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/scatterlist.h> 34 #include <linux/slab.h> 35 #include <asm/unaligned.h> 36 #include "ecryptfs_kernel.h" 37 38 /** 39 * ecryptfs_get_locked_page 40 * 41 * Get one page from cache or lower f/s, return error otherwise. 42 * 43 * Returns locked and up-to-date page (if ok), with increased 44 * refcnt. 45 */ 46 struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index) 47 { 48 struct page *page = read_mapping_page(inode->i_mapping, index, NULL); 49 if (!IS_ERR(page)) 50 lock_page(page); 51 return page; 52 } 53 54 /** 55 * ecryptfs_writepage 56 * @page: Page that is locked before this call is made 57 * 58 * Returns zero on success; non-zero otherwise 59 * 60 * This is where we encrypt the data and pass the encrypted data to 61 * the lower filesystem. In OpenPGP-compatible mode, we operate on 62 * entire underlying packets. 63 */ 64 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc) 65 { 66 int rc; 67 68 rc = ecryptfs_encrypt_page(page); 69 if (rc) { 70 ecryptfs_printk(KERN_WARNING, "Error encrypting " 71 "page (upper index [0x%.16lx])\n", page->index); 72 ClearPageUptodate(page); 73 goto out; 74 } 75 SetPageUptodate(page); 76 out: 77 unlock_page(page); 78 return rc; 79 } 80 81 static void strip_xattr_flag(char *page_virt, 82 struct ecryptfs_crypt_stat *crypt_stat) 83 { 84 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 85 size_t written; 86 87 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR; 88 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat, 89 &written); 90 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR; 91 } 92 } 93 94 /** 95 * Header Extent: 96 * Octets 0-7: Unencrypted file size (big-endian) 97 * Octets 8-15: eCryptfs special marker 98 * Octets 16-19: Flags 99 * Octet 16: File format version number (between 0 and 255) 100 * Octets 17-18: Reserved 101 * Octet 19: Bit 1 (lsb): Reserved 102 * Bit 2: Encrypted? 103 * Bits 3-8: Reserved 104 * Octets 20-23: Header extent size (big-endian) 105 * Octets 24-25: Number of header extents at front of file 106 * (big-endian) 107 * Octet 26: Begin RFC 2440 authentication token packet set 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_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 size_t num_header_extents_at_front = 134 (crypt_stat->metadata_size / crypt_stat->extent_size); 135 136 if (view_extent_num < num_header_extents_at_front) { 137 /* This is a header extent */ 138 char *page_virt; 139 140 page_virt = kmap_atomic(page); 141 memset(page_virt, 0, PAGE_SIZE); 142 /* TODO: Support more than one header extent */ 143 if (view_extent_num == 0) { 144 size_t written; 145 146 rc = ecryptfs_read_xattr_region( 147 page_virt, page->mapping->host); 148 strip_xattr_flag(page_virt + 16, crypt_stat); 149 ecryptfs_write_header_metadata(page_virt + 20, 150 crypt_stat, 151 &written); 152 } 153 kunmap_atomic(page_virt); 154 flush_dcache_page(page); 155 if (rc) { 156 printk(KERN_ERR "%s: Error reading xattr " 157 "region; rc = [%d]\n", __func__, rc); 158 goto out; 159 } 160 } else { 161 /* This is an encrypted data extent */ 162 loff_t lower_offset = 163 ((view_extent_num * crypt_stat->extent_size) 164 - crypt_stat->metadata_size); 165 166 rc = ecryptfs_read_lower_page_segment( 167 page, (lower_offset >> PAGE_SHIFT), 168 (lower_offset & ~PAGE_MASK), 169 crypt_stat->extent_size, page->mapping->host); 170 if (rc) { 171 printk(KERN_ERR "%s: Error attempting to read " 172 "extent at offset [%lld] in the lower " 173 "file; rc = [%d]\n", __func__, 174 lower_offset, rc); 175 goto out; 176 } 177 } 178 extent_num_in_page++; 179 } 180 out: 181 return rc; 182 } 183 184 /** 185 * ecryptfs_readpage 186 * @file: An eCryptfs file 187 * @page: Page from eCryptfs inode mapping into which to stick the read data 188 * 189 * Read in a page, decrypting if necessary. 190 * 191 * Returns zero on success; non-zero on error. 192 */ 193 static int ecryptfs_readpage(struct file *file, struct page *page) 194 { 195 struct ecryptfs_crypt_stat *crypt_stat = 196 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat; 197 int rc = 0; 198 199 if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 200 rc = ecryptfs_read_lower_page_segment(page, page->index, 0, 201 PAGE_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", __func__, rc); 213 goto out; 214 } 215 216 } else { 217 rc = ecryptfs_read_lower_page_segment( 218 page, page->index, 0, PAGE_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%.16lx]\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_SIZE) != page->index) 254 goto out; 255 end_byte_in_page = i_size_read(inode) % PAGE_SIZE; 256 if (to > end_byte_in_page) 257 end_byte_in_page = to; 258 zero_user_segment(page, end_byte_in_page, PAGE_SIZE); 259 out: 260 return 0; 261 } 262 263 /** 264 * ecryptfs_write_begin 265 * @file: The eCryptfs file 266 * @mapping: The eCryptfs object 267 * @pos: The file offset at which to start writing 268 * @len: Length of the write 269 * @flags: Various flags 270 * @pagep: Pointer to return the page 271 * @fsdata: Pointer to return fs data (unused) 272 * 273 * This function must zero any hole we create 274 * 275 * Returns zero on success; non-zero otherwise 276 */ 277 static int ecryptfs_write_begin(struct file *file, 278 struct address_space *mapping, 279 loff_t pos, unsigned len, unsigned flags, 280 struct page **pagep, void **fsdata) 281 { 282 pgoff_t index = pos >> PAGE_SHIFT; 283 struct page *page; 284 loff_t prev_page_end_size; 285 int rc = 0; 286 287 page = grab_cache_page_write_begin(mapping, index, flags); 288 if (!page) 289 return -ENOMEM; 290 *pagep = page; 291 292 prev_page_end_size = ((loff_t)index << PAGE_SHIFT); 293 if (!PageUptodate(page)) { 294 struct ecryptfs_crypt_stat *crypt_stat = 295 &ecryptfs_inode_to_private(mapping->host)->crypt_stat; 296 297 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 298 rc = ecryptfs_read_lower_page_segment( 299 page, index, 0, PAGE_SIZE, mapping->host); 300 if (rc) { 301 printk(KERN_ERR "%s: Error attempting to read " 302 "lower page segment; rc = [%d]\n", 303 __func__, rc); 304 ClearPageUptodate(page); 305 goto out; 306 } else 307 SetPageUptodate(page); 308 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 309 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 310 rc = ecryptfs_copy_up_encrypted_with_header( 311 page, crypt_stat); 312 if (rc) { 313 printk(KERN_ERR "%s: Error attempting " 314 "to copy the encrypted content " 315 "from the lower file whilst " 316 "inserting the metadata from " 317 "the xattr into the header; rc " 318 "= [%d]\n", __func__, rc); 319 ClearPageUptodate(page); 320 goto out; 321 } 322 SetPageUptodate(page); 323 } else { 324 rc = ecryptfs_read_lower_page_segment( 325 page, index, 0, PAGE_SIZE, 326 mapping->host); 327 if (rc) { 328 printk(KERN_ERR "%s: Error reading " 329 "page; rc = [%d]\n", 330 __func__, rc); 331 ClearPageUptodate(page); 332 goto out; 333 } 334 SetPageUptodate(page); 335 } 336 } else { 337 if (prev_page_end_size 338 >= i_size_read(page->mapping->host)) { 339 zero_user(page, 0, PAGE_SIZE); 340 SetPageUptodate(page); 341 } else if (len < PAGE_SIZE) { 342 rc = ecryptfs_decrypt_page(page); 343 if (rc) { 344 printk(KERN_ERR "%s: Error decrypting " 345 "page at index [%ld]; " 346 "rc = [%d]\n", 347 __func__, page->index, rc); 348 ClearPageUptodate(page); 349 goto out; 350 } 351 SetPageUptodate(page); 352 } 353 } 354 } 355 /* If creating a page or more of holes, zero them out via truncate. 356 * Note, this will increase i_size. */ 357 if (index != 0) { 358 if (prev_page_end_size > i_size_read(page->mapping->host)) { 359 rc = ecryptfs_truncate(file->f_path.dentry, 360 prev_page_end_size); 361 if (rc) { 362 printk(KERN_ERR "%s: Error on attempt to " 363 "truncate to (higher) offset [%lld];" 364 " rc = [%d]\n", __func__, 365 prev_page_end_size, rc); 366 goto out; 367 } 368 } 369 } 370 /* Writing to a new page, and creating a small hole from start 371 * of page? Zero it out. */ 372 if ((i_size_read(mapping->host) == prev_page_end_size) 373 && (pos != 0)) 374 zero_user(page, 0, PAGE_SIZE); 375 out: 376 if (unlikely(rc)) { 377 unlock_page(page); 378 put_page(page); 379 *pagep = NULL; 380 } 381 return rc; 382 } 383 384 /** 385 * ecryptfs_write_inode_size_to_header 386 * 387 * Writes the lower file size to the first 8 bytes of the header. 388 * 389 * Returns zero on success; non-zero on error. 390 */ 391 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) 392 { 393 char *file_size_virt; 394 int rc; 395 396 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); 397 if (!file_size_virt) { 398 rc = -ENOMEM; 399 goto out; 400 } 401 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); 402 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, 403 sizeof(u64)); 404 kfree(file_size_virt); 405 if (rc < 0) 406 printk(KERN_ERR "%s: Error writing file size to header; " 407 "rc = [%d]\n", __func__, rc); 408 else 409 rc = 0; 410 out: 411 return rc; 412 } 413 414 struct kmem_cache *ecryptfs_xattr_cache; 415 416 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) 417 { 418 ssize_t size; 419 void *xattr_virt; 420 struct dentry *lower_dentry = 421 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry; 422 struct inode *lower_inode = d_inode(lower_dentry); 423 int rc; 424 425 if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) { 426 printk(KERN_WARNING 427 "No support for setting xattr in lower filesystem\n"); 428 rc = -ENOSYS; 429 goto out; 430 } 431 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); 432 if (!xattr_virt) { 433 printk(KERN_ERR "Out of memory whilst attempting to write " 434 "inode size to xattr\n"); 435 rc = -ENOMEM; 436 goto out; 437 } 438 inode_lock(lower_inode); 439 size = lower_inode->i_op->getxattr(lower_dentry, lower_inode, 440 ECRYPTFS_XATTR_NAME, 441 xattr_virt, PAGE_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, lower_inode, 446 ECRYPTFS_XATTR_NAME, 447 xattr_virt, size, 0); 448 inode_unlock(lower_inode); 449 if (rc) 450 printk(KERN_ERR "Error whilst attempting to write inode size " 451 "to lower file xattr; rc = [%d]\n", rc); 452 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); 453 out: 454 return rc; 455 } 456 457 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) 458 { 459 struct ecryptfs_crypt_stat *crypt_stat; 460 461 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 462 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); 463 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) 464 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); 465 else 466 return ecryptfs_write_inode_size_to_header(ecryptfs_inode); 467 } 468 469 /** 470 * ecryptfs_write_end 471 * @file: The eCryptfs file object 472 * @mapping: The eCryptfs object 473 * @pos: The file position 474 * @len: The length of the data (unused) 475 * @copied: The amount of data copied 476 * @page: The eCryptfs page 477 * @fsdata: The fsdata (unused) 478 */ 479 static int ecryptfs_write_end(struct file *file, 480 struct address_space *mapping, 481 loff_t pos, unsigned len, unsigned copied, 482 struct page *page, void *fsdata) 483 { 484 pgoff_t index = pos >> PAGE_SHIFT; 485 unsigned from = pos & (PAGE_SIZE - 1); 486 unsigned to = from + copied; 487 struct inode *ecryptfs_inode = mapping->host; 488 struct ecryptfs_crypt_stat *crypt_stat = 489 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 490 int rc; 491 492 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" 493 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to); 494 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 495 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, 496 to); 497 if (!rc) { 498 rc = copied; 499 fsstack_copy_inode_size(ecryptfs_inode, 500 ecryptfs_inode_to_lower(ecryptfs_inode)); 501 } 502 goto out; 503 } 504 if (!PageUptodate(page)) { 505 if (copied < PAGE_SIZE) { 506 rc = 0; 507 goto out; 508 } 509 SetPageUptodate(page); 510 } 511 /* Fills in zeros if 'to' goes beyond inode size */ 512 rc = fill_zeros_to_end_of_page(page, to); 513 if (rc) { 514 ecryptfs_printk(KERN_WARNING, "Error attempting to fill " 515 "zeros in page with index = [0x%.16lx]\n", index); 516 goto out; 517 } 518 rc = ecryptfs_encrypt_page(page); 519 if (rc) { 520 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper " 521 "index [0x%.16lx])\n", index); 522 goto out; 523 } 524 if (pos + copied > i_size_read(ecryptfs_inode)) { 525 i_size_write(ecryptfs_inode, pos + copied); 526 ecryptfs_printk(KERN_DEBUG, "Expanded file size to " 527 "[0x%.16llx]\n", 528 (unsigned long long)i_size_read(ecryptfs_inode)); 529 } 530 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode); 531 if (rc) 532 printk(KERN_ERR "Error writing inode size to metadata; " 533 "rc = [%d]\n", rc); 534 else 535 rc = copied; 536 out: 537 unlock_page(page); 538 put_page(page); 539 return rc; 540 } 541 542 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block) 543 { 544 int rc = 0; 545 struct inode *inode; 546 struct inode *lower_inode; 547 548 inode = (struct inode *)mapping->host; 549 lower_inode = ecryptfs_inode_to_lower(inode); 550 if (lower_inode->i_mapping->a_ops->bmap) 551 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping, 552 block); 553 return rc; 554 } 555 556 const struct address_space_operations ecryptfs_aops = { 557 .writepage = ecryptfs_writepage, 558 .readpage = ecryptfs_readpage, 559 .write_begin = ecryptfs_write_begin, 560 .write_end = ecryptfs_write_end, 561 .bmap = ecryptfs_bmap, 562 }; 563