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         int save_num_header_extents_at_front =
 104                 crypt_stat->num_header_extents_at_front;
 105
 106         crypt_stat->num_header_extents_at_front = 1;
 107         ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written);
 108         crypt_stat->num_header_extents_at_front =
 109                 save_num_header_extents_at_front;
 110 }
 111
 112 /**
 113  * ecryptfs_copy_up_encrypted_with_header
 114  * @page: Sort of a ``virtual'' representation of the encrypted lower
 115  *        file. The actual lower file does not have the metadata in
 116  *        the header. This is locked.
 117  * @crypt_stat: The eCryptfs inode's cryptographic context
 118  *
 119  * The ``view'' is the version of the file that userspace winds up
 120  * seeing, with the header information inserted.
 121  */
 122 static int
 123 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 124                                        struct ecryptfs_crypt_stat *crypt_stat)
 125 {
 126         loff_t extent_num_in_page = 0;
 127         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
 128                                        / crypt_stat->extent_size);
 129         int rc = 0;
 130
 131         while (extent_num_in_page < num_extents_per_page) {
 132                 loff_t view_extent_num = ((((loff_t)page->index)
 133                                            * num_extents_per_page)
 134                                           + extent_num_in_page);
 135
 136                 if (view_extent_num < crypt_stat->num_header_extents_at_front) {
 137                         /* This is a header extent */
 138                         char *page_virt;
 139
 140                         page_virt = kmap_atomic(page, KM_USER0);
 141                         memset(page_virt, 0, PAGE_CACHE_SIZE);
 142                         /* TODO: Support more than one header extent */
 143                         if (view_extent_num == 0) {
 144                                 rc = ecryptfs_read_xattr_region(
 145                                         page_virt, page->mapping->host);
 146                                 set_header_info(page_virt, crypt_stat);
 147                         }
 148                         kunmap_atomic(page_virt, KM_USER0);
 149                         flush_dcache_page(page);
 150                         if (rc) {
 151                                 printk(KERN_ERR "%s: Error reading xattr "
 152                                        "region; rc = [%d]\n", __FUNCTION__, rc);
 153                                 goto out;
 154                         }
 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         if (rc)
 236                 ClearPageUptodate(page);
 237         else
 238                 SetPageUptodate(page);
 239         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
 240                         page->index);
 241         unlock_page(page);
 242         return rc;
 243 }
 244
 245 /**
 246  * Called with lower inode mutex held.
 247  */
 248 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 249 {
 250         struct inode *inode = page->mapping->host;
 251         int end_byte_in_page;
 252
 253         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
 254                 goto out;
 255         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
 256         if (to > end_byte_in_page)
 257                 end_byte_in_page = to;
 258         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
 259 out:
 260         return 0;
 261 }
 262
 263 /* This function must zero any hole we create */
 264 static int ecryptfs_prepare_write(struct file *file, struct page *page,
 265                                   unsigned from, unsigned to)
 266 {
 267         int rc = 0;
 268         loff_t prev_page_end_size;
 269
 270         if (!PageUptodate(page)) {
 271                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 272                                                       PAGE_CACHE_SIZE,
 273                                                       page->mapping->host);
 274                 if (rc) {
 275                         printk(KERN_ERR "%s: Error attemping to read lower "
 276                                "page segment; rc = [%d]\n", __FUNCTION__, rc);
 277                         ClearPageUptodate(page);
 278                         goto out;
 279                 } else
 280                         SetPageUptodate(page);
 281         }
 282
 283         prev_page_end_size = ((loff_t)page->index << PAGE_CACHE_SHIFT);
 284
 285         /*
 286          * If creating a page or more of holes, zero them out via truncate.
 287          * Note, this will increase i_size.
 288          */
 289         if (page->index != 0) {
 290                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
 291                         rc = ecryptfs_truncate(file->f_path.dentry,
 292                                                prev_page_end_size);
 293                         if (rc) {
 294                                 printk(KERN_ERR "Error on attempt to "
 295                                        "truncate to (higher) offset [%lld];"
 296                                        " rc = [%d]\n", prev_page_end_size, rc);
 297                                 goto out;
 298                         }
 299                 }
 300         }
 301         /*
 302          * Writing to a new page, and creating a small hole from start of page?
 303          * Zero it out.
 304          */
 305         if ((i_size_read(page->mapping->host) == prev_page_end_size) &&
 306             (from != 0)) {
 307                 zero_user(page, 0, PAGE_CACHE_SIZE);
 308         }
 309 out:
 310         return rc;
 311 }
 312
 313 /**
 314  * ecryptfs_write_inode_size_to_header
 315  *
 316  * Writes the lower file size to the first 8 bytes of the header.
 317  *
 318  * Returns zero on success; non-zero on error.
 319  */
 320 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 321 {
 322         u64 file_size;
 323         char *file_size_virt;
 324         int rc;
 325
 326         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 327         if (!file_size_virt) {
 328                 rc = -ENOMEM;
 329                 goto out;
 330         }
 331         file_size = (u64)i_size_read(ecryptfs_inode);
 332         file_size = cpu_to_be64(file_size);
 333         memcpy(file_size_virt, &file_size, sizeof(u64));
 334         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 335                                   sizeof(u64));
 336         kfree(file_size_virt);
 337         if (rc)
 338                 printk(KERN_ERR "%s: Error writing file size to header; "
 339                        "rc = [%d]\n", __FUNCTION__, rc);
 340 out:
 341         return rc;
 342 }
 343
 344 struct kmem_cache *ecryptfs_xattr_cache;
 345
 346 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 347 {
 348         ssize_t size;
 349         void *xattr_virt;
 350         struct dentry *lower_dentry =
 351                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
 352         struct inode *lower_inode = lower_dentry->d_inode;
 353         u64 file_size;
 354         int rc;
 355
 356         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
 357                 printk(KERN_WARNING
 358                        "No support for setting xattr in lower filesystem\n");
 359                 rc = -ENOSYS;
 360                 goto out;
 361         }
 362         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 363         if (!xattr_virt) {
 364                 printk(KERN_ERR "Out of memory whilst attempting to write "
 365                        "inode size to xattr\n");
 366                 rc = -ENOMEM;
 367                 goto out;
 368         }
 369         mutex_lock(&lower_inode->i_mutex);
 370         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 371                                            xattr_virt, PAGE_CACHE_SIZE);
 372         if (size < 0)
 373                 size = 8;
 374         file_size = (u64)i_size_read(ecryptfs_inode);
 375         file_size = cpu_to_be64(file_size);
 376         memcpy(xattr_virt, &file_size, sizeof(u64));
 377         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 378                                          xattr_virt, size, 0);
 379         mutex_unlock(&lower_inode->i_mutex);
 380         if (rc)
 381                 printk(KERN_ERR "Error whilst attempting to write inode size "
 382                        "to lower file xattr; rc = [%d]\n", rc);
 383         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 384 out:
 385         return rc;
 386 }
 387
 388 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 389 {
 390         struct ecryptfs_crypt_stat *crypt_stat;
 391
 392         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 393         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 394                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 395         else
 396                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 397 }
 398
 399 /**
 400  * ecryptfs_commit_write
 401  * @file: The eCryptfs file object
 402  * @page: The eCryptfs page
 403  * @from: Ignored (we rotate the page IV on each write)
 404  * @to: Ignored
 405  *
 406  * This is where we encrypt the data and pass the encrypted data to
 407  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 408  * entire underlying packets.
 409  */
 410 static int ecryptfs_commit_write(struct file *file, struct page *page,
 411                                  unsigned from, unsigned to)
 412 {
 413         loff_t pos;
 414         struct inode *ecryptfs_inode = page->mapping->host;
 415         struct ecryptfs_crypt_stat *crypt_stat =
 416                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 417         int rc;
 418
 419         if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
 420                 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
 421                         "crypt_stat at memory location [%p]\n", crypt_stat);
 422                 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
 423         } else
 424                 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
 425         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 426                         "(page w/ index = [0x%.16x], to = [%d])\n", page->index,
 427                         to);
 428         /* Fills in zeros if 'to' goes beyond inode size */
 429         rc = fill_zeros_to_end_of_page(page, to);
 430         if (rc) {
 431                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 432                                 "zeros in page with index = [0x%.16x]\n",
 433                                 page->index);
 434                 goto out;
 435         }
 436         rc = ecryptfs_encrypt_page(page);
 437         if (rc) {
 438                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 439                                 "index [0x%.16x])\n", page->index);
 440                 goto out;
 441         }
 442         pos = (((loff_t)page->index) << PAGE_CACHE_SHIFT) + to;
 443         if (pos > i_size_read(ecryptfs_inode)) {
 444                 i_size_write(ecryptfs_inode, pos);
 445                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 446                                 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
 447         }
 448         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 449         if (rc)
 450                 printk(KERN_ERR "Error writing inode size to metadata; "
 451                        "rc = [%d]\n", rc);
 452 out:
 453         return rc;
 454 }
 455
 456 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 457 {
 458         int rc = 0;
 459         struct inode *inode;
 460         struct inode *lower_inode;
 461
 462         inode = (struct inode *)mapping->host;
 463         lower_inode = ecryptfs_inode_to_lower(inode);
 464         if (lower_inode->i_mapping->a_ops->bmap)
 465                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
 466                                                          block);
 467         return rc;
 468 }
 469
 470 struct address_space_operations ecryptfs_aops = {
 471         .writepage = ecryptfs_writepage,
 472         .readpage = ecryptfs_readpage,
 473         .prepare_write = ecryptfs_prepare_write,
 474         .commit_write = ecryptfs_commit_write,
 475         .bmap = ecryptfs_bmap,
 476 };