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