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