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 * @wbc: Write-back control structure 45 * 46 * Returns zero on success; non-zero otherwise 47 * 48 * This is where we encrypt the data and pass the encrypted data to 49 * the lower filesystem. In OpenPGP-compatible mode, we operate on 50 * entire underlying packets. 51 */ 52 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc) 53 { 54 int rc; 55 56 rc = ecryptfs_encrypt_page(page); 57 if (rc) { 58 ecryptfs_printk(KERN_WARNING, "Error encrypting " 59 "page (upper index [0x%.16lx])\n", page->index); 60 ClearPageUptodate(page); 61 goto out; 62 } 63 SetPageUptodate(page); 64 out: 65 unlock_page(page); 66 return rc; 67 } 68 69 static void strip_xattr_flag(char *page_virt, 70 struct ecryptfs_crypt_stat *crypt_stat) 71 { 72 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 73 size_t written; 74 75 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR; 76 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat, 77 &written); 78 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR; 79 } 80 } 81 82 /* 83 * Header Extent: 84 * Octets 0-7: Unencrypted file size (big-endian) 85 * Octets 8-15: eCryptfs special marker 86 * Octets 16-19: Flags 87 * Octet 16: File format version number (between 0 and 255) 88 * Octets 17-18: Reserved 89 * Octet 19: Bit 1 (lsb): Reserved 90 * Bit 2: Encrypted? 91 * Bits 3-8: Reserved 92 * Octets 20-23: Header extent size (big-endian) 93 * Octets 24-25: Number of header extents at front of file 94 * (big-endian) 95 * Octet 26: Begin RFC 2440 authentication token packet set 96 */ 97 98 /** 99 * ecryptfs_copy_up_encrypted_with_header 100 * @page: Sort of a ``virtual'' representation of the encrypted lower 101 * file. The actual lower file does not have the metadata in 102 * the header. This is locked. 103 * @crypt_stat: The eCryptfs inode's cryptographic context 104 * 105 * The ``view'' is the version of the file that userspace winds up 106 * seeing, with the header information inserted. 107 */ 108 static int 109 ecryptfs_copy_up_encrypted_with_header(struct page *page, 110 struct ecryptfs_crypt_stat *crypt_stat) 111 { 112 loff_t extent_num_in_page = 0; 113 loff_t num_extents_per_page = (PAGE_SIZE 114 / crypt_stat->extent_size); 115 int rc = 0; 116 117 while (extent_num_in_page < num_extents_per_page) { 118 loff_t view_extent_num = ((((loff_t)page->index) 119 * num_extents_per_page) 120 + extent_num_in_page); 121 size_t num_header_extents_at_front = 122 (crypt_stat->metadata_size / crypt_stat->extent_size); 123 124 if (view_extent_num < num_header_extents_at_front) { 125 /* This is a header extent */ 126 char *page_virt; 127 128 page_virt = kmap_atomic(page); 129 memset(page_virt, 0, PAGE_SIZE); 130 /* TODO: Support more than one header extent */ 131 if (view_extent_num == 0) { 132 size_t written; 133 134 rc = ecryptfs_read_xattr_region( 135 page_virt, page->mapping->host); 136 strip_xattr_flag(page_virt + 16, crypt_stat); 137 ecryptfs_write_header_metadata(page_virt + 20, 138 crypt_stat, 139 &written); 140 } 141 kunmap_atomic(page_virt); 142 flush_dcache_page(page); 143 if (rc) { 144 printk(KERN_ERR "%s: Error reading xattr " 145 "region; rc = [%d]\n", __func__, rc); 146 goto out; 147 } 148 } else { 149 /* This is an encrypted data extent */ 150 loff_t lower_offset = 151 ((view_extent_num * crypt_stat->extent_size) 152 - crypt_stat->metadata_size); 153 154 rc = ecryptfs_read_lower_page_segment( 155 page, (lower_offset >> PAGE_SHIFT), 156 (lower_offset & ~PAGE_MASK), 157 crypt_stat->extent_size, page->mapping->host); 158 if (rc) { 159 printk(KERN_ERR "%s: Error attempting to read " 160 "extent at offset [%lld] in the lower " 161 "file; rc = [%d]\n", __func__, 162 lower_offset, rc); 163 goto out; 164 } 165 } 166 extent_num_in_page++; 167 } 168 out: 169 return rc; 170 } 171 172 /** 173 * ecryptfs_read_folio 174 * @file: An eCryptfs file 175 * @folio: Folio from eCryptfs inode mapping into which to stick the read data 176 * 177 * Read in a folio, decrypting if necessary. 178 * 179 * Returns zero on success; non-zero on error. 180 */ 181 static int ecryptfs_read_folio(struct file *file, struct folio *folio) 182 { 183 struct page *page = &folio->page; 184 struct ecryptfs_crypt_stat *crypt_stat = 185 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat; 186 int rc = 0; 187 188 if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 189 rc = ecryptfs_read_lower_page_segment(page, page->index, 0, 190 PAGE_SIZE, 191 page->mapping->host); 192 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 193 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 194 rc = ecryptfs_copy_up_encrypted_with_header(page, 195 crypt_stat); 196 if (rc) { 197 printk(KERN_ERR "%s: Error attempting to copy " 198 "the encrypted content from the lower " 199 "file whilst inserting the metadata " 200 "from the xattr into the header; rc = " 201 "[%d]\n", __func__, rc); 202 goto out; 203 } 204 205 } else { 206 rc = ecryptfs_read_lower_page_segment( 207 page, page->index, 0, PAGE_SIZE, 208 page->mapping->host); 209 if (rc) { 210 printk(KERN_ERR "Error reading page; rc = " 211 "[%d]\n", rc); 212 goto out; 213 } 214 } 215 } else { 216 rc = ecryptfs_decrypt_page(page); 217 if (rc) { 218 ecryptfs_printk(KERN_ERR, "Error decrypting page; " 219 "rc = [%d]\n", rc); 220 goto out; 221 } 222 } 223 out: 224 if (rc) 225 ClearPageUptodate(page); 226 else 227 SetPageUptodate(page); 228 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n", 229 page->index); 230 unlock_page(page); 231 return rc; 232 } 233 234 /* 235 * Called with lower inode mutex held. 236 */ 237 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to) 238 { 239 struct inode *inode = page->mapping->host; 240 int end_byte_in_page; 241 242 if ((i_size_read(inode) / PAGE_SIZE) != page->index) 243 goto out; 244 end_byte_in_page = i_size_read(inode) % PAGE_SIZE; 245 if (to > end_byte_in_page) 246 end_byte_in_page = to; 247 zero_user_segment(page, end_byte_in_page, PAGE_SIZE); 248 out: 249 return 0; 250 } 251 252 /** 253 * ecryptfs_write_begin 254 * @file: The eCryptfs file 255 * @mapping: The eCryptfs object 256 * @pos: The file offset at which to start writing 257 * @len: Length of the write 258 * @flags: Various flags 259 * @pagep: Pointer to return the page 260 * @fsdata: Pointer to return fs data (unused) 261 * 262 * This function must zero any hole we create 263 * 264 * Returns zero on success; non-zero otherwise 265 */ 266 static int ecryptfs_write_begin(struct file *file, 267 struct address_space *mapping, 268 loff_t pos, unsigned len, 269 struct page **pagep, void **fsdata) 270 { 271 pgoff_t index = pos >> PAGE_SHIFT; 272 struct page *page; 273 loff_t prev_page_end_size; 274 int rc = 0; 275 276 page = grab_cache_page_write_begin(mapping, index); 277 if (!page) 278 return -ENOMEM; 279 *pagep = page; 280 281 prev_page_end_size = ((loff_t)index << PAGE_SHIFT); 282 if (!PageUptodate(page)) { 283 struct ecryptfs_crypt_stat *crypt_stat = 284 &ecryptfs_inode_to_private(mapping->host)->crypt_stat; 285 286 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 287 rc = ecryptfs_read_lower_page_segment( 288 page, index, 0, PAGE_SIZE, mapping->host); 289 if (rc) { 290 printk(KERN_ERR "%s: Error attempting to read " 291 "lower page segment; rc = [%d]\n", 292 __func__, rc); 293 ClearPageUptodate(page); 294 goto out; 295 } else 296 SetPageUptodate(page); 297 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 298 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 299 rc = ecryptfs_copy_up_encrypted_with_header( 300 page, crypt_stat); 301 if (rc) { 302 printk(KERN_ERR "%s: Error attempting " 303 "to copy the encrypted content " 304 "from the lower file whilst " 305 "inserting the metadata from " 306 "the xattr into the header; rc " 307 "= [%d]\n", __func__, rc); 308 ClearPageUptodate(page); 309 goto out; 310 } 311 SetPageUptodate(page); 312 } else { 313 rc = ecryptfs_read_lower_page_segment( 314 page, index, 0, PAGE_SIZE, 315 mapping->host); 316 if (rc) { 317 printk(KERN_ERR "%s: Error reading " 318 "page; rc = [%d]\n", 319 __func__, rc); 320 ClearPageUptodate(page); 321 goto out; 322 } 323 SetPageUptodate(page); 324 } 325 } else { 326 if (prev_page_end_size 327 >= i_size_read(page->mapping->host)) { 328 zero_user(page, 0, PAGE_SIZE); 329 SetPageUptodate(page); 330 } else if (len < PAGE_SIZE) { 331 rc = ecryptfs_decrypt_page(page); 332 if (rc) { 333 printk(KERN_ERR "%s: Error decrypting " 334 "page at index [%ld]; " 335 "rc = [%d]\n", 336 __func__, page->index, rc); 337 ClearPageUptodate(page); 338 goto out; 339 } 340 SetPageUptodate(page); 341 } 342 } 343 } 344 /* If creating a page or more of holes, zero them out via truncate. 345 * Note, this will increase i_size. */ 346 if (index != 0) { 347 if (prev_page_end_size > i_size_read(page->mapping->host)) { 348 rc = ecryptfs_truncate(file->f_path.dentry, 349 prev_page_end_size); 350 if (rc) { 351 printk(KERN_ERR "%s: Error on attempt to " 352 "truncate to (higher) offset [%lld];" 353 " rc = [%d]\n", __func__, 354 prev_page_end_size, rc); 355 goto out; 356 } 357 } 358 } 359 /* Writing to a new page, and creating a small hole from start 360 * of page? Zero it out. */ 361 if ((i_size_read(mapping->host) == prev_page_end_size) 362 && (pos != 0)) 363 zero_user(page, 0, PAGE_SIZE); 364 out: 365 if (unlikely(rc)) { 366 unlock_page(page); 367 put_page(page); 368 *pagep = NULL; 369 } 370 return rc; 371 } 372 373 /* 374 * ecryptfs_write_inode_size_to_header 375 * 376 * Writes the lower file size to the first 8 bytes of the header. 377 * 378 * Returns zero on success; non-zero on error. 379 */ 380 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) 381 { 382 char *file_size_virt; 383 int rc; 384 385 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); 386 if (!file_size_virt) { 387 rc = -ENOMEM; 388 goto out; 389 } 390 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); 391 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, 392 sizeof(u64)); 393 kfree(file_size_virt); 394 if (rc < 0) 395 printk(KERN_ERR "%s: Error writing file size to header; " 396 "rc = [%d]\n", __func__, rc); 397 else 398 rc = 0; 399 out: 400 return rc; 401 } 402 403 struct kmem_cache *ecryptfs_xattr_cache; 404 405 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) 406 { 407 ssize_t size; 408 void *xattr_virt; 409 struct dentry *lower_dentry = 410 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry; 411 struct inode *lower_inode = d_inode(lower_dentry); 412 int rc; 413 414 if (!(lower_inode->i_opflags & IOP_XATTR)) { 415 printk(KERN_WARNING 416 "No support for setting xattr in lower filesystem\n"); 417 rc = -ENOSYS; 418 goto out; 419 } 420 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); 421 if (!xattr_virt) { 422 rc = -ENOMEM; 423 goto out; 424 } 425 inode_lock(lower_inode); 426 size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME, 427 xattr_virt, PAGE_SIZE); 428 if (size < 0) 429 size = 8; 430 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt); 431 rc = __vfs_setxattr(&init_user_ns, lower_dentry, lower_inode, 432 ECRYPTFS_XATTR_NAME, xattr_virt, size, 0); 433 inode_unlock(lower_inode); 434 if (rc) 435 printk(KERN_ERR "Error whilst attempting to write inode size " 436 "to lower file xattr; rc = [%d]\n", rc); 437 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); 438 out: 439 return rc; 440 } 441 442 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) 443 { 444 struct ecryptfs_crypt_stat *crypt_stat; 445 446 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 447 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); 448 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) 449 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); 450 else 451 return ecryptfs_write_inode_size_to_header(ecryptfs_inode); 452 } 453 454 /** 455 * ecryptfs_write_end 456 * @file: The eCryptfs file object 457 * @mapping: The eCryptfs object 458 * @pos: The file position 459 * @len: The length of the data (unused) 460 * @copied: The amount of data copied 461 * @page: The eCryptfs page 462 * @fsdata: The fsdata (unused) 463 */ 464 static int ecryptfs_write_end(struct file *file, 465 struct address_space *mapping, 466 loff_t pos, unsigned len, unsigned copied, 467 struct page *page, void *fsdata) 468 { 469 pgoff_t index = pos >> PAGE_SHIFT; 470 unsigned from = pos & (PAGE_SIZE - 1); 471 unsigned to = from + copied; 472 struct inode *ecryptfs_inode = mapping->host; 473 struct ecryptfs_crypt_stat *crypt_stat = 474 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 475 int rc; 476 477 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" 478 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to); 479 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 480 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, 481 to); 482 if (!rc) { 483 rc = copied; 484 fsstack_copy_inode_size(ecryptfs_inode, 485 ecryptfs_inode_to_lower(ecryptfs_inode)); 486 } 487 goto out; 488 } 489 if (!PageUptodate(page)) { 490 if (copied < PAGE_SIZE) { 491 rc = 0; 492 goto out; 493 } 494 SetPageUptodate(page); 495 } 496 /* Fills in zeros if 'to' goes beyond inode size */ 497 rc = fill_zeros_to_end_of_page(page, to); 498 if (rc) { 499 ecryptfs_printk(KERN_WARNING, "Error attempting to fill " 500 "zeros in page with index = [0x%.16lx]\n", index); 501 goto out; 502 } 503 rc = ecryptfs_encrypt_page(page); 504 if (rc) { 505 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper " 506 "index [0x%.16lx])\n", index); 507 goto out; 508 } 509 if (pos + copied > i_size_read(ecryptfs_inode)) { 510 i_size_write(ecryptfs_inode, pos + copied); 511 ecryptfs_printk(KERN_DEBUG, "Expanded file size to " 512 "[0x%.16llx]\n", 513 (unsigned long long)i_size_read(ecryptfs_inode)); 514 } 515 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode); 516 if (rc) 517 printk(KERN_ERR "Error writing inode size to metadata; " 518 "rc = [%d]\n", rc); 519 else 520 rc = copied; 521 out: 522 unlock_page(page); 523 put_page(page); 524 return rc; 525 } 526 527 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block) 528 { 529 struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host); 530 int ret = bmap(lower_inode, &block); 531 532 if (ret) 533 return 0; 534 return block; 535 } 536 537 #include <linux/buffer_head.h> 538 539 const struct address_space_operations ecryptfs_aops = { 540 /* 541 * XXX: This is pretty broken for multiple reasons: ecryptfs does not 542 * actually use buffer_heads, and ecryptfs will crash without 543 * CONFIG_BLOCK. But it matches the behavior before the default for 544 * address_space_operations without the ->dirty_folio method was 545 * cleaned up, so this is the best we can do without maintainer 546 * feedback. 547 */ 548 #ifdef CONFIG_BLOCK 549 .dirty_folio = block_dirty_folio, 550 .invalidate_folio = block_invalidate_folio, 551 #endif 552 .writepage = ecryptfs_writepage, 553 .read_folio = ecryptfs_read_folio, 554 .write_begin = ecryptfs_write_begin, 555 .write_end = ecryptfs_write_end, 556 .bmap = ecryptfs_bmap, 557 }; 558