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 */
ecryptfs_get_locked_page(struct inode * inode,loff_t index)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 */
ecryptfs_writepage(struct page * page,struct writeback_control * wbc)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
strip_xattr_flag(char * page_virt,struct ecryptfs_crypt_stat * crypt_stat)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
ecryptfs_copy_up_encrypted_with_header(struct page * page,struct ecryptfs_crypt_stat * crypt_stat)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 */
ecryptfs_read_folio(struct file * file,struct folio * folio)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 */
fill_zeros_to_end_of_page(struct page * page,unsigned int to)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 */
ecryptfs_write_begin(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,struct page ** pagep,void ** fsdata)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 */
ecryptfs_write_inode_size_to_header(struct inode * ecryptfs_inode)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
ecryptfs_write_inode_size_to_xattr(struct inode * ecryptfs_inode)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
ecryptfs_write_inode_size_to_metadata(struct inode * ecryptfs_inode)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 */
ecryptfs_write_end(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned copied,struct page * page,void * fsdata)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
ecryptfs_bmap(struct address_space * mapping,sector_t block)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