machine-id-setup.c revision 81527be142678057215665be66e4b3c8306a7ab3
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
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 General Public License as published by
the Free Software Foundation; either version 2 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
General Public License for more details.
You should have received a copy of the GNU General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mount.h>
#include <systemd/sd-id128.h>
#include "machine-id-setup.h"
#include "macro.h"
#include "util.h"
#include "log.h"
static int generate(char id[34]) {
int fd, r;
unsigned char *p;
sd_id128_t buf;
char *q;
ssize_t k;
assert(id);
/* First, try reading the D-Bus machine id, unless it is a symlink */
fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
if (fd >= 0) {
k = loop_read(fd, id, 33, false);
close_nointr_nofail(fd);
if (k >= 32) {
id[32] = '\n';
id[33] = 0;
log_info("Initializing machine ID from D-Bus machine ID.");
return 0;
}
}
/* If that didn't work, generate a random machine id */
r = sd_id128_randomize(&buf);
if (r < 0) {
log_error("Failed to open /dev/urandom: %s", strerror(-r));
return r;
}
for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
q[0] = hexchar(*p >> 4);
q[1] = hexchar(*p & 15);
}
id[32] = '\n';
id[33] = 0;
log_info("Initializing machine ID from random generator.");
return 0;
}
int machine_id_setup(void) {
int fd, r;
bool writable;
struct stat st;
char id[34]; /* 32 + \n + \0 */
mode_t m;
m = umask(0000);
/* We create this 0444, to indicate that this isn't really
* something you should ever modify. Of course, since the file
* will be owned by root it doesn't matter much, but maybe
* people look. */
fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
if (fd >= 0)
writable = true;
else {
fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (fd < 0) {
umask(m);
log_error("Cannot open /etc/machine-id: %m");
return -errno;
}
writable = false;
}
umask(m);
if (fstat(fd, &st) < 0) {
log_error("fstat() failed: %m");
r = -errno;
goto finish;
}
if (S_ISREG(st.st_mode)) {
if (loop_read(fd, id, 32, false) >= 32) {
r = 0;
goto finish;
}
}
/* Hmm, so, the id currently stored is not useful, then let's
* generate one */
r = generate(id);
if (r < 0)
goto finish;
if (S_ISREG(st.st_mode) && writable) {
lseek(fd, 0, SEEK_SET);
if (loop_write(fd, id, 33, false) == 33) {
r = 0;
goto finish;
}
}
close_nointr_nofail(fd);
fd = -1;
/* Hmm, we couldn't write it? So let's write it to
* /run/systemd/machine-id as a replacement */
mkdir_p("/run/systemd", 0755);
m = umask(0022);
r = write_one_line_file("/run/systemd/machine-id", id);
umask(m);
if (r < 0) {
log_error("Cannot write /run/systemd/machine-id: %s", strerror(-r));
unlink("/run/systemd/machine-id");
goto finish;
}
/* And now, let's mount it over */
r = mount("/run/systemd/machine-id", "/etc/machine-id", "bind", MS_BIND|MS_RDONLY, NULL) < 0 ? -errno : 0;
unlink("/run/systemd/machine-id");
if (r < 0)
log_error("Failed to mount /etc/machine-id: %s", strerror(-r));
else
log_info("Installed transient /etc/machine-id file.");
finish:
if (fd >= 0)
close_nointr_nofail(fd);
return r;
}