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 static void strip_xattr_flag(char *page_virt, 87 struct ecryptfs_crypt_stat *crypt_stat) 88 { 89 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 90 size_t written; 91 92 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR; 93 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat, 94 &written); 95 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR; 96 } 97 } 98 99 /** 100 * Header Extent: 101 * Octets 0-7: Unencrypted file size (big-endian) 102 * Octets 8-15: eCryptfs special marker 103 * Octets 16-19: Flags 104 * Octet 16: File format version number (between 0 and 255) 105 * Octets 17-18: Reserved 106 * Octet 19: Bit 1 (lsb): Reserved 107 * Bit 2: Encrypted? 108 * Bits 3-8: Reserved 109 * Octets 20-23: Header extent size (big-endian) 110 * Octets 24-25: Number of header extents at front of file 111 * (big-endian) 112 * Octet 26: Begin RFC 2440 authentication token packet set 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->metadata_size / crypt_stat->extent_size); 140 141 if (view_extent_num < num_header_extents_at_front) { 142 /* This is a header extent */ 143 char *page_virt; 144 145 page_virt = kmap_atomic(page, KM_USER0); 146 memset(page_virt, 0, PAGE_CACHE_SIZE); 147 /* TODO: Support more than one header extent */ 148 if (view_extent_num == 0) { 149 size_t written; 150 151 rc = ecryptfs_read_xattr_region( 152 page_virt, page->mapping->host); 153 strip_xattr_flag(page_virt + 16, crypt_stat); 154 ecryptfs_write_header_metadata(page_virt + 20, 155 crypt_stat, 156 &written); 157 } 158 kunmap_atomic(page_virt, KM_USER0); 159 flush_dcache_page(page); 160 if (rc) { 161 printk(KERN_ERR "%s: Error reading xattr " 162 "region; rc = [%d]\n", __func__, rc); 163 goto out; 164 } 165 } else { 166 /* This is an encrypted data extent */ 167 loff_t lower_offset = 168 ((view_extent_num * crypt_stat->extent_size) 169 - crypt_stat->metadata_size); 170 171 rc = ecryptfs_read_lower_page_segment( 172 page, (lower_offset >> PAGE_CACHE_SHIFT), 173 (lower_offset & ~PAGE_CACHE_MASK), 174 crypt_stat->extent_size, page->mapping->host); 175 if (rc) { 176 printk(KERN_ERR "%s: Error attempting to read " 177 "extent at offset [%lld] in the lower " 178 "file; rc = [%d]\n", __func__, 179 lower_offset, rc); 180 goto out; 181 } 182 } 183 extent_num_in_page++; 184 } 185 out: 186 return rc; 187 } 188 189 /** 190 * ecryptfs_readpage 191 * @file: An eCryptfs file 192 * @page: Page from eCryptfs inode mapping into which to stick the read data 193 * 194 * Read in a page, decrypting if necessary. 195 * 196 * Returns zero on success; non-zero on error. 197 */ 198 static int ecryptfs_readpage(struct file *file, struct page *page) 199 { 200 struct ecryptfs_crypt_stat *crypt_stat = 201 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat; 202 int rc = 0; 203 204 if (!crypt_stat 205 || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED) 206 || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) { 207 ecryptfs_printk(KERN_DEBUG, 208 "Passing through unencrypted page\n"); 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%.16x]\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 if (!PageUptodate(page)) { 302 struct ecryptfs_crypt_stat *crypt_stat = 303 &ecryptfs_inode_to_private( 304 file->f_path.dentry->d_inode)->crypt_stat; 305 306 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED) 307 || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) { 308 rc = ecryptfs_read_lower_page_segment( 309 page, index, 0, PAGE_CACHE_SIZE, mapping->host); 310 if (rc) { 311 printk(KERN_ERR "%s: Error attemping to read " 312 "lower page segment; rc = [%d]\n", 313 __func__, rc); 314 ClearPageUptodate(page); 315 goto out; 316 } else 317 SetPageUptodate(page); 318 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 319 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 320 rc = ecryptfs_copy_up_encrypted_with_header( 321 page, crypt_stat); 322 if (rc) { 323 printk(KERN_ERR "%s: Error attempting " 324 "to copy the encrypted content " 325 "from the lower file whilst " 326 "inserting the metadata from " 327 "the xattr into the header; rc " 328 "= [%d]\n", __func__, rc); 329 ClearPageUptodate(page); 330 goto out; 331 } 332 SetPageUptodate(page); 333 } else { 334 rc = ecryptfs_read_lower_page_segment( 335 page, index, 0, PAGE_CACHE_SIZE, 336 mapping->host); 337 if (rc) { 338 printk(KERN_ERR "%s: Error reading " 339 "page; rc = [%d]\n", 340 __func__, rc); 341 ClearPageUptodate(page); 342 goto out; 343 } 344 SetPageUptodate(page); 345 } 346 } else { 347 rc = ecryptfs_decrypt_page(page); 348 if (rc) { 349 printk(KERN_ERR "%s: Error decrypting page " 350 "at index [%ld]; rc = [%d]\n", 351 __func__, page->index, rc); 352 ClearPageUptodate(page); 353 goto out; 354 } 355 SetPageUptodate(page); 356 } 357 } 358 prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT); 359 /* If creating a page or more of holes, zero them out via truncate. 360 * Note, this will increase i_size. */ 361 if (index != 0) { 362 if (prev_page_end_size > i_size_read(page->mapping->host)) { 363 rc = ecryptfs_truncate(file->f_path.dentry, 364 prev_page_end_size); 365 if (rc) { 366 printk(KERN_ERR "%s: Error on attempt to " 367 "truncate to (higher) offset [%lld];" 368 " rc = [%d]\n", __func__, 369 prev_page_end_size, rc); 370 goto out; 371 } 372 } 373 } 374 /* Writing to a new page, and creating a small hole from start 375 * of page? Zero it out. */ 376 if ((i_size_read(mapping->host) == prev_page_end_size) 377 && (pos != 0)) 378 zero_user(page, 0, PAGE_CACHE_SIZE); 379 out: 380 return rc; 381 } 382 383 /** 384 * ecryptfs_write_inode_size_to_header 385 * 386 * Writes the lower file size to the first 8 bytes of the header. 387 * 388 * Returns zero on success; non-zero on error. 389 */ 390 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) 391 { 392 char *file_size_virt; 393 int rc; 394 395 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); 396 if (!file_size_virt) { 397 rc = -ENOMEM; 398 goto out; 399 } 400 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); 401 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, 402 sizeof(u64)); 403 kfree(file_size_virt); 404 if (rc < 0) 405 printk(KERN_ERR "%s: Error writing file size to header; " 406 "rc = [%d]\n", __func__, rc); 407 else 408 rc = 0; 409 out: 410 return rc; 411 } 412 413 struct kmem_cache *ecryptfs_xattr_cache; 414 415 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) 416 { 417 ssize_t size; 418 void *xattr_virt; 419 struct dentry *lower_dentry = 420 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry; 421 struct inode *lower_inode = lower_dentry->d_inode; 422 int rc; 423 424 if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) { 425 printk(KERN_WARNING 426 "No support for setting xattr in lower filesystem\n"); 427 rc = -ENOSYS; 428 goto out; 429 } 430 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); 431 if (!xattr_virt) { 432 printk(KERN_ERR "Out of memory whilst attempting to write " 433 "inode size to xattr\n"); 434 rc = -ENOMEM; 435 goto out; 436 } 437 mutex_lock(&lower_inode->i_mutex); 438 size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 439 xattr_virt, PAGE_CACHE_SIZE); 440 if (size < 0) 441 size = 8; 442 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt); 443 rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 444 xattr_virt, size, 0); 445 mutex_unlock(&lower_inode->i_mutex); 446 if (rc) 447 printk(KERN_ERR "Error whilst attempting to write inode size " 448 "to lower file xattr; rc = [%d]\n", rc); 449 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); 450 out: 451 return rc; 452 } 453 454 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) 455 { 456 struct ecryptfs_crypt_stat *crypt_stat; 457 458 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 459 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); 460 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) 461 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); 462 else 463 return ecryptfs_write_inode_size_to_header(ecryptfs_inode); 464 } 465 466 /** 467 * ecryptfs_write_end 468 * @file: The eCryptfs file object 469 * @mapping: The eCryptfs object 470 * @pos: The file position 471 * @len: The length of the data (unused) 472 * @copied: The amount of data copied 473 * @page: The eCryptfs page 474 * @fsdata: The fsdata (unused) 475 * 476 * This is where we encrypt the data and pass the encrypted data to 477 * the lower filesystem. In OpenPGP-compatible mode, we operate on 478 * entire underlying packets. 479 */ 480 static int ecryptfs_write_end(struct file *file, 481 struct address_space *mapping, 482 loff_t pos, unsigned len, unsigned copied, 483 struct page *page, void *fsdata) 484 { 485 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 486 unsigned from = pos & (PAGE_CACHE_SIZE - 1); 487 unsigned to = from + copied; 488 struct inode *ecryptfs_inode = mapping->host; 489 struct ecryptfs_crypt_stat *crypt_stat = 490 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat; 491 int rc; 492 493 if (crypt_stat->flags & ECRYPTFS_NEW_FILE) { 494 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in " 495 "crypt_stat at memory location [%p]\n", crypt_stat); 496 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE); 497 } else 498 ecryptfs_printk(KERN_DEBUG, "Not a new file\n"); 499 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" 500 "(page w/ index = [0x%.16x], to = [%d])\n", index, to); 501 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 502 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, 503 to); 504 if (!rc) { 505 rc = copied; 506 fsstack_copy_inode_size(ecryptfs_inode, 507 ecryptfs_inode_to_lower(ecryptfs_inode)); 508 } 509 goto out; 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%.16x]\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%.16x])\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%.16x]\n", 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