fs/ecryptfs/mmap.c

   1 /**
   2  * eCryptfs: Linux filesystem encryption layer
   3  * This is where eCryptfs coordinates the symmetric encryption and
   4  * decryption of the file data as it passes between the lower
   5  * encrypted file and the upper decrypted file.
   6  *
   7  * Copyright (C) 1997-2003 Erez Zadok
   8  * Copyright (C) 2001-2003 Stony Brook University
   9  * Copyright (C) 2004-2007 International Business Machines Corp.
  10  *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful, but
  18  * WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  25  * 02111-1307, USA.
  26  */
  27
  28 #include <linux/pagemap.h>
  29 #include <linux/writeback.h>
  30 #include <linux/page-flags.h>
  31 #include <linux/mount.h>
  32 #include <linux/file.h>
  33 #include <linux/crypto.h>
  34 #include <linux/scatterlist.h>
  35 #include <asm/unaligned.h>
  36 #include "ecryptfs_kernel.h"
  37
  38 /**
  39  * ecryptfs_get_locked_page
  40  *
  41  * Get one page from cache or lower f/s, return error otherwise.
  42  *
  43  * Returns locked and up-to-date page (if ok), with increased
  44  * refcnt.
  45  */
  46 struct page *ecryptfs_get_locked_page(struct file *file, loff_t index)
  47 {
  48         struct dentry *dentry;
  49         struct inode *inode;
  50         struct address_space *mapping;
  51         struct page *page;
  52
  53         dentry = file->f_path.dentry;
  54         inode = dentry->d_inode;
  55         mapping = inode->i_mapping;
  56         page = read_mapping_page(mapping, index, (void *)file);
  57         if (!IS_ERR(page))
  58                 lock_page(page);
  59         return page;
  60 }
  61
  62 /**
  63  * ecryptfs_writepage
  64  * @page: Page that is locked before this call is made
  65  *
  66  * Returns zero on success; non-zero otherwise
  67  */
  68 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
  69 {
  70         int rc;
  71
  72         rc = ecryptfs_encrypt_page(page);
  73         if (rc) {
  74                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
  75                                 "page (upper index [0x%.16x])\n", page->index);
  76                 ClearPageUptodate(page);
  77                 goto out;
  78         }
  79         SetPageUptodate(page);
  80         unlock_page(page);
  81 out:
  82         return rc;
  83 }
  84
  85 static void strip_xattr_flag(char *page_virt,
  86                              struct ecryptfs_crypt_stat *crypt_stat)
  87 {
  88         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
  89                 size_t written;
  90
  91                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
  92                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
  93                                                 &written);
  94                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
  95         }
  96 }
  97
  98 /**
  99  *   Header Extent:
 100  *     Octets 0-7:        Unencrypted file size (big-endian)
 101  *     Octets 8-15:       eCryptfs special marker
 102  *     Octets 16-19:      Flags
 103  *      Octet 16:         File format version number (between 0 and 255)
 104  *      Octets 17-18:     Reserved
 105  *      Octet 19:         Bit 1 (lsb): Reserved
 106  *                        Bit 2: Encrypted?
 107  *                        Bits 3-8: Reserved
 108  *     Octets 20-23:      Header extent size (big-endian)
 109  *     Octets 24-25:      Number of header extents at front of file
 110  *                        (big-endian)
 111  *     Octet  26:         Begin RFC 2440 authentication token packet set
 112  */
 113
 114 /**
 115  * ecryptfs_copy_up_encrypted_with_header
 116  * @page: Sort of a ``virtual'' representation of the encrypted lower
 117  *        file. The actual lower file does not have the metadata in
 118  *        the header. This is locked.
 119  * @crypt_stat: The eCryptfs inode's cryptographic context
 120  *
 121  * The ``view'' is the version of the file that userspace winds up
 122  * seeing, with the header information inserted.
 123  */
 124 static int
 125 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 126                                        struct ecryptfs_crypt_stat *crypt_stat)
 127 {
 128         loff_t extent_num_in_page = 0;
 129         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
 130                                        / crypt_stat->extent_size);
 131         int rc = 0;
 132
 133         while (extent_num_in_page < num_extents_per_page) {
 134                 loff_t view_extent_num = ((((loff_t)page->index)
 135                                            * num_extents_per_page)
 136                                           + extent_num_in_page);
 137                 size_t num_header_extents_at_front =
 138                         (crypt_stat->metadata_size / crypt_stat->extent_size);
 139
 140                 if (view_extent_num < num_header_extents_at_front) {
 141                         /* This is a header extent */
 142                         char *page_virt;
 143
 144                         page_virt = kmap_atomic(page, KM_USER0);
 145                         memset(page_virt, 0, PAGE_CACHE_SIZE);
 146                         /* TODO: Support more than one header extent */
 147                         if (view_extent_num == 0) {
 148                                 size_t written;
 149
 150                                 rc = ecryptfs_read_xattr_region(
 151                                         page_virt, page->mapping->host);
 152                                 strip_xattr_flag(page_virt + 16, crypt_stat);
 153                                 ecryptfs_write_header_metadata(page_virt + 20,
 154                                                                crypt_stat,
 155                                                                &written);
 156                         }
 157                         kunmap_atomic(page_virt, KM_USER0);
 158                         flush_dcache_page(page);
 159                         if (rc) {
 160                                 printk(KERN_ERR "%s: Error reading xattr "
 161                                        "region; rc = [%d]\n", __func__, rc);
 162                                 goto out;
 163                         }
 164                 } else {
 165                         /* This is an encrypted data extent */
 166                         loff_t lower_offset =
 167                                 ((view_extent_num * crypt_stat->extent_size)
 168                                  - crypt_stat->metadata_size);
 169
 170                         rc = ecryptfs_read_lower_page_segment(
 171                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
 172                                 (lower_offset & ~PAGE_CACHE_MASK),
 173                                 crypt_stat->extent_size, page->mapping->host);
 174                         if (rc) {
 175                                 printk(KERN_ERR "%s: Error attempting to read "
 176                                        "extent at offset [%lld] in the lower "
 177                                        "file; rc = [%d]\n", __func__,
 178                                        lower_offset, rc);
 179                                 goto out;
 180                         }
 181                 }
 182                 extent_num_in_page++;
 183         }
 184 out:
 185         return rc;
 186 }
 187
 188 /**
 189  * ecryptfs_readpage
 190  * @file: An eCryptfs file
 191  * @page: Page from eCryptfs inode mapping into which to stick the read data
 192  *
 193  * Read in a page, decrypting if necessary.
 194  *
 195  * Returns zero on success; non-zero on error.
 196  */
 197 static int ecryptfs_readpage(struct file *file, struct page *page)
 198 {
 199         struct ecryptfs_crypt_stat *crypt_stat =
 200                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 201         int rc = 0;
 202
 203         if (!crypt_stat
 204             || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 205             || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
 206                 ecryptfs_printk(KERN_DEBUG,
 207                                 "Passing through unencrypted page\n");
 208                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 209                                                       PAGE_CACHE_SIZE,
 210                                                       page->mapping->host);
 211         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 212                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 213                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 214                                                                     crypt_stat);
 215                         if (rc) {
 216                                 printk(KERN_ERR "%s: Error attempting to copy "
 217                                        "the encrypted content from the lower "
 218                                        "file whilst inserting the metadata "
 219                                        "from the xattr into the header; rc = "
 220                                        "[%d]\n", __func__, rc);
 221                                 goto out;
 222                         }
 223
 224                 } else {
 225                         rc = ecryptfs_read_lower_page_segment(
 226                                 page, page->index, 0, PAGE_CACHE_SIZE,
 227                                 page->mapping->host);
 228                         if (rc) {
 229                                 printk(KERN_ERR "Error reading page; rc = "
 230                                        "[%d]\n", rc);
 231                                 goto out;
 232                         }
 233                 }
 234         } else {
 235                 rc = ecryptfs_decrypt_page(page);
 236                 if (rc) {
 237                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 238                                         "rc = [%d]\n", rc);
 239                         goto out;
 240                 }
 241         }
 242 out:
 243         if (rc)
 244                 ClearPageUptodate(page);
 245         else
 246                 SetPageUptodate(page);
 247         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
 248                         page->index);
 249         unlock_page(page);
 250         return rc;
 251 }
 252
 253 /**
 254  * Called with lower inode mutex held.
 255  */
 256 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 257 {
 258         struct inode *inode = page->mapping->host;
 259         int end_byte_in_page;
 260
 261         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
 262                 goto out;
 263         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
 264         if (to > end_byte_in_page)
 265                 end_byte_in_page = to;
 266         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
 267 out:
 268         return 0;
 269 }
 270
 271 /**
 272  * ecryptfs_write_begin
 273  * @file: The eCryptfs file
 274  * @mapping: The eCryptfs object
 275  * @pos: The file offset at which to start writing
 276  * @len: Length of the write
 277  * @flags: Various flags
 278  * @pagep: Pointer to return the page
 279  * @fsdata: Pointer to return fs data (unused)
 280  *
 281  * This function must zero any hole we create
 282  *
 283  * Returns zero on success; non-zero otherwise
 284  */
 285 static int ecryptfs_write_begin(struct file *file,
 286                         struct address_space *mapping,
 287                         loff_t pos, unsigned len, unsigned flags,
 288                         struct page **pagep, void **fsdata)
 289 {
 290         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 291         struct page *page;
 292         loff_t prev_page_end_size;
 293         int rc = 0;
 294
 295         page = grab_cache_page_write_begin(mapping, index, flags);
 296         if (!page)
 297                 return -ENOMEM;
 298         *pagep = page;
 299
 300         if (!PageUptodate(page)) {
 301                 struct ecryptfs_crypt_stat *crypt_stat =
 302                         &ecryptfs_inode_to_private(
 303                                 file->f_path.dentry->d_inode)->crypt_stat;
 304
 305                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 306                     || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
 307                         rc = ecryptfs_read_lower_page_segment(
 308                                 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
 309                         if (rc) {
 310                                 printk(KERN_ERR "%s: Error attemping to read "
 311                                        "lower page segment; rc = [%d]\n",
 312                                        __func__, rc);
 313                                 ClearPageUptodate(page);
 314                                 goto out;
 315                         } else
 316                                 SetPageUptodate(page);
 317                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 318                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 319                                 rc = ecryptfs_copy_up_encrypted_with_header(
 320                                         page, crypt_stat);
 321                                 if (rc) {
 322                                         printk(KERN_ERR "%s: Error attempting "
 323                                                "to copy the encrypted content "
 324                                                "from the lower file whilst "
 325                                                "inserting the metadata from "
 326                                                "the xattr into the header; rc "
 327                                                "= [%d]\n", __func__, rc);
 328                                         ClearPageUptodate(page);
 329                                         goto out;
 330                                 }
 331                                 SetPageUptodate(page);
 332                         } else {
 333                                 rc = ecryptfs_read_lower_page_segment(
 334                                         page, index, 0, PAGE_CACHE_SIZE,
 335                                         mapping->host);
 336                                 if (rc) {
 337                                         printk(KERN_ERR "%s: Error reading "
 338                                                "page; rc = [%d]\n",
 339                                                __func__, rc);
 340                                         ClearPageUptodate(page);
 341                                         goto out;
 342                                 }
 343                                 SetPageUptodate(page);
 344                         }
 345                 } else {
 346                         rc = ecryptfs_decrypt_page(page);
 347                         if (rc) {
 348                                 printk(KERN_ERR "%s: Error decrypting page "
 349                                        "at index [%ld]; rc = [%d]\n",
 350                                        __func__, page->index, rc);
 351                                 ClearPageUptodate(page);
 352                                 goto out;
 353                         }
 354                         SetPageUptodate(page);
 355                 }
 356         }
 357         prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
 358         /* If creating a page or more of holes, zero them out via truncate.
 359          * Note, this will increase i_size. */
 360         if (index != 0) {
 361                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
 362                         rc = ecryptfs_truncate(file->f_path.dentry,
 363                                                prev_page_end_size);
 364                         if (rc) {
 365                                 printk(KERN_ERR "%s: Error on attempt to "
 366                                        "truncate to (higher) offset [%lld];"
 367                                        " rc = [%d]\n", __func__,
 368                                        prev_page_end_size, rc);
 369                                 goto out;
 370                         }
 371                 }
 372         }
 373         /* Writing to a new page, and creating a small hole from start
 374          * of page?  Zero it out. */
 375         if ((i_size_read(mapping->host) == prev_page_end_size)
 376             && (pos != 0))
 377                 zero_user(page, 0, PAGE_CACHE_SIZE);
 378 out:
 379         return rc;
 380 }
 381
 382 /**
 383  * ecryptfs_write_inode_size_to_header
 384  *
 385  * Writes the lower file size to the first 8 bytes of the header.
 386  *
 387  * Returns zero on success; non-zero on error.
 388  */
 389 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 390 {
 391         char *file_size_virt;
 392         int rc;
 393
 394         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 395         if (!file_size_virt) {
 396                 rc = -ENOMEM;
 397                 goto out;
 398         }
 399         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
 400         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 401                                   sizeof(u64));
 402         kfree(file_size_virt);
 403         if (rc < 0)
 404                 printk(KERN_ERR "%s: Error writing file size to header; "
 405                        "rc = [%d]\n", __func__, rc);
 406         else
 407                 rc = 0;
 408 out:
 409         return rc;
 410 }
 411
 412 struct kmem_cache *ecryptfs_xattr_cache;
 413
 414 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 415 {
 416         ssize_t size;
 417         void *xattr_virt;
 418         struct dentry *lower_dentry =
 419                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
 420         struct inode *lower_inode = lower_dentry->d_inode;
 421         int rc;
 422
 423         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
 424                 printk(KERN_WARNING
 425                        "No support for setting xattr in lower filesystem\n");
 426                 rc = -ENOSYS;
 427                 goto out;
 428         }
 429         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 430         if (!xattr_virt) {
 431                 printk(KERN_ERR "Out of memory whilst attempting to write "
 432                        "inode size to xattr\n");
 433                 rc = -ENOMEM;
 434                 goto out;
 435         }
 436         mutex_lock(&lower_inode->i_mutex);
 437         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 438                                            xattr_virt, PAGE_CACHE_SIZE);
 439         if (size < 0)
 440                 size = 8;
 441         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 442         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 443                                          xattr_virt, size, 0);
 444         mutex_unlock(&lower_inode->i_mutex);
 445         if (rc)
 446                 printk(KERN_ERR "Error whilst attempting to write inode size "
 447                        "to lower file xattr; rc = [%d]\n", rc);
 448         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 449 out:
 450         return rc;
 451 }
 452
 453 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 454 {
 455         struct ecryptfs_crypt_stat *crypt_stat;
 456
 457         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 458         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
 459         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 460                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 461         else
 462                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 463 }
 464
 465 /**
 466  * ecryptfs_write_end
 467  * @file: The eCryptfs file object
 468  * @mapping: The eCryptfs object
 469  * @pos: The file position
 470  * @len: The length of the data (unused)
 471  * @copied: The amount of data copied
 472  * @page: The eCryptfs page
 473  * @fsdata: The fsdata (unused)
 474  *
 475  * This is where we encrypt the data and pass the encrypted data to
 476  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 477  * entire underlying packets.
 478  */
 479 static int ecryptfs_write_end(struct file *file,
 480                         struct address_space *mapping,
 481                         loff_t pos, unsigned len, unsigned copied,
 482                         struct page *page, void *fsdata)
 483 {
 484         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 485         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 486         unsigned to = from + copied;
 487         struct inode *ecryptfs_inode = mapping->host;
 488         struct ecryptfs_crypt_stat *crypt_stat =
 489                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 490         int rc;
 491
 492         if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
 493                 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
 494                         "crypt_stat at memory location [%p]\n", crypt_stat);
 495                 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
 496         } else
 497                 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
 498         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 499                         "(page w/ index = [0x%.16x], to = [%d])\n", index, to);
 500         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 501                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
 502                                                        to);
 503                 if (!rc) {
 504                         rc = copied;
 505                         fsstack_copy_inode_size(ecryptfs_inode,
 506                                 ecryptfs_inode_to_lower(ecryptfs_inode));
 507                 }
 508                 goto out;
 509         }
 510         /* Fills in zeros if 'to' goes beyond inode size */
 511         rc = fill_zeros_to_end_of_page(page, to);
 512         if (rc) {
 513                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 514                         "zeros in page with index = [0x%.16x]\n", index);
 515                 goto out;
 516         }
 517         rc = ecryptfs_encrypt_page(page);
 518         if (rc) {
 519                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 520                                 "index [0x%.16x])\n", index);
 521                 goto out;
 522         }
 523         if (pos + copied > i_size_read(ecryptfs_inode)) {
 524                 i_size_write(ecryptfs_inode, pos + copied);
 525                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 526                                 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
 527         }
 528         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 529         if (rc)
 530                 printk(KERN_ERR "Error writing inode size to metadata; "
 531                        "rc = [%d]\n", rc);
 532         else
 533                 rc = copied;
 534 out:
 535         unlock_page(page);
 536         page_cache_release(page);
 537         return rc;
 538 }
 539
 540 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 541 {
 542         int rc = 0;
 543         struct inode *inode;
 544         struct inode *lower_inode;
 545
 546         inode = (struct inode *)mapping->host;
 547         lower_inode = ecryptfs_inode_to_lower(inode);
 548         if (lower_inode->i_mapping->a_ops->bmap)
 549                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
 550                                                          block);
 551         return rc;
 552 }
 553
 554 const struct address_space_operations ecryptfs_aops = {
 555         .writepage = ecryptfs_writepage,
 556         .readpage = ecryptfs_readpage,
 557         .write_begin = ecryptfs_write_begin,
 558         .write_end = ecryptfs_write_end,
 559         .bmap = ecryptfs_bmap,
 560 };