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 <linux/slab.h> 36 #include <asm/unaligned.h> 37 #include "ecryptfs_kernel.h" 38 39 /** 40 * ecryptfs_get_locked_page 41 * 42 * Get one page from cache or lower f/s, return error otherwise. 43 * 44 * Returns locked and up-to-date page (if ok), with increased 45 * refcnt. 46 */ 47 struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index) 48 { 49 struct page *page = read_mapping_page(inode->i_mapping, index, NULL); 50 if (!IS_ERR(page)) 51 lock_page(page); 52 return page; 53 } 54 55 /** 56 * ecryptfs_writepage 57 * @page: Page that is locked before this call is made 58 * 59 * Returns zero on success; non-zero otherwise 60 * 61 * This is where we encrypt the data and pass the encrypted data to 62 * the lower filesystem. In OpenPGP-compatible mode, we operate on 63 * entire underlying packets. 64 */ 65 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc) 66 { 67 int rc; 68 69 /* 70 * Refuse to write the page out if we are called from reclaim context 71 * since our writepage() path may potentially allocate memory when 72 * calling into the lower fs vfs_write() which may in turn invoke 73 * us again. 74 */ 75 if (current->flags & PF_MEMALLOC) { 76 redirty_page_for_writepage(wbc, page); 77 rc = 0; 78 goto out; 79 } 80 81 rc = ecryptfs_encrypt_page(page); 82 if (rc) { 83 ecryptfs_printk(KERN_WARNING, "Error encrypting " 84 "page (upper index [0x%.16lx])\n", page->index); 85 ClearPageUptodate(page); 86 goto out; 87 } 88 SetPageUptodate(page); 89 out: 90 unlock_page(page); 91 return rc; 92 } 93 94 static void strip_xattr_flag(char *page_virt, 95 struct ecryptfs_crypt_stat *crypt_stat) 96 { 97 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 98 size_t written; 99 100 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR; 101 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat, 102 &written); 103 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR; 104 } 105 } 106 107 /** 108 * Header Extent: 109 * Octets 0-7: Unencrypted file size (big-endian) 110 * Octets 8-15: eCryptfs special marker 111 * Octets 16-19: Flags 112 * Octet 16: File format version number (between 0 and 255) 113 * Octets 17-18: Reserved 114 * Octet 19: Bit 1 (lsb): Reserved 115 * Bit 2: Encrypted? 116 * Bits 3-8: Reserved 117 * Octets 20-23: Header extent size (big-endian) 118 * Octets 24-25: Number of header extents at front of file 119 * (big-endian) 120 * Octet 26: Begin RFC 2440 authentication token packet set 121 */ 122 123 /** 124 * ecryptfs_copy_up_encrypted_with_header 125 * @page: Sort of a ``virtual'' representation of the encrypted lower 126 * file. The actual lower file does not have the metadata in 127 * the header. This is locked. 128 * @crypt_stat: The eCryptfs inode's cryptographic context 129 * 130 * The ``view'' is the version of the file that userspace winds up 131 * seeing, with the header information inserted. 132 */ 133 static int 134 ecryptfs_copy_up_encrypted_with_header(struct page *page, 135 struct ecryptfs_crypt_stat *crypt_stat) 136 { 137 loff_t extent_num_in_page = 0; 138 loff_t num_extents_per_page = (PAGE_CACHE_SIZE 139 / crypt_stat->extent_size); 140 int rc = 0; 141 142 while (extent_num_in_page < num_extents_per_page) { 143 loff_t view_extent_num = ((((loff_t)page->index) 144 * num_extents_per_page) 145 + extent_num_in_page); 146 size_t num_header_extents_at_front = 147 (crypt_stat->metadata_size / crypt_stat->extent_size); 148 149 if (view_extent_num < num_header_extents_at_front) { 150 /* This is a header extent */ 151 char *page_virt; 152 153 page_virt = kmap_atomic(page); 154 memset(page_virt, 0, PAGE_CACHE_SIZE); 155 /* TODO: Support more than one header extent */ 156 if (view_extent_num == 0) { 157 size_t written; 158 159 rc = ecryptfs_read_xattr_region( 160 page_virt, page->mapping->host); 161 strip_xattr_flag(page_virt + 16, crypt_stat); 162 ecryptfs_write_header_metadata(page_virt + 20, 163 crypt_stat, 164 &written); 165 } 166 kunmap_atomic(page_virt); 167 flush_dcache_page(page); 168 if (rc) { 169 printk(KERN_ERR "%s: Error reading xattr " 170 "region; rc = [%d]\n", __func__, rc); 171 goto out; 172 } 173 } else { 174 /* This is an encrypted data extent */ 175 loff_t lower_offset = 176 ((view_extent_num * crypt_stat->extent_size) 177 - crypt_stat->metadata_size); 178 179 rc = ecryptfs_read_lower_page_segment( 180 page, (lower_offset >> PAGE_CACHE_SHIFT), 181 (lower_offset & ~PAGE_CACHE_MASK), 182 crypt_stat->extent_size, page->mapping->host); 183 if (rc) { 184 printk(KERN_ERR "%s: Error attempting to read " 185 "extent at offset [%lld] in the lower " 186 "file; rc = [%d]\n", __func__, 187 lower_offset, rc); 188 goto out; 189 } 190 } 191 extent_num_in_page++; 192 } 193 out: 194 return rc; 195 } 196 197 /** 198 * ecryptfs_readpage 199 * @file: An eCryptfs file 200 * @page: Page from eCryptfs inode mapping into which to stick the read data 201 * 202 * Read in a page, decrypting if necessary. 203 * 204 * Returns zero on success; non-zero on error. 205 */ 206 static int ecryptfs_readpage(struct file *file, struct page *page) 207 { 208 struct ecryptfs_crypt_stat *crypt_stat = 209 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat; 210 int rc = 0; 211 212 if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 213 rc = ecryptfs_read_lower_page_segment(page, page->index, 0, 214 PAGE_CACHE_SIZE, 215 page->mapping->host); 216 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 217 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 218 rc = ecryptfs_copy_up_encrypted_with_header(page, 219 crypt_stat); 220 if (rc) { 221 printk(KERN_ERR "%s: Error attempting to copy " 222 "the encrypted content from the lower " 223 "file whilst inserting the metadata " 224 "from the xattr into the header; rc = " 225 "[%d]\n", __func__, rc); 226 goto out; 227 } 228 229 } else { 230 rc = ecryptfs_read_lower_page_segment( 231 page, page->index, 0, PAGE_CACHE_SIZE, 232 page->mapping->host); 233 if (rc) { 234 printk(KERN_ERR "Error reading page; rc = " 235 "[%d]\n", rc); 236 goto out; 237 } 238 } 239 } else { 240 rc = ecryptfs_decrypt_page(page); 241 if (rc) { 242 ecryptfs_printk(KERN_ERR, "Error decrypting page; " 243 "rc = [%d]\n", rc); 244 goto out; 245 } 246 } 247 out: 248 if (rc) 249 ClearPageUptodate(page); 250 else 251 SetPageUptodate(page); 252 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n", 253 page->index); 254 unlock_page(page); 255 return rc; 256 } 257 258 /** 259 * Called with lower inode mutex held. 260 */ 261 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to) 262 { 263 struct inode *inode = page->mapping->host; 264 int end_byte_in_page; 265 266 if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index) 267 goto out; 268 end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE; 269 if (to > end_byte_in_page) 270 end_byte_in_page = to; 271 zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE); 272 out: 273 return 0; 274 } 275 276 /** 277 * ecryptfs_write_begin 278 * @file: The eCryptfs file 279 * @mapping: The eCryptfs object 280 * @pos: The file offset at which to start writing 281 * @len: Length of the write 282 * @flags: Various flags 283 * @pagep: Pointer to return the page 284 * @fsdata: Pointer to return fs data (unused) 285 * 286 * This function must zero any hole we create 287 * 288 * Returns zero on success; non-zero otherwise 289 */ 290 static int ecryptfs_write_begin(struct file *file, 291 struct address_space *mapping, 292 loff_t pos, unsigned len, unsigned flags, 293 struct page **pagep, void **fsdata) 294 { 295 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 296 struct page *page; 297 loff_t prev_page_end_size; 298 int rc = 0; 299 300 page = grab_cache_page_write_begin(mapping, index, flags); 301 if (!page) 302 return -ENOMEM; 303 *pagep = page; 304 305 prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT); 306 if (!PageUptodate(page)) { 307 struct ecryptfs_crypt_stat *crypt_stat = 308 &ecryptfs_inode_to_private(mapping->host)->crypt_stat; 309 310 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 311 rc = ecryptfs_read_lower_page_segment( 312 page, index, 0, PAGE_CACHE_SIZE, mapping->host); 313 if (rc) { 314 printk(KERN_ERR "%s: Error attemping to read " 315 "lower page segment; rc = [%d]\n", 316 __func__, rc); 317 ClearPageUptodate(page); 318 goto out; 319 } else 320 SetPageUptodate(page); 321 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 322 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 323 rc = ecryptfs_copy_up_encrypted_with_header( 324 page, crypt_stat); 325 if (rc) { 326 printk(KERN_ERR "%s: Error attempting " 327 "to copy the encrypted content " 328 "from the lower file whilst " 329 "inserting the metadata from " 330 "the xattr into the header; rc " 331 "= [%d]\n", __func__, rc); 332 ClearPageUptodate(page); 333 goto out; 334 } 335 SetPageUptodate(page); 336 } else { 337 rc = ecryptfs_read_lower_page_segment( 338 page, index, 0, PAGE_CACHE_SIZE, 339 mapping->host); 340 if (rc) { 341 printk(KERN_ERR "%s: Error reading " 342 "page; rc = [%d]\n", 343 __func__, rc); 344 ClearPageUptodate(page); 345 goto out; 346 } 347 SetPageUptodate(page); 348 } 349 } else { 350 if (prev_page_end_size 351 >= i_size_read(page->mapping->host)) { 352 zero_user(page, 0, PAGE_CACHE_SIZE); 353 } else { 354 rc = ecryptfs_decrypt_page(page); 355 if (rc) { 356 printk(KERN_ERR "%s: Error decrypting " 357 "page at index [%ld]; " 358 "rc = [%d]\n", 359 __func__, page->index, rc); 360 ClearPageUptodate(page); 361 goto out; 362 } 363 } 364 SetPageUptodate(page); 365 } 366 } 367 /* If creating a page or more of holes, zero them out via truncate. 368 * Note, this will increase i_size. */ 369 if (index != 0) { 370 if (prev_page_end_size > i_size_read(page->mapping->host)) { 371 rc = ecryptfs_truncate(file->f_path.dentry, 372 prev_page_end_size); 373 if (rc) { 374 printk(KERN_ERR "%s: Error on attempt to " 375 "truncate to (higher) offset [%lld];" 376 " rc = [%d]\n", __func__, 377 prev_page_end_size, rc); 378 goto out; 379 } 380 } 381 } 382 /* Writing to a new page, and creating a small hole from start 383 * of page? Zero it out. */ 384 if ((i_size_read(mapping->host) == prev_page_end_size) 385 && (pos != 0)) 386 zero_user(page, 0, PAGE_CACHE_SIZE); 387 out: 388 if (unlikely(rc)) { 389 unlock_page(page); 390 page_cache_release(page); 391 *pagep = NULL; 392 } 393 return rc; 394 } 395 396 /** 397 * ecryptfs_write_inode_size_to_header 398 * 399 * Writes the lower file size to the first 8 bytes of the header. 400 * 401 * Returns zero on success; non-zero on error. 402 */ 403 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) 404 { 405 char *file_size_virt; 406 int rc; 407 408 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); 409 if (!file_size_virt) { 410 rc = -ENOMEM; 411 goto out; 412 } 413 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); 414 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, 415 sizeof(u64)); 416 kfree(file_size_virt); 417 if (rc < 0) 418 printk(KERN_ERR "%s: Error writing file size to header; " 419 "rc = [%d]\n", __func__, rc); 420 else 421 rc = 0; 422 out: 423 return rc; 424 } 425 426 struct kmem_cache *ecryptfs_xattr_cache; 427 428 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) 429 { 430 ssize_t size; 431 void *xattr_virt; 432 struct dentry *lower_dentry = 433 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry; 434 struct inode *lower_inode = lower_dentry->d_inode; 435 int rc; 436 437 if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) { 438 printk(KERN_WARNING 439 "No support for setting xattr in lower filesystem\n"); 440 rc = -ENOSYS; 441 goto out; 442 } 443 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); 444 if (!xattr_virt) { 445 printk(KERN_ERR "Out of memory whilst attempting to write " 446 "inode size to xattr\n"); 447 rc = -ENOMEM; 448 goto out; 449 } 450 mutex_lock(&lower_inode->i_mutex); 451 size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 452 xattr_virt, PAGE_CACHE_SIZE); 453 if (size < 0) 454 size = 8; 455 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt); 456 rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 457 xattr_virt, size, 0); 458 mutex_unlock(&lower_inode->i_mutex); 459 if (rc) 460 printk(KERN_ERR "Error whilst attempting to write inode size " 461 "to lower file xattr; rc = [%d]\n", rc); 462 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); 463 out: 464 return rc; 465 } 466 467 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) 468 { 469 struct ecryptfs_crypt_stat *crypt_stat; 470 471 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 472 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); 473 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) 474 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); 475 else 476 return ecryptfs_write_inode_size_to_header(ecryptfs_inode); 477 } 478 479 /** 480 * ecryptfs_write_end 481 * @file: The eCryptfs file object 482 * @mapping: The eCryptfs object 483 * @pos: The file position 484 * @len: The length of the data (unused) 485 * @copied: The amount of data copied 486 * @page: The eCryptfs page 487 * @fsdata: The fsdata (unused) 488 */ 489 static int ecryptfs_write_end(struct file *file, 490 struct address_space *mapping, 491 loff_t pos, unsigned len, unsigned copied, 492 struct page *page, void *fsdata) 493 { 494 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 495 unsigned from = pos & (PAGE_CACHE_SIZE - 1); 496 unsigned to = from + copied; 497 struct inode *ecryptfs_inode = mapping->host; 498 struct ecryptfs_crypt_stat *crypt_stat = 499 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 500 int rc; 501 int need_unlock_page = 1; 502 503 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" 504 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to); 505 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 506 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, 507 to); 508 if (!rc) { 509 rc = copied; 510 fsstack_copy_inode_size(ecryptfs_inode, 511 ecryptfs_inode_to_lower(ecryptfs_inode)); 512 } 513 goto out; 514 } 515 /* Fills in zeros if 'to' goes beyond inode size */ 516 rc = fill_zeros_to_end_of_page(page, to); 517 if (rc) { 518 ecryptfs_printk(KERN_WARNING, "Error attempting to fill " 519 "zeros in page with index = [0x%.16lx]\n", index); 520 goto out; 521 } 522 set_page_dirty(page); 523 unlock_page(page); 524 need_unlock_page = 0; 525 if (pos + copied > i_size_read(ecryptfs_inode)) { 526 i_size_write(ecryptfs_inode, pos + copied); 527 ecryptfs_printk(KERN_DEBUG, "Expanded file size to " 528 "[0x%.16llx]\n", 529 (unsigned long long)i_size_read(ecryptfs_inode)); 530 balance_dirty_pages_ratelimited(mapping); 531 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode); 532 if (rc) { 533 printk(KERN_ERR "Error writing inode size to metadata; " 534 "rc = [%d]\n", rc); 535 goto out; 536 } 537 } 538 rc = copied; 539 out: 540 if (need_unlock_page) 541 unlock_page(page); 542 page_cache_release(page); 543 return rc; 544 } 545 546 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block) 547 { 548 int rc = 0; 549 struct inode *inode; 550 struct inode *lower_inode; 551 552 inode = (struct inode *)mapping->host; 553 lower_inode = ecryptfs_inode_to_lower(inode); 554 if (lower_inode->i_mapping->a_ops->bmap) 555 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping, 556 block); 557 return rc; 558 } 559 560 const struct address_space_operations ecryptfs_aops = { 561 .writepage = ecryptfs_writepage, 562 .readpage = ecryptfs_readpage, 563 .write_begin = ecryptfs_write_begin, 564 .write_end = ecryptfs_write_end, 565 .bmap = ecryptfs_bmap, 566 }; 567