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