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1// SPDX-License-Identifier: GPL-2.02/*3 * TPM handling.4 *5 * Copyright (C) 2016 CoreOS, Inc6 * 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_MITIGATION17static 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 the25 * RAM on next reboot before proceeding with boot, ensuring that any secrets26 * are cleared. If userland has ensured that all secrets have been removed27 * from RAM before reboot it can simply reset this variable.28 */29void 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#endif49 50static 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 of74 * 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 algorithms82 * back into a size is contained in the first entry -83 * pass a pointer to the final entry (to calculate its84 * size) and the first entry (so we know how long each85 * 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 the109 * final events structure, and if so how much space they take up110 */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 144err_free:145 efi_bs_call(free_pool, log_tbl);146}147 148void 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