LXR linux/certs/system

   1/* System trusted keyring for trusted public keys
   2 *
   3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public Licence
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the Licence, or (at your option) any later version.
  10 */
  11
  12#include <linux/export.h>
  13#include <linux/kernel.h>
  14#include <linux/sched.h>
  15#include <linux/cred.h>
  16#include <linux/err.h>
  17#include <keys/asymmetric-type.h>
  18#include <keys/system_keyring.h>
  19#include <crypto/pkcs7.h>
  20
  21static struct key *builtin_trusted_keys;
  22#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  23static struct key *secondary_trusted_keys;
  24#endif
  25
  26extern __initconst const u8 system_certificate_list[];
  27extern __initconst const unsigned long system_certificate_list_size;
  28
  29/**
  30 * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
  31 *
  32 * Restrict the addition of keys into a keyring based on the key-to-be-added
  33 * being vouched for by a key in the built in system keyring.
  34 */
  35int restrict_link_by_builtin_trusted(struct key *keyring,
  36                                     const struct key_type *type,
  37                                     const union key_payload *payload)
  38{
  39        return restrict_link_by_signature(builtin_trusted_keys, type, payload);
  40}
  41
  42#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  43/**
  44 * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  45 *   addition by both builtin and secondary keyrings
  46 *
  47 * Restrict the addition of keys into a keyring based on the key-to-be-added
  48 * being vouched for by a key in either the built-in or the secondary system
  49 * keyrings.
  50 */
  51int restrict_link_by_builtin_and_secondary_trusted(
  52        struct key *keyring,
  53        const struct key_type *type,
  54        const union key_payload *payload)
  55{
  56        /* If we have a secondary trusted keyring, then that contains a link
  57         * through to the builtin keyring and the search will follow that link.
  58         */
  59        if (type == &key_type_keyring &&
  60            keyring == secondary_trusted_keys &&
  61            payload == &builtin_trusted_keys->payload)
  62                /* Allow the builtin keyring to be added to the secondary */
  63                return 0;
  64
  65        return restrict_link_by_signature(secondary_trusted_keys, type, payload);
  66}
  67#endif
  68
  69/*
  70 * Create the trusted keyrings
  71 */
  72static __init int system_trusted_keyring_init(void)
  73{
  74        pr_notice("Initialise system trusted keyrings\n");
  75
  76        builtin_trusted_keys =
  77                keyring_alloc(".builtin_trusted_keys",
  78                              KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
  79                              ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  80                              KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
  81                              KEY_ALLOC_NOT_IN_QUOTA,
  82                              NULL, NULL);
  83        if (IS_ERR(builtin_trusted_keys))
  84                panic("Can't allocate builtin trusted keyring\n");
  85
  86#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  87        secondary_trusted_keys =
  88                keyring_alloc(".secondary_trusted_keys",
  89                              KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
  90                              ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  91                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
  92                               KEY_USR_WRITE),
  93                              KEY_ALLOC_NOT_IN_QUOTA,
  94                              restrict_link_by_builtin_and_secondary_trusted,
  95                              NULL);
  96        if (IS_ERR(secondary_trusted_keys))
  97                panic("Can't allocate secondary trusted keyring\n");
  98
  99        if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 100                panic("Can't link trusted keyrings\n");
 101#endif
 102
 103        return 0;
 104}
 105
 106/*
 107 * Must be initialised before we try and load the keys into the keyring.
 108 */
 109device_initcall(system_trusted_keyring_init);
 110
 111/*
 112 * Load the compiled-in list of X.509 certificates.
 113 */
 114static __init int load_system_certificate_list(void)
 115{
 116        key_ref_t key;
 117        const u8 *p, *end;
 118        size_t plen;
 119
 120        pr_notice("Loading compiled-in X.509 certificates\n");
 121
 122        p = system_certificate_list;
 123        end = p + system_certificate_list_size;
 124        while (p < end) {
 125                /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
 126                 * than 256 bytes in size.
 127                 */
 128                if (end - p < 4)
 129                        goto dodgy_cert;
 130                if (p[0] != 0x30 &&
 131                    p[1] != 0x82)
 132                        goto dodgy_cert;
 133                plen = (p[2] << 8) | p[3];
 134                plen += 4;
 135                if (plen > end - p)
 136                        goto dodgy_cert;
 137
 138                key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
 139                                           "asymmetric",
 140                                           NULL,
 141                                           p,
 142                                           plen,
 143                                           ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 144                                           KEY_USR_VIEW | KEY_USR_READ),
 145                                           KEY_ALLOC_NOT_IN_QUOTA |
 146                                           KEY_ALLOC_BUILT_IN |
 147                                           KEY_ALLOC_BYPASS_RESTRICTION);
 148                if (IS_ERR(key)) {
 149                        pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 150                               PTR_ERR(key));
 151                } else {
 152                        pr_notice("Loaded X.509 cert '%s'\n",
 153                                  key_ref_to_ptr(key)->description);
 154                        key_ref_put(key);
 155                }
 156                p += plen;
 157        }
 158
 159        return 0;
 160
 161dodgy_cert:
 162        pr_err("Problem parsing in-kernel X.509 certificate list\n");
 163        return 0;
 164}
 165late_initcall(load_system_certificate_list);
 166
 167#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 168
 169/**
 170 * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 171 * @data: The data to be verified (NULL if expecting internal data).
 172 * @len: Size of @data.
 173 * @raw_pkcs7: The PKCS#7 message that is the signature.
 174 * @pkcs7_len: The size of @raw_pkcs7.
 175 * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 176 *                                      (void *)1UL for all trusted keys).
 177 * @usage: The use to which the key is being put.
 178 * @view_content: Callback to gain access to content.
 179 * @ctx: Context for callback.
 180 */
 181int verify_pkcs7_signature(const void *data, size_t len,
 182                           const void *raw_pkcs7, size_t pkcs7_len,
 183                           struct key *trusted_keys,
 184                           enum key_being_used_for usage,
 185                           int (*view_content)(void *ctx,
 186                                               const void *data, size_t len,
 187                                               size_t asn1hdrlen),
 188                           void *ctx)
 189{
 190        struct pkcs7_message *pkcs7;
 191        int ret;
 192
 193        pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 194        if (IS_ERR(pkcs7))
 195                return PTR_ERR(pkcs7);
 196
 197        /* The data should be detached - so we need to supply it. */
 198        if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 199                pr_err("PKCS#7 signature with non-detached data\n");
 200                ret = -EBADMSG;
 201                goto error;
 202        }
 203
 204        ret = pkcs7_verify(pkcs7, usage);
 205        if (ret < 0)
 206                goto error;
 207
 208        if (!trusted_keys) {
 209                trusted_keys = builtin_trusted_keys;
 210        } else if (trusted_keys == (void *)1UL) {
 211#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 212                trusted_keys = secondary_trusted_keys;
 213#else
 214                trusted_keys = builtin_trusted_keys;
 215#endif
 216        }
 217        ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 218        if (ret < 0) {
 219                if (ret == -ENOKEY)
 220                        pr_err("PKCS#7 signature not signed with a trusted key\n");
 221                goto error;
 222        }
 223
 224        if (view_content) {
 225                size_t asn1hdrlen;
 226
 227                ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 228                if (ret < 0) {
 229                        if (ret == -ENODATA)
 230                                pr_devel("PKCS#7 message does not contain data\n");
 231                        goto error;
 232                }
 233
 234                ret = view_content(ctx, data, len, asn1hdrlen);
 235        }
 236
 237error:
 238        pkcs7_free_message(pkcs7);
 239        pr_devel("<==%s() = %d\n", __func__, ret);
 240        return ret;
 241}
 242EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 243
 244#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 245