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