certs/system_keyring.c

   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
  21 struct key *system_trusted_keyring;
  22 EXPORT_SYMBOL_GPL(system_trusted_keyring);
  23
  24 extern __initconst const u8 system_certificate_list[];
  25 extern __initconst const unsigned long system_certificate_list_size;
  26
  27 /*
  28  * Load the compiled-in keys
  29  */
  30 static __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  */
  50 device_initcall(system_trusted_keyring_init);
  51
  52 /*
  53  * Load the compiled-in list of X.509 certificates.
  54  */
  55 static __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                 if (IS_ERR(key)) {
  89                         pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
  90                                PTR_ERR(key));
  91                 } else {
  92                         set_bit(KEY_FLAG_BUILTIN, &key_ref_to_ptr(key)->flags);
  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
 102 dodgy_cert:
 103         pr_err("Problem parsing in-kernel X.509 certificate list\n");
 104         return 0;
 105 }
 106 late_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  */
 118 int 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
 150 error:
 151         pkcs7_free_message(pkcs7);
 152         pr_devel("<==%s() = %d\n", __func__, ret);
 153         return ret;
 154 }
 155 EXPORT_SYMBOL_GPL(system_verify_data);
 156
 157 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */