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