certs/system_keyring.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* System trusted keyring for trusted public keys
   3  *
   4  * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/export.h>
   9 #include <linux/kernel.h>
  10 #include <linux/sched.h>
  11 #include <linux/cred.h>
  12 #include <linux/err.h>
  13 #include <linux/slab.h>
  14 #include <linux/uidgid.h>
  15 #include <linux/verification.h>
  16 #include <keys/asymmetric-type.h>
  17 #include <keys/system_keyring.h>
  18 #include <crypto/pkcs7.h>
  19
  20 static struct key *builtin_trusted_keys;
  21 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  22 static struct key *secondary_trusted_keys;
  23 #endif
  24 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
  25 static struct key *platform_trusted_keys;
  26 #endif
  27
  28 extern __initconst const u8 system_certificate_list[];
  29 extern __initconst const unsigned long system_certificate_list_size;
  30
  31 /**
  32  * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
  33  *
  34  * Restrict the addition of keys into a keyring based on the key-to-be-added
  35  * being vouched for by a key in the built in system keyring.
  36  */
  37 int restrict_link_by_builtin_trusted(struct key *dest_keyring,
  38                                      const struct key_type *type,
  39                                      const union key_payload *payload,
  40                                      struct key *restriction_key)
  41 {
  42         return restrict_link_by_signature(dest_keyring, type, payload,
  43                                           builtin_trusted_keys);
  44 }
  45
  46 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  47 /**
  48  * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
  49  *   addition by both builtin and secondary keyrings
  50  *
  51  * Restrict the addition of keys into a keyring based on the key-to-be-added
  52  * being vouched for by a key in either the built-in or the secondary system
  53  * keyrings.
  54  */
  55 int restrict_link_by_builtin_and_secondary_trusted(
  56         struct key *dest_keyring,
  57         const struct key_type *type,
  58         const union key_payload *payload,
  59         struct key *restrict_key)
  60 {
  61         /* If we have a secondary trusted keyring, then that contains a link
  62          * through to the builtin keyring and the search will follow that link.
  63          */
  64         if (type == &key_type_keyring &&
  65             dest_keyring == secondary_trusted_keys &&
  66             payload == &builtin_trusted_keys->payload)
  67                 /* Allow the builtin keyring to be added to the secondary */
  68                 return 0;
  69
  70         return restrict_link_by_signature(dest_keyring, type, payload,
  71                                           secondary_trusted_keys);
  72 }
  73
  74 /**
  75  * Allocate a struct key_restriction for the "builtin and secondary trust"
  76  * keyring. Only for use in system_trusted_keyring_init().
  77  */
  78 static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
  79 {
  80         struct key_restriction *restriction;
  81
  82         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
  83
  84         if (!restriction)
  85                 panic("Can't allocate secondary trusted keyring restriction\n");
  86
  87         restriction->check = restrict_link_by_builtin_and_secondary_trusted;
  88
  89         return restriction;
  90 }
  91 #endif
  92
  93 /*
  94  * Create the trusted keyrings
  95  */
  96 static __init int system_trusted_keyring_init(void)
  97 {
  98         pr_notice("Initialise system trusted keyrings\n");
  99
 100         builtin_trusted_keys =
 101                 keyring_alloc(".builtin_trusted_keys",
 102                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 103                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 104                               KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
 105                               KEY_ALLOC_NOT_IN_QUOTA,
 106                               NULL, NULL);
 107         if (IS_ERR(builtin_trusted_keys))
 108                 panic("Can't allocate builtin trusted keyring\n");
 109
 110 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 111         secondary_trusted_keys =
 112                 keyring_alloc(".secondary_trusted_keys",
 113                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 114                               ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 115                                KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
 116                                KEY_USR_WRITE),
 117                               KEY_ALLOC_NOT_IN_QUOTA,
 118                               get_builtin_and_secondary_restriction(),
 119                               NULL);
 120         if (IS_ERR(secondary_trusted_keys))
 121                 panic("Can't allocate secondary trusted keyring\n");
 122
 123         if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 124                 panic("Can't link trusted keyrings\n");
 125 #endif
 126
 127         return 0;
 128 }
 129
 130 /*
 131  * Must be initialised before we try and load the keys into the keyring.
 132  */
 133 device_initcall(system_trusted_keyring_init);
 134
 135 /*
 136  * Load the compiled-in list of X.509 certificates.
 137  */
 138 static __init int load_system_certificate_list(void)
 139 {
 140         key_ref_t key;
 141         const u8 *p, *end;
 142         size_t plen;
 143
 144         pr_notice("Loading compiled-in X.509 certificates\n");
 145
 146         p = system_certificate_list;
 147         end = p + system_certificate_list_size;
 148         while (p < end) {
 149                 /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
 150                  * than 256 bytes in size.
 151                  */
 152                 if (end - p < 4)
 153                         goto dodgy_cert;
 154                 if (p[0] != 0x30 &&
 155                     p[1] != 0x82)
 156                         goto dodgy_cert;
 157                 plen = (p[2] << 8) | p[3];
 158                 plen += 4;
 159                 if (plen > end - p)
 160                         goto dodgy_cert;
 161
 162                 key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
 163                                            "asymmetric",
 164                                            NULL,
 165                                            p,
 166                                            plen,
 167                                            ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 168                                            KEY_USR_VIEW | KEY_USR_READ),
 169                                            KEY_ALLOC_NOT_IN_QUOTA |
 170                                            KEY_ALLOC_BUILT_IN |
 171                                            KEY_ALLOC_BYPASS_RESTRICTION);
 172                 if (IS_ERR(key)) {
 173                         pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 174                                PTR_ERR(key));
 175                 } else {
 176                         pr_notice("Loaded X.509 cert '%s'\n",
 177                                   key_ref_to_ptr(key)->description);
 178                         key_ref_put(key);
 179                 }
 180                 p += plen;
 181         }
 182
 183         return 0;
 184
 185 dodgy_cert:
 186         pr_err("Problem parsing in-kernel X.509 certificate list\n");
 187         return 0;
 188 }
 189 late_initcall(load_system_certificate_list);
 190
 191 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 192
 193 /**
 194  * verify_pkcs7_message_sig - Verify a PKCS#7-based signature on system data.
 195  * @data: The data to be verified (NULL if expecting internal data).
 196  * @len: Size of @data.
 197  * @pkcs7: The PKCS#7 message that is the signature.
 198  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 199  *                                      (void *)1UL for all trusted keys).
 200  * @usage: The use to which the key is being put.
 201  * @view_content: Callback to gain access to content.
 202  * @ctx: Context for callback.
 203  */
 204 int verify_pkcs7_message_sig(const void *data, size_t len,
 205                              struct pkcs7_message *pkcs7,
 206                              struct key *trusted_keys,
 207                              enum key_being_used_for usage,
 208                              int (*view_content)(void *ctx,
 209                                                  const void *data, size_t len,
 210                                                  size_t asn1hdrlen),
 211                              void *ctx)
 212 {
 213         int ret;
 214
 215         /* The data should be detached - so we need to supply it. */
 216         if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 217                 pr_err("PKCS#7 signature with non-detached data\n");
 218                 ret = -EBADMSG;
 219                 goto error;
 220         }
 221
 222         ret = pkcs7_verify(pkcs7, usage);
 223         if (ret < 0)
 224                 goto error;
 225
 226         if (!trusted_keys) {
 227                 trusted_keys = builtin_trusted_keys;
 228         } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
 229 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 230                 trusted_keys = secondary_trusted_keys;
 231 #else
 232                 trusted_keys = builtin_trusted_keys;
 233 #endif
 234         } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
 235 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 236                 trusted_keys = platform_trusted_keys;
 237 #else
 238                 trusted_keys = NULL;
 239 #endif
 240                 if (!trusted_keys) {
 241                         ret = -ENOKEY;
 242                         pr_devel("PKCS#7 platform keyring is not available\n");
 243                         goto error;
 244                 }
 245         }
 246         ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 247         if (ret < 0) {
 248                 if (ret == -ENOKEY)
 249                         pr_devel("PKCS#7 signature not signed with a trusted key\n");
 250                 goto error;
 251         }
 252
 253         if (view_content) {
 254                 size_t asn1hdrlen;
 255
 256                 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 257                 if (ret < 0) {
 258                         if (ret == -ENODATA)
 259                                 pr_devel("PKCS#7 message does not contain data\n");
 260                         goto error;
 261                 }
 262
 263                 ret = view_content(ctx, data, len, asn1hdrlen);
 264         }
 265
 266 error:
 267         pr_devel("<==%s() = %d\n", __func__, ret);
 268         return ret;
 269 }
 270
 271 /**
 272  * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 273  * @data: The data to be verified (NULL if expecting internal data).
 274  * @len: Size of @data.
 275  * @raw_pkcs7: The PKCS#7 message that is the signature.
 276  * @pkcs7_len: The size of @raw_pkcs7.
 277  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 278  *                                      (void *)1UL for all trusted keys).
 279  * @usage: The use to which the key is being put.
 280  * @view_content: Callback to gain access to content.
 281  * @ctx: Context for callback.
 282  */
 283 int verify_pkcs7_signature(const void *data, size_t len,
 284                            const void *raw_pkcs7, size_t pkcs7_len,
 285                            struct key *trusted_keys,
 286                            enum key_being_used_for usage,
 287                            int (*view_content)(void *ctx,
 288                                                const void *data, size_t len,
 289                                                size_t asn1hdrlen),
 290                            void *ctx)
 291 {
 292         struct pkcs7_message *pkcs7;
 293         int ret;
 294
 295         pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 296         if (IS_ERR(pkcs7))
 297                 return PTR_ERR(pkcs7);
 298
 299         ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
 300                                        view_content, ctx);
 301
 302         pkcs7_free_message(pkcs7);
 303         pr_devel("<==%s() = %d\n", __func__, ret);
 304         return ret;
 305 }
 306 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 307
 308 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 309
 310 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 311 void __init set_platform_trusted_keys(struct key *keyring)
 312 {
 313         platform_trusted_keys = keyring;
 314 }
 315 #endif