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%.16x])\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%.16x]\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 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 || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) { 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 rc = ecryptfs_decrypt_page(page); 339 if (rc) { 340 printk(KERN_ERR "%s: Error decrypting page " 341 "at index [%ld]; rc = [%d]\n", 342 __func__, page->index, rc); 343 ClearPageUptodate(page); 344 goto out; 345 } 346 SetPageUptodate(page); 347 } 348 } 349 prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT); 350 /* If creating a page or more of holes, zero them out via truncate. 351 * Note, this will increase i_size. */ 352 if (index != 0) { 353 if (prev_page_end_size > i_size_read(page->mapping->host)) { 354 rc = ecryptfs_truncate(file->f_path.dentry, 355 prev_page_end_size); 356 if (rc) { 357 printk(KERN_ERR "%s: Error on attempt to " 358 "truncate to (higher) offset [%lld];" 359 " rc = [%d]\n", __func__, 360 prev_page_end_size, rc); 361 goto out; 362 } 363 } 364 } 365 /* Writing to a new page, and creating a small hole from start 366 * of page? Zero it out. */ 367 if ((i_size_read(mapping->host) == prev_page_end_size) 368 && (pos != 0)) 369 zero_user(page, 0, PAGE_CACHE_SIZE); 370 out: 371 return rc; 372 } 373 374 /** 375 * ecryptfs_write_inode_size_to_header 376 * 377 * Writes the lower file size to the first 8 bytes of the header. 378 * 379 * Returns zero on success; non-zero on error. 380 */ 381 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) 382 { 383 char *file_size_virt; 384 int rc; 385 386 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); 387 if (!file_size_virt) { 388 rc = -ENOMEM; 389 goto out; 390 } 391 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); 392 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, 393 sizeof(u64)); 394 kfree(file_size_virt); 395 if (rc < 0) 396 printk(KERN_ERR "%s: Error writing file size to header; " 397 "rc = [%d]\n", __func__, rc); 398 else 399 rc = 0; 400 out: 401 return rc; 402 } 403 404 struct kmem_cache *ecryptfs_xattr_cache; 405 406 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) 407 { 408 ssize_t size; 409 void *xattr_virt; 410 struct dentry *lower_dentry = 411 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry; 412 struct inode *lower_inode = lower_dentry->d_inode; 413 int rc; 414 415 if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) { 416 printk(KERN_WARNING 417 "No support for setting xattr in lower filesystem\n"); 418 rc = -ENOSYS; 419 goto out; 420 } 421 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); 422 if (!xattr_virt) { 423 printk(KERN_ERR "Out of memory whilst attempting to write " 424 "inode size to xattr\n"); 425 rc = -ENOMEM; 426 goto out; 427 } 428 mutex_lock(&lower_inode->i_mutex); 429 size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 430 xattr_virt, PAGE_CACHE_SIZE); 431 if (size < 0) 432 size = 8; 433 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt); 434 rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME, 435 xattr_virt, size, 0); 436 mutex_unlock(&lower_inode->i_mutex); 437 if (rc) 438 printk(KERN_ERR "Error whilst attempting to write inode size " 439 "to lower file xattr; rc = [%d]\n", rc); 440 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); 441 out: 442 return rc; 443 } 444 445 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) 446 { 447 struct ecryptfs_crypt_stat *crypt_stat; 448 449 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 450 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); 451 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) 452 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); 453 else 454 return ecryptfs_write_inode_size_to_header(ecryptfs_inode); 455 } 456 457 /** 458 * ecryptfs_write_end 459 * @file: The eCryptfs file object 460 * @mapping: The eCryptfs object 461 * @pos: The file position 462 * @len: The length of the data (unused) 463 * @copied: The amount of data copied 464 * @page: The eCryptfs page 465 * @fsdata: The fsdata (unused) 466 * 467 * This is where we encrypt the data and pass the encrypted data to 468 * the lower filesystem. In OpenPGP-compatible mode, we operate on 469 * entire underlying packets. 470 */ 471 static int ecryptfs_write_end(struct file *file, 472 struct address_space *mapping, 473 loff_t pos, unsigned len, unsigned copied, 474 struct page *page, void *fsdata) 475 { 476 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 477 unsigned from = pos & (PAGE_CACHE_SIZE - 1); 478 unsigned to = from + copied; 479 struct inode *ecryptfs_inode = mapping->host; 480 struct ecryptfs_crypt_stat *crypt_stat = 481 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 482 int rc; 483 484 if (crypt_stat->flags & ECRYPTFS_NEW_FILE) { 485 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in " 486 "crypt_stat at memory location [%p]\n", crypt_stat); 487 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE); 488 } else 489 ecryptfs_printk(KERN_DEBUG, "Not a new file\n"); 490 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" 491 "(page w/ index = [0x%.16x], to = [%d])\n", index, to); 492 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 493 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, 494 to); 495 if (!rc) { 496 rc = copied; 497 fsstack_copy_inode_size(ecryptfs_inode, 498 ecryptfs_inode_to_lower(ecryptfs_inode)); 499 } 500 goto out; 501 } 502 /* Fills in zeros if 'to' goes beyond inode size */ 503 rc = fill_zeros_to_end_of_page(page, to); 504 if (rc) { 505 ecryptfs_printk(KERN_WARNING, "Error attempting to fill " 506 "zeros in page with index = [0x%.16x]\n", index); 507 goto out; 508 } 509 rc = ecryptfs_encrypt_page(page); 510 if (rc) { 511 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper " 512 "index [0x%.16x])\n", index); 513 goto out; 514 } 515 if (pos + copied > i_size_read(ecryptfs_inode)) { 516 i_size_write(ecryptfs_inode, pos + copied); 517 ecryptfs_printk(KERN_DEBUG, "Expanded file size to " 518 "[0x%.16x]\n", i_size_read(ecryptfs_inode)); 519 } 520 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode); 521 if (rc) 522 printk(KERN_ERR "Error writing inode size to metadata; " 523 "rc = [%d]\n", rc); 524 else 525 rc = copied; 526 out: 527 unlock_page(page); 528 page_cache_release(page); 529 return rc; 530 } 531 532 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block) 533 { 534 int rc = 0; 535 struct inode *inode; 536 struct inode *lower_inode; 537 538 inode = (struct inode *)mapping->host; 539 lower_inode = ecryptfs_inode_to_lower(inode); 540 if (lower_inode->i_mapping->a_ops->bmap) 541 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping, 542 block); 543 return rc; 544 } 545 546 const struct address_space_operations ecryptfs_aops = { 547 .writepage = ecryptfs_writepage, 548 .readpage = ecryptfs_readpage, 549 .write_begin = ecryptfs_write_begin, 550 .write_end = ecryptfs_write_end, 551 .bmap = ecryptfs_bmap, 552 }; 553