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 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc) 62 { 63 int rc; 64 65 /* 66 * Refuse to write the page out if we are called from reclaim context 67 * since our writepage() path may potentially allocate memory when 68 * calling into the lower fs vfs_write() which may in turn invoke 69 * us again. 70 */ 71 if (current->flags & PF_MEMALLOC) { 72 redirty_page_for_writepage(wbc, page); 73 rc = 0; 74 goto out; 75 } 76 77 rc = ecryptfs_encrypt_page(page); 78 if (rc) { 79 ecryptfs_printk(KERN_WARNING, "Error encrypting " 80 "page (upper index [0x%.16lx])\n", page->index); 81 ClearPageUptodate(page); 82 goto out; 83 } 84 SetPageUptodate(page); 85 out: 86 unlock_page(page); 87 return rc; 88 } 89 90 static void strip_xattr_flag(char *page_virt, 91 struct ecryptfs_crypt_stat *crypt_stat) 92 { 93 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 94 size_t written; 95 96 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR; 97 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat, 98 &written); 99 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR; 100 } 101 } 102 103 /** 104 * Header Extent: 105 * Octets 0-7: Unencrypted file size (big-endian) 106 * Octets 8-15: eCryptfs special marker 107 * Octets 16-19: Flags 108 * Octet 16: File format version number (between 0 and 255) 109 * Octets 17-18: Reserved 110 * Octet 19: Bit 1 (lsb): Reserved 111 * Bit 2: Encrypted? 112 * Bits 3-8: Reserved 113 * Octets 20-23: Header extent size (big-endian) 114 * Octets 24-25: Number of header extents at front of file 115 * (big-endian) 116 * Octet 26: Begin RFC 2440 authentication token packet set 117 */ 118 119 /** 120 * ecryptfs_copy_up_encrypted_with_header 121 * @page: Sort of a ``virtual'' representation of the encrypted lower 122 * file. The actual lower file does not have the metadata in 123 * the header. This is locked. 124 * @crypt_stat: The eCryptfs inode's cryptographic context 125 * 126 * The ``view'' is the version of the file that userspace winds up 127 * seeing, with the header information inserted. 128 */ 129 static int 130 ecryptfs_copy_up_encrypted_with_header(struct page *page, 131 struct ecryptfs_crypt_stat *crypt_stat) 132 { 133 loff_t extent_num_in_page = 0; 134 loff_t num_extents_per_page = (PAGE_CACHE_SIZE 135 / crypt_stat->extent_size); 136 int rc = 0; 137 138 while (extent_num_in_page < num_extents_per_page) { 139 loff_t view_extent_num = ((((loff_t)page->index) 140 * num_extents_per_page) 141 + extent_num_in_page); 142 size_t num_header_extents_at_front = 143 (crypt_stat->metadata_size / crypt_stat->extent_size); 144 145 if (view_extent_num < num_header_extents_at_front) { 146 /* This is a header extent */ 147 char *page_virt; 148 149 page_virt = kmap_atomic(page, KM_USER0); 150 memset(page_virt, 0, PAGE_CACHE_SIZE); 151 /* TODO: Support more than one header extent */ 152 if (view_extent_num == 0) { 153 size_t written; 154 155 rc = ecryptfs_read_xattr_region( 156 page_virt, page->mapping->host); 157 strip_xattr_flag(page_virt + 16, crypt_stat); 158 ecryptfs_write_header_metadata(page_virt + 20, 159 crypt_stat, 160 &written); 161 } 162 kunmap_atomic(page_virt, KM_USER0); 163 flush_dcache_page(page); 164 if (rc) { 165 printk(KERN_ERR "%s: Error reading xattr " 166 "region; rc = [%d]\n", __func__, rc); 167 goto out; 168 } 169 } else { 170 /* This is an encrypted data extent */ 171 loff_t lower_offset = 172 ((view_extent_num * crypt_stat->extent_size) 173 - crypt_stat->metadata_size); 174 175 rc = ecryptfs_read_lower_page_segment( 176 page, (lower_offset >> PAGE_CACHE_SHIFT), 177 (lower_offset & ~PAGE_CACHE_MASK), 178 crypt_stat->extent_size, page->mapping->host); 179 if (rc) { 180 printk(KERN_ERR "%s: Error attempting to read " 181 "extent at offset [%lld] in the lower " 182 "file; rc = [%d]\n", __func__, 183 lower_offset, rc); 184 goto out; 185 } 186 } 187 extent_num_in_page++; 188 } 189 out: 190 return rc; 191 } 192 193 /** 194 * ecryptfs_readpage 195 * @file: An eCryptfs file 196 * @page: Page from eCryptfs inode mapping into which to stick the read data 197 * 198 * Read in a page, decrypting if necessary. 199 * 200 * Returns zero on success; non-zero on error. 201 */ 202 static int ecryptfs_readpage(struct file *file, struct page *page) 203 { 204 struct ecryptfs_crypt_stat *crypt_stat = 205 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat; 206 int rc = 0; 207 208 if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 209 rc = ecryptfs_read_lower_page_segment(page, page->index, 0, 210 PAGE_CACHE_SIZE, 211 page->mapping->host); 212 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 213 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 214 rc = ecryptfs_copy_up_encrypted_with_header(page, 215 crypt_stat); 216 if (rc) { 217 printk(KERN_ERR "%s: Error attempting to copy " 218 "the encrypted content from the lower " 219 "file whilst inserting the metadata " 220 "from the xattr into the header; rc = " 221 "[%d]\n", __func__, rc); 222 goto out; 223 } 224 225 } else { 226 rc = ecryptfs_read_lower_page_segment( 227 page, page->index, 0, PAGE_CACHE_SIZE, 228 page->mapping->host); 229 if (rc) { 230 printk(KERN_ERR "Error reading page; rc = " 231 "[%d]\n", rc); 232 goto out; 233 } 234 } 235 } else { 236 rc = ecryptfs_decrypt_page(page); 237 if (rc) { 238 ecryptfs_printk(KERN_ERR, "Error decrypting page; " 239 "rc = [%d]\n", rc); 240 goto out; 241 } 242 } 243 out: 244 if (rc) 245 ClearPageUptodate(page); 246 else 247 SetPageUptodate(page); 248 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n", 249 page->index); 250 unlock_page(page); 251 return rc; 252 } 253 254 /** 255 * Called with lower inode mutex held. 256 */ 257 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to) 258 { 259 struct inode *inode = page->mapping->host; 260 int end_byte_in_page; 261 262 if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index) 263 goto out; 264 end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE; 265 if (to > end_byte_in_page) 266 end_byte_in_page = to; 267 zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE); 268 out: 269 return 0; 270 } 271 272 /** 273 * ecryptfs_write_begin 274 * @file: The eCryptfs file 275 * @mapping: The eCryptfs object 276 * @pos: The file offset at which to start writing 277 * @len: Length of the write 278 * @flags: Various flags 279 * @pagep: Pointer to return the page 280 * @fsdata: Pointer to return fs data (unused) 281 * 282 * This function must zero any hole we create 283 * 284 * Returns zero on success; non-zero otherwise 285 */ 286 static int ecryptfs_write_begin(struct file *file, 287 struct address_space *mapping, 288 loff_t pos, unsigned len, unsigned flags, 289 struct page **pagep, void **fsdata) 290 { 291 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 292 struct page *page; 293 loff_t prev_page_end_size; 294 int rc = 0; 295 296 page = grab_cache_page_write_begin(mapping, index, flags); 297 if (!page) 298 return -ENOMEM; 299 *pagep = page; 300 301 prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT); 302 if (!PageUptodate(page)) { 303 struct ecryptfs_crypt_stat *crypt_stat = 304 &ecryptfs_inode_to_private(mapping->host)->crypt_stat; 305 306 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 307 rc = ecryptfs_read_lower_page_segment( 308 page, index, 0, PAGE_CACHE_SIZE, mapping->host); 309 if (rc) { 310 printk(KERN_ERR "%s: Error attemping to read " 311 "lower page segment; rc = [%d]\n", 312 __func__, rc); 313 ClearPageUptodate(page); 314 goto out; 315 } else 316 SetPageUptodate(page); 317 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 318 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 319 rc = ecryptfs_copy_up_encrypted_with_header( 320 page, crypt_stat); 321 if (rc) { 322 printk(KERN_ERR "%s: Error attempting " 323 "to copy the encrypted content " 324 "from the lower file whilst " 325 "inserting the metadata from " 326 "the xattr into the header; rc " 327 "= [%d]\n", __func__, rc); 328 ClearPageUptodate(page); 329 goto out; 330 } 331 SetPageUptodate(page); 332 } else { 333 rc = ecryptfs_read_lower_page_segment( 334 page, index, 0, PAGE_CACHE_SIZE, 335 mapping->host); 336 if (rc) { 337 printk(KERN_ERR "%s: Error reading " 338 "page; rc = [%d]\n", 339 __func__, rc); 340 ClearPageUptodate(page); 341 goto out; 342 } 343 SetPageUptodate(page); 344 } 345 } else { 346 if (prev_page_end_size 347 >= i_size_read(page->mapping->host)) { 348 zero_user(page, 0, PAGE_CACHE_SIZE); 349 } else { 350 rc = ecryptfs_decrypt_page(page); 351 if (rc) { 352 printk(KERN_ERR "%s: Error decrypting " 353 "page at index [%ld]; " 354 "rc = [%d]\n", 355 __func__, page->index, rc); 356 ClearPageUptodate(page); 357 goto out; 358 } 359 } 360 SetPageUptodate(page); 361 } 362 } 363 /* If creating a page or more of holes, zero them out via truncate. 364 * Note, this will increase i_size. */ 365 if (index != 0) { 366 if (prev_page_end_size > i_size_read(page->mapping->host)) { 367 rc = ecryptfs_truncate(file->f_path.dentry, 368 prev_page_end_size); 369 if (rc) { 370 printk(KERN_ERR "%s: Error on attempt to " 371 "truncate to (higher) offset [%lld];" 372 " rc = [%d]\n", __func__, 373 prev_page_end_size, rc); 374 goto out; 375 } 376 } 377 } 378 /* Writing to a new page, and creating a small hole from start 379 * of page? Zero it out. */ 380 if ((i_size_read(mapping->host) == prev_page_end_size) 381 && (pos != 0)) 382 zero_user(page, 0, PAGE_CACHE_SIZE); 383 out: 384 return rc; 385 } 386 387 /** 388 * ecryptfs_write_inode_size_to_header 389 * 390 * Writes the lower file size to the first 8 bytes of the header. 391 * 392 * Returns zero on success; non-zero on error. 393 */ 394 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) 395 { 396 char *file_size_virt; 397 int rc; 398 399 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); 400 if (!file_size_virt) { 401 rc = -ENOMEM; 402 goto out; 403 } 404 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); 405 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, 406 sizeof(u64)); 407 kfree(file_size_virt); 408 if (rc < 0) 409 printk(KERN_ERR "%s: Error writing file size to header; " 410 "rc = [%d]\n", __func__, rc); 411 else 412 rc = 0; 413 out: 414 return rc; 415 } 416 417 struct kmem_cache *ecryptfs_xattr_cache; 418 419 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) 420 { 421 ssize_t size; 422 void *xattr_virt; 423 struct dentry *lower_dentry = 424 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry; 425 struct inode *lower_inode = lower_dentry->d_inode; 426 int rc; 427 428 if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) { 429 printk(KERN_WARNING 430 "No support for setting xattr in lower filesystem\n"); 431 rc = -ENOSYS; 432 goto out; 433 } 434 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); 435 if (!xattr_virt) { 436 printk(KERN_ERR "Out of memory whilst attempting to write " 437 "inode size to xattr\n"); 438 rc = -ENOMEM; 439 goto out; 440 } 441 mutex_lock(&lower_inode->i_mutex); 442 size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 443 xattr_virt, PAGE_CACHE_SIZE); 444 if (size < 0) 445 size = 8; 446 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt); 447 rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 448 xattr_virt, size, 0); 449 mutex_unlock(&lower_inode->i_mutex); 450 if (rc) 451 printk(KERN_ERR "Error whilst attempting to write inode size " 452 "to lower file xattr; rc = [%d]\n", rc); 453 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); 454 out: 455 return rc; 456 } 457 458 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) 459 { 460 struct ecryptfs_crypt_stat *crypt_stat; 461 462 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 463 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); 464 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) 465 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); 466 else 467 return ecryptfs_write_inode_size_to_header(ecryptfs_inode); 468 } 469 470 /** 471 * ecryptfs_write_end 472 * @file: The eCryptfs file object 473 * @mapping: The eCryptfs object 474 * @pos: The file position 475 * @len: The length of the data (unused) 476 * @copied: The amount of data copied 477 * @page: The eCryptfs page 478 * @fsdata: The fsdata (unused) 479 * 480 * This is where we encrypt the data and pass the encrypted data to 481 * the lower filesystem. In OpenPGP-compatible mode, we operate on 482 * entire underlying packets. 483 */ 484 static int ecryptfs_write_end(struct file *file, 485 struct address_space *mapping, 486 loff_t pos, unsigned len, unsigned copied, 487 struct page *page, void *fsdata) 488 { 489 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 490 unsigned from = pos & (PAGE_CACHE_SIZE - 1); 491 unsigned to = from + copied; 492 struct inode *ecryptfs_inode = mapping->host; 493 struct ecryptfs_crypt_stat *crypt_stat = 494 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 495 int rc; 496 int need_unlock_page = 1; 497 498 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" 499 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to); 500 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 501 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, 502 to); 503 if (!rc) { 504 rc = copied; 505 fsstack_copy_inode_size(ecryptfs_inode, 506 ecryptfs_inode_to_lower(ecryptfs_inode)); 507 } 508 goto out; 509 } 510 /* Fills in zeros if 'to' goes beyond inode size */ 511 rc = fill_zeros_to_end_of_page(page, to); 512 if (rc) { 513 ecryptfs_printk(KERN_WARNING, "Error attempting to fill " 514 "zeros in page with index = [0x%.16lx]\n", index); 515 goto out; 516 } 517 set_page_dirty(page); 518 unlock_page(page); 519 need_unlock_page = 0; 520 if (pos + copied > i_size_read(ecryptfs_inode)) { 521 i_size_write(ecryptfs_inode, pos + copied); 522 ecryptfs_printk(KERN_DEBUG, "Expanded file size to " 523 "[0x%.16llx]\n", 524 (unsigned long long)i_size_read(ecryptfs_inode)); 525 balance_dirty_pages_ratelimited(mapping); 526 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode); 527 if (rc) { 528 printk(KERN_ERR "Error writing inode size to metadata; " 529 "rc = [%d]\n", rc); 530 goto out; 531 } 532 } 533 rc = copied; 534 out: 535 if (need_unlock_page) 536 unlock_page(page); 537 page_cache_release(page); 538 return rc; 539 } 540 541 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block) 542 { 543 int rc = 0; 544 struct inode *inode; 545 struct inode *lower_inode; 546 547 inode = (struct inode *)mapping->host; 548 lower_inode = ecryptfs_inode_to_lower(inode); 549 if (lower_inode->i_mapping->a_ops->bmap) 550 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping, 551 block); 552 return rc; 553 } 554 555 const struct address_space_operations ecryptfs_aops = { 556 .writepage = ecryptfs_writepage, 557 .readpage = ecryptfs_readpage, 558 .write_begin = ecryptfs_write_begin, 559 .write_end = ecryptfs_write_end, 560 .bmap = ecryptfs_bmap, 561 }; 562