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.
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>
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.
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.
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
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 <asm/unaligned.h>
36 #include "ecryptfs_kernel.h"
39 * ecryptfs_get_locked_page
41 * Get one page from cache or lower f/s, return error otherwise.
43 * Returns locked and up-to-date page (if ok), with increased
46 struct page
*ecryptfs_get_locked_page(struct file
*file
, loff_t index
)
48 struct dentry
*dentry
;
50 struct address_space
*mapping
;
53 dentry
= file
->f_path
.dentry
;
54 inode
= dentry
->d_inode
;
55 mapping
= inode
->i_mapping
;
56 page
= read_mapping_page(mapping
, index
, (void *)file
);
64 * @page: Page that is locked before this call is made
66 * Returns zero on success; non-zero otherwise
68 static int ecryptfs_writepage(struct page
*page
, struct writeback_control
*wbc
)
72 rc
= ecryptfs_encrypt_page(page
);
74 ecryptfs_printk(KERN_WARNING
, "Error encrypting "
75 "page (upper index [0x%.16x])\n", page
->index
);
76 ClearPageUptodate(page
);
79 SetPageUptodate(page
);
87 * Octets 0-7: Unencrypted file size (big-endian)
88 * Octets 8-15: eCryptfs special marker
90 * Octet 16: File format version number (between 0 and 255)
91 * Octets 17-18: Reserved
92 * Octet 19: Bit 1 (lsb): Reserved
95 * Octets 20-23: Header extent size (big-endian)
96 * Octets 24-25: Number of header extents at front of file
98 * Octet 26: Begin RFC 2440 authentication token packet set
102 * ecryptfs_copy_up_encrypted_with_header
103 * @page: Sort of a ``virtual'' representation of the encrypted lower
104 * file. The actual lower file does not have the metadata in
105 * the header. This is locked.
106 * @crypt_stat: The eCryptfs inode's cryptographic context
108 * The ``view'' is the version of the file that userspace winds up
109 * seeing, with the header information inserted.
112 ecryptfs_copy_up_encrypted_with_header(struct page
*page
,
113 struct ecryptfs_crypt_stat
*crypt_stat
)
115 loff_t extent_num_in_page
= 0;
116 loff_t num_extents_per_page
= (PAGE_CACHE_SIZE
117 / crypt_stat
->extent_size
);
120 while (extent_num_in_page
< num_extents_per_page
) {
121 loff_t view_extent_num
= ((((loff_t
)page
->index
)
122 * num_extents_per_page
)
123 + extent_num_in_page
);
124 size_t num_header_extents_at_front
=
125 (crypt_stat
->num_header_bytes_at_front
126 / crypt_stat
->extent_size
);
128 if (view_extent_num
< num_header_extents_at_front
) {
129 /* This is a header extent */
132 page_virt
= kmap_atomic(page
, KM_USER0
);
133 memset(page_virt
, 0, PAGE_CACHE_SIZE
);
134 /* TODO: Support more than one header extent */
135 if (view_extent_num
== 0) {
138 rc
= ecryptfs_read_xattr_region(
139 page_virt
, page
->mapping
->host
);
140 ecryptfs_write_header_metadata(page_virt
+ 20,
144 kunmap_atomic(page_virt
, KM_USER0
);
145 flush_dcache_page(page
);
147 printk(KERN_ERR
"%s: Error reading xattr "
148 "region; rc = [%d]\n", __func__
, rc
);
152 /* This is an encrypted data extent */
153 loff_t lower_offset
=
154 ((view_extent_num
* crypt_stat
->extent_size
)
155 - crypt_stat
->num_header_bytes_at_front
);
157 rc
= ecryptfs_read_lower_page_segment(
158 page
, (lower_offset
>> PAGE_CACHE_SHIFT
),
159 (lower_offset
& ~PAGE_CACHE_MASK
),
160 crypt_stat
->extent_size
, page
->mapping
->host
);
162 printk(KERN_ERR
"%s: Error attempting to read "
163 "extent at offset [%lld] in the lower "
164 "file; rc = [%d]\n", __func__
,
169 extent_num_in_page
++;
177 * @file: An eCryptfs file
178 * @page: Page from eCryptfs inode mapping into which to stick the read data
180 * Read in a page, decrypting if necessary.
182 * Returns zero on success; non-zero on error.
184 static int ecryptfs_readpage(struct file
*file
, struct page
*page
)
186 struct ecryptfs_crypt_stat
*crypt_stat
=
187 &ecryptfs_inode_to_private(file
->f_path
.dentry
->d_inode
)->crypt_stat
;
191 || !(crypt_stat
->flags
& ECRYPTFS_ENCRYPTED
)
192 || (crypt_stat
->flags
& ECRYPTFS_NEW_FILE
)) {
193 ecryptfs_printk(KERN_DEBUG
,
194 "Passing through unencrypted page\n");
195 rc
= ecryptfs_read_lower_page_segment(page
, page
->index
, 0,
197 page
->mapping
->host
);
198 } else if (crypt_stat
->flags
& ECRYPTFS_VIEW_AS_ENCRYPTED
) {
199 if (crypt_stat
->flags
& ECRYPTFS_METADATA_IN_XATTR
) {
200 rc
= ecryptfs_copy_up_encrypted_with_header(page
,
203 printk(KERN_ERR
"%s: Error attempting to copy "
204 "the encrypted content from the lower "
205 "file whilst inserting the metadata "
206 "from the xattr into the header; rc = "
207 "[%d]\n", __func__
, rc
);
212 rc
= ecryptfs_read_lower_page_segment(
213 page
, page
->index
, 0, PAGE_CACHE_SIZE
,
214 page
->mapping
->host
);
216 printk(KERN_ERR
"Error reading page; rc = "
222 rc
= ecryptfs_decrypt_page(page
);
224 ecryptfs_printk(KERN_ERR
, "Error decrypting page; "
231 ClearPageUptodate(page
);
233 SetPageUptodate(page
);
234 ecryptfs_printk(KERN_DEBUG
, "Unlocking page with index = [0x%.16x]\n",
241 * Called with lower inode mutex held.
243 static int fill_zeros_to_end_of_page(struct page
*page
, unsigned int to
)
245 struct inode
*inode
= page
->mapping
->host
;
246 int end_byte_in_page
;
248 if ((i_size_read(inode
) / PAGE_CACHE_SIZE
) != page
->index
)
250 end_byte_in_page
= i_size_read(inode
) % PAGE_CACHE_SIZE
;
251 if (to
> end_byte_in_page
)
252 end_byte_in_page
= to
;
253 zero_user_segment(page
, end_byte_in_page
, PAGE_CACHE_SIZE
);
259 * ecryptfs_write_begin
260 * @file: The eCryptfs file
261 * @mapping: The eCryptfs object
262 * @pos: The file offset at which to start writing
263 * @len: Length of the write
264 * @flags: Various flags
265 * @pagep: Pointer to return the page
266 * @fsdata: Pointer to return fs data (unused)
268 * This function must zero any hole we create
270 * Returns zero on success; non-zero otherwise
272 static int ecryptfs_write_begin(struct file
*file
,
273 struct address_space
*mapping
,
274 loff_t pos
, unsigned len
, unsigned flags
,
275 struct page
**pagep
, void **fsdata
)
277 pgoff_t index
= pos
>> PAGE_CACHE_SHIFT
;
279 loff_t prev_page_end_size
;
282 page
= grab_cache_page_write_begin(mapping
, index
, flags
);
287 if (!PageUptodate(page
)) {
288 struct ecryptfs_crypt_stat
*crypt_stat
=
289 &ecryptfs_inode_to_private(
290 file
->f_path
.dentry
->d_inode
)->crypt_stat
;
292 if (!(crypt_stat
->flags
& ECRYPTFS_ENCRYPTED
)
293 || (crypt_stat
->flags
& ECRYPTFS_NEW_FILE
)) {
294 rc
= ecryptfs_read_lower_page_segment(
295 page
, index
, 0, PAGE_CACHE_SIZE
, mapping
->host
);
297 printk(KERN_ERR
"%s: Error attemping to read "
298 "lower page segment; rc = [%d]\n",
300 ClearPageUptodate(page
);
303 SetPageUptodate(page
);
304 } else if (crypt_stat
->flags
& ECRYPTFS_VIEW_AS_ENCRYPTED
) {
305 if (crypt_stat
->flags
& ECRYPTFS_METADATA_IN_XATTR
) {
306 rc
= ecryptfs_copy_up_encrypted_with_header(
309 printk(KERN_ERR
"%s: Error attempting "
310 "to copy the encrypted content "
311 "from the lower file whilst "
312 "inserting the metadata from "
313 "the xattr into the header; rc "
314 "= [%d]\n", __func__
, rc
);
315 ClearPageUptodate(page
);
318 SetPageUptodate(page
);
320 rc
= ecryptfs_read_lower_page_segment(
321 page
, index
, 0, PAGE_CACHE_SIZE
,
324 printk(KERN_ERR
"%s: Error reading "
327 ClearPageUptodate(page
);
330 SetPageUptodate(page
);
333 rc
= ecryptfs_decrypt_page(page
);
335 printk(KERN_ERR
"%s: Error decrypting page "
336 "at index [%ld]; rc = [%d]\n",
337 __func__
, page
->index
, rc
);
338 ClearPageUptodate(page
);
341 SetPageUptodate(page
);
344 prev_page_end_size
= ((loff_t
)index
<< PAGE_CACHE_SHIFT
);
345 /* If creating a page or more of holes, zero them out via truncate.
346 * Note, this will increase i_size. */
348 if (prev_page_end_size
> i_size_read(page
->mapping
->host
)) {
349 rc
= ecryptfs_truncate(file
->f_path
.dentry
,
352 printk(KERN_ERR
"%s: Error on attempt to "
353 "truncate to (higher) offset [%lld];"
354 " rc = [%d]\n", __func__
,
355 prev_page_end_size
, rc
);
360 /* Writing to a new page, and creating a small hole from start
361 * of page? Zero it out. */
362 if ((i_size_read(mapping
->host
) == prev_page_end_size
)
364 zero_user(page
, 0, PAGE_CACHE_SIZE
);
370 * ecryptfs_write_inode_size_to_header
372 * Writes the lower file size to the first 8 bytes of the header.
374 * Returns zero on success; non-zero on error.
376 static int ecryptfs_write_inode_size_to_header(struct inode
*ecryptfs_inode
)
378 char *file_size_virt
;
381 file_size_virt
= kmalloc(sizeof(u64
), GFP_KERNEL
);
382 if (!file_size_virt
) {
386 put_unaligned_be64(i_size_read(ecryptfs_inode
), file_size_virt
);
387 rc
= ecryptfs_write_lower(ecryptfs_inode
, file_size_virt
, 0,
389 kfree(file_size_virt
);
391 printk(KERN_ERR
"%s: Error writing file size to header; "
392 "rc = [%d]\n", __func__
, rc
);
399 struct kmem_cache
*ecryptfs_xattr_cache
;
401 static int ecryptfs_write_inode_size_to_xattr(struct inode
*ecryptfs_inode
)
405 struct dentry
*lower_dentry
=
406 ecryptfs_inode_to_private(ecryptfs_inode
)->lower_file
->f_dentry
;
407 struct inode
*lower_inode
= lower_dentry
->d_inode
;
410 if (!lower_inode
->i_op
->getxattr
|| !lower_inode
->i_op
->setxattr
) {
412 "No support for setting xattr in lower filesystem\n");
416 xattr_virt
= kmem_cache_alloc(ecryptfs_xattr_cache
, GFP_KERNEL
);
418 printk(KERN_ERR
"Out of memory whilst attempting to write "
419 "inode size to xattr\n");
423 mutex_lock(&lower_inode
->i_mutex
);
424 size
= lower_inode
->i_op
->getxattr(lower_dentry
, ECRYPTFS_XATTR_NAME
,
425 xattr_virt
, PAGE_CACHE_SIZE
);
428 put_unaligned_be64(i_size_read(ecryptfs_inode
), xattr_virt
);
429 rc
= lower_inode
->i_op
->setxattr(lower_dentry
, ECRYPTFS_XATTR_NAME
,
430 xattr_virt
, size
, 0);
431 mutex_unlock(&lower_inode
->i_mutex
);
433 printk(KERN_ERR
"Error whilst attempting to write inode size "
434 "to lower file xattr; rc = [%d]\n", rc
);
435 kmem_cache_free(ecryptfs_xattr_cache
, xattr_virt
);
440 int ecryptfs_write_inode_size_to_metadata(struct inode
*ecryptfs_inode
)
442 struct ecryptfs_crypt_stat
*crypt_stat
;
444 crypt_stat
= &ecryptfs_inode_to_private(ecryptfs_inode
)->crypt_stat
;
445 BUG_ON(!(crypt_stat
->flags
& ECRYPTFS_ENCRYPTED
));
446 if (crypt_stat
->flags
& ECRYPTFS_METADATA_IN_XATTR
)
447 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode
);
449 return ecryptfs_write_inode_size_to_header(ecryptfs_inode
);
454 * @file: The eCryptfs file object
455 * @mapping: The eCryptfs object
456 * @pos: The file position
457 * @len: The length of the data (unused)
458 * @copied: The amount of data copied
459 * @page: The eCryptfs page
460 * @fsdata: The fsdata (unused)
462 * This is where we encrypt the data and pass the encrypted data to
463 * the lower filesystem. In OpenPGP-compatible mode, we operate on
464 * entire underlying packets.
466 static int ecryptfs_write_end(struct file
*file
,
467 struct address_space
*mapping
,
468 loff_t pos
, unsigned len
, unsigned copied
,
469 struct page
*page
, void *fsdata
)
471 pgoff_t index
= pos
>> PAGE_CACHE_SHIFT
;
472 unsigned from
= pos
& (PAGE_CACHE_SIZE
- 1);
473 unsigned to
= from
+ copied
;
474 struct inode
*ecryptfs_inode
= mapping
->host
;
475 struct ecryptfs_crypt_stat
*crypt_stat
=
476 &ecryptfs_inode_to_private(file
->f_path
.dentry
->d_inode
)->crypt_stat
;
479 if (crypt_stat
->flags
& ECRYPTFS_NEW_FILE
) {
480 ecryptfs_printk(KERN_DEBUG
, "ECRYPTFS_NEW_FILE flag set in "
481 "crypt_stat at memory location [%p]\n", crypt_stat
);
482 crypt_stat
->flags
&= ~(ECRYPTFS_NEW_FILE
);
484 ecryptfs_printk(KERN_DEBUG
, "Not a new file\n");
485 ecryptfs_printk(KERN_DEBUG
, "Calling fill_zeros_to_end_of_page"
486 "(page w/ index = [0x%.16x], to = [%d])\n", index
, to
);
487 if (!(crypt_stat
->flags
& ECRYPTFS_ENCRYPTED
)) {
488 rc
= ecryptfs_write_lower_page_segment(ecryptfs_inode
, page
, 0,
492 fsstack_copy_inode_size(ecryptfs_inode
,
493 ecryptfs_inode_to_lower(ecryptfs_inode
));
497 /* Fills in zeros if 'to' goes beyond inode size */
498 rc
= fill_zeros_to_end_of_page(page
, to
);
500 ecryptfs_printk(KERN_WARNING
, "Error attempting to fill "
501 "zeros in page with index = [0x%.16x]\n", index
);
504 rc
= ecryptfs_encrypt_page(page
);
506 ecryptfs_printk(KERN_WARNING
, "Error encrypting page (upper "
507 "index [0x%.16x])\n", index
);
510 if (pos
+ copied
> i_size_read(ecryptfs_inode
)) {
511 i_size_write(ecryptfs_inode
, pos
+ copied
);
512 ecryptfs_printk(KERN_DEBUG
, "Expanded file size to "
513 "[0x%.16x]\n", i_size_read(ecryptfs_inode
));
515 rc
= ecryptfs_write_inode_size_to_metadata(ecryptfs_inode
);
517 printk(KERN_ERR
"Error writing inode size to metadata; "
523 page_cache_release(page
);
527 static sector_t
ecryptfs_bmap(struct address_space
*mapping
, sector_t block
)
531 struct inode
*lower_inode
;
533 inode
= (struct inode
*)mapping
->host
;
534 lower_inode
= ecryptfs_inode_to_lower(inode
);
535 if (lower_inode
->i_mapping
->a_ops
->bmap
)
536 rc
= lower_inode
->i_mapping
->a_ops
->bmap(lower_inode
->i_mapping
,
541 const struct address_space_operations ecryptfs_aops
= {
542 .writepage
= ecryptfs_writepage
,
543 .readpage
= ecryptfs_readpage
,
544 .write_begin
= ecryptfs_write_begin
,
545 .write_end
= ecryptfs_write_end
,
546 .bmap
= ecryptfs_bmap
,