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 */ 16 static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID; 17 static const efi_char16_t efi_SecureBoot_name[] = L"SecureBoot"; 18 static const efi_char16_t efi_SetupMode_name[] = L"SetupMode"; 19 20 /* SHIM variables */ 21 static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID; 22 static 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 */ 30 enum 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 69 secure_boot_enabled: 70 efi_info("UEFI Secure Boot is enabled.\n"); 71 return efi_secureboot_mode_enabled; 72 73 out_efi_err: 74 efi_err("Could not determine UEFI Secure Boot status.\n"); 75 return efi_secureboot_mode_unknown; 76 } 77