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                               &internal_key_acl, KEY_ALLOC_NOT_IN_QUOTA,
 103                               NULL, NULL);
 104         if (IS_ERR(builtin_trusted_keys))
 105                 panic("Can't allocate builtin trusted keyring\n");
 106
 107 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 108         secondary_trusted_keys =
 109                 keyring_alloc(".secondary_trusted_keys",
 110                               KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
 111                               &internal_writable_keyring_acl, KEY_ALLOC_NOT_IN_QUOTA,
 112                               get_builtin_and_secondary_restriction(),
 113                               NULL);
 114         if (IS_ERR(secondary_trusted_keys))
 115                 panic("Can't allocate secondary trusted keyring\n");
 116
 117         if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 118                 panic("Can't link trusted keyrings\n");
 119 #endif
 120
 121         return 0;
 122 }
 123
 124 /*
 125  * Must be initialised before we try and load the keys into the keyring.
 126  */
 127 device_initcall(system_trusted_keyring_init);
 128
 129 /*
 130  * Load the compiled-in list of X.509 certificates.
 131  */
 132 static __init int load_system_certificate_list(void)
 133 {
 134         key_ref_t key;
 135         const u8 *p, *end;
 136         size_t plen;
 137
 138         pr_notice("Loading compiled-in X.509 certificates\n");
 139
 140         p = system_certificate_list;
 141         end = p + system_certificate_list_size;
 142         while (p < end) {
 143                 /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
 144                  * than 256 bytes in size.
 145                  */
 146                 if (end - p < 4)
 147                         goto dodgy_cert;
 148                 if (p[0] != 0x30 &&
 149                     p[1] != 0x82)
 150                         goto dodgy_cert;
 151                 plen = (p[2] << 8) | p[3];
 152                 plen += 4;
 153                 if (plen > end - p)
 154                         goto dodgy_cert;
 155
 156                 key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
 157                                            "asymmetric",
 158                                            NULL,
 159                                            p,
 160                                            plen,
 161                                            &internal_key_acl,
 162                                            KEY_ALLOC_NOT_IN_QUOTA |
 163                                            KEY_ALLOC_BUILT_IN |
 164                                            KEY_ALLOC_BYPASS_RESTRICTION);
 165                 if (IS_ERR(key)) {
 166                         pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 167                                PTR_ERR(key));
 168                 } else {
 169                         pr_notice("Loaded X.509 cert '%s'\n",
 170                                   key_ref_to_ptr(key)->description);
 171                         key_ref_put(key);
 172                 }
 173                 p += plen;
 174         }
 175
 176         return 0;
 177
 178 dodgy_cert:
 179         pr_err("Problem parsing in-kernel X.509 certificate list\n");
 180         return 0;
 181 }
 182 late_initcall(load_system_certificate_list);
 183
 184 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 185
 186 /**
 187  * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
 188  * @data: The data to be verified (NULL if expecting internal data).
 189  * @len: Size of @data.
 190  * @raw_pkcs7: The PKCS#7 message that is the signature.
 191  * @pkcs7_len: The size of @raw_pkcs7.
 192  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
 193  *                                      (void *)1UL for all trusted keys).
 194  * @usage: The use to which the key is being put.
 195  * @view_content: Callback to gain access to content.
 196  * @ctx: Context for callback.
 197  */
 198 int verify_pkcs7_signature(const void *data, size_t len,
 199                            const void *raw_pkcs7, size_t pkcs7_len,
 200                            struct key *trusted_keys,
 201                            enum key_being_used_for usage,
 202                            int (*view_content)(void *ctx,
 203                                                const void *data, size_t len,
 204                                                size_t asn1hdrlen),
 205                            void *ctx)
 206 {
 207         struct pkcs7_message *pkcs7;
 208         int ret;
 209
 210         pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
 211         if (IS_ERR(pkcs7))
 212                 return PTR_ERR(pkcs7);
 213
 214         /* The data should be detached - so we need to supply it. */
 215         if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 216                 pr_err("PKCS#7 signature with non-detached data\n");
 217                 ret = -EBADMSG;
 218                 goto error;
 219         }
 220
 221         ret = pkcs7_verify(pkcs7, usage);
 222         if (ret < 0)
 223                 goto error;
 224
 225         if (!trusted_keys) {
 226                 trusted_keys = builtin_trusted_keys;
 227         } else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
 228 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 229                 trusted_keys = secondary_trusted_keys;
 230 #else
 231                 trusted_keys = builtin_trusted_keys;
 232 #endif
 233         } else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
 234 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 235                 trusted_keys = platform_trusted_keys;
 236 #else
 237                 trusted_keys = NULL;
 238 #endif
 239                 if (!trusted_keys) {
 240                         ret = -ENOKEY;
 241                         pr_devel("PKCS#7 platform keyring is not available\n");
 242                         goto error;
 243                 }
 244         }
 245         ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 246         if (ret < 0) {
 247                 if (ret == -ENOKEY)
 248                         pr_devel("PKCS#7 signature not signed with a trusted key\n");
 249                 goto error;
 250         }
 251
 252         if (view_content) {
 253                 size_t asn1hdrlen;
 254
 255                 ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
 256                 if (ret < 0) {
 257                         if (ret == -ENODATA)
 258                                 pr_devel("PKCS#7 message does not contain data\n");
 259                         goto error;
 260                 }
 261
 262                 ret = view_content(ctx, data, len, asn1hdrlen);
 263         }
 264
 265 error:
 266         pkcs7_free_message(pkcs7);
 267         pr_devel("<==%s() = %d\n", __func__, ret);
 268         return ret;
 269 }
 270 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 271
 272 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 273
 274 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
 275 void __init set_platform_trusted_keys(struct key *keyring)
 276 {
 277         platform_trusted_keys = keyring;
 278 }
 279 #endif