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 inode *inode, loff_t index)
49 struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
57 * @page: Page that is locked before this call is made
59 * Returns zero on success; non-zero otherwise
61 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
65 rc = ecryptfs_encrypt_page(page);
67 ecryptfs_printk(KERN_WARNING, "Error encrypting "
68 "page (upper index [0x%.16x])\n", page->index);
69 ClearPageUptodate(page);
72 SetPageUptodate(page);
78 static void strip_xattr_flag(char *page_virt,
79 struct ecryptfs_crypt_stat *crypt_stat)
81 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
84 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
85 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
87 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
93 * Octets 0-7: Unencrypted file size (big-endian)
94 * Octets 8-15: eCryptfs special marker
96 * Octet 16: File format version number (between 0 and 255)
97 * Octets 17-18: Reserved
98 * Octet 19: Bit 1 (lsb): Reserved
101 * Octets 20-23: Header extent size (big-endian)
102 * Octets 24-25: Number of header extents at front of file
104 * Octet 26: Begin RFC 2440 authentication token packet set
108 * ecryptfs_copy_up_encrypted_with_header
109 * @page: Sort of a ``virtual'' representation of the encrypted lower
110 * file. The actual lower file does not have the metadata in
111 * the header. This is locked.
112 * @crypt_stat: The eCryptfs inode's cryptographic context
114 * The ``view'' is the version of the file that userspace winds up
115 * seeing, with the header information inserted.
118 ecryptfs_copy_up_encrypted_with_header(struct page *page,
119 struct ecryptfs_crypt_stat *crypt_stat)
121 loff_t extent_num_in_page = 0;
122 loff_t num_extents_per_page = (PAGE_CACHE_SIZE
123 / crypt_stat->extent_size);
126 while (extent_num_in_page < num_extents_per_page) {
127 loff_t view_extent_num = ((((loff_t)page->index)
128 * num_extents_per_page)
129 + extent_num_in_page);
130 size_t num_header_extents_at_front =
131 (crypt_stat->metadata_size / crypt_stat->extent_size);
133 if (view_extent_num < num_header_extents_at_front) {
134 /* This is a header extent */
137 page_virt = kmap_atomic(page, KM_USER0);
138 memset(page_virt, 0, PAGE_CACHE_SIZE);
139 /* TODO: Support more than one header extent */
140 if (view_extent_num == 0) {
143 rc = ecryptfs_read_xattr_region(
144 page_virt, page->mapping->host);
145 strip_xattr_flag(page_virt + 16, crypt_stat);
146 ecryptfs_write_header_metadata(page_virt + 20,
150 kunmap_atomic(page_virt, KM_USER0);
151 flush_dcache_page(page);
153 printk(KERN_ERR "%s: Error reading xattr "
154 "region; rc = [%d]\n", __func__, rc);
158 /* This is an encrypted data extent */
159 loff_t lower_offset =
160 ((view_extent_num * crypt_stat->extent_size)
161 - crypt_stat->metadata_size);
163 rc = ecryptfs_read_lower_page_segment(
164 page, (lower_offset >> PAGE_CACHE_SHIFT),
165 (lower_offset & ~PAGE_CACHE_MASK),
166 crypt_stat->extent_size, page->mapping->host);
168 printk(KERN_ERR "%s: Error attempting to read "
169 "extent at offset [%lld] in the lower "
170 "file; rc = [%d]\n", __func__,
175 extent_num_in_page++;
183 * @file: An eCryptfs file
184 * @page: Page from eCryptfs inode mapping into which to stick the read data
186 * Read in a page, decrypting if necessary.
188 * Returns zero on success; non-zero on error.
190 static int ecryptfs_readpage(struct file *file, struct page *page)
192 struct ecryptfs_crypt_stat *crypt_stat =
193 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
197 || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
198 || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
199 ecryptfs_printk(KERN_DEBUG,
200 "Passing through unencrypted page\n");
201 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
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,
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);
218 rc = ecryptfs_read_lower_page_segment(
219 page, page->index, 0, PAGE_CACHE_SIZE,
220 page->mapping->host);
222 printk(KERN_ERR "Error reading page; rc = "
228 rc = ecryptfs_decrypt_page(page);
230 ecryptfs_printk(KERN_ERR, "Error decrypting page; "
237 ClearPageUptodate(page);
239 SetPageUptodate(page);
240 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
247 * Called with lower inode mutex held.
249 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
251 struct inode *inode = page->mapping->host;
252 int end_byte_in_page;
254 if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
256 end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
257 if (to > end_byte_in_page)
258 end_byte_in_page = to;
259 zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
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)
274 * This function must zero any hole we create
276 * Returns zero on success; non-zero otherwise
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)
283 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
285 loff_t prev_page_end_size;
288 page = grab_cache_page_write_begin(mapping, index, flags);
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 || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
299 rc = ecryptfs_read_lower_page_segment(
300 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
302 printk(KERN_ERR "%s: Error attemping to read "
303 "lower page segment; rc = [%d]\n",
305 ClearPageUptodate(page);
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(
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);
323 SetPageUptodate(page);
325 rc = ecryptfs_read_lower_page_segment(
326 page, index, 0, PAGE_CACHE_SIZE,
329 printk(KERN_ERR "%s: Error reading "
332 ClearPageUptodate(page);
335 SetPageUptodate(page);
338 rc = ecryptfs_decrypt_page(page);
340 printk(KERN_ERR "%s: Error decrypting page "
341 "at index [%ld]; rc = [%d]\n",
342 __func__, page->index, rc);
343 ClearPageUptodate(page);
346 SetPageUptodate(page);
349 prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
350 /* If creating a page or more of holes, zero them out via truncate.
351 * Note, this will increase i_size. */
353 if (prev_page_end_size > i_size_read(page->mapping->host)) {
354 rc = ecryptfs_truncate(file->f_path.dentry,
357 printk(KERN_ERR "%s: Error on attempt to "
358 "truncate to (higher) offset [%lld];"
359 " rc = [%d]\n", __func__,
360 prev_page_end_size, rc);
365 /* Writing to a new page, and creating a small hole from start
366 * of page? Zero it out. */
367 if ((i_size_read(mapping->host) == prev_page_end_size)
369 zero_user(page, 0, PAGE_CACHE_SIZE);
375 * ecryptfs_write_inode_size_to_header
377 * Writes the lower file size to the first 8 bytes of the header.
379 * Returns zero on success; non-zero on error.
381 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
383 char *file_size_virt;
386 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
387 if (!file_size_virt) {
391 put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
392 rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
394 kfree(file_size_virt);
396 printk(KERN_ERR "%s: Error writing file size to header; "
397 "rc = [%d]\n", __func__, rc);
404 struct kmem_cache *ecryptfs_xattr_cache;
406 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
410 struct dentry *lower_dentry =
411 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
412 struct inode *lower_inode = lower_dentry->d_inode;
415 if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
417 "No support for setting xattr in lower filesystem\n");
421 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
423 printk(KERN_ERR "Out of memory whilst attempting to write "
424 "inode size to xattr\n");
428 mutex_lock(&lower_inode->i_mutex);
429 size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
430 xattr_virt, PAGE_CACHE_SIZE);
433 put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
434 rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
435 xattr_virt, size, 0);
436 mutex_unlock(&lower_inode->i_mutex);
438 printk(KERN_ERR "Error whilst attempting to write inode size "
439 "to lower file xattr; rc = [%d]\n", rc);
440 kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
445 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
447 struct ecryptfs_crypt_stat *crypt_stat;
449 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
450 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
451 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
452 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
454 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
459 * @file: The eCryptfs file object
460 * @mapping: The eCryptfs object
461 * @pos: The file position
462 * @len: The length of the data (unused)
463 * @copied: The amount of data copied
464 * @page: The eCryptfs page
465 * @fsdata: The fsdata (unused)
467 * This is where we encrypt the data and pass the encrypted data to
468 * the lower filesystem. In OpenPGP-compatible mode, we operate on
469 * entire underlying packets.
471 static int ecryptfs_write_end(struct file *file,
472 struct address_space *mapping,
473 loff_t pos, unsigned len, unsigned copied,
474 struct page *page, void *fsdata)
476 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
477 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
478 unsigned to = from + copied;
479 struct inode *ecryptfs_inode = mapping->host;
480 struct ecryptfs_crypt_stat *crypt_stat =
481 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
484 if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
485 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
486 "crypt_stat at memory location [%p]\n", crypt_stat);
487 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
489 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
490 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
491 "(page w/ index = [0x%.16x], 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 /* Fills in zeros if 'to' goes beyond inode size */
503 rc = fill_zeros_to_end_of_page(page, to);
505 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
506 "zeros in page with index = [0x%.16x]\n", index);
509 rc = ecryptfs_encrypt_page(page);
511 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
512 "index [0x%.16x])\n", index);
515 if (pos + copied > i_size_read(ecryptfs_inode)) {
516 i_size_write(ecryptfs_inode, pos + copied);
517 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
518 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
520 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
522 printk(KERN_ERR "Error writing inode size to metadata; "
528 page_cache_release(page);
532 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
536 struct inode *lower_inode;
538 inode = (struct inode *)mapping->host;
539 lower_inode = ecryptfs_inode_to_lower(inode);
540 if (lower_inode->i_mapping->a_ops->bmap)
541 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
546 const struct address_space_operations ecryptfs_aops = {
547 .writepage = ecryptfs_writepage,
548 .readpage = ecryptfs_readpage,
549 .write_begin = ecryptfs_write_begin,
550 .write_end = ecryptfs_write_end,
551 .bmap = ecryptfs_bmap,