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d7ccca2e LP |
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 General Public License as published by | |
10 | the Free Software Foundation; either version 2 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 | General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU 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 "machine-id-setup.h" | |
31 | #include "macro.h" | |
32 | #include "util.h" | |
33 | #include "log.h" | |
34 | ||
8d41a963 LP |
35 | static void make_v4_uuid(unsigned char *id) { |
36 | /* Stolen from generate_random_uuid() of drivers/char/random.c | |
37 | * in the kernel sources */ | |
38 | ||
39 | /* Set UUID version to 4 --- truly random generation */ | |
40 | id[6] = (id[6] & 0x0F) | 0x40; | |
41 | ||
42 | /* Set the UUID variant to DCE */ | |
43 | id[8] = (id[8] & 0x3F) | 0x80; | |
44 | } | |
45 | ||
d7ccca2e LP |
46 | static int generate(char id[34]) { |
47 | int fd; | |
8d41a963 LP |
48 | unsigned char buf[16], *p; |
49 | char *q; | |
d7ccca2e LP |
50 | ssize_t k; |
51 | ||
52 | assert(id); | |
53 | ||
54 | /* First, try reading the D-Bus machine id, unless it is a symlink */ | |
8d41a963 LP |
55 | fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW); |
56 | if (fd >= 0) { | |
d7ccca2e LP |
57 | |
58 | k = loop_read(fd, id, 33, false); | |
59 | close_nointr_nofail(fd); | |
60 | ||
61 | if (k >= 32) { | |
62 | id[32] = '\n'; | |
63 | id[33] = 0; | |
64 | ||
65 | log_info("Initializing machine ID from D-Bus machine ID."); | |
66 | return 0; | |
67 | } | |
68 | } | |
69 | ||
70 | /* If that didn't work, generate a random machine id */ | |
8d41a963 LP |
71 | fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY); |
72 | if (fd < 0) { | |
d7ccca2e LP |
73 | log_error("Failed to open /dev/urandom: %m"); |
74 | return -errno; | |
75 | } | |
76 | ||
77 | k = loop_read(fd, buf, sizeof(buf), false); | |
78 | close_nointr_nofail(fd); | |
79 | ||
80 | if (k != sizeof(buf)) { | |
81 | log_error("Failed to read /dev/urandom: %s", strerror(k < 0 ? -k : EIO)); | |
82 | return k < 0 ? (int) k : -EIO; | |
83 | } | |
84 | ||
8d41a963 LP |
85 | /* Turn this into a valid v4 UUID, to be nice. Note that we |
86 | * only guarantee this for newly generated UUIDs, not for | |
87 | * pre-existing ones.*/ | |
88 | make_v4_uuid(buf); | |
89 | ||
d7ccca2e LP |
90 | for (p = buf, q = id; p < buf + sizeof(buf); p++, q += 2) { |
91 | q[0] = hexchar(*p >> 4); | |
92 | q[1] = hexchar(*p & 15); | |
93 | } | |
94 | ||
95 | id[32] = '\n'; | |
96 | id[33] = 0; | |
97 | ||
98 | log_info("Initializing machine ID from random generator."); | |
99 | ||
100 | return 0; | |
101 | } | |
102 | ||
103 | int machine_id_setup(void) { | |
104 | int fd, r; | |
105 | bool writable; | |
106 | struct stat st; | |
107 | char id[34]; /* 32 + \n + \0 */ | |
108 | mode_t m; | |
109 | ||
110 | m = umask(0000); | |
111 | ||
76526bad LP |
112 | /* We create this 0444, to indicate that this isn't really |
113 | * something you should ever modify. Of course, since the file | |
114 | * will be owned by root it doesn't matter much, but maybe | |
115 | * people look. */ | |
116 | ||
8d41a963 LP |
117 | fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444); |
118 | if (fd >= 0) | |
d7ccca2e LP |
119 | writable = true; |
120 | else { | |
8d41a963 LP |
121 | fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY); |
122 | if (fd < 0) { | |
d7ccca2e LP |
123 | umask(m); |
124 | log_error("Cannot open /etc/machine-id: %m"); | |
125 | return -errno; | |
126 | } | |
127 | ||
128 | writable = false; | |
129 | } | |
130 | ||
131 | umask(m); | |
132 | ||
133 | if (fstat(fd, &st) < 0) { | |
134 | log_error("fstat() failed: %m"); | |
135 | r = -errno; | |
136 | goto finish; | |
137 | } | |
138 | ||
139 | if (S_ISREG(st.st_mode)) { | |
140 | if (loop_read(fd, id, 32, false) >= 32) { | |
141 | r = 0; | |
142 | goto finish; | |
143 | } | |
144 | } | |
145 | ||
146 | /* Hmm, so, the id currently stored is not useful, then let's | |
147 | * generate one */ | |
148 | ||
8d41a963 LP |
149 | r = generate(id); |
150 | if (r < 0) | |
d7ccca2e LP |
151 | goto finish; |
152 | ||
153 | if (S_ISREG(st.st_mode) && writable) { | |
154 | lseek(fd, 0, SEEK_SET); | |
155 | ||
156 | if (loop_write(fd, id, 33, false) == 33) { | |
157 | r = 0; | |
158 | goto finish; | |
159 | } | |
160 | } | |
161 | ||
162 | close_nointr_nofail(fd); | |
163 | fd = -1; | |
164 | ||
165 | /* Hmm, we couldn't write it? So let's write it to | |
2b583ce6 | 166 | * /run/systemd/machine-id as a replacement */ |
d7ccca2e | 167 | |
2b583ce6 | 168 | mkdir_p("/run/systemd", 0755); |
d7ccca2e | 169 | |
4c12626c | 170 | m = umask(0022); |
8d41a963 | 171 | r = write_one_line_file("/run/systemd/machine-id", id); |
4c12626c LP |
172 | umask(m); |
173 | ||
8d41a963 | 174 | if (r < 0) { |
2b583ce6 | 175 | log_error("Cannot write /run/systemd/machine-id: %s", strerror(-r)); |
d7ccca2e | 176 | |
2b583ce6 | 177 | unlink("/run/systemd/machine-id"); |
d7ccca2e LP |
178 | goto finish; |
179 | } | |
180 | ||
181 | /* And now, let's mount it over */ | |
2b583ce6 KS |
182 | r = mount("/run/systemd/machine-id", "/etc/machine-id", "bind", MS_BIND|MS_RDONLY, NULL) < 0 ? -errno : 0; |
183 | unlink("/run/systemd/machine-id"); | |
d7ccca2e LP |
184 | |
185 | if (r < 0) | |
186 | log_error("Failed to mount /etc/machine-id: %s", strerror(-r)); | |
187 | else | |
9b4f818b | 188 | log_info("Installed transient /etc/machine-id file."); |
d7ccca2e LP |
189 | |
190 | finish: | |
191 | ||
192 | if (fd >= 0) | |
193 | close_nointr_nofail(fd); | |
194 | ||
195 | return r; | |
196 | } |