into |out| and returns 1. In
* the case of an error it returns 0. */
static char read_full(int fd, uint8_t *out, size_t len) {
ssize_t r;
while (len > 0) {
do {
r = read(fd, out, len);
} while (r == -1 && errno == EINTR);
if (r <= 0) {
return 0;
}
out += r;
len -= r;
}
return 1;
}
/* read_from_buffer reads |requested| random bytes from the buffer into |out|,
* refilling it if necessary to satisfy the request. */
static void read_from_buffer(struct rand_buffer *buf,
uint8_t *out, size_t requested) {
size_t remaining = BUF_SIZE - buf->used;
while (requested > remaining) {
memcpy(out, &buf->rand[buf->used], remaining);
buf->used += remaining;
out += remaining;
requested -= remaining;
if (!read_full(urandom_fd, buf->rand, BUF_SIZE)) {
abort();
return;
}
buf->used = 0;
remaining = BUF_SIZE;
}
memcpy(out, &buf->rand[buf->used], requested);
buf->used += requested;
}
/* CRYPTO_sysrand puts |requested| random bytes into |out|. */
void CRYPTO_sysrand(uint8_t *out, size_t requested) {
if (requested == 0) {
return;
}
CRYPTO_once(&once, init_once);
if (urandom_buffering && requested < BUF_SIZE) {
struct rand_buffer *buf = get_thread_local_buffer();
if (buf != NULL) {
read_from_buffer(buf, out, requested);
return;
}
}
if (!read_full(urandom_fd, out, requested)) {
abort();
}
}
#endif /* !OPENSSL_WINDOWS */