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 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  55 /**
  56  * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  57  *   addition by both built-in and secondary keyrings.
  58  * @dest_keyring: Keyring being linked to.
  59  * @type: The type of key being added.
  60  * @payload: The payload of the new key.
  61  * @restrict_key: A ring of keys that can be used to vouch for the new cert.
  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 *dest_keyring,
  69         const struct key_type *type,
  70         const union key_payload *payload,
  71         struct key *restrict_key)
  72 {
  73         /* If we have a secondary trusted keyring, then that contains a link
  74          * through to the builtin keyring and the search will follow that link.
  75          */
  76         if (type == &key_type_keyring &&
  77             dest_keyring == secondary_trusted_keys &&
  78             payload == &builtin_trusted_keys->payload)
  79                 /* Allow the builtin keyring to be added to the secondary */
  80                 return 0;
  81
  82         return restrict_link_by_signature(dest_keyring, type, payload,
  83                                           secondary_trusted_keys);
  84 }
  85
  86 /*
  87  * Allocate a struct key_restriction for the "builtin and secondary trust"
  88  * keyring. Only for use in system_trusted_keyring_init().
  89  */
  90 static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
  91 {
  92         struct key_restriction *restriction;
  93
  94         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
  95
  96         if (!restriction)
  97                 panic("Can't allocate secondary trusted keyring restriction\n");
  98
  99         if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING))
 100                 restriction->check = restrict_link_by_builtin_secondary_and_machine;
 101         else
 102                 restriction->check = restrict_link_by_builtin_and_secondary_trusted;
 103
 104         return restriction;
 105 }
 106 #endif
 107 #ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
 108 void __init set_machine_trusted_keys(struct key *keyring)
 109 {
 110         machine_trusted_keys = keyring;
 111
 112         if (key_link(secondary_trusted_keys, machine_trusted_keys) < 0)
 113                 panic("Can't link (machine) trusted keyrings\n");
 114 }
 115
 116 /**
 117  * restrict_link_by_builtin_secondary_and_machine - Restrict keyring addition.
 118  * @dest_keyring: Keyring being linked to.
 119  * @type: The type of key being added.
 120  * @payload: The payload of the new key.
 121  * @restrict_key: A ring of keys that can be used to vouch for the new cert.
 122  *
 123  * Restrict the addition of keys into a keyring based on the key-to-be-added
 124  * being vouched for by a key in either the built-in, the secondary, or
 125  * the machine keyrings.
 126  */
 127 int restrict_link_by_builtin_secondary_and_machine(
 128         struct key *dest_keyring,
 129         const struct key_type *type,
 130         const union key_payload *payload,
 131         struct key *restrict_key)
 132 {
 133         if (machine_trusted_keys && type == &key_type_keyring &&
 134             dest_keyring == secondary_trusted_keys &&
 135             payload == &machine_trusted_keys->payload)
 136                 /* Allow the machine keyring to be added to the secondary */
 137                 return 0;
 138
 139         return restrict_link_by_builtin_and_secondary_trusted(dest_keyring, type,
 140                                                               payload, restrict_key);
 141 }
 142 #endif
 143
 144 /*
 145  * Create the trusted keyrings
 146  */
 147 static __init int system_trusted_keyring_init(void)
 148 {
 149         pr_notice("Initialise system trusted keyrings\n");
 150
 151         builtin_trusted_keys =
 152                 keyring_alloc(".builtin_trusted_keys",
 153                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 154                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 155                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 156                               KEY_ALLOC_NOT_IN_QUOTA,
 157                               NULL, NULL);
 158         if (IS_ERR(builtin_trusted_keys))
 159                 panic("Can't allocate builtin trusted keyring\n");
 160
 161 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 162         secondary_trusted_keys =
 163                 keyring_alloc(".secondary_trusted_keys",
 164                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 165                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 166                                KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
 167                                KEY_USR_WRITE),
 168                               KEY_ALLOC_NOT_IN_QUOTA,
 169                               get_builtin_and_secondary_restriction(),
 170                               NULL);
 171         if (IS_ERR(secondary_trusted_keys))
 172                 panic("Can't allocate secondary trusted keyring\n");
 173
 174         if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 175                 panic("Can't link trusted keyrings\n");
 176 #endif
 177
 178         return 0;
 179 }
 180
 181 /*
 182  * Must be initialised before we try and load the keys into the keyring.
 183  */
 184 device_initcall(system_trusted_keyring_init);
 185
 186 __init int load_module_cert(struct key *keyring)
 187 {
 188         if (!IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG))
 189                 return 0;
 190
 191         pr_notice("Loading compiled-in module X.509 certificates\n");
 192
 193         return x509_load_certificate_list(system_certificate_list,
 194                                           module_cert_size, keyring);
 195 }
 196
 197 /*
 198  * Load the compiled-in list of X.509 certificates.
 199  */
 200 static __init int load_system_certificate_list(void)
 201 {
 202         const u8 *p;
 203         unsigned long size;
 204
 205         pr_notice("Loading compiled-in X.509 certificates\n");
 206
 207 #ifdef CONFIG_MODULE_SIG
 208         p = system_certificate_list;
 209         size = system_certificate_list_size;
 210 #else
 211         p = system_certificate_list + module_cert_size;
 212         size = system_certificate_list_size - module_cert_size;
 213 #endif
 214
 215         return x509_load_certificate_list(p, size, builtin_trusted_keys);
 216 }
 217 late_initcall(load_system_certificate_list);
 218
 219 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 220
 221 /**
 222  * verify_pkcs7_message_sig - Verify a PKCS#7-based signature on system data.
 223  * @data: The data to be verified (NULL if expecting internal data).
 224  * @len: Size of @data.
 225  * @pkcs7: The PKCS#7 message that is the signature.
 226  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 227  *                                      (void *)1UL for all trusted keys).
 228  * @usage: The use to which the key is being put.
 229  * @view_content: Callback to gain access to content.
 230  * @ctx: Context for callback.
 231  */
 232 int verify_pkcs7_message_sig(const void *data, size_t len,
 233                              struct pkcs7_message *pkcs7,
 234                              struct key *trusted_keys,
 235                              enum key_being_used_for usage,
 236                              int (*view_content)(void *ctx,
 237                                                  const void *data, size_t len,
 238                                                  size_t asn1hdrlen),
 239                              void *ctx)
 240 {
 241         int ret;
 242
 243         /* The data should be detached - so we need to supply it. */
 244         if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 245                 pr_err("PKCS#7 signature with non-detached data\n");
 246                 ret = -EBADMSG;
 247                 goto error;
 248         }
 249
 250         ret = pkcs7_verify(pkcs7, usage);
 251         if (ret < 0)
 252                 goto error;
 253
 254         if (!trusted_keys) {
 255                 trusted_keys = builtin_trusted_keys;
 256         } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
 257 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 258                 trusted_keys = secondary_trusted_keys;
 259 #else
 260                 trusted_keys = builtin_trusted_keys;
 261 #endif
 262         } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
 263 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 264                 trusted_keys = platform_trusted_keys;
 265 #else
 266                 trusted_keys = NULL;
 267 #endif
 268                 if (!trusted_keys) {
 269                         ret = -ENOKEY;
 270                         pr_devel("PKCS#7 platform keyring is not available\n");
 271                         goto error;
 272                 }
 273
 274                 ret = is_key_on_revocation_list(pkcs7);
 275                 if (ret != -ENOKEY) {
 276                         pr_devel("PKCS#7 platform key is on revocation list\n");
 277                         goto error;
 278                 }
 279         }
 280         ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 281         if (ret < 0) {
 282                 if (ret == -ENOKEY)
 283                         pr_devel("PKCS#7 signature not signed with a trusted key\n");
 284                 goto error;
 285         }
 286
 287         if (view_content) {
 288                 size_t asn1hdrlen;
 289
 290                 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 291                 if (ret < 0) {
 292                         if (ret == -ENODATA)
 293                                 pr_devel("PKCS#7 message does not contain data\n");
 294                         goto error;
 295                 }
 296
 297                 ret = view_content(ctx, data, len, asn1hdrlen);
 298         }
 299
 300 error:
 301         pr_devel("<==%s() = %d\n", __func__, ret);
 302         return ret;
 303 }
 304
 305 /**
 306  * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 307  * @data: The data to be verified (NULL if expecting internal data).
 308  * @len: Size of @data.
 309  * @raw_pkcs7: The PKCS#7 message that is the signature.
 310  * @pkcs7_len: The size of @raw_pkcs7.
 311  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 312  *                                      (void *)1UL for all trusted keys).
 313  * @usage: The use to which the key is being put.
 314  * @view_content: Callback to gain access to content.
 315  * @ctx: Context for callback.
 316  */
 317 int verify_pkcs7_signature(const void *data, size_t len,
 318                            const void *raw_pkcs7, size_t pkcs7_len,
 319                            struct key *trusted_keys,
 320                            enum key_being_used_for usage,
 321                            int (*view_content)(void *ctx,
 322                                                const void *data, size_t len,
 323                                                size_t asn1hdrlen),
 324                            void *ctx)
 325 {
 326         struct pkcs7_message *pkcs7;
 327         int ret;
 328
 329         pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 330         if (IS_ERR(pkcs7))
 331                 return PTR_ERR(pkcs7);
 332
 333         ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
 334                                        view_content, ctx);
 335
 336         pkcs7_free_message(pkcs7);
 337         pr_devel("<==%s() = %d\n", __func__, ret);
 338         return ret;
 339 }
 340 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 341
 342 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 343
 344 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 345 void __init set_platform_trusted_keys(struct key *keyring)
 346 {
 347         platform_trusted_keys = keyring;
 348 }
 349 #endif