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 static void efi_retrieve_tcg2_eventlog(int version, efi_physical_addr_t log_location, 51 efi_physical_addr_t log_last_entry, 52 efi_bool_t truncated, 53 struct efi_tcg2_final_events_table *final_events_table) 54 { 55 efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID; 56 efi_status_t status; 57 struct linux_efi_tpm_eventlog *log_tbl = NULL; 58 unsigned long first_entry_addr, last_entry_addr; 59 size_t log_size, last_entry_size; 60 int final_events_size = 0; 61 62 first_entry_addr = (unsigned long) log_location; 63 64 /* 65 * We populate the EFI table even if the logs are empty. 66 */ 67 if (!log_last_entry) { 68 log_size = 0; 69 } else { 70 last_entry_addr = (unsigned long) log_last_entry; 71 /* 72 * get_event_log only returns the address of the last entry. 73 * We need to calculate its size to deduce the full size of 74 * the logs. 75 * 76 * CC Event log also uses TCG2 format, handle it same as TPM2. 77 */ 78 if (version > EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2) { 79 /* 80 * The TCG2 log format has variable length entries, 81 * and the information to decode the hash algorithms 82 * back into a size is contained in the first entry - 83 * pass a pointer to the final entry (to calculate its 84 * size) and the first entry (so we know how long each 85 * digest is) 86 */ 87 last_entry_size = 88 __calc_tpm2_event_size((void *)last_entry_addr, 89 (void *)(long)log_location, 90 false); 91 } else { 92 last_entry_size = sizeof(struct tcpa_event) + 93 ((struct tcpa_event *) last_entry_addr)->event_size; 94 } 95 log_size = log_last_entry - log_location + last_entry_size; 96 } 97 98 /* Allocate space for the logs and copy them. */ 99 status = efi_bs_call(allocate_pool, EFI_ACPI_RECLAIM_MEMORY, 100 sizeof(*log_tbl) + log_size, (void **)&log_tbl); 101 102 if (status != EFI_SUCCESS) { 103 efi_err("Unable to allocate memory for event log\n"); 104 return; 105 } 106 107 /* 108 * Figure out whether any events have already been logged to the 109 * final events structure, and if so how much space they take up 110 */ 111 if (final_events_table && final_events_table->nr_events) { 112 struct tcg_pcr_event2_head *header; 113 int offset; 114 void *data; 115 int event_size; 116 int i = final_events_table->nr_events; 117 118 data = (void *)final_events_table; 119 offset = sizeof(final_events_table->version) + 120 sizeof(final_events_table->nr_events); 121 122 while (i > 0) { 123 header = data + offset + final_events_size; 124 event_size = __calc_tpm2_event_size(header, 125 (void *)(long)log_location, 126 false); 127 final_events_size += event_size; 128 i--; 129 } 130 } 131 132 memset(log_tbl, 0, sizeof(*log_tbl) + log_size); 133 log_tbl->size = log_size; 134 log_tbl->final_events_preboot_size = final_events_size; 135 log_tbl->version = version; 136 memcpy(log_tbl->log, (void *) first_entry_addr, log_size); 137 138 status = efi_bs_call(install_configuration_table, 139 &linux_eventlog_guid, log_tbl); 140 if (status != EFI_SUCCESS) 141 goto err_free; 142 return; 143 144 err_free: 145 efi_bs_call(free_pool, log_tbl); 146 } 147 148 void efi_retrieve_eventlog(void) 149 { 150 struct efi_tcg2_final_events_table *final_events_table = NULL; 151 efi_physical_addr_t log_location = 0, log_last_entry = 0; 152 efi_guid_t tpm2_guid = EFI_TCG2_PROTOCOL_GUID; 153 int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2; 154 efi_tcg2_protocol_t *tpm2 = NULL; 155 efi_bool_t truncated; 156 efi_status_t status; 157 158 status = efi_bs_call(locate_protocol, &tpm2_guid, NULL, (void **)&tpm2); 159 if (status == EFI_SUCCESS) { 160 status = efi_call_proto(tpm2, get_event_log, version, &log_location, 161 &log_last_entry, &truncated); 162 163 if (status != EFI_SUCCESS || !log_location) { 164 version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2; 165 status = efi_call_proto(tpm2, get_event_log, version, 166 &log_location, &log_last_entry, 167 &truncated); 168 } else { 169 final_events_table = 170 get_efi_config_table(EFI_TCG2_FINAL_EVENTS_TABLE_GUID); 171 } 172 } else { 173 efi_guid_t cc_guid = EFI_CC_MEASUREMENT_PROTOCOL_GUID; 174 efi_cc_protocol_t *cc = NULL; 175 176 status = efi_bs_call(locate_protocol, &cc_guid, NULL, (void **)&cc); 177 if (status != EFI_SUCCESS) 178 return; 179 180 version = EFI_CC_EVENT_LOG_FORMAT_TCG_2; 181 status = efi_call_proto(cc, get_event_log, version, &log_location, 182 &log_last_entry, &truncated); 183 184 final_events_table = 185 get_efi_config_table(EFI_CC_FINAL_EVENTS_TABLE_GUID); 186 } 187 188 if (status != EFI_SUCCESS || !log_location) 189 return; 190 191 efi_retrieve_tcg2_eventlog(version, log_location, log_last_entry, 192 truncated, final_events_table); 193 } 194