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/scatterlist.h>
34 #include <linux/slab.h>
35 #include <linux/xattr.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 */
ecryptfs_get_locked_page(struct inode * inode,loff_t index)47 struct 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 */
ecryptfs_writepage(struct page * page,struct writeback_control * wbc)65 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
66 {
67 int rc;
68
69 rc = ecryptfs_encrypt_page(page);
70 if (rc) {
71 ecryptfs_printk(KERN_WARNING, "Error encrypting "
72 "page (upper index [0x%.16lx])\n", page->index);
73 ClearPageUptodate(page);
74 goto out;
75 }
76 SetPageUptodate(page);
77 out:
78 unlock_page(page);
79 return rc;
80 }
81
strip_xattr_flag(char * page_virt,struct ecryptfs_crypt_stat * crypt_stat)82 static void strip_xattr_flag(char *page_virt,
83 struct ecryptfs_crypt_stat *crypt_stat)
84 {
85 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
86 size_t written;
87
88 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
89 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
90 &written);
91 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
92 }
93 }
94
95 /**
96 * Header Extent:
97 * Octets 0-7: Unencrypted file size (big-endian)
98 * Octets 8-15: eCryptfs special marker
99 * Octets 16-19: Flags
100 * Octet 16: File format version number (between 0 and 255)
101 * Octets 17-18: Reserved
102 * Octet 19: Bit 1 (lsb): Reserved
103 * Bit 2: Encrypted?
104 * Bits 3-8: Reserved
105 * Octets 20-23: Header extent size (big-endian)
106 * Octets 24-25: Number of header extents at front of file
107 * (big-endian)
108 * Octet 26: Begin RFC 2440 authentication token packet set
109 */
110
111 /**
112 * ecryptfs_copy_up_encrypted_with_header
113 * @page: Sort of a ``virtual'' representation of the encrypted lower
114 * file. The actual lower file does not have the metadata in
115 * the header. This is locked.
116 * @crypt_stat: The eCryptfs inode's cryptographic context
117 *
118 * The ``view'' is the version of the file that userspace winds up
119 * seeing, with the header information inserted.
120 */
121 static int
ecryptfs_copy_up_encrypted_with_header(struct page * page,struct ecryptfs_crypt_stat * crypt_stat)122 ecryptfs_copy_up_encrypted_with_header(struct page *page,
123 struct ecryptfs_crypt_stat *crypt_stat)
124 {
125 loff_t extent_num_in_page = 0;
126 loff_t num_extents_per_page = (PAGE_SIZE
127 / crypt_stat->extent_size);
128 int rc = 0;
129
130 while (extent_num_in_page < num_extents_per_page) {
131 loff_t view_extent_num = ((((loff_t)page->index)
132 * num_extents_per_page)
133 + extent_num_in_page);
134 size_t num_header_extents_at_front =
135 (crypt_stat->metadata_size / crypt_stat->extent_size);
136
137 if (view_extent_num < num_header_extents_at_front) {
138 /* This is a header extent */
139 char *page_virt;
140
141 page_virt = kmap_atomic(page);
142 memset(page_virt, 0, PAGE_SIZE);
143 /* TODO: Support more than one header extent */
144 if (view_extent_num == 0) {
145 size_t written;
146
147 rc = ecryptfs_read_xattr_region(
148 page_virt, page->mapping->host);
149 strip_xattr_flag(page_virt + 16, crypt_stat);
150 ecryptfs_write_header_metadata(page_virt + 20,
151 crypt_stat,
152 &written);
153 }
154 kunmap_atomic(page_virt);
155 flush_dcache_page(page);
156 if (rc) {
157 printk(KERN_ERR "%s: Error reading xattr "
158 "region; rc = [%d]\n", __func__, rc);
159 goto out;
160 }
161 } else {
162 /* This is an encrypted data extent */
163 loff_t lower_offset =
164 ((view_extent_num * crypt_stat->extent_size)
165 - crypt_stat->metadata_size);
166
167 rc = ecryptfs_read_lower_page_segment(
168 page, (lower_offset >> PAGE_SHIFT),
169 (lower_offset & ~PAGE_MASK),
170 crypt_stat->extent_size, page->mapping->host);
171 if (rc) {
172 printk(KERN_ERR "%s: Error attempting to read "
173 "extent at offset [%lld] in the lower "
174 "file; rc = [%d]\n", __func__,
175 lower_offset, rc);
176 goto out;
177 }
178 }
179 extent_num_in_page++;
180 }
181 out:
182 return rc;
183 }
184
185 /**
186 * ecryptfs_readpage
187 * @file: An eCryptfs file
188 * @page: Page from eCryptfs inode mapping into which to stick the read data
189 *
190 * Read in a page, decrypting if necessary.
191 *
192 * Returns zero on success; non-zero on error.
193 */
ecryptfs_readpage(struct file * file,struct page * page)194 static int ecryptfs_readpage(struct file *file, struct page *page)
195 {
196 struct ecryptfs_crypt_stat *crypt_stat =
197 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
198 int rc = 0;
199
200 if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
201 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
202 PAGE_SIZE,
203 page->mapping->host);
204 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
205 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
206 rc = ecryptfs_copy_up_encrypted_with_header(page,
207 crypt_stat);
208 if (rc) {
209 printk(KERN_ERR "%s: Error attempting to copy "
210 "the encrypted content from the lower "
211 "file whilst inserting the metadata "
212 "from the xattr into the header; rc = "
213 "[%d]\n", __func__, rc);
214 goto out;
215 }
216
217 } else {
218 rc = ecryptfs_read_lower_page_segment(
219 page, page->index, 0, PAGE_SIZE,
220 page->mapping->host);
221 if (rc) {
222 printk(KERN_ERR "Error reading page; rc = "
223 "[%d]\n", rc);
224 goto out;
225 }
226 }
227 } else {
228 rc = ecryptfs_decrypt_page(page);
229 if (rc) {
230 ecryptfs_printk(KERN_ERR, "Error decrypting page; "
231 "rc = [%d]\n", rc);
232 goto out;
233 }
234 }
235 out:
236 if (rc)
237 ClearPageUptodate(page);
238 else
239 SetPageUptodate(page);
240 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
241 page->index);
242 unlock_page(page);
243 return rc;
244 }
245
246 /**
247 * Called with lower inode mutex held.
248 */
fill_zeros_to_end_of_page(struct page * page,unsigned int to)249 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
250 {
251 struct inode *inode = page->mapping->host;
252 int end_byte_in_page;
253
254 if ((i_size_read(inode) / PAGE_SIZE) != page->index)
255 goto out;
256 end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
257 if (to > end_byte_in_page)
258 end_byte_in_page = to;
259 zero_user_segment(page, end_byte_in_page, PAGE_SIZE);
260 out:
261 return 0;
262 }
263
264 /**
265 * ecryptfs_write_begin
266 * @file: The eCryptfs file
267 * @mapping: The eCryptfs object
268 * @pos: The file offset at which to start writing
269 * @len: Length of the write
270 * @flags: Various flags
271 * @pagep: Pointer to return the page
272 * @fsdata: Pointer to return fs data (unused)
273 *
274 * This function must zero any hole we create
275 *
276 * Returns zero on success; non-zero otherwise
277 */
ecryptfs_write_begin(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned flags,struct page ** pagep,void ** fsdata)278 static int ecryptfs_write_begin(struct file *file,
279 struct address_space *mapping,
280 loff_t pos, unsigned len, unsigned flags,
281 struct page **pagep, void **fsdata)
282 {
283 pgoff_t index = pos >> PAGE_SHIFT;
284 struct page *page;
285 loff_t prev_page_end_size;
286 int rc = 0;
287
288 page = grab_cache_page_write_begin(mapping, index, flags);
289 if (!page)
290 return -ENOMEM;
291 *pagep = page;
292
293 prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
294 if (!PageUptodate(page)) {
295 struct ecryptfs_crypt_stat *crypt_stat =
296 &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
297
298 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
299 rc = ecryptfs_read_lower_page_segment(
300 page, index, 0, PAGE_SIZE, mapping->host);
301 if (rc) {
302 printk(KERN_ERR "%s: Error attempting to read "
303 "lower page segment; rc = [%d]\n",
304 __func__, rc);
305 ClearPageUptodate(page);
306 goto out;
307 } else
308 SetPageUptodate(page);
309 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
310 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
311 rc = ecryptfs_copy_up_encrypted_with_header(
312 page, crypt_stat);
313 if (rc) {
314 printk(KERN_ERR "%s: Error attempting "
315 "to copy the encrypted content "
316 "from the lower file whilst "
317 "inserting the metadata from "
318 "the xattr into the header; rc "
319 "= [%d]\n", __func__, rc);
320 ClearPageUptodate(page);
321 goto out;
322 }
323 SetPageUptodate(page);
324 } else {
325 rc = ecryptfs_read_lower_page_segment(
326 page, index, 0, PAGE_SIZE,
327 mapping->host);
328 if (rc) {
329 printk(KERN_ERR "%s: Error reading "
330 "page; rc = [%d]\n",
331 __func__, rc);
332 ClearPageUptodate(page);
333 goto out;
334 }
335 SetPageUptodate(page);
336 }
337 } else {
338 if (prev_page_end_size
339 >= i_size_read(page->mapping->host)) {
340 zero_user(page, 0, PAGE_SIZE);
341 SetPageUptodate(page);
342 } else if (len < PAGE_SIZE) {
343 rc = ecryptfs_decrypt_page(page);
344 if (rc) {
345 printk(KERN_ERR "%s: Error decrypting "
346 "page at index [%ld]; "
347 "rc = [%d]\n",
348 __func__, page->index, rc);
349 ClearPageUptodate(page);
350 goto out;
351 }
352 SetPageUptodate(page);
353 }
354 }
355 }
356 /* If creating a page or more of holes, zero them out via truncate.
357 * Note, this will increase i_size. */
358 if (index != 0) {
359 if (prev_page_end_size > i_size_read(page->mapping->host)) {
360 rc = ecryptfs_truncate(file->f_path.dentry,
361 prev_page_end_size);
362 if (rc) {
363 printk(KERN_ERR "%s: Error on attempt to "
364 "truncate to (higher) offset [%lld];"
365 " rc = [%d]\n", __func__,
366 prev_page_end_size, rc);
367 goto out;
368 }
369 }
370 }
371 /* Writing to a new page, and creating a small hole from start
372 * of page? Zero it out. */
373 if ((i_size_read(mapping->host) == prev_page_end_size)
374 && (pos != 0))
375 zero_user(page, 0, PAGE_SIZE);
376 out:
377 if (unlikely(rc)) {
378 unlock_page(page);
379 put_page(page);
380 *pagep = NULL;
381 }
382 return rc;
383 }
384
385 /**
386 * ecryptfs_write_inode_size_to_header
387 *
388 * Writes the lower file size to the first 8 bytes of the header.
389 *
390 * Returns zero on success; non-zero on error.
391 */
ecryptfs_write_inode_size_to_header(struct inode * ecryptfs_inode)392 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
393 {
394 char *file_size_virt;
395 int rc;
396
397 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
398 if (!file_size_virt) {
399 rc = -ENOMEM;
400 goto out;
401 }
402 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
403 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
404 sizeof(u64));
405 kfree(file_size_virt);
406 if (rc < 0)
407 printk(KERN_ERR "%s: Error writing file size to header; "
408 "rc = [%d]\n", __func__, rc);
409 else
410 rc = 0;
411 out:
412 return rc;
413 }
414
415 struct kmem_cache *ecryptfs_xattr_cache;
416
ecryptfs_write_inode_size_to_xattr(struct inode * ecryptfs_inode)417 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
418 {
419 ssize_t size;
420 void *xattr_virt;
421 struct dentry *lower_dentry =
422 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
423 struct inode *lower_inode = d_inode(lower_dentry);
424 int rc;
425
426 if (!(lower_inode->i_opflags & IOP_XATTR)) {
427 printk(KERN_WARNING
428 "No support for setting xattr in lower filesystem\n");
429 rc = -ENOSYS;
430 goto out;
431 }
432 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
433 if (!xattr_virt) {
434 rc = -ENOMEM;
435 goto out;
436 }
437 inode_lock(lower_inode);
438 size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
439 xattr_virt, PAGE_SIZE);
440 if (size < 0)
441 size = 8;
442 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
443 rc = __vfs_setxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
444 xattr_virt, size, 0);
445 inode_unlock(lower_inode);
446 if (rc)
447 printk(KERN_ERR "Error whilst attempting to write inode size "
448 "to lower file xattr; rc = [%d]\n", rc);
449 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
450 out:
451 return rc;
452 }
453
ecryptfs_write_inode_size_to_metadata(struct inode * ecryptfs_inode)454 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
455 {
456 struct ecryptfs_crypt_stat *crypt_stat;
457
458 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
459 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
460 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
461 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
462 else
463 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
464 }
465
466 /**
467 * ecryptfs_write_end
468 * @file: The eCryptfs file object
469 * @mapping: The eCryptfs object
470 * @pos: The file position
471 * @len: The length of the data (unused)
472 * @copied: The amount of data copied
473 * @page: The eCryptfs page
474 * @fsdata: The fsdata (unused)
475 */
ecryptfs_write_end(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned copied,struct page * page,void * fsdata)476 static int ecryptfs_write_end(struct file *file,
477 struct address_space *mapping,
478 loff_t pos, unsigned len, unsigned copied,
479 struct page *page, void *fsdata)
480 {
481 pgoff_t index = pos >> PAGE_SHIFT;
482 unsigned from = pos & (PAGE_SIZE - 1);
483 unsigned to = from + copied;
484 struct inode *ecryptfs_inode = mapping->host;
485 struct ecryptfs_crypt_stat *crypt_stat =
486 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
487 int rc;
488
489 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
490 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
491 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
492 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
493 to);
494 if (!rc) {
495 rc = copied;
496 fsstack_copy_inode_size(ecryptfs_inode,
497 ecryptfs_inode_to_lower(ecryptfs_inode));
498 }
499 goto out;
500 }
501 if (!PageUptodate(page)) {
502 if (copied < PAGE_SIZE) {
503 rc = 0;
504 goto out;
505 }
506 SetPageUptodate(page);
507 }
508 /* Fills in zeros if 'to' goes beyond inode size */
509 rc = fill_zeros_to_end_of_page(page, to);
510 if (rc) {
511 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
512 "zeros in page with index = [0x%.16lx]\n", index);
513 goto out;
514 }
515 rc = ecryptfs_encrypt_page(page);
516 if (rc) {
517 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
518 "index [0x%.16lx])\n", index);
519 goto out;
520 }
521 if (pos + copied > i_size_read(ecryptfs_inode)) {
522 i_size_write(ecryptfs_inode, pos + copied);
523 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
524 "[0x%.16llx]\n",
525 (unsigned long long)i_size_read(ecryptfs_inode));
526 }
527 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
528 if (rc)
529 printk(KERN_ERR "Error writing inode size to metadata; "
530 "rc = [%d]\n", rc);
531 else
532 rc = copied;
533 out:
534 unlock_page(page);
535 put_page(page);
536 return rc;
537 }
538
ecryptfs_bmap(struct address_space * mapping,sector_t block)539 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
540 {
541 int rc = 0;
542 struct inode *inode;
543 struct inode *lower_inode;
544
545 inode = (struct inode *)mapping->host;
546 lower_inode = ecryptfs_inode_to_lower(inode);
547 if (lower_inode->i_mapping->a_ops->bmap)
548 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
549 block);
550 return rc;
551 }
552
553 const struct address_space_operations ecryptfs_aops = {
554 .writepage = ecryptfs_writepage,
555 .readpage = ecryptfs_readpage,
556 .write_begin = ecryptfs_write_begin,
557 .write_end = ecryptfs_write_end,
558 .bmap = ecryptfs_bmap,
559 };
560