security/keys/trusted-keys/trusted_core.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2010 IBM Corporation
   4  * Copyright (c) 2019-2021, Linaro Limited
   5  *
   6  * See Documentation/security/keys/trusted-encrypted.rst
   7  */
   8
   9 #include <keys/user-type.h>
  10 #include <keys/trusted-type.h>
  11 #include <keys/trusted_tee.h>
  12 #include <keys/trusted_tpm.h>
  13 #include <linux/capability.h>
  14 #include <linux/err.h>
  15 #include <linux/init.h>
  16 #include <linux/key-type.h>
  17 #include <linux/module.h>
  18 #include <linux/parser.h>
  19 #include <linux/rcupdate.h>
  20 #include <linux/slab.h>
  21 #include <linux/static_call.h>
  22 #include <linux/string.h>
  23 #include <linux/uaccess.h>
  24
  25 static char *trusted_key_source;
  26 module_param_named(source, trusted_key_source, charp, 0);
  27 MODULE_PARM_DESC(source, "Select trusted keys source (tpm or tee)");
  28
  29 static const struct trusted_key_source trusted_key_sources[] = {
  30 #if defined(CONFIG_TCG_TPM)
  31         { "tpm", &trusted_key_tpm_ops },
  32 #endif
  33 #if defined(CONFIG_TEE)
  34         { "tee", &trusted_key_tee_ops },
  35 #endif
  36 };
  37
  38 DEFINE_STATIC_CALL_NULL(trusted_key_init, *trusted_key_sources[0].ops->init);
  39 DEFINE_STATIC_CALL_NULL(trusted_key_seal, *trusted_key_sources[0].ops->seal);
  40 DEFINE_STATIC_CALL_NULL(trusted_key_unseal,
  41                         *trusted_key_sources[0].ops->unseal);
  42 DEFINE_STATIC_CALL_NULL(trusted_key_get_random,
  43                         *trusted_key_sources[0].ops->get_random);
  44 DEFINE_STATIC_CALL_NULL(trusted_key_exit, *trusted_key_sources[0].ops->exit);
  45 static unsigned char migratable;
  46
  47 enum {
  48         Opt_err,
  49         Opt_new, Opt_load, Opt_update,
  50 };
  51
  52 static const match_table_t key_tokens = {
  53         {Opt_new, "new"},
  54         {Opt_load, "load"},
  55         {Opt_update, "update"},
  56         {Opt_err, NULL}
  57 };
  58
  59 /*
  60  * datablob_parse - parse the keyctl data and fill in the
  61  *                  payload structure
  62  *
  63  * On success returns 0, otherwise -EINVAL.
  64  */
  65 static int datablob_parse(char *datablob, struct trusted_key_payload *p)
  66 {
  67         substring_t args[MAX_OPT_ARGS];
  68         long keylen;
  69         int ret = -EINVAL;
  70         int key_cmd;
  71         char *c;
  72
  73         /* main command */
  74         c = strsep(&datablob, " \t");
  75         if (!c)
  76                 return -EINVAL;
  77         key_cmd = match_token(c, key_tokens, args);
  78         switch (key_cmd) {
  79         case Opt_new:
  80                 /* first argument is key size */
  81                 c = strsep(&datablob, " \t");
  82                 if (!c)
  83                         return -EINVAL;
  84                 ret = kstrtol(c, 10, &keylen);
  85                 if (ret < 0 || keylen < MIN_KEY_SIZE || keylen > MAX_KEY_SIZE)
  86                         return -EINVAL;
  87                 p->key_len = keylen;
  88                 ret = Opt_new;
  89                 break;
  90         case Opt_load:
  91                 /* first argument is sealed blob */
  92                 c = strsep(&datablob, " \t");
  93                 if (!c)
  94                         return -EINVAL;
  95                 p->blob_len = strlen(c) / 2;
  96                 if (p->blob_len > MAX_BLOB_SIZE)
  97                         return -EINVAL;
  98                 ret = hex2bin(p->blob, c, p->blob_len);
  99                 if (ret < 0)
 100                         return -EINVAL;
 101                 ret = Opt_load;
 102                 break;
 103         case Opt_update:
 104                 ret = Opt_update;
 105                 break;
 106         case Opt_err:
 107                 return -EINVAL;
 108         }
 109         return ret;
 110 }
 111
 112 static struct trusted_key_payload *trusted_payload_alloc(struct key *key)
 113 {
 114         struct trusted_key_payload *p = NULL;
 115         int ret;
 116
 117         ret = key_payload_reserve(key, sizeof(*p));
 118         if (ret < 0)
 119                 return p;
 120         p = kzalloc(sizeof(*p), GFP_KERNEL);
 121
 122         p->migratable = migratable;
 123
 124         return p;
 125 }
 126
 127 /*
 128  * trusted_instantiate - create a new trusted key
 129  *
 130  * Unseal an existing trusted blob or, for a new key, get a
 131  * random key, then seal and create a trusted key-type key,
 132  * adding it to the specified keyring.
 133  *
 134  * On success, return 0. Otherwise return errno.
 135  */
 136 static int trusted_instantiate(struct key *key,
 137                                struct key_preparsed_payload *prep)
 138 {
 139         struct trusted_key_payload *payload = NULL;
 140         size_t datalen = prep->datalen;
 141         char *datablob;
 142         int ret = 0;
 143         int key_cmd;
 144         size_t key_len;
 145
 146         if (datalen <= 0 || datalen > 32767 || !prep->data)
 147                 return -EINVAL;
 148
 149         datablob = kmalloc(datalen + 1, GFP_KERNEL);
 150         if (!datablob)
 151                 return -ENOMEM;
 152         memcpy(datablob, prep->data, datalen);
 153         datablob[datalen] = '\0';
 154
 155         payload = trusted_payload_alloc(key);
 156         if (!payload) {
 157                 ret = -ENOMEM;
 158                 goto out;
 159         }
 160
 161         key_cmd = datablob_parse(datablob, payload);
 162         if (key_cmd < 0) {
 163                 ret = key_cmd;
 164                 goto out;
 165         }
 166
 167         dump_payload(payload);
 168
 169         switch (key_cmd) {
 170         case Opt_load:
 171                 ret = static_call(trusted_key_unseal)(payload, datablob);
 172                 dump_payload(payload);
 173                 if (ret < 0)
 174                         pr_info("key_unseal failed (%d)\n", ret);
 175                 break;
 176         case Opt_new:
 177                 key_len = payload->key_len;
 178                 ret = static_call(trusted_key_get_random)(payload->key,
 179                                                           key_len);
 180                 if (ret < 0)
 181                         goto out;
 182
 183                 if (ret != key_len) {
 184                         pr_info("key_create failed (%d)\n", ret);
 185                         ret = -EIO;
 186                         goto out;
 187                 }
 188
 189                 ret = static_call(trusted_key_seal)(payload, datablob);
 190                 if (ret < 0)
 191                         pr_info("key_seal failed (%d)\n", ret);
 192                 break;
 193         default:
 194                 ret = -EINVAL;
 195         }
 196 out:
 197         kfree_sensitive(datablob);
 198         if (!ret)
 199                 rcu_assign_keypointer(key, payload);
 200         else
 201                 kfree_sensitive(payload);
 202         return ret;
 203 }
 204
 205 static void trusted_rcu_free(struct rcu_head *rcu)
 206 {
 207         struct trusted_key_payload *p;
 208
 209         p = container_of(rcu, struct trusted_key_payload, rcu);
 210         kfree_sensitive(p);
 211 }
 212
 213 /*
 214  * trusted_update - reseal an existing key with new PCR values
 215  */
 216 static int trusted_update(struct key *key, struct key_preparsed_payload *prep)
 217 {
 218         struct trusted_key_payload *p;
 219         struct trusted_key_payload *new_p;
 220         size_t datalen = prep->datalen;
 221         char *datablob;
 222         int ret = 0;
 223
 224         if (key_is_negative(key))
 225                 return -ENOKEY;
 226         p = key->payload.data[0];
 227         if (!p->migratable)
 228                 return -EPERM;
 229         if (datalen <= 0 || datalen > 32767 || !prep->data)
 230                 return -EINVAL;
 231
 232         datablob = kmalloc(datalen + 1, GFP_KERNEL);
 233         if (!datablob)
 234                 return -ENOMEM;
 235
 236         new_p = trusted_payload_alloc(key);
 237         if (!new_p) {
 238                 ret = -ENOMEM;
 239                 goto out;
 240         }
 241
 242         memcpy(datablob, prep->data, datalen);
 243         datablob[datalen] = '\0';
 244         ret = datablob_parse(datablob, new_p);
 245         if (ret != Opt_update) {
 246                 ret = -EINVAL;
 247                 kfree_sensitive(new_p);
 248                 goto out;
 249         }
 250
 251         /* copy old key values, and reseal with new pcrs */
 252         new_p->migratable = p->migratable;
 253         new_p->key_len = p->key_len;
 254         memcpy(new_p->key, p->key, p->key_len);
 255         dump_payload(p);
 256         dump_payload(new_p);
 257
 258         ret = static_call(trusted_key_seal)(new_p, datablob);
 259         if (ret < 0) {
 260                 pr_info("key_seal failed (%d)\n", ret);
 261                 kfree_sensitive(new_p);
 262                 goto out;
 263         }
 264
 265         rcu_assign_keypointer(key, new_p);
 266         call_rcu(&p->rcu, trusted_rcu_free);
 267 out:
 268         kfree_sensitive(datablob);
 269         return ret;
 270 }
 271
 272 /*
 273  * trusted_read - copy the sealed blob data to userspace in hex.
 274  * On success, return to userspace the trusted key datablob size.
 275  */
 276 static long trusted_read(const struct key *key, char *buffer,
 277                          size_t buflen)
 278 {
 279         const struct trusted_key_payload *p;
 280         char *bufp;
 281         int i;
 282
 283         p = dereference_key_locked(key);
 284         if (!p)
 285                 return -EINVAL;
 286
 287         if (buffer && buflen >= 2 * p->blob_len) {
 288                 bufp = buffer;
 289                 for (i = 0; i < p->blob_len; i++)
 290                         bufp = hex_byte_pack(bufp, p->blob[i]);
 291         }
 292         return 2 * p->blob_len;
 293 }
 294
 295 /*
 296  * trusted_destroy - clear and free the key's payload
 297  */
 298 static void trusted_destroy(struct key *key)
 299 {
 300         kfree_sensitive(key->payload.data[0]);
 301 }
 302
 303 struct key_type key_type_trusted = {
 304         .name = "trusted",
 305         .instantiate = trusted_instantiate,
 306         .update = trusted_update,
 307         .destroy = trusted_destroy,
 308         .describe = user_describe,
 309         .read = trusted_read,
 310 };
 311 EXPORT_SYMBOL_GPL(key_type_trusted);
 312
 313 static int __init init_trusted(void)
 314 {
 315         int i, ret = 0;
 316
 317         for (i = 0; i < ARRAY_SIZE(trusted_key_sources); i++) {
 318                 if (trusted_key_source &&
 319                     strncmp(trusted_key_source, trusted_key_sources[i].name,
 320                             strlen(trusted_key_sources[i].name)))
 321                         continue;
 322
 323                 static_call_update(trusted_key_init,
 324                                    trusted_key_sources[i].ops->init);
 325                 static_call_update(trusted_key_seal,
 326                                    trusted_key_sources[i].ops->seal);
 327                 static_call_update(trusted_key_unseal,
 328                                    trusted_key_sources[i].ops->unseal);
 329                 static_call_update(trusted_key_get_random,
 330                                    trusted_key_sources[i].ops->get_random);
 331                 static_call_update(trusted_key_exit,
 332                                    trusted_key_sources[i].ops->exit);
 333                 migratable = trusted_key_sources[i].ops->migratable;
 334
 335                 ret = static_call(trusted_key_init)();
 336                 if (!ret)
 337                         break;
 338         }
 339
 340         /*
 341          * encrypted_keys.ko depends on successful load of this module even if
 342          * trusted key implementation is not found.
 343          */
 344         if (ret == -ENODEV)
 345                 return 0;
 346
 347         return ret;
 348 }
 349
 350 static void __exit cleanup_trusted(void)
 351 {
 352         static_call(trusted_key_exit)();
 353 }
 354
 355 late_initcall(init_trusted);
 356 module_exit(cleanup_trusted);
 357
 358 MODULE_LICENSE("GPL");