286 lines
7.4 KiB
C
286 lines
7.4 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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#include <errno.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <linux/fs.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "sd-id128.h"
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#include "alloc-util.h"
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#include "chattr-util.h"
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#include "efivars.h"
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#include "fd-util.h"
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#include "io-util.h"
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#include "macro.h"
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#include "stdio-util.h"
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#include "strv.h"
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#include "time-util.h"
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#include "utf8.h"
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#include "virt.h"
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#if ENABLE_EFI
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char* efi_variable_path(sd_id128_t vendor, const char *name) {
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char *p;
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if (asprintf(&p,
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"/sys/firmware/efi/efivars/%s-" SD_ID128_UUID_FORMAT_STR,
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name, SD_ID128_FORMAT_VAL(vendor)) < 0)
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return NULL;
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return p;
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}
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int efi_get_variable(
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sd_id128_t vendor,
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const char *name,
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uint32_t *ret_attribute,
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void **ret_value,
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size_t *ret_size) {
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_cleanup_close_ int fd = -1;
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_cleanup_free_ char *p = NULL;
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_cleanup_free_ void *buf = NULL;
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struct stat st;
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uint32_t a;
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ssize_t n;
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assert(name);
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p = efi_variable_path(vendor, name);
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if (!p)
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return -ENOMEM;
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if (!ret_value && !ret_size && !ret_attribute) {
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/* If caller is not interested in anything, just check if the variable exists and is readable
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* to us. */
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if (access(p, R_OK) < 0)
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return -errno;
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return 0;
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}
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fd = open(p, O_RDONLY|O_NOCTTY|O_CLOEXEC);
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if (fd < 0)
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return -errno;
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if (fstat(fd, &st) < 0)
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return -errno;
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if (st.st_size < 4)
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return -ENODATA;
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if (st.st_size > 4*1024*1024 + 4)
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return -E2BIG;
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if (ret_value || ret_attribute) {
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n = read(fd, &a, sizeof(a));
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if (n < 0)
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return -errno;
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if (n != sizeof(a))
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return -EIO;
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}
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if (ret_value) {
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buf = malloc(st.st_size - 4 + 2);
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if (!buf)
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return -ENOMEM;
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n = read(fd, buf, (size_t) st.st_size - 4);
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if (n < 0)
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return -errno;
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assert(n <= st.st_size - 4);
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/* Always NUL terminate (2 bytes, to protect UTF-16) */
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((char*) buf)[n] = 0;
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((char*) buf)[n + 1] = 0;
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} else
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/* Assume that the reported size is accurate */
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n = st.st_size - 4;
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/* Note that efivarfs interestingly doesn't require ftruncate() to update an existing EFI variable
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* with a smaller value. */
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if (ret_attribute)
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*ret_attribute = a;
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if (ret_value)
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*ret_value = TAKE_PTR(buf);
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if (ret_size)
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*ret_size = n;
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return 0;
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}
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int efi_get_variable_string(sd_id128_t vendor, const char *name, char **p) {
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_cleanup_free_ void *s = NULL;
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size_t ss = 0;
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int r;
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char *x;
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r = efi_get_variable(vendor, name, NULL, &s, &ss);
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if (r < 0)
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return r;
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x = utf16_to_utf8(s, ss);
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if (!x)
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return -ENOMEM;
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*p = x;
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return 0;
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}
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int efi_set_variable(
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sd_id128_t vendor,
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const char *name,
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const void *value,
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size_t size) {
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struct var {
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uint32_t attr;
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char buf[];
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} _packed_ * _cleanup_free_ buf = NULL;
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_cleanup_free_ char *p = NULL;
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_cleanup_close_ int fd = -1;
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bool saved_flags_valid = false;
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unsigned saved_flags;
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int r;
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assert(name);
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assert(value || size == 0);
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p = efi_variable_path(vendor, name);
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if (!p)
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return -ENOMEM;
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/* Newer efivarfs protects variables that are not in a whitelist with FS_IMMUTABLE_FL by default, to protect
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* them for accidental removal and modification. We are not changing these variables accidentally however,
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* hence let's unset the bit first. */
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r = chattr_path(p, 0, FS_IMMUTABLE_FL, &saved_flags);
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if (r < 0 && r != -ENOENT)
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log_debug_errno(r, "Failed to drop FS_IMMUTABLE_FL flag from '%s', ignoring: %m", p);
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saved_flags_valid = r >= 0;
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if (size == 0) {
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if (unlink(p) < 0) {
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r = -errno;
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goto finish;
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}
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return 0;
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}
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fd = open(p, O_WRONLY|O_CREAT|O_NOCTTY|O_CLOEXEC, 0644);
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if (fd < 0) {
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r = -errno;
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goto finish;
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}
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buf = malloc(sizeof(uint32_t) + size);
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if (!buf) {
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r = -ENOMEM;
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goto finish;
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}
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buf->attr = EFI_VARIABLE_NON_VOLATILE|EFI_VARIABLE_BOOTSERVICE_ACCESS|EFI_VARIABLE_RUNTIME_ACCESS;
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memcpy(buf->buf, value, size);
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r = loop_write(fd, buf, sizeof(uint32_t) + size, false);
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if (r < 0)
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goto finish;
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r = 0;
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finish:
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if (saved_flags_valid) {
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int q;
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/* Restore the original flags field, just in case */
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if (fd < 0)
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q = chattr_path(p, saved_flags, FS_IMMUTABLE_FL, NULL);
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else
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q = chattr_fd(fd, saved_flags, FS_IMMUTABLE_FL, NULL);
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if (q < 0)
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log_debug_errno(q, "Failed to restore FS_IMMUTABLE_FL on '%s', ignoring: %m", p);
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}
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return r;
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}
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int efi_set_variable_string(sd_id128_t vendor, const char *name, const char *v) {
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_cleanup_free_ char16_t *u16 = NULL;
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u16 = utf8_to_utf16(v, strlen(v));
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if (!u16)
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return -ENOMEM;
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return efi_set_variable(vendor, name, u16, (char16_strlen(u16) + 1) * sizeof(char16_t));
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}
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bool is_efi_boot(void) {
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if (detect_container() > 0)
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return false;
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return access("/sys/firmware/efi/", F_OK) >= 0;
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}
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static int read_flag(const char *varname) {
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_cleanup_free_ void *v = NULL;
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uint8_t b;
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size_t s;
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int r;
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if (!is_efi_boot()) /* If this is not an EFI boot, assume the queried flags are zero */
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return 0;
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r = efi_get_variable(EFI_VENDOR_GLOBAL, varname, NULL, &v, &s);
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if (r < 0)
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return r;
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if (s != 1)
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return -EINVAL;
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b = *(uint8_t *)v;
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return !!b;
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}
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bool is_efi_secure_boot(void) {
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return read_flag("SecureBoot") > 0;
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}
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bool is_efi_secure_boot_setup_mode(void) {
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return read_flag("SetupMode") > 0;
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}
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int systemd_efi_options_variable(char **line) {
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const char *e;
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int r;
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assert(line);
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/* For testing purposes it is sometimes useful to be able to override this */
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e = secure_getenv("SYSTEMD_EFI_OPTIONS");
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if (e) {
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char *m;
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m = strdup(e);
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if (!m)
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return -ENOMEM;
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*line = m;
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return 0;
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}
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r = efi_get_variable_string(EFI_VENDOR_SYSTEMD, "SystemdOptions", line);
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if (r == -ENOENT)
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return -ENODATA;
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return r;
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}
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#endif
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