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 <linux/slab.h>
36 #include <asm/unaligned.h>
37 #include "ecryptfs_kernel.h"
40 * ecryptfs_get_locked_page
42 * Get one page from cache or lower f/s, return error otherwise.
44 * Returns locked and up-to-date page (if ok), with increased
47 struct page
*ecryptfs_get_locked_page(struct file
*file
, loff_t index
)
49 struct dentry
*dentry
;
51 struct address_space
*mapping
;
54 dentry
= file
->f_path
.dentry
;
55 inode
= dentry
->d_inode
;
56 mapping
= inode
->i_mapping
;
57 page
= read_mapping_page(mapping
, index
, (void *)file
);
65 * @page: Page that is locked before this call is made
67 * Returns zero on success; non-zero otherwise
69 static int ecryptfs_writepage(struct page
*page
, struct writeback_control
*wbc
)
73 rc
= ecryptfs_encrypt_page(page
);
75 ecryptfs_printk(KERN_WARNING
, "Error encrypting "
76 "page (upper index [0x%.16x])\n", page
->index
);
77 ClearPageUptodate(page
);
80 SetPageUptodate(page
);
86 static void strip_xattr_flag(char *page_virt
,
87 struct ecryptfs_crypt_stat
*crypt_stat
)
89 if (crypt_stat
->flags
& ECRYPTFS_METADATA_IN_XATTR
) {
92 crypt_stat
->flags
&= ~ECRYPTFS_METADATA_IN_XATTR
;
93 ecryptfs_write_crypt_stat_flags(page_virt
, crypt_stat
,
95 crypt_stat
->flags
|= ECRYPTFS_METADATA_IN_XATTR
;
101 * Octets 0-7: Unencrypted file size (big-endian)
102 * Octets 8-15: eCryptfs special marker
103 * Octets 16-19: Flags
104 * Octet 16: File format version number (between 0 and 255)
105 * Octets 17-18: Reserved
106 * Octet 19: Bit 1 (lsb): Reserved
109 * Octets 20-23: Header extent size (big-endian)
110 * Octets 24-25: Number of header extents at front of file
112 * Octet 26: Begin RFC 2440 authentication token packet set
116 * ecryptfs_copy_up_encrypted_with_header
117 * @page: Sort of a ``virtual'' representation of the encrypted lower
118 * file. The actual lower file does not have the metadata in
119 * the header. This is locked.
120 * @crypt_stat: The eCryptfs inode's cryptographic context
122 * The ``view'' is the version of the file that userspace winds up
123 * seeing, with the header information inserted.
126 ecryptfs_copy_up_encrypted_with_header(struct page
*page
,
127 struct ecryptfs_crypt_stat
*crypt_stat
)
129 loff_t extent_num_in_page
= 0;
130 loff_t num_extents_per_page
= (PAGE_CACHE_SIZE
131 / crypt_stat
->extent_size
);
134 while (extent_num_in_page
< num_extents_per_page
) {
135 loff_t view_extent_num
= ((((loff_t
)page
->index
)
136 * num_extents_per_page
)
137 + extent_num_in_page
);
138 size_t num_header_extents_at_front
=
139 (crypt_stat
->metadata_size
/ crypt_stat
->extent_size
);
141 if (view_extent_num
< num_header_extents_at_front
) {
142 /* This is a header extent */
145 page_virt
= kmap_atomic(page
, KM_USER0
);
146 memset(page_virt
, 0, PAGE_CACHE_SIZE
);
147 /* TODO: Support more than one header extent */
148 if (view_extent_num
== 0) {
151 rc
= ecryptfs_read_xattr_region(
152 page_virt
, page
->mapping
->host
);
153 strip_xattr_flag(page_virt
+ 16, crypt_stat
);
154 ecryptfs_write_header_metadata(page_virt
+ 20,
158 kunmap_atomic(page_virt
, KM_USER0
);
159 flush_dcache_page(page
);
161 printk(KERN_ERR
"%s: Error reading xattr "
162 "region; rc = [%d]\n", __func__
, rc
);
166 /* This is an encrypted data extent */
167 loff_t lower_offset
=
168 ((view_extent_num
* crypt_stat
->extent_size
)
169 - crypt_stat
->metadata_size
);
171 rc
= ecryptfs_read_lower_page_segment(
172 page
, (lower_offset
>> PAGE_CACHE_SHIFT
),
173 (lower_offset
& ~PAGE_CACHE_MASK
),
174 crypt_stat
->extent_size
, page
->mapping
->host
);
176 printk(KERN_ERR
"%s: Error attempting to read "
177 "extent at offset [%lld] in the lower "
178 "file; rc = [%d]\n", __func__
,
183 extent_num_in_page
++;
191 * @file: An eCryptfs file
192 * @page: Page from eCryptfs inode mapping into which to stick the read data
194 * Read in a page, decrypting if necessary.
196 * Returns zero on success; non-zero on error.
198 static int ecryptfs_readpage(struct file
*file
, struct page
*page
)
200 struct ecryptfs_crypt_stat
*crypt_stat
=
201 &ecryptfs_inode_to_private(page
->mapping
->host
)->crypt_stat
;
205 || !(crypt_stat
->flags
& ECRYPTFS_ENCRYPTED
)
206 || (crypt_stat
->flags
& ECRYPTFS_NEW_FILE
)) {
207 ecryptfs_printk(KERN_DEBUG
,
208 "Passing through unencrypted page\n");
209 rc
= ecryptfs_read_lower_page_segment(page
, page
->index
, 0,
211 page
->mapping
->host
);
212 } else if (crypt_stat
->flags
& ECRYPTFS_VIEW_AS_ENCRYPTED
) {
213 if (crypt_stat
->flags
& ECRYPTFS_METADATA_IN_XATTR
) {
214 rc
= ecryptfs_copy_up_encrypted_with_header(page
,
217 printk(KERN_ERR
"%s: Error attempting to copy "
218 "the encrypted content from the lower "
219 "file whilst inserting the metadata "
220 "from the xattr into the header; rc = "
221 "[%d]\n", __func__
, rc
);
226 rc
= ecryptfs_read_lower_page_segment(
227 page
, page
->index
, 0, PAGE_CACHE_SIZE
,
228 page
->mapping
->host
);
230 printk(KERN_ERR
"Error reading page; rc = "
236 rc
= ecryptfs_decrypt_page(page
);
238 ecryptfs_printk(KERN_ERR
, "Error decrypting page; "
245 ClearPageUptodate(page
);
247 SetPageUptodate(page
);
248 ecryptfs_printk(KERN_DEBUG
, "Unlocking page with index = [0x%.16x]\n",
255 * Called with lower inode mutex held.
257 static int fill_zeros_to_end_of_page(struct page
*page
, unsigned int to
)
259 struct inode
*inode
= page
->mapping
->host
;
260 int end_byte_in_page
;
262 if ((i_size_read(inode
) / PAGE_CACHE_SIZE
) != page
->index
)
264 end_byte_in_page
= i_size_read(inode
) % PAGE_CACHE_SIZE
;
265 if (to
> end_byte_in_page
)
266 end_byte_in_page
= to
;
267 zero_user_segment(page
, end_byte_in_page
, PAGE_CACHE_SIZE
);
273 * ecryptfs_write_begin
274 * @file: The eCryptfs file
275 * @mapping: The eCryptfs object
276 * @pos: The file offset at which to start writing
277 * @len: Length of the write
278 * @flags: Various flags
279 * @pagep: Pointer to return the page
280 * @fsdata: Pointer to return fs data (unused)
282 * This function must zero any hole we create
284 * Returns zero on success; non-zero otherwise
286 static int ecryptfs_write_begin(struct file
*file
,
287 struct address_space
*mapping
,
288 loff_t pos
, unsigned len
, unsigned flags
,
289 struct page
**pagep
, void **fsdata
)
291 pgoff_t index
= pos
>> PAGE_CACHE_SHIFT
;
293 loff_t prev_page_end_size
;
296 page
= grab_cache_page_write_begin(mapping
, index
, flags
);
301 if (!PageUptodate(page
)) {
302 struct ecryptfs_crypt_stat
*crypt_stat
=
303 &ecryptfs_inode_to_private(mapping
->host
)->crypt_stat
;
305 if (!(crypt_stat
->flags
& ECRYPTFS_ENCRYPTED
)
306 || (crypt_stat
->flags
& ECRYPTFS_NEW_FILE
)) {
307 rc
= ecryptfs_read_lower_page_segment(
308 page
, index
, 0, PAGE_CACHE_SIZE
, mapping
->host
);
310 printk(KERN_ERR
"%s: Error attemping to read "
311 "lower page segment; rc = [%d]\n",
313 ClearPageUptodate(page
);
316 SetPageUptodate(page
);
317 } else if (crypt_stat
->flags
& ECRYPTFS_VIEW_AS_ENCRYPTED
) {
318 if (crypt_stat
->flags
& ECRYPTFS_METADATA_IN_XATTR
) {
319 rc
= ecryptfs_copy_up_encrypted_with_header(
322 printk(KERN_ERR
"%s: Error attempting "
323 "to copy the encrypted content "
324 "from the lower file whilst "
325 "inserting the metadata from "
326 "the xattr into the header; rc "
327 "= [%d]\n", __func__
, rc
);
328 ClearPageUptodate(page
);
331 SetPageUptodate(page
);
333 rc
= ecryptfs_read_lower_page_segment(
334 page
, index
, 0, PAGE_CACHE_SIZE
,
337 printk(KERN_ERR
"%s: Error reading "
340 ClearPageUptodate(page
);
343 SetPageUptodate(page
);
346 rc
= ecryptfs_decrypt_page(page
);
348 printk(KERN_ERR
"%s: Error decrypting page "
349 "at index [%ld]; rc = [%d]\n",
350 __func__
, page
->index
, rc
);
351 ClearPageUptodate(page
);
354 SetPageUptodate(page
);
357 prev_page_end_size
= ((loff_t
)index
<< PAGE_CACHE_SHIFT
);
358 /* If creating a page or more of holes, zero them out via truncate.
359 * Note, this will increase i_size. */
361 if (prev_page_end_size
> i_size_read(page
->mapping
->host
)) {
362 rc
= ecryptfs_truncate(file
->f_path
.dentry
,
365 printk(KERN_ERR
"%s: Error on attempt to "
366 "truncate to (higher) offset [%lld];"
367 " rc = [%d]\n", __func__
,
368 prev_page_end_size
, rc
);
373 /* Writing to a new page, and creating a small hole from start
374 * of page? Zero it out. */
375 if ((i_size_read(mapping
->host
) == prev_page_end_size
)
377 zero_user(page
, 0, PAGE_CACHE_SIZE
);
383 * ecryptfs_write_inode_size_to_header
385 * Writes the lower file size to the first 8 bytes of the header.
387 * Returns zero on success; non-zero on error.
389 static int ecryptfs_write_inode_size_to_header(struct inode
*ecryptfs_inode
)
391 char *file_size_virt
;
394 file_size_virt
= kmalloc(sizeof(u64
), GFP_KERNEL
);
395 if (!file_size_virt
) {
399 put_unaligned_be64(i_size_read(ecryptfs_inode
), file_size_virt
);
400 rc
= ecryptfs_write_lower(ecryptfs_inode
, file_size_virt
, 0,
402 kfree(file_size_virt
);
404 printk(KERN_ERR
"%s: Error writing file size to header; "
405 "rc = [%d]\n", __func__
, rc
);
412 struct kmem_cache
*ecryptfs_xattr_cache
;
414 static int ecryptfs_write_inode_size_to_xattr(struct inode
*ecryptfs_inode
)
418 struct dentry
*lower_dentry
=
419 ecryptfs_inode_to_private(ecryptfs_inode
)->lower_file
->f_dentry
;
420 struct inode
*lower_inode
= lower_dentry
->d_inode
;
423 if (!lower_inode
->i_op
->getxattr
|| !lower_inode
->i_op
->setxattr
) {
425 "No support for setting xattr in lower filesystem\n");
429 xattr_virt
= kmem_cache_alloc(ecryptfs_xattr_cache
, GFP_KERNEL
);
431 printk(KERN_ERR
"Out of memory whilst attempting to write "
432 "inode size to xattr\n");
436 mutex_lock(&lower_inode
->i_mutex
);
437 size
= lower_inode
->i_op
->getxattr(lower_dentry
, ECRYPTFS_XATTR_NAME
,
438 xattr_virt
, PAGE_CACHE_SIZE
);
441 put_unaligned_be64(i_size_read(ecryptfs_inode
), xattr_virt
);
442 rc
= lower_inode
->i_op
->setxattr(lower_dentry
, ECRYPTFS_XATTR_NAME
,
443 xattr_virt
, size
, 0);
444 mutex_unlock(&lower_inode
->i_mutex
);
446 printk(KERN_ERR
"Error whilst attempting to write inode size "
447 "to lower file xattr; rc = [%d]\n", rc
);
448 kmem_cache_free(ecryptfs_xattr_cache
, xattr_virt
);
453 int ecryptfs_write_inode_size_to_metadata(struct inode
*ecryptfs_inode
)
455 struct ecryptfs_crypt_stat
*crypt_stat
;
457 crypt_stat
= &ecryptfs_inode_to_private(ecryptfs_inode
)->crypt_stat
;
458 BUG_ON(!(crypt_stat
->flags
& ECRYPTFS_ENCRYPTED
));
459 if (crypt_stat
->flags
& ECRYPTFS_METADATA_IN_XATTR
)
460 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode
);
462 return ecryptfs_write_inode_size_to_header(ecryptfs_inode
);
467 * @file: The eCryptfs file object
468 * @mapping: The eCryptfs object
469 * @pos: The file position
470 * @len: The length of the data (unused)
471 * @copied: The amount of data copied
472 * @page: The eCryptfs page
473 * @fsdata: The fsdata (unused)
475 * This is where we encrypt the data and pass the encrypted data to
476 * the lower filesystem. In OpenPGP-compatible mode, we operate on
477 * entire underlying packets.
479 static int ecryptfs_write_end(struct file
*file
,
480 struct address_space
*mapping
,
481 loff_t pos
, unsigned len
, unsigned copied
,
482 struct page
*page
, void *fsdata
)
484 pgoff_t index
= pos
>> PAGE_CACHE_SHIFT
;
485 unsigned from
= pos
& (PAGE_CACHE_SIZE
- 1);
486 unsigned to
= from
+ copied
;
487 struct inode
*ecryptfs_inode
= mapping
->host
;
488 struct ecryptfs_crypt_stat
*crypt_stat
=
489 &ecryptfs_inode_to_private(ecryptfs_inode
)->crypt_stat
;
492 if (crypt_stat
->flags
& ECRYPTFS_NEW_FILE
) {
493 ecryptfs_printk(KERN_DEBUG
, "ECRYPTFS_NEW_FILE flag set in "
494 "crypt_stat at memory location [%p]\n", crypt_stat
);
495 crypt_stat
->flags
&= ~(ECRYPTFS_NEW_FILE
);
497 ecryptfs_printk(KERN_DEBUG
, "Not a new file\n");
498 ecryptfs_printk(KERN_DEBUG
, "Calling fill_zeros_to_end_of_page"
499 "(page w/ index = [0x%.16x], to = [%d])\n", index
, to
);
500 if (!(crypt_stat
->flags
& ECRYPTFS_ENCRYPTED
)) {
501 rc
= ecryptfs_write_lower_page_segment(ecryptfs_inode
, page
, 0,
505 fsstack_copy_inode_size(ecryptfs_inode
,
506 ecryptfs_inode_to_lower(ecryptfs_inode
));
510 /* Fills in zeros if 'to' goes beyond inode size */
511 rc
= fill_zeros_to_end_of_page(page
, to
);
513 ecryptfs_printk(KERN_WARNING
, "Error attempting to fill "
514 "zeros in page with index = [0x%.16x]\n", index
);
517 rc
= ecryptfs_encrypt_page(page
);
519 ecryptfs_printk(KERN_WARNING
, "Error encrypting page (upper "
520 "index [0x%.16x])\n", index
);
523 if (pos
+ copied
> i_size_read(ecryptfs_inode
)) {
524 i_size_write(ecryptfs_inode
, pos
+ copied
);
525 ecryptfs_printk(KERN_DEBUG
, "Expanded file size to "
526 "[0x%.16x]\n", i_size_read(ecryptfs_inode
));
528 rc
= ecryptfs_write_inode_size_to_metadata(ecryptfs_inode
);
530 printk(KERN_ERR
"Error writing inode size to metadata; "
536 page_cache_release(page
);
540 static sector_t
ecryptfs_bmap(struct address_space
*mapping
, sector_t block
)
544 struct inode
*lower_inode
;
546 inode
= (struct inode
*)mapping
->host
;
547 lower_inode
= ecryptfs_inode_to_lower(inode
);
548 if (lower_inode
->i_mapping
->a_ops
->bmap
)
549 rc
= lower_inode
->i_mapping
->a_ops
->bmap(lower_inode
->i_mapping
,
554 const struct address_space_operations ecryptfs_aops
= {
555 .writepage
= ecryptfs_writepage
,
556 .readpage
= ecryptfs_readpage
,
557 .write_begin
= ecryptfs_write_begin
,
558 .write_end
= ecryptfs_write_end
,
559 .bmap
= ecryptfs_bmap
,