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/verification.h>
15 #include <keys/asymmetric-type.h>
16 #include <keys/system_keyring.h>
17 #include <crypto/pkcs7.h>
18
19 static struct key *builtin_trusted_keys;
20 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
21 static struct key *secondary_trusted_keys;
22 #endif
23 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
24 static struct key *platform_trusted_keys;
25 #endif
26
27 extern __initconst const u8 system_certificate_list[];
28 extern __initconst const unsigned long system_certificate_list_size;
29
30 /**
31 * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
32 *
33 * Restrict the addition of keys into a keyring based on the key-to-be-added
34 * being vouched for by a key in the built in system keyring.
35 */
restrict_link_by_builtin_trusted(struct key * dest_keyring,const struct key_type * type,const union key_payload * payload,struct key * restriction_key)36 int restrict_link_by_builtin_trusted(struct key *dest_keyring,
37 const struct key_type *type,
38 const union key_payload *payload,
39 struct key *restriction_key)
40 {
41 return restrict_link_by_signature(dest_keyring, type, payload,
42 builtin_trusted_keys);
43 }
44
45 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
46 /**
47 * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
48 * addition by both builtin and secondary keyrings
49 *
50 * Restrict the addition of keys into a keyring based on the key-to-be-added
51 * being vouched for by a key in either the built-in or the secondary system
52 * keyrings.
53 */
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)54 int restrict_link_by_builtin_and_secondary_trusted(
55 struct key *dest_keyring,
56 const struct key_type *type,
57 const union key_payload *payload,
58 struct key *restrict_key)
59 {
60 /* If we have a secondary trusted keyring, then that contains a link
61 * through to the builtin keyring and the search will follow that link.
62 */
63 if (type == &key_type_keyring &&
64 dest_keyring == secondary_trusted_keys &&
65 payload == &builtin_trusted_keys->payload)
66 /* Allow the builtin keyring to be added to the secondary */
67 return 0;
68
69 return restrict_link_by_signature(dest_keyring, type, payload,
70 secondary_trusted_keys);
71 }
72
73 /**
74 * Allocate a struct key_restriction for the "builtin and secondary trust"
75 * keyring. Only for use in system_trusted_keyring_init().
76 */
get_builtin_and_secondary_restriction(void)77 static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
78 {
79 struct key_restriction *restriction;
80
81 restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
82
83 if (!restriction)
84 panic("Can't allocate secondary trusted keyring restriction\n");
85
86 restriction->check = restrict_link_by_builtin_and_secondary_trusted;
87
88 return restriction;
89 }
90 #endif
91
92 /*
93 * Create the trusted keyrings
94 */
system_trusted_keyring_init(void)95 static __init int system_trusted_keyring_init(void)
96 {
97 pr_notice("Initialise system trusted keyrings\n");
98
99 builtin_trusted_keys =
100 keyring_alloc(".builtin_trusted_keys",
101 KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
102 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
103 KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
104 KEY_ALLOC_NOT_IN_QUOTA,
105 NULL, NULL);
106 if (IS_ERR(builtin_trusted_keys))
107 panic("Can't allocate builtin trusted keyring\n");
108
109 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
110 secondary_trusted_keys =
111 keyring_alloc(".secondary_trusted_keys",
112 KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
113 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
114 KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
115 KEY_USR_WRITE),
116 KEY_ALLOC_NOT_IN_QUOTA,
117 get_builtin_and_secondary_restriction(),
118 NULL);
119 if (IS_ERR(secondary_trusted_keys))
120 panic("Can't allocate secondary trusted keyring\n");
121
122 if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
123 panic("Can't link trusted keyrings\n");
124 #endif
125
126 return 0;
127 }
128
129 /*
130 * Must be initialised before we try and load the keys into the keyring.
131 */
132 device_initcall(system_trusted_keyring_init);
133
134 /*
135 * Load the compiled-in list of X.509 certificates.
136 */
load_system_certificate_list(void)137 static __init int load_system_certificate_list(void)
138 {
139 key_ref_t key;
140 const u8 *p, *end;
141 size_t plen;
142
143 pr_notice("Loading compiled-in X.509 certificates\n");
144
145 p = system_certificate_list;
146 end = p + system_certificate_list_size;
147 while (p < end) {
148 /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
149 * than 256 bytes in size.
150 */
151 if (end - p < 4)
152 goto dodgy_cert;
153 if (p[0] != 0x30 &&
154 p[1] != 0x82)
155 goto dodgy_cert;
156 plen = (p[2] << 8) | p[3];
157 plen += 4;
158 if (plen > end - p)
159 goto dodgy_cert;
160
161 key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
162 "asymmetric",
163 NULL,
164 p,
165 plen,
166 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
167 KEY_USR_VIEW | KEY_USR_READ),
168 KEY_ALLOC_NOT_IN_QUOTA |
169 KEY_ALLOC_BUILT_IN |
170 KEY_ALLOC_BYPASS_RESTRICTION);
171 if (IS_ERR(key)) {
172 pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
173 PTR_ERR(key));
174 } else {
175 pr_notice("Loaded X.509 cert '%s'\n",
176 key_ref_to_ptr(key)->description);
177 key_ref_put(key);
178 }
179 p += plen;
180 }
181
182 return 0;
183
184 dodgy_cert:
185 pr_err("Problem parsing in-kernel X.509 certificate list\n");
186 return 0;
187 }
188 late_initcall(load_system_certificate_list);
189
190 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
191
192 /**
193 * verify_pkcs7_message_sig - Verify a PKCS#7-based signature on system data.
194 * @data: The data to be verified (NULL if expecting internal data).
195 * @len: Size of @data.
196 * @pkcs7: The PKCS#7 message that is the signature.
197 * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
198 * (void *)1UL for all trusted keys).
199 * @usage: The use to which the key is being put.
200 * @view_content: Callback to gain access to content.
201 * @ctx: Context for callback.
202 */
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)203 int verify_pkcs7_message_sig(const void *data, size_t len,
204 struct pkcs7_message *pkcs7,
205 struct key *trusted_keys,
206 enum key_being_used_for usage,
207 int (*view_content)(void *ctx,
208 const void *data, size_t len,
209 size_t asn1hdrlen),
210 void *ctx)
211 {
212 int ret;
213
214 /* The data should be detached - so we need to supply it. */
215 if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
216 pr_err("PKCS#7 signature with non-detached data\n");
217 ret = -EBADMSG;
218 goto error;
219 }
220
221 ret = pkcs7_verify(pkcs7, usage);
222 if (ret < 0)
223 goto error;
224
225 if (!trusted_keys) {
226 trusted_keys = builtin_trusted_keys;
227 } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
228 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
229 trusted_keys = secondary_trusted_keys;
230 #else
231 trusted_keys = builtin_trusted_keys;
232 #endif
233 } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
234 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
235 trusted_keys = platform_trusted_keys;
236 #else
237 trusted_keys = NULL;
238 #endif
239 if (!trusted_keys) {
240 ret = -ENOKEY;
241 pr_devel("PKCS#7 platform keyring is not available\n");
242 goto error;
243 }
244 }
245 ret = pkcs7_validate_trust(pkcs7, trusted_keys);
246 if (ret < 0) {
247 if (ret == -ENOKEY)
248 pr_devel("PKCS#7 signature not signed with a trusted key\n");
249 goto error;
250 }
251
252 if (view_content) {
253 size_t asn1hdrlen;
254
255 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
256 if (ret < 0) {
257 if (ret == -ENODATA)
258 pr_devel("PKCS#7 message does not contain data\n");
259 goto error;
260 }
261
262 ret = view_content(ctx, data, len, asn1hdrlen);
263 }
264
265 error:
266 pr_devel("<==%s() = %d\n", __func__, ret);
267 return ret;
268 }
269
270 /**
271 * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
272 * @data: The data to be verified (NULL if expecting internal data).
273 * @len: Size of @data.
274 * @raw_pkcs7: The PKCS#7 message that is the signature.
275 * @pkcs7_len: The size of @raw_pkcs7.
276 * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
277 * (void *)1UL for all trusted keys).
278 * @usage: The use to which the key is being put.
279 * @view_content: Callback to gain access to content.
280 * @ctx: Context for callback.
281 */
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)282 int verify_pkcs7_signature(const void *data, size_t len,
283 const void *raw_pkcs7, size_t pkcs7_len,
284 struct key *trusted_keys,
285 enum key_being_used_for usage,
286 int (*view_content)(void *ctx,
287 const void *data, size_t len,
288 size_t asn1hdrlen),
289 void *ctx)
290 {
291 struct pkcs7_message *pkcs7;
292 int ret;
293
294 pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
295 if (IS_ERR(pkcs7))
296 return PTR_ERR(pkcs7);
297
298 ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
299 view_content, ctx);
300
301 pkcs7_free_message(pkcs7);
302 pr_devel("<==%s() = %d\n", __func__, ret);
303 return ret;
304 }
305 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
306
307 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
308
309 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
set_platform_trusted_keys(struct key * keyring)310 void __init set_platform_trusted_keys(struct key *keyring)
311 {
312 platform_trusted_keys = keyring;
313 }
314 #endif
315
