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/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 #include "internal.h"
  23
  24 static struct key *builtin_trusted_keys;
  25 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  26 static struct key *secondary_trusted_keys;
  27 #endif
  28
  29 extern __initconst const u8 system_certificate_list[];
  30 extern __initconst const unsigned long system_certificate_list_size;
  31
  32 /**
  33  * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
  34  *
  35  * Restrict the addition of keys into a keyring based on the key-to-be-added
  36  * being vouched for by a key in the built in system keyring.
  37  */
  38 int restrict_link_by_builtin_trusted(struct key *dest_keyring,
  39                                      const struct key_type *type,
  40                                      const union key_payload *payload,
  41                                      struct key *restriction_key)
  42 {
  43         return restrict_link_by_signature(dest_keyring, type, payload,
  44                                           builtin_trusted_keys);
  45 }
  46
  47 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  48 /**
  49  * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  50  *   addition by both builtin and secondary keyrings
  51  *
  52  * Restrict the addition of keys into a keyring based on the key-to-be-added
  53  * being vouched for by a key in either the built-in or the secondary system
  54  * keyrings.
  55  */
  56 int restrict_link_by_builtin_and_secondary_trusted(
  57         struct key *dest_keyring,
  58         const struct key_type *type,
  59         const union key_payload *payload,
  60         struct key *restrict_key)
  61 {
  62         /* If we have a secondary trusted keyring, then that contains a link
  63          * through to the builtin keyring and the search will follow that link.
  64          */
  65         if (type == &key_type_keyring &&
  66             dest_keyring == secondary_trusted_keys &&
  67             payload == &builtin_trusted_keys->payload)
  68                 /* Allow the builtin keyring to be added to the secondary */
  69                 return 0;
  70
  71         return restrict_link_by_signature(dest_keyring, type, payload,
  72                                           secondary_trusted_keys);
  73 }
  74
  75 /**
  76  * Allocate a struct key_restriction for the "builtin and secondary trust"
  77  * keyring. Only for use in system_trusted_keyring_init().
  78  */
  79 static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
  80 {
  81         struct key_restriction *restriction;
  82
  83         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
  84
  85         if (!restriction)
  86                 panic("Can't allocate secondary trusted keyring restriction\n");
  87
  88         restriction->check = restrict_link_by_builtin_and_secondary_trusted;
  89
  90         return restriction;
  91 }
  92 #endif
  93
  94 /*
  95  * Create the trusted keyrings
  96  */
  97 static __init int system_trusted_keyring_init(void)
  98 {
  99         pr_notice("Initialise system trusted keyrings\n");
 100
 101         builtin_trusted_keys =
 102                 keyring_alloc(".builtin_trusted_keys",
 103                               KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
 104                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 105                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 106                               KEY_ALLOC_NOT_IN_QUOTA,
 107                               NULL, NULL);
 108         if (IS_ERR(builtin_trusted_keys))
 109                 panic("Can't allocate builtin trusted keyring\n");
 110
 111 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 112         secondary_trusted_keys =
 113                 keyring_alloc(".secondary_trusted_keys",
 114                               KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
 115                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 116                                KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
 117                                KEY_USR_WRITE),
 118                               KEY_ALLOC_NOT_IN_QUOTA,
 119                               get_builtin_and_secondary_restriction(),
 120                               NULL);
 121         if (IS_ERR(secondary_trusted_keys))
 122                 panic("Can't allocate secondary trusted keyring\n");
 123
 124         if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 125                 panic("Can't link trusted keyrings\n");
 126 #endif
 127
 128         return 0;
 129 }
 130
 131 /*
 132  * Must be initialised before we try and load the keys into the keyring.
 133  */
 134 device_initcall(system_trusted_keyring_init);
 135
 136 /*
 137  * Load the compiled-in list of X.509 certificates.
 138  */
 139 static __init int load_system_certificate_list(void)
 140 {
 141         key_ref_t key;
 142         const u8 *p, *end;
 143         size_t plen;
 144
 145         pr_notice("Loading compiled-in X.509 certificates\n");
 146
 147         p = system_certificate_list;
 148         end = p + system_certificate_list_size;
 149         while (p < end) {
 150                 /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
 151                  * than 256 bytes in size.
 152                  */
 153                 if (end - p < 4)
 154                         goto dodgy_cert;
 155                 if (p[0] != 0x30 &&
 156                     p[1] != 0x82)
 157                         goto dodgy_cert;
 158                 plen = (p[2] << 8) | p[3];
 159                 plen += 4;
 160                 if (plen > end - p)
 161                         goto dodgy_cert;
 162
 163                 key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
 164                                            "asymmetric",
 165                                            NULL,
 166                                            p,
 167                                            plen,
 168                                            ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 169                                            KEY_USR_VIEW | KEY_USR_READ),
 170                                            KEY_ALLOC_NOT_IN_QUOTA |
 171                                            KEY_ALLOC_BUILT_IN |
 172                                            KEY_ALLOC_BYPASS_RESTRICTION);
 173                 if (IS_ERR(key)) {
 174                         pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 175                                PTR_ERR(key));
 176                         WARN_ON_ONCE(1);
 177                 } else {
 178                         pr_notice("Loaded X.509 cert '%s'\n",
 179                                   key_ref_to_ptr(key)->description);
 180                         key_ref_put(key);
 181                 }
 182                 p += plen;
 183         }
 184
 185         return 0;
 186
 187 dodgy_cert:
 188         pr_err("Problem parsing in-kernel X.509 certificate list\n");
 189         return 0;
 190 }
 191 late_initcall(load_system_certificate_list);
 192
 193 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 194
 195 /**
 196  * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 197  * @data: The data to be verified (NULL if expecting internal data).
 198  * @len: Size of @data.
 199  * @raw_pkcs7: The PKCS#7 message that is the signature.
 200  * @pkcs7_len: The size of @raw_pkcs7.
 201  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 202  *                                      (void *)1UL for all trusted keys).
 203  * @usage: The use to which the key is being put.
 204  * @view_content: Callback to gain access to content.
 205  * @ctx: Context for callback.
 206  */
 207 int verify_pkcs7_signature(const void *data, size_t len,
 208                            const void *raw_pkcs7, size_t pkcs7_len,
 209                            struct key *trusted_keys,
 210                            enum key_being_used_for usage,
 211                            int (*view_content)(void *ctx,
 212                                                const void *data, size_t len,
 213                                                size_t asn1hdrlen),
 214                            void *ctx)
 215 {
 216         struct pkcs7_message *pkcs7;
 217         int ret;
 218
 219         pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 220         if (IS_ERR(pkcs7))
 221                 return PTR_ERR(pkcs7);
 222
 223         /* The data should be detached - so we need to supply it. */
 224         if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 225                 pr_err("PKCS#7 signature with non-detached data\n");
 226                 ret = -EBADMSG;
 227                 goto error;
 228         }
 229
 230         ret = pkcs7_verify(pkcs7, usage);
 231         if (ret < 0)
 232                 goto error;
 233
 234         if (!trusted_keys) {
 235                 trusted_keys = builtin_trusted_keys;
 236         } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
 237 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 238                 trusted_keys = secondary_trusted_keys;
 239 #else
 240                 trusted_keys = builtin_trusted_keys;
 241 #endif
 242         }
 243         ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 244         if (ret < 0) {
 245                 if (ret == -ENOKEY)
 246                         pr_err("PKCS#7 signature not signed with a trusted key\n");
 247                 goto error;
 248         }
 249
 250         if (view_content) {
 251                 size_t asn1hdrlen;
 252
 253                 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 254                 if (ret < 0) {
 255                         if (ret == -ENODATA)
 256                                 pr_devel("PKCS#7 message does not contain data\n");
 257                         goto error;
 258                 }
 259
 260                 ret = view_content(ctx, data, len, asn1hdrlen);
 261         }
 262
 263 error:
 264         pkcs7_free_message(pkcs7);
 265         pr_devel("<==%s() = %d\n", __func__, ret);
 266         return ret;
 267 }
 268 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 269
 270 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 271
 272 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 273 /**
 274  * add_trusted_secondary_key - Add to secondary keyring with no validation
 275  * @source: Source of key
 276  * @data: The blob holding the key
 277  * @len: The length of the data blob
 278  *
 279  * Add a key to the secondary keyring without checking its trust chain.  This
 280  * is available only during kernel initialisation.
 281  */
 282 void __init add_trusted_secondary_key(const char *source,
 283                                       const void *data, size_t len)
 284 {
 285         key_ref_t key;
 286
 287         key = key_create_or_update(make_key_ref(secondary_trusted_keys, 1),
 288                                    "asymmetric",
 289                                    NULL, data, len,
 290                                    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
 291                                    KEY_USR_VIEW,
 292                                    KEY_ALLOC_NOT_IN_QUOTA |
 293                                    KEY_ALLOC_BYPASS_RESTRICTION);
 294
 295         if (IS_ERR(key))
 296                 pr_err("Problem loading %s X.509 certificate (%ld)\n",
 297                        source, PTR_ERR(key));
 298         else
 299                 pr_notice("Loaded %s cert '%s' linked to secondary sys keyring\n",
 300                           source, key_ref_to_ptr(key)->description);
 301 }
 302 #endif /* CONFIG_SECONDARY_TRUSTED_KEYRING */