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 #include "common.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_INTEGRITY_MACHINE_KEYRING
  26 static struct key *machine_trusted_keys;
  27 #endif
  28 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
  29 static struct key *platform_trusted_keys;
  30 #endif
  31
  32 extern __initconst const u8 system_certificate_list[];
  33 extern __initconst const unsigned long system_certificate_list_size;
  34 extern __initconst const unsigned long module_cert_size;
  35
  36 /**
  37  * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
  38  *
  39  * Restrict the addition of keys into a keyring based on the key-to-be-added
  40  * being vouched for by a key in the built in system keyring.
  41  */
  42 int restrict_link_by_builtin_trusted(struct key *dest_keyring,
  43                                      const struct key_type *type,
  44                                      const union key_payload *payload,
  45                                      struct key *restriction_key)
  46 {
  47         return restrict_link_by_signature(dest_keyring, type, payload,
  48                                           builtin_trusted_keys);
  49 }
  50
  51 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  52 /**
  53  * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  54  *   addition by both builtin and secondary keyrings
  55  *
  56  * Restrict the addition of keys into a keyring based on the key-to-be-added
  57  * being vouched for by a key in either the built-in or the secondary system
  58  * keyrings.
  59  */
  60 int restrict_link_by_builtin_and_secondary_trusted(
  61         struct key *dest_keyring,
  62         const struct key_type *type,
  63         const union key_payload *payload,
  64         struct key *restrict_key)
  65 {
  66         /* If we have a secondary trusted keyring, then that contains a link
  67          * through to the builtin keyring and the search will follow that link.
  68          */
  69         if (type == &key_type_keyring &&
  70             dest_keyring == secondary_trusted_keys &&
  71             payload == &builtin_trusted_keys->payload)
  72                 /* Allow the builtin keyring to be added to the secondary */
  73                 return 0;
  74
  75         return restrict_link_by_signature(dest_keyring, type, payload,
  76                                           secondary_trusted_keys);
  77 }
  78
  79 /**
  80  * Allocate a struct key_restriction for the "builtin and secondary trust"
  81  * keyring. Only for use in system_trusted_keyring_init().
  82  */
  83 static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
  84 {
  85         struct key_restriction *restriction;
  86
  87         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
  88
  89         if (!restriction)
  90                 panic("Can't allocate secondary trusted keyring restriction\n");
  91
  92         if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING))
  93                 restriction->check = restrict_link_by_builtin_secondary_and_machine;
  94         else
  95                 restriction->check = restrict_link_by_builtin_and_secondary_trusted;
  96
  97         return restriction;
  98 }
  99 #endif
 100 #ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
 101 void __init set_machine_trusted_keys(struct key *keyring)
 102 {
 103         machine_trusted_keys = keyring;
 104
 105         if (key_link(secondary_trusted_keys, machine_trusted_keys) < 0)
 106                 panic("Can't link (machine) trusted keyrings\n");
 107 }
 108
 109 /**
 110  * restrict_link_by_builtin_secondary_and_machine - Restrict keyring addition.
 111  * @dest_keyring: Keyring being linked to.
 112  * @type: The type of key being added.
 113  * @payload: The payload of the new key.
 114  * @restrict_key: A ring of keys that can be used to vouch for the new cert.
 115  *
 116  * Restrict the addition of keys into a keyring based on the key-to-be-added
 117  * being vouched for by a key in either the built-in, the secondary, or
 118  * the machine keyrings.
 119  */
 120 int restrict_link_by_builtin_secondary_and_machine(
 121         struct key *dest_keyring,
 122         const struct key_type *type,
 123         const union key_payload *payload,
 124         struct key *restrict_key)
 125 {
 126         if (machine_trusted_keys && type == &key_type_keyring &&
 127             dest_keyring == secondary_trusted_keys &&
 128             payload == &machine_trusted_keys->payload)
 129                 /* Allow the machine keyring to be added to the secondary */
 130                 return 0;
 131
 132         return restrict_link_by_builtin_and_secondary_trusted(dest_keyring, type,
 133                                                               payload, restrict_key);
 134 }
 135 #endif
 136
 137 /*
 138  * Create the trusted keyrings
 139  */
 140 static __init int system_trusted_keyring_init(void)
 141 {
 142         pr_notice("Initialise system trusted keyrings\n");
 143
 144         builtin_trusted_keys =
 145                 keyring_alloc(".builtin_trusted_keys",
 146                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 147                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 148                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 149                               KEY_ALLOC_NOT_IN_QUOTA,
 150                               NULL, NULL);
 151         if (IS_ERR(builtin_trusted_keys))
 152                 panic("Can't allocate builtin trusted keyring\n");
 153
 154 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 155         secondary_trusted_keys =
 156                 keyring_alloc(".secondary_trusted_keys",
 157                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 158                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 159                                KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
 160                                KEY_USR_WRITE),
 161                               KEY_ALLOC_NOT_IN_QUOTA,
 162                               get_builtin_and_secondary_restriction(),
 163                               NULL);
 164         if (IS_ERR(secondary_trusted_keys))
 165                 panic("Can't allocate secondary trusted keyring\n");
 166
 167         if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 168                 panic("Can't link trusted keyrings\n");
 169 #endif
 170
 171         return 0;
 172 }
 173
 174 /*
 175  * Must be initialised before we try and load the keys into the keyring.
 176  */
 177 device_initcall(system_trusted_keyring_init);
 178
 179 __init int load_module_cert(struct key *keyring)
 180 {
 181         if (!IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG))
 182                 return 0;
 183
 184         pr_notice("Loading compiled-in module X.509 certificates\n");
 185
 186         return load_certificate_list(system_certificate_list, 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 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