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/*
* Copyright (C) 2010-2016 Free Software Foundation, Inc.
* Copyright (C) 2015-2016 Red Hat, Inc.
*
* Author: Nikos Mavrogiannopoulos
*
* This file is part of GNUTLS.
*
* The GNUTLS library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>
*
*/
/* The Linux style system random generator: That is,
* getrandom() -> /dev/urandom, where "->" indicates fallback.
*/
#ifndef RND_NO_INCLUDES
# include "gnutls_int.h"
# include "errors.h"
# include <num.h>
# include <errno.h>
# include <rnd-common.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
/* gnulib wants to claim strerror even if it cannot provide it. WTF */
#undef strerror
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <fcntl.h>
static int _gnutls_urandom_fd = -1;
static ino_t _gnutls_urandom_fd_ino = 0;
static dev_t _gnutls_urandom_fd_rdev = 0;
get_entropy_func _rnd_get_system_entropy = NULL;
#if defined(__linux__)
# ifdef HAVE_GETRANDOM
# include <sys/random.h>
# else
# include <sys/syscall.h>
# undef getrandom
# if defined(SYS_getrandom)
# define getrandom(dst,s,flags) syscall(SYS_getrandom, (void*)dst, (size_t)s, (unsigned int)flags)
# else
# define getrandom(dst,s,flags) -1
# endif
# endif
static unsigned have_getrandom(void)
{
char c;
int ret;
ret = getrandom(&c, 1, 1/*GRND_NONBLOCK*/);
if (ret == 1 || (ret == -1 && errno == EAGAIN))
return 1;
return 0;
}
/* returns exactly the amount of bytes requested */
static int force_getrandom(void *buf, size_t buflen, unsigned int flags)
{
int left = buflen;
int ret;
uint8_t *p = buf;
while (left > 0) {
ret = getrandom(p, left, flags);
if (ret == -1) {
if (errno != EINTR)
return ret;
}
if (ret > 0) {
left -= ret;
p += ret;
}
}
return buflen;
}
static int _rnd_get_system_entropy_getrandom(void* _rnd, size_t size)
{
int ret;
ret = force_getrandom(_rnd, size, 0);
if (ret == -1) {
int e = errno;
gnutls_assert();
_gnutls_debug_log
("Failed to use getrandom: %s\n",
strerror(e));
return GNUTLS_E_RANDOM_DEVICE_ERROR;
}
return 0;
}
#else /* not linux */
# define have_getrandom() 0
#endif
static int _rnd_get_system_entropy_urandom(void* _rnd, size_t size)
{
uint8_t* rnd = _rnd;
uint32_t done;
for (done = 0; done < size;) {
int res;
do {
res = read(_gnutls_urandom_fd, rnd + done, size - done);
} while (res < 0 && errno == EINTR);
if (res <= 0) {
int e = errno;
if (res < 0) {
_gnutls_debug_log
("Failed to read /dev/urandom: %s\n",
strerror(e));
} else {
_gnutls_debug_log
("Failed to read /dev/urandom: end of file\n");
}
return GNUTLS_E_RANDOM_DEVICE_ERROR;
}
done += res;
}
return 0;
}
/* This is called when gnutls_global_init() is called for second time.
* It must check whether any resources are still available.
* The particular problem it solves is to verify that the urandom fd is still
* open (for applications that for some reason closed all fds */
int _rnd_system_entropy_check(void)
{
int ret;
struct stat st;
if (_gnutls_urandom_fd == -1) /* not using urandom */
return 0;
ret = fstat(_gnutls_urandom_fd, &st);
if (ret < 0 || st.st_ino != _gnutls_urandom_fd_ino || st.st_rdev != _gnutls_urandom_fd_rdev) {
return _rnd_system_entropy_init();
}
return 0;
}
int _rnd_system_entropy_init(void)
{
int old;
struct stat st;
#if defined(__linux__)
/* Enable getrandom() usage if available */
if (have_getrandom()) {
_rnd_get_system_entropy = _rnd_get_system_entropy_getrandom;
_gnutls_debug_log("getrandom random generator was detected\n");
return 0;
}
#endif
/* First fallback: /dev/unrandom */
_gnutls_urandom_fd = open("/dev/urandom", O_RDONLY);
if (_gnutls_urandom_fd < 0) {
_gnutls_debug_log("Cannot open urandom!\n");
return gnutls_assert_val(GNUTLS_E_RANDOM_DEVICE_ERROR);
}
old = fcntl(_gnutls_urandom_fd, F_GETFD);
if (old != -1)
fcntl(_gnutls_urandom_fd, F_SETFD, old | FD_CLOEXEC);
if (fstat(_gnutls_urandom_fd, &st) >= 0) {
_gnutls_urandom_fd_ino = st.st_ino;
_gnutls_urandom_fd_rdev = st.st_rdev;
}
_rnd_get_system_entropy = _rnd_get_system_entropy_urandom;
return 0;
}
void _rnd_system_entropy_deinit(void)
{
if (_gnutls_urandom_fd >= 0) {
close(_gnutls_urandom_fd);
_gnutls_urandom_fd = -1;
}
}
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