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
  17 static 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 #define get_efi_var(name, vendor, ...) \
  24         efi_call_runtime(get_variable, \
  25                          (efi_char16_t *)(name), (efi_guid_t *)(vendor), \
  26                          __VA_ARGS__)
  27
  28 #define set_efi_var(name, vendor, ...) \
  29         efi_call_runtime(set_variable, \
  30                          (efi_char16_t *)(name), (efi_guid_t *)(vendor), \
  31                          __VA_ARGS__)
  32
  33 /*
  34  * Enable reboot attack mitigation. This requests that the firmware clear the
  35  * RAM on next reboot before proceeding with boot, ensuring that any secrets
  36  * are cleared. If userland has ensured that all secrets have been removed
  37  * from RAM before reboot it can simply reset this variable.
  38  */
  39 void efi_enable_reset_attack_mitigation(efi_system_table_t *sys_table_arg)
  40 {
  41         u8 val = 1;
  42         efi_guid_t var_guid = MEMORY_ONLY_RESET_CONTROL_GUID;
  43         efi_status_t status;
  44         unsigned long datasize = 0;
  45
  46         status = get_efi_var(efi_MemoryOverWriteRequest_name, &var_guid,
  47                              NULL, &datasize, NULL);
  48
  49         if (status == EFI_NOT_FOUND)
  50                 return;
  51
  52         set_efi_var(efi_MemoryOverWriteRequest_name, &var_guid,
  53                     EFI_VARIABLE_NON_VOLATILE |
  54                     EFI_VARIABLE_BOOTSERVICE_ACCESS |
  55                     EFI_VARIABLE_RUNTIME_ACCESS, sizeof(val), &val);
  56 }
  57
  58 #endif
  59
  60 static void efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
  61 {
  62         efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;
  63         efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
  64         efi_status_t status;
  65         efi_physical_addr_t log_location = 0, log_last_entry = 0;
  66         struct linux_efi_tpm_eventlog *log_tbl = NULL;
  67         unsigned long first_entry_addr, last_entry_addr;
  68         size_t log_size, last_entry_size;
  69         efi_bool_t truncated;
  70         void *tcg2_protocol = NULL;
  71
  72         status = efi_call_early(locate_protocol, &tcg2_guid, NULL,
  73                                 &tcg2_protocol);
  74         if (status != EFI_SUCCESS)
  75                 return;
  76
  77         status = efi_call_proto(efi_tcg2_protocol, get_event_log, tcg2_protocol,
  78                                 EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2,
  79                                 &log_location, &log_last_entry, &truncated);
  80         if (status != EFI_SUCCESS)
  81                 return;
  82
  83         if (!log_location)
  84                 return;
  85         first_entry_addr = (unsigned long) log_location;
  86
  87         /*
  88          * We populate the EFI table even if the logs are empty.
  89          */
  90         if (!log_last_entry) {
  91                 log_size = 0;
  92         } else {
  93                 last_entry_addr = (unsigned long) log_last_entry;
  94                 /*
  95                  * get_event_log only returns the address of the last entry.
  96                  * We need to calculate its size to deduce the full size of
  97                  * the logs.
  98                  */
  99                 last_entry_size = sizeof(struct tcpa_event) +
 100                         ((struct tcpa_event *) last_entry_addr)->event_size;
 101                 log_size = log_last_entry - log_location + last_entry_size;
 102         }
 103
 104         /* Allocate space for the logs and copy them. */
 105         status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
 106                                 sizeof(*log_tbl) + log_size,
 107                                 (void **) &log_tbl);
 108
 109         if (status != EFI_SUCCESS) {
 110                 efi_printk(sys_table_arg,
 111                            "Unable to allocate memory for event log\n");
 112                 return;
 113         }
 114
 115         memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
 116         log_tbl->size = log_size;
 117         log_tbl->version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
 118         memcpy(log_tbl->log, (void *) first_entry_addr, log_size);
 119
 120         status = efi_call_early(install_configuration_table,
 121                                 &linux_eventlog_guid, log_tbl);
 122         if (status != EFI_SUCCESS)
 123                 goto err_free;
 124         return;
 125
 126 err_free:
 127         efi_call_early(free_pool, log_tbl);
 128 }
 129
 130 void efi_retrieve_tpm2_eventlog(efi_system_table_t *sys_table_arg)
 131 {
 132         /* Only try to retrieve the logs in 1.2 format. */
 133         efi_retrieve_tpm2_eventlog_1_2(sys_table_arg);
 134 }