SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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 struct kmem_cache *ecryptfs_lower_page_cache;
  38
  39 /**
  40  * ecryptfs_get1page
  41  *
  42  * Get one page from cache or lower f/s, return error otherwise.
  43  *
  44  * Returns unlocked and up-to-date page (if ok), with increased
  45  * refcnt.
  46  */
  47 struct page *ecryptfs_get1page(struct file *file, loff_t index)
  48 {
  49         struct dentry *dentry;
  50         struct inode *inode;
  51         struct address_space *mapping;
  52
  53         dentry = file->f_path.dentry;
  54         inode = dentry->d_inode;
  55         mapping = inode->i_mapping;
  56         return read_mapping_page(mapping, index, (void *)file);
  57 }
  58
  59 /**
  60  * ecryptfs_writepage
  61  * @page: Page that is locked before this call is made
  62  *
  63  * Returns zero on success; non-zero otherwise
  64  */
  65 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
  66 {
  67         int rc;
  68
  69         rc = ecryptfs_encrypt_page(page);
  70         if (rc) {
  71                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
  72                                 "page (upper index [0x%.16x])\n", page->index);
  73                 ClearPageUptodate(page);
  74                 goto out;
  75         }
  76         SetPageUptodate(page);
  77         unlock_page(page);
  78 out:
  79         return rc;
  80 }
  81
  82 /**
  83  *   Header Extent:
  84  *     Octets 0-7:        Unencrypted file size (big-endian)
  85  *     Octets 8-15:       eCryptfs special marker
  86  *     Octets 16-19:      Flags
  87  *      Octet 16:         File format version number (between 0 and 255)
  88  *      Octets 17-18:     Reserved
  89  *      Octet 19:         Bit 1 (lsb): Reserved
  90  *                        Bit 2: Encrypted?
  91  *                        Bits 3-8: Reserved
  92  *     Octets 20-23:      Header extent size (big-endian)
  93  *     Octets 24-25:      Number of header extents at front of file
  94  *                        (big-endian)
  95  *     Octet  26:         Begin RFC 2440 authentication token packet set
  96  */
  97 static void set_header_info(char *page_virt,
  98                             struct ecryptfs_crypt_stat *crypt_stat)
  99 {
 100         size_t written;
 101         int save_num_header_extents_at_front =
 102                 crypt_stat->num_header_extents_at_front;
 103
 104         crypt_stat->num_header_extents_at_front = 1;
 105         ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written);
 106         crypt_stat->num_header_extents_at_front =
 107                 save_num_header_extents_at_front;
 108 }
 109
 110 /**
 111  * ecryptfs_copy_up_encrypted_with_header
 112  * @page: Sort of a ``virtual'' representation of the encrypted lower
 113  *        file. The actual lower file does not have the metadata in
 114  *        the header. This is locked.
 115  * @crypt_stat: The eCryptfs inode's cryptographic context
 116  *
 117  * The ``view'' is the version of the file that userspace winds up
 118  * seeing, with the header information inserted.
 119  */
 120 static int
 121 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 122                                        struct ecryptfs_crypt_stat *crypt_stat)
 123 {
 124         loff_t extent_num_in_page = 0;
 125         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
 126                                        / crypt_stat->extent_size);
 127         int rc = 0;
 128
 129         while (extent_num_in_page < num_extents_per_page) {
 130                 loff_t view_extent_num = ((((loff_t)page->index)
 131                                            * num_extents_per_page)
 132                                           + extent_num_in_page);
 133
 134                 if (view_extent_num < crypt_stat->num_header_extents_at_front) {
 135                         /* This is a header extent */
 136                         char *page_virt;
 137
 138                         page_virt = kmap_atomic(page, KM_USER0);
 139                         memset(page_virt, 0, PAGE_CACHE_SIZE);
 140                         /* TODO: Support more than one header extent */
 141                         if (view_extent_num == 0) {
 142                                 rc = ecryptfs_read_xattr_region(
 143                                         page_virt, page->mapping->host);
 144                                 set_header_info(page_virt, crypt_stat);
 145                         }
 146                         kunmap_atomic(page_virt, KM_USER0);
 147                         flush_dcache_page(page);
 148                         if (rc) {
 149                                 ClearPageUptodate(page);
 150                                 printk(KERN_ERR "%s: Error reading xattr "
 151                                        "region; rc = [%d]\n", __FUNCTION__, rc);
 152                                 goto out;
 153                         }
 154                         SetPageUptodate(page);
 155                 } else {
 156                         /* This is an encrypted data extent */
 157                         loff_t lower_offset =
 158                                 ((view_extent_num -
 159                                   crypt_stat->num_header_extents_at_front)
 160                                  * crypt_stat->extent_size);
 161
 162                         rc = ecryptfs_read_lower_page_segment(
 163                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
 164                                 (lower_offset & ~PAGE_CACHE_MASK),
 165                                 crypt_stat->extent_size, page->mapping->host);
 166                         if (rc) {
 167                                 printk(KERN_ERR "%s: Error attempting to read "
 168                                        "extent at offset [%lld] in the lower "
 169                                        "file; rc = [%d]\n", __FUNCTION__,
 170                                        lower_offset, rc);
 171                                 goto out;
 172                         }
 173                 }
 174                 extent_num_in_page++;
 175         }
 176 out:
 177         return rc;
 178 }
 179
 180 /**
 181  * ecryptfs_readpage
 182  * @file: An eCryptfs file
 183  * @page: Page from eCryptfs inode mapping into which to stick the read data
 184  *
 185  * Read in a page, decrypting if necessary.
 186  *
 187  * Returns zero on success; non-zero on error.
 188  */
 189 static int ecryptfs_readpage(struct file *file, struct page *page)
 190 {
 191         struct ecryptfs_crypt_stat *crypt_stat =
 192                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 193         int rc = 0;
 194
 195         if (!crypt_stat
 196             || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 197             || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
 198                 ecryptfs_printk(KERN_DEBUG,
 199                                 "Passing through unencrypted page\n");
 200                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 201                                                       PAGE_CACHE_SIZE,
 202                                                       page->mapping->host);
 203         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 204                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 205                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 206                                                                     crypt_stat);
 207                         if (rc) {
 208                                 printk(KERN_ERR "%s: Error attempting to copy "
 209                                        "the encrypted content from the lower "
 210                                        "file whilst inserting the metadata "
 211                                        "from the xattr into the header; rc = "
 212                                        "[%d]\n", __FUNCTION__, rc);
 213                                 goto out;
 214                         }
 215
 216                 } else {
 217                         rc = ecryptfs_read_lower_page_segment(
 218                                 page, page->index, 0, PAGE_CACHE_SIZE,
 219                                 page->mapping->host);
 220                         if (rc) {
 221                                 printk(KERN_ERR "Error reading page; rc = "
 222                                        "[%d]\n", rc);
 223                                 goto out;
 224                         }
 225                 }
 226         } else {
 227                 rc = ecryptfs_decrypt_page(page);
 228                 if (rc) {
 229                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 230                                         "rc = [%d]\n", rc);
 231                         goto out;
 232                 }
 233         }
 234 out:
 235         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
 236                         page->index);
 237         unlock_page(page);
 238         return rc;
 239 }
 240
 241 /**
 242  * Called with lower inode mutex held.
 243  */
 244 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 245 {
 246         struct inode *inode = page->mapping->host;
 247         int end_byte_in_page;
 248
 249         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
 250                 goto out;
 251         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
 252         if (to > end_byte_in_page)
 253                 end_byte_in_page = to;
 254         zero_user_page(page, end_byte_in_page,
 255                 PAGE_CACHE_SIZE - end_byte_in_page, KM_USER0);
 256 out:
 257         return 0;
 258 }
 259
 260 static int ecryptfs_prepare_write(struct file *file, struct page *page,
 261                                   unsigned from, unsigned to)
 262 {
 263         int rc = 0;
 264
 265         if (from == 0 && to == PAGE_CACHE_SIZE)
 266                 goto out;       /* If we are writing a full page, it will be
 267                                    up to date. */
 268         if (!PageUptodate(page))
 269                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 270                                                       PAGE_CACHE_SIZE,
 271                                                       page->mapping->host);
 272         if (page->index != 0) {
 273                 loff_t end_of_prev_pg_pos =
 274                         (((loff_t)page->index << PAGE_CACHE_SHIFT) - 1);
 275
 276                 if (end_of_prev_pg_pos > i_size_read(page->mapping->host)) {
 277                         rc = ecryptfs_truncate(file->f_path.dentry,
 278                                                end_of_prev_pg_pos);
 279                         if (rc) {
 280                                 printk(KERN_ERR "Error on attempt to "
 281                                        "truncate to (higher) offset [%lld];"
 282                                        " rc = [%d]\n", end_of_prev_pg_pos, rc);
 283                                 goto out;
 284                         }
 285                 }
 286                 if (end_of_prev_pg_pos + 1 > i_size_read(page->mapping->host))
 287                         zero_user_page(page, 0, PAGE_CACHE_SIZE, KM_USER0);
 288         }
 289 out:
 290         return rc;
 291 }
 292
 293 /**
 294  * ecryptfs_write_inode_size_to_header
 295  *
 296  * Writes the lower file size to the first 8 bytes of the header.
 297  *
 298  * Returns zero on success; non-zero on error.
 299  */
 300 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 301 {
 302         u64 file_size;
 303         char *file_size_virt;
 304         int rc;
 305
 306         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 307         if (!file_size_virt) {
 308                 rc = -ENOMEM;
 309                 goto out;
 310         }
 311         file_size = (u64)i_size_read(ecryptfs_inode);
 312         file_size = cpu_to_be64(file_size);
 313         memcpy(file_size_virt, &file_size, sizeof(u64));
 314         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 315                                   sizeof(u64));
 316         kfree(file_size_virt);
 317         if (rc)
 318                 printk(KERN_ERR "%s: Error writing file size to header; "
 319                        "rc = [%d]\n", __FUNCTION__, rc);
 320 out:
 321         return rc;
 322 }
 323
 324 struct kmem_cache *ecryptfs_xattr_cache;
 325
 326 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 327 {
 328         ssize_t size;
 329         void *xattr_virt;
 330         struct dentry *lower_dentry =
 331                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
 332         struct inode *lower_inode = lower_dentry->d_inode;
 333         u64 file_size;
 334         int rc;
 335
 336         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
 337                 printk(KERN_WARNING
 338                        "No support for setting xattr in lower filesystem\n");
 339                 rc = -ENOSYS;
 340                 goto out;
 341         }
 342         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 343         if (!xattr_virt) {
 344                 printk(KERN_ERR "Out of memory whilst attempting to write "
 345                        "inode size to xattr\n");
 346                 rc = -ENOMEM;
 347                 goto out;
 348         }
 349         mutex_lock(&lower_inode->i_mutex);
 350         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 351                                            xattr_virt, PAGE_CACHE_SIZE);
 352         if (size < 0)
 353                 size = 8;
 354         file_size = (u64)i_size_read(ecryptfs_inode);
 355         file_size = cpu_to_be64(file_size);
 356         memcpy(xattr_virt, &file_size, sizeof(u64));
 357         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 358                                          xattr_virt, size, 0);
 359         mutex_unlock(&lower_inode->i_mutex);
 360         if (rc)
 361                 printk(KERN_ERR "Error whilst attempting to write inode size "
 362                        "to lower file xattr; rc = [%d]\n", rc);
 363         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 364 out:
 365         return rc;
 366 }
 367
 368 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 369 {
 370         struct ecryptfs_crypt_stat *crypt_stat;
 371
 372         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 373         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 374                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 375         else
 376                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 377 }
 378
 379 /**
 380  * ecryptfs_commit_write
 381  * @file: The eCryptfs file object
 382  * @page: The eCryptfs page
 383  * @from: Ignored (we rotate the page IV on each write)
 384  * @to: Ignored
 385  *
 386  * This is where we encrypt the data and pass the encrypted data to
 387  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 388  * entire underlying packets.
 389  */
 390 static int ecryptfs_commit_write(struct file *file, struct page *page,
 391                                  unsigned from, unsigned to)
 392 {
 393         loff_t pos;
 394         struct inode *ecryptfs_inode = page->mapping->host;
 395         struct ecryptfs_crypt_stat *crypt_stat =
 396                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 397         int rc;
 398
 399         if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
 400                 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
 401                         "crypt_stat at memory location [%p]\n", crypt_stat);
 402                 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
 403         } else
 404                 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
 405         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 406                         "(page w/ index = [0x%.16x], to = [%d])\n", page->index,
 407                         to);
 408         /* Fills in zeros if 'to' goes beyond inode size */
 409         rc = fill_zeros_to_end_of_page(page, to);
 410         if (rc) {
 411                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 412                                 "zeros in page with index = [0x%.16x]\n",
 413                                 page->index);
 414                 goto out;
 415         }
 416         rc = ecryptfs_encrypt_page(page);
 417         if (rc) {
 418                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 419                                 "index [0x%.16x])\n", page->index);
 420                 goto out;
 421         }
 422         pos = (((loff_t)page->index) << PAGE_CACHE_SHIFT) + to;
 423         if (pos > i_size_read(ecryptfs_inode)) {
 424                 i_size_write(ecryptfs_inode, pos);
 425                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 426                                 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
 427         }
 428         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 429         if (rc)
 430                 printk(KERN_ERR "Error writing inode size to metadata; "
 431                        "rc = [%d]\n", rc);
 432 out:
 433         return rc;
 434 }
 435
 436 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 437 {
 438         int rc = 0;
 439         struct inode *inode;
 440         struct inode *lower_inode;
 441
 442         inode = (struct inode *)mapping->host;
 443         lower_inode = ecryptfs_inode_to_lower(inode);
 444         if (lower_inode->i_mapping->a_ops->bmap)
 445                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
 446                                                          block);
 447         return rc;
 448 }
 449
 450 struct address_space_operations ecryptfs_aops = {
 451         .writepage = ecryptfs_writepage,
 452         .readpage = ecryptfs_readpage,
 453         .prepare_write = ecryptfs_prepare_write,
 454         .commit_write = ecryptfs_commit_write,
 455         .bmap = ecryptfs_bmap,
 456 };