certs/system_keyring.c

   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/uidgid.h>
  15 #include <linux/verification.h>
  16 #include <keys/asymmetric-type.h>
  17 #include <keys/system_keyring.h>
  18 #include <crypto/pkcs7.h>
  19
  20 static struct key *builtin_trusted_keys;
  21 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  22 static struct key *secondary_trusted_keys;
  23 #endif
  24 #ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
  25 static struct key *machine_trusted_keys;
  26 #endif
  27 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
  28 static struct key *platform_trusted_keys;
  29 #endif
  30
  31 extern __initconst const u8 system_certificate_list[];
  32 extern __initconst const unsigned long system_certificate_list_size;
  33 extern __initconst const unsigned long module_cert_size;
  34
  35 /**
  36  * restrict_link_by_builtin_trusted - Restrict keyring addition by built-in CA
  37  * @dest_keyring: Keyring being linked to.
  38  * @type: The type of key being added.
  39  * @payload: The payload of the new key.
  40  * @restriction_key: A ring of keys that can be used to vouch for the new cert.
  41  *
  42  * Restrict the addition of keys into a keyring based on the key-to-be-added
  43  * being vouched for by a key in the built in system keyring.
  44  */
  45 int restrict_link_by_builtin_trusted(struct key *dest_keyring,
  46                                      const struct key_type *type,
  47                                      const union key_payload *payload,
  48                                      struct key *restriction_key)
  49 {
  50         return restrict_link_by_signature(dest_keyring, type, payload,
  51                                           builtin_trusted_keys);
  52 }
  53
  54 /**
  55  * restrict_link_by_digsig_builtin - Restrict digitalSignature key additions by the built-in keyring
  56  * @dest_keyring: Keyring being linked to.
  57  * @type: The type of key being added.
  58  * @payload: The payload of the new key.
  59  * @restriction_key: A ring of keys that can be used to vouch for the new cert.
  60  *
  61  * Restrict the addition of keys into a keyring based on the key-to-be-added
  62  * being vouched for by a key in the built in system keyring. The new key
  63  * must have the digitalSignature usage field set.
  64  */
  65 int restrict_link_by_digsig_builtin(struct key *dest_keyring,
  66                                     const struct key_type *type,
  67                                     const union key_payload *payload,
  68                                     struct key *restriction_key)
  69 {
  70         return restrict_link_by_digsig(dest_keyring, type, payload,
  71                                        builtin_trusted_keys);
  72 }
  73
  74 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  75 /**
  76  * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  77  *   addition by both built-in and secondary keyrings.
  78  * @dest_keyring: Keyring being linked to.
  79  * @type: The type of key being added.
  80  * @payload: The payload of the new key.
  81  * @restrict_key: A ring of keys that can be used to vouch for the new cert.
  82  *
  83  * Restrict the addition of keys into a keyring based on the key-to-be-added
  84  * being vouched for by a key in either the built-in or the secondary system
  85  * keyrings.
  86  */
  87 int restrict_link_by_builtin_and_secondary_trusted(
  88         struct key *dest_keyring,
  89         const struct key_type *type,
  90         const union key_payload *payload,
  91         struct key *restrict_key)
  92 {
  93         /* If we have a secondary trusted keyring, then that contains a link
  94          * through to the builtin keyring and the search will follow that link.
  95          */
  96         if (type == &key_type_keyring &&
  97             dest_keyring == secondary_trusted_keys &&
  98             payload == &builtin_trusted_keys->payload)
  99                 /* Allow the builtin keyring to be added to the secondary */
 100                 return 0;
 101
 102         return restrict_link_by_signature(dest_keyring, type, payload,
 103                                           secondary_trusted_keys);
 104 }
 105
 106 /**
 107  * restrict_link_by_digsig_builtin_and_secondary - Restrict by digitalSignature.
 108  * @dest_keyring: Keyring being linked to.
 109  * @type: The type of key being added.
 110  * @payload: The payload of the new key.
 111  * @restrict_key: A ring of keys that can be used to vouch for the new cert.
 112  *
 113  * Restrict the addition of keys into a keyring based on the key-to-be-added
 114  * being vouched for by a key in either the built-in or the secondary system
 115  * keyrings. The new key must have the digitalSignature usage field set.
 116  */
 117 int restrict_link_by_digsig_builtin_and_secondary(struct key *dest_keyring,
 118                                                   const struct key_type *type,
 119                                                   const union key_payload *payload,
 120                                                   struct key *restrict_key)
 121 {
 122         /* If we have a secondary trusted keyring, then that contains a link
 123          * through to the builtin keyring and the search will follow that link.
 124          */
 125         if (type == &key_type_keyring &&
 126             dest_keyring == secondary_trusted_keys &&
 127             payload == &builtin_trusted_keys->payload)
 128                 /* Allow the builtin keyring to be added to the secondary */
 129                 return 0;
 130
 131         return restrict_link_by_digsig(dest_keyring, type, payload,
 132                                        secondary_trusted_keys);
 133 }
 134
 135 /*
 136  * Allocate a struct key_restriction for the "builtin and secondary trust"
 137  * keyring. Only for use in system_trusted_keyring_init().
 138  */
 139 static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
 140 {
 141         struct key_restriction *restriction;
 142
 143         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
 144
 145         if (!restriction)
 146                 panic("Can't allocate secondary trusted keyring restriction\n");
 147
 148         if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING))
 149                 restriction->check = restrict_link_by_builtin_secondary_and_machine;
 150         else
 151                 restriction->check = restrict_link_by_builtin_and_secondary_trusted;
 152
 153         return restriction;
 154 }
 155 #endif
 156 #ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
 157 void __init set_machine_trusted_keys(struct key *keyring)
 158 {
 159         machine_trusted_keys = keyring;
 160
 161         if (key_link(secondary_trusted_keys, machine_trusted_keys) < 0)
 162                 panic("Can't link (machine) trusted keyrings\n");
 163 }
 164
 165 /**
 166  * restrict_link_by_builtin_secondary_and_machine - Restrict keyring addition.
 167  * @dest_keyring: Keyring being linked to.
 168  * @type: The type of key being added.
 169  * @payload: The payload of the new key.
 170  * @restrict_key: A ring of keys that can be used to vouch for the new cert.
 171  *
 172  * Restrict the addition of keys into a keyring based on the key-to-be-added
 173  * being vouched for by a key in either the built-in, the secondary, or
 174  * the machine keyrings.
 175  */
 176 int restrict_link_by_builtin_secondary_and_machine(
 177         struct key *dest_keyring,
 178         const struct key_type *type,
 179         const union key_payload *payload,
 180         struct key *restrict_key)
 181 {
 182         if (machine_trusted_keys && type == &key_type_keyring &&
 183             dest_keyring == secondary_trusted_keys &&
 184             payload == &machine_trusted_keys->payload)
 185                 /* Allow the machine keyring to be added to the secondary */
 186                 return 0;
 187
 188         return restrict_link_by_builtin_and_secondary_trusted(dest_keyring, type,
 189                                                               payload, restrict_key);
 190 }
 191 #endif
 192
 193 /*
 194  * Create the trusted keyrings
 195  */
 196 static __init int system_trusted_keyring_init(void)
 197 {
 198         pr_notice("Initialise system trusted keyrings\n");
 199
 200         builtin_trusted_keys =
 201                 keyring_alloc(".builtin_trusted_keys",
 202                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 203                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 204                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 205                               KEY_ALLOC_NOT_IN_QUOTA,
 206                               NULL, NULL);
 207         if (IS_ERR(builtin_trusted_keys))
 208                 panic("Can't allocate builtin trusted keyring\n");
 209
 210 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 211         secondary_trusted_keys =
 212                 keyring_alloc(".secondary_trusted_keys",
 213                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 214                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 215                                KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
 216                                KEY_USR_WRITE),
 217                               KEY_ALLOC_NOT_IN_QUOTA,
 218                               get_builtin_and_secondary_restriction(),
 219                               NULL);
 220         if (IS_ERR(secondary_trusted_keys))
 221                 panic("Can't allocate secondary trusted keyring\n");
 222
 223         if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 224                 panic("Can't link trusted keyrings\n");
 225 #endif
 226
 227         return 0;
 228 }
 229
 230 /*
 231  * Must be initialised before we try and load the keys into the keyring.
 232  */
 233 device_initcall(system_trusted_keyring_init);
 234
 235 __init int load_module_cert(struct key *keyring)
 236 {
 237         if (!IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG))
 238                 return 0;
 239
 240         pr_notice("Loading compiled-in module X.509 certificates\n");
 241
 242         return x509_load_certificate_list(system_certificate_list,
 243                                           module_cert_size, keyring);
 244 }
 245
 246 /*
 247  * Load the compiled-in list of X.509 certificates.
 248  */
 249 static __init int load_system_certificate_list(void)
 250 {
 251         const u8 *p;
 252         unsigned long size;
 253
 254         pr_notice("Loading compiled-in X.509 certificates\n");
 255
 256 #ifdef CONFIG_MODULE_SIG
 257         p = system_certificate_list;
 258         size = system_certificate_list_size;
 259 #else
 260         p = system_certificate_list + module_cert_size;
 261         size = system_certificate_list_size - module_cert_size;
 262 #endif
 263
 264         return x509_load_certificate_list(p, size, builtin_trusted_keys);
 265 }
 266 late_initcall(load_system_certificate_list);
 267
 268 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 269
 270 /**
 271  * verify_pkcs7_message_sig - 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  * @pkcs7: The PKCS#7 message that is the signature.
 275  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 276  *                                      (void *)1UL for all trusted keys).
 277  * @usage: The use to which the key is being put.
 278  * @view_content: Callback to gain access to content.
 279  * @ctx: Context for callback.
 280  */
 281 int verify_pkcs7_message_sig(const void *data, size_t len,
 282                              struct pkcs7_message *pkcs7,
 283                              struct key *trusted_keys,
 284                              enum key_being_used_for usage,
 285                              int (*view_content)(void *ctx,
 286                                                  const void *data, size_t len,
 287                                                  size_t asn1hdrlen),
 288                              void *ctx)
 289 {
 290         int ret;
 291
 292         /* The data should be detached - so we need to supply it. */
 293         if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 294                 pr_err("PKCS#7 signature with non-detached data\n");
 295                 ret = -EBADMSG;
 296                 goto error;
 297         }
 298
 299         ret = pkcs7_verify(pkcs7, usage);
 300         if (ret < 0)
 301                 goto error;
 302
 303         if (!trusted_keys) {
 304                 trusted_keys = builtin_trusted_keys;
 305         } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
 306 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 307                 trusted_keys = secondary_trusted_keys;
 308 #else
 309                 trusted_keys = builtin_trusted_keys;
 310 #endif
 311         } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
 312 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 313                 trusted_keys = platform_trusted_keys;
 314 #else
 315                 trusted_keys = NULL;
 316 #endif
 317                 if (!trusted_keys) {
 318                         ret = -ENOKEY;
 319                         pr_devel("PKCS#7 platform keyring is not available\n");
 320                         goto error;
 321                 }
 322
 323                 ret = is_key_on_revocation_list(pkcs7);
 324                 if (ret != -ENOKEY) {
 325                         pr_devel("PKCS#7 platform key is on revocation list\n");
 326                         goto error;
 327                 }
 328         }
 329         ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 330         if (ret < 0) {
 331                 if (ret == -ENOKEY)
 332                         pr_devel("PKCS#7 signature not signed with a trusted key\n");
 333                 goto error;
 334         }
 335
 336         if (view_content) {
 337                 size_t asn1hdrlen;
 338
 339                 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 340                 if (ret < 0) {
 341                         if (ret == -ENODATA)
 342                                 pr_devel("PKCS#7 message does not contain data\n");
 343                         goto error;
 344                 }
 345
 346                 ret = view_content(ctx, data, len, asn1hdrlen);
 347         }
 348
 349 error:
 350         pr_devel("<==%s() = %d\n", __func__, ret);
 351         return ret;
 352 }
 353
 354 /**
 355  * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 356  * @data: The data to be verified (NULL if expecting internal data).
 357  * @len: Size of @data.
 358  * @raw_pkcs7: The PKCS#7 message that is the signature.
 359  * @pkcs7_len: The size of @raw_pkcs7.
 360  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 361  *                                      (void *)1UL for all trusted keys).
 362  * @usage: The use to which the key is being put.
 363  * @view_content: Callback to gain access to content.
 364  * @ctx: Context for callback.
 365  */
 366 int verify_pkcs7_signature(const void *data, size_t len,
 367                            const void *raw_pkcs7, size_t pkcs7_len,
 368                            struct key *trusted_keys,
 369                            enum key_being_used_for usage,
 370                            int (*view_content)(void *ctx,
 371                                                const void *data, size_t len,
 372                                                size_t asn1hdrlen),
 373                            void *ctx)
 374 {
 375         struct pkcs7_message *pkcs7;
 376         int ret;
 377
 378         pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 379         if (IS_ERR(pkcs7))
 380                 return PTR_ERR(pkcs7);
 381
 382         ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
 383                                        view_content, ctx);
 384
 385         pkcs7_free_message(pkcs7);
 386         pr_devel("<==%s() = %d\n", __func__, ret);
 387         return ret;
 388 }
 389 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 390
 391 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 392
 393 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 394 void __init set_platform_trusted_keys(struct key *keyring)
 395 {
 396         platform_trusted_keys = keyring;
 397 }
 398 #endif