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[36], const char *source) {
  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;
  70         _cleanup_free_ char *dbus_machine_id = NULL;
  71
  72         assert(id);
  73
  74         if (asprintf(&dbus_machine_id, "%s/var/lib/dbus/machine-id", root) < 0)
  75                 return log_oom();
  76
  77         /* First, try reading the D-Bus machine id, unless it is a symlink */
  78         fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
  79         if (fd >= 0) {
  80                 k = loop_read(fd, id, 33, false);
  81                 safe_close(fd);
  82
  83                 if (k == 33 && id[32] == '\n') {
  84
  85                         id[32] = 0;
  86                         if (id128_is_valid(id)) {
  87                                 id[32] = '\n';
  88                                 id[33] = 0;
  89
  90                                 log_info("Initializing machine ID from D-Bus machine ID.");
  91                                 return 0;
  92                         }
  93                 }
  94         }
  95
  96         /* If that didn't work, see if we are running in a container,
  97          * and a machine ID was passed in via $container_uuid the way
  98          * libvirt/LXC does it */
  99         r = detect_container(NULL);
 100         if (r > 0) {
 101                 _cleanup_free_ char *e = NULL;
 102
 103                 r = getenv_for_pid(1, "container_uuid", &e);
 104                 if (r > 0) {
 105                         if (strlen(e) >= 36) {
 106                                 r = shorten_uuid(id, e);
 107                                 if (r >= 0) {
 108                                         log_info("Initializing machine ID from container UUID.");
 109                                         return 0;
 110                                 }
 111                         }
 112                 }
 113
 114         } else {
 115                 /* If we are not running in a container, see if we are
 116                  * running in qemu/kvm and a machine ID was passed in
 117                  * via -uuid on the qemu/kvm command line */
 118
 119                 r = detect_vm(&vm_id);
 120                 if (r > 0 && streq(vm_id, "kvm")) {
 121                         char uuid[37];
 122
 123                         fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
 124                         if (fd >= 0) {
 125                                 k = loop_read(fd, uuid, 36, false);
 126                                 safe_close(fd);
 127
 128                                 if (k >= 36) {
 129                                         r = shorten_uuid(id, uuid);
 130                                         if (r >= 0) {
 131                                                 log_info("Initializing machine ID from KVM UUID.");
 132                                                 return 0;
 133                                         }
 134                                 }
 135                         }
 136                 }
 137         }
 138
 139         /* If that didn't work, generate a random machine id */
 140         r = sd_id128_randomize(&buf);
 141         if (r < 0) {
 142                 log_error("Failed to open /dev/urandom: %s", strerror(-r));
 143                 return r;
 144         }
 145
 146         for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
 147                 q[0] = hexchar(*p >> 4);
 148                 q[1] = hexchar(*p & 15);
 149         }
 150
 151         id[32] = '\n';
 152         id[33] = 0;
 153
 154         log_info("Initializing machine ID from random generator.");
 155
 156         return 0;
 157 }
 158
 159 int machine_id_setup(const char *root) {
 160         _cleanup_close_ int fd = -1;
 161         int r;
 162         bool writable = false;
 163         struct stat st;
 164         char id[34]; /* 32 + \n + \0 */
 165         char *etc_machine_id, *run_machine_id;
 166
 167         etc_machine_id = strappenda(root, "/etc/machine-id");
 168         path_kill_slashes(etc_machine_id);
 169
 170         run_machine_id = strappenda(root, "/run/machine-id");
 171         path_kill_slashes(run_machine_id);
 172
 173         RUN_WITH_UMASK(0000) {
 174                 /* We create this 0444, to indicate that this isn't really
 175                  * something you should ever modify. Of course, since the file
 176                  * will be owned by root it doesn't matter much, but maybe
 177                  * people look. */
 178
 179                 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
 180                 if (fd >= 0)
 181                         writable = true;
 182                 else {
 183                         fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
 184                         if (fd < 0) {
 185                                 log_error("Cannot open %s: %m", etc_machine_id);
 186                                 return -errno;
 187                         }
 188
 189                         writable = false;
 190                 }
 191         }
 192
 193         if (fstat(fd, &st) < 0) {
 194                 log_error("fstat() failed: %m");
 195                 return -errno;
 196         }
 197
 198         if (S_ISREG(st.st_mode))
 199                 if (loop_read(fd, id, 33, false) == 33 && id[32] == '\n') {
 200                         id[32] = 0;
 201
 202                         if (id128_is_valid(id))
 203                                 return 0;
 204                 }
 205
 206         /* Hmm, so, the id currently stored is not useful, then let's
 207          * generate one */
 208
 209         r = generate(id, root);
 210         if (r < 0)
 211                 return r;
 212
 213         if (S_ISREG(st.st_mode) && writable) {
 214                 lseek(fd, 0, SEEK_SET);
 215
 216                 if (loop_write(fd, id, 33, false) == 33)
 217                         return 0;
 218         }
 219
 220         fd = safe_close(fd);
 221
 222         /* Hmm, we couldn't write it? So let's write it to
 223          * /run/machine-id as a replacement */
 224
 225         RUN_WITH_UMASK(0022) {
 226                 r = write_string_file(run_machine_id, id);
 227         }
 228         if (r < 0) {
 229                 log_error("Cannot write %s: %s", run_machine_id, strerror(-r));
 230                 unlink(run_machine_id);
 231                 return r;
 232         }
 233
 234         /* And now, let's mount it over */
 235         r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
 236         if (r < 0) {
 237                 log_error("Failed to mount %s: %m", etc_machine_id);
 238                 unlink_noerrno(run_machine_id);
 239                 return -errno;
 240         }
 241
 242         log_info("Installed transient %s file.", etc_machine_id);
 243
 244         /* Mark the mount read-only */
 245         if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
 246                 log_warning("Failed to make transient %s read-only: %m", etc_machine_id);
 247
 248         return 0;
 249 }