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

   1/*
   2 * TPM handling.
   3 *
   4 * Copyright (C) 2016 CoreOS, Inc
   5 * Copyright (C) 2017 Google, Inc.
   6 *     Matthew Garrett <mjg59@google.com>
   7 *     Thiebaud Weksteen <tweek@google.com>
   8 *
   9 * This file is part of the Linux kernel, and is made available under the
  10 * terms of the GNU General Public License version 2.
  11 */
  12#include <linux/efi.h>
  13#include <linux/tpm_eventlog.h>
  14#include <asm/efi.h>
  15
  16#include "efistub.h"
  17
  18#ifdef CONFIG_RESET_ATTACK_MITIGATION
  19static const efi_char16_t efi_MemoryOverWriteRequest_name[] =
  20        L"MemoryOverwriteRequestControl";
  21
  22#define MEMORY_ONLY_RESET_CONTROL_GUID \
  23        EFI_GUID(0xe20939be, 0x32d4, 0x41be, 0xa1, 0x50, 0x89, 0x7f, 0x85, 0xd4, 0x98, 0x29)
  24
  25#define get_efi_var(name, vendor, ...) \
  26        efi_call_runtime(get_variable, \
  27                         (efi_char16_t *)(name), (efi_guid_t *)(vendor), \
  28                         __VA_ARGS__)
  29
  30#define set_efi_var(name, vendor, ...) \
  31        efi_call_runtime(set_variable, \
  32                         (efi_char16_t *)(name), (efi_guid_t *)(vendor), \
  33                         __VA_ARGS__)
  34
  35/*
  36 * Enable reboot attack mitigation. This requests that the firmware clear the
  37 * RAM on next reboot before proceeding with boot, ensuring that any secrets
  38 * are cleared. If userland has ensured that all secrets have been removed
  39 * from RAM before reboot it can simply reset this variable.
  40 */
  41void efi_enable_reset_attack_mitigation(efi_system_table_t *sys_table_arg)
  42{
  43        u8 val = 1;
  44        efi_guid_t var_guid = MEMORY_ONLY_RESET_CONTROL_GUID;
  45        efi_status_t status;
  46        unsigned long datasize = 0;
  47
  48        status = get_efi_var(efi_MemoryOverWriteRequest_name, &var_guid,
  49                             NULL, &datasize, NULL);
  50
  51        if (status == EFI_NOT_FOUND)
  52                return;
  53
  54        set_efi_var(efi_MemoryOverWriteRequest_name, &var_guid,
  55                    EFI_VARIABLE_NON_VOLATILE |
  56                    EFI_VARIABLE_BOOTSERVICE_ACCESS |
  57                    EFI_VARIABLE_RUNTIME_ACCESS, sizeof(val), &val);
  58}
  59
  60#endif
  61
  62static void efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
  63{
  64        efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;
  65        efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
  66        efi_status_t status;
  67        efi_physical_addr_t log_location = 0, log_last_entry = 0;
  68        struct linux_efi_tpm_eventlog *log_tbl = NULL;
  69        unsigned long first_entry_addr, last_entry_addr;
  70        size_t log_size, last_entry_size;
  71        efi_bool_t truncated;
  72        void *tcg2_protocol = NULL;
  73
  74        status = efi_call_early(locate_protocol, &tcg2_guid, NULL,
  75                                &tcg2_protocol);
  76        if (status != EFI_SUCCESS)
  77                return;
  78
  79        status = efi_call_proto(efi_tcg2_protocol, get_event_log, tcg2_protocol,
  80                                EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2,
  81                                &log_location, &log_last_entry, &truncated);
  82        if (status != EFI_SUCCESS)
  83                return;
  84
  85        if (!log_location)
  86                return;
  87        first_entry_addr = (unsigned long) log_location;
  88
  89        /*
  90         * We populate the EFI table even if the logs are empty.
  91         */
  92        if (!log_last_entry) {
  93                log_size = 0;
  94        } else {
  95                last_entry_addr = (unsigned long) log_last_entry;
  96                /*
  97                 * get_event_log only returns the address of the last entry.
  98                 * We need to calculate its size to deduce the full size of
  99                 * the logs.
 100                 */
 101                last_entry_size = sizeof(struct tcpa_event) +
 102                        ((struct tcpa_event *) last_entry_addr)->event_size;
 103                log_size = log_last_entry - log_location + last_entry_size;
 104        }
 105
 106        /* Allocate space for the logs and copy them. */
 107        status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
 108                                sizeof(*log_tbl) + log_size,
 109                                (void **) &log_tbl);
 110
 111        if (status != EFI_SUCCESS) {
 112                efi_printk(sys_table_arg,
 113                           "Unable to allocate memory for event log\n");
 114                return;
 115        }
 116
 117        memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
 118        log_tbl->size = log_size;
 119        log_tbl->version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
 120        memcpy(log_tbl->log, (void *) first_entry_addr, log_size);
 121
 122        status = efi_call_early(install_configuration_table,
 123                                &linux_eventlog_guid, log_tbl);
 124        if (status != EFI_SUCCESS)
 125                goto err_free;
 126        return;
 127
 128err_free:
 129        efi_call_early(free_pool, log_tbl);
 130}
 131
 132void efi_retrieve_tpm2_eventlog(efi_system_table_t *sys_table_arg)
 133{
 134        /* Only try to retrieve the logs in 1.2 format. */
 135        efi_retrieve_tpm2_eventlog_1_2(sys_table_arg);
 136}
 137