1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* System trusted keyring for trusted public keys
3 *
4 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #include <linux/export.h>
9 #include <linux/kernel.h>
10 #include <linux/sched.h>
11 #include <linux/cred.h>
12 #include <linux/err.h>
13 #include <linux/slab.h>
14 #include <linux/uidgid.h>
15 #include <linux/verification.h>
16 #include <keys/asymmetric-type.h>
17 #include <keys/system_keyring.h>
18 #include <crypto/pkcs7.h>
19 #include "common.h"
20
21 static struct key *builtin_trusted_keys;
22 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
23 static struct key *secondary_trusted_keys;
24 #endif
25 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
26 static struct key *platform_trusted_keys;
27 #endif
28
29 extern __initconst const u8 system_certificate_list[];
30 extern __initconst const unsigned long system_certificate_list_size;
31 extern __initconst const unsigned long module_cert_size;
32
33 /**
34 * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
35 *
36 * Restrict the addition of keys into a keyring based on the key-to-be-added
37 * being vouched for by a key in the built in system keyring.
38 */
restrict_link_by_builtin_trusted(struct key * dest_keyring,const struct key_type * type,const union key_payload * payload,struct key * restriction_key)39 int restrict_link_by_builtin_trusted(struct key *dest_keyring,
40 const struct key_type *type,
41 const union key_payload *payload,
42 struct key *restriction_key)
43 {
44 return restrict_link_by_signature(dest_keyring, type, payload,
45 builtin_trusted_keys);
46 }
47
48 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
49 /**
50 * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
51 * addition by both builtin and secondary keyrings
52 *
53 * Restrict the addition of keys into a keyring based on the key-to-be-added
54 * being vouched for by a key in either the built-in or the secondary system
55 * keyrings.
56 */
restrict_link_by_builtin_and_secondary_trusted(struct key * dest_keyring,const struct key_type * type,const union key_payload * payload,struct key * restrict_key)57 int restrict_link_by_builtin_and_secondary_trusted(
58 struct key *dest_keyring,
59 const struct key_type *type,
60 const union key_payload *payload,
61 struct key *restrict_key)
62 {
63 /* If we have a secondary trusted keyring, then that contains a link
64 * through to the builtin keyring and the search will follow that link.
65 */
66 if (type == &key_type_keyring &&
67 dest_keyring == secondary_trusted_keys &&
68 payload == &builtin_trusted_keys->payload)
69 /* Allow the builtin keyring to be added to the secondary */
70 return 0;
71
72 return restrict_link_by_signature(dest_keyring, type, payload,
73 secondary_trusted_keys);
74 }
75
76 /**
77 * Allocate a struct key_restriction for the "builtin and secondary trust"
78 * keyring. Only for use in system_trusted_keyring_init().
79 */
get_builtin_and_secondary_restriction(void)80 static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
81 {
82 struct key_restriction *restriction;
83
84 restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
85
86 if (!restriction)
87 panic("Can't allocate secondary trusted keyring restriction\n");
88
89 restriction->check = restrict_link_by_builtin_and_secondary_trusted;
90
91 return restriction;
92 }
93 #endif
94
95 /*
96 * Create the trusted keyrings
97 */
system_trusted_keyring_init(void)98 static __init int system_trusted_keyring_init(void)
99 {
100 pr_notice("Initialise system trusted keyrings\n");
101
102 builtin_trusted_keys =
103 keyring_alloc(".builtin_trusted_keys",
104 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
105 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
106 KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
107 KEY_ALLOC_NOT_IN_QUOTA,
108 NULL, NULL);
109 if (IS_ERR(builtin_trusted_keys))
110 panic("Can't allocate builtin trusted keyring\n");
111
112 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
113 secondary_trusted_keys =
114 keyring_alloc(".secondary_trusted_keys",
115 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
116 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
117 KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
118 KEY_USR_WRITE),
119 KEY_ALLOC_NOT_IN_QUOTA,
120 get_builtin_and_secondary_restriction(),
121 NULL);
122 if (IS_ERR(secondary_trusted_keys))
123 panic("Can't allocate secondary trusted keyring\n");
124
125 if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
126 panic("Can't link trusted keyrings\n");
127 #endif
128
129 return 0;
130 }
131
132 /*
133 * Must be initialised before we try and load the keys into the keyring.
134 */
135 device_initcall(system_trusted_keyring_init);
136
load_module_cert(struct key * keyring)137 __init int load_module_cert(struct key *keyring)
138 {
139 if (!IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG))
140 return 0;
141
142 pr_notice("Loading compiled-in module X.509 certificates\n");
143
144 return load_certificate_list(system_certificate_list, module_cert_size, keyring);
145 }
146
147 /*
148 * Load the compiled-in list of X.509 certificates.
149 */
load_system_certificate_list(void)150 static __init int load_system_certificate_list(void)
151 {
152 const u8 *p;
153 unsigned long size;
154
155 pr_notice("Loading compiled-in X.509 certificates\n");
156
157 #ifdef CONFIG_MODULE_SIG
158 p = system_certificate_list;
159 size = system_certificate_list_size;
160 #else
161 p = system_certificate_list + module_cert_size;
162 size = system_certificate_list_size - module_cert_size;
163 #endif
164
165 return load_certificate_list(p, size, builtin_trusted_keys);
166 }
167 late_initcall(load_system_certificate_list);
168
169 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
170
171 /**
172 * verify_pkcs7_message_sig - Verify a PKCS#7-based signature on system data.
173 * @data: The data to be verified (NULL if expecting internal data).
174 * @len: Size of @data.
175 * @pkcs7: The PKCS#7 message that is the signature.
176 * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
177 * (void *)1UL for all trusted keys).
178 * @usage: The use to which the key is being put.
179 * @view_content: Callback to gain access to content.
180 * @ctx: Context for callback.
181 */
verify_pkcs7_message_sig(const void * data,size_t len,struct pkcs7_message * pkcs7,struct key * trusted_keys,enum key_being_used_for usage,int (* view_content)(void * ctx,const void * data,size_t len,size_t asn1hdrlen),void * ctx)182 int verify_pkcs7_message_sig(const void *data, size_t len,
183 struct pkcs7_message *pkcs7,
184 struct key *trusted_keys,
185 enum key_being_used_for usage,
186 int (*view_content)(void *ctx,
187 const void *data, size_t len,
188 size_t asn1hdrlen),
189 void *ctx)
190 {
191 int ret;
192
193 /* The data should be detached - so we need to supply it. */
194 if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
195 pr_err("PKCS#7 signature with non-detached data\n");
196 ret = -EBADMSG;
197 goto error;
198 }
199
200 ret = pkcs7_verify(pkcs7, usage);
201 if (ret < 0)
202 goto error;
203
204 if (!trusted_keys) {
205 trusted_keys = builtin_trusted_keys;
206 } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
207 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
208 trusted_keys = secondary_trusted_keys;
209 #else
210 trusted_keys = builtin_trusted_keys;
211 #endif
212 } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
213 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
214 trusted_keys = platform_trusted_keys;
215 #else
216 trusted_keys = NULL;
217 #endif
218 if (!trusted_keys) {
219 ret = -ENOKEY;
220 pr_devel("PKCS#7 platform keyring is not available\n");
221 goto error;
222 }
223
224 ret = is_key_on_revocation_list(pkcs7);
225 if (ret != -ENOKEY) {
226 pr_devel("PKCS#7 platform key is on revocation list\n");
227 goto error;
228 }
229 }
230 ret = pkcs7_validate_trust(pkcs7, trusted_keys);
231 if (ret < 0) {
232 if (ret == -ENOKEY)
233 pr_devel("PKCS#7 signature not signed with a trusted key\n");
234 goto error;
235 }
236
237 if (view_content) {
238 size_t asn1hdrlen;
239
240 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
241 if (ret < 0) {
242 if (ret == -ENODATA)
243 pr_devel("PKCS#7 message does not contain data\n");
244 goto error;
245 }
246
247 ret = view_content(ctx, data, len, asn1hdrlen);
248 }
249
250 error:
251 pr_devel("<==%s() = %d\n", __func__, ret);
252 return ret;
253 }
254
255 /**
256 * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
257 * @data: The data to be verified (NULL if expecting internal data).
258 * @len: Size of @data.
259 * @raw_pkcs7: The PKCS#7 message that is the signature.
260 * @pkcs7_len: The size of @raw_pkcs7.
261 * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
262 * (void *)1UL for all trusted keys).
263 * @usage: The use to which the key is being put.
264 * @view_content: Callback to gain access to content.
265 * @ctx: Context for callback.
266 */
verify_pkcs7_signature(const void * data,size_t len,const void * raw_pkcs7,size_t pkcs7_len,struct key * trusted_keys,enum key_being_used_for usage,int (* view_content)(void * ctx,const void * data,size_t len,size_t asn1hdrlen),void * ctx)267 int verify_pkcs7_signature(const void *data, size_t len,
268 const void *raw_pkcs7, size_t pkcs7_len,
269 struct key *trusted_keys,
270 enum key_being_used_for usage,
271 int (*view_content)(void *ctx,
272 const void *data, size_t len,
273 size_t asn1hdrlen),
274 void *ctx)
275 {
276 struct pkcs7_message *pkcs7;
277 int ret;
278
279 pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
280 if (IS_ERR(pkcs7))
281 return PTR_ERR(pkcs7);
282
283 ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
284 view_content, ctx);
285
286 pkcs7_free_message(pkcs7);
287 pr_devel("<==%s() = %d\n", __func__, ret);
288 return ret;
289 }
290 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
291
292 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
293
294 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
set_platform_trusted_keys(struct key * keyring)295 void __init set_platform_trusted_keys(struct key *keyring)
296 {
297 platform_trusted_keys = keyring;
298 }
299 #endif
300
