/* SPDX-License-Identifier: LGPL-2.1+ */ #include #include #include #include #include "sd-id128.h" #include "alloc-util.h" #include "fd-util.h" #include "fs-util.h" #include "id128-util.h" #include "log.h" #include "machine-id-setup.h" #include "macro.h" #include "mkdir.h" #include "mountpoint-util.h" #include "path-util.h" #include "process-util.h" #include "stat-util.h" #include "string-util.h" #include "umask-util.h" #include "util.h" #include "virt.h" static int generate_machine_id(const char *root, sd_id128_t *ret) { const char *dbus_machine_id; _cleanup_close_ int fd = -1; int r; assert(ret); /* First, try reading the D-Bus machine id, unless it is a symlink */ dbus_machine_id = prefix_roota(root, "/var/lib/dbus/machine-id"); fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW); if (fd >= 0) { if (id128_read_fd(fd, ID128_PLAIN, ret) >= 0) { log_info("Initializing machine ID from D-Bus machine ID."); return 0; } fd = safe_close(fd); } if (isempty(root)) { /* 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 (detect_vm() == VIRTUALIZATION_KVM) { /* If we are not running in a container, see if we are * running in qemu/kvm and a machine ID was passed in * via -uuid on the qemu/kvm command line */ if (id128_read("/sys/class/dmi/id/product_uuid", ID128_UUID, ret) >= 0) { log_info("Initializing machine ID from KVM 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, sd_id128_t machine_id, sd_id128_t *ret) { const char *etc_machine_id, *run_machine_id; _cleanup_close_ int fd = -1; bool writable; int r; etc_machine_id = prefix_roota(root, "/etc/machine-id"); RUN_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_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) == (off_t) -1) 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 (id128_write_fd(fd, ID128_PLAIN, machine_id, true) >= 0) goto finish; } fd = safe_close(fd); /* Hmm, we couldn't write it? So let's write it to /run/machine-id as a replacement */ run_machine_id = prefix_roota(root, "/run/machine-id"); RUN_WITH_UMASK(0022) r = id128_write(run_machine_id, ID128_PLAIN, machine_id, false); 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 */ if (mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL) < 0) { (void) unlink_noerrno(run_machine_id); return log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id); } log_info("Installed transient %s file.", etc_machine_id); /* Mark the mount read-only */ if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0) log_warning_errno(errno, "Failed to make transient %s read-only, ignoring: %m", etc_machine_id); finish: if (ret) *ret = machine_id; return 0; } int machine_id_commit(const char *root) { _cleanup_close_ int fd = -1, initial_mntns_fd = -1; const char *etc_machine_id; sd_id128_t id; int r; /* 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_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 */ if (unshare(CLONE_NEWNS) < 0) return log_error_errno(errno, "Failed to enter new namespace: %m"); if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) < 0) return log_error_errno(errno, "Couldn't make-rslave / mountpoint in our private namespace: %m"); if (umount(etc_machine_id) < 0) return log_error_errno(errno, "Failed to unmount transient %s file in our private namespace: %m", etc_machine_id); /* Update a persistent version of etc_machine_id */ r = id128_write(etc_machine_id, ID128_PLAIN, id, true); 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; }