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