summaryrefslogtreecommitdiff
path: root/src/core/machine-id-setup.c
blob: 74582a5dcd0be2121778197e6301bc0f922fc4b7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  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 <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mount.h>

#include "systemd/sd-id128.h"

#include "machine-id-setup.h"
#include "macro.h"
#include "util.h"
#include "mkdir.h"
#include "log.h"
#include "virt.h"
#include "fileio.h"
#include "path-util.h"

static int shorten_uuid(char destination[34], const char source[36]) {
        unsigned i, j;

        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) {
                destination[32] = '\n';
                destination[33] = 0;
                return 0;
        }

        return -EINVAL;
}

static int generate(char id[34], const char *root) {
        int fd, r;
        unsigned char *p;
        sd_id128_t buf;
        char  *q;
        ssize_t k;
        const char *vm_id, *dbus_machine_id;

        assert(id);

        if (isempty(root))
                dbus_machine_id = "/var/lib/dbus/machine-id";
        else
                dbus_machine_id = strappenda(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) {
                k = loop_read(fd, id, 33, false);
                safe_close(fd);

                if (k == 33 && id[32] == '\n') {

                        id[32] = 0;
                        if (id128_is_valid(id)) {
                                id[32] = '\n';
                                id[33] = 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 */
                r = detect_container(NULL);
                if (r > 0) {
                        _cleanup_free_ char *e = NULL;

                        r = getenv_for_pid(1, "container_uuid", &e);
                        if (r > 0) {
                                if (strlen(e) >= 36) {
                                        r = shorten_uuid(id, e);
                                        if (r >= 0) {
                                                log_info("Initializing machine ID from container UUID.");
                                                return 0;
                                        }
                                }
                        }

                } else {
                        /* 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 */

                        r = detect_vm(&vm_id);
                        if (r > 0 && streq(vm_id, "kvm")) {
                                char uuid[37];

                                fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
                                if (fd >= 0) {
                                        k = loop_read(fd, uuid, 36, false);
                                        safe_close(fd);

                                        if (k >= 36) {
                                                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;
}

static int get_valid_machine_id(int fd, char id[34]) {
        char id_to_validate[34];

        assert(fd >= 0);
        assert(id);

        if (loop_read(fd, id_to_validate, 33, false) == 33 && id_to_validate[32] == '\n') {
                id_to_validate[32] = 0;

                if (id128_is_valid(id_to_validate)) {
                        memcpy(id, id_to_validate, 32);
                        id[32] = '\n';
                        id[33] = 0;
                        return 0;
                }
        }

        return -EINVAL;
}

static int write_machine_id(int fd, char id[34]) {
        assert(fd >= 0);
        assert(id);
        lseek(fd, 0, SEEK_SET);

        if (loop_write(fd, id, 33, false) == 33)
                return 0;

        return -errno;
}

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;

        if (isempty(root))
                etc_machine_id = "/etc/machine-id";
        else {
                char *x;

                x = strappenda(root, "/etc/machine-id");
                etc_machine_id = path_kill_slashes(x);
        }

        r = path_is_mount_point(etc_machine_id, false);
        if (r < 0)
                return log_error_errno(r, "Failed to determine wether %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 = get_valid_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 = is_fd_on_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);
        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);
        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;
}

int machine_id_setup(const char *root) {
        const char *etc_machine_id, *run_machine_id;
        _cleanup_close_ int fd = -1;
        bool writable = true;
        struct stat st;
        char id[34]; /* 32 + \n + \0 */
        int r;

        if (isempty(root))  {
                etc_machine_id = "/etc/machine-id";
                run_machine_id = "/run/machine-id";
        } else {
                char *x;

                x = strappenda(root, "/etc/machine-id");
                etc_machine_id = path_kill_slashes(x);

                x = strappenda(root, "/run/machine-id");
                run_machine_id = path_kill_slashes(x);
        }

        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("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;
                }
        }

        if (fstat(fd, &st) < 0)
                return log_error_errno(errno, "fstat() failed: %m");

        if (S_ISREG(st.st_mode) && get_valid_machine_id(fd, id) == 0)
                return 0;

        /* Hmm, so, the id currently stored is not useful, then let's
         * generate one */

        r = generate(id, root);
        if (r < 0)
                return r;

        if (S_ISREG(st.st_mode) && 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);
        }
        if (r < 0) {
                log_error_errno(r, "Cannot write %s: %m", run_machine_id);
                unlink(run_machine_id);
                return r;
        }

        /* And now, let's mount it over */
        r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
        if (r < 0) {
                log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id);
                unlink_noerrno(run_machine_id);
                return -errno;
        }

        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;
}