src/core/machine-id-setup.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2010 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <unistd.h>
  23 #include <stdio.h>
  24 #include <errno.h>
  25 #include <string.h>
  26 #include <stdlib.h>
  27 #include <fcntl.h>
  28 #include <sys/mount.h>
  29
  30 #include "systemd/sd-id128.h"
  31
  32 #include "machine-id-setup.h"
  33 #include "macro.h"
  34 #include "util.h"
  35 #include "mkdir.h"
  36 #include "log.h"
  37 #include "virt.h"
  38 #include "fileio.h"
  39 #include "path-util.h"
  40
  41 static int shorten_uuid(char destination[34], const char source[36]) {
  42         unsigned i, j;
  43
  44         for (i = 0, j = 0; i < 36 && j < 32; i++) {
  45                 int t;
  46
  47                 t = unhexchar(source[i]);
  48                 if (t < 0)
  49                         continue;
  50
  51                 destination[j++] = hexchar(t);
  52         }
  53
  54         if (i == 36 && j == 32) {
  55                 destination[32] = '\n';
  56                 destination[33] = 0;
  57                 return 0;
  58         }
  59
  60         return -EINVAL;
  61 }
  62
  63 static int generate(char id[34], const char *root) {
  64         int fd, r;
  65         unsigned char *p;
  66         sd_id128_t buf;
  67         char  *q;
  68         ssize_t k;
  69         const char *vm_id, *dbus_machine_id;
  70
  71         assert(id);
  72
  73         if (isempty(root))
  74                 dbus_machine_id = "/var/lib/dbus/machine-id";
  75         else
  76                 dbus_machine_id = strappenda(root, "/var/lib/dbus/machine-id");
  77
  78         /* First, try reading the D-Bus machine id, unless it is a symlink */
  79         fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
  80         if (fd >= 0) {
  81                 k = loop_read(fd, id, 33, false);
  82                 safe_close(fd);
  83
  84                 if (k == 33 && id[32] == '\n') {
  85
  86                         id[32] = 0;
  87                         if (id128_is_valid(id)) {
  88                                 id[32] = '\n';
  89                                 id[33] = 0;
  90
  91                                 log_info("Initializing machine ID from D-Bus machine ID.");
  92                                 return 0;
  93                         }
  94                 }
  95         }
  96
  97         if (isempty(root)) {
  98                 /* If that didn't work, see if we are running in a container,
  99                  * and a machine ID was passed in via $container_uuid the way
 100                  * libvirt/LXC does it */
 101                 r = detect_container(NULL);
 102                 if (r > 0) {
 103                         _cleanup_free_ char *e = NULL;
 104
 105                         r = getenv_for_pid(1, "container_uuid", &e);
 106                         if (r > 0) {
 107                                 if (strlen(e) >= 36) {
 108                                         r = shorten_uuid(id, e);
 109                                         if (r >= 0) {
 110                                                 log_info("Initializing machine ID from container UUID.");
 111                                                 return 0;
 112                                         }
 113                                 }
 114                         }
 115
 116                 } else {
 117                         /* If we are not running in a container, see if we are
 118                          * running in qemu/kvm and a machine ID was passed in
 119                          * via -uuid on the qemu/kvm command line */
 120
 121                         r = detect_vm(&vm_id);
 122                         if (r > 0 && streq(vm_id, "kvm")) {
 123                                 char uuid[37];
 124
 125                                 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
 126                                 if (fd >= 0) {
 127                                         k = loop_read(fd, uuid, 36, false);
 128                                         safe_close(fd);
 129
 130                                         if (k >= 36) {
 131                                                 r = shorten_uuid(id, uuid);
 132                                                 if (r >= 0) {
 133                                                         log_info("Initializing machine ID from KVM UUID.");
 134                                                         return 0;
 135                                                 }
 136                                         }
 137                                 }
 138                         }
 139                 }
 140         }
 141
 142         /* If that didn't work, generate a random machine id */
 143         r = sd_id128_randomize(&buf);
 144         if (r < 0) {
 145                 log_error_errno(-r, "Failed to open /dev/urandom: %m");
 146                 return r;
 147         }
 148
 149         for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
 150                 q[0] = hexchar(*p >> 4);
 151                 q[1] = hexchar(*p & 15);
 152         }
 153
 154         id[32] = '\n';
 155         id[33] = 0;
 156
 157         log_info("Initializing machine ID from random generator.");
 158
 159         return 0;
 160 }
 161
 162 int machine_id_setup(const char *root) {
 163         const char *etc_machine_id, *run_machine_id;
 164         _cleanup_close_ int fd = -1;
 165         bool writable = true;
 166         struct stat st;
 167         char id[34]; /* 32 + \n + \0 */
 168         int r;
 169
 170         if (isempty(root))  {
 171                 etc_machine_id = "/etc/machine-id";
 172                 run_machine_id = "/run/machine-id";
 173         } else {
 174                 etc_machine_id = strappenda(root, "/etc/machine-id");
 175                 path_kill_slashes((char*) etc_machine_id);
 176
 177                 run_machine_id = strappenda(root, "/run/machine-id");
 178                 path_kill_slashes((char*) run_machine_id);
 179         }
 180
 181         RUN_WITH_UMASK(0000) {
 182                 /* We create this 0444, to indicate that this isn't really
 183                  * something you should ever modify. Of course, since the file
 184                  * will be owned by root it doesn't matter much, but maybe
 185                  * people look. */
 186
 187                 mkdir_parents(etc_machine_id, 0755);
 188                 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
 189                 if (fd < 0) {
 190                         int old_errno = errno;
 191
 192                         fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
 193                         if (fd < 0) {
 194                                 if (old_errno == EROFS && errno == ENOENT)
 195                                         log_error("System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
 196                                                   "Booting up is supported only when:\n"
 197                                                   "1) /etc/machine-id exists and is populated.\n"
 198                                                   "2) /etc/machine-id exists and is empty.\n"
 199                                                   "3) /etc/machine-id is missing and /etc is writable.\n");
 200                                 else
 201                                         log_error("Cannot open %s: %m", etc_machine_id);
 202                                 return -errno;
 203                         }
 204
 205                         writable = false;
 206                 }
 207         }
 208
 209         if (fstat(fd, &st) < 0) {
 210                 log_error("fstat() failed: %m");
 211                 return -errno;
 212         }
 213
 214         if (S_ISREG(st.st_mode))
 215                 if (loop_read(fd, id, 33, false) == 33 && id[32] == '\n') {
 216                         id[32] = 0;
 217
 218                         if (id128_is_valid(id))
 219                                 return 0;
 220                 }
 221
 222         /* Hmm, so, the id currently stored is not useful, then let's
 223          * generate one */
 224
 225         r = generate(id, root);
 226         if (r < 0)
 227                 return r;
 228
 229         if (S_ISREG(st.st_mode) && writable) {
 230                 lseek(fd, 0, SEEK_SET);
 231
 232                 if (loop_write(fd, id, 33, false) == 33)
 233                         return 0;
 234         }
 235
 236         fd = safe_close(fd);
 237
 238         /* Hmm, we couldn't write it? So let's write it to
 239          * /run/machine-id as a replacement */
 240
 241         RUN_WITH_UMASK(0022) {
 242                 r = write_string_file(run_machine_id, id);
 243         }
 244         if (r < 0) {
 245                 log_error_errno(-r, "Cannot write %s: %m", run_machine_id);
 246                 unlink(run_machine_id);
 247                 return r;
 248         }
 249
 250         /* And now, let's mount it over */
 251         r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
 252         if (r < 0) {
 253                 log_error("Failed to mount %s: %m", etc_machine_id);
 254                 unlink_noerrno(run_machine_id);
 255                 return -errno;
 256         }
 257
 258         log_info("Installed transient %s file.", etc_machine_id);
 259
 260         /* Mark the mount read-only */
 261         if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
 262                 log_warning("Failed to make transient %s read-only: %m", etc_machine_id);
 263
 264         return 0;
 265 }