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