fs/ecryptfs/crypto.c

   1 /**
   2  * eCryptfs: Linux filesystem encryption layer
   3  *
   4  * Copyright (C) 1997-2004 Erez Zadok
   5  * Copyright (C) 2001-2004 Stony Brook University
   6  * Copyright (C) 2004-2007 International Business Machines Corp.
   7  *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
   8  *              Michael C. Thompson <mcthomps@us.ibm.com>
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public License as
  12  * published by the Free Software Foundation; either version 2 of the
  13  * License, or (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  23  * 02111-1307, USA.
  24  */
  25
  26 #include <linux/fs.h>
  27 #include <linux/mount.h>
  28 #include <linux/pagemap.h>
  29 #include <linux/random.h>
  30 #include <linux/compiler.h>
  31 #include <linux/key.h>
  32 #include <linux/namei.h>
  33 #include <linux/crypto.h>
  34 #include <linux/file.h>
  35 #include <linux/scatterlist.h>
  36 #include "ecryptfs_kernel.h"
  37
  38 static int
  39 ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
  40                              struct page *dst_page, int dst_offset,
  41                              struct page *src_page, int src_offset, int size,
  42                              unsigned char *iv);
  43 static int
  44 ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
  45                              struct page *dst_page, int dst_offset,
  46                              struct page *src_page, int src_offset, int size,
  47                              unsigned char *iv);
  48
  49 /**
  50  * ecryptfs_to_hex
  51  * @dst: Buffer to take hex character representation of contents of
  52  *       src; must be at least of size (src_size * 2)
  53  * @src: Buffer to be converted to a hex string respresentation
  54  * @src_size: number of bytes to convert
  55  */
  56 void ecryptfs_to_hex(char *dst, char *src, size_t src_size)
  57 {
  58         int x;
  59
  60         for (x = 0; x < src_size; x++)
  61                 sprintf(&dst[x * 2], "%.2x", (unsigned char)src[x]);
  62 }
  63
  64 /**
  65  * ecryptfs_from_hex
  66  * @dst: Buffer to take the bytes from src hex; must be at least of
  67  *       size (src_size / 2)
  68  * @src: Buffer to be converted from a hex string respresentation to raw value
  69  * @dst_size: size of dst buffer, or number of hex characters pairs to convert
  70  */
  71 void ecryptfs_from_hex(char *dst, char *src, int dst_size)
  72 {
  73         int x;
  74         char tmp[3] = { 0, };
  75
  76         for (x = 0; x < dst_size; x++) {
  77                 tmp[0] = src[x * 2];
  78                 tmp[1] = src[x * 2 + 1];
  79                 dst[x] = (unsigned char)simple_strtol(tmp, NULL, 16);
  80         }
  81 }
  82
  83 /**
  84  * ecryptfs_calculate_md5 - calculates the md5 of @src
  85  * @dst: Pointer to 16 bytes of allocated memory
  86  * @crypt_stat: Pointer to crypt_stat struct for the current inode
  87  * @src: Data to be md5'd
  88  * @len: Length of @src
  89  *
  90  * Uses the allocated crypto context that crypt_stat references to
  91  * generate the MD5 sum of the contents of src.
  92  */
  93 static int ecryptfs_calculate_md5(char *dst,
  94                                   struct ecryptfs_crypt_stat *crypt_stat,
  95                                   char *src, int len)
  96 {
  97         struct scatterlist sg;
  98         struct hash_desc desc = {
  99                 .tfm = crypt_stat->hash_tfm,
 100                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
 101         };
 102         int rc = 0;
 103
 104         mutex_lock(&crypt_stat->cs_hash_tfm_mutex);
 105         sg_init_one(&sg, (u8 *)src, len);
 106         if (!desc.tfm) {
 107                 desc.tfm = crypto_alloc_hash(ECRYPTFS_DEFAULT_HASH, 0,
 108                                              CRYPTO_ALG_ASYNC);
 109                 if (IS_ERR(desc.tfm)) {
 110                         rc = PTR_ERR(desc.tfm);
 111                         ecryptfs_printk(KERN_ERR, "Error attempting to "
 112                                         "allocate crypto context; rc = [%d]\n",
 113                                         rc);
 114                         goto out;
 115                 }
 116                 crypt_stat->hash_tfm = desc.tfm;
 117         }
 118         crypto_hash_init(&desc);
 119         crypto_hash_update(&desc, &sg, len);
 120         crypto_hash_final(&desc, dst);
 121         mutex_unlock(&crypt_stat->cs_hash_tfm_mutex);
 122 out:
 123         return rc;
 124 }
 125
 126 int ecryptfs_crypto_api_algify_cipher_name(char **algified_name,
 127                                            char *cipher_name,
 128                                            char *chaining_modifier)
 129 {
 130         int cipher_name_len = strlen(cipher_name);
 131         int chaining_modifier_len = strlen(chaining_modifier);
 132         int algified_name_len;
 133         int rc;
 134
 135         algified_name_len = (chaining_modifier_len + cipher_name_len + 3);
 136         (*algified_name) = kmalloc(algified_name_len, GFP_KERNEL);
 137         if (!(*algified_name)) {
 138                 rc = -ENOMEM;
 139                 goto out;
 140         }
 141         snprintf((*algified_name), algified_name_len, "%s(%s)",
 142                  chaining_modifier, cipher_name);
 143         rc = 0;
 144 out:
 145         return rc;
 146 }
 147
 148 /**
 149  * ecryptfs_derive_iv
 150  * @iv: destination for the derived iv vale
 151  * @crypt_stat: Pointer to crypt_stat struct for the current inode
 152  * @offset: Offset of the page whose's iv we are to derive
 153  *
 154  * Generate the initialization vector from the given root IV and page
 155  * offset.
 156  *
 157  * Returns zero on success; non-zero on error.
 158  */
 159 static int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
 160                               pgoff_t offset)
 161 {
 162         int rc = 0;
 163         char dst[MD5_DIGEST_SIZE];
 164         char src[ECRYPTFS_MAX_IV_BYTES + 16];
 165
 166         if (unlikely(ecryptfs_verbosity > 0)) {
 167                 ecryptfs_printk(KERN_DEBUG, "root iv:\n");
 168                 ecryptfs_dump_hex(crypt_stat->root_iv, crypt_stat->iv_bytes);
 169         }
 170         /* TODO: It is probably secure to just cast the least
 171          * significant bits of the root IV into an unsigned long and
 172          * add the offset to that rather than go through all this
 173          * hashing business. -Halcrow */
 174         memcpy(src, crypt_stat->root_iv, crypt_stat->iv_bytes);
 175         memset((src + crypt_stat->iv_bytes), 0, 16);
 176         snprintf((src + crypt_stat->iv_bytes), 16, "%ld", offset);
 177         if (unlikely(ecryptfs_verbosity > 0)) {
 178                 ecryptfs_printk(KERN_DEBUG, "source:\n");
 179                 ecryptfs_dump_hex(src, (crypt_stat->iv_bytes + 16));
 180         }
 181         rc = ecryptfs_calculate_md5(dst, crypt_stat, src,
 182                                     (crypt_stat->iv_bytes + 16));
 183         if (rc) {
 184                 ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
 185                                 "MD5 while generating IV for a page\n");
 186                 goto out;
 187         }
 188         memcpy(iv, dst, crypt_stat->iv_bytes);
 189         if (unlikely(ecryptfs_verbosity > 0)) {
 190                 ecryptfs_printk(KERN_DEBUG, "derived iv:\n");
 191                 ecryptfs_dump_hex(iv, crypt_stat->iv_bytes);
 192         }
 193 out:
 194         return rc;
 195 }
 196
 197 /**
 198  * ecryptfs_init_crypt_stat
 199  * @crypt_stat: Pointer to the crypt_stat struct to initialize.
 200  *
 201  * Initialize the crypt_stat structure.
 202  */
 203 void
 204 ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
 205 {
 206         memset((void *)crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
 207         mutex_init(&crypt_stat->cs_mutex);
 208         mutex_init(&crypt_stat->cs_tfm_mutex);
 209         mutex_init(&crypt_stat->cs_hash_tfm_mutex);
 210         crypt_stat->flags |= ECRYPTFS_STRUCT_INITIALIZED;
 211 }
 212
 213 /**
 214  * ecryptfs_destruct_crypt_stat
 215  * @crypt_stat: Pointer to the crypt_stat struct to initialize.
 216  *
 217  * Releases all memory associated with a crypt_stat struct.
 218  */
 219 void ecryptfs_destruct_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
 220 {
 221         if (crypt_stat->tfm)
 222                 crypto_free_blkcipher(crypt_stat->tfm);
 223         if (crypt_stat->hash_tfm)
 224                 crypto_free_hash(crypt_stat->hash_tfm);
 225         memset(crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
 226 }
 227
 228 void ecryptfs_destruct_mount_crypt_stat(
 229         struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
 230 {
 231         if (mount_crypt_stat->global_auth_tok_key)
 232                 key_put(mount_crypt_stat->global_auth_tok_key);
 233         if (mount_crypt_stat->global_key_tfm)
 234                 crypto_free_blkcipher(mount_crypt_stat->global_key_tfm);
 235         memset(mount_crypt_stat, 0, sizeof(struct ecryptfs_mount_crypt_stat));
 236 }
 237
 238 /**
 239  * virt_to_scatterlist
 240  * @addr: Virtual address
 241  * @size: Size of data; should be an even multiple of the block size
 242  * @sg: Pointer to scatterlist array; set to NULL to obtain only
 243  *      the number of scatterlist structs required in array
 244  * @sg_size: Max array size
 245  *
 246  * Fills in a scatterlist array with page references for a passed
 247  * virtual address.
 248  *
 249  * Returns the number of scatterlist structs in array used
 250  */
 251 int virt_to_scatterlist(const void *addr, int size, struct scatterlist *sg,
 252                         int sg_size)
 253 {
 254         int i = 0;
 255         struct page *pg;
 256         int offset;
 257         int remainder_of_page;
 258
 259         while (size > 0 && i < sg_size) {
 260                 pg = virt_to_page(addr);
 261                 offset = offset_in_page(addr);
 262                 if (sg) {
 263                         sg[i].page = pg;
 264                         sg[i].offset = offset;
 265                 }
 266                 remainder_of_page = PAGE_CACHE_SIZE - offset;
 267                 if (size >= remainder_of_page) {
 268                         if (sg)
 269                                 sg[i].length = remainder_of_page;
 270                         addr += remainder_of_page;
 271                         size -= remainder_of_page;
 272                 } else {
 273                         if (sg)
 274                                 sg[i].length = size;
 275                         addr += size;
 276                         size = 0;
 277                 }
 278                 i++;
 279         }
 280         if (size > 0)
 281                 return -ENOMEM;
 282         return i;
 283 }
 284
 285 /**
 286  * encrypt_scatterlist
 287  * @crypt_stat: Pointer to the crypt_stat struct to initialize.
 288  * @dest_sg: Destination of encrypted data
 289  * @src_sg: Data to be encrypted
 290  * @size: Length of data to be encrypted
 291  * @iv: iv to use during encryption
 292  *
 293  * Returns the number of bytes encrypted; negative value on error
 294  */
 295 static int encrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
 296                                struct scatterlist *dest_sg,
 297                                struct scatterlist *src_sg, int size,
 298                                unsigned char *iv)
 299 {
 300         struct blkcipher_desc desc = {
 301                 .tfm = crypt_stat->tfm,
 302                 .info = iv,
 303                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
 304         };
 305         int rc = 0;
 306
 307         BUG_ON(!crypt_stat || !crypt_stat->tfm
 308                || !(crypt_stat->flags & ECRYPTFS_STRUCT_INITIALIZED));
 309         if (unlikely(ecryptfs_verbosity > 0)) {
 310                 ecryptfs_printk(KERN_DEBUG, "Key size [%d]; key:\n",
 311                                 crypt_stat->key_size);
 312                 ecryptfs_dump_hex(crypt_stat->key,
 313                                   crypt_stat->key_size);
 314         }
 315         /* Consider doing this once, when the file is opened */
 316         mutex_lock(&crypt_stat->cs_tfm_mutex);
 317         rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
 318                                      crypt_stat->key_size);
 319         if (rc) {
 320                 ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
 321                                 rc);
 322                 mutex_unlock(&crypt_stat->cs_tfm_mutex);
 323                 rc = -EINVAL;
 324                 goto out;
 325         }
 326         ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes.\n", size);
 327         crypto_blkcipher_encrypt_iv(&desc, dest_sg, src_sg, size);
 328         mutex_unlock(&crypt_stat->cs_tfm_mutex);
 329 out:
 330         return rc;
 331 }
 332
 333 static void
 334 ecryptfs_extent_to_lwr_pg_idx_and_offset(unsigned long *lower_page_idx,
 335                                          int *byte_offset,
 336                                          struct ecryptfs_crypt_stat *crypt_stat,
 337                                          unsigned long extent_num)
 338 {
 339         unsigned long lower_extent_num;
 340         int extents_occupied_by_headers_at_front;
 341         int bytes_occupied_by_headers_at_front;
 342         int extent_offset;
 343         int extents_per_page;
 344
 345         bytes_occupied_by_headers_at_front =
 346                 ( crypt_stat->header_extent_size
 347                   * crypt_stat->num_header_extents_at_front );
 348         extents_occupied_by_headers_at_front =
 349                 ( bytes_occupied_by_headers_at_front
 350                   / crypt_stat->extent_size );
 351         lower_extent_num = extents_occupied_by_headers_at_front + extent_num;
 352         extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
 353         (*lower_page_idx) = lower_extent_num / extents_per_page;
 354         extent_offset = lower_extent_num % extents_per_page;
 355         (*byte_offset) = extent_offset * crypt_stat->extent_size;
 356         ecryptfs_printk(KERN_DEBUG, " * crypt_stat->header_extent_size = "
 357                         "[%d]\n", crypt_stat->header_extent_size);
 358         ecryptfs_printk(KERN_DEBUG, " * crypt_stat->"
 359                         "num_header_extents_at_front = [%d]\n",
 360                         crypt_stat->num_header_extents_at_front);
 361         ecryptfs_printk(KERN_DEBUG, " * extents_occupied_by_headers_at_"
 362                         "front = [%d]\n", extents_occupied_by_headers_at_front);
 363         ecryptfs_printk(KERN_DEBUG, " * lower_extent_num = [0x%.16x]\n",
 364                         lower_extent_num);
 365         ecryptfs_printk(KERN_DEBUG, " * extents_per_page = [%d]\n",
 366                         extents_per_page);
 367         ecryptfs_printk(KERN_DEBUG, " * (*lower_page_idx) = [0x%.16x]\n",
 368                         (*lower_page_idx));
 369         ecryptfs_printk(KERN_DEBUG, " * extent_offset = [%d]\n",
 370                         extent_offset);
 371         ecryptfs_printk(KERN_DEBUG, " * (*byte_offset) = [%d]\n",
 372                         (*byte_offset));
 373 }
 374
 375 static int ecryptfs_write_out_page(struct ecryptfs_page_crypt_context *ctx,
 376                                    struct page *lower_page,
 377                                    struct inode *lower_inode,
 378                                    int byte_offset_in_page, int bytes_to_write)
 379 {
 380         int rc = 0;
 381
 382         if (ctx->mode == ECRYPTFS_PREPARE_COMMIT_MODE) {
 383                 rc = ecryptfs_commit_lower_page(lower_page, lower_inode,
 384                                                 ctx->param.lower_file,
 385                                                 byte_offset_in_page,
 386                                                 bytes_to_write);
 387                 if (rc) {
 388                         ecryptfs_printk(KERN_ERR, "Error calling lower "
 389                                         "commit; rc = [%d]\n", rc);
 390                         goto out;
 391                 }
 392         } else {
 393                 rc = ecryptfs_writepage_and_release_lower_page(lower_page,
 394                                                                lower_inode,
 395                                                                ctx->param.wbc);
 396                 if (rc) {
 397                         ecryptfs_printk(KERN_ERR, "Error calling lower "
 398                                         "writepage(); rc = [%d]\n", rc);
 399                         goto out;
 400                 }
 401         }
 402 out:
 403         return rc;
 404 }
 405
 406 static int ecryptfs_read_in_page(struct ecryptfs_page_crypt_context *ctx,
 407                                  struct page **lower_page,
 408                                  struct inode *lower_inode,
 409                                  unsigned long lower_page_idx,
 410                                  int byte_offset_in_page)
 411 {
 412         int rc = 0;
 413
 414         if (ctx->mode == ECRYPTFS_PREPARE_COMMIT_MODE) {
 415                 /* TODO: Limit this to only the data extents that are
 416                  * needed */
 417                 rc = ecryptfs_get_lower_page(lower_page, lower_inode,
 418                                              ctx->param.lower_file,
 419                                              lower_page_idx,
 420                                              byte_offset_in_page,
 421                                              (PAGE_CACHE_SIZE
 422                                               - byte_offset_in_page));
 423                 if (rc) {
 424                         ecryptfs_printk(
 425                                 KERN_ERR, "Error attempting to grab, map, "
 426                                 "and prepare_write lower page with index "
 427                                 "[0x%.16x]; rc = [%d]\n", lower_page_idx, rc);
 428                         goto out;
 429                 }
 430         } else {
 431                 *lower_page = grab_cache_page(lower_inode->i_mapping,
 432                                               lower_page_idx);
 433                 if (!(*lower_page)) {
 434                         rc = -EINVAL;
 435                         ecryptfs_printk(
 436                                 KERN_ERR, "Error attempting to grab and map "
 437                                 "lower page with index [0x%.16x]; rc = [%d]\n",
 438                                 lower_page_idx, rc);
 439                         goto out;
 440                 }
 441         }
 442 out:
 443         return rc;
 444 }
 445
 446 /**
 447  * ecryptfs_encrypt_page
 448  * @ctx: The context of the page
 449  *
 450  * Encrypt an eCryptfs page. This is done on a per-extent basis. Note
 451  * that eCryptfs pages may straddle the lower pages -- for instance,
 452  * if the file was created on a machine with an 8K page size
 453  * (resulting in an 8K header), and then the file is copied onto a
 454  * host with a 32K page size, then when reading page 0 of the eCryptfs
 455  * file, 24K of page 0 of the lower file will be read and decrypted,
 456  * and then 8K of page 1 of the lower file will be read and decrypted.
 457  *
 458  * The actual operations performed on each page depends on the
 459  * contents of the ecryptfs_page_crypt_context struct.
 460  *
 461  * Returns zero on success; negative on error
 462  */
 463 int ecryptfs_encrypt_page(struct ecryptfs_page_crypt_context *ctx)
 464 {
 465         char extent_iv[ECRYPTFS_MAX_IV_BYTES];
 466         unsigned long base_extent;
 467         unsigned long extent_offset = 0;
 468         unsigned long lower_page_idx = 0;
 469         unsigned long prior_lower_page_idx = 0;
 470         struct page *lower_page;
 471         struct inode *lower_inode;
 472         struct ecryptfs_inode_info *inode_info;
 473         struct ecryptfs_crypt_stat *crypt_stat;
 474         int rc = 0;
 475         int lower_byte_offset = 0;
 476         int orig_byte_offset = 0;
 477         int num_extents_per_page;
 478 #define ECRYPTFS_PAGE_STATE_UNREAD    0
 479 #define ECRYPTFS_PAGE_STATE_READ      1
 480 #define ECRYPTFS_PAGE_STATE_MODIFIED  2
 481 #define ECRYPTFS_PAGE_STATE_WRITTEN   3
 482         int page_state;
 483
 484         lower_inode = ecryptfs_inode_to_lower(ctx->page->mapping->host);
 485         inode_info = ecryptfs_inode_to_private(ctx->page->mapping->host);
 486         crypt_stat = &inode_info->crypt_stat;
 487         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 488                 rc = ecryptfs_copy_page_to_lower(ctx->page, lower_inode,
 489                                                  ctx->param.lower_file);
 490                 if (rc)
 491                         ecryptfs_printk(KERN_ERR, "Error attempting to copy "
 492                                         "page at index [0x%.16x]\n",
 493                                         ctx->page->index);
 494                 goto out;
 495         }
 496         num_extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
 497         base_extent = (ctx->page->index * num_extents_per_page);
 498         page_state = ECRYPTFS_PAGE_STATE_UNREAD;
 499         while (extent_offset < num_extents_per_page) {
 500                 ecryptfs_extent_to_lwr_pg_idx_and_offset(
 501                         &lower_page_idx, &lower_byte_offset, crypt_stat,
 502                         (base_extent + extent_offset));
 503                 if (prior_lower_page_idx != lower_page_idx
 504                     && page_state == ECRYPTFS_PAGE_STATE_MODIFIED) {
 505                         rc = ecryptfs_write_out_page(ctx, lower_page,
 506                                                      lower_inode,
 507                                                      orig_byte_offset,
 508                                                      (PAGE_CACHE_SIZE
 509                                                       - orig_byte_offset));
 510                         if (rc) {
 511                                 ecryptfs_printk(KERN_ERR, "Error attempting "
 512                                                 "to write out page; rc = [%d]"
 513                                                 "\n", rc);
 514                                 goto out;
 515                         }
 516                         page_state = ECRYPTFS_PAGE_STATE_WRITTEN;
 517                 }
 518                 if (page_state == ECRYPTFS_PAGE_STATE_UNREAD
 519                     || page_state == ECRYPTFS_PAGE_STATE_WRITTEN) {
 520                         rc = ecryptfs_read_in_page(ctx, &lower_page,
 521                                                    lower_inode, lower_page_idx,
 522                                                    lower_byte_offset);
 523                         if (rc) {
 524                                 ecryptfs_printk(KERN_ERR, "Error attempting "
 525                                                 "to read in lower page with "
 526                                                 "index [0x%.16x]; rc = [%d]\n",
 527                                                 lower_page_idx, rc);
 528                                 goto out;
 529                         }
 530                         orig_byte_offset = lower_byte_offset;
 531                         prior_lower_page_idx = lower_page_idx;
 532                         page_state = ECRYPTFS_PAGE_STATE_READ;
 533                 }
 534                 BUG_ON(!(page_state == ECRYPTFS_PAGE_STATE_MODIFIED
 535                          || page_state == ECRYPTFS_PAGE_STATE_READ));
 536                 rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
 537                                         (base_extent + extent_offset));
 538                 if (rc) {
 539                         ecryptfs_printk(KERN_ERR, "Error attempting to "
 540                                         "derive IV for extent [0x%.16x]; "
 541                                         "rc = [%d]\n",
 542                                         (base_extent + extent_offset), rc);
 543                         goto out;
 544                 }
 545                 if (unlikely(ecryptfs_verbosity > 0)) {
 546                         ecryptfs_printk(KERN_DEBUG, "Encrypting extent "
 547                                         "with iv:\n");
 548                         ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
 549                         ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
 550                                         "encryption:\n");
 551                         ecryptfs_dump_hex((char *)
 552                                           (page_address(ctx->page)
 553                                            + (extent_offset
 554                                               * crypt_stat->extent_size)), 8);
 555                 }
 556                 rc = ecryptfs_encrypt_page_offset(
 557                         crypt_stat, lower_page, lower_byte_offset, ctx->page,
 558                         (extent_offset * crypt_stat->extent_size),
 559                         crypt_stat->extent_size, extent_iv);
 560                 ecryptfs_printk(KERN_DEBUG, "Encrypt extent [0x%.16x]; "
 561                                 "rc = [%d]\n",
 562                                 (base_extent + extent_offset), rc);
 563                 if (unlikely(ecryptfs_verbosity > 0)) {
 564                         ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
 565                                         "encryption:\n");
 566                         ecryptfs_dump_hex((char *)(page_address(lower_page)
 567                                                    + lower_byte_offset), 8);
 568                 }
 569                 page_state = ECRYPTFS_PAGE_STATE_MODIFIED;
 570                 extent_offset++;
 571         }
 572         BUG_ON(orig_byte_offset != 0);
 573         rc = ecryptfs_write_out_page(ctx, lower_page, lower_inode, 0,
 574                                      (lower_byte_offset
 575                                       + crypt_stat->extent_size));
 576         if (rc) {
 577                 ecryptfs_printk(KERN_ERR, "Error attempting to write out "
 578                                 "page; rc = [%d]\n", rc);
 579                                 goto out;
 580         }
 581 out:
 582         return rc;
 583 }
 584
 585 /**
 586  * ecryptfs_decrypt_page
 587  * @file: The ecryptfs file
 588  * @page: The page in ecryptfs to decrypt
 589  *
 590  * Decrypt an eCryptfs page. This is done on a per-extent basis. Note
 591  * that eCryptfs pages may straddle the lower pages -- for instance,
 592  * if the file was created on a machine with an 8K page size
 593  * (resulting in an 8K header), and then the file is copied onto a
 594  * host with a 32K page size, then when reading page 0 of the eCryptfs
 595  * file, 24K of page 0 of the lower file will be read and decrypted,
 596  * and then 8K of page 1 of the lower file will be read and decrypted.
 597  *
 598  * Returns zero on success; negative on error
 599  */
 600 int ecryptfs_decrypt_page(struct file *file, struct page *page)
 601 {
 602         char extent_iv[ECRYPTFS_MAX_IV_BYTES];
 603         unsigned long base_extent;
 604         unsigned long extent_offset = 0;
 605         unsigned long lower_page_idx = 0;
 606         unsigned long prior_lower_page_idx = 0;
 607         struct page *lower_page;
 608         char *lower_page_virt = NULL;
 609         struct inode *lower_inode;
 610         struct ecryptfs_crypt_stat *crypt_stat;
 611         int rc = 0;
 612         int byte_offset;
 613         int num_extents_per_page;
 614         int page_state;
 615
 616         crypt_stat = &(ecryptfs_inode_to_private(
 617                                page->mapping->host)->crypt_stat);
 618         lower_inode = ecryptfs_inode_to_lower(page->mapping->host);
 619         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 620                 rc = ecryptfs_do_readpage(file, page, page->index);
 621                 if (rc)
 622                         ecryptfs_printk(KERN_ERR, "Error attempting to copy "
 623                                         "page at index [0x%.16x]\n",
 624                                         page->index);
 625                 goto out;
 626         }
 627         num_extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
 628         base_extent = (page->index * num_extents_per_page);
 629         lower_page_virt = kmem_cache_alloc(ecryptfs_lower_page_cache,
 630                                            GFP_KERNEL);
 631         if (!lower_page_virt) {
 632                 rc = -ENOMEM;
 633                 ecryptfs_printk(KERN_ERR, "Error getting page for encrypted "
 634                                 "lower page(s)\n");
 635                 goto out;
 636         }
 637         lower_page = virt_to_page(lower_page_virt);
 638         page_state = ECRYPTFS_PAGE_STATE_UNREAD;
 639         while (extent_offset < num_extents_per_page) {
 640                 ecryptfs_extent_to_lwr_pg_idx_and_offset(
 641                         &lower_page_idx, &byte_offset, crypt_stat,
 642                         (base_extent + extent_offset));
 643                 if (prior_lower_page_idx != lower_page_idx
 644                     || page_state == ECRYPTFS_PAGE_STATE_UNREAD) {
 645                         rc = ecryptfs_do_readpage(file, lower_page,
 646                                                   lower_page_idx);
 647                         if (rc) {
 648                                 ecryptfs_printk(KERN_ERR, "Error reading "
 649                                                 "lower encrypted page; rc = "
 650                                                 "[%d]\n", rc);
 651                                 goto out;
 652                         }
 653                         prior_lower_page_idx = lower_page_idx;
 654                         page_state = ECRYPTFS_PAGE_STATE_READ;
 655                 }
 656                 rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
 657                                         (base_extent + extent_offset));
 658                 if (rc) {
 659                         ecryptfs_printk(KERN_ERR, "Error attempting to "
 660                                         "derive IV for extent [0x%.16x]; rc = "
 661                                         "[%d]\n",
 662                                         (base_extent + extent_offset), rc);
 663                         goto out;
 664                 }
 665                 if (unlikely(ecryptfs_verbosity > 0)) {
 666                         ecryptfs_printk(KERN_DEBUG, "Decrypting extent "
 667                                         "with iv:\n");
 668                         ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
 669                         ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
 670                                         "decryption:\n");
 671                         ecryptfs_dump_hex((lower_page_virt + byte_offset), 8);
 672                 }
 673                 rc = ecryptfs_decrypt_page_offset(crypt_stat, page,
 674                                                   (extent_offset
 675                                                    * crypt_stat->extent_size),
 676                                                   lower_page, byte_offset,
 677                                                   crypt_stat->extent_size,
 678                                                   extent_iv);
 679                 if (rc != crypt_stat->extent_size) {
 680                         ecryptfs_printk(KERN_ERR, "Error attempting to "
 681                                         "decrypt extent [0x%.16x]\n",
 682                                         (base_extent + extent_offset));
 683                         goto out;
 684                 }
 685                 rc = 0;
 686                 if (unlikely(ecryptfs_verbosity > 0)) {
 687                         ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
 688                                         "decryption:\n");
 689                         ecryptfs_dump_hex((char *)(page_address(page)
 690                                                    + byte_offset), 8);
 691                 }
 692                 extent_offset++;
 693         }
 694 out:
 695         if (lower_page_virt)
 696                 kmem_cache_free(ecryptfs_lower_page_cache, lower_page_virt);
 697         return rc;
 698 }
 699
 700 /**
 701  * decrypt_scatterlist
 702  *
 703  * Returns the number of bytes decrypted; negative value on error
 704  */
 705 static int decrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
 706                                struct scatterlist *dest_sg,
 707                                struct scatterlist *src_sg, int size,
 708                                unsigned char *iv)
 709 {
 710         struct blkcipher_desc desc = {
 711                 .tfm = crypt_stat->tfm,
 712                 .info = iv,
 713                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
 714         };
 715         int rc = 0;
 716
 717         /* Consider doing this once, when the file is opened */
 718         mutex_lock(&crypt_stat->cs_tfm_mutex);
 719         rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
 720                                      crypt_stat->key_size);
 721         if (rc) {
 722                 ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
 723                                 rc);
 724                 mutex_unlock(&crypt_stat->cs_tfm_mutex);
 725                 rc = -EINVAL;
 726                 goto out;
 727         }
 728         ecryptfs_printk(KERN_DEBUG, "Decrypting [%d] bytes.\n", size);
 729         rc = crypto_blkcipher_decrypt_iv(&desc, dest_sg, src_sg, size);
 730         mutex_unlock(&crypt_stat->cs_tfm_mutex);
 731         if (rc) {
 732                 ecryptfs_printk(KERN_ERR, "Error decrypting; rc = [%d]\n",
 733                                 rc);
 734                 goto out;
 735         }
 736         rc = size;
 737 out:
 738         return rc;
 739 }
 740
 741 /**
 742  * ecryptfs_encrypt_page_offset
 743  *
 744  * Returns the number of bytes encrypted
 745  */
 746 static int
 747 ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
 748                              struct page *dst_page, int dst_offset,
 749                              struct page *src_page, int src_offset, int size,
 750                              unsigned char *iv)
 751 {
 752         struct scatterlist src_sg, dst_sg;
 753
 754         src_sg.page = src_page;
 755         src_sg.offset = src_offset;
 756         src_sg.length = size;
 757         dst_sg.page = dst_page;
 758         dst_sg.offset = dst_offset;
 759         dst_sg.length = size;
 760         return encrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
 761 }
 762
 763 /**
 764  * ecryptfs_decrypt_page_offset
 765  *
 766  * Returns the number of bytes decrypted
 767  */
 768 static int
 769 ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
 770                              struct page *dst_page, int dst_offset,
 771                              struct page *src_page, int src_offset, int size,
 772                              unsigned char *iv)
 773 {
 774         struct scatterlist src_sg, dst_sg;
 775
 776         src_sg.page = src_page;
 777         src_sg.offset = src_offset;
 778         src_sg.length = size;
 779         dst_sg.page = dst_page;
 780         dst_sg.offset = dst_offset;
 781         dst_sg.length = size;
 782         return decrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
 783 }
 784
 785 #define ECRYPTFS_MAX_SCATTERLIST_LEN 4
 786
 787 /**
 788  * ecryptfs_init_crypt_ctx
 789  * @crypt_stat: Uninitilized crypt stats structure
 790  *
 791  * Initialize the crypto context.
 792  *
 793  * TODO: Performance: Keep a cache of initialized cipher contexts;
 794  * only init if needed
 795  */
 796 int ecryptfs_init_crypt_ctx(struct ecryptfs_crypt_stat *crypt_stat)
 797 {
 798         char *full_alg_name;
 799         int rc = -EINVAL;
 800
 801         if (!crypt_stat->cipher) {
 802                 ecryptfs_printk(KERN_ERR, "No cipher specified\n");
 803                 goto out;
 804         }
 805         ecryptfs_printk(KERN_DEBUG,
 806                         "Initializing cipher [%s]; strlen = [%d]; "
 807                         "key_size_bits = [%d]\n",
 808                         crypt_stat->cipher, (int)strlen(crypt_stat->cipher),
 809                         crypt_stat->key_size << 3);
 810         if (crypt_stat->tfm) {
 811                 rc = 0;
 812                 goto out;
 813         }
 814         mutex_lock(&crypt_stat->cs_tfm_mutex);
 815         rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
 816                                                     crypt_stat->cipher, "cbc");
 817         if (rc)
 818                 goto out;
 819         crypt_stat->tfm = crypto_alloc_blkcipher(full_alg_name, 0,
 820                                                  CRYPTO_ALG_ASYNC);
 821         kfree(full_alg_name);
 822         if (IS_ERR(crypt_stat->tfm)) {
 823                 rc = PTR_ERR(crypt_stat->tfm);
 824                 ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
 825                                 "Error initializing cipher [%s]\n",
 826                                 crypt_stat->cipher);
 827                 mutex_unlock(&crypt_stat->cs_tfm_mutex);
 828                 goto out;
 829         }
 830         crypto_blkcipher_set_flags(crypt_stat->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
 831         mutex_unlock(&crypt_stat->cs_tfm_mutex);
 832         rc = 0;
 833 out:
 834         return rc;
 835 }
 836
 837 static void set_extent_mask_and_shift(struct ecryptfs_crypt_stat *crypt_stat)
 838 {
 839         int extent_size_tmp;
 840
 841         crypt_stat->extent_mask = 0xFFFFFFFF;
 842         crypt_stat->extent_shift = 0;
 843         if (crypt_stat->extent_size == 0)
 844                 return;
 845         extent_size_tmp = crypt_stat->extent_size;
 846         while ((extent_size_tmp & 0x01) == 0) {
 847                 extent_size_tmp >>= 1;
 848                 crypt_stat->extent_mask <<= 1;
 849                 crypt_stat->extent_shift++;
 850         }
 851 }
 852
 853 void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat)
 854 {
 855         /* Default values; may be overwritten as we are parsing the
 856          * packets. */
 857         crypt_stat->extent_size = ECRYPTFS_DEFAULT_EXTENT_SIZE;
 858         set_extent_mask_and_shift(crypt_stat);
 859         crypt_stat->iv_bytes = ECRYPTFS_DEFAULT_IV_BYTES;
 860         if (PAGE_CACHE_SIZE <= ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE) {
 861                 crypt_stat->header_extent_size =
 862                         ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
 863         } else
 864                 crypt_stat->header_extent_size = PAGE_CACHE_SIZE;
 865         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 866                 crypt_stat->num_header_extents_at_front = 0;
 867         else
 868                 crypt_stat->num_header_extents_at_front = 1;
 869 }
 870
 871 /**
 872  * ecryptfs_compute_root_iv
 873  * @crypt_stats
 874  *
 875  * On error, sets the root IV to all 0's.
 876  */
 877 int ecryptfs_compute_root_iv(struct ecryptfs_crypt_stat *crypt_stat)
 878 {
 879         int rc = 0;
 880         char dst[MD5_DIGEST_SIZE];
 881
 882         BUG_ON(crypt_stat->iv_bytes > MD5_DIGEST_SIZE);
 883         BUG_ON(crypt_stat->iv_bytes <= 0);
 884         if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
 885                 rc = -EINVAL;
 886                 ecryptfs_printk(KERN_WARNING, "Session key not valid; "
 887                                 "cannot generate root IV\n");
 888                 goto out;
 889         }
 890         rc = ecryptfs_calculate_md5(dst, crypt_stat, crypt_stat->key,
 891                                     crypt_stat->key_size);
 892         if (rc) {
 893                 ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
 894                                 "MD5 while generating root IV\n");
 895                 goto out;
 896         }
 897         memcpy(crypt_stat->root_iv, dst, crypt_stat->iv_bytes);
 898 out:
 899         if (rc) {
 900                 memset(crypt_stat->root_iv, 0, crypt_stat->iv_bytes);
 901                 crypt_stat->flags |= ECRYPTFS_SECURITY_WARNING;
 902         }
 903         return rc;
 904 }
 905
 906 static void ecryptfs_generate_new_key(struct ecryptfs_crypt_stat *crypt_stat)
 907 {
 908         get_random_bytes(crypt_stat->key, crypt_stat->key_size);
 909         crypt_stat->flags |= ECRYPTFS_KEY_VALID;
 910         ecryptfs_compute_root_iv(crypt_stat);
 911         if (unlikely(ecryptfs_verbosity > 0)) {
 912                 ecryptfs_printk(KERN_DEBUG, "Generated new session key:\n");
 913                 ecryptfs_dump_hex(crypt_stat->key,
 914                                   crypt_stat->key_size);
 915         }
 916 }
 917
 918 /**
 919  * ecryptfs_copy_mount_wide_flags_to_inode_flags
 920  *
 921  * This function propagates the mount-wide flags to individual inode
 922  * flags.
 923  */
 924 static void ecryptfs_copy_mount_wide_flags_to_inode_flags(
 925         struct ecryptfs_crypt_stat *crypt_stat,
 926         struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
 927 {
 928         if (mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED)
 929                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
 930         if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
 931                 crypt_stat->flags |= ECRYPTFS_VIEW_AS_ENCRYPTED;
 932 }
 933
 934 /**
 935  * ecryptfs_set_default_crypt_stat_vals
 936  * @crypt_stat
 937  *
 938  * Default values in the event that policy does not override them.
 939  */
 940 static void ecryptfs_set_default_crypt_stat_vals(
 941         struct ecryptfs_crypt_stat *crypt_stat,
 942         struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
 943 {
 944         ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
 945                                                       mount_crypt_stat);
 946         ecryptfs_set_default_sizes(crypt_stat);
 947         strcpy(crypt_stat->cipher, ECRYPTFS_DEFAULT_CIPHER);
 948         crypt_stat->key_size = ECRYPTFS_DEFAULT_KEY_BYTES;
 949         crypt_stat->flags &= ~(ECRYPTFS_KEY_VALID);
 950         crypt_stat->file_version = ECRYPTFS_FILE_VERSION;
 951         crypt_stat->mount_crypt_stat = mount_crypt_stat;
 952 }
 953
 954 /**
 955  * ecryptfs_new_file_context
 956  * @ecryptfs_dentry
 957  *
 958  * If the crypto context for the file has not yet been established,
 959  * this is where we do that.  Establishing a new crypto context
 960  * involves the following decisions:
 961  *  - What cipher to use?
 962  *  - What set of authentication tokens to use?
 963  * Here we just worry about getting enough information into the
 964  * authentication tokens so that we know that they are available.
 965  * We associate the available authentication tokens with the new file
 966  * via the set of signatures in the crypt_stat struct.  Later, when
 967  * the headers are actually written out, we may again defer to
 968  * userspace to perform the encryption of the session key; for the
 969  * foreseeable future, this will be the case with public key packets.
 970  *
 971  * Returns zero on success; non-zero otherwise
 972  */
 973 /* Associate an authentication token(s) with the file */
 974 int ecryptfs_new_file_context(struct dentry *ecryptfs_dentry)
 975 {
 976         int rc = 0;
 977         struct ecryptfs_crypt_stat *crypt_stat =
 978             &ecryptfs_inode_to_private(ecryptfs_dentry->d_inode)->crypt_stat;
 979         struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
 980             &ecryptfs_superblock_to_private(
 981                     ecryptfs_dentry->d_sb)->mount_crypt_stat;
 982         int cipher_name_len;
 983
 984         ecryptfs_set_default_crypt_stat_vals(crypt_stat, mount_crypt_stat);
 985         /* See if there are mount crypt options */
 986         if (mount_crypt_stat->global_auth_tok) {
 987                 ecryptfs_printk(KERN_DEBUG, "Initializing context for new "
 988                                 "file using mount_crypt_stat\n");
 989                 crypt_stat->flags |= ECRYPTFS_ENCRYPTED;
 990                 crypt_stat->flags |= ECRYPTFS_KEY_VALID;
 991                 ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
 992                                                               mount_crypt_stat);
 993                 memcpy(crypt_stat->keysigs[crypt_stat->num_keysigs++],
 994                        mount_crypt_stat->global_auth_tok_sig,
 995                        ECRYPTFS_SIG_SIZE_HEX);
 996                 cipher_name_len =
 997                     strlen(mount_crypt_stat->global_default_cipher_name);
 998                 memcpy(crypt_stat->cipher,
 999                        mount_crypt_stat->global_default_cipher_name,
1000                        cipher_name_len);
1001                 crypt_stat->cipher[cipher_name_len] = '\0';
1002                 crypt_stat->key_size =
1003                         mount_crypt_stat->global_default_cipher_key_size;
1004                 ecryptfs_generate_new_key(crypt_stat);
1005         } else
1006                 /* We should not encounter this scenario since we
1007                  * should detect lack of global_auth_tok at mount time
1008                  * TODO: Applies to 0.1 release only; remove in future
1009                  * release */
1010                 BUG();
1011         rc = ecryptfs_init_crypt_ctx(crypt_stat);
1012         if (rc)
1013                 ecryptfs_printk(KERN_ERR, "Error initializing cryptographic "
1014                                 "context for cipher [%s]: rc = [%d]\n",
1015                                 crypt_stat->cipher, rc);
1016         return rc;
1017 }
1018
1019 /**
1020  * contains_ecryptfs_marker - check for the ecryptfs marker
1021  * @data: The data block in which to check
1022  *
1023  * Returns one if marker found; zero if not found
1024  */
1025 static int contains_ecryptfs_marker(char *data)
1026 {
1027         u32 m_1, m_2;
1028
1029         memcpy(&m_1, data, 4);
1030         m_1 = be32_to_cpu(m_1);
1031         memcpy(&m_2, (data + 4), 4);
1032         m_2 = be32_to_cpu(m_2);
1033         if ((m_1 ^ MAGIC_ECRYPTFS_MARKER) == m_2)
1034                 return 1;
1035         ecryptfs_printk(KERN_DEBUG, "m_1 = [0x%.8x]; m_2 = [0x%.8x]; "
1036                         "MAGIC_ECRYPTFS_MARKER = [0x%.8x]\n", m_1, m_2,
1037                         MAGIC_ECRYPTFS_MARKER);
1038         ecryptfs_printk(KERN_DEBUG, "(m_1 ^ MAGIC_ECRYPTFS_MARKER) = "
1039                         "[0x%.8x]\n", (m_1 ^ MAGIC_ECRYPTFS_MARKER));
1040         return 0;
1041 }
1042
1043 struct ecryptfs_flag_map_elem {
1044         u32 file_flag;
1045         u32 local_flag;
1046 };
1047
1048 /* Add support for additional flags by adding elements here. */
1049 static struct ecryptfs_flag_map_elem ecryptfs_flag_map[] = {
1050         {0x00000001, ECRYPTFS_ENABLE_HMAC},
1051         {0x00000002, ECRYPTFS_ENCRYPTED},
1052         {0x00000004, ECRYPTFS_METADATA_IN_XATTR}
1053 };
1054
1055 /**
1056  * ecryptfs_process_flags
1057  * @crypt_stat
1058  * @page_virt: Source data to be parsed
1059  * @bytes_read: Updated with the number of bytes read
1060  *
1061  * Returns zero on success; non-zero if the flag set is invalid
1062  */
1063 static int ecryptfs_process_flags(struct ecryptfs_crypt_stat *crypt_stat,
1064                                   char *page_virt, int *bytes_read)
1065 {
1066         int rc = 0;
1067         int i;
1068         u32 flags;
1069
1070         memcpy(&flags, page_virt, 4);
1071         flags = be32_to_cpu(flags);
1072         for (i = 0; i < ((sizeof(ecryptfs_flag_map)
1073                           / sizeof(struct ecryptfs_flag_map_elem))); i++)
1074                 if (flags & ecryptfs_flag_map[i].file_flag) {
1075                         crypt_stat->flags |= ecryptfs_flag_map[i].local_flag;
1076                 } else
1077                         crypt_stat->flags &= ~(ecryptfs_flag_map[i].local_flag);
1078         /* Version is in top 8 bits of the 32-bit flag vector */
1079         crypt_stat->file_version = ((flags >> 24) & 0xFF);
1080         (*bytes_read) = 4;
1081         return rc;
1082 }
1083
1084 /**
1085  * write_ecryptfs_marker
1086  * @page_virt: The pointer to in a page to begin writing the marker
1087  * @written: Number of bytes written
1088  *
1089  * Marker = 0x3c81b7f5
1090  */
1091 static void write_ecryptfs_marker(char *page_virt, size_t *written)
1092 {
1093         u32 m_1, m_2;
1094
1095         get_random_bytes(&m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
1096         m_2 = (m_1 ^ MAGIC_ECRYPTFS_MARKER);
1097         m_1 = cpu_to_be32(m_1);
1098         memcpy(page_virt, &m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
1099         m_2 = cpu_to_be32(m_2);
1100         memcpy(page_virt + (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2), &m_2,
1101                (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
1102         (*written) = MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
1103 }
1104
1105 static void
1106 write_ecryptfs_flags(char *page_virt, struct ecryptfs_crypt_stat *crypt_stat,
1107                      size_t *written)
1108 {
1109         u32 flags = 0;
1110         int i;
1111
1112         for (i = 0; i < ((sizeof(ecryptfs_flag_map)
1113                           / sizeof(struct ecryptfs_flag_map_elem))); i++)
1114                 if (crypt_stat->flags & ecryptfs_flag_map[i].local_flag)
1115                         flags |= ecryptfs_flag_map[i].file_flag;
1116         /* Version is in top 8 bits of the 32-bit flag vector */
1117         flags |= ((((u8)crypt_stat->file_version) << 24) & 0xFF000000);
1118         flags = cpu_to_be32(flags);
1119         memcpy(page_virt, &flags, 4);
1120         (*written) = 4;
1121 }
1122
1123 struct ecryptfs_cipher_code_str_map_elem {
1124         char cipher_str[16];
1125         u16 cipher_code;
1126 };
1127
1128 /* Add support for additional ciphers by adding elements here. The
1129  * cipher_code is whatever OpenPGP applicatoins use to identify the
1130  * ciphers. List in order of probability. */
1131 static struct ecryptfs_cipher_code_str_map_elem
1132 ecryptfs_cipher_code_str_map[] = {
1133         {"aes",RFC2440_CIPHER_AES_128 },
1134         {"blowfish", RFC2440_CIPHER_BLOWFISH},
1135         {"des3_ede", RFC2440_CIPHER_DES3_EDE},
1136         {"cast5", RFC2440_CIPHER_CAST_5},
1137         {"twofish", RFC2440_CIPHER_TWOFISH},
1138         {"cast6", RFC2440_CIPHER_CAST_6},
1139         {"aes", RFC2440_CIPHER_AES_192},
1140         {"aes", RFC2440_CIPHER_AES_256}
1141 };
1142
1143 /**
1144  * ecryptfs_code_for_cipher_string
1145  * @str: The string representing the cipher name
1146  *
1147  * Returns zero on no match, or the cipher code on match
1148  */
1149 u16 ecryptfs_code_for_cipher_string(struct ecryptfs_crypt_stat *crypt_stat)
1150 {
1151         int i;
1152         u16 code = 0;
1153         struct ecryptfs_cipher_code_str_map_elem *map =
1154                 ecryptfs_cipher_code_str_map;
1155
1156         if (strcmp(crypt_stat->cipher, "aes") == 0) {
1157                 switch (crypt_stat->key_size) {
1158                 case 16:
1159                         code = RFC2440_CIPHER_AES_128;
1160                         break;
1161                 case 24:
1162                         code = RFC2440_CIPHER_AES_192;
1163                         break;
1164                 case 32:
1165                         code = RFC2440_CIPHER_AES_256;
1166                 }
1167         } else {
1168                 for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
1169                         if (strcmp(crypt_stat->cipher, map[i].cipher_str) == 0){
1170                                 code = map[i].cipher_code;
1171                                 break;
1172                         }
1173         }
1174         return code;
1175 }
1176
1177 /**
1178  * ecryptfs_cipher_code_to_string
1179  * @str: Destination to write out the cipher name
1180  * @cipher_code: The code to convert to cipher name string
1181  *
1182  * Returns zero on success
1183  */
1184 int ecryptfs_cipher_code_to_string(char *str, u16 cipher_code)
1185 {
1186         int rc = 0;
1187         int i;
1188
1189         str[0] = '\0';
1190         for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
1191                 if (cipher_code == ecryptfs_cipher_code_str_map[i].cipher_code)
1192                         strcpy(str, ecryptfs_cipher_code_str_map[i].cipher_str);
1193         if (str[0] == '\0') {
1194                 ecryptfs_printk(KERN_WARNING, "Cipher code not recognized: "
1195                                 "[%d]\n", cipher_code);
1196                 rc = -EINVAL;
1197         }
1198         return rc;
1199 }
1200
1201 /**
1202  * ecryptfs_read_header_region
1203  * @data
1204  * @dentry
1205  * @nd
1206  *
1207  * Returns zero on success; non-zero otherwise
1208  */
1209 static int ecryptfs_read_header_region(char *data, struct dentry *dentry,
1210                                        struct vfsmount *mnt)
1211 {
1212         struct file *lower_file;
1213         mm_segment_t oldfs;
1214         int rc;
1215
1216         if ((rc = ecryptfs_open_lower_file(&lower_file, dentry, mnt,
1217                                            O_RDONLY))) {
1218                 printk(KERN_ERR
1219                        "Error opening lower_file to read header region\n");
1220                 goto out;
1221         }
1222         lower_file->f_pos = 0;
1223         oldfs = get_fs();
1224         set_fs(get_ds());
1225         /* For releases 0.1 and 0.2, all of the header information
1226          * fits in the first data extent-sized region. */
1227         rc = lower_file->f_op->read(lower_file, (char __user *)data,
1228                               ECRYPTFS_DEFAULT_EXTENT_SIZE, &lower_file->f_pos);
1229         set_fs(oldfs);
1230         if ((rc = ecryptfs_close_lower_file(lower_file))) {
1231                 printk(KERN_ERR "Error closing lower_file\n");
1232                 goto out;
1233         }
1234         rc = 0;
1235 out:
1236         return rc;
1237 }
1238
1239 int ecryptfs_read_and_validate_header_region(char *data, struct dentry *dentry,
1240                                              struct vfsmount *mnt)
1241 {
1242         int rc;
1243
1244         rc = ecryptfs_read_header_region(data, dentry, mnt);
1245         if (rc)
1246                 goto out;
1247         if (!contains_ecryptfs_marker(data + ECRYPTFS_FILE_SIZE_BYTES))
1248                 rc = -EINVAL;
1249 out:
1250         return rc;
1251 }
1252
1253
1254 void
1255 ecryptfs_write_header_metadata(char *virt,
1256                                struct ecryptfs_crypt_stat *crypt_stat,
1257                                size_t *written)
1258 {
1259         u32 header_extent_size;
1260         u16 num_header_extents_at_front;
1261
1262         header_extent_size = (u32)crypt_stat->header_extent_size;
1263         num_header_extents_at_front =
1264                 (u16)crypt_stat->num_header_extents_at_front;
1265         header_extent_size = cpu_to_be32(header_extent_size);
1266         memcpy(virt, &header_extent_size, 4);
1267         virt += 4;
1268         num_header_extents_at_front = cpu_to_be16(num_header_extents_at_front);
1269         memcpy(virt, &num_header_extents_at_front, 2);
1270         (*written) = 6;
1271 }
1272
1273 struct kmem_cache *ecryptfs_header_cache_0;
1274 struct kmem_cache *ecryptfs_header_cache_1;
1275 struct kmem_cache *ecryptfs_header_cache_2;
1276
1277 /**
1278  * ecryptfs_write_headers_virt
1279  * @page_virt
1280  * @crypt_stat
1281  * @ecryptfs_dentry
1282  *
1283  * Format version: 1
1284  *
1285  *   Header Extent:
1286  *     Octets 0-7:        Unencrypted file size (big-endian)
1287  *     Octets 8-15:       eCryptfs special marker
1288  *     Octets 16-19:      Flags
1289  *      Octet 16:         File format version number (between 0 and 255)
1290  *      Octets 17-18:     Reserved
1291  *      Octet 19:         Bit 1 (lsb): Reserved
1292  *                        Bit 2: Encrypted?
1293  *                        Bits 3-8: Reserved
1294  *     Octets 20-23:      Header extent size (big-endian)
1295  *     Octets 24-25:      Number of header extents at front of file
1296  *                        (big-endian)
1297  *     Octet  26:         Begin RFC 2440 authentication token packet set
1298  *   Data Extent 0:
1299  *     Lower data (CBC encrypted)
1300  *   Data Extent 1:
1301  *     Lower data (CBC encrypted)
1302  *   ...
1303  *
1304  * Returns zero on success
1305  */
1306 static int ecryptfs_write_headers_virt(char *page_virt, size_t *size,
1307                                        struct ecryptfs_crypt_stat *crypt_stat,
1308                                        struct dentry *ecryptfs_dentry)
1309 {
1310         int rc;
1311         size_t written;
1312         size_t offset;
1313
1314         offset = ECRYPTFS_FILE_SIZE_BYTES;
1315         write_ecryptfs_marker((page_virt + offset), &written);
1316         offset += written;
1317         write_ecryptfs_flags((page_virt + offset), crypt_stat, &written);
1318         offset += written;
1319         ecryptfs_write_header_metadata((page_virt + offset), crypt_stat,
1320                                        &written);
1321         offset += written;
1322         rc = ecryptfs_generate_key_packet_set((page_virt + offset), crypt_stat,
1323                                               ecryptfs_dentry, &written,
1324                                               PAGE_CACHE_SIZE - offset);
1325         if (rc)
1326                 ecryptfs_printk(KERN_WARNING, "Error generating key packet "
1327                                 "set; rc = [%d]\n", rc);
1328         if (size) {
1329                 offset += written;
1330                 *size = offset;
1331         }
1332         return rc;
1333 }
1334
1335 static int ecryptfs_write_metadata_to_contents(struct ecryptfs_crypt_stat *crypt_stat,
1336                                                struct file *lower_file,
1337                                                char *page_virt)
1338 {
1339         mm_segment_t oldfs;
1340         int current_header_page;
1341         int header_pages;
1342         ssize_t size;
1343         int rc = 0;
1344
1345         lower_file->f_pos = 0;
1346         oldfs = get_fs();
1347         set_fs(get_ds());
1348         size = vfs_write(lower_file, (char __user *)page_virt, PAGE_CACHE_SIZE,
1349                          &lower_file->f_pos);
1350         if (size < 0) {
1351                 rc = (int)size;
1352                 printk(KERN_ERR "Error attempting to write lower page; "
1353                        "rc = [%d]\n", rc);
1354                 set_fs(oldfs);
1355                 goto out;
1356         }
1357         header_pages = ((crypt_stat->header_extent_size
1358                          * crypt_stat->num_header_extents_at_front)
1359                         / PAGE_CACHE_SIZE);
1360         memset(page_virt, 0, PAGE_CACHE_SIZE);
1361         current_header_page = 1;
1362         while (current_header_page < header_pages) {
1363                 size = vfs_write(lower_file, (char __user *)page_virt,
1364                                  PAGE_CACHE_SIZE, &lower_file->f_pos);
1365                 if (size < 0) {
1366                         rc = (int)size;
1367                         printk(KERN_ERR "Error attempting to write lower page; "
1368                                "rc = [%d]\n", rc);
1369                         set_fs(oldfs);
1370                         goto out;
1371                 }
1372                 current_header_page++;
1373         }
1374         set_fs(oldfs);
1375 out:
1376         return rc;
1377 }
1378
1379 static int ecryptfs_write_metadata_to_xattr(struct dentry *ecryptfs_dentry,
1380                                             struct ecryptfs_crypt_stat *crypt_stat,
1381                                             char *page_virt, size_t size)
1382 {
1383         int rc;
1384
1385         rc = ecryptfs_setxattr(ecryptfs_dentry, ECRYPTFS_XATTR_NAME, page_virt,
1386                                size, 0);
1387         return rc;
1388 }
1389
1390 /**
1391  * ecryptfs_write_metadata
1392  * @lower_file: The lower file struct, which was returned from dentry_open
1393  *
1394  * Write the file headers out.  This will likely involve a userspace
1395  * callout, in which the session key is encrypted with one or more
1396  * public keys and/or the passphrase necessary to do the encryption is
1397  * retrieved via a prompt.  Exactly what happens at this point should
1398  * be policy-dependent.
1399  *
1400  * Returns zero on success; non-zero on error
1401  */
1402 int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry,
1403                             struct file *lower_file)
1404 {
1405         struct ecryptfs_crypt_stat *crypt_stat;
1406         char *page_virt;
1407         size_t size;
1408         int rc = 0;
1409
1410         crypt_stat = &ecryptfs_inode_to_private(
1411                 ecryptfs_dentry->d_inode)->crypt_stat;
1412         if (likely(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
1413                 if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
1414                         ecryptfs_printk(KERN_DEBUG, "Key is "
1415                                         "invalid; bailing out\n");
1416                         rc = -EINVAL;
1417                         goto out;
1418                 }
1419         } else {
1420                 rc = -EINVAL;
1421                 ecryptfs_printk(KERN_WARNING,
1422                                 "Called with crypt_stat->encrypted == 0\n");
1423                 goto out;
1424         }
1425         /* Released in this function */
1426         page_virt = kmem_cache_zalloc(ecryptfs_header_cache_0, GFP_USER);
1427         if (!page_virt) {
1428                 ecryptfs_printk(KERN_ERR, "Out of memory\n");
1429                 rc = -ENOMEM;
1430                 goto out;
1431         }
1432         rc = ecryptfs_write_headers_virt(page_virt, &size, crypt_stat,
1433                                          ecryptfs_dentry);
1434         if (unlikely(rc)) {
1435                 ecryptfs_printk(KERN_ERR, "Error whilst writing headers\n");
1436                 memset(page_virt, 0, PAGE_CACHE_SIZE);
1437                 goto out_free;
1438         }
1439         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
1440                 rc = ecryptfs_write_metadata_to_xattr(ecryptfs_dentry,
1441                                                       crypt_stat, page_virt,
1442                                                       size);
1443         else
1444                 rc = ecryptfs_write_metadata_to_contents(crypt_stat, lower_file,
1445                                                          page_virt);
1446         if (rc) {
1447                 printk(KERN_ERR "Error writing metadata out to lower file; "
1448                        "rc = [%d]\n", rc);
1449                 goto out_free;
1450         }
1451 out_free:
1452         kmem_cache_free(ecryptfs_header_cache_0, page_virt);
1453 out:
1454         return rc;
1455 }
1456
1457 #define ECRYPTFS_DONT_VALIDATE_HEADER_SIZE 0
1458 #define ECRYPTFS_VALIDATE_HEADER_SIZE 1
1459 static int parse_header_metadata(struct ecryptfs_crypt_stat *crypt_stat,
1460                                  char *virt, int *bytes_read,
1461                                  int validate_header_size)
1462 {
1463         int rc = 0;
1464         u32 header_extent_size;
1465         u16 num_header_extents_at_front;
1466
1467         memcpy(&header_extent_size, virt, 4);
1468         header_extent_size = be32_to_cpu(header_extent_size);
1469         virt += 4;
1470         memcpy(&num_header_extents_at_front, virt, 2);
1471         num_header_extents_at_front = be16_to_cpu(num_header_extents_at_front);
1472         crypt_stat->header_extent_size = (int)header_extent_size;
1473         crypt_stat->num_header_extents_at_front =
1474                 (int)num_header_extents_at_front;
1475         (*bytes_read) = 6;
1476         if ((validate_header_size == ECRYPTFS_VALIDATE_HEADER_SIZE)
1477             && ((crypt_stat->header_extent_size
1478                  * crypt_stat->num_header_extents_at_front)
1479                 < ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)) {
1480                 rc = -EINVAL;
1481                 ecryptfs_printk(KERN_WARNING, "Invalid header extent size: "
1482                                 "[%d]\n", crypt_stat->header_extent_size);
1483         }
1484         return rc;
1485 }
1486
1487 /**
1488  * set_default_header_data
1489  *
1490  * For version 0 file format; this function is only for backwards
1491  * compatibility for files created with the prior versions of
1492  * eCryptfs.
1493  */
1494 static void set_default_header_data(struct ecryptfs_crypt_stat *crypt_stat)
1495 {
1496         crypt_stat->header_extent_size = 4096;
1497         crypt_stat->num_header_extents_at_front = 1;
1498 }
1499
1500 /**
1501  * ecryptfs_read_headers_virt
1502  *
1503  * Read/parse the header data. The header format is detailed in the
1504  * comment block for the ecryptfs_write_headers_virt() function.
1505  *
1506  * Returns zero on success
1507  */
1508 static int ecryptfs_read_headers_virt(char *page_virt,
1509                                       struct ecryptfs_crypt_stat *crypt_stat,
1510                                       struct dentry *ecryptfs_dentry,
1511                                       int validate_header_size)
1512 {
1513         int rc = 0;
1514         int offset;
1515         int bytes_read;
1516
1517         ecryptfs_set_default_sizes(crypt_stat);
1518         crypt_stat->mount_crypt_stat = &ecryptfs_superblock_to_private(
1519                 ecryptfs_dentry->d_sb)->mount_crypt_stat;
1520         offset = ECRYPTFS_FILE_SIZE_BYTES;
1521         rc = contains_ecryptfs_marker(page_virt + offset);
1522         if (rc == 0) {
1523                 rc = -EINVAL;
1524                 goto out;
1525         }
1526         offset += MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
1527         rc = ecryptfs_process_flags(crypt_stat, (page_virt + offset),
1528                                     &bytes_read);
1529         if (rc) {
1530                 ecryptfs_printk(KERN_WARNING, "Error processing flags\n");
1531                 goto out;
1532         }
1533         if (crypt_stat->file_version > ECRYPTFS_SUPPORTED_FILE_VERSION) {
1534                 ecryptfs_printk(KERN_WARNING, "File version is [%d]; only "
1535                                 "file version [%d] is supported by this "
1536                                 "version of eCryptfs\n",
1537                                 crypt_stat->file_version,
1538                                 ECRYPTFS_SUPPORTED_FILE_VERSION);
1539                 rc = -EINVAL;
1540                 goto out;
1541         }
1542         offset += bytes_read;
1543         if (crypt_stat->file_version >= 1) {
1544                 rc = parse_header_metadata(crypt_stat, (page_virt + offset),
1545                                            &bytes_read, validate_header_size);
1546                 if (rc) {
1547                         ecryptfs_printk(KERN_WARNING, "Error reading header "
1548                                         "metadata; rc = [%d]\n", rc);
1549                 }
1550                 offset += bytes_read;
1551         } else
1552                 set_default_header_data(crypt_stat);
1553         rc = ecryptfs_parse_packet_set(crypt_stat, (page_virt + offset),
1554                                        ecryptfs_dentry);
1555 out:
1556         return rc;
1557 }
1558
1559 /**
1560  * ecryptfs_read_xattr_region
1561  *
1562  * Attempts to read the crypto metadata from the extended attribute
1563  * region of the lower file.
1564  */
1565 int ecryptfs_read_xattr_region(char *page_virt, struct dentry *ecryptfs_dentry)
1566 {
1567         ssize_t size;
1568         int rc = 0;
1569
1570         size = ecryptfs_getxattr(ecryptfs_dentry, ECRYPTFS_XATTR_NAME,
1571                                  page_virt, ECRYPTFS_DEFAULT_EXTENT_SIZE);
1572         if (size < 0) {
1573                 printk(KERN_DEBUG "Error attempting to read the [%s] "
1574                        "xattr from the lower file; return value = [%zd]\n",
1575                        ECRYPTFS_XATTR_NAME, size);
1576                 rc = -EINVAL;
1577                 goto out;
1578         }
1579 out:
1580         return rc;
1581 }
1582
1583 int ecryptfs_read_and_validate_xattr_region(char *page_virt,
1584                                             struct dentry *ecryptfs_dentry)
1585 {
1586         int rc;
1587
1588         rc = ecryptfs_read_xattr_region(page_virt, ecryptfs_dentry);
1589         if (rc)
1590                 goto out;
1591         if (!contains_ecryptfs_marker(page_virt + ECRYPTFS_FILE_SIZE_BYTES)) {
1592                 printk(KERN_WARNING "Valid data found in [%s] xattr, but "
1593                         "the marker is invalid\n", ECRYPTFS_XATTR_NAME);
1594                 rc = -EINVAL;
1595         }
1596 out:
1597         return rc;
1598 }
1599
1600 /**
1601  * ecryptfs_read_metadata
1602  *
1603  * Common entry point for reading file metadata. From here, we could
1604  * retrieve the header information from the header region of the file,
1605  * the xattr region of the file, or some other repostory that is
1606  * stored separately from the file itself. The current implementation
1607  * supports retrieving the metadata information from the file contents
1608  * and from the xattr region.
1609  *
1610  * Returns zero if valid headers found and parsed; non-zero otherwise
1611  */
1612 int ecryptfs_read_metadata(struct dentry *ecryptfs_dentry,
1613                            struct file *lower_file)
1614 {
1615         int rc = 0;
1616         char *page_virt = NULL;
1617         mm_segment_t oldfs;
1618         ssize_t bytes_read;
1619         struct ecryptfs_crypt_stat *crypt_stat =
1620             &ecryptfs_inode_to_private(ecryptfs_dentry->d_inode)->crypt_stat;
1621         struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
1622                 &ecryptfs_superblock_to_private(
1623                         ecryptfs_dentry->d_sb)->mount_crypt_stat;
1624
1625         ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
1626                                                       mount_crypt_stat);
1627         /* Read the first page from the underlying file */
1628         page_virt = kmem_cache_alloc(ecryptfs_header_cache_1, GFP_USER);
1629         if (!page_virt) {
1630                 rc = -ENOMEM;
1631                 ecryptfs_printk(KERN_ERR, "Unable to allocate page_virt\n");
1632                 goto out;
1633         }
1634         lower_file->f_pos = 0;
1635         oldfs = get_fs();
1636         set_fs(get_ds());
1637         bytes_read = lower_file->f_op->read(lower_file,
1638                                             (char __user *)page_virt,
1639                                             ECRYPTFS_DEFAULT_EXTENT_SIZE,
1640                                             &lower_file->f_pos);
1641         set_fs(oldfs);
1642         if (bytes_read != ECRYPTFS_DEFAULT_EXTENT_SIZE) {
1643                 rc = -EINVAL;
1644                 goto out;
1645         }
1646         rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
1647                                         ecryptfs_dentry,
1648                                         ECRYPTFS_VALIDATE_HEADER_SIZE);
1649         if (rc) {
1650                 rc = ecryptfs_read_xattr_region(page_virt,
1651                                                 ecryptfs_dentry);
1652                 if (rc) {
1653                         printk(KERN_DEBUG "Valid eCryptfs headers not found in "
1654                                "file header region or xattr region\n");
1655                         rc = -EINVAL;
1656                         goto out;
1657                 }
1658                 rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
1659                                                 ecryptfs_dentry,
1660                                                 ECRYPTFS_DONT_VALIDATE_HEADER_SIZE);
1661                 if (rc) {
1662                         printk(KERN_DEBUG "Valid eCryptfs headers not found in "
1663                                "file xattr region either\n");
1664                         rc = -EINVAL;
1665                 }
1666                 if (crypt_stat->mount_crypt_stat->flags
1667                     & ECRYPTFS_XATTR_METADATA_ENABLED) {
1668                         crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
1669                 } else {
1670                         printk(KERN_WARNING "Attempt to access file with "
1671                                "crypto metadata only in the extended attribute "
1672                                "region, but eCryptfs was mounted without "
1673                                "xattr support enabled. eCryptfs will not treat "
1674                                "this like an encrypted file.\n");
1675                         rc = -EINVAL;
1676                 }
1677         }
1678 out:
1679         if (page_virt) {
1680                 memset(page_virt, 0, PAGE_CACHE_SIZE);
1681                 kmem_cache_free(ecryptfs_header_cache_1, page_virt);
1682         }
1683         return rc;
1684 }
1685
1686 /**
1687  * ecryptfs_encode_filename - converts a plaintext file name to cipher text
1688  * @crypt_stat: The crypt_stat struct associated with the file anem to encode
1689  * @name: The plaintext name
1690  * @length: The length of the plaintext
1691  * @encoded_name: The encypted name
1692  *
1693  * Encrypts and encodes a filename into something that constitutes a
1694  * valid filename for a filesystem, with printable characters.
1695  *
1696  * We assume that we have a properly initialized crypto context,
1697  * pointed to by crypt_stat->tfm.
1698  *
1699  * TODO: Implement filename decoding and decryption here, in place of
1700  * memcpy. We are keeping the framework around for now to (1)
1701  * facilitate testing of the components needed to implement filename
1702  * encryption and (2) to provide a code base from which other
1703  * developers in the community can easily implement this feature.
1704  *
1705  * Returns the length of encoded filename; negative if error
1706  */
1707 int
1708 ecryptfs_encode_filename(struct ecryptfs_crypt_stat *crypt_stat,
1709                          const char *name, int length, char **encoded_name)
1710 {
1711         int error = 0;
1712
1713         (*encoded_name) = kmalloc(length + 2, GFP_KERNEL);
1714         if (!(*encoded_name)) {
1715                 error = -ENOMEM;
1716                 goto out;
1717         }
1718         /* TODO: Filename encryption is a scheduled feature for a
1719          * future version of eCryptfs. This function is here only for
1720          * the purpose of providing a framework for other developers
1721          * to easily implement filename encryption. Hint: Replace this
1722          * memcpy() with a call to encrypt and encode the
1723          * filename, the set the length accordingly. */
1724         memcpy((void *)(*encoded_name), (void *)name, length);
1725         (*encoded_name)[length] = '\0';
1726         error = length + 1;
1727 out:
1728         return error;
1729 }
1730
1731 /**
1732  * ecryptfs_decode_filename - converts the cipher text name to plaintext
1733  * @crypt_stat: The crypt_stat struct associated with the file
1734  * @name: The filename in cipher text
1735  * @length: The length of the cipher text name
1736  * @decrypted_name: The plaintext name
1737  *
1738  * Decodes and decrypts the filename.
1739  *
1740  * We assume that we have a properly initialized crypto context,
1741  * pointed to by crypt_stat->tfm.
1742  *
1743  * TODO: Implement filename decoding and decryption here, in place of
1744  * memcpy. We are keeping the framework around for now to (1)
1745  * facilitate testing of the components needed to implement filename
1746  * encryption and (2) to provide a code base from which other
1747  * developers in the community can easily implement this feature.
1748  *
1749  * Returns the length of decoded filename; negative if error
1750  */
1751 int
1752 ecryptfs_decode_filename(struct ecryptfs_crypt_stat *crypt_stat,
1753                          const char *name, int length, char **decrypted_name)
1754 {
1755         int error = 0;
1756
1757         (*decrypted_name) = kmalloc(length + 2, GFP_KERNEL);
1758         if (!(*decrypted_name)) {
1759                 error = -ENOMEM;
1760                 goto out;
1761         }
1762         /* TODO: Filename encryption is a scheduled feature for a
1763          * future version of eCryptfs. This function is here only for
1764          * the purpose of providing a framework for other developers
1765          * to easily implement filename encryption. Hint: Replace this
1766          * memcpy() with a call to decode and decrypt the
1767          * filename, the set the length accordingly. */
1768         memcpy((void *)(*decrypted_name), (void *)name, length);
1769         (*decrypted_name)[length + 1] = '\0';   /* Only for convenience
1770                                                  * in printing out the
1771                                                  * string in debug
1772                                                  * messages */
1773         error = length;
1774 out:
1775         return error;
1776 }
1777
1778 /**
1779  * ecryptfs_process_cipher - Perform cipher initialization.
1780  * @key_tfm: Crypto context for key material, set by this function
1781  * @cipher_name: Name of the cipher
1782  * @key_size: Size of the key in bytes
1783  *
1784  * Returns zero on success. Any crypto_tfm structs allocated here
1785  * should be released by other functions, such as on a superblock put
1786  * event, regardless of whether this function succeeds for fails.
1787  */
1788 int
1789 ecryptfs_process_cipher(struct crypto_blkcipher **key_tfm, char *cipher_name,
1790                         size_t *key_size)
1791 {
1792         char dummy_key[ECRYPTFS_MAX_KEY_BYTES];
1793         char *full_alg_name;
1794         int rc;
1795
1796         *key_tfm = NULL;
1797         if (*key_size > ECRYPTFS_MAX_KEY_BYTES) {
1798                 rc = -EINVAL;
1799                 printk(KERN_ERR "Requested key size is [%Zd] bytes; maximum "
1800                       "allowable is [%d]\n", *key_size, ECRYPTFS_MAX_KEY_BYTES);
1801                 goto out;
1802         }
1803         rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name, cipher_name,
1804                                                     "ecb");
1805         if (rc)
1806                 goto out;
1807         *key_tfm = crypto_alloc_blkcipher(full_alg_name, 0, CRYPTO_ALG_ASYNC);
1808         kfree(full_alg_name);
1809         if (IS_ERR(*key_tfm)) {
1810                 rc = PTR_ERR(*key_tfm);
1811                 printk(KERN_ERR "Unable to allocate crypto cipher with name "
1812                        "[%s]; rc = [%d]\n", cipher_name, rc);
1813                 goto out;
1814         }
1815         crypto_blkcipher_set_flags(*key_tfm, CRYPTO_TFM_REQ_WEAK_KEY);
1816         if (*key_size == 0) {
1817                 struct blkcipher_alg *alg = crypto_blkcipher_alg(*key_tfm);
1818
1819                 *key_size = alg->max_keysize;
1820         }
1821         get_random_bytes(dummy_key, *key_size);
1822         rc = crypto_blkcipher_setkey(*key_tfm, dummy_key, *key_size);
1823         if (rc) {
1824                 printk(KERN_ERR "Error attempting to set key of size [%Zd] for "
1825                        "cipher [%s]; rc = [%d]\n", *key_size, cipher_name, rc);
1826                 rc = -EINVAL;
1827                 goto out;
1828         }
1829 out:
1830         return rc;
1831 }