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_local_page(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_local(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 * @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,
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);
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(&nop_mnt_idmap, 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 #include <linux/buffer_head.h>
537
538 const struct address_space_operations ecryptfs_aops = {
539 /*
540 * XXX: This is pretty broken for multiple reasons: ecryptfs does not
541 * actually use buffer_heads, and ecryptfs will crash without
542 * CONFIG_BLOCK. But it matches the behavior before the default for
543 * address_space_operations without the ->dirty_folio method was
544 * cleaned up, so this is the best we can do without maintainer
545 * feedback.
546 */
547 #ifdef CONFIG_BLOCK
548 .dirty_folio = block_dirty_folio,
549 .invalidate_folio = block_invalidate_folio,
550 #endif
551 .writepage = ecryptfs_writepage,
552 .read_folio = ecryptfs_read_folio,
553 .write_begin = ecryptfs_write_begin,
554 .write_end = ecryptfs_write_end,
555 .bmap = ecryptfs_bmap,
556 };
557
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