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 /* BIOS variables */ 16 static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID; 17 static const efi_char16_t const efi_SecureBoot_name[] = { 18 'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0 19 }; 20 static const efi_char16_t const efi_SetupMode_name[] = { 21 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0 22 }; 23 24 /* SHIM variables */ 25 static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID; 26 static efi_char16_t const shim_MokSBState_name[] = { 27 'M', 'o', 'k', 'S', 'B', 'S', 't', 'a', 't', 'e', 0 28 }; 29 30 #define get_efi_var(name, vendor, ...) \ 31 efi_call_runtime(get_variable, \ 32 (efi_char16_t *)(name), (efi_guid_t *)(vendor), \ 33 __VA_ARGS__); 34 35 /* 36 * Determine whether we're in secure boot mode. 37 */ 38 enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg) 39 { 40 u32 attr; 41 u8 secboot, setupmode, moksbstate; 42 unsigned long size; 43 efi_status_t status; 44 45 size = sizeof(secboot); 46 status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid, 47 NULL, &size, &secboot); 48 if (status == EFI_NOT_FOUND) 49 return efi_secureboot_mode_disabled; 50 if (status != EFI_SUCCESS) 51 goto out_efi_err; 52 53 size = sizeof(setupmode); 54 status = get_efi_var(efi_SetupMode_name, &efi_variable_guid, 55 NULL, &size, &setupmode); 56 if (status != EFI_SUCCESS) 57 goto out_efi_err; 58 59 if (secboot == 0 || setupmode == 1) 60 return efi_secureboot_mode_disabled; 61 62 /* 63 * See if a user has put the shim into insecure mode. If so, and if the 64 * variable doesn't have the runtime attribute set, we might as well 65 * honor that. 66 */ 67 size = sizeof(moksbstate); 68 status = get_efi_var(shim_MokSBState_name, &shim_guid, 69 &attr, &size, &moksbstate); 70 71 /* If it fails, we don't care why. Default to secure */ 72 if (status != EFI_SUCCESS) 73 goto secure_boot_enabled; 74 if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1) 75 return efi_secureboot_mode_disabled; 76 77 secure_boot_enabled: 78 pr_efi(sys_table_arg, "UEFI Secure Boot is enabled.\n"); 79 return efi_secureboot_mode_enabled; 80 81 out_efi_err: 82 pr_efi_err(sys_table_arg, "Could not determine UEFI Secure Boot status.\n"); 83 return efi_secureboot_mode_unknown; 84 } 85