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