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
get_var(efi_char16_t * name,efi_guid_t * vendor,u32 * attr,unsigned long * data_size,void * data)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 */
efi_get_secureboot(void)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 }
63