/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #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, VIRTUALIZATION_BHYVE)) { /* 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; }