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);
85 static void strip_xattr_flag(char *page_virt,
86 struct ecryptfs_crypt_stat *crypt_stat)
88 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
91 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
92 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
94 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
100 * Octets 0-7: Unencrypted file size (big-endian)
101 * Octets 8-15: eCryptfs special marker
102 * Octets 16-19: Flags
103 * Octet 16: File format version number (between 0 and 255)
104 * Octets 17-18: Reserved
105 * Octet 19: Bit 1 (lsb): Reserved
108 * Octets 20-23: Header extent size (big-endian)
109 * Octets 24-25: Number of header extents at front of file
111 * Octet 26: Begin RFC 2440 authentication token packet set
115 * ecryptfs_copy_up_encrypted_with_header
116 * @page: Sort of a ``virtual'' representation of the encrypted lower
117 * file. The actual lower file does not have the metadata in
118 * the header. This is locked.
119 * @crypt_stat: The eCryptfs inode's cryptographic context
121 * The ``view'' is the version of the file that userspace winds up
122 * seeing, with the header information inserted.
125 ecryptfs_copy_up_encrypted_with_header(struct page *page,
126 struct ecryptfs_crypt_stat *crypt_stat)
128 loff_t extent_num_in_page = 0;
129 loff_t num_extents_per_page = (PAGE_CACHE_SIZE
130 / crypt_stat->extent_size);
133 while (extent_num_in_page < num_extents_per_page) {
134 loff_t view_extent_num = ((((loff_t)page->index)
135 * num_extents_per_page)
136 + extent_num_in_page);
137 size_t num_header_extents_at_front =
138 (crypt_stat->metadata_size / crypt_stat->extent_size);
140 if (view_extent_num < num_header_extents_at_front) {
141 /* This is a header extent */
144 page_virt = kmap_atomic(page, KM_USER0);
145 memset(page_virt, 0, PAGE_CACHE_SIZE);
146 /* TODO: Support more than one header extent */
147 if (view_extent_num == 0) {
150 rc = ecryptfs_read_xattr_region(
151 page_virt, page->mapping->host);
152 strip_xattr_flag(page_virt + 16, crypt_stat);
153 ecryptfs_write_header_metadata(page_virt + 20,
157 kunmap_atomic(page_virt, KM_USER0);
158 flush_dcache_page(page);
160 printk(KERN_ERR "%s: Error reading xattr "
161 "region; rc = [%d]\n", __func__, rc);
165 /* This is an encrypted data extent */
166 loff_t lower_offset =
167 ((view_extent_num * crypt_stat->extent_size)
168 - crypt_stat->metadata_size);
170 rc = ecryptfs_read_lower_page_segment(
171 page, (lower_offset >> PAGE_CACHE_SHIFT),
172 (lower_offset & ~PAGE_CACHE_MASK),
173 crypt_stat->extent_size, page->mapping->host);
175 printk(KERN_ERR "%s: Error attempting to read "
176 "extent at offset [%lld] in the lower "
177 "file; rc = [%d]\n", __func__,
182 extent_num_in_page++;
190 * @file: An eCryptfs file
191 * @page: Page from eCryptfs inode mapping into which to stick the read data
193 * Read in a page, decrypting if necessary.
195 * Returns zero on success; non-zero on error.
197 static int ecryptfs_readpage(struct file *file, struct page *page)
199 struct ecryptfs_crypt_stat *crypt_stat =
200 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
204 || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
205 || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
206 ecryptfs_printk(KERN_DEBUG,
207 "Passing through unencrypted page\n");
208 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
210 page->mapping->host);
211 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
212 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
213 rc = ecryptfs_copy_up_encrypted_with_header(page,
216 printk(KERN_ERR "%s: Error attempting to copy "
217 "the encrypted content from the lower "
218 "file whilst inserting the metadata "
219 "from the xattr into the header; rc = "
220 "[%d]\n", __func__, rc);
225 rc = ecryptfs_read_lower_page_segment(
226 page, page->index, 0, PAGE_CACHE_SIZE,
227 page->mapping->host);
229 printk(KERN_ERR "Error reading page; rc = "
235 rc = ecryptfs_decrypt_page(page);
237 ecryptfs_printk(KERN_ERR, "Error decrypting page; "
244 ClearPageUptodate(page);
246 SetPageUptodate(page);
247 ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
254 * Called with lower inode mutex held.
256 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
258 struct inode *inode = page->mapping->host;
259 int end_byte_in_page;
261 if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
263 end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
264 if (to > end_byte_in_page)
265 end_byte_in_page = to;
266 zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
272 * ecryptfs_write_begin
273 * @file: The eCryptfs file
274 * @mapping: The eCryptfs object
275 * @pos: The file offset at which to start writing
276 * @len: Length of the write
277 * @flags: Various flags
278 * @pagep: Pointer to return the page
279 * @fsdata: Pointer to return fs data (unused)
281 * This function must zero any hole we create
283 * Returns zero on success; non-zero otherwise
285 static int ecryptfs_write_begin(struct file *file,
286 struct address_space *mapping,
287 loff_t pos, unsigned len, unsigned flags,
288 struct page **pagep, void **fsdata)
290 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
292 loff_t prev_page_end_size;
295 page = grab_cache_page_write_begin(mapping, index, flags);
300 if (!PageUptodate(page)) {
301 struct ecryptfs_crypt_stat *crypt_stat =
302 &ecryptfs_inode_to_private(
303 file->f_path.dentry->d_inode)->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(file->f_path.dentry->d_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,