1/* System trusted keyring for trusted public keys
2 *
3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/export.h>
13#include <linux/kernel.h>
14#include <linux/sched.h>
15#include <linux/cred.h>
16#include <linux/err.h>
17#include <linux/slab.h>
18#include <linux/verification.h>
19#include <keys/asymmetric-type.h>
20#include <keys/system_keyring.h>
21#include <crypto/pkcs7.h>
22
23static struct key *builtin_trusted_keys;
24#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
25static struct key *secondary_trusted_keys;
26#endif
27#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
28static struct key *platform_trusted_keys;
29#endif
30
31extern __initconst const u8 system_certificate_list[];
32extern __initconst const unsigned long system_certificate_list_size;
33
34/**
35 * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
36 *
37 * Restrict the addition of keys into a keyring based on the key-to-be-added
38 * being vouched for by a key in the built in system keyring.
39 */
40int restrict_link_by_builtin_trusted(struct key *dest_keyring,
41 const struct key_type *type,
42 const union key_payload *payload,
43 struct key *restriction_key)
44{
45 return restrict_link_by_signature(dest_keyring, type, payload,
46 builtin_trusted_keys);
47}
48
49#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
50/**
51 * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
52 * addition by both builtin and secondary keyrings
53 *
54 * Restrict the addition of keys into a keyring based on the key-to-be-added
55 * being vouched for by a key in either the built-in or the secondary system
56 * keyrings.
57 */
58int restrict_link_by_builtin_and_secondary_trusted(
59 struct key *dest_keyring,
60 const struct key_type *type,
61 const union key_payload *payload,
62 struct key *restrict_key)
63{
64 /* If we have a secondary trusted keyring, then that contains a link
65 * through to the builtin keyring and the search will follow that link.
66 */
67 if (type == &key_type_keyring &&
68 dest_keyring == secondary_trusted_keys &&
69 payload == &builtin_trusted_keys->payload)
70 /* Allow the builtin keyring to be added to the secondary */
71 return 0;
72
73 return restrict_link_by_signature(dest_keyring, type, payload,
74 secondary_trusted_keys);
75}
76
77/**
78 * Allocate a struct key_restriction for the "builtin and secondary trust"
79 * keyring. Only for use in system_trusted_keyring_init().
80 */
81static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
82{
83 struct key_restriction *restriction;
84
85 restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
86
87 if (!restriction)
88 panic("Can't allocate secondary trusted keyring restriction\n");
89
90 restriction->check = restrict_link_by_builtin_and_secondary_trusted;
91
92 return restriction;
93}
94#endif
95
96/*
97 * Create the trusted keyrings
98 */
99static __init int system_trusted_keyring_init(void)
100{
101 pr_notice("Initialise system trusted keyrings\n");
102
103 builtin_trusted_keys =
104 keyring_alloc(".builtin_trusted_keys",
105 KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
106 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
107 KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
108 KEY_ALLOC_NOT_IN_QUOTA,
109 NULL, NULL);
110 if (IS_ERR(builtin_trusted_keys))
111 panic("Can't allocate builtin trusted keyring\n");
112
113#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
114 secondary_trusted_keys =
115 keyring_alloc(".secondary_trusted_keys",
116 KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
117 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
118 KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
119 KEY_USR_WRITE),
120 KEY_ALLOC_NOT_IN_QUOTA,
121 get_builtin_and_secondary_restriction(),
122 NULL);
123 if (IS_ERR(secondary_trusted_keys))
124 panic("Can't allocate secondary trusted keyring\n");
125
126 if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
127 panic("Can't link trusted keyrings\n");
128#endif
129
130 return 0;
131}
132
133/*
134 * Must be initialised before we try and load the keys into the keyring.
135 */
136device_initcall(system_trusted_keyring_init);
137
138/*
139 * Load the compiled-in list of X.509 certificates.
140 */
141static __init int load_system_certificate_list(void)
142{
143 key_ref_t key;
144 const u8 *p, *end;
145 size_t plen;
146
147 pr_notice("Loading compiled-in X.509 certificates\n");
148
149 p = system_certificate_list;
150 end = p + system_certificate_list_size;
151 while (p < end) {
152 /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
153 * than 256 bytes in size.
154 */
155 if (end - p < 4)
156 goto dodgy_cert;
157 if (p[0] != 0x30 &&
158 p[1] != 0x82)
159 goto dodgy_cert;
160 plen = (p[2] << 8) | p[3];
161 plen += 4;
162 if (plen > end - p)
163 goto dodgy_cert;
164
165 key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
166 "asymmetric",
167 NULL,
168 p,
169 plen,
170 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
171 KEY_USR_VIEW | KEY_USR_READ),
172 KEY_ALLOC_NOT_IN_QUOTA |
173 KEY_ALLOC_BUILT_IN |
174 KEY_ALLOC_BYPASS_RESTRICTION);
175 if (IS_ERR(key)) {
176 pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
177 PTR_ERR(key));
178 } else {
179 pr_notice("Loaded X.509 cert '%s'\n",
180 key_ref_to_ptr(key)->description);
181 key_ref_put(key);
182 }
183 p += plen;
184 }
185
186 return 0;
187
188dodgy_cert:
189 pr_err("Problem parsing in-kernel X.509 certificate list\n");
190 return 0;
191}
192late_initcall(load_system_certificate_list);
193
194#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
195
196/**
197 * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
198 * @data: The data to be verified (NULL if expecting internal data).
199 * @len: Size of @data.
200 * @raw_pkcs7: The PKCS#7 message that is the signature.
201 * @pkcs7_len: The size of @raw_pkcs7.
202 * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
203 * (void *)1UL for all trusted keys).
204 * @usage: The use to which the key is being put.
205 * @view_content: Callback to gain access to content.
206 * @ctx: Context for callback.
207 */
208int verify_pkcs7_signature(const void *data, size_t len,
209 const void *raw_pkcs7, size_t pkcs7_len,
210 struct key *trusted_keys,
211 enum key_being_used_for usage,
212 int (*view_content)(void *ctx,
213 const void *data, size_t len,
214 size_t asn1hdrlen),
215 void *ctx)
216{
217 struct pkcs7_message *pkcs7;
218 int ret;
219
220 pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
221 if (IS_ERR(pkcs7))
222 return PTR_ERR(pkcs7);
223
224 /* The data should be detached - so we need to supply it. */
225 if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
226 pr_err("PKCS#7 signature with non-detached data\n");
227 ret = -EBADMSG;
228 goto error;
229 }
230
231 ret = pkcs7_verify(pkcs7, usage);
232 if (ret < 0)
233 goto error;
234
235 if (!trusted_keys) {
236 trusted_keys = builtin_trusted_keys;
237 } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
238#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
239 trusted_keys = secondary_trusted_keys;
240#else
241 trusted_keys = builtin_trusted_keys;
242#endif
243 } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
244#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
245 trusted_keys = platform_trusted_keys;
246#else
247 trusted_keys = NULL;
248#endif
249 if (!trusted_keys) {
250 ret = -ENOKEY;
251 pr_devel("PKCS#7 platform keyring is not available\n");
252 goto error;
253 }
254 }
255 ret = pkcs7_validate_trust(pkcs7, trusted_keys);
256 if (ret < 0) {
257 if (ret == -ENOKEY)
258 pr_devel("PKCS#7 signature not signed with a trusted key\n");
259 goto error;
260 }
261
262 if (view_content) {
263 size_t asn1hdrlen;
264
265 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
266 if (ret < 0) {
267 if (ret == -ENODATA)
268 pr_devel("PKCS#7 message does not contain data\n");
269 goto error;
270 }
271
272 ret = view_content(ctx, data, len, asn1hdrlen);
273 }
274
275error:
276 pkcs7_free_message(pkcs7);
277 pr_devel("<==%s() = %d\n", __func__, ret);
278 return ret;
279}
280EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
281
282#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
283
284#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
285void __init set_platform_trusted_keys(struct key *keyring)
286{
287 platform_trusted_keys = keyring;
288}
289#endif
290