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// SPDX-License-Identifier: GPL-2.0
/*
* TPM handling.
*
* Copyright (C) 2016 CoreOS, Inc
* Copyright (C) 2017 Google, Inc.
* Matthew Garrett <mjg59@google.com>
* Thiebaud Weksteen <tweek@google.com>
*/
#include <linux/efi.h>
#include <linux/tpm_eventlog.h>
#include <asm/efi.h>
#include "efistub.h"
#ifdef CONFIG_RESET_ATTACK_MITIGATION
static const efi_char16_t efi_MemoryOverWriteRequest_name[] =
L"MemoryOverwriteRequestControl";
#define MEMORY_ONLY_RESET_CONTROL_GUID \
EFI_GUID(0xe20939be, 0x32d4, 0x41be, 0xa1, 0x50, 0x89, 0x7f, 0x85, 0xd4, 0x98, 0x29)
#define get_efi_var(name, vendor, ...) \
efi_call_runtime(get_variable, \
(efi_char16_t *)(name), (efi_guid_t *)(vendor), \
__VA_ARGS__)
#define set_efi_var(name, vendor, ...) \
efi_call_runtime(set_variable, \
(efi_char16_t *)(name), (efi_guid_t *)(vendor), \
__VA_ARGS__)
/*
* Enable reboot attack mitigation. This requests that the firmware clear the
* RAM on next reboot before proceeding with boot, ensuring that any secrets
* are cleared. If userland has ensured that all secrets have been removed
* from RAM before reboot it can simply reset this variable.
*/
void efi_enable_reset_attack_mitigation(void)
{
u8 val = 1;
efi_guid_t var_guid = MEMORY_ONLY_RESET_CONTROL_GUID;
efi_status_t status;
unsigned long datasize = 0;
status = get_efi_var(efi_MemoryOverWriteRequest_name, &var_guid,
NULL, &datasize, NULL);
if (status == EFI_NOT_FOUND)
return;
set_efi_var(efi_MemoryOverWriteRequest_name, &var_guid,
EFI_VARIABLE_NON_VOLATILE |
EFI_VARIABLE_BOOTSERVICE_ACCESS |
EFI_VARIABLE_RUNTIME_ACCESS, sizeof(val), &val);
}
#endif
void efi_retrieve_tpm2_eventlog(void)
{
efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;
efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
efi_status_t status;
efi_physical_addr_t log_location = 0, log_last_entry = 0;
struct linux_efi_tpm_eventlog *log_tbl = NULL;
struct efi_tcg2_final_events_table *final_events_table;
unsigned long first_entry_addr, last_entry_addr;
size_t log_size, last_entry_size;
efi_bool_t truncated;
int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2;
efi_tcg2_protocol_t *tcg2_protocol = NULL;
int final_events_size = 0;
status = efi_call_early(locate_protocol, &tcg2_guid, NULL,
(void **)&tcg2_protocol);
if (status != EFI_SUCCESS)
return;
status = efi_call_proto(efi_tcg2_protocol, get_event_log,
tcg2_protocol, version, &log_location,
&log_last_entry, &truncated);
if (status != EFI_SUCCESS || !log_location) {
version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
status = efi_call_proto(efi_tcg2_protocol, get_event_log,
tcg2_protocol, version, &log_location,
&log_last_entry, &truncated);
if (status != EFI_SUCCESS || !log_location)
return;
}
first_entry_addr = (unsigned long) log_location;
/*
* We populate the EFI table even if the logs are empty.
*/
if (!log_last_entry) {
log_size = 0;
} else {
last_entry_addr = (unsigned long) log_last_entry;
/*
* get_event_log only returns the address of the last entry.
* We need to calculate its size to deduce the full size of
* the logs.
*/
if (version == EFI_TCG2_EVENT_LOG_FORMAT_TCG_2) {
/*
* The TCG2 log format has variable length entries,
* and the information to decode the hash algorithms
* back into a size is contained in the first entry -
* pass a pointer to the final entry (to calculate its
* size) and the first entry (so we know how long each
* digest is)
*/
last_entry_size =
__calc_tpm2_event_size((void *)last_entry_addr,
(void *)(long)log_location,
false);
} else {
last_entry_size = sizeof(struct tcpa_event) +
((struct tcpa_event *) last_entry_addr)->event_size;
}
log_size = log_last_entry - log_location + last_entry_size;
}
/* Allocate space for the logs and copy them. */
status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
sizeof(*log_tbl) + log_size,
(void **) &log_tbl);
if (status != EFI_SUCCESS) {
efi_printk("Unable to allocate memory for event log\n");
return;
}
/*
* Figure out whether any events have already been logged to the
* final events structure, and if so how much space they take up
*/
final_events_table = get_efi_config_table(LINUX_EFI_TPM_FINAL_LOG_GUID);
if (final_events_table && final_events_table->nr_events) {
struct tcg_pcr_event2_head *header;
int offset;
void *data;
int event_size;
int i = final_events_table->nr_events;
data = (void *)final_events_table;
offset = sizeof(final_events_table->version) +
sizeof(final_events_table->nr_events);
while (i > 0) {
header = data + offset + final_events_size;
event_size = __calc_tpm2_event_size(header,
(void *)(long)log_location,
false);
final_events_size += event_size;
i--;
}
}
memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
log_tbl->size = log_size;
log_tbl->final_events_preboot_size = final_events_size;
log_tbl->version = version;
memcpy(log_tbl->log, (void *) first_entry_addr, log_size);
status = efi_call_early(install_configuration_table,
&linux_eventlog_guid, log_tbl);
if (status != EFI_SUCCESS)
goto err_free;
return;
err_free:
efi_call_early(free_pool, log_tbl);
}
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