From 85f875357b144b7a6c6eba3556db828a6f10a436 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Fri, 16 Dec 2022 18:42:39 +0100 Subject: bootctl: split out random seed verb, too --- src/boot/bootctl-random-seed.c | 151 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 151 insertions(+) create mode 100644 src/boot/bootctl-random-seed.c (limited to 'src/boot/bootctl-random-seed.c') diff --git a/src/boot/bootctl-random-seed.c b/src/boot/bootctl-random-seed.c new file mode 100644 index 0000000000..0b3ff74eaa --- /dev/null +++ b/src/boot/bootctl-random-seed.c @@ -0,0 +1,151 @@ +/* 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 "mkdir.h" +#include "path-util.h" +#include "random-util.h" +#include "tmpfile-util.h" +#include "umask-util.h" + +int install_random_seed(const char *esp) { + _cleanup_(unlink_and_freep) char *tmp = NULL; + uint8_t buffer[RANDOM_EFI_SEED_SIZE]; + _cleanup_free_ char *path = NULL; + _cleanup_close_ int fd = -1; + size_t token_size; + ssize_t n; + int r; + + assert(esp); + + path = path_join(esp, "/loader/random-seed"); + if (!path) + return log_oom(); + + r = crypto_random_bytes(buffer, sizeof(buffer)); + if (r < 0) + return log_error_errno(r, "Failed to acquire random seed: %m"); + + /* Normally create_subdirs() should already have created everything we need, but in case "bootctl + * random-seed" is called we want to just create the minimum we need for it, and not the full + * list. */ + r = mkdir_parents(path, 0755); + if (r < 0) + return log_error_errno(r, "Failed to create parent directory for %s: %m", path); + + r = tempfn_random(path, "bootctl", &tmp); + if (r < 0) + return log_oom(); + + fd = open(tmp, O_CREAT|O_EXCL|O_NOFOLLOW|O_NOCTTY|O_WRONLY|O_CLOEXEC, 0600); + if (fd < 0) { + tmp = mfree(tmp); + return log_error_errno(fd, "Failed to open random seed file for writing: %m"); + } + + n = write(fd, buffer, sizeof(buffer)); + if (n < 0) + return log_error_errno(errno, "Failed to write random seed file: %m"); + if ((size_t) n != sizeof(buffer)) + return log_error_errno(SYNTHETIC_ERRNO(EIO), "Short write while writing random seed file."); + + if (rename(tmp, path) < 0) + return log_error_errno(r, "Failed to move random seed file into place: %m"); + + tmp = mfree(tmp); + + log_info("Random seed file %s successfully written (%zu bytes).", path, sizeof(buffer)); + + 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_warning_errno(r, "Unable to write 'LoaderSystemToken' EFI variable (firmware problem?), ignoring: %m"); + else + log_warning_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 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; + + (void) sync_everything(); + return 0; +} -- cgit v1.2.1