1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
|
// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/dmi.h>
#include <linux/err.h>
#include <linux/efi.h>
#include <linux/slab.h>
#include <linux/ima.h>
#include <keys/asymmetric-type.h>
#include <keys/system_keyring.h>
#include "../integrity.h"
#include "keyring_handler.h"
/*
* On T2 Macs reading the db and dbx efi variables to load UEFI Secure Boot
* certificates causes occurrence of a page fault in Apple's firmware and
* a crash disabling EFI runtime services. The following quirk skips reading
* these variables.
*/
static const struct dmi_system_id uefi_skip_cert[] = {
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,2") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,3") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,4") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,2") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,3") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,4") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,2") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir9,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacMini8,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacPro7,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,2") },
{ }
};
/*
* Look to see if a UEFI variable called MokIgnoreDB exists and return true if
* it does.
*
* This UEFI variable is set by the shim if a user tells the shim to not use
* the certs/hashes in the UEFI db variable for verification purposes. If it
* is set, we should ignore the db variable also and the true return indicates
* this.
*/
static __init bool uefi_check_ignore_db(void)
{
efi_status_t status;
unsigned int db = 0;
unsigned long size = sizeof(db);
efi_guid_t guid = EFI_SHIM_LOCK_GUID;
status = efi.get_variable(L"MokIgnoreDB", &guid, NULL, &size, &db);
return status == EFI_SUCCESS;
}
/*
* Get a certificate list blob from the named EFI variable.
*/
static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid,
unsigned long *size, efi_status_t *status)
{
unsigned long lsize = 4;
unsigned long tmpdb[4];
void *db;
*status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb);
if (*status == EFI_NOT_FOUND)
return NULL;
if (*status != EFI_BUFFER_TOO_SMALL) {
pr_err("Couldn't get size: 0x%lx\n", *status);
return NULL;
}
db = kmalloc(lsize, GFP_KERNEL);
if (!db)
return NULL;
*status = efi.get_variable(name, guid, NULL, &lsize, db);
if (*status != EFI_SUCCESS) {
kfree(db);
pr_err("Error reading db var: 0x%lx\n", *status);
return NULL;
}
*size = lsize;
return db;
}
/*
* load_moklist_certs() - Load MokList certs
*
* Load the certs contained in the UEFI MokListRT database into the
* platform trusted keyring.
*
* This routine checks the EFI MOK config table first. If and only if
* that fails, this routine uses the MokListRT ordinary UEFI variable.
*
* Return: Status
*/
static int __init load_moklist_certs(void)
{
struct efi_mokvar_table_entry *mokvar_entry;
efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
void *mok;
unsigned long moksize;
efi_status_t status;
int rc;
/* First try to load certs from the EFI MOKvar config table.
* It's not an error if the MOKvar config table doesn't exist
* or the MokListRT entry is not found in it.
*/
mokvar_entry = efi_mokvar_entry_find("MokListRT");
if (mokvar_entry) {
rc = parse_efi_signature_list("UEFI:MokListRT (MOKvar table)",
mokvar_entry->data,
mokvar_entry->data_size,
get_handler_for_mok);
/* All done if that worked. */
if (!rc)
return rc;
pr_err("Couldn't parse MokListRT signatures from EFI MOKvar config table: %d\n",
rc);
}
/* Get MokListRT. It might not exist, so it isn't an error
* if we can't get it.
*/
mok = get_cert_list(L"MokListRT", &mok_var, &moksize, &status);
if (mok) {
rc = parse_efi_signature_list("UEFI:MokListRT",
mok, moksize, get_handler_for_mok);
kfree(mok);
if (rc)
pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
return rc;
}
if (status == EFI_NOT_FOUND)
pr_debug("MokListRT variable wasn't found\n");
else
pr_info("Couldn't get UEFI MokListRT\n");
return 0;
}
/*
* load_uefi_certs() - Load certs from UEFI sources
*
* Load the certs contained in the UEFI databases into the platform trusted
* keyring and the UEFI blacklisted X.509 cert SHA256 hashes into the blacklist
* keyring.
*/
static int __init load_uefi_certs(void)
{
efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
void *db = NULL, *dbx = NULL, *mokx = NULL;
unsigned long dbsize = 0, dbxsize = 0, mokxsize = 0;
efi_status_t status;
int rc = 0;
const struct dmi_system_id *dmi_id;
dmi_id = dmi_first_match(uefi_skip_cert);
if (dmi_id) {
pr_err("Reading UEFI Secure Boot Certs is not supported on T2 Macs.\n");
return false;
}
if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
return false;
/* Get db and dbx. They might not exist, so it isn't an error
* if we can't get them.
*/
if (!uefi_check_ignore_db()) {
db = get_cert_list(L"db", &secure_var, &dbsize, &status);
if (!db) {
if (status == EFI_NOT_FOUND)
pr_debug("MODSIGN: db variable wasn't found\n");
else
pr_err("MODSIGN: Couldn't get UEFI db list\n");
} else {
rc = parse_efi_signature_list("UEFI:db",
db, dbsize, get_handler_for_db);
if (rc)
pr_err("Couldn't parse db signatures: %d\n",
rc);
kfree(db);
}
}
dbx = get_cert_list(L"dbx", &secure_var, &dbxsize, &status);
if (!dbx) {
if (status == EFI_NOT_FOUND)
pr_debug("dbx variable wasn't found\n");
else
pr_info("Couldn't get UEFI dbx list\n");
} else {
rc = parse_efi_signature_list("UEFI:dbx",
dbx, dbxsize,
get_handler_for_dbx);
if (rc)
pr_err("Couldn't parse dbx signatures: %d\n", rc);
kfree(dbx);
}
/* the MOK/MOKx can not be trusted when secure boot is disabled */
if (!arch_ima_get_secureboot())
return 0;
mokx = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &status);
if (!mokx) {
if (status == EFI_NOT_FOUND)
pr_debug("mokx variable wasn't found\n");
else
pr_info("Couldn't get mokx list\n");
} else {
rc = parse_efi_signature_list("UEFI:MokListXRT",
mokx, mokxsize,
get_handler_for_dbx);
if (rc)
pr_err("Couldn't parse mokx signatures %d\n", rc);
kfree(mokx);
}
/* Load the MokListRT certs */
rc = load_moklist_certs();
return rc;
}
late_initcall(load_uefi_certs);
|
