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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <fcntl.h>
#include <sched.h>
#include <sys/mount.h>
#include <unistd.h>
#include "sd-id128.h"
#include "alloc-util.h"
#include "chase.h"
#include "creds-util.h"
#include "fd-util.h"
#include "id128-util.h"
#include "io-util.h"
#include "log.h"
#include "machine-id-setup.h"
#include "macro.h"
#include "mkdir.h"
#include "mount-util.h"
#include "mountpoint-util.h"
#include "namespace-util.h"
#include "path-util.h"
#include "process-util.h"
#include "stat-util.h"
#include "string-util.h"
#include "sync-util.h"
#include "umask-util.h"
#include "virt.h"
static int acquire_machine_id_from_credential(sd_id128_t *ret) {
_cleanup_free_ char *buf = NULL;
int r;
r = read_credential_with_decryption("system.machine_id", (void**) &buf, /* ret_size= */ NULL);
if (r < 0)
return log_warning_errno(r, "Failed to read system.machine_id credential, ignoring: %m");
if (r == 0) /* not found */
return -ENXIO;
r = sd_id128_from_string(buf, ret);
if (r < 0)
return log_warning_errno(r, "Failed to parse system.machine_id credential, ignoring: %m");
log_info("Initializing machine ID from credential.");
return 0;
}
static int generate_machine_id(const char *root, sd_id128_t *ret) {
_cleanup_close_ int fd = -EBADF;
int r;
assert(ret);
/* First, try reading the D-Bus machine id, unless it is a symlink */
fd = chase_and_open("/var/lib/dbus/machine-id", root, CHASE_PREFIX_ROOT | CHASE_NOFOLLOW, O_RDONLY|O_CLOEXEC|O_NOCTTY, NULL);
if (fd >= 0 && id128_read_fd(fd, ID128_FORMAT_PLAIN | ID128_REFUSE_NULL, ret) >= 0) {
log_info("Initializing machine ID from D-Bus machine ID.");
return 0;
}
if (isempty(root) && running_in_chroot() <= 0) {
/* Let's use a system credential for the machine ID if we can */
r = acquire_machine_id_from_credential(ret);
if (r >= 0)
return r;
/* If that didn't work, see if we are running in a container,
* and a machine ID was passed in via $container_uuid the way
* libvirt/LXC does it */
if (detect_container() > 0) {
_cleanup_free_ char *e = NULL;
if (getenv_for_pid(1, "container_uuid", &e) > 0 &&
sd_id128_from_string(e, ret) >= 0) {
log_info("Initializing machine ID from container UUID.");
return 0;
}
} else if (IN_SET(detect_vm(), VIRTUALIZATION_KVM, VIRTUALIZATION_AMAZON, VIRTUALIZATION_QEMU, VIRTUALIZATION_XEN)) {
/* If we are not running in a container, see if we are running in a VM that provides
* a system UUID via the SMBIOS/DMI interfaces. Such environments include QEMU/KVM
* with the -uuid on the qemu command line or the Amazon EC2 Nitro hypervisor. */
if (id128_get_product(ret) >= 0) {
log_info("Initializing machine ID from VM UUID.");
return 0;
}
}
}
/* If that didn't work, generate a random machine id */
r = sd_id128_randomize(ret);
if (r < 0)
return log_error_errno(r, "Failed to generate randomized machine ID: %m");
log_info("Initializing machine ID from random generator.");
return 0;
}
int machine_id_setup(const char *root, bool force_transient, sd_id128_t machine_id, sd_id128_t *ret) {
const char *etc_machine_id, *run_machine_id;
_cleanup_close_ int fd = -EBADF;
bool writable;
int r;
etc_machine_id = prefix_roota(root, "/etc/machine-id");
WITH_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. */
(void) mkdir_parents(etc_machine_id, 0755);
fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
if (fd < 0) {
int old_errno = errno;
fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (fd < 0) {
if (old_errno == EROFS && errno == ENOENT)
return log_error_errno(errno,
"System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
"Booting up is supported only when:\n"
"1) /etc/machine-id exists and is populated.\n"
"2) /etc/machine-id exists and is empty.\n"
"3) /etc/machine-id is missing and /etc is writable.\n");
else
return log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
}
writable = false;
} else
writable = true;
}
/* A we got a valid machine ID argument, that's what counts */
if (sd_id128_is_null(machine_id)) {
/* Try to read any existing machine ID */
if (id128_read_fd(fd, ID128_FORMAT_PLAIN, ret) >= 0)
return 0;
/* Hmm, so, the id currently stored is not useful, then let's generate one */
r = generate_machine_id(root, &machine_id);
if (r < 0)
return r;
}
if (writable) {
if (lseek(fd, 0, SEEK_SET) < 0)
return log_error_errno(errno, "Failed to seek %s: %m", etc_machine_id);
if (ftruncate(fd, 0) < 0)
return log_error_errno(errno, "Failed to truncate %s: %m", etc_machine_id);
/* If the caller requested a transient machine-id, write the string "uninitialized\n" to
* disk and overmount it with a transient file.
*
* Otherwise write the machine-id directly to disk. */
if (force_transient) {
r = loop_write(fd, "uninitialized\n", SIZE_MAX);
if (r < 0)
return log_error_errno(r, "Failed to write uninitialized %s: %m", etc_machine_id);
r = fsync_full(fd);
if (r < 0)
return log_error_errno(r, "Failed to sync %s: %m", etc_machine_id);
} else {
r = id128_write_fd(fd, ID128_FORMAT_PLAIN | ID128_SYNC_ON_WRITE, machine_id);
if (r < 0)
return log_error_errno(r, "Failed to write %s: %m", etc_machine_id);
else
goto finish;
}
}
fd = safe_close(fd);
/* Hmm, we couldn't or shouldn't write the machine-id to /etc?
* So let's write it to /run/machine-id as a replacement */
run_machine_id = prefix_roota(root, "/run/machine-id");
WITH_UMASK(0022)
r = id128_write(run_machine_id, ID128_FORMAT_PLAIN, machine_id);
if (r < 0) {
(void) unlink(run_machine_id);
return log_error_errno(r, "Cannot write %s: %m", run_machine_id);
}
/* And now, let's mount it over */
r = mount_follow_verbose(LOG_ERR, run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
if (r < 0) {
(void) unlink(run_machine_id);
return r;
}
log_full(force_transient ? LOG_DEBUG : LOG_INFO, "Installed transient %s file.", etc_machine_id);
/* Mark the mount read-only */
r = mount_follow_verbose(LOG_WARNING, NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL);
if (r < 0)
return r;
finish:
if (ret)
*ret = machine_id;
return 0;
}
int machine_id_commit(const char *root) {
_cleanup_close_ int fd = -EBADF, initial_mntns_fd = -EBADF;
const char *etc_machine_id;
sd_id128_t id;
int r;
/* Before doing anything, sync everything to ensure any changes by first-boot units are persisted.
*
* First, explicitly sync the file systems we care about and check if it worked. */
FOREACH_STRING(sync_path, "/etc/", "/var/") {
r = syncfs_path(AT_FDCWD, sync_path);
if (r < 0)
return log_error_errno(r, "Cannot sync %s: %m", sync_path);
}
/* Afterwards, sync() the rest too, but we can't check the return value for these. */
sync();
/* Replaces a tmpfs bind mount of /etc/machine-id by a proper file, atomically. For this, the umount is removed
* in a mount namespace, a new file is created at the right place. Afterwards the mount is also removed in the
* original mount namespace, thus revealing the file that was just created. */
etc_machine_id = prefix_roota(root, "/etc/machine-id");
r = path_is_mount_point(etc_machine_id, NULL, 0);
if (r < 0)
return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", etc_machine_id);
if (r == 0) {
log_debug("%s is not a mount point. Nothing to do.", etc_machine_id);
return 0;
}
/* Read existing machine-id */
fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (fd < 0)
return log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
r = fd_is_temporary_fs(fd);
if (r < 0)
return log_error_errno(r, "Failed to determine whether %s is on a temporary file system: %m", etc_machine_id);
if (r == 0)
return log_error_errno(SYNTHETIC_ERRNO(EROFS),
"%s is not on a temporary file system.",
etc_machine_id);
r = id128_read_fd(fd, ID128_FORMAT_PLAIN, &id);
if (r < 0)
return log_error_errno(r, "We didn't find a valid machine ID in %s: %m", etc_machine_id);
fd = safe_close(fd);
/* Store current mount namespace */
r = namespace_open(0, NULL, &initial_mntns_fd, NULL, NULL, NULL);
if (r < 0)
return log_error_errno(r, "Can't fetch current mount namespace: %m");
/* Switch to a new mount namespace, isolate ourself and unmount etc_machine_id in our new namespace */
r = detach_mount_namespace();
if (r < 0)
return log_error_errno(r, "Failed to set up new mount namespace: %m");
r = umount_verbose(LOG_ERR, etc_machine_id, 0);
if (r < 0)
return r;
/* Update a persistent version of etc_machine_id */
r = id128_write(etc_machine_id, ID128_FORMAT_PLAIN | ID128_SYNC_ON_WRITE, id);
if (r < 0)
return log_error_errno(r, "Cannot write %s. This is mandatory to get a persistent machine ID: %m", etc_machine_id);
/* Return to initial namespace and proceed a lazy tmpfs unmount */
r = namespace_enter(-1, initial_mntns_fd, -1, -1, -1);
if (r < 0)
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);
if (umount2(etc_machine_id, MNT_DETACH) < 0)
return log_warning_errno(errno, "Failed to unmount transient %s file: %m.\nWe keep that mount until next reboot.", etc_machine_id);
return 0;
}
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