LXR linux/drivers/firmware/efi/libstub/tpm.c

   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}
 168