/* 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 "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 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; 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); 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; /* 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"); r = loop_write(fd, buffer, sizeof(buffer), /* do_poll= */ false); 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; }