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 * Please keep the logic in sync with 29 * arch/x86/xen/efi.c:xen_efi_get_secureboot(). 30 */ 31 enum efi_secureboot_mode efi_get_secureboot(void) 32 { 33 u32 attr; 34 unsigned long size; 35 enum efi_secureboot_mode mode; 36 efi_status_t status; 37 u8 moksbstate; 38 39 mode = efi_get_secureboot_mode(get_var); 40 if (mode == efi_secureboot_mode_unknown) { 41 efi_err("Could not determine UEFI Secure Boot status.\n"); 42 return efi_secureboot_mode_unknown; 43 } 44 if (mode != efi_secureboot_mode_enabled) 45 return mode; 46 47 /* 48 * See if a user has put the shim into insecure mode. If so, and if the 49 * variable doesn't have the runtime attribute set, we might as well 50 * honor that. 51 */ 52 size = sizeof(moksbstate); 53 status = get_efi_var(shim_MokSBState_name, &shim_guid, 54 &attr, &size, &moksbstate); 55 56 /* If it fails, we don't care why. Default to secure */ 57 if (status != EFI_SUCCESS) 58 goto secure_boot_enabled; 59 if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1) 60 return efi_secureboot_mode_disabled; 61 62 secure_boot_enabled: 63 efi_info("UEFI Secure Boot is enabled.\n"); 64 return efi_secureboot_mode_enabled; 65 } 66