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/* SPDX-License-Identifier: LGPL-2.1+ */
/***
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd 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.
systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
#include "alloc-util.h"
#include "fd-util.h"
#include "io-util.h"
#include "log.h"
#include "mkdir.h"
#include "string-util.h"
#include "util.h"
#define POOL_SIZE_MIN 512
int main(int argc, char *argv[]) {
_cleanup_close_ int seed_fd = -1, random_fd = -1;
_cleanup_free_ void* buf = NULL;
size_t buf_size = 0;
ssize_t k;
int r, open_rw_error;
FILE *f;
bool refresh_seed_file = true;
if (argc != 2) {
log_error("This program requires one argument.");
return EXIT_FAILURE;
}
log_set_target(LOG_TARGET_AUTO);
log_parse_environment();
log_open();
umask(0022);
/* Read pool size, if possible */
f = fopen("/proc/sys/kernel/random/poolsize", "re");
if (f) {
if (fscanf(f, "%zu", &buf_size) > 0)
/* poolsize is in bits on 2.6, but we want bytes */
buf_size /= 8;
fclose(f);
}
if (buf_size <= POOL_SIZE_MIN)
buf_size = POOL_SIZE_MIN;
buf = malloc(buf_size);
if (!buf) {
r = log_oom();
goto finish;
}
r = mkdir_parents_label(RANDOM_SEED, 0755);
if (r < 0) {
log_error_errno(r, "Failed to create directory " RANDOM_SEED_DIR ": %m");
goto finish;
}
/* When we load the seed we read it and write it to the device
* and then immediately update the saved seed with new data,
* to make sure the next boot gets seeded differently. */
if (streq(argv[1], "load")) {
seed_fd = open(RANDOM_SEED, O_RDWR|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600);
open_rw_error = -errno;
if (seed_fd < 0) {
refresh_seed_file = false;
seed_fd = open(RANDOM_SEED, O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (seed_fd < 0) {
bool missing = errno == ENOENT;
log_full_errno(missing ? LOG_DEBUG : LOG_ERR,
open_rw_error, "Failed to open " RANDOM_SEED " for writing: %m");
r = log_full_errno(missing ? LOG_DEBUG : LOG_ERR,
errno, "Failed to open " RANDOM_SEED " for reading: %m");
if (missing)
r = 0;
goto finish;
}
}
random_fd = open("/dev/urandom", O_RDWR|O_CLOEXEC|O_NOCTTY, 0600);
if (random_fd < 0) {
random_fd = open("/dev/urandom", O_WRONLY|O_CLOEXEC|O_NOCTTY, 0600);
if (random_fd < 0) {
r = log_error_errno(errno, "Failed to open /dev/urandom: %m");
goto finish;
}
}
k = loop_read(seed_fd, buf, buf_size, false);
if (k < 0)
r = log_error_errno(k, "Failed to read seed from " RANDOM_SEED ": %m");
else if (k == 0) {
r = 0;
log_debug("Seed file " RANDOM_SEED " not yet initialized, proceeding.");
} else {
(void) lseek(seed_fd, 0, SEEK_SET);
r = loop_write(random_fd, buf, (size_t) k, false);
if (r < 0)
log_error_errno(r, "Failed to write seed to /dev/urandom: %m");
}
} else if (streq(argv[1], "save")) {
seed_fd = open(RANDOM_SEED, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600);
if (seed_fd < 0) {
r = log_error_errno(errno, "Failed to open " RANDOM_SEED ": %m");
goto finish;
}
random_fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (random_fd < 0) {
r = log_error_errno(errno, "Failed to open /dev/urandom: %m");
goto finish;
}
} else {
log_error("Unknown verb '%s'.", argv[1]);
r = -EINVAL;
goto finish;
}
if (refresh_seed_file) {
/* This is just a safety measure. Given that we are root and
* most likely created the file ourselves the mode and owner
* should be correct anyway. */
(void) fchmod(seed_fd, 0600);
(void) fchown(seed_fd, 0, 0);
k = loop_read(random_fd, buf, buf_size, false);
if (k < 0) {
r = log_error_errno(k, "Failed to read new seed from /dev/urandom: %m");
goto finish;
}
if (k == 0) {
log_error("Got EOF while reading from /dev/urandom.");
r = -EIO;
goto finish;
}
r = loop_write(seed_fd, buf, (size_t) k, false);
if (r < 0)
log_error_errno(r, "Failed to write new random seed file: %m");
}
finish:
return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}
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