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_PLATFORM_KEYRING
  26 static struct key *platform_trusted_keys;
  27 #endif
  28
  29 extern __initconst const u8 system_certificate_list[];
  30 extern __initconst const unsigned long system_certificate_list_size;
  31 extern __initconst const unsigned long module_cert_size;
  32
  33 /**
  34  * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
  35  *
  36  * Restrict the addition of keys into a keyring based on the key-to-be-added
  37  * being vouched for by a key in the built in system keyring.
  38  */
  39 int restrict_link_by_builtin_trusted(struct key *dest_keyring,
  40                                      const struct key_type *type,
  41                                      const union key_payload *payload,
  42                                      struct key *restriction_key)
  43 {
  44         return restrict_link_by_signature(dest_keyring, type, payload,
  45                                           builtin_trusted_keys);
  46 }
  47
  48 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  49 /**
  50  * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  51  *   addition by both builtin and secondary keyrings
  52  *
  53  * Restrict the addition of keys into a keyring based on the key-to-be-added
  54  * being vouched for by a key in either the built-in or the secondary system
  55  * keyrings.
  56  */
  57 int restrict_link_by_builtin_and_secondary_trusted(
  58         struct key *dest_keyring,
  59         const struct key_type *type,
  60         const union key_payload *payload,
  61         struct key *restrict_key)
  62 {
  63         /* If we have a secondary trusted keyring, then that contains a link
  64          * through to the builtin keyring and the search will follow that link.
  65          */
  66         if (type == &key_type_keyring &&
  67             dest_keyring == secondary_trusted_keys &&
  68             payload == &builtin_trusted_keys->payload)
  69                 /* Allow the builtin keyring to be added to the secondary */
  70                 return 0;
  71
  72         return restrict_link_by_signature(dest_keyring, type, payload,
  73                                           secondary_trusted_keys);
  74 }
  75
  76 /**
  77  * Allocate a struct key_restriction for the "builtin and secondary trust"
  78  * keyring. Only for use in system_trusted_keyring_init().
  79  */
  80 static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
  81 {
  82         struct key_restriction *restriction;
  83
  84         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
  85
  86         if (!restriction)
  87                 panic("Can't allocate secondary trusted keyring restriction\n");
  88
  89         restriction->check = restrict_link_by_builtin_and_secondary_trusted;
  90
  91         return restriction;
  92 }
  93 #endif
  94
  95 /*
  96  * Create the trusted keyrings
  97  */
  98 static __init int system_trusted_keyring_init(void)
  99 {
 100         pr_notice("Initialise system trusted keyrings\n");
 101
 102         builtin_trusted_keys =
 103                 keyring_alloc(".builtin_trusted_keys",
 104                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 105                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 106                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 107                               KEY_ALLOC_NOT_IN_QUOTA,
 108                               NULL, NULL);
 109         if (IS_ERR(builtin_trusted_keys))
 110                 panic("Can't allocate builtin trusted keyring\n");
 111
 112 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 113         secondary_trusted_keys =
 114                 keyring_alloc(".secondary_trusted_keys",
 115                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 116                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 117                                KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
 118                                KEY_USR_WRITE),
 119                               KEY_ALLOC_NOT_IN_QUOTA,
 120                               get_builtin_and_secondary_restriction(),
 121                               NULL);
 122         if (IS_ERR(secondary_trusted_keys))
 123                 panic("Can't allocate secondary trusted keyring\n");
 124
 125         if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 126                 panic("Can't link trusted keyrings\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 __init int load_module_cert(struct key *keyring)
 138 {
 139         if (!IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG))
 140                 return 0;
 141
 142         pr_notice("Loading compiled-in module X.509 certificates\n");
 143
 144         return load_certificate_list(system_certificate_list, module_cert_size, keyring);
 145 }
 146
 147 /*
 148  * Load the compiled-in list of X.509 certificates.
 149  */
 150 static __init int load_system_certificate_list(void)
 151 {
 152         const u8 *p;
 153         unsigned long size;
 154
 155         pr_notice("Loading compiled-in X.509 certificates\n");
 156
 157 #ifdef CONFIG_MODULE_SIG
 158         p = system_certificate_list;
 159         size = system_certificate_list_size;
 160 #else
 161         p = system_certificate_list + module_cert_size;
 162         size = system_certificate_list_size - module_cert_size;
 163 #endif
 164
 165         return load_certificate_list(p, size, builtin_trusted_keys);
 166 }
 167 late_initcall(load_system_certificate_list);
 168
 169 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 170
 171 /**
 172  * verify_pkcs7_message_sig - Verify a PKCS#7-based signature on system data.
 173  * @data: The data to be verified (NULL if expecting internal data).
 174  * @len: Size of @data.
 175  * @pkcs7: The PKCS#7 message that is the signature.
 176  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 177  *                                      (void *)1UL for all trusted keys).
 178  * @usage: The use to which the key is being put.
 179  * @view_content: Callback to gain access to content.
 180  * @ctx: Context for callback.
 181  */
 182 int verify_pkcs7_message_sig(const void *data, size_t len,
 183                              struct pkcs7_message *pkcs7,
 184                              struct key *trusted_keys,
 185                              enum key_being_used_for usage,
 186                              int (*view_content)(void *ctx,
 187                                                  const void *data, size_t len,
 188                                                  size_t asn1hdrlen),
 189                              void *ctx)
 190 {
 191         int ret;
 192
 193         /* The data should be detached - so we need to supply it. */
 194         if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 195                 pr_err("PKCS#7 signature with non-detached data\n");
 196                 ret = -EBADMSG;
 197                 goto error;
 198         }
 199
 200         ret = pkcs7_verify(pkcs7, usage);
 201         if (ret < 0)
 202                 goto error;
 203
 204         if (!trusted_keys) {
 205                 trusted_keys = builtin_trusted_keys;
 206         } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
 207 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 208                 trusted_keys = secondary_trusted_keys;
 209 #else
 210                 trusted_keys = builtin_trusted_keys;
 211 #endif
 212         } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
 213 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 214                 trusted_keys = platform_trusted_keys;
 215 #else
 216                 trusted_keys = NULL;
 217 #endif
 218                 if (!trusted_keys) {
 219                         ret = -ENOKEY;
 220                         pr_devel("PKCS#7 platform keyring is not available\n");
 221                         goto error;
 222                 }
 223
 224                 ret = is_key_on_revocation_list(pkcs7);
 225                 if (ret != -ENOKEY) {
 226                         pr_devel("PKCS#7 platform key is on revocation list\n");
 227                         goto error;
 228                 }
 229         }
 230         ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 231         if (ret < 0) {
 232                 if (ret == -ENOKEY)
 233                         pr_devel("PKCS#7 signature not signed with a trusted key\n");
 234                 goto error;
 235         }
 236
 237         if (view_content) {
 238                 size_t asn1hdrlen;
 239
 240                 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 241                 if (ret < 0) {
 242                         if (ret == -ENODATA)
 243                                 pr_devel("PKCS#7 message does not contain data\n");
 244                         goto error;
 245                 }
 246
 247                 ret = view_content(ctx, data, len, asn1hdrlen);
 248         }
 249
 250 error:
 251         pr_devel("<==%s() = %d\n", __func__, ret);
 252         return ret;
 253 }
 254
 255 /**
 256  * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 257  * @data: The data to be verified (NULL if expecting internal data).
 258  * @len: Size of @data.
 259  * @raw_pkcs7: The PKCS#7 message that is the signature.
 260  * @pkcs7_len: The size of @raw_pkcs7.
 261  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 262  *                                      (void *)1UL for all trusted keys).
 263  * @usage: The use to which the key is being put.
 264  * @view_content: Callback to gain access to content.
 265  * @ctx: Context for callback.
 266  */
 267 int verify_pkcs7_signature(const void *data, size_t len,
 268                            const void *raw_pkcs7, size_t pkcs7_len,
 269                            struct key *trusted_keys,
 270                            enum key_being_used_for usage,
 271                            int (*view_content)(void *ctx,
 272                                                const void *data, size_t len,
 273                                                size_t asn1hdrlen),
 274                            void *ctx)
 275 {
 276         struct pkcs7_message *pkcs7;
 277         int ret;
 278
 279         pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 280         if (IS_ERR(pkcs7))
 281                 return PTR_ERR(pkcs7);
 282
 283         ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
 284                                        view_content, ctx);
 285
 286         pkcs7_free_message(pkcs7);
 287         pr_devel("<==%s() = %d\n", __func__, ret);
 288         return ret;
 289 }
 290 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 291
 292 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 293
 294 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 295 void __init set_platform_trusted_keys(struct key *keyring)
 296 {
 297         platform_trusted_keys = keyring;
 298 }
 299 #endif