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