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/* BIOS variables */
16static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
17static const efi_char16_t efi_SecureBoot_name[] = L"SecureBoot";
18static const efi_char16_t efi_SetupMode_name[] = L"SetupMode";
19
20/* SHIM variables */
21static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
22static const efi_char16_t shim_MokSBState_name[] = L"MokSBState";
23
24/*
25 * Determine whether we're in secure boot mode.
26 *
27 * Please keep the logic in sync with
28 * arch/x86/xen/efi.c:xen_efi_get_secureboot().
29 */
30enum efi_secureboot_mode efi_get_secureboot(void)
31{
32	u32 attr;
33	u8 secboot, setupmode, moksbstate;
34	unsigned long size;
35	efi_status_t status;
36
37	size = sizeof(secboot);
38	status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid,
39			     NULL, &size, &secboot);
40	if (status == EFI_NOT_FOUND)
41		return efi_secureboot_mode_disabled;
42	if (status != EFI_SUCCESS)
43		goto out_efi_err;
44
45	size = sizeof(setupmode);
46	status = get_efi_var(efi_SetupMode_name, &efi_variable_guid,
47			     NULL, &size, &setupmode);
48	if (status != EFI_SUCCESS)
49		goto out_efi_err;
50
51	if (secboot == 0 || setupmode == 1)
52		return efi_secureboot_mode_disabled;
53
54	/*
55	 * See if a user has put the shim into insecure mode. If so, and if the
56	 * variable doesn't have the runtime attribute set, we might as well
57	 * honor that.
58	 */
59	size = sizeof(moksbstate);
60	status = get_efi_var(shim_MokSBState_name, &shim_guid,
61			     &attr, &size, &moksbstate);
62
63	/* If it fails, we don't care why. Default to secure */
64	if (status != EFI_SUCCESS)
65		goto secure_boot_enabled;
66	if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1)
67		return efi_secureboot_mode_disabled;
68
69secure_boot_enabled:
70	efi_info("UEFI Secure Boot is enabled.\n");
71	return efi_secureboot_mode_enabled;
72
73out_efi_err:
74	efi_err("Could not determine UEFI Secure Boot status.\n");
75	return efi_secureboot_mode_unknown;
76}