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