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