1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * TPM handling. 4 * 5 * Copyright (C) 2016 CoreOS, Inc 6 * Copyright (C) 2017 Google, Inc. 7 * Matthew Garrett <mjg59@google.com> 8 * Thiebaud Weksteen <tweek@google.com> 9 */ 10 #include <linux/efi.h> 11 #include <linux/tpm_eventlog.h> 12 #include <asm/efi.h> 13 14 #include "efistub.h" 15 16 #ifdef CONFIG_RESET_ATTACK_MITIGATION 17 static const efi_char16_t efi_MemoryOverWriteRequest_name[] = 18 L"MemoryOverwriteRequestControl"; 19 20 #define MEMORY_ONLY_RESET_CONTROL_GUID \ 21 EFI_GUID(0xe20939be, 0x32d4, 0x41be, 0xa1, 0x50, 0x89, 0x7f, 0x85, 0xd4, 0x98, 0x29) 22 23 /* 24 * Enable reboot attack mitigation. This requests that the firmware clear the 25 * RAM on next reboot before proceeding with boot, ensuring that any secrets 26 * are cleared. If userland has ensured that all secrets have been removed 27 * from RAM before reboot it can simply reset this variable. 28 */ 29 void efi_enable_reset_attack_mitigation(void) 30 { 31 u8 val = 1; 32 efi_guid_t var_guid = MEMORY_ONLY_RESET_CONTROL_GUID; 33 efi_status_t status; 34 unsigned long datasize = 0; 35 36 status = get_efi_var(efi_MemoryOverWriteRequest_name, &var_guid, 37 NULL, &datasize, NULL); 38 39 if (status == EFI_NOT_FOUND) 40 return; 41 42 set_efi_var(efi_MemoryOverWriteRequest_name, &var_guid, 43 EFI_VARIABLE_NON_VOLATILE | 44 EFI_VARIABLE_BOOTSERVICE_ACCESS | 45 EFI_VARIABLE_RUNTIME_ACCESS, sizeof(val), &val); 46 } 47 48 #endif 49 50 void efi_retrieve_tpm2_eventlog(void) 51 { 52 efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID; 53 efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID; 54 efi_status_t status; 55 efi_physical_addr_t log_location = 0, log_last_entry = 0; 56 struct linux_efi_tpm_eventlog *log_tbl = NULL; 57 struct efi_tcg2_final_events_table *final_events_table = NULL; 58 unsigned long first_entry_addr, last_entry_addr; 59 size_t log_size, last_entry_size; 60 efi_bool_t truncated; 61 int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2; 62 efi_tcg2_protocol_t *tcg2_protocol = NULL; 63 int final_events_size = 0; 64 65 status = efi_bs_call(locate_protocol, &tcg2_guid, NULL, 66 (void **)&tcg2_protocol); 67 if (status != EFI_SUCCESS) 68 return; 69 70 status = efi_call_proto(tcg2_protocol, get_event_log, version, 71 &log_location, &log_last_entry, &truncated); 72 73 if (status != EFI_SUCCESS || !log_location) { 74 version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2; 75 status = efi_call_proto(tcg2_protocol, get_event_log, version, 76 &log_location, &log_last_entry, 77 &truncated); 78 if (status != EFI_SUCCESS || !log_location) 79 return; 80 81 } 82 83 first_entry_addr = (unsigned long) log_location; 84 85 /* 86 * We populate the EFI table even if the logs are empty. 87 */ 88 if (!log_last_entry) { 89 log_size = 0; 90 } else { 91 last_entry_addr = (unsigned long) log_last_entry; 92 /* 93 * get_event_log only returns the address of the last entry. 94 * We need to calculate its size to deduce the full size of 95 * the logs. 96 */ 97 if (version == EFI_TCG2_EVENT_LOG_FORMAT_TCG_2) { 98 /* 99 * The TCG2 log format has variable length entries, 100 * and the information to decode the hash algorithms 101 * back into a size is contained in the first entry - 102 * pass a pointer to the final entry (to calculate its 103 * size) and the first entry (so we know how long each 104 * digest is) 105 */ 106 last_entry_size = 107 __calc_tpm2_event_size((void *)last_entry_addr, 108 (void *)(long)log_location, 109 false); 110 } else { 111 last_entry_size = sizeof(struct tcpa_event) + 112 ((struct tcpa_event *) last_entry_addr)->event_size; 113 } 114 log_size = log_last_entry - log_location + last_entry_size; 115 } 116 117 /* Allocate space for the logs and copy them. */ 118 status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, 119 sizeof(*log_tbl) + log_size, (void **)&log_tbl); 120 121 if (status != EFI_SUCCESS) { 122 efi_printk("Unable to allocate memory for event log\n"); 123 return; 124 } 125 126 /* 127 * Figure out whether any events have already been logged to the 128 * final events structure, and if so how much space they take up 129 */ 130 if (version == EFI_TCG2_EVENT_LOG_FORMAT_TCG_2) 131 final_events_table = get_efi_config_table(LINUX_EFI_TPM_FINAL_LOG_GUID); 132 if (final_events_table && final_events_table->nr_events) { 133 struct tcg_pcr_event2_head *header; 134 int offset; 135 void *data; 136 int event_size; 137 int i = final_events_table->nr_events; 138 139 data = (void *)final_events_table; 140 offset = sizeof(final_events_table->version) + 141 sizeof(final_events_table->nr_events); 142 143 while (i > 0) { 144 header = data + offset + final_events_size; 145 event_size = __calc_tpm2_event_size(header, 146 (void *)(long)log_location, 147 false); 148 final_events_size += event_size; 149 i--; 150 } 151 } 152 153 memset(log_tbl, 0, sizeof(*log_tbl) + log_size); 154 log_tbl->size = log_size; 155 log_tbl->final_events_preboot_size = final_events_size; 156 log_tbl->version = version; 157 memcpy(log_tbl->log, (void *) first_entry_addr, log_size); 158 159 status = efi_bs_call(install_configuration_table, 160 &linux_eventlog_guid, log_tbl); 161 if (status != EFI_SUCCESS) 162 goto err_free; 163 return; 164 165 err_free: 166 efi_bs_call(free_pool, log_tbl); 167 } 168