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
  32 /**
  33  * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
  34  *
  35  * Restrict the addition of keys into a keyring based on the key-to-be-added
  36  * being vouched for by a key in the built in system keyring.
  37  */
  38 int restrict_link_by_builtin_trusted(struct key *dest_keyring,
  39                                      const struct key_type *type,
  40                                      const union key_payload *payload,
  41                                      struct key *restriction_key)
  42 {
  43         return restrict_link_by_signature(dest_keyring, type, payload,
  44                                           builtin_trusted_keys);
  45 }
  46
  47 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  48 /**
  49  * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  50  *   addition by both builtin and secondary keyrings
  51  *
  52  * Restrict the addition of keys into a keyring based on the key-to-be-added
  53  * being vouched for by a key in either the built-in or the secondary system
  54  * keyrings.
  55  */
  56 int restrict_link_by_builtin_and_secondary_trusted(
  57         struct key *dest_keyring,
  58         const struct key_type *type,
  59         const union key_payload *payload,
  60         struct key *restrict_key)
  61 {
  62         /* If we have a secondary trusted keyring, then that contains a link
  63          * through to the builtin keyring and the search will follow that link.
  64          */
  65         if (type == &key_type_keyring &&
  66             dest_keyring == secondary_trusted_keys &&
  67             payload == &builtin_trusted_keys->payload)
  68                 /* Allow the builtin keyring to be added to the secondary */
  69                 return 0;
  70
  71         return restrict_link_by_signature(dest_keyring, type, payload,
  72                                           secondary_trusted_keys);
  73 }
  74
  75 /**
  76  * Allocate a struct key_restriction for the "builtin and secondary trust"
  77  * keyring. Only for use in system_trusted_keyring_init().
  78  */
  79 static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
  80 {
  81         struct key_restriction *restriction;
  82
  83         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
  84
  85         if (!restriction)
  86                 panic("Can't allocate secondary trusted keyring restriction\n");
  87
  88         restriction->check = restrict_link_by_builtin_and_secondary_trusted;
  89
  90         return restriction;
  91 }
  92 #endif
  93
  94 /*
  95  * Create the trusted keyrings
  96  */
  97 static __init int system_trusted_keyring_init(void)
  98 {
  99         pr_notice("Initialise system trusted keyrings\n");
 100
 101         builtin_trusted_keys =
 102                 keyring_alloc(".builtin_trusted_keys",
 103                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 104                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 105                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 106                               KEY_ALLOC_NOT_IN_QUOTA,
 107                               NULL, NULL);
 108         if (IS_ERR(builtin_trusted_keys))
 109                 panic("Can't allocate builtin trusted keyring\n");
 110
 111 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 112         secondary_trusted_keys =
 113                 keyring_alloc(".secondary_trusted_keys",
 114                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 115                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 116                                KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
 117                                KEY_USR_WRITE),
 118                               KEY_ALLOC_NOT_IN_QUOTA,
 119                               get_builtin_and_secondary_restriction(),
 120                               NULL);
 121         if (IS_ERR(secondary_trusted_keys))
 122                 panic("Can't allocate secondary trusted keyring\n");
 123
 124         if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 125                 panic("Can't link trusted keyrings\n");
 126 #endif
 127
 128         return 0;
 129 }
 130
 131 /*
 132  * Must be initialised before we try and load the keys into the keyring.
 133  */
 134 device_initcall(system_trusted_keyring_init);
 135
 136 /*
 137  * Load the compiled-in list of X.509 certificates.
 138  */
 139 static __init int load_system_certificate_list(void)
 140 {
 141         pr_notice("Loading compiled-in X.509 certificates\n");
 142
 143         return load_certificate_list(system_certificate_list, system_certificate_list_size,
 144                                      builtin_trusted_keys);
 145 }
 146 late_initcall(load_system_certificate_list);
 147
 148 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 149
 150 /**
 151  * verify_pkcs7_message_sig - Verify a PKCS#7-based signature on system data.
 152  * @data: The data to be verified (NULL if expecting internal data).
 153  * @len: Size of @data.
 154  * @pkcs7: The PKCS#7 message that is the signature.
 155  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 156  *                                      (void *)1UL for all trusted keys).
 157  * @usage: The use to which the key is being put.
 158  * @view_content: Callback to gain access to content.
 159  * @ctx: Context for callback.
 160  */
 161 int verify_pkcs7_message_sig(const void *data, size_t len,
 162                              struct pkcs7_message *pkcs7,
 163                              struct key *trusted_keys,
 164                              enum key_being_used_for usage,
 165                              int (*view_content)(void *ctx,
 166                                                  const void *data, size_t len,
 167                                                  size_t asn1hdrlen),
 168                              void *ctx)
 169 {
 170         int ret;
 171
 172         /* The data should be detached - so we need to supply it. */
 173         if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 174                 pr_err("PKCS#7 signature with non-detached data\n");
 175                 ret = -EBADMSG;
 176                 goto error;
 177         }
 178
 179         ret = pkcs7_verify(pkcs7, usage);
 180         if (ret < 0)
 181                 goto error;
 182
 183         if (!trusted_keys) {
 184                 trusted_keys = builtin_trusted_keys;
 185         } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
 186 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 187                 trusted_keys = secondary_trusted_keys;
 188 #else
 189                 trusted_keys = builtin_trusted_keys;
 190 #endif
 191         } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
 192 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 193                 trusted_keys = platform_trusted_keys;
 194 #else
 195                 trusted_keys = NULL;
 196 #endif
 197                 if (!trusted_keys) {
 198                         ret = -ENOKEY;
 199                         pr_devel("PKCS#7 platform keyring is not available\n");
 200                         goto error;
 201                 }
 202
 203                 ret = is_key_on_revocation_list(pkcs7);
 204                 if (ret != -ENOKEY) {
 205                         pr_devel("PKCS#7 platform key is on revocation list\n");
 206                         goto error;
 207                 }
 208         }
 209         ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 210         if (ret < 0) {
 211                 if (ret == -ENOKEY)
 212                         pr_devel("PKCS#7 signature not signed with a trusted key\n");
 213                 goto error;
 214         }
 215
 216         if (view_content) {
 217                 size_t asn1hdrlen;
 218
 219                 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 220                 if (ret < 0) {
 221                         if (ret == -ENODATA)
 222                                 pr_devel("PKCS#7 message does not contain data\n");
 223                         goto error;
 224                 }
 225
 226                 ret = view_content(ctx, data, len, asn1hdrlen);
 227         }
 228
 229 error:
 230         pr_devel("<==%s() = %d\n", __func__, ret);
 231         return ret;
 232 }
 233
 234 /**
 235  * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 236  * @data: The data to be verified (NULL if expecting internal data).
 237  * @len: Size of @data.
 238  * @raw_pkcs7: The PKCS#7 message that is the signature.
 239  * @pkcs7_len: The size of @raw_pkcs7.
 240  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 241  *                                      (void *)1UL for all trusted keys).
 242  * @usage: The use to which the key is being put.
 243  * @view_content: Callback to gain access to content.
 244  * @ctx: Context for callback.
 245  */
 246 int verify_pkcs7_signature(const void *data, size_t len,
 247                            const void *raw_pkcs7, size_t pkcs7_len,
 248                            struct key *trusted_keys,
 249                            enum key_being_used_for usage,
 250                            int (*view_content)(void *ctx,
 251                                                const void *data, size_t len,
 252                                                size_t asn1hdrlen),
 253                            void *ctx)
 254 {
 255         struct pkcs7_message *pkcs7;
 256         int ret;
 257
 258         pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 259         if (IS_ERR(pkcs7))
 260                 return PTR_ERR(pkcs7);
 261
 262         ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
 263                                        view_content, ctx);
 264
 265         pkcs7_free_message(pkcs7);
 266         pr_devel("<==%s() = %d\n", __func__, ret);
 267         return ret;
 268 }
 269 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 270
 271 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 272
 273 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 274 void __init set_platform_trusted_keys(struct key *keyring)
 275 {
 276         platform_trusted_keys = keyring;
 277 }
 278 #endif