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 <linux/slab.h>
  18#include <linux/verification.h>
  19#include <keys/asymmetric-type.h>
  20#include <keys/system_keyring.h>
  21#include <crypto/pkcs7.h>
  22
  23static struct key *builtin_trusted_keys;
  24#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  25static struct key *secondary_trusted_keys;
  26#endif
  27#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
  28static struct key *platform_trusted_keys;
  29#endif
  30
  31extern __initconst const u8 system_certificate_list[];
  32extern __initconst const unsigned long system_certificate_list_size;
  33
  34/**
  35 * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
  36 *
  37 * Restrict the addition of keys into a keyring based on the key-to-be-added
  38 * being vouched for by a key in the built in system keyring.
  39 */
  40int restrict_link_by_builtin_trusted(struct key *dest_keyring,
  41                                     const struct key_type *type,
  42                                     const union key_payload *payload,
  43                                     struct key *restriction_key)
  44{
  45        return restrict_link_by_signature(dest_keyring, type, payload,
  46                                          builtin_trusted_keys);
  47}
  48
  49#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  50/**
  51 * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  52 *   addition by both builtin and secondary keyrings
  53 *
  54 * Restrict the addition of keys into a keyring based on the key-to-be-added
  55 * being vouched for by a key in either the built-in or the secondary system
  56 * keyrings.
  57 */
  58int restrict_link_by_builtin_and_secondary_trusted(
  59        struct key *dest_keyring,
  60        const struct key_type *type,
  61        const union key_payload *payload,
  62        struct key *restrict_key)
  63{
  64        /* If we have a secondary trusted keyring, then that contains a link
  65         * through to the builtin keyring and the search will follow that link.
  66         */
  67        if (type == &key_type_keyring &&
  68            dest_keyring == secondary_trusted_keys &&
  69            payload == &builtin_trusted_keys->payload)
  70                /* Allow the builtin keyring to be added to the secondary */
  71                return 0;
  72
  73        return restrict_link_by_signature(dest_keyring, type, payload,
  74                                          secondary_trusted_keys);
  75}
  76
  77/**
  78 * Allocate a struct key_restriction for the "builtin and secondary trust"
  79 * keyring. Only for use in system_trusted_keyring_init().
  80 */
  81static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
  82{
  83        struct key_restriction *restriction;
  84
  85        restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
  86
  87        if (!restriction)
  88                panic("Can't allocate secondary trusted keyring restriction\n");
  89
  90        restriction->check = restrict_link_by_builtin_and_secondary_trusted;
  91
  92        return restriction;
  93}
  94#endif
  95
  96/*
  97 * Create the trusted keyrings
  98 */
  99static __init int system_trusted_keyring_init(void)
 100{
 101        pr_notice("Initialise system trusted keyrings\n");
 102
 103        builtin_trusted_keys =
 104                keyring_alloc(".builtin_trusted_keys",
 105                              KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
 106                              ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 107                              KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 108                              KEY_ALLOC_NOT_IN_QUOTA,
 109                              NULL, NULL);
 110        if (IS_ERR(builtin_trusted_keys))
 111                panic("Can't allocate builtin trusted keyring\n");
 112
 113#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 114        secondary_trusted_keys =
 115                keyring_alloc(".secondary_trusted_keys",
 116                              KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
 117                              ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 118                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
 119                               KEY_USR_WRITE),
 120                              KEY_ALLOC_NOT_IN_QUOTA,
 121                              get_builtin_and_secondary_restriction(),
 122                              NULL);
 123        if (IS_ERR(secondary_trusted_keys))
 124                panic("Can't allocate secondary trusted keyring\n");
 125
 126        if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 127                panic("Can't link trusted keyrings\n");
 128#endif
 129
 130        return 0;
 131}
 132
 133/*
 134 * Must be initialised before we try and load the keys into the keyring.
 135 */
 136device_initcall(system_trusted_keyring_init);
 137
 138/*
 139 * Load the compiled-in list of X.509 certificates.
 140 */
 141static __init int load_system_certificate_list(void)
 142{
 143        key_ref_t key;
 144        const u8 *p, *end;
 145        size_t plen;
 146
 147        pr_notice("Loading compiled-in X.509 certificates\n");
 148
 149        p = system_certificate_list;
 150        end = p + system_certificate_list_size;
 151        while (p < end) {
 152                /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
 153                 * than 256 bytes in size.
 154                 */
 155                if (end - p < 4)
 156                        goto dodgy_cert;
 157                if (p[0] != 0x30 &&
 158                    p[1] != 0x82)
 159                        goto dodgy_cert;
 160                plen = (p[2] << 8) | p[3];
 161                plen += 4;
 162                if (plen > end - p)
 163                        goto dodgy_cert;
 164
 165                key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
 166                                           "asymmetric",
 167                                           NULL,
 168                                           p,
 169                                           plen,
 170                                           ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 171                                           KEY_USR_VIEW | KEY_USR_READ),
 172                                           KEY_ALLOC_NOT_IN_QUOTA |
 173                                           KEY_ALLOC_BUILT_IN |
 174                                           KEY_ALLOC_BYPASS_RESTRICTION);
 175                if (IS_ERR(key)) {
 176                        pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 177                               PTR_ERR(key));
 178                } else {
 179                        pr_notice("Loaded X.509 cert '%s'\n",
 180                                  key_ref_to_ptr(key)->description);
 181                        key_ref_put(key);
 182                }
 183                p += plen;
 184        }
 185
 186        return 0;
 187
 188dodgy_cert:
 189        pr_err("Problem parsing in-kernel X.509 certificate list\n");
 190        return 0;
 191}
 192late_initcall(load_system_certificate_list);
 193
 194#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 195
 196/**
 197 * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 198 * @data: The data to be verified (NULL if expecting internal data).
 199 * @len: Size of @data.
 200 * @raw_pkcs7: The PKCS#7 message that is the signature.
 201 * @pkcs7_len: The size of @raw_pkcs7.
 202 * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 203 *                                      (void *)1UL for all trusted keys).
 204 * @usage: The use to which the key is being put.
 205 * @view_content: Callback to gain access to content.
 206 * @ctx: Context for callback.
 207 */
 208int verify_pkcs7_signature(const void *data, size_t len,
 209                           const void *raw_pkcs7, size_t pkcs7_len,
 210                           struct key *trusted_keys,
 211                           enum key_being_used_for usage,
 212                           int (*view_content)(void *ctx,
 213                                               const void *data, size_t len,
 214                                               size_t asn1hdrlen),
 215                           void *ctx)
 216{
 217        struct pkcs7_message *pkcs7;
 218        int ret;
 219
 220        pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 221        if (IS_ERR(pkcs7))
 222                return PTR_ERR(pkcs7);
 223
 224        /* The data should be detached - so we need to supply it. */
 225        if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 226                pr_err("PKCS#7 signature with non-detached data\n");
 227                ret = -EBADMSG;
 228                goto error;
 229        }
 230
 231        ret = pkcs7_verify(pkcs7, usage);
 232        if (ret < 0)
 233                goto error;
 234
 235        if (!trusted_keys) {
 236                trusted_keys = builtin_trusted_keys;
 237        } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
 238#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 239                trusted_keys = secondary_trusted_keys;
 240#else
 241                trusted_keys = builtin_trusted_keys;
 242#endif
 243        } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
 244#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 245                trusted_keys = platform_trusted_keys;
 246#else
 247                trusted_keys = NULL;
 248#endif
 249                if (!trusted_keys) {
 250                        ret = -ENOKEY;
 251                        pr_devel("PKCS#7 platform keyring is not available\n");
 252                        goto error;
 253                }
 254        }
 255        ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 256        if (ret < 0) {
 257                if (ret == -ENOKEY)
 258                        pr_devel("PKCS#7 signature not signed with a trusted key\n");
 259                goto error;
 260        }
 261
 262        if (view_content) {
 263                size_t asn1hdrlen;
 264
 265                ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 266                if (ret < 0) {
 267                        if (ret == -ENODATA)
 268                                pr_devel("PKCS#7 message does not contain data\n");
 269                        goto error;
 270                }
 271
 272                ret = view_content(ctx, data, len, asn1hdrlen);
 273        }
 274
 275error:
 276        pkcs7_free_message(pkcs7);
 277        pr_devel("<==%s() = %d\n", __func__, ret);
 278        return ret;
 279}
 280EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 281
 282#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 283void __init set_platform_trusted_keys(struct key *keyring)
 284{
 285        platform_trusted_keys = keyring;
 286}
 287#endif
 288
 289#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 290