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