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/*
* cryptsetup kernel RNG access functions
*
* Copyright (C) 2010-2021 Red Hat, Inc. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <sys/select.h>
#include "libcryptsetup.h"
#include "internal.h"
static int random_initialised = 0;
#define URANDOM_DEVICE "/dev/urandom"
static int urandom_fd = -1;
#define RANDOM_DEVICE "/dev/random"
static int random_fd = -1;
/* Read random chunk - gathered data usually appears with this granularity */
#define RANDOM_DEVICE_CHUNK 8
/* Timeout to print warning if no random data (entropy) */
#define RANDOM_DEVICE_TIMEOUT 5
/* URANDOM_DEVICE access */
static int _get_urandom(struct crypt_device *ctx __attribute__((unused)),
char *buf, size_t len)
{
int r;
size_t old_len = len;
char *old_buf = buf;
assert(urandom_fd != -1);
while(len) {
r = read(urandom_fd, buf, len);
if (r == -1 && errno != EINTR)
return -EINVAL;
if (r > 0) {
len -= r;
buf += r;
}
}
assert(len == 0);
assert((size_t)(buf - old_buf) == old_len);
return 0;
}
static void _get_random_progress(struct crypt_device *ctx, int warn,
size_t expected_len, size_t read_len)
{
if (warn)
log_std(ctx,
_("System is out of entropy while generating volume key.\n"
"Please move mouse or type some text in another window "
"to gather some random events.\n"));
log_std(ctx, _("Generating key (%d%% done).\n"),
(int)((expected_len - read_len) * 100 / expected_len));
}
/* RANDOM_DEVICE access */
static int _get_random(struct crypt_device *ctx, char *buf, size_t len)
{
int r, warn_once = 1;
size_t n, old_len = len;
char *old_buf = buf;
fd_set fds;
struct timeval tv;
assert(random_fd != -1);
while (len) {
FD_ZERO(&fds);
FD_SET(random_fd, &fds);
tv.tv_sec = RANDOM_DEVICE_TIMEOUT;
tv.tv_usec = 0;
r = select(random_fd + 1, &fds, NULL, NULL, &tv);
if(r == -1)
return -EINVAL;
if(!r) {
_get_random_progress(ctx, warn_once, old_len, len);
warn_once = 0;
continue;
}
do {
n = RANDOM_DEVICE_CHUNK;
if (len < RANDOM_DEVICE_CHUNK)
n = len;
r = read(random_fd, buf, n);
if (r == -1 && errno == EINTR) {
r = 0;
continue;
}
/* bogus read? */
if(r > (int)n)
return -EINVAL;
/* random device is opened with O_NONBLOCK, EAGAIN is expected */
if (r == -1 && (errno != EAGAIN && errno != EWOULDBLOCK))
return -EINVAL;
if (r > 0) {
len -= r;
buf += r;
}
} while (len && r > 0);
}
assert(len == 0);
assert((size_t)(buf - old_buf) == old_len);
if (!warn_once)
_get_random_progress(ctx, 0, old_len, len);
return 0;
}
/* Initialisation of both RNG file descriptors is mandatory */
int crypt_random_init(struct crypt_device *ctx)
{
if (random_initialised)
return 0;
/* Used for CRYPT_RND_NORMAL */
if(urandom_fd == -1)
urandom_fd = open(URANDOM_DEVICE, O_RDONLY | O_CLOEXEC);
if(urandom_fd == -1)
goto fail;
/* Used for CRYPT_RND_KEY */
if(random_fd == -1)
random_fd = open(RANDOM_DEVICE, O_RDONLY | O_NONBLOCK | O_CLOEXEC);
if(random_fd == -1)
goto fail;
if (crypt_fips_mode())
log_verbose(ctx, _("Running in FIPS mode."));
random_initialised = 1;
return 0;
fail:
crypt_random_exit();
log_err(ctx, _("Fatal error during RNG initialisation."));
return -ENOSYS;
}
int crypt_random_get(struct crypt_device *ctx, char *buf, size_t len, int quality)
{
int status, rng_type;
switch(quality) {
case CRYPT_RND_NORMAL:
status = _get_urandom(ctx, buf, len);
break;
case CRYPT_RND_SALT:
if (crypt_fips_mode())
status = crypt_backend_rng(buf, len, quality, 1);
else
status = _get_urandom(ctx, buf, len);
break;
case CRYPT_RND_KEY:
if (crypt_fips_mode()) {
status = crypt_backend_rng(buf, len, quality, 1);
break;
}
rng_type = ctx ? crypt_get_rng_type(ctx) :
crypt_random_default_key_rng();
switch (rng_type) {
case CRYPT_RNG_URANDOM:
status = _get_urandom(ctx, buf, len);
break;
case CRYPT_RNG_RANDOM:
status = _get_random(ctx, buf, len);
break;
default:
abort();
}
break;
default:
log_err(ctx, _("Unknown RNG quality requested."));
return -EINVAL;
}
if (status)
log_err(ctx, _("Error reading from RNG."));
return status;
}
void crypt_random_exit(void)
{
random_initialised = 0;
if(random_fd != -1) {
(void)close(random_fd);
random_fd = -1;
}
if(urandom_fd != -1) {
(void)close(urandom_fd);
urandom_fd = -1;
}
}
int crypt_random_default_key_rng(void)
{
/* coverity[pointless_string_compare] */
if (!strcmp(DEFAULT_RNG, RANDOM_DEVICE))
return CRYPT_RNG_RANDOM;
/* coverity[pointless_string_compare] */
if (!strcmp(DEFAULT_RNG, URANDOM_DEVICE))
return CRYPT_RNG_URANDOM;
/* RNG misconfiguration is fatal */
abort();
}
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