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 #define get_efi_var(name, vendor, ...) \ 25 efi_call_runtime(get_variable, \ 26 (efi_char16_t *)(name), (efi_guid_t *)(vendor), \ 27 __VA_ARGS__); 28 29 /* 30 * Determine whether we're in secure boot mode. 31 * 32 * Please keep the logic in sync with 33 * arch/x86/xen/efi.c:xen_efi_get_secureboot(). 34 */ 35 enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg) 36 { 37 u32 attr; 38 u8 secboot, setupmode, moksbstate; 39 unsigned long size; 40 efi_status_t status; 41 42 size = sizeof(secboot); 43 status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid, 44 NULL, &size, &secboot); 45 if (status == EFI_NOT_FOUND) 46 return efi_secureboot_mode_disabled; 47 if (status != EFI_SUCCESS) 48 goto out_efi_err; 49 50 size = sizeof(setupmode); 51 status = get_efi_var(efi_SetupMode_name, &efi_variable_guid, 52 NULL, &size, &setupmode); 53 if (status != EFI_SUCCESS) 54 goto out_efi_err; 55 56 if (secboot == 0 || setupmode == 1) 57 return efi_secureboot_mode_disabled; 58 59 /* 60 * See if a user has put the shim into insecure mode. If so, and if the 61 * variable doesn't have the runtime attribute set, we might as well 62 * honor that. 63 */ 64 size = sizeof(moksbstate); 65 status = get_efi_var(shim_MokSBState_name, &shim_guid, 66 &attr, &size, &moksbstate); 67 68 /* If it fails, we don't care why. Default to secure */ 69 if (status != EFI_SUCCESS) 70 goto secure_boot_enabled; 71 if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1) 72 return efi_secureboot_mode_disabled; 73 74 secure_boot_enabled: 75 pr_efi(sys_table_arg, "UEFI Secure Boot is enabled.\n"); 76 return efi_secureboot_mode_enabled; 77 78 out_efi_err: 79 pr_efi_err(sys_table_arg, "Could not determine UEFI Secure Boot status.\n"); 80 return efi_secureboot_mode_unknown; 81 } 82