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 #ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
  24 struct key *system_blacklist_keyring;
  25 #endif
  26
  27 extern __initconst const u8 system_certificate_list[];
  28 extern __initconst const unsigned long system_certificate_list_size;
  29
  30 /*
  31  * Load the compiled-in keys
  32  */
  33 static __init int system_trusted_keyring_init(void)
  34 {
  35         pr_notice("Initialise system trusted keyring\n");
  36
  37         system_trusted_keyring =
  38                 keyring_alloc(".system_keyring",
  39                               KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
  40                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  41                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
  42                               KEY_ALLOC_NOT_IN_QUOTA, NULL);
  43         if (IS_ERR(system_trusted_keyring))
  44                 panic("Can't allocate system trusted keyring\n");
  45
  46         set_bit(KEY_FLAG_TRUSTED_ONLY, &system_trusted_keyring->flags);
  47
  48         #ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
  49         system_blacklist_keyring = keyring_alloc(".system_blacklist_keyring",
  50                                     KUIDT_INIT(0), KGIDT_INIT(0),
  51                                     current_cred(),
  52                                     (KEY_POS_ALL & ~KEY_POS_SETATTR) |
  53                                     KEY_USR_VIEW | KEY_USR_READ,
  54                                     KEY_ALLOC_NOT_IN_QUOTA, NULL);
  55         if (IS_ERR(system_blacklist_keyring))
  56                 panic("Can't allocate system blacklist keyring\n");
  57
  58         set_bit(KEY_FLAG_TRUSTED_ONLY, &system_blacklist_keyring->flags);
  59 #endif
  60
  61         return 0;
  62 }
  63
  64 /*
  65  * Must be initialised before we try and load the keys into the keyring.
  66  */
  67 device_initcall(system_trusted_keyring_init);
  68
  69 /*
  70  * Load the compiled-in list of X.509 certificates.
  71  */
  72 static __init int load_system_certificate_list(void)
  73 {
  74         key_ref_t key;
  75         const u8 *p, *end;
  76         size_t plen;
  77
  78         pr_notice("Loading compiled-in X.509 certificates\n");
  79
  80         p = system_certificate_list;
  81         end = p + system_certificate_list_size;
  82         while (p < end) {
  83                 /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
  84                  * than 256 bytes in size.
  85                  */
  86                 if (end - p < 4)
  87                         goto dodgy_cert;
  88                 if (p[0] != 0x30 &&
  89                     p[1] != 0x82)
  90                         goto dodgy_cert;
  91                 plen = (p[2] << 8) | p[3];
  92                 plen += 4;
  93                 if (plen > end - p)
  94                         goto dodgy_cert;
  95
  96                 key = key_create_or_update(make_key_ref(system_trusted_keyring, 1),
  97                                            "asymmetric",
  98                                            NULL,
  99                                            p,
 100                                            plen,
 101                                            ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 102                                            KEY_USR_VIEW | KEY_USR_READ),
 103                                            KEY_ALLOC_NOT_IN_QUOTA |
 104                                            KEY_ALLOC_TRUSTED |
 105                                            KEY_ALLOC_BUILT_IN);
 106                 if (IS_ERR(key)) {
 107                         pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 108                                PTR_ERR(key));
 109                         WARN_ON_ONCE(1);
 110                 } else {
 111                         pr_notice("Loaded X.509 cert '%s'\n",
 112                                   key_ref_to_ptr(key)->description);
 113                         key_ref_put(key);
 114                 }
 115                 p += plen;
 116         }
 117
 118         return 0;
 119
 120 dodgy_cert:
 121         pr_err("Problem parsing in-kernel X.509 certificate list\n");
 122         return 0;
 123 }
 124 late_initcall(load_system_certificate_list);
 125
 126 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 127
 128 /**
 129  * Verify a PKCS#7-based signature on system data.
 130  * @data: The data to be verified.
 131  * @len: Size of @data.
 132  * @raw_pkcs7: The PKCS#7 message that is the signature.
 133  * @pkcs7_len: The size of @raw_pkcs7.
 134  * @usage: The use to which the key is being put.
 135  */
 136 int system_verify_data(const void *data, unsigned long len,
 137                        const void *raw_pkcs7, size_t pkcs7_len,
 138                        enum key_being_used_for usage)
 139 {
 140         struct pkcs7_message *pkcs7;
 141         bool trusted;
 142         int ret;
 143
 144         pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 145         if (IS_ERR(pkcs7))
 146                 return PTR_ERR(pkcs7);
 147
 148         /* The data should be detached - so we need to supply it. */
 149         if (pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 150                 pr_err("PKCS#7 signature with non-detached data\n");
 151                 ret = -EBADMSG;
 152                 goto error;
 153         }
 154
 155         ret = pkcs7_verify(pkcs7, usage);
 156         if (ret < 0)
 157                 goto error;
 158
 159 #ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
 160         ret = pkcs7_validate_trust(pkcs7, system_blacklist_keyring, &trusted);
 161         if (!ret) {
 162                 /* module is signed with a cert in the blacklist.  reject */
 163                 pr_err("Module key is in the blacklist\n");
 164                 ret = -EKEYREJECTED;
 165                 goto error;
 166         }
 167 #endif
 168
 169         ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
 170         if (ret < 0)
 171                 goto error;
 172
 173         if (!trusted) {
 174                 pr_err("PKCS#7 signature not signed with a trusted key\n");
 175                 ret = -ENOKEY;
 176         }
 177
 178 error:
 179         pkcs7_free_message(pkcs7);
 180         pr_devel("<==%s() = %d\n", __func__, ret);
 181         return ret;
 182 }
 183 EXPORT_SYMBOL_GPL(system_verify_data);
 184
 185 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */