LXR linux/certs/system

   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/verification.h>
  15#include <keys/asymmetric-type.h>
  16#include <keys/system_keyring.h>
  17#include <crypto/pkcs7.h>
  18
  19static struct key *builtin_trusted_keys;
  20#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  21static struct key *secondary_trusted_keys;
  22#endif
  23#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
  24static struct key *platform_trusted_keys;
  25#endif
  26
  27extern __initconst const u8 system_certificate_list[];
  28extern __initconst const unsigned long system_certificate_list_size;
  29
  30/**
  31 * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
  32 *
  33 * Restrict the addition of keys into a keyring based on the key-to-be-added
  34 * being vouched for by a key in the built in system keyring.
  35 */
  36int restrict_link_by_builtin_trusted(struct key *dest_keyring,
  37                                     const struct key_type *type,
  38                                     const union key_payload *payload,
  39                                     struct key *restriction_key)
  40{
  41        return restrict_link_by_signature(dest_keyring, type, payload,
  42                                          builtin_trusted_keys);
  43}
  44
  45#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  46/**
  47 * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  48 *   addition by both builtin and secondary keyrings
  49 *
  50 * Restrict the addition of keys into a keyring based on the key-to-be-added
  51 * being vouched for by a key in either the built-in or the secondary system
  52 * keyrings.
  53 */
  54int restrict_link_by_builtin_and_secondary_trusted(
  55        struct key *dest_keyring,
  56        const struct key_type *type,
  57        const union key_payload *payload,
  58        struct key *restrict_key)
  59{
  60        /* If we have a secondary trusted keyring, then that contains a link
  61         * through to the builtin keyring and the search will follow that link.
  62         */
  63        if (type == &key_type_keyring &&
  64            dest_keyring == secondary_trusted_keys &&
  65            payload == &builtin_trusted_keys->payload)
  66                /* Allow the builtin keyring to be added to the secondary */
  67                return 0;
  68
  69        return restrict_link_by_signature(dest_keyring, type, payload,
  70                                          secondary_trusted_keys);
  71}
  72
  73/**
  74 * Allocate a struct key_restriction for the "builtin and secondary trust"
  75 * keyring. Only for use in system_trusted_keyring_init().
  76 */
  77static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
  78{
  79        struct key_restriction *restriction;
  80
  81        restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
  82
  83        if (!restriction)
  84                panic("Can't allocate secondary trusted keyring restriction\n");
  85
  86        restriction->check = restrict_link_by_builtin_and_secondary_trusted;
  87
  88        return restriction;
  89}
  90#endif
  91
  92/*
  93 * Create the trusted keyrings
  94 */
  95static __init int system_trusted_keyring_init(void)
  96{
  97        pr_notice("Initialise system trusted keyrings\n");
  98
  99        builtin_trusted_keys =
 100                keyring_alloc(".builtin_trusted_keys",
 101                              KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
 102                              ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 103                              KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 104                              KEY_ALLOC_NOT_IN_QUOTA,
 105                              NULL, NULL);
 106        if (IS_ERR(builtin_trusted_keys))
 107                panic("Can't allocate builtin trusted keyring\n");
 108
 109#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 110        secondary_trusted_keys =
 111                keyring_alloc(".secondary_trusted_keys",
 112                              KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
 113                              ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 114                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
 115                               KEY_USR_WRITE),
 116                              KEY_ALLOC_NOT_IN_QUOTA,
 117                              get_builtin_and_secondary_restriction(),
 118                              NULL);
 119        if (IS_ERR(secondary_trusted_keys))
 120                panic("Can't allocate secondary trusted keyring\n");
 121
 122        if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 123                panic("Can't link trusted keyrings\n");
 124#endif
 125
 126        return 0;
 127}
 128
 129/*
 130 * Must be initialised before we try and load the keys into the keyring.
 131 */
 132device_initcall(system_trusted_keyring_init);
 133
 134/*
 135 * Load the compiled-in list of X.509 certificates.
 136 */
 137static __init int load_system_certificate_list(void)
 138{
 139        key_ref_t key;
 140        const u8 *p, *end;
 141        size_t plen;
 142
 143        pr_notice("Loading compiled-in X.509 certificates\n");
 144
 145        p = system_certificate_list;
 146        end = p + system_certificate_list_size;
 147        while (p < end) {
 148                /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
 149                 * than 256 bytes in size.
 150                 */
 151                if (end - p < 4)
 152                        goto dodgy_cert;
 153                if (p[0] != 0x30 &&
 154                    p[1] != 0x82)
 155                        goto dodgy_cert;
 156                plen = (p[2] << 8) | p[3];
 157                plen += 4;
 158                if (plen > end - p)
 159                        goto dodgy_cert;
 160
 161                key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
 162                                           "asymmetric",
 163                                           NULL,
 164                                           p,
 165                                           plen,
 166                                           ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 167                                           KEY_USR_VIEW | KEY_USR_READ),
 168                                           KEY_ALLOC_NOT_IN_QUOTA |
 169                                           KEY_ALLOC_BUILT_IN |
 170                                           KEY_ALLOC_BYPASS_RESTRICTION);
 171                if (IS_ERR(key)) {
 172                        pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 173                               PTR_ERR(key));
 174                } else {
 175                        pr_notice("Loaded X.509 cert '%s'\n",
 176                                  key_ref_to_ptr(key)->description);
 177                        key_ref_put(key);
 178                }
 179                p += plen;
 180        }
 181
 182        return 0;
 183
 184dodgy_cert:
 185        pr_err("Problem parsing in-kernel X.509 certificate list\n");
 186        return 0;
 187}
 188late_initcall(load_system_certificate_list);
 189
 190#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 191
 192/**
 193 * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 194 * @data: The data to be verified (NULL if expecting internal data).
 195 * @len: Size of @data.
 196 * @raw_pkcs7: The PKCS#7 message that is the signature.
 197 * @pkcs7_len: The size of @raw_pkcs7.
 198 * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 199 *                                      (void *)1UL for all trusted keys).
 200 * @usage: The use to which the key is being put.
 201 * @view_content: Callback to gain access to content.
 202 * @ctx: Context for callback.
 203 */
 204int verify_pkcs7_signature(const void *data, size_t len,
 205                           const void *raw_pkcs7, size_t pkcs7_len,
 206                           struct key *trusted_keys,
 207                           enum key_being_used_for usage,
 208                           int (*view_content)(void *ctx,
 209                                               const void *data, size_t len,
 210                                               size_t asn1hdrlen),
 211                           void *ctx)
 212{
 213        struct pkcs7_message *pkcs7;
 214        int ret;
 215
 216        pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 217        if (IS_ERR(pkcs7))
 218                return PTR_ERR(pkcs7);
 219
 220        /* The data should be detached - so we need to supply it. */
 221        if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 222                pr_err("PKCS#7 signature with non-detached data\n");
 223                ret = -EBADMSG;
 224                goto error;
 225        }
 226
 227        ret = pkcs7_verify(pkcs7, usage);
 228        if (ret < 0)
 229                goto error;
 230
 231        if (!trusted_keys) {
 232                trusted_keys = builtin_trusted_keys;
 233        } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
 234#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 235                trusted_keys = secondary_trusted_keys;
 236#else
 237                trusted_keys = builtin_trusted_keys;
 238#endif
 239        } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
 240#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 241                trusted_keys = platform_trusted_keys;
 242#else
 243                trusted_keys = NULL;
 244#endif
 245                if (!trusted_keys) {
 246                        ret = -ENOKEY;
 247                        pr_devel("PKCS#7 platform keyring is not available\n");
 248                        goto error;
 249                }
 250        }
 251        ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 252        if (ret < 0) {
 253                if (ret == -ENOKEY)
 254                        pr_devel("PKCS#7 signature not signed with a trusted key\n");
 255                goto error;
 256        }
 257
 258        if (view_content) {
 259                size_t asn1hdrlen;
 260
 261                ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 262                if (ret < 0) {
 263                        if (ret == -ENODATA)
 264                                pr_devel("PKCS#7 message does not contain data\n");
 265                        goto error;
 266                }
 267
 268                ret = view_content(ctx, data, len, asn1hdrlen);
 269        }
 270
 271error:
 272        pkcs7_free_message(pkcs7);
 273        pr_devel("<==%s() = %d\n", __func__, ret);
 274        return ret;
 275}
 276EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 277
 278#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 279
 280#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 281void __init set_platform_trusted_keys(struct key *keyring)
 282{
 283        platform_trusted_keys = keyring;
 284}
 285#endif
 286