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