Loading...
1/**
2 * eCryptfs: Linux filesystem encryption layer
3 * This is where eCryptfs coordinates the symmetric encryption and
4 * decryption of the file data as it passes between the lower
5 * encrypted file and the upper decrypted file.
6 *
7 * Copyright (C) 1997-2003 Erez Zadok
8 * Copyright (C) 2001-2003 Stony Brook University
9 * Copyright (C) 2004-2007 International Business Machines Corp.
10 * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
11 *
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License as
14 * published by the Free Software Foundation; either version 2 of the
15 * License, or (at your option) any later version.
16 *
17 * This program is distributed in the hope that it will be useful, but
18 * WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 * General Public License for more details.
21 *
22 * You should have received a copy of the GNU General Public License
23 * along with this program; if not, write to the Free Software
24 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
25 * 02111-1307, USA.
26 */
27
28#include <linux/pagemap.h>
29#include <linux/writeback.h>
30#include <linux/page-flags.h>
31#include <linux/mount.h>
32#include <linux/file.h>
33#include <linux/crypto.h>
34#include <linux/scatterlist.h>
35#include <linux/slab.h>
36#include <asm/unaligned.h>
37#include "ecryptfs_kernel.h"
38
39/**
40 * ecryptfs_get_locked_page
41 *
42 * Get one page from cache or lower f/s, return error otherwise.
43 *
44 * Returns locked and up-to-date page (if ok), with increased
45 * refcnt.
46 */
47struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index)
48{
49 struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
50 if (!IS_ERR(page))
51 lock_page(page);
52 return page;
53}
54
55/**
56 * ecryptfs_writepage
57 * @page: Page that is locked before this call is made
58 *
59 * Returns zero on success; non-zero otherwise
60 *
61 * This is where we encrypt the data and pass the encrypted data to
62 * the lower filesystem. In OpenPGP-compatible mode, we operate on
63 * entire underlying packets.
64 */
65static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
66{
67 int rc;
68
69 /*
70 * Refuse to write the page out if we are called from reclaim context
71 * since our writepage() path may potentially allocate memory when
72 * calling into the lower fs vfs_write() which may in turn invoke
73 * us again.
74 */
75 if (current->flags & PF_MEMALLOC) {
76 redirty_page_for_writepage(wbc, page);
77 rc = 0;
78 goto out;
79 }
80
81 rc = ecryptfs_encrypt_page(page);
82 if (rc) {
83 ecryptfs_printk(KERN_WARNING, "Error encrypting "
84 "page (upper index [0x%.16lx])\n", page->index);
85 ClearPageUptodate(page);
86 goto out;
87 }
88 SetPageUptodate(page);
89out:
90 unlock_page(page);
91 return rc;
92}
93
94static void strip_xattr_flag(char *page_virt,
95 struct ecryptfs_crypt_stat *crypt_stat)
96{
97 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
98 size_t written;
99
100 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
101 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
102 &written);
103 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
104 }
105}
106
107/**
108 * Header Extent:
109 * Octets 0-7: Unencrypted file size (big-endian)
110 * Octets 8-15: eCryptfs special marker
111 * Octets 16-19: Flags
112 * Octet 16: File format version number (between 0 and 255)
113 * Octets 17-18: Reserved
114 * Octet 19: Bit 1 (lsb): Reserved
115 * Bit 2: Encrypted?
116 * Bits 3-8: Reserved
117 * Octets 20-23: Header extent size (big-endian)
118 * Octets 24-25: Number of header extents at front of file
119 * (big-endian)
120 * Octet 26: Begin RFC 2440 authentication token packet set
121 */
122
123/**
124 * ecryptfs_copy_up_encrypted_with_header
125 * @page: Sort of a ``virtual'' representation of the encrypted lower
126 * file. The actual lower file does not have the metadata in
127 * the header. This is locked.
128 * @crypt_stat: The eCryptfs inode's cryptographic context
129 *
130 * The ``view'' is the version of the file that userspace winds up
131 * seeing, with the header information inserted.
132 */
133static int
134ecryptfs_copy_up_encrypted_with_header(struct page *page,
135 struct ecryptfs_crypt_stat *crypt_stat)
136{
137 loff_t extent_num_in_page = 0;
138 loff_t num_extents_per_page = (PAGE_CACHE_SIZE
139 / crypt_stat->extent_size);
140 int rc = 0;
141
142 while (extent_num_in_page < num_extents_per_page) {
143 loff_t view_extent_num = ((((loff_t)page->index)
144 * num_extents_per_page)
145 + extent_num_in_page);
146 size_t num_header_extents_at_front =
147 (crypt_stat->metadata_size / crypt_stat->extent_size);
148
149 if (view_extent_num < num_header_extents_at_front) {
150 /* This is a header extent */
151 char *page_virt;
152
153 page_virt = kmap_atomic(page);
154 memset(page_virt, 0, PAGE_CACHE_SIZE);
155 /* TODO: Support more than one header extent */
156 if (view_extent_num == 0) {
157 size_t written;
158
159 rc = ecryptfs_read_xattr_region(
160 page_virt, page->mapping->host);
161 strip_xattr_flag(page_virt + 16, crypt_stat);
162 ecryptfs_write_header_metadata(page_virt + 20,
163 crypt_stat,
164 &written);
165 }
166 kunmap_atomic(page_virt);
167 flush_dcache_page(page);
168 if (rc) {
169 printk(KERN_ERR "%s: Error reading xattr "
170 "region; rc = [%d]\n", __func__, rc);
171 goto out;
172 }
173 } else {
174 /* This is an encrypted data extent */
175 loff_t lower_offset =
176 ((view_extent_num * crypt_stat->extent_size)
177 - crypt_stat->metadata_size);
178
179 rc = ecryptfs_read_lower_page_segment(
180 page, (lower_offset >> PAGE_CACHE_SHIFT),
181 (lower_offset & ~PAGE_CACHE_MASK),
182 crypt_stat->extent_size, page->mapping->host);
183 if (rc) {
184 printk(KERN_ERR "%s: Error attempting to read "
185 "extent at offset [%lld] in the lower "
186 "file; rc = [%d]\n", __func__,
187 lower_offset, rc);
188 goto out;
189 }
190 }
191 extent_num_in_page++;
192 }
193out:
194 return rc;
195}
196
197/**
198 * ecryptfs_readpage
199 * @file: An eCryptfs file
200 * @page: Page from eCryptfs inode mapping into which to stick the read data
201 *
202 * Read in a page, decrypting if necessary.
203 *
204 * Returns zero on success; non-zero on error.
205 */
206static int ecryptfs_readpage(struct file *file, struct page *page)
207{
208 struct ecryptfs_crypt_stat *crypt_stat =
209 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
210 int rc = 0;
211
212 if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
213 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
214 PAGE_CACHE_SIZE,
215 page->mapping->host);
216 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
217 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
218 rc = ecryptfs_copy_up_encrypted_with_header(page,
219 crypt_stat);
220 if (rc) {
221 printk(KERN_ERR "%s: Error attempting to copy "
222 "the encrypted content from the lower "
223 "file whilst inserting the metadata "
224 "from the xattr into the header; rc = "
225 "[%d]\n", __func__, rc);
226 goto out;
227 }
228
229 } else {
230 rc = ecryptfs_read_lower_page_segment(
231 page, page->index, 0, PAGE_CACHE_SIZE,
232 page->mapping->host);
233 if (rc) {
234 printk(KERN_ERR "Error reading page; rc = "
235 "[%d]\n", rc);
236 goto out;
237 }
238 }
239 } else {
240 rc = ecryptfs_decrypt_page(page);
241 if (rc) {
242 ecryptfs_printk(KERN_ERR, "Error decrypting page; "
243 "rc = [%d]\n", rc);
244 goto out;
245 }
246 }
247out:
248 if (rc)
249 ClearPageUptodate(page);
250 else
251 SetPageUptodate(page);
252 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
253 page->index);
254 unlock_page(page);
255 return rc;
256}
257
258/**
259 * Called with lower inode mutex held.
260 */
261static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
262{
263 struct inode *inode = page->mapping->host;
264 int end_byte_in_page;
265
266 if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
267 goto out;
268 end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
269 if (to > end_byte_in_page)
270 end_byte_in_page = to;
271 zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
272out:
273 return 0;
274}
275
276/**
277 * ecryptfs_write_begin
278 * @file: The eCryptfs file
279 * @mapping: The eCryptfs object
280 * @pos: The file offset at which to start writing
281 * @len: Length of the write
282 * @flags: Various flags
283 * @pagep: Pointer to return the page
284 * @fsdata: Pointer to return fs data (unused)
285 *
286 * This function must zero any hole we create
287 *
288 * Returns zero on success; non-zero otherwise
289 */
290static int ecryptfs_write_begin(struct file *file,
291 struct address_space *mapping,
292 loff_t pos, unsigned len, unsigned flags,
293 struct page **pagep, void **fsdata)
294{
295 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
296 struct page *page;
297 loff_t prev_page_end_size;
298 int rc = 0;
299
300 page = grab_cache_page_write_begin(mapping, index, flags);
301 if (!page)
302 return -ENOMEM;
303 *pagep = page;
304
305 prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
306 if (!PageUptodate(page)) {
307 struct ecryptfs_crypt_stat *crypt_stat =
308 &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
309
310 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
311 rc = ecryptfs_read_lower_page_segment(
312 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
313 if (rc) {
314 printk(KERN_ERR "%s: Error attemping to read "
315 "lower page segment; rc = [%d]\n",
316 __func__, rc);
317 ClearPageUptodate(page);
318 goto out;
319 } else
320 SetPageUptodate(page);
321 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
322 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
323 rc = ecryptfs_copy_up_encrypted_with_header(
324 page, crypt_stat);
325 if (rc) {
326 printk(KERN_ERR "%s: Error attempting "
327 "to copy the encrypted content "
328 "from the lower file whilst "
329 "inserting the metadata from "
330 "the xattr into the header; rc "
331 "= [%d]\n", __func__, rc);
332 ClearPageUptodate(page);
333 goto out;
334 }
335 SetPageUptodate(page);
336 } else {
337 rc = ecryptfs_read_lower_page_segment(
338 page, index, 0, PAGE_CACHE_SIZE,
339 mapping->host);
340 if (rc) {
341 printk(KERN_ERR "%s: Error reading "
342 "page; rc = [%d]\n",
343 __func__, rc);
344 ClearPageUptodate(page);
345 goto out;
346 }
347 SetPageUptodate(page);
348 }
349 } else {
350 if (prev_page_end_size
351 >= i_size_read(page->mapping->host)) {
352 zero_user(page, 0, PAGE_CACHE_SIZE);
353 } else {
354 rc = ecryptfs_decrypt_page(page);
355 if (rc) {
356 printk(KERN_ERR "%s: Error decrypting "
357 "page at index [%ld]; "
358 "rc = [%d]\n",
359 __func__, page->index, rc);
360 ClearPageUptodate(page);
361 goto out;
362 }
363 }
364 SetPageUptodate(page);
365 }
366 }
367 /* If creating a page or more of holes, zero them out via truncate.
368 * Note, this will increase i_size. */
369 if (index != 0) {
370 if (prev_page_end_size > i_size_read(page->mapping->host)) {
371 rc = ecryptfs_truncate(file->f_path.dentry,
372 prev_page_end_size);
373 if (rc) {
374 printk(KERN_ERR "%s: Error on attempt to "
375 "truncate to (higher) offset [%lld];"
376 " rc = [%d]\n", __func__,
377 prev_page_end_size, rc);
378 goto out;
379 }
380 }
381 }
382 /* Writing to a new page, and creating a small hole from start
383 * of page? Zero it out. */
384 if ((i_size_read(mapping->host) == prev_page_end_size)
385 && (pos != 0))
386 zero_user(page, 0, PAGE_CACHE_SIZE);
387out:
388 if (unlikely(rc)) {
389 unlock_page(page);
390 page_cache_release(page);
391 *pagep = NULL;
392 }
393 return rc;
394}
395
396/**
397 * ecryptfs_write_inode_size_to_header
398 *
399 * Writes the lower file size to the first 8 bytes of the header.
400 *
401 * Returns zero on success; non-zero on error.
402 */
403static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
404{
405 char *file_size_virt;
406 int rc;
407
408 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
409 if (!file_size_virt) {
410 rc = -ENOMEM;
411 goto out;
412 }
413 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
414 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
415 sizeof(u64));
416 kfree(file_size_virt);
417 if (rc < 0)
418 printk(KERN_ERR "%s: Error writing file size to header; "
419 "rc = [%d]\n", __func__, rc);
420 else
421 rc = 0;
422out:
423 return rc;
424}
425
426struct kmem_cache *ecryptfs_xattr_cache;
427
428static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
429{
430 ssize_t size;
431 void *xattr_virt;
432 struct dentry *lower_dentry =
433 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
434 struct inode *lower_inode = lower_dentry->d_inode;
435 int rc;
436
437 if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
438 printk(KERN_WARNING
439 "No support for setting xattr in lower filesystem\n");
440 rc = -ENOSYS;
441 goto out;
442 }
443 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
444 if (!xattr_virt) {
445 printk(KERN_ERR "Out of memory whilst attempting to write "
446 "inode size to xattr\n");
447 rc = -ENOMEM;
448 goto out;
449 }
450 mutex_lock(&lower_inode->i_mutex);
451 size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
452 xattr_virt, PAGE_CACHE_SIZE);
453 if (size < 0)
454 size = 8;
455 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
456 rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
457 xattr_virt, size, 0);
458 mutex_unlock(&lower_inode->i_mutex);
459 if (rc)
460 printk(KERN_ERR "Error whilst attempting to write inode size "
461 "to lower file xattr; rc = [%d]\n", rc);
462 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
463out:
464 return rc;
465}
466
467int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
468{
469 struct ecryptfs_crypt_stat *crypt_stat;
470
471 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
472 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
473 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
474 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
475 else
476 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
477}
478
479/**
480 * ecryptfs_write_end
481 * @file: The eCryptfs file object
482 * @mapping: The eCryptfs object
483 * @pos: The file position
484 * @len: The length of the data (unused)
485 * @copied: The amount of data copied
486 * @page: The eCryptfs page
487 * @fsdata: The fsdata (unused)
488 */
489static int ecryptfs_write_end(struct file *file,
490 struct address_space *mapping,
491 loff_t pos, unsigned len, unsigned copied,
492 struct page *page, void *fsdata)
493{
494 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
495 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
496 unsigned to = from + copied;
497 struct inode *ecryptfs_inode = mapping->host;
498 struct ecryptfs_crypt_stat *crypt_stat =
499 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
500 int rc;
501 int need_unlock_page = 1;
502
503 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
504 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
505 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
506 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
507 to);
508 if (!rc) {
509 rc = copied;
510 fsstack_copy_inode_size(ecryptfs_inode,
511 ecryptfs_inode_to_lower(ecryptfs_inode));
512 }
513 goto out;
514 }
515 /* Fills in zeros if 'to' goes beyond inode size */
516 rc = fill_zeros_to_end_of_page(page, to);
517 if (rc) {
518 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
519 "zeros in page with index = [0x%.16lx]\n", index);
520 goto out;
521 }
522 set_page_dirty(page);
523 unlock_page(page);
524 need_unlock_page = 0;
525 if (pos + copied > i_size_read(ecryptfs_inode)) {
526 i_size_write(ecryptfs_inode, pos + copied);
527 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
528 "[0x%.16llx]\n",
529 (unsigned long long)i_size_read(ecryptfs_inode));
530 balance_dirty_pages_ratelimited(mapping);
531 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
532 if (rc) {
533 printk(KERN_ERR "Error writing inode size to metadata; "
534 "rc = [%d]\n", rc);
535 goto out;
536 }
537 }
538 rc = copied;
539out:
540 if (need_unlock_page)
541 unlock_page(page);
542 page_cache_release(page);
543 return rc;
544}
545
546static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
547{
548 int rc = 0;
549 struct inode *inode;
550 struct inode *lower_inode;
551
552 inode = (struct inode *)mapping->host;
553 lower_inode = ecryptfs_inode_to_lower(inode);
554 if (lower_inode->i_mapping->a_ops->bmap)
555 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
556 block);
557 return rc;
558}
559
560const struct address_space_operations ecryptfs_aops = {
561 .writepage = ecryptfs_writepage,
562 .readpage = ecryptfs_readpage,
563 .write_begin = ecryptfs_write_begin,
564 .write_end = ecryptfs_write_end,
565 .bmap = ecryptfs_bmap,
566};