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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-10 20:49:52 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-10 20:49:52 +0000 |
commit | 55944e5e40b1be2afc4855d8d2baf4b73d1876b5 (patch) | |
tree | 33f869f55a1b149e9b7c2b7e201867ca5dd52992 /src/boot/bootctl-random-seed.c | |
parent | Initial commit. (diff) | |
download | systemd-55944e5e40b1be2afc4855d8d2baf4b73d1876b5.tar.xz systemd-55944e5e40b1be2afc4855d8d2baf4b73d1876b5.zip |
Adding upstream version 255.4.upstream/255.4
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | src/boot/bootctl-random-seed.c | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/src/boot/bootctl-random-seed.c b/src/boot/bootctl-random-seed.c new file mode 100644 index 0000000..cfe10c4 --- /dev/null +++ b/src/boot/bootctl-random-seed.c @@ -0,0 +1,239 @@ +/* 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; +} |