5a30e01547f1e8aebf23c4545006f2d2e95e8174
[linux-2.6.git] / fs / ecryptfs / mmap.c
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/crypto.h>
34 #include <linux/scatterlist.h>
35 #include <asm/unaligned.h>
36 #include "ecryptfs_kernel.h"
37
38 /**
39  * ecryptfs_get_locked_page
40  *
41  * Get one page from cache or lower f/s, return error otherwise.
42  *
43  * Returns locked and up-to-date page (if ok), with increased
44  * refcnt.
45  */
46 struct page *ecryptfs_get_locked_page(struct file *file, loff_t index)
47 {
48         struct dentry *dentry;
49         struct inode *inode;
50         struct address_space *mapping;
51         struct page *page;
52
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);
57         if (!IS_ERR(page))
58                 lock_page(page);
59         return page;
60 }
61
62 /**
63  * ecryptfs_writepage
64  * @page: Page that is locked before this call is made
65  *
66  * Returns zero on success; non-zero otherwise
67  */
68 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
69 {
70         int rc;
71
72         rc = ecryptfs_encrypt_page(page);
73         if (rc) {
74                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
75                                 "page (upper index [0x%.16x])\n", page->index);
76                 ClearPageUptodate(page);
77                 goto out;
78         }
79         SetPageUptodate(page);
80         unlock_page(page);
81 out:
82         return rc;
83 }
84
85 /**
86  *   Header Extent:
87  *     Octets 0-7:        Unencrypted file size (big-endian)
88  *     Octets 8-15:       eCryptfs special marker
89  *     Octets 16-19:      Flags
90  *      Octet 16:         File format version number (between 0 and 255)
91  *      Octets 17-18:     Reserved
92  *      Octet 19:         Bit 1 (lsb): Reserved
93  *                        Bit 2: Encrypted?
94  *                        Bits 3-8: Reserved
95  *     Octets 20-23:      Header extent size (big-endian)
96  *     Octets 24-25:      Number of header extents at front of file
97  *                        (big-endian)
98  *     Octet  26:         Begin RFC 2440 authentication token packet set
99  */
100
101 /**
102  * ecryptfs_copy_up_encrypted_with_header
103  * @page: Sort of a ``virtual'' representation of the encrypted lower
104  *        file. The actual lower file does not have the metadata in
105  *        the header. This is locked.
106  * @crypt_stat: The eCryptfs inode's cryptographic context
107  *
108  * The ``view'' is the version of the file that userspace winds up
109  * seeing, with the header information inserted.
110  */
111 static int
112 ecryptfs_copy_up_encrypted_with_header(struct page *page,
113                                        struct ecryptfs_crypt_stat *crypt_stat)
114 {
115         loff_t extent_num_in_page = 0;
116         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
117                                        / crypt_stat->extent_size);
118         int rc = 0;
119
120         while (extent_num_in_page < num_extents_per_page) {
121                 loff_t view_extent_num = ((((loff_t)page->index)
122                                            * num_extents_per_page)
123                                           + extent_num_in_page);
124                 size_t num_header_extents_at_front =
125                         (crypt_stat->num_header_bytes_at_front
126                          / crypt_stat->extent_size);
127
128                 if (view_extent_num < num_header_extents_at_front) {
129                         /* This is a header extent */
130                         char *page_virt;
131
132                         page_virt = kmap_atomic(page, KM_USER0);
133                         memset(page_virt, 0, PAGE_CACHE_SIZE);
134                         /* TODO: Support more than one header extent */
135                         if (view_extent_num == 0) {
136                                 size_t written;
137
138                                 rc = ecryptfs_read_xattr_region(
139                                         page_virt, page->mapping->host);
140                                 ecryptfs_write_header_metadata(page_virt + 20,
141                                                                crypt_stat,
142                                                                &written);
143                         }
144                         kunmap_atomic(page_virt, KM_USER0);
145                         flush_dcache_page(page);
146                         if (rc) {
147                                 printk(KERN_ERR "%s: Error reading xattr "
148                                        "region; rc = [%d]\n", __func__, rc);
149                                 goto out;
150                         }
151                 } else {
152                         /* This is an encrypted data extent */
153                         loff_t lower_offset =
154                                 ((view_extent_num * crypt_stat->extent_size)
155                                  - crypt_stat->num_header_bytes_at_front);
156
157                         rc = ecryptfs_read_lower_page_segment(
158                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
159                                 (lower_offset & ~PAGE_CACHE_MASK),
160                                 crypt_stat->extent_size, page->mapping->host);
161                         if (rc) {
162                                 printk(KERN_ERR "%s: Error attempting to read "
163                                        "extent at offset [%lld] in the lower "
164                                        "file; rc = [%d]\n", __func__,
165                                        lower_offset, rc);
166                                 goto out;
167                         }
168                 }
169                 extent_num_in_page++;
170         }
171 out:
172         return rc;
173 }
174
175 /**
176  * ecryptfs_readpage
177  * @file: An eCryptfs file
178  * @page: Page from eCryptfs inode mapping into which to stick the read data
179  *
180  * Read in a page, decrypting if necessary.
181  *
182  * Returns zero on success; non-zero on error.
183  */
184 static int ecryptfs_readpage(struct file *file, struct page *page)
185 {
186         struct ecryptfs_crypt_stat *crypt_stat =
187                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
188         int rc = 0;
189
190         if (!crypt_stat
191             || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
192             || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
193                 ecryptfs_printk(KERN_DEBUG,
194                                 "Passing through unencrypted page\n");
195                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
196                                                       PAGE_CACHE_SIZE,
197                                                       page->mapping->host);
198         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
199                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
200                         rc = ecryptfs_copy_up_encrypted_with_header(page,
201                                                                     crypt_stat);
202                         if (rc) {
203                                 printk(KERN_ERR "%s: Error attempting to copy "
204                                        "the encrypted content from the lower "
205                                        "file whilst inserting the metadata "
206                                        "from the xattr into the header; rc = "
207                                        "[%d]\n", __func__, rc);
208                                 goto out;
209                         }
210
211                 } else {
212                         rc = ecryptfs_read_lower_page_segment(
213                                 page, page->index, 0, PAGE_CACHE_SIZE,
214                                 page->mapping->host);
215                         if (rc) {
216                                 printk(KERN_ERR "Error reading page; rc = "
217                                        "[%d]\n", rc);
218                                 goto out;
219                         }
220                 }
221         } else {
222                 rc = ecryptfs_decrypt_page(page);
223                 if (rc) {
224                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
225                                         "rc = [%d]\n", rc);
226                         goto out;
227                 }
228         }
229 out:
230         if (rc)
231                 ClearPageUptodate(page);
232         else
233                 SetPageUptodate(page);
234         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
235                         page->index);
236         unlock_page(page);
237         return rc;
238 }
239
240 /**
241  * Called with lower inode mutex held.
242  */
243 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
244 {
245         struct inode *inode = page->mapping->host;
246         int end_byte_in_page;
247
248         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
249                 goto out;
250         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
251         if (to > end_byte_in_page)
252                 end_byte_in_page = to;
253         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
254 out:
255         return 0;
256 }
257
258 /**
259  * ecryptfs_write_begin
260  * @file: The eCryptfs file
261  * @mapping: The eCryptfs object
262  * @pos: The file offset at which to start writing
263  * @len: Length of the write
264  * @flags: Various flags
265  * @pagep: Pointer to return the page
266  * @fsdata: Pointer to return fs data (unused)
267  *
268  * This function must zero any hole we create
269  *
270  * Returns zero on success; non-zero otherwise
271  */
272 static int ecryptfs_write_begin(struct file *file,
273                         struct address_space *mapping,
274                         loff_t pos, unsigned len, unsigned flags,
275                         struct page **pagep, void **fsdata)
276 {
277         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
278         struct page *page;
279         loff_t prev_page_end_size;
280         int rc = 0;
281
282         page = grab_cache_page_write_begin(mapping, index, flags);
283         if (!page)
284                 return -ENOMEM;
285         *pagep = page;
286
287         if (!PageUptodate(page)) {
288                 struct ecryptfs_crypt_stat *crypt_stat =
289                         &ecryptfs_inode_to_private(
290                                 file->f_path.dentry->d_inode)->crypt_stat;
291
292                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
293                     || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
294                         rc = ecryptfs_read_lower_page_segment(
295                                 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
296                         if (rc) {
297                                 printk(KERN_ERR "%s: Error attemping to read "
298                                        "lower page segment; rc = [%d]\n",
299                                        __func__, rc);
300                                 ClearPageUptodate(page);
301                                 goto out;
302                         } else
303                                 SetPageUptodate(page);
304                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
305                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
306                                 rc = ecryptfs_copy_up_encrypted_with_header(
307                                         page, crypt_stat);
308                                 if (rc) {
309                                         printk(KERN_ERR "%s: Error attempting "
310                                                "to copy the encrypted content "
311                                                "from the lower file whilst "
312                                                "inserting the metadata from "
313                                                "the xattr into the header; rc "
314                                                "= [%d]\n", __func__, rc);
315                                         ClearPageUptodate(page);
316                                         goto out;
317                                 }
318                                 SetPageUptodate(page);
319                         } else {
320                                 rc = ecryptfs_read_lower_page_segment(
321                                         page, index, 0, PAGE_CACHE_SIZE,
322                                         mapping->host);
323                                 if (rc) {
324                                         printk(KERN_ERR "%s: Error reading "
325                                                "page; rc = [%d]\n",
326                                                __func__, rc);
327                                         ClearPageUptodate(page);
328                                         goto out;
329                                 }
330                                 SetPageUptodate(page);
331                         }
332                 } else {
333                         rc = ecryptfs_decrypt_page(page);
334                         if (rc) {
335                                 printk(KERN_ERR "%s: Error decrypting page "
336                                        "at index [%ld]; rc = [%d]\n",
337                                        __func__, page->index, rc);
338                                 ClearPageUptodate(page);
339                                 goto out;
340                         }
341                         SetPageUptodate(page);
342                 }
343         }
344         prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
345         /* If creating a page or more of holes, zero them out via truncate.
346          * Note, this will increase i_size. */
347         if (index != 0) {
348                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
349                         rc = ecryptfs_truncate(file->f_path.dentry,
350                                                prev_page_end_size);
351                         if (rc) {
352                                 printk(KERN_ERR "%s: Error on attempt to "
353                                        "truncate to (higher) offset [%lld];"
354                                        " rc = [%d]\n", __func__,
355                                        prev_page_end_size, rc);
356                                 goto out;
357                         }
358                 }
359         }
360         /* Writing to a new page, and creating a small hole from start
361          * of page?  Zero it out. */
362         if ((i_size_read(mapping->host) == prev_page_end_size)
363             && (pos != 0))
364                 zero_user(page, 0, PAGE_CACHE_SIZE);
365 out:
366         return rc;
367 }
368
369 /**
370  * ecryptfs_write_inode_size_to_header
371  *
372  * Writes the lower file size to the first 8 bytes of the header.
373  *
374  * Returns zero on success; non-zero on error.
375  */
376 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
377 {
378         char *file_size_virt;
379         int rc;
380
381         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
382         if (!file_size_virt) {
383                 rc = -ENOMEM;
384                 goto out;
385         }
386         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
387         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
388                                   sizeof(u64));
389         kfree(file_size_virt);
390         if (rc < 0)
391                 printk(KERN_ERR "%s: Error writing file size to header; "
392                        "rc = [%d]\n", __func__, rc);
393         else
394                 rc = 0;
395 out:
396         return rc;
397 }
398
399 struct kmem_cache *ecryptfs_xattr_cache;
400
401 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
402 {
403         ssize_t size;
404         void *xattr_virt;
405         struct dentry *lower_dentry =
406                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
407         struct inode *lower_inode = lower_dentry->d_inode;
408         int rc;
409
410         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
411                 printk(KERN_WARNING
412                        "No support for setting xattr in lower filesystem\n");
413                 rc = -ENOSYS;
414                 goto out;
415         }
416         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
417         if (!xattr_virt) {
418                 printk(KERN_ERR "Out of memory whilst attempting to write "
419                        "inode size to xattr\n");
420                 rc = -ENOMEM;
421                 goto out;
422         }
423         mutex_lock(&lower_inode->i_mutex);
424         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
425                                            xattr_virt, PAGE_CACHE_SIZE);
426         if (size < 0)
427                 size = 8;
428         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
429         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
430                                          xattr_virt, size, 0);
431         mutex_unlock(&lower_inode->i_mutex);
432         if (rc)
433                 printk(KERN_ERR "Error whilst attempting to write inode size "
434                        "to lower file xattr; rc = [%d]\n", rc);
435         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
436 out:
437         return rc;
438 }
439
440 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
441 {
442         struct ecryptfs_crypt_stat *crypt_stat;
443
444         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
445         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
446         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
447                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
448         else
449                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
450 }
451
452 /**
453  * ecryptfs_write_end
454  * @file: The eCryptfs file object
455  * @mapping: The eCryptfs object
456  * @pos: The file position
457  * @len: The length of the data (unused)
458  * @copied: The amount of data copied
459  * @page: The eCryptfs page
460  * @fsdata: The fsdata (unused)
461  *
462  * This is where we encrypt the data and pass the encrypted data to
463  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
464  * entire underlying packets.
465  */
466 static int ecryptfs_write_end(struct file *file,
467                         struct address_space *mapping,
468                         loff_t pos, unsigned len, unsigned copied,
469                         struct page *page, void *fsdata)
470 {
471         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
472         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
473         unsigned to = from + copied;
474         struct inode *ecryptfs_inode = mapping->host;
475         struct ecryptfs_crypt_stat *crypt_stat =
476                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
477         int rc;
478
479         if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
480                 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
481                         "crypt_stat at memory location [%p]\n", crypt_stat);
482                 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
483         } else
484                 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
485         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
486                         "(page w/ index = [0x%.16x], to = [%d])\n", index, to);
487         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
488                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
489                                                        to);
490                 if (!rc) {
491                         rc = copied;
492                         fsstack_copy_inode_size(ecryptfs_inode,
493                                 ecryptfs_inode_to_lower(ecryptfs_inode));
494                 }
495                 goto out;
496         }
497         /* Fills in zeros if 'to' goes beyond inode size */
498         rc = fill_zeros_to_end_of_page(page, to);
499         if (rc) {
500                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
501                         "zeros in page with index = [0x%.16x]\n", index);
502                 goto out;
503         }
504         rc = ecryptfs_encrypt_page(page);
505         if (rc) {
506                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
507                                 "index [0x%.16x])\n", index);
508                 goto out;
509         }
510         if (pos + copied > i_size_read(ecryptfs_inode)) {
511                 i_size_write(ecryptfs_inode, pos + copied);
512                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
513                                 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
514         }
515         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
516         if (rc)
517                 printk(KERN_ERR "Error writing inode size to metadata; "
518                        "rc = [%d]\n", rc);
519         else
520                 rc = copied;
521 out:
522         unlock_page(page);
523         page_cache_release(page);
524         return rc;
525 }
526
527 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
528 {
529         int rc = 0;
530         struct inode *inode;
531         struct inode *lower_inode;
532
533         inode = (struct inode *)mapping->host;
534         lower_inode = ecryptfs_inode_to_lower(inode);
535         if (lower_inode->i_mapping->a_ops->bmap)
536                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
537                                                          block);
538         return rc;
539 }
540
541 const struct address_space_operations ecryptfs_aops = {
542         .writepage = ecryptfs_writepage,
543         .readpage = ecryptfs_readpage,
544         .write_begin = ecryptfs_write_begin,
545         .write_end = ecryptfs_write_end,
546         .bmap = ecryptfs_bmap,
547 };