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