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
|
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2020 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*
* UEFI Secure Boot related checkings.
*/
#include <grub/efi/efi.h>
#include <grub/efi/pe32.h>
#include <grub/efi/sb.h>
#include <grub/env.h>
#include <grub/err.h>
#include <grub/file.h>
#include <grub/i386/linux.h>
#include <grub/kernel.h>
#include <grub/mm.h>
#include <grub/types.h>
#include <grub/verify.h>
static grub_efi_guid_t shim_lock_guid = GRUB_EFI_SHIM_LOCK_GUID;
/*
* Determine whether we're in secure boot mode.
*
* Please keep the logic in sync with the Linux kernel,
* drivers/firmware/efi/libstub/secureboot.c:efi_get_secureboot().
*/
grub_uint8_t
grub_efi_get_secureboot (void)
{
static grub_efi_guid_t efi_variable_guid = GRUB_EFI_GLOBAL_VARIABLE_GUID;
grub_efi_status_t status;
grub_efi_uint32_t attr = 0;
grub_size_t size = 0;
grub_uint8_t *secboot = NULL;
grub_uint8_t *setupmode = NULL;
grub_uint8_t *moksbstate = NULL;
grub_uint8_t secureboot = GRUB_EFI_SECUREBOOT_MODE_UNKNOWN;
const char *secureboot_str = "UNKNOWN";
status = grub_efi_get_variable ("SecureBoot", &efi_variable_guid,
&size, (void **) &secboot);
if (status == GRUB_EFI_NOT_FOUND)
{
secureboot = GRUB_EFI_SECUREBOOT_MODE_DISABLED;
goto out;
}
if (status != GRUB_EFI_SUCCESS)
goto out;
status = grub_efi_get_variable ("SetupMode", &efi_variable_guid,
&size, (void **) &setupmode);
if (status != GRUB_EFI_SUCCESS)
goto out;
if ((*secboot == 0) || (*setupmode == 1))
{
secureboot = GRUB_EFI_SECUREBOOT_MODE_DISABLED;
goto out;
}
/*
* See if a user has put the shim into insecure mode. If so, and if the
* variable doesn't have the runtime attribute set, we might as well
* honor that.
*/
status = grub_efi_get_variable_with_attributes ("MokSBState", &shim_lock_guid,
&size, (void **) &moksbstate, &attr);
/* If it fails, we don't care why. Default to secure. */
if (status != GRUB_EFI_SUCCESS)
{
secureboot = GRUB_EFI_SECUREBOOT_MODE_ENABLED;
goto out;
}
if (!(attr & GRUB_EFI_VARIABLE_RUNTIME_ACCESS) && *moksbstate == 1)
{
secureboot = GRUB_EFI_SECUREBOOT_MODE_DISABLED;
goto out;
}
secureboot = GRUB_EFI_SECUREBOOT_MODE_ENABLED;
out:
grub_free (moksbstate);
grub_free (setupmode);
grub_free (secboot);
if (secureboot == GRUB_EFI_SECUREBOOT_MODE_DISABLED)
secureboot_str = "Disabled";
else if (secureboot == GRUB_EFI_SECUREBOOT_MODE_ENABLED)
secureboot_str = "Enabled";
grub_dprintf ("efi", "UEFI Secure Boot state: %s\n", secureboot_str);
return secureboot;
}
static grub_err_t
shim_lock_verifier_init (grub_file_t io __attribute__ ((unused)),
enum grub_file_type type,
void **context __attribute__ ((unused)),
enum grub_verify_flags *flags)
{
*flags = GRUB_VERIFY_FLAGS_SKIP_VERIFICATION;
switch (type & GRUB_FILE_TYPE_MASK)
{
case GRUB_FILE_TYPE_LINUX_KERNEL:
case GRUB_FILE_TYPE_MULTIBOOT_KERNEL:
case GRUB_FILE_TYPE_BSD_KERNEL:
case GRUB_FILE_TYPE_XNU_KERNEL:
case GRUB_FILE_TYPE_PLAN9_KERNEL:
case GRUB_FILE_TYPE_EFI_CHAINLOADED_IMAGE:
*flags = GRUB_VERIFY_FLAGS_SINGLE_CHUNK;
/* Fall through. */
default:
return GRUB_ERR_NONE;
}
}
static grub_err_t
shim_lock_verifier_write (void *context __attribute__ ((unused)), void *buf, grub_size_t size)
{
grub_efi_shim_lock_protocol_t *sl = grub_efi_locate_protocol (&shim_lock_guid, 0);
if (!sl)
return grub_error (GRUB_ERR_ACCESS_DENIED, N_("shim_lock protocol not found"));
if (sl->verify (buf, size) != GRUB_EFI_SUCCESS)
return grub_error (GRUB_ERR_BAD_SIGNATURE, N_("bad shim signature"));
return GRUB_ERR_NONE;
}
struct grub_file_verifier shim_lock_verifier =
{
.name = "shim_lock_verifier",
.init = shim_lock_verifier_init,
.write = shim_lock_verifier_write
};
void
grub_shim_lock_verifier_setup (void)
{
struct grub_module_header *header;
grub_efi_shim_lock_protocol_t *sl =
grub_efi_locate_protocol (&shim_lock_guid, 0);
/* shim_lock is missing, check if GRUB image is built with --disable-shim-lock. */
if (!sl)
{
FOR_MODULES (header)
{
if (header->type == OBJ_TYPE_DISABLE_SHIM_LOCK)
return;
}
}
/* Secure Boot is off. Do not load shim_lock. */
if (grub_efi_get_secureboot () != GRUB_EFI_SECUREBOOT_MODE_ENABLED)
return;
/* Enforce shim_lock_verifier. */
grub_verifier_register (&shim_lock_verifier);
grub_env_set ("shim_lock", "y");
grub_env_export ("shim_lock");
}
|
