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}
194