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 "ecryptfs_kernel.h"
  36
  37 /**
  38  * ecryptfs_get_locked_page
  39  *
  40  * Get one page from cache or lower f/s, return error otherwise.
  41  *
  42  * Returns locked and up-to-date page (if ok), with increased
  43  * refcnt.
  44  */
  45 struct page *ecryptfs_get_locked_page(struct file *file, loff_t index)
  46 {
  47         struct dentry *dentry;
  48         struct inode *inode;
  49         struct address_space *mapping;
  50         struct page *page;
  51
  52         dentry = file->f_path.dentry;
  53         inode = dentry->d_inode;
  54         mapping = inode->i_mapping;
  55         page = read_mapping_page(mapping, index, (void *)file);
  56         if (!IS_ERR(page))
  57                 lock_page(page);
  58         return page;
  59 }
  60
  61 /**
  62  * ecryptfs_writepage
  63  * @page: Page that is locked before this call is made
  64  *
  65  * Returns zero on success; non-zero otherwise
  66  */
  67 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
  68 {
  69         int rc;
  70
  71         rc = ecryptfs_encrypt_page(page);
  72         if (rc) {
  73                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
  74                                 "page (upper index [0x%.16x])\n", page->index);
  75                 ClearPageUptodate(page);
  76                 goto out;
  77         }
  78         SetPageUptodate(page);
  79         unlock_page(page);
  80 out:
  81         return rc;
  82 }
  83
  84 /**
  85  *   Header Extent:
  86  *     Octets 0-7:        Unencrypted file size (big-endian)
  87  *     Octets 8-15:       eCryptfs special marker
  88  *     Octets 16-19:      Flags
  89  *      Octet 16:         File format version number (between 0 and 255)
  90  *      Octets 17-18:     Reserved
  91  *      Octet 19:         Bit 1 (lsb): Reserved
  92  *                        Bit 2: Encrypted?
  93  *                        Bits 3-8: Reserved
  94  *     Octets 20-23:      Header extent size (big-endian)
  95  *     Octets 24-25:      Number of header extents at front of file
  96  *                        (big-endian)
  97  *     Octet  26:         Begin RFC 2440 authentication token packet set
  98  */
  99 static void set_header_info(char *page_virt,
 100                             struct ecryptfs_crypt_stat *crypt_stat)
 101 {
 102         size_t written;
 103         size_t save_num_header_bytes_at_front =
 104                 crypt_stat->num_header_bytes_at_front;
 105
 106         crypt_stat->num_header_bytes_at_front =
 107                 ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
 108         ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written);
 109         crypt_stat->num_header_bytes_at_front =
 110                 save_num_header_bytes_at_front;
 111 }
 112
 113 /**
 114  * ecryptfs_copy_up_encrypted_with_header
 115  * @page: Sort of a ``virtual'' representation of the encrypted lower
 116  *        file. The actual lower file does not have the metadata in
 117  *        the header. This is locked.
 118  * @crypt_stat: The eCryptfs inode's cryptographic context
 119  *
 120  * The ``view'' is the version of the file that userspace winds up
 121  * seeing, with the header information inserted.
 122  */
 123 static int
 124 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 125                                        struct ecryptfs_crypt_stat *crypt_stat)
 126 {
 127         loff_t extent_num_in_page = 0;
 128         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
 129                                        / crypt_stat->extent_size);
 130         int rc = 0;
 131
 132         while (extent_num_in_page < num_extents_per_page) {
 133                 loff_t view_extent_num = ((((loff_t)page->index)
 134                                            * num_extents_per_page)
 135                                           + extent_num_in_page);
 136                 size_t num_header_extents_at_front =
 137                         (crypt_stat->num_header_bytes_at_front
 138                          / crypt_stat->extent_size);
 139
 140                 if (view_extent_num < num_header_extents_at_front) {
 141                         /* This is a header extent */
 142                         char *page_virt;
 143
 144                         page_virt = kmap_atomic(page, KM_USER0);
 145                         memset(page_virt, 0, PAGE_CACHE_SIZE);
 146                         /* TODO: Support more than one header extent */
 147                         if (view_extent_num == 0) {
 148                                 rc = ecryptfs_read_xattr_region(
 149                                         page_virt, page->mapping->host);
 150                                 set_header_info(page_virt, crypt_stat);
 151                         }
 152                         kunmap_atomic(page_virt, KM_USER0);
 153                         flush_dcache_page(page);
 154                         if (rc) {
 155                                 printk(KERN_ERR "%s: Error reading xattr "
 156                                        "region; rc = [%d]\n", __FUNCTION__, rc);
 157                                 goto out;
 158                         }
 159                 } else {
 160                         /* This is an encrypted data extent */
 161                         loff_t lower_offset =
 162                                 ((view_extent_num * crypt_stat->extent_size)
 163                                  - crypt_stat->num_header_bytes_at_front);
 164
 165                         rc = ecryptfs_read_lower_page_segment(
 166                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
 167                                 (lower_offset & ~PAGE_CACHE_MASK),
 168                                 crypt_stat->extent_size, page->mapping->host);
 169                         if (rc) {
 170                                 printk(KERN_ERR "%s: Error attempting to read "
 171                                        "extent at offset [%lld] in the lower "
 172                                        "file; rc = [%d]\n", __FUNCTION__,
 173                                        lower_offset, rc);
 174                                 goto out;
 175                         }
 176                 }
 177                 extent_num_in_page++;
 178         }
 179 out:
 180         return rc;
 181 }
 182
 183 /**
 184  * ecryptfs_readpage
 185  * @file: An eCryptfs file
 186  * @page: Page from eCryptfs inode mapping into which to stick the read data
 187  *
 188  * Read in a page, decrypting if necessary.
 189  *
 190  * Returns zero on success; non-zero on error.
 191  */
 192 static int ecryptfs_readpage(struct file *file, struct page *page)
 193 {
 194         struct ecryptfs_crypt_stat *crypt_stat =
 195                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 196         int rc = 0;
 197
 198         if (!crypt_stat
 199             || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 200             || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
 201                 ecryptfs_printk(KERN_DEBUG,
 202                                 "Passing through unencrypted page\n");
 203                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 204                                                       PAGE_CACHE_SIZE,
 205                                                       page->mapping->host);
 206         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 207                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 208                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 209                                                                     crypt_stat);
 210                         if (rc) {
 211                                 printk(KERN_ERR "%s: Error attempting to copy "
 212                                        "the encrypted content from the lower "
 213                                        "file whilst inserting the metadata "
 214                                        "from the xattr into the header; rc = "
 215                                        "[%d]\n", __FUNCTION__, rc);
 216                                 goto out;
 217                         }
 218
 219                 } else {
 220                         rc = ecryptfs_read_lower_page_segment(
 221                                 page, page->index, 0, PAGE_CACHE_SIZE,
 222                                 page->mapping->host);
 223                         if (rc) {
 224                                 printk(KERN_ERR "Error reading page; rc = "
 225                                        "[%d]\n", rc);
 226                                 goto out;
 227                         }
 228                 }
 229         } else {
 230                 rc = ecryptfs_decrypt_page(page);
 231                 if (rc) {
 232                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 233                                         "rc = [%d]\n", rc);
 234                         goto out;
 235                 }
 236         }
 237 out:
 238         if (rc)
 239                 ClearPageUptodate(page);
 240         else
 241                 SetPageUptodate(page);
 242         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
 243                         page->index);
 244         unlock_page(page);
 245         return rc;
 246 }
 247
 248 /**
 249  * Called with lower inode mutex held.
 250  */
 251 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 252 {
 253         struct inode *inode = page->mapping->host;
 254         int end_byte_in_page;
 255
 256         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
 257                 goto out;
 258         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
 259         if (to > end_byte_in_page)
 260                 end_byte_in_page = to;
 261         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
 262 out:
 263         return 0;
 264 }
 265
 266 /* This function must zero any hole we create */
 267 static int ecryptfs_prepare_write(struct file *file, struct page *page,
 268                                   unsigned from, unsigned to)
 269 {
 270         int rc = 0;
 271         loff_t prev_page_end_size;
 272
 273         if (!PageUptodate(page)) {
 274                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 275                                                       PAGE_CACHE_SIZE,
 276                                                       page->mapping->host);
 277                 if (rc) {
 278                         printk(KERN_ERR "%s: Error attemping to read lower "
 279                                "page segment; rc = [%d]\n", __FUNCTION__, rc);
 280                         ClearPageUptodate(page);
 281                         goto out;
 282                 } else
 283                         SetPageUptodate(page);
 284         }
 285
 286         prev_page_end_size = ((loff_t)page->index << PAGE_CACHE_SHIFT);
 287
 288         /*
 289          * If creating a page or more of holes, zero them out via truncate.
 290          * Note, this will increase i_size.
 291          */
 292         if (page->index != 0) {
 293                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
 294                         rc = ecryptfs_truncate(file->f_path.dentry,
 295                                                prev_page_end_size);
 296                         if (rc) {
 297                                 printk(KERN_ERR "Error on attempt to "
 298                                        "truncate to (higher) offset [%lld];"
 299                                        " rc = [%d]\n", prev_page_end_size, rc);
 300                                 goto out;
 301                         }
 302                 }
 303         }
 304         /*
 305          * Writing to a new page, and creating a small hole from start of page?
 306          * Zero it out.
 307          */
 308         if ((i_size_read(page->mapping->host) == prev_page_end_size) &&
 309             (from != 0)) {
 310                 zero_user(page, 0, PAGE_CACHE_SIZE);
 311         }
 312 out:
 313         return rc;
 314 }
 315
 316 /**
 317  * ecryptfs_write_inode_size_to_header
 318  *
 319  * Writes the lower file size to the first 8 bytes of the header.
 320  *
 321  * Returns zero on success; non-zero on error.
 322  */
 323 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 324 {
 325         u64 file_size;
 326         char *file_size_virt;
 327         int rc;
 328
 329         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 330         if (!file_size_virt) {
 331                 rc = -ENOMEM;
 332                 goto out;
 333         }
 334         file_size = (u64)i_size_read(ecryptfs_inode);
 335         file_size = cpu_to_be64(file_size);
 336         memcpy(file_size_virt, &file_size, sizeof(u64));
 337         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 338                                   sizeof(u64));
 339         kfree(file_size_virt);
 340         if (rc)
 341                 printk(KERN_ERR "%s: Error writing file size to header; "
 342                        "rc = [%d]\n", __FUNCTION__, rc);
 343 out:
 344         return rc;
 345 }
 346
 347 struct kmem_cache *ecryptfs_xattr_cache;
 348
 349 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 350 {
 351         ssize_t size;
 352         void *xattr_virt;
 353         struct dentry *lower_dentry =
 354                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
 355         struct inode *lower_inode = lower_dentry->d_inode;
 356         u64 file_size;
 357         int rc;
 358
 359         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
 360                 printk(KERN_WARNING
 361                        "No support for setting xattr in lower filesystem\n");
 362                 rc = -ENOSYS;
 363                 goto out;
 364         }
 365         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 366         if (!xattr_virt) {
 367                 printk(KERN_ERR "Out of memory whilst attempting to write "
 368                        "inode size to xattr\n");
 369                 rc = -ENOMEM;
 370                 goto out;
 371         }
 372         mutex_lock(&lower_inode->i_mutex);
 373         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 374                                            xattr_virt, PAGE_CACHE_SIZE);
 375         if (size < 0)
 376                 size = 8;
 377         file_size = (u64)i_size_read(ecryptfs_inode);
 378         file_size = cpu_to_be64(file_size);
 379         memcpy(xattr_virt, &file_size, sizeof(u64));
 380         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 381                                          xattr_virt, size, 0);
 382         mutex_unlock(&lower_inode->i_mutex);
 383         if (rc)
 384                 printk(KERN_ERR "Error whilst attempting to write inode size "
 385                        "to lower file xattr; rc = [%d]\n", rc);
 386         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 387 out:
 388         return rc;
 389 }
 390
 391 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 392 {
 393         struct ecryptfs_crypt_stat *crypt_stat;
 394
 395         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 396         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 397                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 398         else
 399                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 400 }
 401
 402 /**
 403  * ecryptfs_commit_write
 404  * @file: The eCryptfs file object
 405  * @page: The eCryptfs page
 406  * @from: Ignored (we rotate the page IV on each write)
 407  * @to: Ignored
 408  *
 409  * This is where we encrypt the data and pass the encrypted data to
 410  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 411  * entire underlying packets.
 412  */
 413 static int ecryptfs_commit_write(struct file *file, struct page *page,
 414                                  unsigned from, unsigned to)
 415 {
 416         loff_t pos;
 417         struct inode *ecryptfs_inode = page->mapping->host;
 418         struct ecryptfs_crypt_stat *crypt_stat =
 419                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 420         int rc;
 421
 422         if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
 423                 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
 424                         "crypt_stat at memory location [%p]\n", crypt_stat);
 425                 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
 426         } else
 427                 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
 428         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 429                         "(page w/ index = [0x%.16x], to = [%d])\n", page->index,
 430                         to);
 431         /* Fills in zeros if 'to' goes beyond inode size */
 432         rc = fill_zeros_to_end_of_page(page, to);
 433         if (rc) {
 434                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 435                                 "zeros in page with index = [0x%.16x]\n",
 436                                 page->index);
 437                 goto out;
 438         }
 439         rc = ecryptfs_encrypt_page(page);
 440         if (rc) {
 441                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 442                                 "index [0x%.16x])\n", page->index);
 443                 goto out;
 444         }
 445         pos = (((loff_t)page->index) << PAGE_CACHE_SHIFT) + to;
 446         if (pos > i_size_read(ecryptfs_inode)) {
 447                 i_size_write(ecryptfs_inode, pos);
 448                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 449                                 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
 450         }
 451         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 452         if (rc)
 453                 printk(KERN_ERR "Error writing inode size to metadata; "
 454                        "rc = [%d]\n", rc);
 455 out:
 456         return rc;
 457 }
 458
 459 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 460 {
 461         int rc = 0;
 462         struct inode *inode;
 463         struct inode *lower_inode;
 464
 465         inode = (struct inode *)mapping->host;
 466         lower_inode = ecryptfs_inode_to_lower(inode);
 467         if (lower_inode->i_mapping->a_ops->bmap)
 468                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
 469                                                          block);
 470         return rc;
 471 }
 472
 473 struct address_space_operations ecryptfs_aops = {
 474         .writepage = ecryptfs_writepage,
 475         .readpage = ecryptfs_readpage,
 476         .prepare_write = ecryptfs_prepare_write,
 477         .commit_write = ecryptfs_commit_write,
 478         .bmap = ecryptfs_bmap,
 479 };