summaryrefslogtreecommitdiff
path: root/src/systemd-random-seed/random-seed.c
blob: 6748bb9dd33cd70255b370dbcae6f865f879082c (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
/***
  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 <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

#include "alloc-util.h"
#include "fd-util.h"
#include "io-util.h"
#include "log.h"
#include "mkdir.h"
#include "string-util.h"
#include "util.h"

#define POOL_SIZE_MIN 512

int main(int argc, char *argv[]) {
        _cleanup_close_ int seed_fd = -1, random_fd = -1;
        _cleanup_free_ void* buf = NULL;
        size_t buf_size = 0;
        ssize_t k;
        int r, open_rw_error;
        FILE *f;
        bool refresh_seed_file = true;

        if (argc != 2) {
                log_error("This program requires one argument.");
                return EXIT_FAILURE;
        }

        log_set_target(LOG_TARGET_AUTO);
        log_parse_environment();
        log_open();

        umask(0022);

        /* Read pool size, if possible */
        f = fopen("/proc/sys/kernel/random/poolsize", "re");
        if (f) {
                if (fscanf(f, "%zu", &buf_size) > 0)
                        /* poolsize is in bits on 2.6, but we want bytes */
                        buf_size /= 8;

                fclose(f);
        }

        if (buf_size <= POOL_SIZE_MIN)
                buf_size = POOL_SIZE_MIN;

        buf = malloc(buf_size);
        if (!buf) {
                r = log_oom();
                goto finish;
        }

        r = mkdir_parents_label(RANDOM_SEED, 0755);
        if (r < 0) {
                log_error_errno(r, "Failed to create directory " RANDOM_SEED_DIR ": %m");
                goto finish;
        }

        /* When we load the seed we read it and write it to the device
         * and then immediately update the saved seed with new data,
         * to make sure the next boot gets seeded differently. */

        if (streq(argv[1], "load")) {

                seed_fd = open(RANDOM_SEED, O_RDWR|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600);
                open_rw_error = -errno;
                if (seed_fd < 0) {
                        refresh_seed_file = false;

                        seed_fd = open(RANDOM_SEED, O_RDONLY|O_CLOEXEC|O_NOCTTY);
                        if (seed_fd < 0) {
                                bool missing = errno == ENOENT;

                                log_full_errno(missing ? LOG_DEBUG : LOG_ERR,
                                               open_rw_error, "Failed to open " RANDOM_SEED " for writing: %m");
                                r = log_full_errno(missing ? LOG_DEBUG : LOG_ERR,
                                                   errno, "Failed to open " RANDOM_SEED " for reading: %m");
                                if (missing)
                                        r = 0;

                                goto finish;
                        }
                }

                random_fd = open("/dev/urandom", O_RDWR|O_CLOEXEC|O_NOCTTY, 0600);
                if (random_fd < 0) {
                        random_fd = open("/dev/urandom", O_WRONLY|O_CLOEXEC|O_NOCTTY, 0600);
                        if (random_fd < 0) {
                                r = log_error_errno(errno, "Failed to open /dev/urandom: %m");
                                goto finish;
                        }
                }

                k = loop_read(seed_fd, buf, buf_size, false);
                if (k < 0)
                        r = log_error_errno(k, "Failed to read seed from " RANDOM_SEED ": %m");
                else if (k == 0) {
                        r = 0;
                        log_debug("Seed file " RANDOM_SEED " not yet initialized, proceeding.");
                } else {
                        (void) lseek(seed_fd, 0, SEEK_SET);

                        r = loop_write(random_fd, buf, (size_t) k, false);
                        if (r < 0)
                                log_error_errno(r, "Failed to write seed to /dev/urandom: %m");
                }

        } else if (streq(argv[1], "save")) {

                seed_fd = open(RANDOM_SEED, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600);
                if (seed_fd < 0) {
                        r = log_error_errno(errno, "Failed to open " RANDOM_SEED ": %m");
                        goto finish;
                }

                random_fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
                if (random_fd < 0) {
                        r = log_error_errno(errno, "Failed to open /dev/urandom: %m");
                        goto finish;
                }

        } else {
                log_error("Unknown verb '%s'.", argv[1]);
                r = -EINVAL;
                goto finish;
        }

        if (refresh_seed_file) {

                /* This is just a safety measure. Given that we are root and
                 * most likely created the file ourselves the mode and owner
                 * should be correct anyway. */
                (void) fchmod(seed_fd, 0600);
                (void) fchown(seed_fd, 0, 0);

                k = loop_read(random_fd, buf, buf_size, false);
                if (k < 0) {
                        r = log_error_errno(k, "Failed to read new seed from /dev/urandom: %m");
                        goto finish;
                }
                if (k == 0) {
                        log_error("Got EOF while reading from /dev/urandom.");
                        r = -EIO;
                        goto finish;
                }

                r = loop_write(seed_fd, buf, (size_t) k, false);
                if (r < 0)
                        log_error_errno(r, "Failed to write new random seed file: %m");
        }

finish:
        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}