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_readpage 174 * @file: An eCryptfs file 175 * @page: Page from eCryptfs inode mapping into which to stick the read data 176 * 177 * Read in a page, decrypting if necessary. 178 * 179 * Returns zero on success; non-zero on error. 180 */ 181 static int ecryptfs_readpage(struct file *file, struct page *page) 182 { 183 struct ecryptfs_crypt_stat *crypt_stat = 184 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat; 185 int rc = 0; 186 187 if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 188 rc = ecryptfs_read_lower_page_segment(page, page->index, 0, 189 PAGE_SIZE, 190 page->mapping->host); 191 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 192 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 193 rc = ecryptfs_copy_up_encrypted_with_header(page, 194 crypt_stat); 195 if (rc) { 196 printk(KERN_ERR "%s: Error attempting to copy " 197 "the encrypted content from the lower " 198 "file whilst inserting the metadata " 199 "from the xattr into the header; rc = " 200 "[%d]\n", __func__, rc); 201 goto out; 202 } 203 204 } else { 205 rc = ecryptfs_read_lower_page_segment( 206 page, page->index, 0, PAGE_SIZE, 207 page->mapping->host); 208 if (rc) { 209 printk(KERN_ERR "Error reading page; rc = " 210 "[%d]\n", rc); 211 goto out; 212 } 213 } 214 } else { 215 rc = ecryptfs_decrypt_page(page); 216 if (rc) { 217 ecryptfs_printk(KERN_ERR, "Error decrypting page; " 218 "rc = [%d]\n", rc); 219 goto out; 220 } 221 } 222 out: 223 if (rc) 224 ClearPageUptodate(page); 225 else 226 SetPageUptodate(page); 227 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n", 228 page->index); 229 unlock_page(page); 230 return rc; 231 } 232 233 /* 234 * Called with lower inode mutex held. 235 */ 236 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to) 237 { 238 struct inode *inode = page->mapping->host; 239 int end_byte_in_page; 240 241 if ((i_size_read(inode) / PAGE_SIZE) != page->index) 242 goto out; 243 end_byte_in_page = i_size_read(inode) % PAGE_SIZE; 244 if (to > end_byte_in_page) 245 end_byte_in_page = to; 246 zero_user_segment(page, end_byte_in_page, PAGE_SIZE); 247 out: 248 return 0; 249 } 250 251 /** 252 * ecryptfs_write_begin 253 * @file: The eCryptfs file 254 * @mapping: The eCryptfs object 255 * @pos: The file offset at which to start writing 256 * @len: Length of the write 257 * @flags: Various flags 258 * @pagep: Pointer to return the page 259 * @fsdata: Pointer to return fs data (unused) 260 * 261 * This function must zero any hole we create 262 * 263 * Returns zero on success; non-zero otherwise 264 */ 265 static int ecryptfs_write_begin(struct file *file, 266 struct address_space *mapping, 267 loff_t pos, unsigned len, unsigned flags, 268 struct page **pagep, void **fsdata) 269 { 270 pgoff_t index = pos >> PAGE_SHIFT; 271 struct page *page; 272 loff_t prev_page_end_size; 273 int rc = 0; 274 275 page = grab_cache_page_write_begin(mapping, index, flags); 276 if (!page) 277 return -ENOMEM; 278 *pagep = page; 279 280 prev_page_end_size = ((loff_t)index << PAGE_SHIFT); 281 if (!PageUptodate(page)) { 282 struct ecryptfs_crypt_stat *crypt_stat = 283 &ecryptfs_inode_to_private(mapping->host)->crypt_stat; 284 285 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 286 rc = ecryptfs_read_lower_page_segment( 287 page, index, 0, PAGE_SIZE, mapping->host); 288 if (rc) { 289 printk(KERN_ERR "%s: Error attempting to read " 290 "lower page segment; rc = [%d]\n", 291 __func__, rc); 292 ClearPageUptodate(page); 293 goto out; 294 } else 295 SetPageUptodate(page); 296 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { 297 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { 298 rc = ecryptfs_copy_up_encrypted_with_header( 299 page, crypt_stat); 300 if (rc) { 301 printk(KERN_ERR "%s: Error attempting " 302 "to copy the encrypted content " 303 "from the lower file whilst " 304 "inserting the metadata from " 305 "the xattr into the header; rc " 306 "= [%d]\n", __func__, rc); 307 ClearPageUptodate(page); 308 goto out; 309 } 310 SetPageUptodate(page); 311 } else { 312 rc = ecryptfs_read_lower_page_segment( 313 page, index, 0, PAGE_SIZE, 314 mapping->host); 315 if (rc) { 316 printk(KERN_ERR "%s: Error reading " 317 "page; rc = [%d]\n", 318 __func__, rc); 319 ClearPageUptodate(page); 320 goto out; 321 } 322 SetPageUptodate(page); 323 } 324 } else { 325 if (prev_page_end_size 326 >= i_size_read(page->mapping->host)) { 327 zero_user(page, 0, PAGE_SIZE); 328 SetPageUptodate(page); 329 } else if (len < PAGE_SIZE) { 330 rc = ecryptfs_decrypt_page(page); 331 if (rc) { 332 printk(KERN_ERR "%s: Error decrypting " 333 "page at index [%ld]; " 334 "rc = [%d]\n", 335 __func__, page->index, rc); 336 ClearPageUptodate(page); 337 goto out; 338 } 339 SetPageUptodate(page); 340 } 341 } 342 } 343 /* If creating a page or more of holes, zero them out via truncate. 344 * Note, this will increase i_size. */ 345 if (index != 0) { 346 if (prev_page_end_size > i_size_read(page->mapping->host)) { 347 rc = ecryptfs_truncate(file->f_path.dentry, 348 prev_page_end_size); 349 if (rc) { 350 printk(KERN_ERR "%s: Error on attempt to " 351 "truncate to (higher) offset [%lld];" 352 " rc = [%d]\n", __func__, 353 prev_page_end_size, rc); 354 goto out; 355 } 356 } 357 } 358 /* Writing to a new page, and creating a small hole from start 359 * of page? Zero it out. */ 360 if ((i_size_read(mapping->host) == prev_page_end_size) 361 && (pos != 0)) 362 zero_user(page, 0, PAGE_SIZE); 363 out: 364 if (unlikely(rc)) { 365 unlock_page(page); 366 put_page(page); 367 *pagep = NULL; 368 } 369 return rc; 370 } 371 372 /* 373 * ecryptfs_write_inode_size_to_header 374 * 375 * Writes the lower file size to the first 8 bytes of the header. 376 * 377 * Returns zero on success; non-zero on error. 378 */ 379 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) 380 { 381 char *file_size_virt; 382 int rc; 383 384 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); 385 if (!file_size_virt) { 386 rc = -ENOMEM; 387 goto out; 388 } 389 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); 390 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, 391 sizeof(u64)); 392 kfree(file_size_virt); 393 if (rc < 0) 394 printk(KERN_ERR "%s: Error writing file size to header; " 395 "rc = [%d]\n", __func__, rc); 396 else 397 rc = 0; 398 out: 399 return rc; 400 } 401 402 struct kmem_cache *ecryptfs_xattr_cache; 403 404 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) 405 { 406 ssize_t size; 407 void *xattr_virt; 408 struct dentry *lower_dentry = 409 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry; 410 struct inode *lower_inode = d_inode(lower_dentry); 411 int rc; 412 413 if (!(lower_inode->i_opflags & IOP_XATTR)) { 414 printk(KERN_WARNING 415 "No support for setting xattr in lower filesystem\n"); 416 rc = -ENOSYS; 417 goto out; 418 } 419 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); 420 if (!xattr_virt) { 421 rc = -ENOMEM; 422 goto out; 423 } 424 inode_lock(lower_inode); 425 size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME, 426 xattr_virt, PAGE_SIZE); 427 if (size < 0) 428 size = 8; 429 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt); 430 rc = __vfs_setxattr(&init_user_ns, lower_dentry, lower_inode, 431 ECRYPTFS_XATTR_NAME, xattr_virt, size, 0); 432 inode_unlock(lower_inode); 433 if (rc) 434 printk(KERN_ERR "Error whilst attempting to write inode size " 435 "to lower file xattr; rc = [%d]\n", rc); 436 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); 437 out: 438 return rc; 439 } 440 441 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) 442 { 443 struct ecryptfs_crypt_stat *crypt_stat; 444 445 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 446 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); 447 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) 448 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); 449 else 450 return ecryptfs_write_inode_size_to_header(ecryptfs_inode); 451 } 452 453 /** 454 * ecryptfs_write_end 455 * @file: The eCryptfs file object 456 * @mapping: The eCryptfs object 457 * @pos: The file position 458 * @len: The length of the data (unused) 459 * @copied: The amount of data copied 460 * @page: The eCryptfs page 461 * @fsdata: The fsdata (unused) 462 */ 463 static int ecryptfs_write_end(struct file *file, 464 struct address_space *mapping, 465 loff_t pos, unsigned len, unsigned copied, 466 struct page *page, void *fsdata) 467 { 468 pgoff_t index = pos >> PAGE_SHIFT; 469 unsigned from = pos & (PAGE_SIZE - 1); 470 unsigned to = from + copied; 471 struct inode *ecryptfs_inode = mapping->host; 472 struct ecryptfs_crypt_stat *crypt_stat = 473 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 474 int rc; 475 476 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" 477 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to); 478 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { 479 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, 480 to); 481 if (!rc) { 482 rc = copied; 483 fsstack_copy_inode_size(ecryptfs_inode, 484 ecryptfs_inode_to_lower(ecryptfs_inode)); 485 } 486 goto out; 487 } 488 if (!PageUptodate(page)) { 489 if (copied < PAGE_SIZE) { 490 rc = 0; 491 goto out; 492 } 493 SetPageUptodate(page); 494 } 495 /* Fills in zeros if 'to' goes beyond inode size */ 496 rc = fill_zeros_to_end_of_page(page, to); 497 if (rc) { 498 ecryptfs_printk(KERN_WARNING, "Error attempting to fill " 499 "zeros in page with index = [0x%.16lx]\n", index); 500 goto out; 501 } 502 rc = ecryptfs_encrypt_page(page); 503 if (rc) { 504 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper " 505 "index [0x%.16lx])\n", index); 506 goto out; 507 } 508 if (pos + copied > i_size_read(ecryptfs_inode)) { 509 i_size_write(ecryptfs_inode, pos + copied); 510 ecryptfs_printk(KERN_DEBUG, "Expanded file size to " 511 "[0x%.16llx]\n", 512 (unsigned long long)i_size_read(ecryptfs_inode)); 513 } 514 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode); 515 if (rc) 516 printk(KERN_ERR "Error writing inode size to metadata; " 517 "rc = [%d]\n", rc); 518 else 519 rc = copied; 520 out: 521 unlock_page(page); 522 put_page(page); 523 return rc; 524 } 525 526 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block) 527 { 528 struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host); 529 int ret = bmap(lower_inode, &block); 530 531 if (ret) 532 return 0; 533 return block; 534 } 535 536 const struct address_space_operations ecryptfs_aops = { 537 .writepage = ecryptfs_writepage, 538 .readpage = ecryptfs_readpage, 539 .write_begin = ecryptfs_write_begin, 540 .write_end = ecryptfs_write_end, 541 .bmap = ecryptfs_bmap, 542 }; 543