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 rc = ecryptfs_encrypt_page(page); 66 if (rc) { 67 ecryptfs_printk(KERN_WARNING, "Error encrypting " 68 "page (upper index [0x%.16lx])\n", page->index); 69 ClearPageUptodate(page); 70 goto out; 71 } 72 SetPageUptodate(page); 73 unlock_page(page); 74 out: 75 return rc; 76 } 77 78 static void strip_xattr_flag(char *page_virt, 79 struct ecryptfs_crypt_stat *crypt_stat) 80 { 81 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 82 size_t written; 83 84 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR; 85 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat, 86 &written); 87 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR; 88 } 89 } 90 91 /** 92 * Header Extent: 93 * Octets 0-7: Unencrypted file size (big-endian) 94 * Octets 8-15: eCryptfs special marker 95 * Octets 16-19: Flags 96 * Octet 16: File format version number (between 0 and 255) 97 * Octets 17-18: Reserved 98 * Octet 19: Bit 1 (lsb): Reserved 99 * Bit 2: Encrypted? 100 * Bits 3-8: Reserved 101 * Octets 20-23: Header extent size (big-endian) 102 * Octets 24-25: Number of header extents at front of file 103 * (big-endian) 104 * Octet 26: Begin RFC 2440 authentication token packet set 105 */ 106 107 /** 108 * ecryptfs_copy_up_encrypted_with_header 109 * @page: Sort of a ``virtual'' representation of the encrypted lower 110 * file. The actual lower file does not have the metadata in 111 * the header. This is locked. 112 * @crypt_stat: The eCryptfs inode's cryptographic context 113 * 114 * The ``view'' is the version of the file that userspace winds up 115 * seeing, with the header information inserted. 116 */ 117 static int 118 ecryptfs_copy_up_encrypted_with_header(struct page *page, 119 struct ecryptfs_crypt_stat *crypt_stat) 120 { 121 loff_t extent_num_in_page = 0; 122 loff_t num_extents_per_page = (PAGE_CACHE_SIZE 123 / crypt_stat->extent_size); 124 int rc = 0; 125 126 while (extent_num_in_page < num_extents_per_page) { 127 loff_t view_extent_num = ((((loff_t)page->index) 128 * num_extents_per_page) 129 + extent_num_in_page); 130 size_t num_header_extents_at_front = 131 (crypt_stat->metadata_size / crypt_stat->extent_size); 132 133 if (view_extent_num < num_header_extents_at_front) { 134 /* This is a header extent */ 135 char *page_virt; 136 137 page_virt = kmap_atomic(page, KM_USER0); 138 memset(page_virt, 0, PAGE_CACHE_SIZE); 139 /* TODO: Support more than one header extent */ 140 if (view_extent_num == 0) { 141 size_t written; 142 143 rc = ecryptfs_read_xattr_region( 144 page_virt, page->mapping->host); 145 strip_xattr_flag(page_virt + 16, crypt_stat); 146 ecryptfs_write_header_metadata(page_virt + 20, 147 crypt_stat, 148 &written); 149 } 150 kunmap_atomic(page_virt, KM_USER0); 151 flush_dcache_page(page); 152 if (rc) { 153 printk(KERN_ERR "%s: Error reading xattr " 154 "region; rc = [%d]\n", __func__, rc); 155 goto out; 156 } 157 } else { 158 /* This is an encrypted data extent */ 159 loff_t lower_offset = 160 ((view_extent_num * crypt_stat->extent_size) 161 - crypt_stat->metadata_size); 162 163 rc = ecryptfs_read_lower_page_segment( 164 page, (lower_offset >> PAGE_CACHE_SHIFT), 165 (lower_offset & ~PAGE_CACHE_MASK), 166 crypt_stat->extent_size, page->mapping->host); 167 if (rc) { 168 printk(KERN_ERR "%s: Error attempting to read " 169 "extent at offset [%lld] in the lower " 170 "file; rc = [%d]\n", __func__, 171 lower_offset, rc); 172 goto out; 173 } 174 } 175 extent_num_in_page++; 176 } 177 out: 178 return rc; 179 } 180 181 /** 182 * ecryptfs_readpage 183 * @file: An eCryptfs file 184 * @page: Page from eCryptfs inode mapping into which to stick the read data 185 * 186 * Read in a page, decrypting if necessary. 187 * 188 * Returns zero on success; non-zero on error. 189 */ 190 static int ecryptfs_readpage(struct file *file, struct page *page) 191 { 192 struct ecryptfs_crypt_stat *crypt_stat = 193 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat; 194 int rc = 0; 195 196 if (!crypt_stat 197 || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED) 198 || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) { 199 ecryptfs_printk(KERN_DEBUG, 200 "Passing through unencrypted page\n"); 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 || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) { 300 rc = ecryptfs_read_lower_page_segment( 301 page, index, 0, PAGE_CACHE_SIZE, mapping->host); 302 if (rc) { 303 printk(KERN_ERR "%s: Error attemping to read " 304 "lower page segment; rc = [%d]\n", 305 __func__, rc); 306 ClearPageUptodate(page); 307 goto out; 308 } else 309 SetPageUptodate(page); 310 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 311 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 312 rc = ecryptfs_copy_up_encrypted_with_header( 313 page, crypt_stat); 314 if (rc) { 315 printk(KERN_ERR "%s: Error attempting " 316 "to copy the encrypted content " 317 "from the lower file whilst " 318 "inserting the metadata from " 319 "the xattr into the header; rc " 320 "= [%d]\n", __func__, rc); 321 ClearPageUptodate(page); 322 goto out; 323 } 324 SetPageUptodate(page); 325 } else { 326 rc = ecryptfs_read_lower_page_segment( 327 page, index, 0, PAGE_CACHE_SIZE, 328 mapping->host); 329 if (rc) { 330 printk(KERN_ERR "%s: Error reading " 331 "page; rc = [%d]\n", 332 __func__, rc); 333 ClearPageUptodate(page); 334 goto out; 335 } 336 SetPageUptodate(page); 337 } 338 } else { 339 if (prev_page_end_size 340 >= i_size_read(page->mapping->host)) { 341 zero_user(page, 0, PAGE_CACHE_SIZE); 342 } else { 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 } 353 SetPageUptodate(page); 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 return rc; 378 } 379 380 /** 381 * ecryptfs_write_inode_size_to_header 382 * 383 * Writes the lower file size to the first 8 bytes of the header. 384 * 385 * Returns zero on success; non-zero on error. 386 */ 387 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) 388 { 389 char *file_size_virt; 390 int rc; 391 392 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); 393 if (!file_size_virt) { 394 rc = -ENOMEM; 395 goto out; 396 } 397 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); 398 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, 399 sizeof(u64)); 400 kfree(file_size_virt); 401 if (rc < 0) 402 printk(KERN_ERR "%s: Error writing file size to header; " 403 "rc = [%d]\n", __func__, rc); 404 else 405 rc = 0; 406 out: 407 return rc; 408 } 409 410 struct kmem_cache *ecryptfs_xattr_cache; 411 412 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) 413 { 414 ssize_t size; 415 void *xattr_virt; 416 struct dentry *lower_dentry = 417 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry; 418 struct inode *lower_inode = lower_dentry->d_inode; 419 int rc; 420 421 if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) { 422 printk(KERN_WARNING 423 "No support for setting xattr in lower filesystem\n"); 424 rc = -ENOSYS; 425 goto out; 426 } 427 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); 428 if (!xattr_virt) { 429 printk(KERN_ERR "Out of memory whilst attempting to write " 430 "inode size to xattr\n"); 431 rc = -ENOMEM; 432 goto out; 433 } 434 mutex_lock(&lower_inode->i_mutex); 435 size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 436 xattr_virt, PAGE_CACHE_SIZE); 437 if (size < 0) 438 size = 8; 439 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt); 440 rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 441 xattr_virt, size, 0); 442 mutex_unlock(&lower_inode->i_mutex); 443 if (rc) 444 printk(KERN_ERR "Error whilst attempting to write inode size " 445 "to lower file xattr; rc = [%d]\n", rc); 446 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); 447 out: 448 return rc; 449 } 450 451 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) 452 { 453 struct ecryptfs_crypt_stat *crypt_stat; 454 455 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 456 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); 457 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) 458 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); 459 else 460 return ecryptfs_write_inode_size_to_header(ecryptfs_inode); 461 } 462 463 /** 464 * ecryptfs_write_end 465 * @file: The eCryptfs file object 466 * @mapping: The eCryptfs object 467 * @pos: The file position 468 * @len: The length of the data (unused) 469 * @copied: The amount of data copied 470 * @page: The eCryptfs page 471 * @fsdata: The fsdata (unused) 472 * 473 * This is where we encrypt the data and pass the encrypted data to 474 * the lower filesystem. In OpenPGP-compatible mode, we operate on 475 * entire underlying packets. 476 */ 477 static int ecryptfs_write_end(struct file *file, 478 struct address_space *mapping, 479 loff_t pos, unsigned len, unsigned copied, 480 struct page *page, void *fsdata) 481 { 482 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 483 unsigned from = pos & (PAGE_CACHE_SIZE - 1); 484 unsigned to = from + copied; 485 struct inode *ecryptfs_inode = mapping->host; 486 struct ecryptfs_crypt_stat *crypt_stat = 487 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 488 int rc; 489 490 if (crypt_stat->flags & ECRYPTFS_NEW_FILE) { 491 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in " 492 "crypt_stat at memory location [%p]\n", crypt_stat); 493 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE); 494 } else 495 ecryptfs_printk(KERN_DEBUG, "Not a new file\n"); 496 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" 497 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to); 498 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 499 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, 500 to); 501 if (!rc) { 502 rc = copied; 503 fsstack_copy_inode_size(ecryptfs_inode, 504 ecryptfs_inode_to_lower(ecryptfs_inode)); 505 } 506 goto out; 507 } 508 /* Fills in zeros if 'to' goes beyond inode size */ 509 rc = fill_zeros_to_end_of_page(page, to); 510 if (rc) { 511 ecryptfs_printk(KERN_WARNING, "Error attempting to fill " 512 "zeros in page with index = [0x%.16lx]\n", index); 513 goto out; 514 } 515 rc = ecryptfs_encrypt_page(page); 516 if (rc) { 517 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper " 518 "index [0x%.16lx])\n", index); 519 goto out; 520 } 521 if (pos + copied > i_size_read(ecryptfs_inode)) { 522 i_size_write(ecryptfs_inode, pos + copied); 523 ecryptfs_printk(KERN_DEBUG, "Expanded file size to " 524 "[0x%.16llx]\n", 525 (unsigned long long)i_size_read(ecryptfs_inode)); 526 } 527 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode); 528 if (rc) 529 printk(KERN_ERR "Error writing inode size to metadata; " 530 "rc = [%d]\n", rc); 531 else 532 rc = copied; 533 out: 534 unlock_page(page); 535 page_cache_release(page); 536 return rc; 537 } 538 539 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block) 540 { 541 int rc = 0; 542 struct inode *inode; 543 struct inode *lower_inode; 544 545 inode = (struct inode *)mapping->host; 546 lower_inode = ecryptfs_inode_to_lower(inode); 547 if (lower_inode->i_mapping->a_ops->bmap) 548 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping, 549 block); 550 return rc; 551 } 552 553 const struct address_space_operations ecryptfs_aops = { 554 .writepage = ecryptfs_writepage, 555 .readpage = ecryptfs_readpage, 556 .write_begin = ecryptfs_write_begin, 557 .write_end = ecryptfs_write_end, 558 .bmap = ecryptfs_bmap, 559 }; 560