diff options
Diffstat (limited to 'src/shared/machine-id-setup.c')
| -rw-r--r-- | src/shared/machine-id-setup.c | 295 |
1 files changed, 295 insertions, 0 deletions
diff --git a/src/shared/machine-id-setup.c b/src/shared/machine-id-setup.c new file mode 100644 index 0000000..3efba03 --- /dev/null +++ b/src/shared/machine-id-setup.c @@ -0,0 +1,295 @@ +/* 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; +} |