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