365 lines
12 KiB
C
365 lines
12 KiB
C
/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <fcntl.h>
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#include <sched.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/mount.h>
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#include <unistd.h>
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#include "sd-id128.h"
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "fs-util.h"
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#include "hexdecoct.h"
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#include "io-util.h"
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#include "log.h"
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#include "machine-id-setup.h"
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#include "macro.h"
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#include "mkdir.h"
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#include "mount-util.h"
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#include "path-util.h"
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#include "process-util.h"
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#include "stat-util.h"
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#include "string-util.h"
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#include "umask-util.h"
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#include "util.h"
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#include "virt.h"
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static int shorten_uuid(char destination[34], const char source[36]) {
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unsigned i, j;
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assert(destination);
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assert(source);
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/* Converts a UUID into a machine ID, by lowercasing it and
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* removing dashes. Validates everything. */
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for (i = 0, j = 0; i < 36 && j < 32; i++) {
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int t;
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t = unhexchar(source[i]);
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if (t < 0)
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continue;
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destination[j++] = hexchar(t);
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}
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if (i != 36 || j != 32)
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return -EINVAL;
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destination[32] = '\n';
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destination[33] = 0;
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return 0;
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}
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static int read_machine_id(int fd, char id[34]) {
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char id_to_validate[34];
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int r;
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assert(fd >= 0);
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assert(id);
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/* Reads a machine ID from a file, validates it, and returns
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* it. The returned ID ends in a newline. */
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r = loop_read_exact(fd, id_to_validate, 33, false);
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if (r < 0)
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return r;
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if (id_to_validate[32] != '\n')
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return -EINVAL;
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id_to_validate[32] = 0;
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if (!id128_is_valid(id_to_validate))
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return -EINVAL;
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memcpy(id, id_to_validate, 32);
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id[32] = '\n';
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id[33] = 0;
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return 0;
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}
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static int write_machine_id(int fd, const char id[34]) {
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int r;
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assert(fd >= 0);
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assert(id);
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if (lseek(fd, 0, SEEK_SET) < 0)
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return -errno;
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r = loop_write(fd, id, 33, false);
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if (r < 0)
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return r;
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if (fsync(fd) < 0)
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return -errno;
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return 0;
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}
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static int generate_machine_id(char id[34], const char *root) {
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int fd, r;
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unsigned char *p;
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sd_id128_t buf;
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char *q;
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const char *dbus_machine_id;
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assert(id);
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dbus_machine_id = prefix_roota(root, "/var/lib/dbus/machine-id");
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/* First, try reading the D-Bus machine id, unless it is a symlink */
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fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
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if (fd >= 0) {
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r = read_machine_id(fd, id);
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safe_close(fd);
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if (r >= 0) {
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log_info("Initializing machine ID from D-Bus machine ID.");
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return 0;
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}
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}
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if (isempty(root)) {
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/* If that didn't work, see if we are running in a container,
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* and a machine ID was passed in via $container_uuid the way
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* libvirt/LXC does it */
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if (detect_container() > 0) {
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_cleanup_free_ char *e = NULL;
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r = getenv_for_pid(1, "container_uuid", &e);
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if (r > 0) {
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r = shorten_uuid(id, e);
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if (r >= 0) {
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log_info("Initializing machine ID from container UUID.");
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return 0;
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}
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}
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} else if (detect_vm() == VIRTUALIZATION_KVM) {
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/* If we are not running in a container, see if we are
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* running in qemu/kvm and a machine ID was passed in
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* via -uuid on the qemu/kvm command line */
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char uuid[36];
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fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
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if (fd >= 0) {
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r = loop_read_exact(fd, uuid, 36, false);
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safe_close(fd);
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if (r >= 0) {
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r = shorten_uuid(id, uuid);
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if (r >= 0) {
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log_info("Initializing machine ID from KVM UUID.");
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return 0;
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}
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}
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}
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}
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}
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/* If that didn't work, generate a random machine id */
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r = sd_id128_randomize(&buf);
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if (r < 0)
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return log_error_errno(r, "Failed to open /dev/urandom: %m");
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for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
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q[0] = hexchar(*p >> 4);
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q[1] = hexchar(*p & 15);
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}
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id[32] = '\n';
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id[33] = 0;
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log_info("Initializing machine ID from random generator.");
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return 0;
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}
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int machine_id_setup(const char *root, sd_id128_t machine_id) {
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const char *etc_machine_id, *run_machine_id;
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_cleanup_close_ int fd = -1;
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bool writable = true;
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char id[34]; /* 32 + \n + \0 */
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int r;
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etc_machine_id = prefix_roota(root, "/etc/machine-id");
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run_machine_id = prefix_roota(root, "/run/machine-id");
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RUN_WITH_UMASK(0000) {
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/* We create this 0444, to indicate that this isn't really
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* something you should ever modify. Of course, since the file
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* will be owned by root it doesn't matter much, but maybe
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* people look. */
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mkdir_parents(etc_machine_id, 0755);
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fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
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if (fd < 0) {
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int old_errno = errno;
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fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
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if (fd < 0) {
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if (old_errno == EROFS && errno == ENOENT)
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log_error_errno(errno,
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"System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
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"Booting up is supported only when:\n"
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"1) /etc/machine-id exists and is populated.\n"
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"2) /etc/machine-id exists and is empty.\n"
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"3) /etc/machine-id is missing and /etc is writable.\n");
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else
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log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
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return -errno;
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}
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writable = false;
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}
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}
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/* A machine id argument overrides all other machined-ids */
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if (!sd_id128_is_null(machine_id)) {
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sd_id128_to_string(machine_id, id);
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id[32] = '\n';
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id[33] = 0;
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} else {
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if (read_machine_id(fd, id) >= 0)
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return 0;
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/* Hmm, so, the id currently stored is not useful, then let's
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* generate one */
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r = generate_machine_id(id, root);
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if (r < 0)
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return r;
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}
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if (writable)
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if (write_machine_id(fd, id) >= 0)
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return 0;
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fd = safe_close(fd);
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/* Hmm, we couldn't write it? So let's write it to
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* /run/machine-id as a replacement */
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RUN_WITH_UMASK(0022) {
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r = write_string_file(run_machine_id, id, WRITE_STRING_FILE_CREATE);
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if (r < 0) {
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(void) unlink(run_machine_id);
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return log_error_errno(r, "Cannot write %s: %m", run_machine_id);
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}
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}
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/* And now, let's mount it over */
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if (mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL) < 0) {
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(void) unlink_noerrno(run_machine_id);
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return log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id);
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}
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log_info("Installed transient %s file.", etc_machine_id);
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/* Mark the mount read-only */
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if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
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log_warning_errno(errno, "Failed to make transient %s read-only: %m", etc_machine_id);
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return 0;
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}
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int machine_id_commit(const char *root) {
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_cleanup_close_ int fd = -1, initial_mntns_fd = -1;
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const char *etc_machine_id;
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char id[34]; /* 32 + \n + \0 */
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int r;
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etc_machine_id = prefix_roota(root, "/etc/machine-id");
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r = path_is_mount_point(etc_machine_id, 0);
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if (r < 0)
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return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", etc_machine_id);
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if (r == 0) {
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log_debug("%s is not a mount point. Nothing to do.", etc_machine_id);
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return 0;
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}
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/* Read existing machine-id */
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fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
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if (fd < 0)
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return log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
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r = read_machine_id(fd, id);
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if (r < 0)
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return log_error_errno(r, "We didn't find a valid machine ID in %s.", etc_machine_id);
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r = fd_is_temporary_fs(fd);
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if (r < 0)
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return log_error_errno(r, "Failed to determine whether %s is on a temporary file system: %m", etc_machine_id);
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if (r == 0) {
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log_error("%s is not on a temporary file system.", etc_machine_id);
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return -EROFS;
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}
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fd = safe_close(fd);
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/* Store current mount namespace */
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r = namespace_open(0, NULL, &initial_mntns_fd, NULL, NULL, NULL);
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if (r < 0)
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return log_error_errno(r, "Can't fetch current mount namespace: %m");
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/* Switch to a new mount namespace, isolate ourself and unmount etc_machine_id in our new namespace */
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if (unshare(CLONE_NEWNS) < 0)
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return log_error_errno(errno, "Failed to enter new namespace: %m");
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if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) < 0)
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return log_error_errno(errno, "Couldn't make-rslave / mountpoint in our private namespace: %m");
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if (umount(etc_machine_id) < 0)
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return log_error_errno(errno, "Failed to unmount transient %s file in our private namespace: %m", etc_machine_id);
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/* Update a persistent version of etc_machine_id */
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fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
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if (fd < 0)
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return log_error_errno(errno, "Cannot open for writing %s. This is mandatory to get a persistent machine-id: %m", etc_machine_id);
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r = write_machine_id(fd, id);
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if (r < 0)
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return log_error_errno(r, "Cannot write %s: %m", etc_machine_id);
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fd = safe_close(fd);
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/* Return to initial namespace and proceed a lazy tmpfs unmount */
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r = namespace_enter(-1, initial_mntns_fd, -1, -1, -1);
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if (r < 0)
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return log_warning_errno(r, "Failed to switch back to initial mount namespace: %m.\nWe'll keep transient %s file until next reboot.", etc_machine_id);
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if (umount2(etc_machine_id, MNT_DETACH) < 0)
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return log_warning_errno(errno, "Failed to unmount transient %s file: %m.\nWe keep that mount until next reboot.", etc_machine_id);
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return 0;
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}
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