fs/ecryptfs/keystore.c

   1 /**
   2  * eCryptfs: Linux filesystem encryption layer
   3  * In-kernel key management code.  Includes functions to parse and
   4  * write authentication token-related packets with the underlying
   5  * file.
   6  *
   7  * Copyright (C) 2004-2006 International Business Machines Corp.
   8  *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   9  *              Michael C. Thompson <mcthomps@us.ibm.com>
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License as
  13  * published by the Free Software Foundation; either version 2 of the
  14  * License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful, but
  17  * WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19  * General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  24  * 02111-1307, USA.
  25  */
  26
  27 #include <linux/string.h>
  28 #include <linux/sched.h>
  29 #include <linux/syscalls.h>
  30 #include <linux/pagemap.h>
  31 #include <linux/key.h>
  32 #include <linux/random.h>
  33 #include <linux/crypto.h>
  34 #include <linux/scatterlist.h>
  35 #include "ecryptfs_kernel.h"
  36
  37 /**
  38  * request_key returned an error instead of a valid key address;
  39  * determine the type of error, make appropriate log entries, and
  40  * return an error code.
  41  */
  42 int process_request_key_err(long err_code)
  43 {
  44         int rc = 0;
  45
  46         switch (err_code) {
  47         case ENOKEY:
  48                 ecryptfs_printk(KERN_WARNING, "No key\n");
  49                 rc = -ENOENT;
  50                 break;
  51         case EKEYEXPIRED:
  52                 ecryptfs_printk(KERN_WARNING, "Key expired\n");
  53                 rc = -ETIME;
  54                 break;
  55         case EKEYREVOKED:
  56                 ecryptfs_printk(KERN_WARNING, "Key revoked\n");
  57                 rc = -EINVAL;
  58                 break;
  59         default:
  60                 ecryptfs_printk(KERN_WARNING, "Unknown error code: "
  61                                 "[0x%.16x]\n", err_code);
  62                 rc = -EINVAL;
  63         }
  64         return rc;
  65 }
  66
  67 static void wipe_auth_tok_list(struct list_head *auth_tok_list_head)
  68 {
  69         struct list_head *walker;
  70         struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
  71
  72         walker = auth_tok_list_head->next;
  73         while (walker != auth_tok_list_head) {
  74                 auth_tok_list_item =
  75                     list_entry(walker, struct ecryptfs_auth_tok_list_item,
  76                                list);
  77                 walker = auth_tok_list_item->list.next;
  78                 memset(auth_tok_list_item, 0,
  79                        sizeof(struct ecryptfs_auth_tok_list_item));
  80                 kmem_cache_free(ecryptfs_auth_tok_list_item_cache,
  81                                 auth_tok_list_item);
  82         }
  83 }
  84
  85 struct kmem_cache *ecryptfs_auth_tok_list_item_cache;
  86
  87 /**
  88  * parse_packet_length
  89  * @data: Pointer to memory containing length at offset
  90  * @size: This function writes the decoded size to this memory
  91  *        address; zero on error
  92  * @length_size: The number of bytes occupied by the encoded length
  93  *
  94  * Returns Zero on success
  95  */
  96 static int parse_packet_length(unsigned char *data, size_t *size,
  97                                size_t *length_size)
  98 {
  99         int rc = 0;
 100
 101         (*length_size) = 0;
 102         (*size) = 0;
 103         if (data[0] < 192) {
 104                 /* One-byte length */
 105                 (*size) = data[0];
 106                 (*length_size) = 1;
 107         } else if (data[0] < 224) {
 108                 /* Two-byte length */
 109                 (*size) = ((data[0] - 192) * 256);
 110                 (*size) += (data[1] + 192);
 111                 (*length_size) = 2;
 112         } else if (data[0] == 255) {
 113                 /* Five-byte length; we're not supposed to see this */
 114                 ecryptfs_printk(KERN_ERR, "Five-byte packet length not "
 115                                 "supported\n");
 116                 rc = -EINVAL;
 117                 goto out;
 118         } else {
 119                 ecryptfs_printk(KERN_ERR, "Error parsing packet length\n");
 120                 rc = -EINVAL;
 121                 goto out;
 122         }
 123 out:
 124         return rc;
 125 }
 126
 127 /**
 128  * write_packet_length
 129  * @dest: The byte array target into which to write the
 130  *       length. Must have at least 5 bytes allocated.
 131  * @size: The length to write.
 132  * @packet_size_length: The number of bytes used to encode the
 133  *                      packet length is written to this address.
 134  *
 135  * Returns zero on success; non-zero on error.
 136  */
 137 static int write_packet_length(char *dest, size_t size,
 138                                size_t *packet_size_length)
 139 {
 140         int rc = 0;
 141
 142         if (size < 192) {
 143                 dest[0] = size;
 144                 (*packet_size_length) = 1;
 145         } else if (size < 65536) {
 146                 dest[0] = (((size - 192) / 256) + 192);
 147                 dest[1] = ((size - 192) % 256);
 148                 (*packet_size_length) = 2;
 149         } else {
 150                 rc = -EINVAL;
 151                 ecryptfs_printk(KERN_WARNING,
 152                                 "Unsupported packet size: [%d]\n", size);
 153         }
 154         return rc;
 155 }
 156
 157 /**
 158  * parse_tag_3_packet
 159  * @crypt_stat: The cryptographic context to modify based on packet
 160  *              contents.
 161  * @data: The raw bytes of the packet.
 162  * @auth_tok_list: eCryptfs parses packets into authentication tokens;
 163  *                 a new authentication token will be placed at the end
 164  *                 of this list for this packet.
 165  * @new_auth_tok: Pointer to a pointer to memory that this function
 166  *                allocates; sets the memory address of the pointer to
 167  *                NULL on error. This object is added to the
 168  *                auth_tok_list.
 169  * @packet_size: This function writes the size of the parsed packet
 170  *               into this memory location; zero on error.
 171  * @max_packet_size: maximum number of bytes to parse
 172  *
 173  * Returns zero on success; non-zero on error.
 174  */
 175 static int
 176 parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
 177                    unsigned char *data, struct list_head *auth_tok_list,
 178                    struct ecryptfs_auth_tok **new_auth_tok,
 179                    size_t *packet_size, size_t max_packet_size)
 180 {
 181         int rc = 0;
 182         size_t body_size;
 183         struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
 184         size_t length_size;
 185
 186         (*packet_size) = 0;
 187         (*new_auth_tok) = NULL;
 188
 189         /* we check that:
 190          *   one byte for the Tag 3 ID flag
 191          *   two bytes for the body size
 192          * do not exceed the maximum_packet_size
 193          */
 194         if (unlikely((*packet_size) + 3 > max_packet_size)) {
 195                 ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
 196                 rc = -EINVAL;
 197                 goto out;
 198         }
 199
 200         /* check for Tag 3 identifyer - one byte */
 201         if (data[(*packet_size)++] != ECRYPTFS_TAG_3_PACKET_TYPE) {
 202                 ecryptfs_printk(KERN_ERR, "Enter w/ first byte != 0x%.2x\n",
 203                                 ECRYPTFS_TAG_3_PACKET_TYPE);
 204                 rc = -EINVAL;
 205                 goto out;
 206         }
 207         /* Released: wipe_auth_tok_list called in ecryptfs_parse_packet_set or
 208          * at end of function upon failure */
 209         auth_tok_list_item =
 210             kmem_cache_alloc(ecryptfs_auth_tok_list_item_cache, GFP_KERNEL);
 211         if (!auth_tok_list_item) {
 212                 ecryptfs_printk(KERN_ERR, "Unable to allocate memory\n");
 213                 rc = -ENOMEM;
 214                 goto out;
 215         }
 216         memset(auth_tok_list_item, 0,
 217                sizeof(struct ecryptfs_auth_tok_list_item));
 218         (*new_auth_tok) = &auth_tok_list_item->auth_tok;
 219
 220         /* check for body size - one to two bytes */
 221         rc = parse_packet_length(&data[(*packet_size)], &body_size,
 222                                  &length_size);
 223         if (rc) {
 224                 ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
 225                                 "rc = [%d]\n", rc);
 226                 goto out_free;
 227         }
 228         if (unlikely(body_size < (0x05 + ECRYPTFS_SALT_SIZE))) {
 229                 ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n",
 230                                 body_size);
 231                 rc = -EINVAL;
 232                 goto out_free;
 233         }
 234         (*packet_size) += length_size;
 235
 236         /* now we know the length of the remainting Tag 3 packet size:
 237          *   5 fix bytes for: version string, cipher, S2K ID, hash algo,
 238          *                    number of hash iterations
 239          *   ECRYPTFS_SALT_SIZE bytes for salt
 240          *   body_size bytes minus the stuff above is the encrypted key size
 241          */
 242         if (unlikely((*packet_size) + body_size > max_packet_size)) {
 243                 ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
 244                 rc = -EINVAL;
 245                 goto out_free;
 246         }
 247
 248         /* There are 5 characters of additional information in the
 249          * packet */
 250         (*new_auth_tok)->session_key.encrypted_key_size =
 251                 body_size - (0x05 + ECRYPTFS_SALT_SIZE);
 252         ecryptfs_printk(KERN_DEBUG, "Encrypted key size = [%d]\n",
 253                         (*new_auth_tok)->session_key.encrypted_key_size);
 254
 255         /* Version 4 (from RFC2440) - one byte */
 256         if (unlikely(data[(*packet_size)++] != 0x04)) {
 257                 ecryptfs_printk(KERN_DEBUG, "Unknown version number "
 258                                 "[%d]\n", data[(*packet_size) - 1]);
 259                 rc = -EINVAL;
 260                 goto out_free;
 261         }
 262
 263         /* cipher - one byte */
 264         ecryptfs_cipher_code_to_string(crypt_stat->cipher,
 265                                        (u16)data[(*packet_size)]);
 266         /* A little extra work to differentiate among the AES key
 267          * sizes; see RFC2440 */
 268         switch(data[(*packet_size)++]) {
 269         case RFC2440_CIPHER_AES_192:
 270                 crypt_stat->key_size = 24;
 271                 break;
 272         default:
 273                 crypt_stat->key_size =
 274                         (*new_auth_tok)->session_key.encrypted_key_size;
 275         }
 276         ecryptfs_init_crypt_ctx(crypt_stat);
 277         /* S2K identifier 3 (from RFC2440) */
 278         if (unlikely(data[(*packet_size)++] != 0x03)) {
 279                 ecryptfs_printk(KERN_ERR, "Only S2K ID 3 is currently "
 280                                 "supported\n");
 281                 rc = -ENOSYS;
 282                 goto out_free;
 283         }
 284
 285         /* TODO: finish the hash mapping */
 286         /* hash algorithm - one byte */
 287         switch (data[(*packet_size)++]) {
 288         case 0x01: /* See RFC2440 for these numbers and their mappings */
 289                 /* Choose MD5 */
 290                 /* salt - ECRYPTFS_SALT_SIZE bytes */
 291                 memcpy((*new_auth_tok)->token.password.salt,
 292                        &data[(*packet_size)], ECRYPTFS_SALT_SIZE);
 293                 (*packet_size) += ECRYPTFS_SALT_SIZE;
 294
 295                 /* This conversion was taken straight from RFC2440 */
 296                 /* number of hash iterations - one byte */
 297                 (*new_auth_tok)->token.password.hash_iterations =
 298                         ((u32) 16 + (data[(*packet_size)] & 15))
 299                                 << ((data[(*packet_size)] >> 4) + 6);
 300                 (*packet_size)++;
 301
 302                 /* encrypted session key -
 303                  *   (body_size-5-ECRYPTFS_SALT_SIZE) bytes */
 304                 memcpy((*new_auth_tok)->session_key.encrypted_key,
 305                        &data[(*packet_size)],
 306                        (*new_auth_tok)->session_key.encrypted_key_size);
 307                 (*packet_size) +=
 308                         (*new_auth_tok)->session_key.encrypted_key_size;
 309                 (*new_auth_tok)->session_key.flags &=
 310                         ~ECRYPTFS_CONTAINS_DECRYPTED_KEY;
 311                 (*new_auth_tok)->session_key.flags |=
 312                         ECRYPTFS_CONTAINS_ENCRYPTED_KEY;
 313                 (*new_auth_tok)->token.password.hash_algo = 0x01;
 314                 break;
 315         default:
 316                 ecryptfs_printk(KERN_ERR, "Unsupported hash algorithm: "
 317                                 "[%d]\n", data[(*packet_size) - 1]);
 318                 rc = -ENOSYS;
 319                 goto out_free;
 320         }
 321         (*new_auth_tok)->token_type = ECRYPTFS_PASSWORD;
 322         /* TODO: Parametarize; we might actually want userspace to
 323          * decrypt the session key. */
 324         ECRYPTFS_CLEAR_FLAG((*new_auth_tok)->session_key.flags,
 325                             ECRYPTFS_USERSPACE_SHOULD_TRY_TO_DECRYPT);
 326         ECRYPTFS_CLEAR_FLAG((*new_auth_tok)->session_key.flags,
 327                             ECRYPTFS_USERSPACE_SHOULD_TRY_TO_ENCRYPT);
 328         list_add(&auth_tok_list_item->list, auth_tok_list);
 329         goto out;
 330 out_free:
 331         (*new_auth_tok) = NULL;
 332         memset(auth_tok_list_item, 0,
 333                sizeof(struct ecryptfs_auth_tok_list_item));
 334         kmem_cache_free(ecryptfs_auth_tok_list_item_cache,
 335                         auth_tok_list_item);
 336 out:
 337         if (rc)
 338                 (*packet_size) = 0;
 339         return rc;
 340 }
 341
 342 /**
 343  * parse_tag_11_packet
 344  * @data: The raw bytes of the packet
 345  * @contents: This function writes the data contents of the literal
 346  *            packet into this memory location
 347  * @max_contents_bytes: The maximum number of bytes that this function
 348  *                      is allowed to write into contents
 349  * @tag_11_contents_size: This function writes the size of the parsed
 350  *                        contents into this memory location; zero on
 351  *                        error
 352  * @packet_size: This function writes the size of the parsed packet
 353  *               into this memory location; zero on error
 354  * @max_packet_size: maximum number of bytes to parse
 355  *
 356  * Returns zero on success; non-zero on error.
 357  */
 358 static int
 359 parse_tag_11_packet(unsigned char *data, unsigned char *contents,
 360                     size_t max_contents_bytes, size_t *tag_11_contents_size,
 361                     size_t *packet_size, size_t max_packet_size)
 362 {
 363         int rc = 0;
 364         size_t body_size;
 365         size_t length_size;
 366
 367         (*packet_size) = 0;
 368         (*tag_11_contents_size) = 0;
 369
 370         /* check that:
 371          *   one byte for the Tag 11 ID flag
 372          *   two bytes for the Tag 11 length
 373          * do not exceed the maximum_packet_size
 374          */
 375         if (unlikely((*packet_size) + 3 > max_packet_size)) {
 376                 ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
 377                 rc = -EINVAL;
 378                 goto out;
 379         }
 380
 381         /* check for Tag 11 identifyer - one byte */
 382         if (data[(*packet_size)++] != ECRYPTFS_TAG_11_PACKET_TYPE) {
 383                 ecryptfs_printk(KERN_WARNING,
 384                                 "Invalid tag 11 packet format\n");
 385                 rc = -EINVAL;
 386                 goto out;
 387         }
 388
 389         /* get Tag 11 content length - one or two bytes */
 390         rc = parse_packet_length(&data[(*packet_size)], &body_size,
 391                                  &length_size);
 392         if (rc) {
 393                 ecryptfs_printk(KERN_WARNING,
 394                                 "Invalid tag 11 packet format\n");
 395                 goto out;
 396         }
 397         (*packet_size) += length_size;
 398
 399         if (body_size < 13) {
 400                 ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n",
 401                                 body_size);
 402                 rc = -EINVAL;
 403                 goto out;
 404         }
 405         /* We have 13 bytes of surrounding packet values */
 406         (*tag_11_contents_size) = (body_size - 13);
 407
 408         /* now we know the length of the remainting Tag 11 packet size:
 409          *   14 fix bytes for: special flag one, special flag two,
 410          *                     12 skipped bytes
 411          *   body_size bytes minus the stuff above is the Tag 11 content
 412          */
 413         /* FIXME why is the body size one byte smaller than the actual
 414          * size of the body?
 415          * this seems to be an error here as well as in
 416          * write_tag_11_packet() */
 417         if (unlikely((*packet_size) + body_size + 1 > max_packet_size)) {
 418                 ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
 419                 rc = -EINVAL;
 420                 goto out;
 421         }
 422
 423         /* special flag one - one byte */
 424         if (data[(*packet_size)++] != 0x62) {
 425                 ecryptfs_printk(KERN_WARNING, "Unrecognizable packet\n");
 426                 rc = -EINVAL;
 427                 goto out;
 428         }
 429
 430         /* special flag two - one byte */
 431         if (data[(*packet_size)++] != 0x08) {
 432                 ecryptfs_printk(KERN_WARNING, "Unrecognizable packet\n");
 433                 rc = -EINVAL;
 434                 goto out;
 435         }
 436
 437         /* skip the next 12 bytes */
 438         (*packet_size) += 12; /* We don't care about the filename or
 439                                * the timestamp */
 440
 441         /* get the Tag 11 contents - tag_11_contents_size bytes */
 442         memcpy(contents, &data[(*packet_size)], (*tag_11_contents_size));
 443         (*packet_size) += (*tag_11_contents_size);
 444
 445 out:
 446         if (rc) {
 447                 (*packet_size) = 0;
 448                 (*tag_11_contents_size) = 0;
 449         }
 450         return rc;
 451 }
 452
 453 /**
 454  * decrypt_session_key - Decrypt the session key with the given auth_tok.
 455  *
 456  * Returns Zero on success; non-zero error otherwise.
 457  */
 458 static int decrypt_session_key(struct ecryptfs_auth_tok *auth_tok,
 459                                struct ecryptfs_crypt_stat *crypt_stat)
 460 {
 461         struct ecryptfs_password *password_s_ptr;
 462         struct scatterlist src_sg[2], dst_sg[2];
 463         struct mutex *tfm_mutex = NULL;
 464         /* TODO: Use virt_to_scatterlist for these */
 465         char *encrypted_session_key;
 466         char *session_key;
 467         struct blkcipher_desc desc = {
 468                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
 469         };
 470         int rc = 0;
 471
 472         password_s_ptr = &auth_tok->token.password;
 473         if (ECRYPTFS_CHECK_FLAG(password_s_ptr->flags,
 474                                 ECRYPTFS_SESSION_KEY_ENCRYPTION_KEY_SET))
 475                 ecryptfs_printk(KERN_DEBUG, "Session key encryption key "
 476                                 "set; skipping key generation\n");
 477         ecryptfs_printk(KERN_DEBUG, "Session key encryption key (size [%d])"
 478                         ":\n",
 479                         password_s_ptr->session_key_encryption_key_bytes);
 480         if (ecryptfs_verbosity > 0)
 481                 ecryptfs_dump_hex(password_s_ptr->session_key_encryption_key,
 482                                   password_s_ptr->
 483                                   session_key_encryption_key_bytes);
 484         if (!strcmp(crypt_stat->cipher,
 485                     crypt_stat->mount_crypt_stat->global_default_cipher_name)
 486             && crypt_stat->mount_crypt_stat->global_key_tfm) {
 487                 desc.tfm = crypt_stat->mount_crypt_stat->global_key_tfm;
 488                 tfm_mutex = &crypt_stat->mount_crypt_stat->global_key_tfm_mutex;
 489         } else {
 490                 char *full_alg_name;
 491
 492                 rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
 493                                                             crypt_stat->cipher,
 494                                                             "ecb");
 495                 if (rc)
 496                         goto out;
 497                 desc.tfm = crypto_alloc_blkcipher(full_alg_name, 0,
 498                                                   CRYPTO_ALG_ASYNC);
 499                 kfree(full_alg_name);
 500                 if (IS_ERR(desc.tfm)) {
 501                         rc = PTR_ERR(desc.tfm);
 502                         printk(KERN_ERR "Error allocating crypto context; "
 503                                "rc = [%d]\n", rc);
 504                         goto out;
 505                 }
 506                 crypto_blkcipher_set_flags(desc.tfm, CRYPTO_TFM_REQ_WEAK_KEY);
 507         }
 508         if (tfm_mutex)
 509                 mutex_lock(tfm_mutex);
 510         rc = crypto_blkcipher_setkey(desc.tfm,
 511                                      password_s_ptr->session_key_encryption_key,
 512                                      crypt_stat->key_size);
 513         if (rc < 0) {
 514                 printk(KERN_ERR "Error setting key for crypto context\n");
 515                 rc = -EINVAL;
 516                 goto out_free_tfm;
 517         }
 518         /* TODO: virt_to_scatterlist */
 519         encrypted_session_key = (char *)__get_free_page(GFP_KERNEL);
 520         if (!encrypted_session_key) {
 521                 ecryptfs_printk(KERN_ERR, "Out of memory\n");
 522                 rc = -ENOMEM;
 523                 goto out_free_tfm;
 524         }
 525         session_key = (char *)__get_free_page(GFP_KERNEL);
 526         if (!session_key) {
 527                 kfree(encrypted_session_key);
 528                 ecryptfs_printk(KERN_ERR, "Out of memory\n");
 529                 rc = -ENOMEM;
 530                 goto out_free_tfm;
 531         }
 532         memcpy(encrypted_session_key, auth_tok->session_key.encrypted_key,
 533                auth_tok->session_key.encrypted_key_size);
 534         src_sg[0].page = virt_to_page(encrypted_session_key);
 535         src_sg[0].offset = 0;
 536         BUG_ON(auth_tok->session_key.encrypted_key_size > PAGE_CACHE_SIZE);
 537         src_sg[0].length = auth_tok->session_key.encrypted_key_size;
 538         dst_sg[0].page = virt_to_page(session_key);
 539         dst_sg[0].offset = 0;
 540         auth_tok->session_key.decrypted_key_size =
 541             auth_tok->session_key.encrypted_key_size;
 542         dst_sg[0].length = auth_tok->session_key.encrypted_key_size;
 543         rc = crypto_blkcipher_decrypt(&desc, dst_sg, src_sg,
 544                                       auth_tok->session_key.encrypted_key_size);
 545         if (rc) {
 546                 printk(KERN_ERR "Error decrypting; rc = [%d]\n", rc);
 547                 goto out_free_memory;
 548         }
 549         auth_tok->session_key.decrypted_key_size =
 550             auth_tok->session_key.encrypted_key_size;
 551         memcpy(auth_tok->session_key.decrypted_key, session_key,
 552                auth_tok->session_key.decrypted_key_size);
 553         auth_tok->session_key.flags |= ECRYPTFS_CONTAINS_DECRYPTED_KEY;
 554         memcpy(crypt_stat->key, auth_tok->session_key.decrypted_key,
 555                auth_tok->session_key.decrypted_key_size);
 556         ECRYPTFS_SET_FLAG(crypt_stat->flags, ECRYPTFS_KEY_VALID);
 557         ecryptfs_printk(KERN_DEBUG, "Decrypted session key:\n");
 558         if (ecryptfs_verbosity > 0)
 559                 ecryptfs_dump_hex(crypt_stat->key,
 560                                   crypt_stat->key_size);
 561 out_free_memory:
 562         memset(encrypted_session_key, 0, PAGE_CACHE_SIZE);
 563         free_page((unsigned long)encrypted_session_key);
 564         memset(session_key, 0, PAGE_CACHE_SIZE);
 565         free_page((unsigned long)session_key);
 566 out_free_tfm:
 567         if (tfm_mutex)
 568                 mutex_unlock(tfm_mutex);
 569         else
 570                 crypto_free_blkcipher(desc.tfm);
 571 out:
 572         return rc;
 573 }
 574
 575 /**
 576  * ecryptfs_parse_packet_set
 577  * @dest: The header page in memory
 578  * @version: Version of file format, to guide parsing behavior
 579  *
 580  * Get crypt_stat to have the file's session key if the requisite key
 581  * is available to decrypt the session key.
 582  *
 583  * Returns Zero if a valid authentication token was retrieved and
 584  * processed; negative value for file not encrypted or for error
 585  * conditions.
 586  */
 587 int ecryptfs_parse_packet_set(struct ecryptfs_crypt_stat *crypt_stat,
 588                               unsigned char *src,
 589                               struct dentry *ecryptfs_dentry)
 590 {
 591         size_t i = 0;
 592         int rc = 0;
 593         size_t found_auth_tok = 0;
 594         size_t next_packet_is_auth_tok_packet;
 595         char sig[ECRYPTFS_SIG_SIZE_HEX];
 596         struct list_head auth_tok_list;
 597         struct list_head *walker;
 598         struct ecryptfs_auth_tok *chosen_auth_tok = NULL;
 599         struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
 600                 &ecryptfs_superblock_to_private(
 601                         ecryptfs_dentry->d_sb)->mount_crypt_stat;
 602         struct ecryptfs_auth_tok *candidate_auth_tok = NULL;
 603         size_t packet_size;
 604         struct ecryptfs_auth_tok *new_auth_tok;
 605         unsigned char sig_tmp_space[ECRYPTFS_SIG_SIZE];
 606         size_t tag_11_contents_size;
 607         size_t tag_11_packet_size;
 608
 609         INIT_LIST_HEAD(&auth_tok_list);
 610         /* Parse the header to find as many packets as we can, these will be
 611          * added the our &auth_tok_list */
 612         next_packet_is_auth_tok_packet = 1;
 613         while (next_packet_is_auth_tok_packet) {
 614                 size_t max_packet_size = ((PAGE_CACHE_SIZE - 8) - i);
 615
 616                 switch (src[i]) {
 617                 case ECRYPTFS_TAG_3_PACKET_TYPE:
 618                         rc = parse_tag_3_packet(crypt_stat,
 619                                                 (unsigned char *)&src[i],
 620                                                 &auth_tok_list, &new_auth_tok,
 621                                                 &packet_size, max_packet_size);
 622                         if (rc) {
 623                                 ecryptfs_printk(KERN_ERR, "Error parsing "
 624                                                 "tag 3 packet\n");
 625                                 rc = -EIO;
 626                                 goto out_wipe_list;
 627                         }
 628                         i += packet_size;
 629                         rc = parse_tag_11_packet((unsigned char *)&src[i],
 630                                                  sig_tmp_space,
 631                                                  ECRYPTFS_SIG_SIZE,
 632                                                  &tag_11_contents_size,
 633                                                  &tag_11_packet_size,
 634                                                  max_packet_size);
 635                         if (rc) {
 636                                 ecryptfs_printk(KERN_ERR, "No valid "
 637                                                 "(ecryptfs-specific) literal "
 638                                                 "packet containing "
 639                                                 "authentication token "
 640                                                 "signature found after "
 641                                                 "tag 3 packet\n");
 642                                 rc = -EIO;
 643                                 goto out_wipe_list;
 644                         }
 645                         i += tag_11_packet_size;
 646                         if (ECRYPTFS_SIG_SIZE != tag_11_contents_size) {
 647                                 ecryptfs_printk(KERN_ERR, "Expected "
 648                                                 "signature of size [%d]; "
 649                                                 "read size [%d]\n",
 650                                                 ECRYPTFS_SIG_SIZE,
 651                                                 tag_11_contents_size);
 652                                 rc = -EIO;
 653                                 goto out_wipe_list;
 654                         }
 655                         ecryptfs_to_hex(new_auth_tok->token.password.signature,
 656                                         sig_tmp_space, tag_11_contents_size);
 657                         new_auth_tok->token.password.signature[
 658                                 ECRYPTFS_PASSWORD_SIG_SIZE] = '\0';
 659                         ECRYPTFS_SET_FLAG(crypt_stat->flags,
 660                                           ECRYPTFS_ENCRYPTED);
 661                         break;
 662                 case ECRYPTFS_TAG_11_PACKET_TYPE:
 663                         ecryptfs_printk(KERN_WARNING, "Invalid packet set "
 664                                         "(Tag 11 not allowed by itself)\n");
 665                         rc = -EIO;
 666                         goto out_wipe_list;
 667                         break;
 668                 default:
 669                         ecryptfs_printk(KERN_DEBUG, "No packet at offset "
 670                                         "[%d] of the file header; hex value of "
 671                                         "character is [0x%.2x]\n", i, src[i]);
 672                         next_packet_is_auth_tok_packet = 0;
 673                 }
 674         }
 675         if (list_empty(&auth_tok_list)) {
 676                 rc = -EINVAL; /* Do not support non-encrypted files in
 677                                * the 0.1 release */
 678                 goto out;
 679         }
 680         /* If we have a global auth tok, then we should try to use
 681          * it */
 682         if (mount_crypt_stat->global_auth_tok) {
 683                 memcpy(sig, mount_crypt_stat->global_auth_tok_sig,
 684                        ECRYPTFS_SIG_SIZE_HEX);
 685                 chosen_auth_tok = mount_crypt_stat->global_auth_tok;
 686         } else
 687                 BUG(); /* We should always have a global auth tok in
 688                         * the 0.1 release */
 689         /* Scan list to see if our chosen_auth_tok works */
 690         list_for_each(walker, &auth_tok_list) {
 691                 struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
 692                 auth_tok_list_item =
 693                     list_entry(walker, struct ecryptfs_auth_tok_list_item,
 694                                list);
 695                 candidate_auth_tok = &auth_tok_list_item->auth_tok;
 696                 if (unlikely(ecryptfs_verbosity > 0)) {
 697                         ecryptfs_printk(KERN_DEBUG,
 698                                         "Considering cadidate auth tok:\n");
 699                         ecryptfs_dump_auth_tok(candidate_auth_tok);
 700                 }
 701                 /* TODO: Replace ECRYPTFS_SIG_SIZE_HEX w/ dynamic value */
 702                 if (candidate_auth_tok->token_type == ECRYPTFS_PASSWORD
 703                     && !strncmp(candidate_auth_tok->token.password.signature,
 704                                 sig, ECRYPTFS_SIG_SIZE_HEX)) {
 705                         found_auth_tok = 1;
 706                         goto leave_list;
 707                         /* TODO: Transfer the common salt into the
 708                          * crypt_stat salt */
 709                 }
 710         }
 711 leave_list:
 712         if (!found_auth_tok) {
 713                 ecryptfs_printk(KERN_ERR, "Could not find authentication "
 714                                 "token on temporary list for sig [%.*s]\n",
 715                                 ECRYPTFS_SIG_SIZE_HEX, sig);
 716                 rc = -EIO;
 717                 goto out_wipe_list;
 718         } else {
 719                 memcpy(&(candidate_auth_tok->token.password),
 720                        &(chosen_auth_tok->token.password),
 721                        sizeof(struct ecryptfs_password));
 722                 rc = decrypt_session_key(candidate_auth_tok, crypt_stat);
 723                 if (rc) {
 724                         ecryptfs_printk(KERN_ERR, "Error decrypting the "
 725                                         "session key\n");
 726                         goto out_wipe_list;
 727                 }
 728                 rc = ecryptfs_compute_root_iv(crypt_stat);
 729                 if (rc) {
 730                         ecryptfs_printk(KERN_ERR, "Error computing "
 731                                         "the root IV\n");
 732                         goto out_wipe_list;
 733                 }
 734         }
 735         rc = ecryptfs_init_crypt_ctx(crypt_stat);
 736         if (rc) {
 737                 ecryptfs_printk(KERN_ERR, "Error initializing crypto "
 738                                 "context for cipher [%s]; rc = [%d]\n",
 739                                 crypt_stat->cipher, rc);
 740         }
 741 out_wipe_list:
 742         wipe_auth_tok_list(&auth_tok_list);
 743 out:
 744         return rc;
 745 }
 746
 747 /**
 748  * write_tag_11_packet
 749  * @dest: Target into which Tag 11 packet is to be written
 750  * @max: Maximum packet length
 751  * @contents: Byte array of contents to copy in
 752  * @contents_length: Number of bytes in contents
 753  * @packet_length: Length of the Tag 11 packet written; zero on error
 754  *
 755  * Returns zero on success; non-zero on error.
 756  */
 757 static int
 758 write_tag_11_packet(char *dest, int max, char *contents, size_t contents_length,
 759                     size_t *packet_length)
 760 {
 761         int rc = 0;
 762         size_t packet_size_length;
 763
 764         (*packet_length) = 0;
 765         if ((13 + contents_length) > max) {
 766                 rc = -EINVAL;
 767                 ecryptfs_printk(KERN_ERR, "Packet length larger than "
 768                                 "maximum allowable\n");
 769                 goto out;
 770         }
 771         /* General packet header */
 772         /* Packet tag */
 773         dest[(*packet_length)++] = ECRYPTFS_TAG_11_PACKET_TYPE;
 774         /* Packet length */
 775         rc = write_packet_length(&dest[(*packet_length)],
 776                                  (13 + contents_length), &packet_size_length);
 777         if (rc) {
 778                 ecryptfs_printk(KERN_ERR, "Error generating tag 11 packet "
 779                                 "header; cannot generate packet length\n");
 780                 goto out;
 781         }
 782         (*packet_length) += packet_size_length;
 783         /* Tag 11 specific */
 784         /* One-octet field that describes how the data is formatted */
 785         dest[(*packet_length)++] = 0x62; /* binary data */
 786         /* One-octet filename length followed by filename */
 787         dest[(*packet_length)++] = 8;
 788         memcpy(&dest[(*packet_length)], "_CONSOLE", 8);
 789         (*packet_length) += 8;
 790         /* Four-octet number indicating modification date */
 791         memset(&dest[(*packet_length)], 0x00, 4);
 792         (*packet_length) += 4;
 793         /* Remainder is literal data */
 794         memcpy(&dest[(*packet_length)], contents, contents_length);
 795         (*packet_length) += contents_length;
 796  out:
 797         if (rc)
 798                 (*packet_length) = 0;
 799         return rc;
 800 }
 801
 802 /**
 803  * write_tag_3_packet
 804  * @dest: Buffer into which to write the packet
 805  * @max: Maximum number of bytes that can be written
 806  * @auth_tok: Authentication token
 807  * @crypt_stat: The cryptographic context
 808  * @key_rec: encrypted key
 809  * @packet_size: This function will write the number of bytes that end
 810  *               up constituting the packet; set to zero on error
 811  *
 812  * Returns zero on success; non-zero on error.
 813  */
 814 static int
 815 write_tag_3_packet(char *dest, size_t max, struct ecryptfs_auth_tok *auth_tok,
 816                    struct ecryptfs_crypt_stat *crypt_stat,
 817                    struct ecryptfs_key_record *key_rec, size_t *packet_size)
 818 {
 819         size_t i;
 820         size_t signature_is_valid = 0;
 821         size_t encrypted_session_key_valid = 0;
 822         char session_key_encryption_key[ECRYPTFS_MAX_KEY_BYTES];
 823         struct scatterlist dest_sg[2];
 824         struct scatterlist src_sg[2];
 825         struct mutex *tfm_mutex = NULL;
 826         size_t key_rec_size;
 827         size_t packet_size_length;
 828         size_t cipher_code;
 829         struct blkcipher_desc desc = {
 830                 .tfm = NULL,
 831                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
 832         };
 833         int rc = 0;
 834
 835         (*packet_size) = 0;
 836         /* Check for a valid signature on the auth_tok */
 837         for (i = 0; i < ECRYPTFS_SIG_SIZE_HEX; i++)
 838                 signature_is_valid |= auth_tok->token.password.signature[i];
 839         if (!signature_is_valid)
 840                 BUG();
 841         ecryptfs_from_hex((*key_rec).sig, auth_tok->token.password.signature,
 842                           ECRYPTFS_SIG_SIZE);
 843         encrypted_session_key_valid = 0;
 844         for (i = 0; i < crypt_stat->key_size; i++)
 845                 encrypted_session_key_valid |=
 846                         auth_tok->session_key.encrypted_key[i];
 847         if (encrypted_session_key_valid) {
 848                 memcpy((*key_rec).enc_key,
 849                        auth_tok->session_key.encrypted_key,
 850                        auth_tok->session_key.encrypted_key_size);
 851                 goto encrypted_session_key_set;
 852         }
 853         if (auth_tok->session_key.encrypted_key_size == 0)
 854                 auth_tok->session_key.encrypted_key_size =
 855                         crypt_stat->key_size;
 856         if (crypt_stat->key_size == 24
 857             && strcmp("aes", crypt_stat->cipher) == 0) {
 858                 memset((crypt_stat->key + 24), 0, 8);
 859                 auth_tok->session_key.encrypted_key_size = 32;
 860         }
 861         (*key_rec).enc_key_size =
 862                 auth_tok->session_key.encrypted_key_size;
 863         if (ECRYPTFS_CHECK_FLAG(auth_tok->token.password.flags,
 864                                 ECRYPTFS_SESSION_KEY_ENCRYPTION_KEY_SET)) {
 865                 ecryptfs_printk(KERN_DEBUG, "Using previously generated "
 866                                 "session key encryption key of size [%d]\n",
 867                                 auth_tok->token.password.
 868                                 session_key_encryption_key_bytes);
 869                 memcpy(session_key_encryption_key,
 870                        auth_tok->token.password.session_key_encryption_key,
 871                        crypt_stat->key_size);
 872                 ecryptfs_printk(KERN_DEBUG,
 873                                 "Cached session key " "encryption key: \n");
 874                 if (ecryptfs_verbosity > 0)
 875                         ecryptfs_dump_hex(session_key_encryption_key, 16);
 876         }
 877         if (unlikely(ecryptfs_verbosity > 0)) {
 878                 ecryptfs_printk(KERN_DEBUG, "Session key encryption key:\n");
 879                 ecryptfs_dump_hex(session_key_encryption_key, 16);
 880         }
 881         rc = virt_to_scatterlist(crypt_stat->key,
 882                                  (*key_rec).enc_key_size, src_sg, 2);
 883         if (!rc) {
 884                 ecryptfs_printk(KERN_ERR, "Error generating scatterlist "
 885                                 "for crypt_stat session key\n");
 886                 rc = -ENOMEM;
 887                 goto out;
 888         }
 889         rc = virt_to_scatterlist((*key_rec).enc_key,
 890                                  (*key_rec).enc_key_size, dest_sg, 2);
 891         if (!rc) {
 892                 ecryptfs_printk(KERN_ERR, "Error generating scatterlist "
 893                                 "for crypt_stat encrypted session key\n");
 894                 rc = -ENOMEM;
 895                 goto out;
 896         }
 897         if (!strcmp(crypt_stat->cipher,
 898                     crypt_stat->mount_crypt_stat->global_default_cipher_name)
 899             && crypt_stat->mount_crypt_stat->global_key_tfm) {
 900                 desc.tfm = crypt_stat->mount_crypt_stat->global_key_tfm;
 901                 tfm_mutex = &crypt_stat->mount_crypt_stat->global_key_tfm_mutex;
 902         } else {
 903                 char *full_alg_name;
 904
 905                 rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
 906                                                             crypt_stat->cipher,
 907                                                             "ecb");
 908                 if (rc)
 909                         goto out;
 910                 desc.tfm = crypto_alloc_blkcipher(full_alg_name, 0,
 911                                                   CRYPTO_ALG_ASYNC);
 912                 kfree(full_alg_name);
 913                 if (IS_ERR(desc.tfm)) {
 914                         rc = PTR_ERR(desc.tfm);
 915                         ecryptfs_printk(KERN_ERR, "Could not initialize crypto "
 916                                         "context for cipher [%s]; rc = [%d]\n",
 917                                         crypt_stat->cipher, rc);
 918                         goto out;
 919                 }
 920                 crypto_blkcipher_set_flags(desc.tfm, CRYPTO_TFM_REQ_WEAK_KEY);
 921         }
 922         if (tfm_mutex)
 923                 mutex_lock(tfm_mutex);
 924         rc = crypto_blkcipher_setkey(desc.tfm, session_key_encryption_key,
 925                                      crypt_stat->key_size);
 926         if (rc < 0) {
 927                 if (tfm_mutex)
 928                         mutex_unlock(tfm_mutex);
 929                 ecryptfs_printk(KERN_ERR, "Error setting key for crypto "
 930                                 "context; rc = [%d]\n", rc);
 931                 goto out;
 932         }
 933         rc = 0;
 934         ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes of the key\n",
 935                         crypt_stat->key_size);
 936         rc = crypto_blkcipher_encrypt(&desc, dest_sg, src_sg,
 937                                       (*key_rec).enc_key_size);
 938         if (rc) {
 939                 printk(KERN_ERR "Error encrypting; rc = [%d]\n", rc);
 940                 goto out;
 941         }
 942         if (tfm_mutex)
 943                 mutex_unlock(tfm_mutex);
 944         ecryptfs_printk(KERN_DEBUG, "This should be the encrypted key:\n");
 945         if (ecryptfs_verbosity > 0)
 946                 ecryptfs_dump_hex((*key_rec).enc_key,
 947                                   (*key_rec).enc_key_size);
 948 encrypted_session_key_set:
 949         /* Now we have a valid key_rec.  Append it to the
 950          * key_rec set. */
 951         key_rec_size = (sizeof(struct ecryptfs_key_record)
 952                         - ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES
 953                         + ((*key_rec).enc_key_size));
 954         /* TODO: Include a packet size limit as a parameter to this
 955          * function once we have multi-packet headers (for versions
 956          * later than 0.1 */
 957         if (key_rec_size >= ECRYPTFS_MAX_KEYSET_SIZE) {
 958                 ecryptfs_printk(KERN_ERR, "Keyset too large\n");
 959                 rc = -EINVAL;
 960                 goto out;
 961         }
 962         /* TODO: Packet size limit */
 963         /* We have 5 bytes of surrounding packet data */
 964         if ((0x05 + ECRYPTFS_SALT_SIZE
 965              + (*key_rec).enc_key_size) >= max) {
 966                 ecryptfs_printk(KERN_ERR, "Authentication token is too "
 967                                 "large\n");
 968                 rc = -EINVAL;
 969                 goto out;
 970         }
 971         /* This format is inspired by OpenPGP; see RFC 2440
 972          * packet tag 3 */
 973         dest[(*packet_size)++] = ECRYPTFS_TAG_3_PACKET_TYPE;
 974         /* ver+cipher+s2k+hash+salt+iter+enc_key */
 975         rc = write_packet_length(&dest[(*packet_size)],
 976                                  (0x05 + ECRYPTFS_SALT_SIZE
 977                                   + (*key_rec).enc_key_size),
 978                                  &packet_size_length);
 979         if (rc) {
 980                 ecryptfs_printk(KERN_ERR, "Error generating tag 3 packet "
 981                                 "header; cannot generate packet length\n");
 982                 goto out;
 983         }
 984         (*packet_size) += packet_size_length;
 985         dest[(*packet_size)++] = 0x04; /* version 4 */
 986         cipher_code = ecryptfs_code_for_cipher_string(crypt_stat);
 987         if (cipher_code == 0) {
 988                 ecryptfs_printk(KERN_WARNING, "Unable to generate code for "
 989                                 "cipher [%s]\n", crypt_stat->cipher);
 990                 rc = -EINVAL;
 991                 goto out;
 992         }
 993         dest[(*packet_size)++] = cipher_code;
 994         dest[(*packet_size)++] = 0x03;  /* S2K */
 995         dest[(*packet_size)++] = 0x01;  /* MD5 (TODO: parameterize) */
 996         memcpy(&dest[(*packet_size)], auth_tok->token.password.salt,
 997                ECRYPTFS_SALT_SIZE);
 998         (*packet_size) += ECRYPTFS_SALT_SIZE;   /* salt */
 999         dest[(*packet_size)++] = 0x60;  /* hash iterations (65536) */
1000         memcpy(&dest[(*packet_size)], (*key_rec).enc_key,
1001                (*key_rec).enc_key_size);
1002         (*packet_size) += (*key_rec).enc_key_size;
1003 out:
1004         if (desc.tfm && !tfm_mutex)
1005                 crypto_free_blkcipher(desc.tfm);
1006         if (rc)
1007                 (*packet_size) = 0;
1008         return rc;
1009 }
1010
1011 /**
1012  * ecryptfs_generate_key_packet_set
1013  * @dest: Virtual address from which to write the key record set
1014  * @crypt_stat: The cryptographic context from which the
1015  *              authentication tokens will be retrieved
1016  * @ecryptfs_dentry: The dentry, used to retrieve the mount crypt stat
1017  *                   for the global parameters
1018  * @len: The amount written
1019  * @max: The maximum amount of data allowed to be written
1020  *
1021  * Generates a key packet set and writes it to the virtual address
1022  * passed in.
1023  *
1024  * Returns zero on success; non-zero on error.
1025  */
1026 int
1027 ecryptfs_generate_key_packet_set(char *dest_base,
1028                                  struct ecryptfs_crypt_stat *crypt_stat,
1029                                  struct dentry *ecryptfs_dentry, size_t *len,
1030                                  size_t max)
1031 {
1032         int rc = 0;
1033         struct ecryptfs_auth_tok *auth_tok;
1034         struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
1035                 &ecryptfs_superblock_to_private(
1036                         ecryptfs_dentry->d_sb)->mount_crypt_stat;
1037         size_t written;
1038         struct ecryptfs_key_record key_rec;
1039
1040         (*len) = 0;
1041         if (mount_crypt_stat->global_auth_tok) {
1042                 auth_tok = mount_crypt_stat->global_auth_tok;
1043                 if (auth_tok->token_type == ECRYPTFS_PASSWORD) {
1044                         rc = write_tag_3_packet((dest_base + (*len)),
1045                                                 max, auth_tok,
1046                                                 crypt_stat, &key_rec,
1047                                                 &written);
1048                         if (rc) {
1049                                 ecryptfs_printk(KERN_WARNING, "Error "
1050                                                 "writing tag 3 packet\n");
1051                                 goto out;
1052                         }
1053                         (*len) += written;
1054                         /* Write auth tok signature packet */
1055                         rc = write_tag_11_packet(
1056                                 (dest_base + (*len)),
1057                                 (max - (*len)),
1058                                 key_rec.sig, ECRYPTFS_SIG_SIZE, &written);
1059                         if (rc) {
1060                                 ecryptfs_printk(KERN_ERR, "Error writing "
1061                                                 "auth tok signature packet\n");
1062                                 goto out;
1063                         }
1064                         (*len) += written;
1065                 } else {
1066                         ecryptfs_printk(KERN_WARNING, "Unsupported "
1067                                         "authentication token type\n");
1068                         rc = -EINVAL;
1069                         goto out;
1070                 }
1071                 if (rc) {
1072                         ecryptfs_printk(KERN_WARNING, "Error writing "
1073                                         "authentication token packet with sig "
1074                                         "= [%s]\n",
1075                                         mount_crypt_stat->global_auth_tok_sig);
1076                         rc = -EIO;
1077                         goto out;
1078                 }
1079         } else
1080                 BUG();
1081         if (likely((max - (*len)) > 0)) {
1082                 dest_base[(*len)] = 0x00;
1083         } else {
1084                 ecryptfs_printk(KERN_ERR, "Error writing boundary byte\n");
1085                 rc = -EIO;
1086         }
1087 out:
1088         if (rc)
1089                 (*len) = 0;
1090         return rc;
1091 }