machine-id-setup.c 4.66 KB
Newer Older
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
/*-*- 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 General Public License as published by
  the Free Software Foundation; either version 2 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
  General Public License for more details.

  You should have received a copy of the GNU 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 "machine-id-setup.h"
#include "macro.h"
#include "util.h"
#include "log.h"

static int generate(char id[34]) {
        int fd;
        char buf[16];
        char *p, *q;
        ssize_t k;

        assert(id);

        /* First, try reading the D-Bus machine id, unless it is a symlink */
        if ((fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW)) >= 0) {

                k = loop_read(fd, id, 33, false);
                close_nointr_nofail(fd);

                if (k >= 32) {
                        id[32] = '\n';
                        id[33] = 0;

                        log_info("Initializing machine ID from D-Bus machine ID.");
                        return 0;
                }
        }

        /* If that didn't work, generate a random machine id */
        if ((fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY)) < 0) {
                log_error("Failed to open /dev/urandom: %m");
                return -errno;
        }

        k = loop_read(fd, buf, sizeof(buf), false);
        close_nointr_nofail(fd);

        if (k != sizeof(buf)) {
                log_error("Failed to read /dev/urandom: %s", strerror(k < 0 ? -k : EIO));
                return k < 0 ? (int) k : -EIO;
        }

        for (p = buf, q = id; p < buf + 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(void) {
        int fd, r;
        bool writable;
        struct stat st;
        char id[34]; /* 32 + \n + \0 */
        mode_t m;

        m = umask(0000);

        if ((fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0644)) >= 0)
                writable = true;
        else {
                if ((fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY)) < 0) {
                        umask(m);
                        log_error("Cannot open /etc/machine-id: %m");
                        return -errno;
                }

                writable = false;
        }

        umask(m);

        if (fstat(fd, &st) < 0) {
                log_error("fstat() failed: %m");
                r = -errno;
                goto finish;
        }

        if (S_ISREG(st.st_mode)) {
                if (loop_read(fd, id, 32, false) >= 32) {
                        r = 0;
                        goto finish;
                }
        }

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

        if ((r = generate(id)) < 0)
                goto finish;

        if (S_ISREG(st.st_mode) && writable) {
                lseek(fd, 0, SEEK_SET);

                if (loop_write(fd, id, 33, false) == 33) {
                        r = 0;
                        goto finish;
                }
        }

        close_nointr_nofail(fd);
        fd = -1;

        /* Hmm, we couldn't write it? So let's write it to
         * /dev/.systemd/machine-id as a replacement */

        mkdir_p("/dev/.systemd", 0755);

        if ((r = write_one_line_file("/dev/.systemd/machine-id", id)) < 0) {
                log_error("Cannot write /dev/.systemd/machine-id: %s", strerror(-r));

                unlink("/dev/.systemd/machine-id");
                goto finish;
        }

        /* And now, let's mount it over */
        r = mount("/dev/.systemd/machine-id", "/etc/machine-id", "bind", MS_BIND|MS_RDONLY, NULL) < 0 ? -errno : 0;
        unlink("/dev/.systemd/machine-id");

        if (r < 0)
                log_error("Failed to mount /etc/machine-id: %s", strerror(-r));
        else
Lennart Poettering's avatar
Lennart Poettering committed
158
                log_info("Installed transient /etc/machine-id file.");
159
160
161
162
163
164
165
166

finish:

        if (fd >= 0)
                close_nointr_nofail(fd);

        return r;
}