LXR linux/drivers/firmware/efi/libstub/secureboot.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Secure boot handling.
   4 *
   5 * Copyright (C) 2013,2014 Linaro Limited
   6 *     Roy Franz <roy.franz@linaro.org
   7 * Copyright (C) 2013 Red Hat, Inc.
   8 *     Mark Salter <msalter@redhat.com>
   9 */
  10#include <linux/efi.h>
  11#include <asm/efi.h>
  12
  13#include "efistub.h"
  14
  15/* SHIM variables */
  16static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
  17static const efi_char16_t shim_MokSBState_name[] = L"MokSBState";
  18
  19static efi_status_t get_var(efi_char16_t *name, efi_guid_t *vendor, u32 *attr,
  20                            unsigned long *data_size, void *data)
  21{
  22        return get_efi_var(name, vendor, attr, data_size, data);
  23}
  24
  25/*
  26 * Determine whether we're in secure boot mode.
  27 */
  28enum efi_secureboot_mode efi_get_secureboot(void)
  29{
  30        u32 attr;
  31        unsigned long size;
  32        enum efi_secureboot_mode mode;
  33        efi_status_t status;
  34        u8 moksbstate;
  35
  36        mode = efi_get_secureboot_mode(get_var);
  37        if (mode == efi_secureboot_mode_unknown) {
  38                efi_err("Could not determine UEFI Secure Boot status.\n");
  39                return efi_secureboot_mode_unknown;
  40        }
  41        if (mode != efi_secureboot_mode_enabled)
  42                return mode;
  43
  44        /*
  45         * See if a user has put the shim into insecure mode. If so, and if the
  46         * variable doesn't have the runtime attribute set, we might as well
  47         * honor that.
  48         */
  49        size = sizeof(moksbstate);
  50        status = get_efi_var(shim_MokSBState_name, &shim_guid,
  51                             &attr, &size, &moksbstate);
  52
  53        /* If it fails, we don't care why. Default to secure */
  54        if (status != EFI_SUCCESS)
  55                goto secure_boot_enabled;
  56        if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1)
  57                return efi_secureboot_mode_disabled;
  58
  59secure_boot_enabled:
  60        efi_info("UEFI Secure Boot is enabled.\n");
  61        return efi_secureboot_mode_enabled;
  62}
  63