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

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