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 */
  16 static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
  17 static const efi_char16_t shim_MokSBState_name[] = L"MokSBStateRT";
  18
  19 static 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  */
  28 enum 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 non-volatile attribute set, we might as
  47          * well 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_NON_VOLATILE) && moksbstate == 1)
  57                 return efi_secureboot_mode_disabled;
  58
  59 secure_boot_enabled:
  60         efi_info("UEFI Secure Boot is enabled.\n");
  61         return efi_secureboot_mode_enabled;
  62 }