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-rw-r--r--src/core/machine-id-setup.c243
1 files changed, 243 insertions, 0 deletions
diff --git a/src/core/machine-id-setup.c b/src/core/machine-id-setup.c
new file mode 100644
index 0000000..aae5480
--- /dev/null
+++ b/src/core/machine-id-setup.c
@@ -0,0 +1,243 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <fcntl.h>
+#include <sched.h>
+#include <sys/mount.h>
+#include <unistd.h>
+
+#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;
+}