Merge tag 'tpmdd-next-20190625' of git://git.infradead.org/users/jjs/linux-tpmdd
[muen/linux.git] / 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 void efi_retrieve_tpm2_eventlog(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         struct efi_tcg2_final_events_table *final_events_table;
68         unsigned long first_entry_addr, last_entry_addr;
69         size_t log_size, last_entry_size;
70         efi_bool_t truncated;
71         int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2;
72         void *tcg2_protocol = NULL;
73         int final_events_size = 0;
74
75         status = efi_call_early(locate_protocol, &tcg2_guid, NULL,
76                                 &tcg2_protocol);
77         if (status != EFI_SUCCESS)
78                 return;
79
80         status = efi_call_proto(efi_tcg2_protocol, get_event_log,
81                                 tcg2_protocol, version, &log_location,
82                                 &log_last_entry, &truncated);
83
84         if (status != EFI_SUCCESS || !log_location) {
85                 version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
86                 status = efi_call_proto(efi_tcg2_protocol, get_event_log,
87                                         tcg2_protocol, version, &log_location,
88                                         &log_last_entry, &truncated);
89                 if (status != EFI_SUCCESS || !log_location)
90                         return;
91
92         }
93
94         first_entry_addr = (unsigned long) log_location;
95
96         /*
97          * We populate the EFI table even if the logs are empty.
98          */
99         if (!log_last_entry) {
100                 log_size = 0;
101         } else {
102                 last_entry_addr = (unsigned long) log_last_entry;
103                 /*
104                  * get_event_log only returns the address of the last entry.
105                  * We need to calculate its size to deduce the full size of
106                  * the logs.
107                  */
108                 if (version == EFI_TCG2_EVENT_LOG_FORMAT_TCG_2) {
109                         /*
110                          * The TCG2 log format has variable length entries,
111                          * and the information to decode the hash algorithms
112                          * back into a size is contained in the first entry -
113                          * pass a pointer to the final entry (to calculate its
114                          * size) and the first entry (so we know how long each
115                          * digest is)
116                          */
117                         last_entry_size =
118                                 __calc_tpm2_event_size((void *)last_entry_addr,
119                                                     (void *)(long)log_location,
120                                                     false);
121                 } else {
122                         last_entry_size = sizeof(struct tcpa_event) +
123                            ((struct tcpa_event *) last_entry_addr)->event_size;
124                 }
125                 log_size = log_last_entry - log_location + last_entry_size;
126         }
127
128         /* Allocate space for the logs and copy them. */
129         status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
130                                 sizeof(*log_tbl) + log_size,
131                                 (void **) &log_tbl);
132
133         if (status != EFI_SUCCESS) {
134                 efi_printk(sys_table_arg,
135                            "Unable to allocate memory for event log\n");
136                 return;
137         }
138
139         /*
140          * Figure out whether any events have already been logged to the
141          * final events structure, and if so how much space they take up
142          */
143         final_events_table = get_efi_config_table(sys_table_arg,
144                                                 LINUX_EFI_TPM_FINAL_LOG_GUID);
145         if (final_events_table && final_events_table->nr_events) {
146                 struct tcg_pcr_event2_head *header;
147                 int offset;
148                 void *data;
149                 int event_size;
150                 int i = final_events_table->nr_events;
151
152                 data = (void *)final_events_table;
153                 offset = sizeof(final_events_table->version) +
154                         sizeof(final_events_table->nr_events);
155
156                 while (i > 0) {
157                         header = data + offset + final_events_size;
158                         event_size = __calc_tpm2_event_size(header,
159                                                    (void *)(long)log_location,
160                                                    false);
161                         final_events_size += event_size;
162                         i--;
163                 }
164         }
165
166         memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
167         log_tbl->size = log_size;
168         log_tbl->final_events_preboot_size = final_events_size;
169         log_tbl->version = version;
170         memcpy(log_tbl->log, (void *) first_entry_addr, log_size);
171
172         status = efi_call_early(install_configuration_table,
173                                 &linux_eventlog_guid, log_tbl);
174         if (status != EFI_SUCCESS)
175                 goto err_free;
176         return;
177
178 err_free:
179         efi_call_early(free_pool, log_tbl);
180 }