1 /*
2 * Secure boot handling.
3 *
4 * Copyright (C) 2013,2014 Linaro Limited
5 * Roy Franz <roy.franz@linaro.org
6 * Copyright (C) 2013 Red Hat, Inc.
7 * Mark Salter <msalter@redhat.com>
8 *
9 * This file is part of the Linux kernel, and is made available under the
10 * terms of the GNU General Public License version 2.
11 */
12 #include <linux/efi.h>
13 #include <asm/efi.h>
14
15 #include "efistub.h"
16
17 /* BIOS variables */
18 static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
19 static const efi_char16_t efi_SecureBoot_name[] = L"SecureBoot";
20 static const efi_char16_t efi_SetupMode_name[] = L"SetupMode";
21
22 /* SHIM variables */
23 static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
24 static const efi_char16_t shim_MokSBState_name[] = L"MokSBState";
25
26 #define get_efi_var(name, vendor, ...) \
27 efi_call_runtime(get_variable, \
28 (efi_char16_t *)(name), (efi_guid_t *)(vendor), \
29 __VA_ARGS__);
30
31 /*
32 * Determine whether we're in secure boot mode.
33 *
34 * Please keep the logic in sync with
35 * arch/x86/xen/efi.c:xen_efi_get_secureboot().
36 */
efi_get_secureboot(efi_system_table_t * sys_table_arg)37 enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg)
38 {
39 u32 attr;
40 u8 secboot, setupmode, moksbstate;
41 unsigned long size;
42 efi_status_t status;
43
44 size = sizeof(secboot);
45 status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid,
46 NULL, &size, &secboot);
47 if (status == EFI_NOT_FOUND)
48 return efi_secureboot_mode_disabled;
49 if (status != EFI_SUCCESS)
50 goto out_efi_err;
51
52 size = sizeof(setupmode);
53 status = get_efi_var(efi_SetupMode_name, &efi_variable_guid,
54 NULL, &size, &setupmode);
55 if (status != EFI_SUCCESS)
56 goto out_efi_err;
57
58 if (secboot == 0 || setupmode == 1)
59 return efi_secureboot_mode_disabled;
60
61 /*
62 * See if a user has put the shim into insecure mode. If so, and if the
63 * variable doesn't have the runtime attribute set, we might as well
64 * honor that.
65 */
66 size = sizeof(moksbstate);
67 status = get_efi_var(shim_MokSBState_name, &shim_guid,
68 &attr, &size, &moksbstate);
69
70 /* If it fails, we don't care why. Default to secure */
71 if (status != EFI_SUCCESS)
72 goto secure_boot_enabled;
73 if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1)
74 return efi_secureboot_mode_disabled;
75
76 secure_boot_enabled:
77 pr_efi(sys_table_arg, "UEFI Secure Boot is enabled.\n");
78 return efi_secureboot_mode_enabled;
79
80 out_efi_err:
81 pr_efi_err(sys_table_arg, "Could not determine UEFI Secure Boot status.\n");
82 return efi_secureboot_mode_unknown;
83 }
84
