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 #ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
  26 struct key *system_blacklist_keyring;
  27 #endif
  28
  29 extern __initconst const u8 system_certificate_list[];
  30 extern __initconst const unsigned long system_certificate_list_size;
  31
  32 /**
  33  * get_system_keyring - Return a pointer to the system keyring
  34  *
  35  */
  36 struct key *get_system_keyring(void)
  37 {
  38         struct key *system_keyring = NULL;
  39
  40         system_keyring = builtin_trusted_keys;
  41         return system_keyring;
  42 }
  43 EXPORT_SYMBOL_GPL(get_system_keyring);
  44
  45 /**
  46  * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
  47  *
  48  * Restrict the addition of keys into a keyring based on the key-to-be-added
  49  * being vouched for by a key in the built in system keyring.
  50  */
  51 int restrict_link_by_builtin_trusted(struct key *keyring,
  52                                      const struct key_type *type,
  53                                      const union key_payload *payload)
  54 {
  55         return restrict_link_by_signature(builtin_trusted_keys, type, payload);
  56 }
  57
  58 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  59 /**
  60  * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  61  *   addition by both builtin and secondary keyrings
  62  *
  63  * Restrict the addition of keys into a keyring based on the key-to-be-added
  64  * being vouched for by a key in either the built-in or the secondary system
  65  * keyrings.
  66  */
  67 int restrict_link_by_builtin_and_secondary_trusted(
  68         struct key *keyring,
  69         const struct key_type *type,
  70         const union key_payload *payload)
  71 {
  72         /* If we have a secondary trusted keyring, then that contains a link
  73          * through to the builtin keyring and the search will follow that link.
  74          */
  75         if (type == &key_type_keyring &&
  76             keyring == secondary_trusted_keys &&
  77             payload == &builtin_trusted_keys->payload)
  78                 /* Allow the builtin keyring to be added to the secondary */
  79                 return 0;
  80
  81         return restrict_link_by_signature(secondary_trusted_keys, type, payload);
  82 }
  83 #endif
  84
  85 /*
  86  * Create the trusted keyrings
  87  */
  88 static __init int system_trusted_keyring_init(void)
  89 {
  90         pr_notice("Initialise system trusted keyrings\n");
  91
  92         builtin_trusted_keys =
  93                 keyring_alloc(".builtin_trusted_keys",
  94                               KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
  95                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  96                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
  97                               KEY_ALLOC_NOT_IN_QUOTA,
  98                               NULL, NULL);
  99         if (IS_ERR(builtin_trusted_keys))
 100                 panic("Can't allocate builtin trusted keyring\n");
 101
 102 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 103         secondary_trusted_keys =
 104                 keyring_alloc(".secondary_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_USR_WRITE),
 109                               KEY_ALLOC_NOT_IN_QUOTA,
 110                               restrict_link_by_builtin_and_secondary_trusted,
 111                               NULL);
 112         if (IS_ERR(secondary_trusted_keys))
 113                 panic("Can't allocate secondary trusted keyring\n");
 114
 115         if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 116                 panic("Can't link trusted keyrings\n");
 117 #endif
 118 #ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
 119         system_blacklist_keyring = keyring_alloc(".system_blacklist_keyring",
 120                         KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
 121                         ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 122                          KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 123                         KEY_ALLOC_NOT_IN_QUOTA,
 124                         NULL, NULL);
 125         if (IS_ERR(system_blacklist_keyring))
 126                 panic("Can't allocate system blacklist keyring\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
 137 /*
 138  * Load the compiled-in list of X.509 certificates.
 139  */
 140 static __init int load_system_certificate_list(void)
 141 {
 142         key_ref_t key;
 143         const u8 *p, *end;
 144         size_t plen;
 145
 146         pr_notice("Loading compiled-in X.509 certificates\n");
 147
 148         p = system_certificate_list;
 149         end = p + system_certificate_list_size;
 150         while (p < end) {
 151                 /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
 152                  * than 256 bytes in size.
 153                  */
 154                 if (end - p < 4)
 155                         goto dodgy_cert;
 156                 if (p[0] != 0x30 &&
 157                     p[1] != 0x82)
 158                         goto dodgy_cert;
 159                 plen = (p[2] << 8) | p[3];
 160                 plen += 4;
 161                 if (plen > end - p)
 162                         goto dodgy_cert;
 163
 164                 key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
 165                                            "asymmetric",
 166                                            NULL,
 167                                            p,
 168                                            plen,
 169                                            ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 170                                            KEY_USR_VIEW | KEY_USR_READ),
 171                                            KEY_ALLOC_NOT_IN_QUOTA |
 172                                            KEY_ALLOC_BUILT_IN |
 173                                            KEY_ALLOC_BYPASS_RESTRICTION);
 174                 if (IS_ERR(key)) {
 175                         pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 176                                PTR_ERR(key));
 177                         WARN_ON_ONCE(1);
 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
 188 dodgy_cert:
 189         pr_err("Problem parsing in-kernel X.509 certificate list\n");
 190         return 0;
 191 }
 192 late_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  */
 208 int 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 == (void *)1UL) {
 238 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 239                 trusted_keys = secondary_trusted_keys;
 240 #else
 241                 trusted_keys = builtin_trusted_keys;
 242 #endif
 243         }
 244 #ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
 245         ret = pkcs7_validate_trust(pkcs7, system_blacklist_keyring);
 246         if (!ret) {
 247                 /* module is signed with a cert in the blacklist.  reject */
 248                 pr_err("Module key is in the blacklist\n");
 249                 ret = -EKEYREJECTED;
 250                 goto error;
 251         }
 252 #endif
 253         ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 254         if (ret < 0) {
 255                 if (ret == -ENOKEY)
 256                         pr_err("PKCS#7 signature not signed with a trusted key\n");
 257                 goto error;
 258         }
 259
 260         if (view_content) {
 261                 size_t asn1hdrlen;
 262
 263                 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 264                 if (ret < 0) {
 265                         if (ret == -ENODATA)
 266                                 pr_devel("PKCS#7 message does not contain data\n");
 267                         goto error;
 268                 }
 269
 270                 ret = view_content(ctx, data, len, asn1hdrlen);
 271         }
 272
 273 error:
 274         pkcs7_free_message(pkcs7);
 275         pr_devel("<==%s() = %d\n", __func__, ret);
 276         return ret;
 277 }
 278 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 279
 280 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */