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0bb2f0f1 ZJS |
1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
2 | ||
3 | #include <errno.h> | |
4 | #include <fcntl.h> | |
5 | #include <limits.h> | |
6 | #include <linux/fs.h> | |
0bb2f0f1 | 7 | #include <stdlib.h> |
0bb2f0f1 ZJS |
8 | #include <sys/stat.h> |
9 | #include <unistd.h> | |
10 | ||
11 | #include "sd-id128.h" | |
12 | ||
13 | #include "alloc-util.h" | |
14 | #include "chattr-util.h" | |
15 | #include "efivars.h" | |
16 | #include "fd-util.h" | |
17 | #include "io-util.h" | |
18 | #include "macro.h" | |
19 | #include "stdio-util.h" | |
20 | #include "strv.h" | |
21 | #include "time-util.h" | |
22 | #include "utf8.h" | |
c7d26acc | 23 | #include "virt.h" |
0bb2f0f1 ZJS |
24 | |
25 | #if ENABLE_EFI | |
26 | ||
7229ec02 ZJS |
27 | /* Reads from efivarfs sometimes fail with EINTR. Retry that many times. */ |
28 | #define EFI_N_RETRIES 5 | |
29 | #define EFI_RETRY_DELAY (50 * USEC_PER_MSEC) | |
30 | ||
0bb2f0f1 ZJS |
31 | char* efi_variable_path(sd_id128_t vendor, const char *name) { |
32 | char *p; | |
33 | ||
34 | if (asprintf(&p, | |
35 | "/sys/firmware/efi/efivars/%s-" SD_ID128_UUID_FORMAT_STR, | |
36 | name, SD_ID128_FORMAT_VAL(vendor)) < 0) | |
37 | return NULL; | |
38 | ||
39 | return p; | |
40 | } | |
41 | ||
42 | int efi_get_variable( | |
43 | sd_id128_t vendor, | |
44 | const char *name, | |
45 | uint32_t *ret_attribute, | |
46 | void **ret_value, | |
47 | size_t *ret_size) { | |
48 | ||
49 | _cleanup_close_ int fd = -1; | |
50 | _cleanup_free_ char *p = NULL; | |
51 | _cleanup_free_ void *buf = NULL; | |
52 | struct stat st; | |
698564d1 | 53 | usec_t begin; |
0bb2f0f1 ZJS |
54 | uint32_t a; |
55 | ssize_t n; | |
56 | ||
57 | assert(name); | |
58 | ||
59 | p = efi_variable_path(vendor, name); | |
60 | if (!p) | |
61 | return -ENOMEM; | |
62 | ||
63 | if (!ret_value && !ret_size && !ret_attribute) { | |
7229ec02 ZJS |
64 | /* If caller is not interested in anything, just check if the variable exists and is |
65 | * readable. */ | |
0bb2f0f1 ZJS |
66 | if (access(p, R_OK) < 0) |
67 | return -errno; | |
68 | ||
69 | return 0; | |
70 | } | |
71 | ||
698564d1 LP |
72 | if (DEBUG_LOGGING) |
73 | begin = now(CLOCK_MONOTONIC); | |
74 | ||
0bb2f0f1 ZJS |
75 | fd = open(p, O_RDONLY|O_NOCTTY|O_CLOEXEC); |
76 | if (fd < 0) | |
7229ec02 | 77 | return log_debug_errno(errno, "open(\"%s\") failed: %m", p); |
0bb2f0f1 ZJS |
78 | |
79 | if (fstat(fd, &st) < 0) | |
80 | return -errno; | |
81 | if (st.st_size < 4) | |
82 | return -ENODATA; | |
83 | if (st.st_size > 4*1024*1024 + 4) | |
84 | return -E2BIG; | |
85 | ||
86 | if (ret_value || ret_attribute) { | |
7229ec02 ZJS |
87 | /* The kernel ratelimits reads from the efivarfs because EFI is inefficient, and we'll |
88 | * occasionally fail with EINTR here. A slowdown is better than a failure for us, so | |
89 | * retry a few times and eventually fail with -EBUSY. | |
90 | * | |
91 | * See https://github.com/torvalds/linux/blob/master/fs/efivarfs/file.c#L75 | |
92 | * and | |
93 | * https://github.com/torvalds/linux/commit/bef3efbeb897b56867e271cdbc5f8adaacaeb9cd. | |
94 | */ | |
95 | for (unsigned try = 0;; try++) { | |
96 | n = read(fd, &a, sizeof(a)); | |
97 | if (n >= 0) | |
98 | break; | |
99 | log_debug_errno(errno, "read from \"%s\" failed: %m", p); | |
100 | if (errno != EINTR) | |
101 | return -errno; | |
102 | if (try >= EFI_N_RETRIES) | |
103 | return -EBUSY; | |
104 | usleep(EFI_RETRY_DELAY); | |
105 | } | |
106 | ||
0bb2f0f1 ZJS |
107 | if (n != sizeof(a)) |
108 | return -EIO; | |
109 | } | |
110 | ||
111 | if (ret_value) { | |
112 | buf = malloc(st.st_size - 4 + 2); | |
113 | if (!buf) | |
114 | return -ENOMEM; | |
115 | ||
116 | n = read(fd, buf, (size_t) st.st_size - 4); | |
117 | if (n < 0) | |
118 | return -errno; | |
35b9eb0a | 119 | assert(n <= st.st_size - 4); |
0bb2f0f1 ZJS |
120 | |
121 | /* Always NUL terminate (2 bytes, to protect UTF-16) */ | |
861f1789 LP |
122 | ((char*) buf)[n] = 0; |
123 | ((char*) buf)[n + 1] = 0; | |
35b9eb0a ZJS |
124 | } else |
125 | /* Assume that the reported size is accurate */ | |
126 | n = st.st_size - 4; | |
0bb2f0f1 | 127 | |
698564d1 LP |
128 | if (DEBUG_LOGGING) { |
129 | char ts[FORMAT_TIMESPAN_MAX]; | |
130 | usec_t end; | |
131 | ||
132 | end = now(CLOCK_MONOTONIC); | |
133 | if (end > begin + EFI_RETRY_DELAY) | |
134 | log_debug("Detected slow EFI variable read access on " SD_ID128_FORMAT_STR "-%s: %s", | |
135 | SD_ID128_FORMAT_VAL(vendor), name, format_timespan(ts, sizeof(ts), end - begin, 1)); | |
136 | } | |
137 | ||
0bb2f0f1 ZJS |
138 | /* Note that efivarfs interestingly doesn't require ftruncate() to update an existing EFI variable |
139 | * with a smaller value. */ | |
140 | ||
141 | if (ret_attribute) | |
142 | *ret_attribute = a; | |
143 | ||
144 | if (ret_value) | |
145 | *ret_value = TAKE_PTR(buf); | |
146 | ||
147 | if (ret_size) | |
35b9eb0a | 148 | *ret_size = n; |
0bb2f0f1 ZJS |
149 | |
150 | return 0; | |
151 | } | |
152 | ||
153 | int efi_get_variable_string(sd_id128_t vendor, const char *name, char **p) { | |
154 | _cleanup_free_ void *s = NULL; | |
155 | size_t ss = 0; | |
156 | int r; | |
157 | char *x; | |
158 | ||
159 | r = efi_get_variable(vendor, name, NULL, &s, &ss); | |
160 | if (r < 0) | |
161 | return r; | |
162 | ||
163 | x = utf16_to_utf8(s, ss); | |
164 | if (!x) | |
165 | return -ENOMEM; | |
166 | ||
167 | *p = x; | |
168 | return 0; | |
169 | } | |
170 | ||
171 | int efi_set_variable( | |
172 | sd_id128_t vendor, | |
173 | const char *name, | |
174 | const void *value, | |
175 | size_t size) { | |
176 | ||
177 | struct var { | |
178 | uint32_t attr; | |
179 | char buf[]; | |
180 | } _packed_ * _cleanup_free_ buf = NULL; | |
181 | _cleanup_free_ char *p = NULL; | |
182 | _cleanup_close_ int fd = -1; | |
183 | bool saved_flags_valid = false; | |
184 | unsigned saved_flags; | |
185 | int r; | |
186 | ||
187 | assert(name); | |
188 | assert(value || size == 0); | |
189 | ||
190 | p = efi_variable_path(vendor, name); | |
191 | if (!p) | |
192 | return -ENOMEM; | |
193 | ||
194 | /* Newer efivarfs protects variables that are not in a whitelist with FS_IMMUTABLE_FL by default, to protect | |
195 | * them for accidental removal and modification. We are not changing these variables accidentally however, | |
196 | * hence let's unset the bit first. */ | |
197 | ||
198 | r = chattr_path(p, 0, FS_IMMUTABLE_FL, &saved_flags); | |
199 | if (r < 0 && r != -ENOENT) | |
200 | log_debug_errno(r, "Failed to drop FS_IMMUTABLE_FL flag from '%s', ignoring: %m", p); | |
201 | ||
202 | saved_flags_valid = r >= 0; | |
203 | ||
204 | if (size == 0) { | |
205 | if (unlink(p) < 0) { | |
206 | r = -errno; | |
207 | goto finish; | |
208 | } | |
209 | ||
210 | return 0; | |
211 | } | |
212 | ||
213 | fd = open(p, O_WRONLY|O_CREAT|O_NOCTTY|O_CLOEXEC, 0644); | |
214 | if (fd < 0) { | |
215 | r = -errno; | |
216 | goto finish; | |
217 | } | |
218 | ||
219 | buf = malloc(sizeof(uint32_t) + size); | |
220 | if (!buf) { | |
221 | r = -ENOMEM; | |
222 | goto finish; | |
223 | } | |
224 | ||
225 | buf->attr = EFI_VARIABLE_NON_VOLATILE|EFI_VARIABLE_BOOTSERVICE_ACCESS|EFI_VARIABLE_RUNTIME_ACCESS; | |
226 | memcpy(buf->buf, value, size); | |
227 | ||
228 | r = loop_write(fd, buf, sizeof(uint32_t) + size, false); | |
229 | if (r < 0) | |
230 | goto finish; | |
231 | ||
232 | r = 0; | |
233 | ||
234 | finish: | |
235 | if (saved_flags_valid) { | |
236 | int q; | |
237 | ||
238 | /* Restore the original flags field, just in case */ | |
239 | if (fd < 0) | |
240 | q = chattr_path(p, saved_flags, FS_IMMUTABLE_FL, NULL); | |
241 | else | |
242 | q = chattr_fd(fd, saved_flags, FS_IMMUTABLE_FL, NULL); | |
243 | if (q < 0) | |
244 | log_debug_errno(q, "Failed to restore FS_IMMUTABLE_FL on '%s', ignoring: %m", p); | |
245 | } | |
246 | ||
247 | return r; | |
248 | } | |
249 | ||
250 | int efi_set_variable_string(sd_id128_t vendor, const char *name, const char *v) { | |
251 | _cleanup_free_ char16_t *u16 = NULL; | |
252 | ||
253 | u16 = utf8_to_utf16(v, strlen(v)); | |
254 | if (!u16) | |
255 | return -ENOMEM; | |
256 | ||
257 | return efi_set_variable(vendor, name, u16, (char16_strlen(u16) + 1) * sizeof(char16_t)); | |
258 | } | |
259 | ||
c7d26acc | 260 | bool is_efi_boot(void) { |
f46ba939 | 261 | static int cache = -1; |
c7d26acc | 262 | |
f46ba939 LP |
263 | if (cache < 0) { |
264 | if (detect_container() > 0) | |
265 | cache = false; | |
266 | else | |
267 | cache = access("/sys/firmware/efi/", F_OK) >= 0; | |
268 | } | |
269 | ||
270 | return cache; | |
c7d26acc AP |
271 | } |
272 | ||
273 | static int read_flag(const char *varname) { | |
274 | _cleanup_free_ void *v = NULL; | |
275 | uint8_t b; | |
276 | size_t s; | |
277 | int r; | |
278 | ||
279 | if (!is_efi_boot()) /* If this is not an EFI boot, assume the queried flags are zero */ | |
280 | return 0; | |
281 | ||
282 | r = efi_get_variable(EFI_VENDOR_GLOBAL, varname, NULL, &v, &s); | |
283 | if (r < 0) | |
284 | return r; | |
285 | ||
286 | if (s != 1) | |
287 | return -EINVAL; | |
288 | ||
289 | b = *(uint8_t *)v; | |
290 | return !!b; | |
291 | } | |
292 | ||
293 | bool is_efi_secure_boot(void) { | |
f46ba939 LP |
294 | static int cache = -1; |
295 | ||
296 | if (cache < 0) | |
297 | cache = read_flag("SecureBoot"); | |
298 | ||
299 | return cache > 0; | |
c7d26acc AP |
300 | } |
301 | ||
302 | bool is_efi_secure_boot_setup_mode(void) { | |
f46ba939 LP |
303 | static int cache = -1; |
304 | ||
305 | if (cache < 0) | |
306 | cache = read_flag("SetupMode"); | |
307 | ||
308 | return cache > 0; | |
c7d26acc AP |
309 | } |
310 | ||
2536752d | 311 | int systemd_efi_options_variable(char **line) { |
53aa0d02 ZJS |
312 | const char *e; |
313 | int r; | |
314 | ||
315 | assert(line); | |
316 | ||
317 | /* For testing purposes it is sometimes useful to be able to override this */ | |
318 | e = secure_getenv("SYSTEMD_EFI_OPTIONS"); | |
319 | if (e) { | |
320 | char *m; | |
321 | ||
322 | m = strdup(e); | |
323 | if (!m) | |
324 | return -ENOMEM; | |
325 | ||
326 | *line = m; | |
327 | return 0; | |
328 | } | |
329 | ||
484f4e5b LP |
330 | /* In SecureBoot mode this is probably not what you want. As your cmdline is cryptographically signed |
331 | * like when using Type #2 EFI Unified Kernel Images (https://systemd.io/BOOT_LOADER_SPECIFICATION/) | |
332 | * The user's intention is then that the cmdline should not be modified. You want to make sure that | |
333 | * the system starts up as exactly specified in the signed artifact. | |
334 | * | |
335 | * (NB: to make testing purposes we still check the $SYSTEMD_EFI_OPTIONS env var above, even when in | |
336 | * SecureBoot mode.) */ | |
337 | if (is_efi_secure_boot()) { | |
338 | _cleanup_free_ char *k; | |
339 | ||
340 | k = efi_variable_path(EFI_VENDOR_SYSTEMD, "SystemdOptions"); | |
341 | if (!k) | |
342 | return -ENOMEM; | |
343 | ||
344 | /* Let's be helpful with the returned error and check if the variable exists at all. If it | |
345 | * does, let's return a recognizable error (EPERM), and if not ENODATA. */ | |
346 | ||
347 | if (access(k, F_OK) < 0) | |
a0fa2683 | 348 | return errno == ENOENT ? -ENODATA : -errno; |
484f4e5b LP |
349 | |
350 | return -EPERM; | |
351 | } | |
352 | ||
53aa0d02 ZJS |
353 | r = efi_get_variable_string(EFI_VENDOR_SYSTEMD, "SystemdOptions", line); |
354 | if (r == -ENOENT) | |
355 | return -ENODATA; | |
356 | ||
357 | return r; | |
358 | } | |
0bb2f0f1 | 359 | #endif |