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 file *file, loff_t index) 48 { 49 struct dentry *dentry; 50 struct inode *inode; 51 struct address_space *mapping; 52 struct page *page; 53 54 dentry = file->f_path.dentry; 55 inode = dentry->d_inode; 56 mapping = inode->i_mapping; 57 page = read_mapping_page(mapping, index, (void *)file); 58 if (!IS_ERR(page)) 59 lock_page(page); 60 return page; 61 } 62 63 /** 64 * ecryptfs_writepage 65 * @page: Page that is locked before this call is made 66 * 67 * Returns zero on success; non-zero otherwise 68 */ 69 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc) 70 { 71 int rc; 72 73 rc = ecryptfs_encrypt_page(page); 74 if (rc) { 75 ecryptfs_printk(KERN_WARNING, "Error encrypting " 76 "page (upper index [0x%.16x])\n", page->index); 77 ClearPageUptodate(page); 78 goto out; 79 } 80 SetPageUptodate(page); 81 unlock_page(page); 82 out: 83 return rc; 84 } 85 86 /** 87 * Header Extent: 88 * Octets 0-7: Unencrypted file size (big-endian) 89 * Octets 8-15: eCryptfs special marker 90 * Octets 16-19: Flags 91 * Octet 16: File format version number (between 0 and 255) 92 * Octets 17-18: Reserved 93 * Octet 19: Bit 1 (lsb): Reserved 94 * Bit 2: Encrypted? 95 * Bits 3-8: Reserved 96 * Octets 20-23: Header extent size (big-endian) 97 * Octets 24-25: Number of header extents at front of file 98 * (big-endian) 99 * Octet 26: Begin RFC 2440 authentication token packet set 100 */ 101 static void set_header_info(char *page_virt, 102 struct ecryptfs_crypt_stat *crypt_stat) 103 { 104 size_t written; 105 size_t save_num_header_bytes_at_front = 106 crypt_stat->num_header_bytes_at_front; 107 108 crypt_stat->num_header_bytes_at_front = 109 ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE; 110 ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written); 111 crypt_stat->num_header_bytes_at_front = 112 save_num_header_bytes_at_front; 113 } 114 115 /** 116 * ecryptfs_copy_up_encrypted_with_header 117 * @page: Sort of a ``virtual'' representation of the encrypted lower 118 * file. The actual lower file does not have the metadata in 119 * the header. This is locked. 120 * @crypt_stat: The eCryptfs inode's cryptographic context 121 * 122 * The ``view'' is the version of the file that userspace winds up 123 * seeing, with the header information inserted. 124 */ 125 static int 126 ecryptfs_copy_up_encrypted_with_header(struct page *page, 127 struct ecryptfs_crypt_stat *crypt_stat) 128 { 129 loff_t extent_num_in_page = 0; 130 loff_t num_extents_per_page = (PAGE_CACHE_SIZE 131 / crypt_stat->extent_size); 132 int rc = 0; 133 134 while (extent_num_in_page < num_extents_per_page) { 135 loff_t view_extent_num = ((((loff_t)page->index) 136 * num_extents_per_page) 137 + extent_num_in_page); 138 size_t num_header_extents_at_front = 139 (crypt_stat->num_header_bytes_at_front 140 / crypt_stat->extent_size); 141 142 if (view_extent_num < num_header_extents_at_front) { 143 /* This is a header extent */ 144 char *page_virt; 145 146 page_virt = kmap_atomic(page, KM_USER0); 147 memset(page_virt, 0, PAGE_CACHE_SIZE); 148 /* TODO: Support more than one header extent */ 149 if (view_extent_num == 0) { 150 rc = ecryptfs_read_xattr_region( 151 page_virt, page->mapping->host); 152 set_header_info(page_virt, crypt_stat); 153 } 154 kunmap_atomic(page_virt, KM_USER0); 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->num_header_bytes_at_front); 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(file->f_path.dentry->d_inode)->crypt_stat; 198 int rc = 0; 199 200 if (!crypt_stat 201 || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED) 202 || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) { 203 ecryptfs_printk(KERN_DEBUG, 204 "Passing through unencrypted page\n"); 205 rc = ecryptfs_read_lower_page_segment(page, page->index, 0, 206 PAGE_CACHE_SIZE, 207 page->mapping->host); 208 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 209 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 210 rc = ecryptfs_copy_up_encrypted_with_header(page, 211 crypt_stat); 212 if (rc) { 213 printk(KERN_ERR "%s: Error attempting to copy " 214 "the encrypted content from the lower " 215 "file whilst inserting the metadata " 216 "from the xattr into the header; rc = " 217 "[%d]\n", __func__, rc); 218 goto out; 219 } 220 221 } else { 222 rc = ecryptfs_read_lower_page_segment( 223 page, page->index, 0, PAGE_CACHE_SIZE, 224 page->mapping->host); 225 if (rc) { 226 printk(KERN_ERR "Error reading page; rc = " 227 "[%d]\n", rc); 228 goto out; 229 } 230 } 231 } else { 232 rc = ecryptfs_decrypt_page(page); 233 if (rc) { 234 ecryptfs_printk(KERN_ERR, "Error decrypting page; " 235 "rc = [%d]\n", rc); 236 goto out; 237 } 238 } 239 out: 240 if (rc) 241 ClearPageUptodate(page); 242 else 243 SetPageUptodate(page); 244 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n", 245 page->index); 246 unlock_page(page); 247 return rc; 248 } 249 250 /** 251 * Called with lower inode mutex held. 252 */ 253 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to) 254 { 255 struct inode *inode = page->mapping->host; 256 int end_byte_in_page; 257 258 if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index) 259 goto out; 260 end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE; 261 if (to > end_byte_in_page) 262 end_byte_in_page = to; 263 zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE); 264 out: 265 return 0; 266 } 267 268 /** 269 * ecryptfs_write_begin 270 * @file: The eCryptfs file 271 * @mapping: The eCryptfs object 272 * @pos: The file offset at which to start writing 273 * @len: Length of the write 274 * @flags: Various flags 275 * @pagep: Pointer to return the page 276 * @fsdata: Pointer to return fs data (unused) 277 * 278 * This function must zero any hole we create 279 * 280 * Returns zero on success; non-zero otherwise 281 */ 282 static int ecryptfs_write_begin(struct file *file, 283 struct address_space *mapping, 284 loff_t pos, unsigned len, unsigned flags, 285 struct page **pagep, void **fsdata) 286 { 287 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 288 struct page *page; 289 loff_t prev_page_end_size; 290 int rc = 0; 291 292 page = grab_cache_page_write_begin(mapping, index, flags); 293 if (!page) 294 return -ENOMEM; 295 *pagep = page; 296 297 if (!PageUptodate(page)) { 298 struct ecryptfs_crypt_stat *crypt_stat = 299 &ecryptfs_inode_to_private( 300 file->f_path.dentry->d_inode)->crypt_stat; 301 302 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED) 303 || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) { 304 rc = ecryptfs_read_lower_page_segment( 305 page, index, 0, PAGE_CACHE_SIZE, mapping->host); 306 if (rc) { 307 printk(KERN_ERR "%s: Error attemping to read " 308 "lower page segment; rc = [%d]\n", 309 __func__, rc); 310 ClearPageUptodate(page); 311 goto out; 312 } else 313 SetPageUptodate(page); 314 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 315 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 316 rc = ecryptfs_copy_up_encrypted_with_header( 317 page, crypt_stat); 318 if (rc) { 319 printk(KERN_ERR "%s: Error attempting " 320 "to copy the encrypted content " 321 "from the lower file whilst " 322 "inserting the metadata from " 323 "the xattr into the header; rc " 324 "= [%d]\n", __func__, rc); 325 ClearPageUptodate(page); 326 goto out; 327 } 328 SetPageUptodate(page); 329 } else { 330 rc = ecryptfs_read_lower_page_segment( 331 page, index, 0, PAGE_CACHE_SIZE, 332 mapping->host); 333 if (rc) { 334 printk(KERN_ERR "%s: Error reading " 335 "page; rc = [%d]\n", 336 __func__, rc); 337 ClearPageUptodate(page); 338 goto out; 339 } 340 SetPageUptodate(page); 341 } 342 } else { 343 rc = ecryptfs_decrypt_page(page); 344 if (rc) { 345 printk(KERN_ERR "%s: Error decrypting page " 346 "at index [%ld]; rc = [%d]\n", 347 __func__, page->index, rc); 348 ClearPageUptodate(page); 349 goto out; 350 } 351 SetPageUptodate(page); 352 } 353 } 354 prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT); 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_CACHE_SIZE); 375 out: 376 return rc; 377 } 378 379 /** 380 * ecryptfs_write_inode_size_to_header 381 * 382 * Writes the lower file size to the first 8 bytes of the header. 383 * 384 * Returns zero on success; non-zero on error. 385 */ 386 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) 387 { 388 char *file_size_virt; 389 int rc; 390 391 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); 392 if (!file_size_virt) { 393 rc = -ENOMEM; 394 goto out; 395 } 396 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); 397 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, 398 sizeof(u64)); 399 kfree(file_size_virt); 400 if (rc < 0) 401 printk(KERN_ERR "%s: Error writing file size to header; " 402 "rc = [%d]\n", __func__, rc); 403 else 404 rc = 0; 405 out: 406 return rc; 407 } 408 409 struct kmem_cache *ecryptfs_xattr_cache; 410 411 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) 412 { 413 ssize_t size; 414 void *xattr_virt; 415 struct dentry *lower_dentry = 416 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry; 417 struct inode *lower_inode = lower_dentry->d_inode; 418 int rc; 419 420 if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) { 421 printk(KERN_WARNING 422 "No support for setting xattr in lower filesystem\n"); 423 rc = -ENOSYS; 424 goto out; 425 } 426 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); 427 if (!xattr_virt) { 428 printk(KERN_ERR "Out of memory whilst attempting to write " 429 "inode size to xattr\n"); 430 rc = -ENOMEM; 431 goto out; 432 } 433 mutex_lock(&lower_inode->i_mutex); 434 size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 435 xattr_virt, PAGE_CACHE_SIZE); 436 if (size < 0) 437 size = 8; 438 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt); 439 rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 440 xattr_virt, size, 0); 441 mutex_unlock(&lower_inode->i_mutex); 442 if (rc) 443 printk(KERN_ERR "Error whilst attempting to write inode size " 444 "to lower file xattr; rc = [%d]\n", rc); 445 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); 446 out: 447 return rc; 448 } 449 450 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) 451 { 452 struct ecryptfs_crypt_stat *crypt_stat; 453 454 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 455 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); 456 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) 457 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); 458 else 459 return ecryptfs_write_inode_size_to_header(ecryptfs_inode); 460 } 461 462 /** 463 * ecryptfs_write_end 464 * @file: The eCryptfs file object 465 * @mapping: The eCryptfs object 466 * @pos: The file position 467 * @len: The length of the data (unused) 468 * @copied: The amount of data copied 469 * @page: The eCryptfs page 470 * @fsdata: The fsdata (unused) 471 * 472 * This is where we encrypt the data and pass the encrypted data to 473 * the lower filesystem. In OpenPGP-compatible mode, we operate on 474 * entire underlying packets. 475 */ 476 static int ecryptfs_write_end(struct file *file, 477 struct address_space *mapping, 478 loff_t pos, unsigned len, unsigned copied, 479 struct page *page, void *fsdata) 480 { 481 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 482 unsigned from = pos & (PAGE_CACHE_SIZE - 1); 483 unsigned to = from + copied; 484 struct inode *ecryptfs_inode = mapping->host; 485 struct ecryptfs_crypt_stat *crypt_stat = 486 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat; 487 int rc; 488 489 if (crypt_stat->flags & ECRYPTFS_NEW_FILE) { 490 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in " 491 "crypt_stat at memory location [%p]\n", crypt_stat); 492 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE); 493 } else 494 ecryptfs_printk(KERN_DEBUG, "Not a new file\n"); 495 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" 496 "(page w/ index = [0x%.16x], to = [%d])\n", index, to); 497 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 498 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, 499 to); 500 if (!rc) { 501 rc = copied; 502 fsstack_copy_inode_size(ecryptfs_inode, 503 ecryptfs_inode_to_lower(ecryptfs_inode)); 504 } 505 goto out; 506 } 507 /* Fills in zeros if 'to' goes beyond inode size */ 508 rc = fill_zeros_to_end_of_page(page, to); 509 if (rc) { 510 ecryptfs_printk(KERN_WARNING, "Error attempting to fill " 511 "zeros in page with index = [0x%.16x]\n", index); 512 goto out; 513 } 514 rc = ecryptfs_encrypt_page(page); 515 if (rc) { 516 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper " 517 "index [0x%.16x])\n", index); 518 goto out; 519 } 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%.16x]\n", i_size_read(ecryptfs_inode)); 524 } 525 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode); 526 if (rc) 527 printk(KERN_ERR "Error writing inode size to metadata; " 528 "rc = [%d]\n", rc); 529 else 530 rc = copied; 531 out: 532 unlock_page(page); 533 page_cache_release(page); 534 return rc; 535 } 536 537 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block) 538 { 539 int rc = 0; 540 struct inode *inode; 541 struct inode *lower_inode; 542 543 inode = (struct inode *)mapping->host; 544 lower_inode = ecryptfs_inode_to_lower(inode); 545 if (lower_inode->i_mapping->a_ops->bmap) 546 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping, 547 block); 548 return rc; 549 } 550 551 const struct address_space_operations ecryptfs_aops = { 552 .writepage = ecryptfs_writepage, 553 .readpage = ecryptfs_readpage, 554 .write_begin = ecryptfs_write_begin, 555 .write_end = ecryptfs_write_end, 556 .bmap = ecryptfs_bmap, 557 }; 558