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                 return log_error_errno(r, "Failed to open /dev/urandom: %m");
 146
 147         for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
 148                 q[0] = hexchar(*p >> 4);
 149                 q[1] = hexchar(*p & 15);
 150         }
 151
 152         id[32] = '\n';
 153         id[33] = 0;
 154
 155         log_info("Initializing machine ID from random generator.");
 156
 157         return 0;
 158 }
 159
 160 int machine_id_setup(const char *root) {
 161         const char *etc_machine_id, *run_machine_id;
 162         _cleanup_close_ int fd = -1;
 163         bool writable = true;
 164         struct stat st;
 165         char id[34]; /* 32 + \n + \0 */
 166         int r;
 167
 168         if (isempty(root))  {
 169                 etc_machine_id = "/etc/machine-id";
 170                 run_machine_id = "/run/machine-id";
 171         } else {
 172                 etc_machine_id = strappenda(root, "/etc/machine-id");
 173                 path_kill_slashes((char*) etc_machine_id);
 174
 175                 run_machine_id = strappenda(root, "/run/machine-id");
 176                 path_kill_slashes((char*) run_machine_id);
 177         }
 178
 179         RUN_WITH_UMASK(0000) {
 180                 /* We create this 0444, to indicate that this isn't really
 181                  * something you should ever modify. Of course, since the file
 182                  * will be owned by root it doesn't matter much, but maybe
 183                  * people look. */
 184
 185                 mkdir_parents(etc_machine_id, 0755);
 186                 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
 187                 if (fd < 0) {
 188                         int old_errno = errno;
 189
 190                         fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
 191                         if (fd < 0) {
 192                                 if (old_errno == EROFS && errno == ENOENT)
 193                                         log_error("System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
 194                                                   "Booting up is supported only when:\n"
 195                                                   "1) /etc/machine-id exists and is populated.\n"
 196                                                   "2) /etc/machine-id exists and is empty.\n"
 197                                                   "3) /etc/machine-id is missing and /etc is writable.\n");
 198                                 else
 199                                         log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
 200                                 return -errno;
 201                         }
 202
 203                         writable = false;
 204                 }
 205         }
 206
 207         if (fstat(fd, &st) < 0)
 208                 return log_error_errno(errno, "fstat() failed: %m");
 209
 210         if (S_ISREG(st.st_mode))
 211                 if (loop_read(fd, id, 33, false) == 33 && id[32] == '\n') {
 212                         id[32] = 0;
 213
 214                         if (id128_is_valid(id))
 215                                 return 0;
 216                 }
 217
 218         /* Hmm, so, the id currently stored is not useful, then let's
 219          * generate one */
 220
 221         r = generate(id, root);
 222         if (r < 0)
 223                 return r;
 224
 225         if (S_ISREG(st.st_mode) && writable) {
 226                 lseek(fd, 0, SEEK_SET);
 227
 228                 if (loop_write(fd, id, 33, false) == 33)
 229                         return 0;
 230         }
 231
 232         fd = safe_close(fd);
 233
 234         /* Hmm, we couldn't write it? So let's write it to
 235          * /run/machine-id as a replacement */
 236
 237         RUN_WITH_UMASK(0022) {
 238                 r = write_string_file(run_machine_id, id);
 239         }
 240         if (r < 0) {
 241                 log_error_errno(r, "Cannot write %s: %m", run_machine_id);
 242                 unlink(run_machine_id);
 243                 return r;
 244         }
 245
 246         /* And now, let's mount it over */
 247         r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
 248         if (r < 0) {
 249                 log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id);
 250                 unlink_noerrno(run_machine_id);
 251                 return -errno;
 252         }
 253
 254         log_info("Installed transient %s file.", etc_machine_id);
 255
 256         /* Mark the mount read-only */
 257         if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
 258                 log_warning_errno(errno, "Failed to make transient %s read-only: %m", etc_machine_id);
 259
 260         return 0;
 261 }