cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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tpm.c (5009B)

      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
     17static 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 */
     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#endif
     49
     50void 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_err("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
    165err_free:
    166	efi_bs_call(free_pool, log_tbl);
    167}