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"MokSBState"; 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 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 59 secure_boot_enabled: 60 efi_info("UEFI Secure Boot is enabled.\n"); 61 return efi_secureboot_mode_enabled; 62 } 63