src/shared/efi-loader.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include "alloc-util.h"
   4 #include "efi-loader.h"
   5 #include "env-util.h"
   6 #include "parse-util.h"
   7 #include "path-util.h"
   8 #include "stat-util.h"
   9 #include "strv.h"
  10 #include "tpm-pcr.h"
  11 #include "utf8.h"
  12
  13 #if ENABLE_EFI
  14
  15 static int read_usec(const char *variable, usec_t *ret) {
  16         _cleanup_free_ char *j = NULL;
  17         uint64_t x = 0;
  18         int r;
  19
  20         assert(variable);
  21         assert(ret);
  22
  23         r = efi_get_variable_string(variable, &j);
  24         if (r < 0)
  25                 return r;
  26
  27         r = safe_atou64(j, &x);
  28         if (r < 0)
  29                 return r;
  30
  31         *ret = x;
  32         return 0;
  33 }
  34
  35 int efi_loader_get_boot_usec(usec_t *ret_firmware, usec_t *ret_loader) {
  36         uint64_t x, y;
  37         int r;
  38
  39         assert(ret_firmware);
  40         assert(ret_loader);
  41
  42         if (!is_efi_boot())
  43                 return -EOPNOTSUPP;
  44
  45         r = read_usec(EFI_LOADER_VARIABLE(LoaderTimeInitUSec), &x);
  46         if (r < 0)
  47                 return log_debug_errno(r, "Failed to read LoaderTimeInitUSec: %m");
  48
  49         r = read_usec(EFI_LOADER_VARIABLE(LoaderTimeExecUSec), &y);
  50         if (r < 0)
  51                 return log_debug_errno(r, "Failed to read LoaderTimeExecUSec: %m");
  52
  53         if (y == 0 || y < x || y - x > USEC_PER_HOUR)
  54                 return log_debug_errno(SYNTHETIC_ERRNO(EIO),
  55                                        "Bad LoaderTimeInitUSec=%"PRIu64", LoaderTimeExecUSec=%" PRIu64"; refusing.",
  56                                        x, y);
  57
  58         *ret_firmware = x;
  59         *ret_loader = y;
  60         return 0;
  61 }
  62
  63 int efi_loader_get_device_part_uuid(sd_id128_t *ret) {
  64         _cleanup_free_ char *p = NULL;
  65         int r;
  66         unsigned parsed[16];
  67
  68         if (!is_efi_boot())
  69                 return -EOPNOTSUPP;
  70
  71         r = efi_get_variable_string(EFI_LOADER_VARIABLE(LoaderDevicePartUUID), &p);
  72         if (r < 0)
  73                 return r;
  74
  75         if (sscanf(p, SD_ID128_UUID_FORMAT_STR,
  76                    &parsed[0], &parsed[1], &parsed[2], &parsed[3],
  77                    &parsed[4], &parsed[5], &parsed[6], &parsed[7],
  78                    &parsed[8], &parsed[9], &parsed[10], &parsed[11],
  79                    &parsed[12], &parsed[13], &parsed[14], &parsed[15]) != 16)
  80                 return -EIO;
  81
  82         if (ret)
  83                 for (unsigned i = 0; i < ELEMENTSOF(parsed); i++)
  84                         ret->bytes[i] = parsed[i];
  85
  86         return 0;
  87 }
  88
  89 int efi_loader_get_entries(char ***ret) {
  90         _cleanup_free_ char16_t *entries = NULL;
  91         _cleanup_strv_free_ char **l = NULL;
  92         size_t size;
  93         int r;
  94
  95         assert(ret);
  96
  97         if (!is_efi_boot())
  98                 return -EOPNOTSUPP;
  99
 100         r = efi_get_variable(EFI_LOADER_VARIABLE(LoaderEntries), NULL, (void**) &entries, &size);
 101         if (r < 0)
 102                 return r;
 103
 104         /* The variable contains a series of individually NUL terminated UTF-16 strings. */
 105
 106         for (size_t i = 0, start = 0;; i++) {
 107                 _cleanup_free_ char *decoded = NULL;
 108                 bool end;
 109
 110                 /* Is this the end of the variable's data? */
 111                 end = i * sizeof(char16_t) >= size;
 112
 113                 /* Are we in the middle of a string? (i.e. not at the end of the variable, nor at a NUL terminator?) If
 114                  * so, let's go to the next entry. */
 115                 if (!end && entries[i] != 0)
 116                         continue;
 117
 118                 /* We reached the end of a string, let's decode it into UTF-8 */
 119                 decoded = utf16_to_utf8(entries + start, (i - start) * sizeof(char16_t));
 120                 if (!decoded)
 121                         return -ENOMEM;
 122
 123                 if (efi_loader_entry_name_valid(decoded)) {
 124                         r = strv_consume(&l, TAKE_PTR(decoded));
 125                         if (r < 0)
 126                                 return r;
 127                 } else
 128                         log_debug("Ignoring invalid loader entry '%s'.", decoded);
 129
 130                 /* We reached the end of the variable */
 131                 if (end)
 132                         break;
 133
 134                 /* Continue after the NUL byte */
 135                 start = i + 1;
 136         }
 137
 138         *ret = TAKE_PTR(l);
 139         return 0;
 140 }
 141
 142 int efi_loader_get_features(uint64_t *ret) {
 143         _cleanup_free_ void *v = NULL;
 144         size_t s;
 145         int r;
 146
 147         assert(ret);
 148
 149         if (!is_efi_boot()) {
 150                 *ret = 0;
 151                 return 0;
 152         }
 153
 154         r = efi_get_variable(EFI_LOADER_VARIABLE(LoaderFeatures), NULL, &v, &s);
 155         if (r == -ENOENT) {
 156                 _cleanup_free_ char *info = NULL;
 157
 158                 /* The new (v240+) LoaderFeatures variable is not supported, let's see if it's systemd-boot at all */
 159                 r = efi_get_variable_string(EFI_LOADER_VARIABLE(LoaderInfo), &info);
 160                 if (r < 0) {
 161                         if (r != -ENOENT)
 162                                 return r;
 163
 164                         /* Variable not set, definitely means not systemd-boot */
 165
 166                 } else if (first_word(info, "systemd-boot")) {
 167
 168                         /* An older systemd-boot version. Let's hardcode the feature set, since it was pretty
 169                          * static in all its versions. */
 170
 171                         *ret = EFI_LOADER_FEATURE_CONFIG_TIMEOUT |
 172                                 EFI_LOADER_FEATURE_ENTRY_DEFAULT |
 173                                 EFI_LOADER_FEATURE_ENTRY_ONESHOT;
 174
 175                         return 0;
 176                 }
 177
 178                 /* No features supported */
 179                 *ret = 0;
 180                 return 0;
 181         }
 182         if (r < 0)
 183                 return r;
 184
 185         if (s != sizeof(uint64_t))
 186                 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
 187                                        "LoaderFeatures EFI variable doesn't have the right size.");
 188
 189         memcpy(ret, v, sizeof(uint64_t));
 190         return 0;
 191 }
 192
 193 int efi_stub_get_features(uint64_t *ret) {
 194         _cleanup_free_ void *v = NULL;
 195         size_t s;
 196         int r;
 197
 198         assert(ret);
 199
 200         if (!is_efi_boot()) {
 201                 *ret = 0;
 202                 return 0;
 203         }
 204
 205         r = efi_get_variable(EFI_LOADER_VARIABLE(StubFeatures), NULL, &v, &s);
 206         if (r == -ENOENT) {
 207                 _cleanup_free_ char *info = NULL;
 208
 209                 /* The new (v252+) StubFeatures variable is not supported, let's see if it's systemd-stub at all */
 210                 r = efi_get_variable_string(EFI_LOADER_VARIABLE(StubInfo), &info);
 211                 if (r < 0) {
 212                         if (r != -ENOENT)
 213                                 return r;
 214
 215                         /* Variable not set, definitely means not systemd-stub */
 216
 217                 } else if (first_word(info, "systemd-stub")) {
 218
 219                         /* An older systemd-stub version. Let's hardcode the feature set, since it was pretty
 220                          * static in all its versions. */
 221
 222                         *ret = EFI_STUB_FEATURE_REPORT_BOOT_PARTITION;
 223                         return 0;
 224                 }
 225
 226                 /* No features supported */
 227                 *ret = 0;
 228                 return 0;
 229         }
 230         if (r < 0)
 231                 return r;
 232
 233         if (s != sizeof(uint64_t))
 234                 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
 235                                        "StubFeatures EFI variable doesn't have the right size.");
 236
 237         memcpy(ret, v, sizeof(uint64_t));
 238         return 0;
 239 }
 240
 241 int efi_stub_measured(void) {
 242         _cleanup_free_ char *pcr_string = NULL;
 243         unsigned pcr_nr;
 244         int r;
 245
 246         /* Checks if we are booted on a kernel with sd-stub which measured the kernel into PCR 11. Or in
 247          * other words, if we are running on a TPM enabled UKI.
 248          *
 249          * Returns == 0 and > 0 depending on the result of the test. Returns -EREMOTE if we detected a stub
 250          * being used, but it measured things into a different PCR than we are configured for in
 251          * userspace. (i.e. we expect PCR 11 being used for this by both sd-stub and us) */
 252
 253         r = getenv_bool_secure("SYSTEMD_FORCE_MEASURE"); /* Give user a chance to override the variable test,
 254                                                           * for debugging purposes */
 255         if (r >= 0)
 256                 return r;
 257         if (r != -ENXIO)
 258                 log_debug_errno(r, "Failed to parse $SYSTEMD_FORCE_MEASURE, ignoring: %m");
 259
 260         if (!is_efi_boot())
 261                 return 0;
 262
 263         r = efi_get_variable_string(EFI_LOADER_VARIABLE(StubPcrKernelImage), &pcr_string);
 264         if (r == -ENOENT)
 265                 return 0;
 266         if (r < 0)
 267                 return r;
 268
 269         r = safe_atou(pcr_string, &pcr_nr);
 270         if (r < 0)
 271                 return log_debug_errno(r, "Failed to parse StubPcrKernelImage EFI variable: %s", pcr_string);
 272         if (pcr_nr != TPM_PCR_INDEX_KERNEL_IMAGE)
 273                 return log_debug_errno(SYNTHETIC_ERRNO(EREMOTE), "Kernel stub measured kernel image into PCR %u, which is different than expected %u.", pcr_nr, TPM_PCR_INDEX_KERNEL_IMAGE);
 274
 275         return 1;
 276 }
 277
 278 int efi_loader_get_config_timeout_one_shot(usec_t *ret) {
 279         _cleanup_free_ char *v = NULL;
 280         static struct stat cache_stat = {};
 281         struct stat new_stat;
 282         static usec_t cache;
 283         uint64_t sec;
 284         int r;
 285
 286         assert(ret);
 287
 288         /* stat() the EFI variable, to see if the mtime changed. If it did, we need to cache again. */
 289         if (stat(EFIVAR_PATH(EFI_LOADER_VARIABLE(LoaderConfigTimeoutOneShot)), &new_stat) < 0)
 290                 return -errno;
 291
 292         if (stat_inode_unmodified(&new_stat, &cache_stat)) {
 293                 *ret = cache;
 294                 return 0;
 295         }
 296
 297         r = efi_get_variable_string(EFI_LOADER_VARIABLE(LoaderConfigTimeoutOneShot), &v);
 298         if (r < 0)
 299                 return r;
 300
 301         r = safe_atou64(v, &sec);
 302         if (r < 0)
 303                 return r;
 304         if (sec > USEC_INFINITY / USEC_PER_SEC)
 305                 return -ERANGE;
 306
 307         cache_stat = new_stat;
 308         *ret = cache = sec * USEC_PER_SEC; /* return in µs */
 309         return 0;
 310 }
 311
 312 int efi_loader_update_entry_one_shot_cache(char **cache, struct stat *cache_stat) {
 313         _cleanup_free_ char *v = NULL;
 314         struct stat new_stat;
 315         int r;
 316
 317         assert(cache);
 318         assert(cache_stat);
 319
 320         /* stat() the EFI variable, to see if the mtime changed. If it did we need to cache again. */
 321         if (stat(EFIVAR_PATH(EFI_LOADER_VARIABLE(LoaderEntryOneShot)), &new_stat) < 0)
 322                 return -errno;
 323
 324         if (stat_inode_unmodified(&new_stat, cache_stat))
 325                 return 0;
 326
 327         r = efi_get_variable_string(EFI_LOADER_VARIABLE(LoaderEntryOneShot), &v);
 328         if (r < 0)
 329                 return r;
 330
 331         if (!efi_loader_entry_name_valid(v))
 332                 return -EINVAL;
 333
 334         *cache_stat = new_stat;
 335         free_and_replace(*cache, v);
 336
 337         return 0;
 338 }
 339
 340 #endif
 341
 342 bool efi_loader_entry_name_valid(const char *s) {
 343         if (!filename_is_valid(s)) /* Make sure entry names fit in filenames */
 344                 return false;
 345
 346         return in_charset(s, ALPHANUMERICAL "+-_.");
 347 }