diff options
Diffstat (limited to 'src/libcore/machine-id-setup.c')
| -rw-r--r-- | src/libcore/machine-id-setup.c | 364 |
1 files changed, 364 insertions, 0 deletions
diff --git a/src/libcore/machine-id-setup.c b/src/libcore/machine-id-setup.c new file mode 100644 index 0000000000..812e4b038c --- /dev/null +++ b/src/libcore/machine-id-setup.c @@ -0,0 +1,364 @@ +/*** + 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 <errno.h> +#include <fcntl.h> +#include <sched.h> +#include <stdio.h> +#include <string.h> +#include <sys/mount.h> +#include <unistd.h> + +#include <systemd/sd-id128.h> + +#include "alloc-util.h" +#include "fd-util.h" +#include "fileio.h" +#include "fs-util.h" +#include "hexdecoct.h" +#include "io-util.h" +#include "log.h" +#include "machine-id-setup.h" +#include "macro.h" +#include "mkdir.h" +#include "mount-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 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, const char id[34]) { + int r; + + assert(fd >= 0); + assert(id); + + if (lseek(fd, 0, SEEK_SET) < 0) + return -errno; + + r = loop_write(fd, id, 33, false); + if (r < 0) + return r; + + if (fsync(fd) < 0) + return -errno; + + return 0; +} + +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 *dbus_machine_id; + + assert(id); + + dbus_machine_id = prefix_roota(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 */ + + if (detect_container() > 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 (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 */ + + 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, sd_id128_t machine_id) { + const char *etc_machine_id, *run_machine_id; + _cleanup_close_ int fd = -1; + bool writable = true; + char id[34]; /* 32 + \n + \0 */ + int r; + + etc_machine_id = prefix_roota(root, "/etc/machine-id"); + run_machine_id = prefix_roota(root, "/run/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. */ + + 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; + } + } + + /* A machine id argument overrides all other machined-ids */ + if (!sd_id128_is_null(machine_id)) { + sd_id128_to_string(machine_id, id); + id[32] = '\n'; + id[33] = 0; + } else { + 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, WRITE_STRING_FILE_CREATE); + 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; + + etc_machine_id = prefix_roota(root, "/etc/machine-id"); + + r = path_is_mount_point(etc_machine_id, 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 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, 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, -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; +} |