1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /** 3 * eCryptfs: Linux filesystem encryption layer 4 * This is where eCryptfs coordinates the symmetric encryption and 5 * decryption of the file data as it passes between the lower 6 * encrypted file and the upper decrypted file. 7 * 8 * Copyright (C) 1997-2003 Erez Zadok 9 * Copyright (C) 2001-2003 Stony Brook University 10 * Copyright (C) 2004-2007 International Business Machines Corp. 11 * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com> 12 */ 13 14 #include <linux/pagemap.h> 15 #include <linux/writeback.h> 16 #include <linux/page-flags.h> 17 #include <linux/mount.h> 18 #include <linux/file.h> 19 #include <linux/scatterlist.h> 20 #include <linux/slab.h> 21 #include <linux/xattr.h> 22 #include <asm/unaligned.h> 23 #include "ecryptfs_kernel.h" 24 25 /** 26 * ecryptfs_get_locked_page 27 * 28 * Get one page from cache or lower f/s, return error otherwise. 29 * 30 * Returns locked and up-to-date page (if ok), with increased 31 * refcnt. 32 */ 33 struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index) 34 { 35 struct page *page = read_mapping_page(inode->i_mapping, index, NULL); 36 if (!IS_ERR(page)) 37 lock_page(page); 38 return page; 39 } 40 41 /** 42 * ecryptfs_writepage 43 * @page: Page that is locked before this call is made 44 * 45 * Returns zero on success; non-zero otherwise 46 * 47 * This is where we encrypt the data and pass the encrypted data to 48 * the lower filesystem. In OpenPGP-compatible mode, we operate on 49 * entire underlying packets. 50 */ 51 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc) 52 { 53 int rc; 54 55 rc = ecryptfs_encrypt_page(page); 56 if (rc) { 57 ecryptfs_printk(KERN_WARNING, "Error encrypting " 58 "page (upper index [0x%.16lx])\n", page->index); 59 ClearPageUptodate(page); 60 goto out; 61 } 62 SetPageUptodate(page); 63 out: 64 unlock_page(page); 65 return rc; 66 } 67 68 static void strip_xattr_flag(char *page_virt, 69 struct ecryptfs_crypt_stat *crypt_stat) 70 { 71 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 72 size_t written; 73 74 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR; 75 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat, 76 &written); 77 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR; 78 } 79 } 80 81 /** 82 * Header Extent: 83 * Octets 0-7: Unencrypted file size (big-endian) 84 * Octets 8-15: eCryptfs special marker 85 * Octets 16-19: Flags 86 * Octet 16: File format version number (between 0 and 255) 87 * Octets 17-18: Reserved 88 * Octet 19: Bit 1 (lsb): Reserved 89 * Bit 2: Encrypted? 90 * Bits 3-8: Reserved 91 * Octets 20-23: Header extent size (big-endian) 92 * Octets 24-25: Number of header extents at front of file 93 * (big-endian) 94 * Octet 26: Begin RFC 2440 authentication token packet set 95 */ 96 97 /** 98 * ecryptfs_copy_up_encrypted_with_header 99 * @page: Sort of a ``virtual'' representation of the encrypted lower 100 * file. The actual lower file does not have the metadata in 101 * the header. This is locked. 102 * @crypt_stat: The eCryptfs inode's cryptographic context 103 * 104 * The ``view'' is the version of the file that userspace winds up 105 * seeing, with the header information inserted. 106 */ 107 static int 108 ecryptfs_copy_up_encrypted_with_header(struct page *page, 109 struct ecryptfs_crypt_stat *crypt_stat) 110 { 111 loff_t extent_num_in_page = 0; 112 loff_t num_extents_per_page = (PAGE_SIZE 113 / crypt_stat->extent_size); 114 int rc = 0; 115 116 while (extent_num_in_page < num_extents_per_page) { 117 loff_t view_extent_num = ((((loff_t)page->index) 118 * num_extents_per_page) 119 + extent_num_in_page); 120 size_t num_header_extents_at_front = 121 (crypt_stat->metadata_size / crypt_stat->extent_size); 122 123 if (view_extent_num < num_header_extents_at_front) { 124 /* This is a header extent */ 125 char *page_virt; 126 127 page_virt = kmap_atomic(page); 128 memset(page_virt, 0, PAGE_SIZE); 129 /* TODO: Support more than one header extent */ 130 if (view_extent_num == 0) { 131 size_t written; 132 133 rc = ecryptfs_read_xattr_region( 134 page_virt, page->mapping->host); 135 strip_xattr_flag(page_virt + 16, crypt_stat); 136 ecryptfs_write_header_metadata(page_virt + 20, 137 crypt_stat, 138 &written); 139 } 140 kunmap_atomic(page_virt); 141 flush_dcache_page(page); 142 if (rc) { 143 printk(KERN_ERR "%s: Error reading xattr " 144 "region; rc = [%d]\n", __func__, rc); 145 goto out; 146 } 147 } else { 148 /* This is an encrypted data extent */ 149 loff_t lower_offset = 150 ((view_extent_num * crypt_stat->extent_size) 151 - crypt_stat->metadata_size); 152 153 rc = ecryptfs_read_lower_page_segment( 154 page, (lower_offset >> PAGE_SHIFT), 155 (lower_offset & ~PAGE_MASK), 156 crypt_stat->extent_size, page->mapping->host); 157 if (rc) { 158 printk(KERN_ERR "%s: Error attempting to read " 159 "extent at offset [%lld] in the lower " 160 "file; rc = [%d]\n", __func__, 161 lower_offset, rc); 162 goto out; 163 } 164 } 165 extent_num_in_page++; 166 } 167 out: 168 return rc; 169 } 170 171 /** 172 * ecryptfs_readpage 173 * @file: An eCryptfs file 174 * @page: Page from eCryptfs inode mapping into which to stick the read data 175 * 176 * Read in a page, decrypting if necessary. 177 * 178 * Returns zero on success; non-zero on error. 179 */ 180 static int ecryptfs_readpage(struct file *file, struct page *page) 181 { 182 struct ecryptfs_crypt_stat *crypt_stat = 183 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat; 184 int rc = 0; 185 186 if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 187 rc = ecryptfs_read_lower_page_segment(page, page->index, 0, 188 PAGE_SIZE, 189 page->mapping->host); 190 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 191 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 192 rc = ecryptfs_copy_up_encrypted_with_header(page, 193 crypt_stat); 194 if (rc) { 195 printk(KERN_ERR "%s: Error attempting to copy " 196 "the encrypted content from the lower " 197 "file whilst inserting the metadata " 198 "from the xattr into the header; rc = " 199 "[%d]\n", __func__, rc); 200 goto out; 201 } 202 203 } else { 204 rc = ecryptfs_read_lower_page_segment( 205 page, page->index, 0, PAGE_SIZE, 206 page->mapping->host); 207 if (rc) { 208 printk(KERN_ERR "Error reading page; rc = " 209 "[%d]\n", rc); 210 goto out; 211 } 212 } 213 } else { 214 rc = ecryptfs_decrypt_page(page); 215 if (rc) { 216 ecryptfs_printk(KERN_ERR, "Error decrypting page; " 217 "rc = [%d]\n", rc); 218 goto out; 219 } 220 } 221 out: 222 if (rc) 223 ClearPageUptodate(page); 224 else 225 SetPageUptodate(page); 226 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n", 227 page->index); 228 unlock_page(page); 229 return rc; 230 } 231 232 /** 233 * Called with lower inode mutex held. 234 */ 235 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to) 236 { 237 struct inode *inode = page->mapping->host; 238 int end_byte_in_page; 239 240 if ((i_size_read(inode) / PAGE_SIZE) != page->index) 241 goto out; 242 end_byte_in_page = i_size_read(inode) % PAGE_SIZE; 243 if (to > end_byte_in_page) 244 end_byte_in_page = to; 245 zero_user_segment(page, end_byte_in_page, PAGE_SIZE); 246 out: 247 return 0; 248 } 249 250 /** 251 * ecryptfs_write_begin 252 * @file: The eCryptfs file 253 * @mapping: The eCryptfs object 254 * @pos: The file offset at which to start writing 255 * @len: Length of the write 256 * @flags: Various flags 257 * @pagep: Pointer to return the page 258 * @fsdata: Pointer to return fs data (unused) 259 * 260 * This function must zero any hole we create 261 * 262 * Returns zero on success; non-zero otherwise 263 */ 264 static int ecryptfs_write_begin(struct file *file, 265 struct address_space *mapping, 266 loff_t pos, unsigned len, unsigned flags, 267 struct page **pagep, void **fsdata) 268 { 269 pgoff_t index = pos >> PAGE_SHIFT; 270 struct page *page; 271 loff_t prev_page_end_size; 272 int rc = 0; 273 274 page = grab_cache_page_write_begin(mapping, index, flags); 275 if (!page) 276 return -ENOMEM; 277 *pagep = page; 278 279 prev_page_end_size = ((loff_t)index << PAGE_SHIFT); 280 if (!PageUptodate(page)) { 281 struct ecryptfs_crypt_stat *crypt_stat = 282 &ecryptfs_inode_to_private(mapping->host)->crypt_stat; 283 284 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 285 rc = ecryptfs_read_lower_page_segment( 286 page, index, 0, PAGE_SIZE, mapping->host); 287 if (rc) { 288 printk(KERN_ERR "%s: Error attempting to read " 289 "lower page segment; rc = [%d]\n", 290 __func__, rc); 291 ClearPageUptodate(page); 292 goto out; 293 } else 294 SetPageUptodate(page); 295 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 296 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 297 rc = ecryptfs_copy_up_encrypted_with_header( 298 page, crypt_stat); 299 if (rc) { 300 printk(KERN_ERR "%s: Error attempting " 301 "to copy the encrypted content " 302 "from the lower file whilst " 303 "inserting the metadata from " 304 "the xattr into the header; rc " 305 "= [%d]\n", __func__, rc); 306 ClearPageUptodate(page); 307 goto out; 308 } 309 SetPageUptodate(page); 310 } else { 311 rc = ecryptfs_read_lower_page_segment( 312 page, index, 0, PAGE_SIZE, 313 mapping->host); 314 if (rc) { 315 printk(KERN_ERR "%s: Error reading " 316 "page; rc = [%d]\n", 317 __func__, rc); 318 ClearPageUptodate(page); 319 goto out; 320 } 321 SetPageUptodate(page); 322 } 323 } else { 324 if (prev_page_end_size 325 >= i_size_read(page->mapping->host)) { 326 zero_user(page, 0, PAGE_SIZE); 327 SetPageUptodate(page); 328 } else if (len < PAGE_SIZE) { 329 rc = ecryptfs_decrypt_page(page); 330 if (rc) { 331 printk(KERN_ERR "%s: Error decrypting " 332 "page at index [%ld]; " 333 "rc = [%d]\n", 334 __func__, page->index, rc); 335 ClearPageUptodate(page); 336 goto out; 337 } 338 SetPageUptodate(page); 339 } 340 } 341 } 342 /* If creating a page or more of holes, zero them out via truncate. 343 * Note, this will increase i_size. */ 344 if (index != 0) { 345 if (prev_page_end_size > i_size_read(page->mapping->host)) { 346 rc = ecryptfs_truncate(file->f_path.dentry, 347 prev_page_end_size); 348 if (rc) { 349 printk(KERN_ERR "%s: Error on attempt to " 350 "truncate to (higher) offset [%lld];" 351 " rc = [%d]\n", __func__, 352 prev_page_end_size, rc); 353 goto out; 354 } 355 } 356 } 357 /* Writing to a new page, and creating a small hole from start 358 * of page? Zero it out. */ 359 if ((i_size_read(mapping->host) == prev_page_end_size) 360 && (pos != 0)) 361 zero_user(page, 0, PAGE_SIZE); 362 out: 363 if (unlikely(rc)) { 364 unlock_page(page); 365 put_page(page); 366 *pagep = NULL; 367 } 368 return rc; 369 } 370 371 /** 372 * ecryptfs_write_inode_size_to_header 373 * 374 * Writes the lower file size to the first 8 bytes of the header. 375 * 376 * Returns zero on success; non-zero on error. 377 */ 378 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) 379 { 380 char *file_size_virt; 381 int rc; 382 383 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); 384 if (!file_size_virt) { 385 rc = -ENOMEM; 386 goto out; 387 } 388 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); 389 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, 390 sizeof(u64)); 391 kfree(file_size_virt); 392 if (rc < 0) 393 printk(KERN_ERR "%s: Error writing file size to header; " 394 "rc = [%d]\n", __func__, rc); 395 else 396 rc = 0; 397 out: 398 return rc; 399 } 400 401 struct kmem_cache *ecryptfs_xattr_cache; 402 403 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) 404 { 405 ssize_t size; 406 void *xattr_virt; 407 struct dentry *lower_dentry = 408 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry; 409 struct inode *lower_inode = d_inode(lower_dentry); 410 int rc; 411 412 if (!(lower_inode->i_opflags & IOP_XATTR)) { 413 printk(KERN_WARNING 414 "No support for setting xattr in lower filesystem\n"); 415 rc = -ENOSYS; 416 goto out; 417 } 418 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); 419 if (!xattr_virt) { 420 rc = -ENOMEM; 421 goto out; 422 } 423 inode_lock(lower_inode); 424 size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME, 425 xattr_virt, PAGE_SIZE); 426 if (size < 0) 427 size = 8; 428 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt); 429 rc = __vfs_setxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME, 430 xattr_virt, size, 0); 431 inode_unlock(lower_inode); 432 if (rc) 433 printk(KERN_ERR "Error whilst attempting to write inode size " 434 "to lower file xattr; rc = [%d]\n", rc); 435 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); 436 out: 437 return rc; 438 } 439 440 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) 441 { 442 struct ecryptfs_crypt_stat *crypt_stat; 443 444 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 445 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); 446 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) 447 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); 448 else 449 return ecryptfs_write_inode_size_to_header(ecryptfs_inode); 450 } 451 452 /** 453 * ecryptfs_write_end 454 * @file: The eCryptfs file object 455 * @mapping: The eCryptfs object 456 * @pos: The file position 457 * @len: The length of the data (unused) 458 * @copied: The amount of data copied 459 * @page: The eCryptfs page 460 * @fsdata: The fsdata (unused) 461 */ 462 static int ecryptfs_write_end(struct file *file, 463 struct address_space *mapping, 464 loff_t pos, unsigned len, unsigned copied, 465 struct page *page, void *fsdata) 466 { 467 pgoff_t index = pos >> PAGE_SHIFT; 468 unsigned from = pos & (PAGE_SIZE - 1); 469 unsigned to = from + copied; 470 struct inode *ecryptfs_inode = mapping->host; 471 struct ecryptfs_crypt_stat *crypt_stat = 472 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 473 int rc; 474 475 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" 476 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to); 477 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 478 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, 479 to); 480 if (!rc) { 481 rc = copied; 482 fsstack_copy_inode_size(ecryptfs_inode, 483 ecryptfs_inode_to_lower(ecryptfs_inode)); 484 } 485 goto out; 486 } 487 if (!PageUptodate(page)) { 488 if (copied < PAGE_SIZE) { 489 rc = 0; 490 goto out; 491 } 492 SetPageUptodate(page); 493 } 494 /* Fills in zeros if 'to' goes beyond inode size */ 495 rc = fill_zeros_to_end_of_page(page, to); 496 if (rc) { 497 ecryptfs_printk(KERN_WARNING, "Error attempting to fill " 498 "zeros in page with index = [0x%.16lx]\n", index); 499 goto out; 500 } 501 rc = ecryptfs_encrypt_page(page); 502 if (rc) { 503 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper " 504 "index [0x%.16lx])\n", index); 505 goto out; 506 } 507 if (pos + copied > i_size_read(ecryptfs_inode)) { 508 i_size_write(ecryptfs_inode, pos + copied); 509 ecryptfs_printk(KERN_DEBUG, "Expanded file size to " 510 "[0x%.16llx]\n", 511 (unsigned long long)i_size_read(ecryptfs_inode)); 512 } 513 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode); 514 if (rc) 515 printk(KERN_ERR "Error writing inode size to metadata; " 516 "rc = [%d]\n", rc); 517 else 518 rc = copied; 519 out: 520 unlock_page(page); 521 put_page(page); 522 return rc; 523 } 524 525 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block) 526 { 527 struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host); 528 int ret = bmap(lower_inode, &block); 529 530 if (ret) 531 return 0; 532 return block; 533 } 534 535 const struct address_space_operations ecryptfs_aops = { 536 .writepage = ecryptfs_writepage, 537 .readpage = ecryptfs_readpage, 538 .write_begin = ecryptfs_write_begin, 539 .write_end = ecryptfs_write_end, 540 .bmap = ecryptfs_bmap, 541 }; 542