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
|
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "alloc-util.h"
#include "bootctl.h"
#include "bootctl-random-seed.h"
#include "bootctl-util.h"
#include "efi-api.h"
#include "env-util.h"
#include "fd-util.h"
#include "find-esp.h"
#include "fs-util.h"
#include "glyph-util.h"
#include "io-util.h"
#include "mkdir.h"
#include "path-util.h"
#include "random-util.h"
#include "sha256.h"
#include "tmpfile-util.h"
#include "umask-util.h"
static int random_seed_verify_permissions(int fd, mode_t expected_type) {
_cleanup_free_ char *full_path = NULL;
struct stat st;
int r;
assert(fd >= 0);
r = fd_get_path(fd, &full_path);
if (r < 0)
return log_error_errno(r, "Unable to determine full path of random seed fd: %m");
if (fstat(fd, &st) < 0)
return log_error_errno(errno, "Unable to stat %s: %m", full_path);
if (((st.st_mode ^ expected_type) & S_IFMT) != 0)
return log_error_errno(SYNTHETIC_ERRNO(EBADF),
"Unexpected inode type when validating random seed access mode on %s: %m", full_path);
if ((st.st_mode & 0007) == 0) /* All world bits are off? Then all is good */
return 0;
if (S_ISREG(expected_type))
log_warning("%s Random seed file '%s' is world accessible, which is a security hole! %s",
special_glyph(SPECIAL_GLYPH_WARNING_SIGN), full_path, special_glyph(SPECIAL_GLYPH_WARNING_SIGN));
else {
assert(S_ISDIR(expected_type));
log_warning("%s Mount point '%s' which backs the random seed file is world accessible, which is a security hole! %s",
special_glyph(SPECIAL_GLYPH_WARNING_SIGN), full_path, special_glyph(SPECIAL_GLYPH_WARNING_SIGN));
}
return 1;
}
static int set_system_token(void) {
uint8_t buffer[RANDOM_EFI_SEED_SIZE];
size_t token_size;
int r;
if (!arg_touch_variables)
return 0;
if (arg_root) {
log_warning("Acting on %s, skipping EFI variable setup.",
arg_image ? "image" : "root directory");
return 0;
}
if (!is_efi_boot()) {
log_notice("Not booted with EFI, skipping EFI variable setup.");
return 0;
}
r = getenv_bool("SYSTEMD_WRITE_SYSTEM_TOKEN");
if (r < 0) {
if (r != -ENXIO)
log_warning_errno(r, "Failed to parse $SYSTEMD_WRITE_SYSTEM_TOKEN, ignoring.");
} else if (r == 0) {
log_notice("Not writing system token, because $SYSTEMD_WRITE_SYSTEM_TOKEN is set to false.");
return 0;
}
r = efi_get_variable(EFI_LOADER_VARIABLE(LoaderSystemToken), NULL, NULL, &token_size);
if (r == -ENODATA)
log_debug_errno(r, "LoaderSystemToken EFI variable is invalid (too short?), replacing.");
else if (r < 0) {
if (r != -ENOENT)
return log_error_errno(r, "Failed to test system token validity: %m");
} else {
if (token_size >= sizeof(buffer)) {
/* Let's avoid writes if we can, and initialize this only once. */
log_debug("System token already written, not updating.");
return 0;
}
log_debug("Existing system token size (%zu) does not match our expectations (%zu), replacing.", token_size, sizeof(buffer));
}
r = crypto_random_bytes(buffer, sizeof(buffer));
if (r < 0)
return log_error_errno(r, "Failed to acquire random seed: %m");
/* Let's write this variable with an umask in effect, so that unprivileged users can't see the token
* and possibly get identification information or too much insight into the kernel's entropy pool
* state. */
WITH_UMASK(0077) {
r = efi_set_variable(EFI_LOADER_VARIABLE(LoaderSystemToken), buffer, sizeof(buffer));
if (r < 0) {
if (!arg_graceful)
return log_error_errno(r, "Failed to write 'LoaderSystemToken' EFI variable: %m");
if (r == -EINVAL)
log_notice_errno(r, "Unable to write 'LoaderSystemToken' EFI variable (firmware problem?), ignoring: %m");
else
log_notice_errno(r, "Unable to write 'LoaderSystemToken' EFI variable, ignoring: %m");
} else
log_info("Successfully initialized system token in EFI variable with %zu bytes.", sizeof(buffer));
}
return 0;
}
int install_random_seed(const char *esp) {
_cleanup_close_ int esp_fd = -EBADF, loader_dir_fd = -EBADF, fd = -EBADF;
_cleanup_free_ char *tmp = NULL;
uint8_t buffer[RANDOM_EFI_SEED_SIZE];
struct sha256_ctx hash_state;
bool refreshed, warned = false;
int r;
assert(esp);
assert_cc(RANDOM_EFI_SEED_SIZE == SHA256_DIGEST_SIZE);
esp_fd = open(esp, O_DIRECTORY|O_RDONLY|O_CLOEXEC);
if (esp_fd < 0)
return log_error_errno(errno, "Failed to open ESP directory '%s': %m", esp);
(void) random_seed_verify_permissions(esp_fd, S_IFDIR);
loader_dir_fd = open_mkdir_at(esp_fd, "loader", O_DIRECTORY|O_RDONLY|O_CLOEXEC|O_NOFOLLOW, 0775);
if (loader_dir_fd < 0)
return log_error_errno(loader_dir_fd, "Failed to open loader directory '%s/loader': %m", esp);
r = crypto_random_bytes(buffer, sizeof(buffer));
if (r < 0)
return log_error_errno(r, "Failed to acquire random seed: %m");
sha256_init_ctx(&hash_state);
sha256_process_bytes_and_size(buffer, sizeof(buffer), &hash_state);
fd = openat(loader_dir_fd, "random-seed", O_NOFOLLOW|O_CLOEXEC|O_RDONLY|O_NOCTTY);
if (fd < 0) {
if (errno != ENOENT)
return log_error_errno(errno, "Failed to open old random seed file: %m");
sha256_process_bytes(&(const ssize_t) { 0 }, sizeof(ssize_t), &hash_state);
refreshed = false;
} else {
ssize_t n;
warned = random_seed_verify_permissions(fd, S_IFREG) > 0;
/* Hash the old seed in so that we never regress in entropy. */
n = read(fd, buffer, sizeof(buffer));
if (n < 0)
return log_error_errno(errno, "Failed to read old random seed file: %m");
sha256_process_bytes_and_size(buffer, n, &hash_state);
fd = safe_close(fd);
refreshed = n > 0;
}
sha256_finish_ctx(&hash_state, buffer);
if (tempfn_random("random-seed", "bootctl", &tmp) < 0)
return log_oom();
fd = openat(loader_dir_fd, tmp, O_CREAT|O_EXCL|O_NOFOLLOW|O_NOCTTY|O_WRONLY|O_CLOEXEC, 0600);
if (fd < 0)
return log_error_errno(fd, "Failed to open random seed file for writing: %m");
if (!warned) /* only warn once per seed file */
(void) random_seed_verify_permissions(fd, S_IFREG);
r = loop_write(fd, buffer, sizeof(buffer));
if (r < 0) {
log_error_errno(r, "Failed to write random seed file: %m");
goto fail;
}
if (fsync(fd) < 0 || fsync(loader_dir_fd) < 0) {
r = log_error_errno(errno, "Failed to sync random seed file: %m");
goto fail;
}
if (renameat(loader_dir_fd, tmp, loader_dir_fd, "random-seed") < 0) {
r = log_error_errno(errno, "Failed to move random seed file into place: %m");
goto fail;
}
tmp = mfree(tmp);
if (syncfs(fd) < 0)
return log_error_errno(errno, "Failed to sync ESP file system: %m");
log_info("Random seed file %s/loader/random-seed successfully %s (%zu bytes).", esp, refreshed ? "refreshed" : "written", sizeof(buffer));
return set_system_token();
fail:
assert(tmp);
(void) unlinkat(loader_dir_fd, tmp, 0);
return r;
}
int verb_random_seed(int argc, char *argv[], void *userdata) {
int r;
r = find_esp_and_warn(arg_root, arg_esp_path, false, &arg_esp_path, NULL, NULL, NULL, NULL, NULL);
if (r == -ENOKEY) {
/* find_esp_and_warn() doesn't warn about ENOKEY, so let's do that on our own */
if (!arg_graceful)
return log_error_errno(r, "Unable to find ESP.");
log_notice("No ESP found, not initializing random seed.");
return 0;
}
if (r < 0)
return r;
r = install_random_seed(arg_esp_path);
if (r < 0)
return r;
return 0;
}
|
