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/scatterlist.h>
34 #include <linux/slab.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 inode *inode, loff_t index)
48 struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
56 * @page: Page that is locked before this call is made
58 * Returns zero on success; non-zero otherwise
60 * This is where we encrypt the data and pass the encrypted data to
61 * the lower filesystem. In OpenPGP-compatible mode, we operate on
62 * entire underlying packets.
64 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
68 rc = ecryptfs_encrypt_page(page);
70 ecryptfs_printk(KERN_WARNING, "Error encrypting "
71 "page (upper index [0x%.16lx])\n", page->index);
72 ClearPageUptodate(page);
75 SetPageUptodate(page);
81 static void strip_xattr_flag(char *page_virt,
82 struct ecryptfs_crypt_stat *crypt_stat)
84 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
87 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
88 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
90 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
96 * Octets 0-7: Unencrypted file size (big-endian)
97 * Octets 8-15: eCryptfs special marker
99 * Octet 16: File format version number (between 0 and 255)
100 * Octets 17-18: Reserved
101 * Octet 19: Bit 1 (lsb): Reserved
104 * Octets 20-23: Header extent size (big-endian)
105 * Octets 24-25: Number of header extents at front of file
107 * Octet 26: Begin RFC 2440 authentication token packet set
111 * ecryptfs_copy_up_encrypted_with_header
112 * @page: Sort of a ``virtual'' representation of the encrypted lower
113 * file. The actual lower file does not have the metadata in
114 * the header. This is locked.
115 * @crypt_stat: The eCryptfs inode's cryptographic context
117 * The ``view'' is the version of the file that userspace winds up
118 * seeing, with the header information inserted.
121 ecryptfs_copy_up_encrypted_with_header(struct page *page,
122 struct ecryptfs_crypt_stat *crypt_stat)
124 loff_t extent_num_in_page = 0;
125 loff_t num_extents_per_page = (PAGE_CACHE_SIZE
126 / crypt_stat->extent_size);
129 while (extent_num_in_page < num_extents_per_page) {
130 loff_t view_extent_num = ((((loff_t)page->index)
131 * num_extents_per_page)
132 + extent_num_in_page);
133 size_t num_header_extents_at_front =
134 (crypt_stat->metadata_size / crypt_stat->extent_size);
136 if (view_extent_num < num_header_extents_at_front) {
137 /* This is a header extent */
140 page_virt = kmap_atomic(page);
141 memset(page_virt, 0, PAGE_CACHE_SIZE);
142 /* TODO: Support more than one header extent */
143 if (view_extent_num == 0) {
146 rc = ecryptfs_read_xattr_region(
147 page_virt, page->mapping->host);
148 strip_xattr_flag(page_virt + 16, crypt_stat);
149 ecryptfs_write_header_metadata(page_virt + 20,
153 kunmap_atomic(page_virt);
154 flush_dcache_page(page);
156 printk(KERN_ERR "%s: Error reading xattr "
157 "region; rc = [%d]\n", __func__, rc);
161 /* This is an encrypted data extent */
162 loff_t lower_offset =
163 ((view_extent_num * crypt_stat->extent_size)
164 - crypt_stat->metadata_size);
166 rc = ecryptfs_read_lower_page_segment(
167 page, (lower_offset >> PAGE_CACHE_SHIFT),
168 (lower_offset & ~PAGE_CACHE_MASK),
169 crypt_stat->extent_size, page->mapping->host);
171 printk(KERN_ERR "%s: Error attempting to read "
172 "extent at offset [%lld] in the lower "
173 "file; rc = [%d]\n", __func__,
178 extent_num_in_page++;
186 * @file: An eCryptfs file
187 * @page: Page from eCryptfs inode mapping into which to stick the read data
189 * Read in a page, decrypting if necessary.
191 * Returns zero on success; non-zero on error.
193 static int ecryptfs_readpage(struct file *file, struct page *page)
195 struct ecryptfs_crypt_stat *crypt_stat =
196 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
199 if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
200 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
202 page->mapping->host);
203 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
204 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
205 rc = ecryptfs_copy_up_encrypted_with_header(page,
208 printk(KERN_ERR "%s: Error attempting to copy "
209 "the encrypted content from the lower "
210 "file whilst inserting the metadata "
211 "from the xattr into the header; rc = "
212 "[%d]\n", __func__, rc);
217 rc = ecryptfs_read_lower_page_segment(
218 page, page->index, 0, PAGE_CACHE_SIZE,
219 page->mapping->host);
221 printk(KERN_ERR "Error reading page; rc = "
227 rc = ecryptfs_decrypt_page(page);
229 ecryptfs_printk(KERN_ERR, "Error decrypting page; "
236 ClearPageUptodate(page);
238 SetPageUptodate(page);
239 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
246 * Called with lower inode mutex held.
248 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
250 struct inode *inode = page->mapping->host;
251 int end_byte_in_page;
253 if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
255 end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
256 if (to > end_byte_in_page)
257 end_byte_in_page = to;
258 zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
264 * ecryptfs_write_begin
265 * @file: The eCryptfs file
266 * @mapping: The eCryptfs object
267 * @pos: The file offset at which to start writing
268 * @len: Length of the write
269 * @flags: Various flags
270 * @pagep: Pointer to return the page
271 * @fsdata: Pointer to return fs data (unused)
273 * This function must zero any hole we create
275 * Returns zero on success; non-zero otherwise
277 static int ecryptfs_write_begin(struct file *file,
278 struct address_space *mapping,
279 loff_t pos, unsigned len, unsigned flags,
280 struct page **pagep, void **fsdata)
282 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
284 loff_t prev_page_end_size;
287 page = grab_cache_page_write_begin(mapping, index, flags);
292 prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
293 if (!PageUptodate(page)) {
294 struct ecryptfs_crypt_stat *crypt_stat =
295 &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
297 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
298 rc = ecryptfs_read_lower_page_segment(
299 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
301 printk(KERN_ERR "%s: Error attempting to read "
302 "lower page segment; rc = [%d]\n",
304 ClearPageUptodate(page);
307 SetPageUptodate(page);
308 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
309 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
310 rc = ecryptfs_copy_up_encrypted_with_header(
313 printk(KERN_ERR "%s: Error attempting "
314 "to copy the encrypted content "
315 "from the lower file whilst "
316 "inserting the metadata from "
317 "the xattr into the header; rc "
318 "= [%d]\n", __func__, rc);
319 ClearPageUptodate(page);
322 SetPageUptodate(page);
324 rc = ecryptfs_read_lower_page_segment(
325 page, index, 0, PAGE_CACHE_SIZE,
328 printk(KERN_ERR "%s: Error reading "
331 ClearPageUptodate(page);
334 SetPageUptodate(page);
337 if (prev_page_end_size
338 >= i_size_read(page->mapping->host)) {
339 zero_user(page, 0, PAGE_CACHE_SIZE);
340 SetPageUptodate(page);
341 } else if (len < PAGE_CACHE_SIZE) {
342 rc = ecryptfs_decrypt_page(page);
344 printk(KERN_ERR "%s: Error decrypting "
345 "page at index [%ld]; "
347 __func__, page->index, rc);
348 ClearPageUptodate(page);
351 SetPageUptodate(page);
355 /* If creating a page or more of holes, zero them out via truncate.
356 * Note, this will increase i_size. */
358 if (prev_page_end_size > i_size_read(page->mapping->host)) {
359 rc = ecryptfs_truncate(file->f_path.dentry,
362 printk(KERN_ERR "%s: Error on attempt to "
363 "truncate to (higher) offset [%lld];"
364 " rc = [%d]\n", __func__,
365 prev_page_end_size, rc);
370 /* Writing to a new page, and creating a small hole from start
371 * of page? Zero it out. */
372 if ((i_size_read(mapping->host) == prev_page_end_size)
374 zero_user(page, 0, PAGE_CACHE_SIZE);
378 page_cache_release(page);
385 * ecryptfs_write_inode_size_to_header
387 * Writes the lower file size to the first 8 bytes of the header.
389 * Returns zero on success; non-zero on error.
391 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
393 char *file_size_virt;
396 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
397 if (!file_size_virt) {
401 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
402 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
404 kfree(file_size_virt);
406 printk(KERN_ERR "%s: Error writing file size to header; "
407 "rc = [%d]\n", __func__, rc);
414 struct kmem_cache *ecryptfs_xattr_cache;
416 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
420 struct dentry *lower_dentry =
421 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
422 struct inode *lower_inode = d_inode(lower_dentry);
425 if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
427 "No support for setting xattr in lower filesystem\n");
431 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
433 printk(KERN_ERR "Out of memory whilst attempting to write "
434 "inode size to xattr\n");
438 inode_lock(lower_inode);
439 size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
440 xattr_virt, PAGE_CACHE_SIZE);
443 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
444 rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
445 xattr_virt, size, 0);
446 inode_unlock(lower_inode);
448 printk(KERN_ERR "Error whilst attempting to write inode size "
449 "to lower file xattr; rc = [%d]\n", rc);
450 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
455 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
457 struct ecryptfs_crypt_stat *crypt_stat;
459 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
460 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
461 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
462 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
464 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
469 * @file: The eCryptfs file object
470 * @mapping: The eCryptfs object
471 * @pos: The file position
472 * @len: The length of the data (unused)
473 * @copied: The amount of data copied
474 * @page: The eCryptfs page
475 * @fsdata: The fsdata (unused)
477 static int ecryptfs_write_end(struct file *file,
478 struct address_space *mapping,
479 loff_t pos, unsigned len, unsigned copied,
480 struct page *page, void *fsdata)
482 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
483 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
484 unsigned to = from + copied;
485 struct inode *ecryptfs_inode = mapping->host;
486 struct ecryptfs_crypt_stat *crypt_stat =
487 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
490 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
491 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
492 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
493 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
497 fsstack_copy_inode_size(ecryptfs_inode,
498 ecryptfs_inode_to_lower(ecryptfs_inode));
502 if (!PageUptodate(page)) {
503 if (copied < PAGE_CACHE_SIZE) {
507 SetPageUptodate(page);
509 /* Fills in zeros if 'to' goes beyond inode size */
510 rc = fill_zeros_to_end_of_page(page, to);
512 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
513 "zeros in page with index = [0x%.16lx]\n", index);
516 rc = ecryptfs_encrypt_page(page);
518 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
519 "index [0x%.16lx])\n", index);
522 if (pos + copied > i_size_read(ecryptfs_inode)) {
523 i_size_write(ecryptfs_inode, pos + copied);
524 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
526 (unsigned long long)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,