/*-*- 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 Lesser General Public License as published by the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details. You should have received a copy of the GNU Lesser 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 <fcntl.h> #include <sys/mount.h> #include "systemd/sd-id128.h" #include "machine-id-setup.h" #include "macro.h" #include "util.h" #include "mkdir.h" #include "log.h" #include "virt.h" #include "fileio.h" #include "path-util.h" #include "process-util.h" static int shorten_uuid(char destination[34], const char source[36]) { unsigned i, j; assert(destination); assert(source); /* Converts a UUID into a machine ID, by lowercasing it and * removing dashes. Validates everything. */ for (i = 0, j = 0; i < 36 && j < 32; i++) { int t; t = unhexchar(source[i]); if (t < 0) continue; destination[j++] = hexchar(t); } if (i != 36 || j != 32) return -EINVAL; destination[32] = '\n'; destination[33] = 0; return 0; } static int read_machine_id(int fd, char id[34]) { char id_to_validate[34]; int r; assert(fd >= 0); assert(id); /* Reads a machine ID from a file, validates it, and returns * it. The returned ID ends in a newline. */ r = loop_read_exact(fd, id_to_validate, 33, false); if (r < 0) return r; if (id_to_validate[32] != '\n') return -EINVAL; id_to_validate[32] = 0; if (!id128_is_valid(id_to_validate)) return -EINVAL; memcpy(id, id_to_validate, 32); id[32] = '\n'; id[33] = 0; return 0; } static int write_machine_id(int fd, char id[34]) { assert(fd >= 0); assert(id); if (lseek(fd, 0, SEEK_SET) < 0) return -errno; return loop_write(fd, id, 33, false); } static int generate_machine_id(char id[34], const char *root) { int fd, r; unsigned char *p; sd_id128_t buf; char *q; const char *vm_id, *dbus_machine_id; assert(id); if (isempty(root)) dbus_machine_id = "/var/lib/dbus/machine-id"; else dbus_machine_id = strjoina(root, "/var/lib/dbus/machine-id"); /* First, try reading the D-Bus machine id, unless it is a symlink */ fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW); if (fd >= 0) { r = read_machine_id(fd, id); safe_close(fd); if (r >= 0) { log_info("Initializing machine ID from D-Bus machine ID."); return 0; } } 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 */ r = detect_container(NULL); if (r > 0) { _cleanup_free_ char *e = NULL; r = getenv_for_pid(1, "container_uuid", &e); if (r > 0) { r = shorten_uuid(id, e); if (r >= 0) { log_info("Initializing machine ID from container UUID."); return 0; } } } else { /* 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 */ r = detect_vm(&vm_id); if (r > 0 && streq(vm_id, "kvm")) { char uuid[36]; fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW); if (fd >= 0) { r = loop_read_exact(fd, uuid, 36, false); safe_close(fd); if (r >= 0) { r = shorten_uuid(id, uuid); if (r >= 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(&buf); if (r < 0) return log_error_errno(r, "Failed to open /dev/urandom: %m"); 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(const char *root) { const char *etc_machine_id, *run_machine_id; _cleanup_close_ int fd = -1; bool writable = true; char id[34]; /* 32 + \n + \0 */ int r; if (isempty(root)) { etc_machine_id = "/etc/machine-id"; run_machine_id = "/run/machine-id"; } else { char *x; x = strjoina(root, "/etc/machine-id"); etc_machine_id = path_kill_slashes(x); x = strjoina(root, "/run/machine-id"); run_machine_id = path_kill_slashes(x); } 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. */ 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) 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 log_error_errno(errno, "Cannot open %s: %m", etc_machine_id); return -errno; } writable = false; } } if (read_machine_id(fd, id) >= 0) return 0; /* Hmm, so, the id currently stored is not useful, then let's * generate one */ r = generate_machine_id(id, root); if (r < 0) return r; if (writable) if (write_machine_id(fd, id) >= 0) return 0; fd = safe_close(fd); /* Hmm, we couldn't write it? So let's write it to * /run/machine-id as a replacement */ RUN_WITH_UMASK(0022) { r = write_string_file(run_machine_id, 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 */ 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: %m", etc_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; char id[34]; /* 32 + \n + \0 */ int r; if (isempty(root)) etc_machine_id = "/etc/machine-id"; else { char *x; x = strjoina(root, "/etc/machine-id"); etc_machine_id = path_kill_slashes(x); } r = path_is_mount_point(etc_machine_id, false); 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 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 = read_machine_id(fd, id); if (r < 0) return log_error_errno(r, "We didn't find a valid machine ID in %s.", 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) { log_error("%s is not on a temporary file system.", etc_machine_id); return -EROFS; } fd = safe_close(fd); /* Store current mount namespace */ r = namespace_open(0, NULL, &initial_mntns_fd, 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 */ fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444); if (fd < 0) return log_error_errno(errno, "Cannot open for writing %s. This is mandatory to get a persistent machine-id: %m", etc_machine_id); r = write_machine_id(fd, id); if (r < 0) return log_error_errno(r, "Cannot write %s: %m", etc_machine_id); fd = safe_close(fd); /* Return to initial namespace and proceed a lazy tmpfs unmount */ r = namespace_enter(-1, initial_mntns_fd, -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; }