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