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 <linux/slab.h>
  36 #include <asm/unaligned.h>
  37 #include "ecryptfs_kernel.h"
  38
  39 /**
  40  * ecryptfs_get_locked_page
  41  *
  42  * Get one page from cache or lower f/s, return error otherwise.
  43  *
  44  * Returns locked and up-to-date page (if ok), with increased
  45  * refcnt.
  46  */
  47 struct page *ecryptfs_get_locked_page(struct file *file, loff_t index)
  48 {
  49         struct dentry *dentry;
  50         struct inode *inode;
  51         struct address_space *mapping;
  52         struct page *page;
  53
  54         dentry = file->f_path.dentry;
  55         inode = dentry->d_inode;
  56         mapping = inode->i_mapping;
  57         page = read_mapping_page(mapping, index, (void *)file);
  58         if (!IS_ERR(page))
  59                 lock_page(page);
  60         return page;
  61 }
  62
  63 /**
  64  * ecryptfs_writepage
  65  * @page: Page that is locked before this call is made
  66  *
  67  * Returns zero on success; non-zero otherwise
  68  */
  69 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
  70 {
  71         int rc;
  72
  73         rc = ecryptfs_encrypt_page(page);
  74         if (rc) {
  75                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
  76                                 "page (upper index [0x%.16x])\n", page->index);
  77                 ClearPageUptodate(page);
  78                 goto out;
  79         }
  80         SetPageUptodate(page);
  81         unlock_page(page);
  82 out:
  83         return rc;
  84 }
  85
  86 static void strip_xattr_flag(char *page_virt,
  87                              struct ecryptfs_crypt_stat *crypt_stat)
  88 {
  89         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
  90                 size_t written;
  91
  92                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
  93                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
  94                                                 &written);
  95                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
  96         }
  97 }
  98
  99 /**
 100  *   Header Extent:
 101  *     Octets 0-7:        Unencrypted file size (big-endian)
 102  *     Octets 8-15:       eCryptfs special marker
 103  *     Octets 16-19:      Flags
 104  *      Octet 16:         File format version number (between 0 and 255)
 105  *      Octets 17-18:     Reserved
 106  *      Octet 19:         Bit 1 (lsb): Reserved
 107  *                        Bit 2: Encrypted?
 108  *                        Bits 3-8: Reserved
 109  *     Octets 20-23:      Header extent size (big-endian)
 110  *     Octets 24-25:      Number of header extents at front of file
 111  *                        (big-endian)
 112  *     Octet  26:         Begin RFC 2440 authentication token packet set
 113  */
 114
 115 /**
 116  * ecryptfs_copy_up_encrypted_with_header
 117  * @page: Sort of a ``virtual'' representation of the encrypted lower
 118  *        file. The actual lower file does not have the metadata in
 119  *        the header. This is locked.
 120  * @crypt_stat: The eCryptfs inode's cryptographic context
 121  *
 122  * The ``view'' is the version of the file that userspace winds up
 123  * seeing, with the header information inserted.
 124  */
 125 static int
 126 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 127                                        struct ecryptfs_crypt_stat *crypt_stat)
 128 {
 129         loff_t extent_num_in_page = 0;
 130         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
 131                                        / crypt_stat->extent_size);
 132         int rc = 0;
 133
 134         while (extent_num_in_page < num_extents_per_page) {
 135                 loff_t view_extent_num = ((((loff_t)page->index)
 136                                            * num_extents_per_page)
 137                                           + extent_num_in_page);
 138                 size_t num_header_extents_at_front =
 139                         (crypt_stat->metadata_size / crypt_stat->extent_size);
 140
 141                 if (view_extent_num < num_header_extents_at_front) {
 142                         /* This is a header extent */
 143                         char *page_virt;
 144
 145                         page_virt = kmap_atomic(page, KM_USER0);
 146                         memset(page_virt, 0, PAGE_CACHE_SIZE);
 147                         /* TODO: Support more than one header extent */
 148                         if (view_extent_num == 0) {
 149                                 size_t written;
 150
 151                                 rc = ecryptfs_read_xattr_region(
 152                                         page_virt, page->mapping->host);
 153                                 strip_xattr_flag(page_virt + 16, crypt_stat);
 154                                 ecryptfs_write_header_metadata(page_virt + 20,
 155                                                                crypt_stat,
 156                                                                &written);
 157                         }
 158                         kunmap_atomic(page_virt, KM_USER0);
 159                         flush_dcache_page(page);
 160                         if (rc) {
 161                                 printk(KERN_ERR "%s: Error reading xattr "
 162                                        "region; rc = [%d]\n", __func__, rc);
 163                                 goto out;
 164                         }
 165                 } else {
 166                         /* This is an encrypted data extent */
 167                         loff_t lower_offset =
 168                                 ((view_extent_num * crypt_stat->extent_size)
 169                                  - crypt_stat->metadata_size);
 170
 171                         rc = ecryptfs_read_lower_page_segment(
 172                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
 173                                 (lower_offset & ~PAGE_CACHE_MASK),
 174                                 crypt_stat->extent_size, page->mapping->host);
 175                         if (rc) {
 176                                 printk(KERN_ERR "%s: Error attempting to read "
 177                                        "extent at offset [%lld] in the lower "
 178                                        "file; rc = [%d]\n", __func__,
 179                                        lower_offset, rc);
 180                                 goto out;
 181                         }
 182                 }
 183                 extent_num_in_page++;
 184         }
 185 out:
 186         return rc;
 187 }
 188
 189 /**
 190  * ecryptfs_readpage
 191  * @file: An eCryptfs file
 192  * @page: Page from eCryptfs inode mapping into which to stick the read data
 193  *
 194  * Read in a page, decrypting if necessary.
 195  *
 196  * Returns zero on success; non-zero on error.
 197  */
 198 static int ecryptfs_readpage(struct file *file, struct page *page)
 199 {
 200         struct ecryptfs_crypt_stat *crypt_stat =
 201                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 202         int rc = 0;
 203
 204         if (!crypt_stat
 205             || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 206             || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
 207                 ecryptfs_printk(KERN_DEBUG,
 208                                 "Passing through unencrypted page\n");
 209                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 210                                                       PAGE_CACHE_SIZE,
 211                                                       page->mapping->host);
 212         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 213                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 214                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 215                                                                     crypt_stat);
 216                         if (rc) {
 217                                 printk(KERN_ERR "%s: Error attempting to copy "
 218                                        "the encrypted content from the lower "
 219                                        "file whilst inserting the metadata "
 220                                        "from the xattr into the header; rc = "
 221                                        "[%d]\n", __func__, rc);
 222                                 goto out;
 223                         }
 224
 225                 } else {
 226                         rc = ecryptfs_read_lower_page_segment(
 227                                 page, page->index, 0, PAGE_CACHE_SIZE,
 228                                 page->mapping->host);
 229                         if (rc) {
 230                                 printk(KERN_ERR "Error reading page; rc = "
 231                                        "[%d]\n", rc);
 232                                 goto out;
 233                         }
 234                 }
 235         } else {
 236                 rc = ecryptfs_decrypt_page(page);
 237                 if (rc) {
 238                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 239                                         "rc = [%d]\n", rc);
 240                         goto out;
 241                 }
 242         }
 243 out:
 244         if (rc)
 245                 ClearPageUptodate(page);
 246         else
 247                 SetPageUptodate(page);
 248         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
 249                         page->index);
 250         unlock_page(page);
 251         return rc;
 252 }
 253
 254 /**
 255  * Called with lower inode mutex held.
 256  */
 257 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 258 {
 259         struct inode *inode = page->mapping->host;
 260         int end_byte_in_page;
 261
 262         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
 263                 goto out;
 264         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
 265         if (to > end_byte_in_page)
 266                 end_byte_in_page = to;
 267         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
 268 out:
 269         return 0;
 270 }
 271
 272 /**
 273  * ecryptfs_write_begin
 274  * @file: The eCryptfs file
 275  * @mapping: The eCryptfs object
 276  * @pos: The file offset at which to start writing
 277  * @len: Length of the write
 278  * @flags: Various flags
 279  * @pagep: Pointer to return the page
 280  * @fsdata: Pointer to return fs data (unused)
 281  *
 282  * This function must zero any hole we create
 283  *
 284  * Returns zero on success; non-zero otherwise
 285  */
 286 static int ecryptfs_write_begin(struct file *file,
 287                         struct address_space *mapping,
 288                         loff_t pos, unsigned len, unsigned flags,
 289                         struct page **pagep, void **fsdata)
 290 {
 291         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 292         struct page *page;
 293         loff_t prev_page_end_size;
 294         int rc = 0;
 295
 296         page = grab_cache_page_write_begin(mapping, index, flags);
 297         if (!page)
 298                 return -ENOMEM;
 299         *pagep = page;
 300
 301         if (!PageUptodate(page)) {
 302                 struct ecryptfs_crypt_stat *crypt_stat =
 303                         &ecryptfs_inode_to_private(
 304                                 file->f_path.dentry->d_inode)->crypt_stat;
 305
 306                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 307                     || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
 308                         rc = ecryptfs_read_lower_page_segment(
 309                                 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
 310                         if (rc) {
 311                                 printk(KERN_ERR "%s: Error attemping to read "
 312                                        "lower page segment; rc = [%d]\n",
 313                                        __func__, rc);
 314                                 ClearPageUptodate(page);
 315                                 goto out;
 316                         } else
 317                                 SetPageUptodate(page);
 318                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 319                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 320                                 rc = ecryptfs_copy_up_encrypted_with_header(
 321                                         page, crypt_stat);
 322                                 if (rc) {
 323                                         printk(KERN_ERR "%s: Error attempting "
 324                                                "to copy the encrypted content "
 325                                                "from the lower file whilst "
 326                                                "inserting the metadata from "
 327                                                "the xattr into the header; rc "
 328                                                "= [%d]\n", __func__, rc);
 329                                         ClearPageUptodate(page);
 330                                         goto out;
 331                                 }
 332                                 SetPageUptodate(page);
 333                         } else {
 334                                 rc = ecryptfs_read_lower_page_segment(
 335                                         page, index, 0, PAGE_CACHE_SIZE,
 336                                         mapping->host);
 337                                 if (rc) {
 338                                         printk(KERN_ERR "%s: Error reading "
 339                                                "page; rc = [%d]\n",
 340                                                __func__, rc);
 341                                         ClearPageUptodate(page);
 342                                         goto out;
 343                                 }
 344                                 SetPageUptodate(page);
 345                         }
 346                 } else {
 347                         rc = ecryptfs_decrypt_page(page);
 348                         if (rc) {
 349                                 printk(KERN_ERR "%s: Error decrypting page "
 350                                        "at index [%ld]; rc = [%d]\n",
 351                                        __func__, page->index, rc);
 352                                 ClearPageUptodate(page);
 353                                 goto out;
 354                         }
 355                         SetPageUptodate(page);
 356                 }
 357         }
 358         prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
 359         /* If creating a page or more of holes, zero them out via truncate.
 360          * Note, this will increase i_size. */
 361         if (index != 0) {
 362                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
 363                         rc = ecryptfs_truncate(file->f_path.dentry,
 364                                                prev_page_end_size);
 365                         if (rc) {
 366                                 printk(KERN_ERR "%s: Error on attempt to "
 367                                        "truncate to (higher) offset [%lld];"
 368                                        " rc = [%d]\n", __func__,
 369                                        prev_page_end_size, rc);
 370                                 goto out;
 371                         }
 372                 }
 373         }
 374         /* Writing to a new page, and creating a small hole from start
 375          * of page?  Zero it out. */
 376         if ((i_size_read(mapping->host) == prev_page_end_size)
 377             && (pos != 0))
 378                 zero_user(page, 0, PAGE_CACHE_SIZE);
 379 out:
 380         return rc;
 381 }
 382
 383 /**
 384  * ecryptfs_write_inode_size_to_header
 385  *
 386  * Writes the lower file size to the first 8 bytes of the header.
 387  *
 388  * Returns zero on success; non-zero on error.
 389  */
 390 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 391 {
 392         char *file_size_virt;
 393         int rc;
 394
 395         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 396         if (!file_size_virt) {
 397                 rc = -ENOMEM;
 398                 goto out;
 399         }
 400         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
 401         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 402                                   sizeof(u64));
 403         kfree(file_size_virt);
 404         if (rc < 0)
 405                 printk(KERN_ERR "%s: Error writing file size to header; "
 406                        "rc = [%d]\n", __func__, rc);
 407         else
 408                 rc = 0;
 409 out:
 410         return rc;
 411 }
 412
 413 struct kmem_cache *ecryptfs_xattr_cache;
 414
 415 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 416 {
 417         ssize_t size;
 418         void *xattr_virt;
 419         struct dentry *lower_dentry =
 420                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
 421         struct inode *lower_inode = lower_dentry->d_inode;
 422         int rc;
 423
 424         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
 425                 printk(KERN_WARNING
 426                        "No support for setting xattr in lower filesystem\n");
 427                 rc = -ENOSYS;
 428                 goto out;
 429         }
 430         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 431         if (!xattr_virt) {
 432                 printk(KERN_ERR "Out of memory whilst attempting to write "
 433                        "inode size to xattr\n");
 434                 rc = -ENOMEM;
 435                 goto out;
 436         }
 437         mutex_lock(&lower_inode->i_mutex);
 438         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 439                                            xattr_virt, PAGE_CACHE_SIZE);
 440         if (size < 0)
 441                 size = 8;
 442         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 443         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 444                                          xattr_virt, size, 0);
 445         mutex_unlock(&lower_inode->i_mutex);
 446         if (rc)
 447                 printk(KERN_ERR "Error whilst attempting to write inode size "
 448                        "to lower file xattr; rc = [%d]\n", rc);
 449         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 450 out:
 451         return rc;
 452 }
 453
 454 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 455 {
 456         struct ecryptfs_crypt_stat *crypt_stat;
 457
 458         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 459         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
 460         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 461                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 462         else
 463                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 464 }
 465
 466 /**
 467  * ecryptfs_write_end
 468  * @file: The eCryptfs file object
 469  * @mapping: The eCryptfs object
 470  * @pos: The file position
 471  * @len: The length of the data (unused)
 472  * @copied: The amount of data copied
 473  * @page: The eCryptfs page
 474  * @fsdata: The fsdata (unused)
 475  *
 476  * This is where we encrypt the data and pass the encrypted data to
 477  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 478  * entire underlying packets.
 479  */
 480 static int ecryptfs_write_end(struct file *file,
 481                         struct address_space *mapping,
 482                         loff_t pos, unsigned len, unsigned copied,
 483                         struct page *page, void *fsdata)
 484 {
 485         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 486         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 487         unsigned to = from + copied;
 488         struct inode *ecryptfs_inode = mapping->host;
 489         struct ecryptfs_crypt_stat *crypt_stat =
 490                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 491         int rc;
 492
 493         if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
 494                 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
 495                         "crypt_stat at memory location [%p]\n", crypt_stat);
 496                 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
 497         } else
 498                 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
 499         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 500                         "(page w/ index = [0x%.16x], to = [%d])\n", index, to);
 501         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 502                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
 503                                                        to);
 504                 if (!rc) {
 505                         rc = copied;
 506                         fsstack_copy_inode_size(ecryptfs_inode,
 507                                 ecryptfs_inode_to_lower(ecryptfs_inode));
 508                 }
 509                 goto out;
 510         }
 511         /* Fills in zeros if 'to' goes beyond inode size */
 512         rc = fill_zeros_to_end_of_page(page, to);
 513         if (rc) {
 514                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 515                         "zeros in page with index = [0x%.16x]\n", index);
 516                 goto out;
 517         }
 518         rc = ecryptfs_encrypt_page(page);
 519         if (rc) {
 520                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 521                                 "index [0x%.16x])\n", index);
 522                 goto out;
 523         }
 524         if (pos + copied > i_size_read(ecryptfs_inode)) {
 525                 i_size_write(ecryptfs_inode, pos + copied);
 526                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 527                                 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
 528         }
 529         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 530         if (rc)
 531                 printk(KERN_ERR "Error writing inode size to metadata; "
 532                        "rc = [%d]\n", rc);
 533         else
 534                 rc = copied;
 535 out:
 536         unlock_page(page);
 537         page_cache_release(page);
 538         return rc;
 539 }
 540
 541 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 542 {
 543         int rc = 0;
 544         struct inode *inode;
 545         struct inode *lower_inode;
 546
 547         inode = (struct inode *)mapping->host;
 548         lower_inode = ecryptfs_inode_to_lower(inode);
 549         if (lower_inode->i_mapping->a_ops->bmap)
 550                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
 551                                                          block);
 552         return rc;
 553 }
 554
 555 const struct address_space_operations ecryptfs_aops = {
 556         .writepage = ecryptfs_writepage,
 557         .readpage = ecryptfs_readpage,
 558         .write_begin = ecryptfs_write_begin,
 559         .write_end = ecryptfs_write_end,
 560         .bmap = ecryptfs_bmap,
 561 };