Loading...
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
50static void efi_retrieve_tcg2_eventlog(int version, efi_physical_addr_t log_location,
51 efi_physical_addr_t log_last_entry,
52 efi_bool_t truncated,
53 struct efi_tcg2_final_events_table *final_events_table)
54{
55 efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
56 efi_status_t status;
57 struct linux_efi_tpm_eventlog *log_tbl = NULL;
58 unsigned long first_entry_addr, last_entry_addr;
59 size_t log_size, last_entry_size;
60 int final_events_size = 0;
61
62 first_entry_addr = (unsigned long) log_location;
63
64 /*
65 * We populate the EFI table even if the logs are empty.
66 */
67 if (!log_last_entry) {
68 log_size = 0;
69 } else {
70 last_entry_addr = (unsigned long) log_last_entry;
71 /*
72 * get_event_log only returns the address of the last entry.
73 * We need to calculate its size to deduce the full size of
74 * the logs.
75 *
76 * CC Event log also uses TCG2 format, handle it same as TPM2.
77 */
78 if (version > EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2) {
79 /*
80 * The TCG2 log format has variable length entries,
81 * and the information to decode the hash algorithms
82 * back into a size is contained in the first entry -
83 * pass a pointer to the final entry (to calculate its
84 * size) and the first entry (so we know how long each
85 * digest is)
86 */
87 last_entry_size =
88 __calc_tpm2_event_size((void *)last_entry_addr,
89 (void *)(long)log_location,
90 false);
91 } else {
92 last_entry_size = sizeof(struct tcpa_event) +
93 ((struct tcpa_event *) last_entry_addr)->event_size;
94 }
95 log_size = log_last_entry - log_location + last_entry_size;
96 }
97
98 /* Allocate space for the logs and copy them. */
99 status = efi_bs_call(allocate_pool, EFI_LOADER_DATA,
100 sizeof(*log_tbl) + log_size, (void **)&log_tbl);
101
102 if (status != EFI_SUCCESS) {
103 efi_err("Unable to allocate memory for event log\n");
104 return;
105 }
106
107 /*
108 * Figure out whether any events have already been logged to the
109 * final events structure, and if so how much space they take up
110 */
111 if (final_events_table && final_events_table->nr_events) {
112 struct tcg_pcr_event2_head *header;
113 int offset;
114 void *data;
115 int event_size;
116 int i = final_events_table->nr_events;
117
118 data = (void *)final_events_table;
119 offset = sizeof(final_events_table->version) +
120 sizeof(final_events_table->nr_events);
121
122 while (i > 0) {
123 header = data + offset + final_events_size;
124 event_size = __calc_tpm2_event_size(header,
125 (void *)(long)log_location,
126 false);
127 final_events_size += event_size;
128 i--;
129 }
130 }
131
132 memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
133 log_tbl->size = log_size;
134 log_tbl->final_events_preboot_size = final_events_size;
135 log_tbl->version = version;
136 memcpy(log_tbl->log, (void *) first_entry_addr, log_size);
137
138 status = efi_bs_call(install_configuration_table,
139 &linux_eventlog_guid, log_tbl);
140 if (status != EFI_SUCCESS)
141 goto err_free;
142 return;
143
144err_free:
145 efi_bs_call(free_pool, log_tbl);
146}
147
148void efi_retrieve_eventlog(void)
149{
150 struct efi_tcg2_final_events_table *final_events_table = NULL;
151 efi_physical_addr_t log_location = 0, log_last_entry = 0;
152 efi_guid_t tpm2_guid = EFI_TCG2_PROTOCOL_GUID;
153 int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2;
154 efi_tcg2_protocol_t *tpm2 = NULL;
155 efi_bool_t truncated;
156 efi_status_t status;
157
158 status = efi_bs_call(locate_protocol, &tpm2_guid, NULL, (void **)&tpm2);
159 if (status == EFI_SUCCESS) {
160 status = efi_call_proto(tpm2, get_event_log, version, &log_location,
161 &log_last_entry, &truncated);
162
163 if (status != EFI_SUCCESS || !log_location) {
164 version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
165 status = efi_call_proto(tpm2, get_event_log, version,
166 &log_location, &log_last_entry,
167 &truncated);
168 } else {
169 final_events_table =
170 get_efi_config_table(EFI_TCG2_FINAL_EVENTS_TABLE_GUID);
171 }
172 } else {
173 efi_guid_t cc_guid = EFI_CC_MEASUREMENT_PROTOCOL_GUID;
174 efi_cc_protocol_t *cc = NULL;
175
176 status = efi_bs_call(locate_protocol, &cc_guid, NULL, (void **)&cc);
177 if (status != EFI_SUCCESS)
178 return;
179
180 version = EFI_CC_EVENT_LOG_FORMAT_TCG_2;
181 status = efi_call_proto(cc, get_event_log, version, &log_location,
182 &log_last_entry, &truncated);
183
184 final_events_table =
185 get_efi_config_table(EFI_CC_FINAL_EVENTS_TABLE_GUID);
186 }
187
188 if (status != EFI_SUCCESS || !log_location)
189 return;
190
191 efi_retrieve_tcg2_eventlog(version, log_location, log_last_entry,
192 truncated, final_events_table);
193}