linux/certs/system_keyring.c
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   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
  21struct key *system_trusted_keyring;
  22EXPORT_SYMBOL_GPL(system_trusted_keyring);
  23
  24extern __initconst const u8 system_certificate_list[];
  25extern __initconst const unsigned long system_certificate_list_size;
  26
  27/*
  28 * Load the compiled-in keys
  29 */
  30static __init int system_trusted_keyring_init(void)
  31{
  32        pr_notice("Initialise system trusted keyring\n");
  33
  34        system_trusted_keyring =
  35                keyring_alloc(".system_keyring",
  36                              KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
  37                              ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  38                              KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
  39                              KEY_ALLOC_NOT_IN_QUOTA, NULL);
  40        if (IS_ERR(system_trusted_keyring))
  41                panic("Can't allocate system trusted keyring\n");
  42
  43        set_bit(KEY_FLAG_TRUSTED_ONLY, &system_trusted_keyring->flags);
  44        return 0;
  45}
  46
  47/*
  48 * Must be initialised before we try and load the keys into the keyring.
  49 */
  50device_initcall(system_trusted_keyring_init);
  51
  52/*
  53 * Load the compiled-in list of X.509 certificates.
  54 */
  55static __init int load_system_certificate_list(void)
  56{
  57        key_ref_t key;
  58        const u8 *p, *end;
  59        size_t plen;
  60
  61        pr_notice("Loading compiled-in X.509 certificates\n");
  62
  63        p = system_certificate_list;
  64        end = p + system_certificate_list_size;
  65        while (p < end) {
  66                /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
  67                 * than 256 bytes in size.
  68                 */
  69                if (end - p < 4)
  70                        goto dodgy_cert;
  71                if (p[0] != 0x30 &&
  72                    p[1] != 0x82)
  73                        goto dodgy_cert;
  74                plen = (p[2] << 8) | p[3];
  75                plen += 4;
  76                if (plen > end - p)
  77                        goto dodgy_cert;
  78
  79                key = key_create_or_update(make_key_ref(system_trusted_keyring, 1),
  80                                           "asymmetric",
  81                                           NULL,
  82                                           p,
  83                                           plen,
  84                                           ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  85                                           KEY_USR_VIEW | KEY_USR_READ),
  86                                           KEY_ALLOC_NOT_IN_QUOTA |
  87                                           KEY_ALLOC_TRUSTED |
  88                                           KEY_ALLOC_BUILT_IN);
  89                if (IS_ERR(key)) {
  90                        pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
  91                               PTR_ERR(key));
  92                } else {
  93                        pr_notice("Loaded X.509 cert '%s'\n",
  94                                  key_ref_to_ptr(key)->description);
  95                        key_ref_put(key);
  96                }
  97                p += plen;
  98        }
  99
 100        return 0;
 101
 102dodgy_cert:
 103        pr_err("Problem parsing in-kernel X.509 certificate list\n");
 104        return 0;
 105}
 106late_initcall(load_system_certificate_list);
 107
 108#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 109
 110/**
 111 * Verify a PKCS#7-based signature on system data.
 112 * @data: The data to be verified.
 113 * @len: Size of @data.
 114 * @raw_pkcs7: The PKCS#7 message that is the signature.
 115 * @pkcs7_len: The size of @raw_pkcs7.
 116 * @usage: The use to which the key is being put.
 117 */
 118int system_verify_data(const void *data, unsigned long len,
 119                       const void *raw_pkcs7, size_t pkcs7_len,
 120                       enum key_being_used_for usage)
 121{
 122        struct pkcs7_message *pkcs7;
 123        bool trusted;
 124        int ret;
 125
 126        pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 127        if (IS_ERR(pkcs7))
 128                return PTR_ERR(pkcs7);
 129
 130        /* The data should be detached - so we need to supply it. */
 131        if (pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 132                pr_err("PKCS#7 signature with non-detached data\n");
 133                ret = -EBADMSG;
 134                goto error;
 135        }
 136
 137        ret = pkcs7_verify(pkcs7, usage);
 138        if (ret < 0)
 139                goto error;
 140
 141        ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
 142        if (ret < 0)
 143                goto error;
 144
 145        if (!trusted) {
 146                pr_err("PKCS#7 signature not signed with a trusted key\n");
 147                ret = -ENOKEY;
 148        }
 149
 150error:
 151        pkcs7_free_message(pkcs7);
 152        pr_devel("<==%s() = %d\n", __func__, ret);
 153        return ret;
 154}
 155EXPORT_SYMBOL_GPL(system_verify_data);
 156
 157#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 158