2ee9a3a7b68c4f69be50770a79bf849a79663cbe
[pandora-kernel.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 <linux/slab.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  */
47 struct page *ecryptfs_get_locked_page(struct file *file, loff_t index)
48 {
49         struct dentry *dentry;
50         struct inode *inode;
51         struct address_space *mapping;
52         struct page *page;
53
54         dentry = file->f_path.dentry;
55         inode = dentry->d_inode;
56         mapping = inode->i_mapping;
57         page = read_mapping_page(mapping, index, (void *)file);
58         if (!IS_ERR(page))
59                 lock_page(page);
60         return page;
61 }
62
63 /**
64  * ecryptfs_writepage
65  * @page: Page that is locked before this call is made
66  *
67  * Returns zero on success; non-zero otherwise
68  */
69 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
70 {
71         int rc;
72
73         rc = ecryptfs_encrypt_page(page);
74         if (rc) {
75                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
76                                 "page (upper index [0x%.16x])\n", page->index);
77                 ClearPageUptodate(page);
78                 goto out;
79         }
80         SetPageUptodate(page);
81         unlock_page(page);
82 out:
83         return rc;
84 }
85
86 static void strip_xattr_flag(char *page_virt,
87                              struct ecryptfs_crypt_stat *crypt_stat)
88 {
89         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
90                 size_t written;
91
92                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
93                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
94                                                 &written);
95                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
96         }
97 }
98
99 /**
100  *   Header Extent:
101  *     Octets 0-7:        Unencrypted file size (big-endian)
102  *     Octets 8-15:       eCryptfs special marker
103  *     Octets 16-19:      Flags
104  *      Octet 16:         File format version number (between 0 and 255)
105  *      Octets 17-18:     Reserved
106  *      Octet 19:         Bit 1 (lsb): Reserved
107  *                        Bit 2: Encrypted?
108  *                        Bits 3-8: Reserved
109  *     Octets 20-23:      Header extent size (big-endian)
110  *     Octets 24-25:      Number of header extents at front of file
111  *                        (big-endian)
112  *     Octet  26:         Begin RFC 2440 authentication token packet set
113  */
114
115 /**
116  * ecryptfs_copy_up_encrypted_with_header
117  * @page: Sort of a ``virtual'' representation of the encrypted lower
118  *        file. The actual lower file does not have the metadata in
119  *        the header. This is locked.
120  * @crypt_stat: The eCryptfs inode's cryptographic context
121  *
122  * The ``view'' is the version of the file that userspace winds up
123  * seeing, with the header information inserted.
124  */
125 static int
126 ecryptfs_copy_up_encrypted_with_header(struct page *page,
127                                        struct ecryptfs_crypt_stat *crypt_stat)
128 {
129         loff_t extent_num_in_page = 0;
130         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
131                                        / crypt_stat->extent_size);
132         int rc = 0;
133
134         while (extent_num_in_page < num_extents_per_page) {
135                 loff_t view_extent_num = ((((loff_t)page->index)
136                                            * num_extents_per_page)
137                                           + extent_num_in_page);
138                 size_t num_header_extents_at_front =
139                         (crypt_stat->metadata_size / crypt_stat->extent_size);
140
141                 if (view_extent_num < num_header_extents_at_front) {
142                         /* This is a header extent */
143                         char *page_virt;
144
145                         page_virt = kmap_atomic(page, KM_USER0);
146                         memset(page_virt, 0, PAGE_CACHE_SIZE);
147                         /* TODO: Support more than one header extent */
148                         if (view_extent_num == 0) {
149                                 size_t written;
150
151                                 rc = ecryptfs_read_xattr_region(
152                                         page_virt, page->mapping->host);
153                                 strip_xattr_flag(page_virt + 16, crypt_stat);
154                                 ecryptfs_write_header_metadata(page_virt + 20,
155                                                                crypt_stat,
156                                                                &written);
157                         }
158                         kunmap_atomic(page_virt, KM_USER0);
159                         flush_dcache_page(page);
160                         if (rc) {
161                                 printk(KERN_ERR "%s: Error reading xattr "
162                                        "region; rc = [%d]\n", __func__, rc);
163                                 goto out;
164                         }
165                 } else {
166                         /* This is an encrypted data extent */
167                         loff_t lower_offset =
168                                 ((view_extent_num * crypt_stat->extent_size)
169                                  - crypt_stat->metadata_size);
170
171                         rc = ecryptfs_read_lower_page_segment(
172                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
173                                 (lower_offset & ~PAGE_CACHE_MASK),
174                                 crypt_stat->extent_size, page->mapping->host);
175                         if (rc) {
176                                 printk(KERN_ERR "%s: Error attempting to read "
177                                        "extent at offset [%lld] in the lower "
178                                        "file; rc = [%d]\n", __func__,
179                                        lower_offset, rc);
180                                 goto out;
181                         }
182                 }
183                 extent_num_in_page++;
184         }
185 out:
186         return rc;
187 }
188
189 /**
190  * ecryptfs_readpage
191  * @file: An eCryptfs file
192  * @page: Page from eCryptfs inode mapping into which to stick the read data
193  *
194  * Read in a page, decrypting if necessary.
195  *
196  * Returns zero on success; non-zero on error.
197  */
198 static int ecryptfs_readpage(struct file *file, struct page *page)
199 {
200         struct ecryptfs_crypt_stat *crypt_stat =
201                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
202         int rc = 0;
203
204         if (!crypt_stat
205             || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
206             || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
207                 ecryptfs_printk(KERN_DEBUG,
208                                 "Passing through unencrypted page\n");
209                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
210                                                       PAGE_CACHE_SIZE,
211                                                       page->mapping->host);
212         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
213                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
214                         rc = ecryptfs_copy_up_encrypted_with_header(page,
215                                                                     crypt_stat);
216                         if (rc) {
217                                 printk(KERN_ERR "%s: Error attempting to copy "
218                                        "the encrypted content from the lower "
219                                        "file whilst inserting the metadata "
220                                        "from the xattr into the header; rc = "
221                                        "[%d]\n", __func__, rc);
222                                 goto out;
223                         }
224
225                 } else {
226                         rc = ecryptfs_read_lower_page_segment(
227                                 page, page->index, 0, PAGE_CACHE_SIZE,
228                                 page->mapping->host);
229                         if (rc) {
230                                 printk(KERN_ERR "Error reading page; rc = "
231                                        "[%d]\n", rc);
232                                 goto out;
233                         }
234                 }
235         } else {
236                 rc = ecryptfs_decrypt_page(page);
237                 if (rc) {
238                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
239                                         "rc = [%d]\n", rc);
240                         goto out;
241                 }
242         }
243 out:
244         if (rc)
245                 ClearPageUptodate(page);
246         else
247                 SetPageUptodate(page);
248         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
249                         page->index);
250         unlock_page(page);
251         return rc;
252 }
253
254 /**
255  * Called with lower inode mutex held.
256  */
257 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
258 {
259         struct inode *inode = page->mapping->host;
260         int end_byte_in_page;
261
262         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
263                 goto out;
264         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
265         if (to > end_byte_in_page)
266                 end_byte_in_page = to;
267         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
268 out:
269         return 0;
270 }
271
272 /**
273  * ecryptfs_write_begin
274  * @file: The eCryptfs file
275  * @mapping: The eCryptfs object
276  * @pos: The file offset at which to start writing
277  * @len: Length of the write
278  * @flags: Various flags
279  * @pagep: Pointer to return the page
280  * @fsdata: Pointer to return fs data (unused)
281  *
282  * This function must zero any hole we create
283  *
284  * Returns zero on success; non-zero otherwise
285  */
286 static int ecryptfs_write_begin(struct file *file,
287                         struct address_space *mapping,
288                         loff_t pos, unsigned len, unsigned flags,
289                         struct page **pagep, void **fsdata)
290 {
291         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
292         struct page *page;
293         loff_t prev_page_end_size;
294         int rc = 0;
295
296         page = grab_cache_page_write_begin(mapping, index, flags);
297         if (!page)
298                 return -ENOMEM;
299         *pagep = page;
300
301         if (!PageUptodate(page)) {
302                 struct ecryptfs_crypt_stat *crypt_stat =
303                         &ecryptfs_inode_to_private(
304                                 file->f_path.dentry->d_inode)->crypt_stat;
305
306                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
307                     || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
308                         rc = ecryptfs_read_lower_page_segment(
309                                 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
310                         if (rc) {
311                                 printk(KERN_ERR "%s: Error attemping to read "
312                                        "lower page segment; rc = [%d]\n",
313                                        __func__, rc);
314                                 ClearPageUptodate(page);
315                                 goto out;
316                         } else
317                                 SetPageUptodate(page);
318                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
319                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
320                                 rc = ecryptfs_copy_up_encrypted_with_header(
321                                         page, crypt_stat);
322                                 if (rc) {
323                                         printk(KERN_ERR "%s: Error attempting "
324                                                "to copy the encrypted content "
325                                                "from the lower file whilst "
326                                                "inserting the metadata from "
327                                                "the xattr into the header; rc "
328                                                "= [%d]\n", __func__, rc);
329                                         ClearPageUptodate(page);
330                                         goto out;
331                                 }
332                                 SetPageUptodate(page);
333                         } else {
334                                 rc = ecryptfs_read_lower_page_segment(
335                                         page, index, 0, PAGE_CACHE_SIZE,
336                                         mapping->host);
337                                 if (rc) {
338                                         printk(KERN_ERR "%s: Error reading "
339                                                "page; rc = [%d]\n",
340                                                __func__, rc);
341                                         ClearPageUptodate(page);
342                                         goto out;
343                                 }
344                                 SetPageUptodate(page);
345                         }
346                 } else {
347                         rc = ecryptfs_decrypt_page(page);
348                         if (rc) {
349                                 printk(KERN_ERR "%s: Error decrypting page "
350                                        "at index [%ld]; rc = [%d]\n",
351                                        __func__, page->index, rc);
352                                 ClearPageUptodate(page);
353                                 goto out;
354                         }
355                         SetPageUptodate(page);
356                 }
357         }
358         prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
359         /* If creating a page or more of holes, zero them out via truncate.
360          * Note, this will increase i_size. */
361         if (index != 0) {
362                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
363                         rc = ecryptfs_truncate(file->f_path.dentry,
364                                                prev_page_end_size);
365                         if (rc) {
366                                 printk(KERN_ERR "%s: Error on attempt to "
367                                        "truncate to (higher) offset [%lld];"
368                                        " rc = [%d]\n", __func__,
369                                        prev_page_end_size, rc);
370                                 goto out;
371                         }
372                 }
373         }
374         /* Writing to a new page, and creating a small hole from start
375          * of page?  Zero it out. */
376         if ((i_size_read(mapping->host) == prev_page_end_size)
377             && (pos != 0))
378                 zero_user(page, 0, PAGE_CACHE_SIZE);
379 out:
380         return rc;
381 }
382
383 /**
384  * ecryptfs_write_inode_size_to_header
385  *
386  * Writes the lower file size to the first 8 bytes of the header.
387  *
388  * Returns zero on success; non-zero on error.
389  */
390 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
391 {
392         char *file_size_virt;
393         int rc;
394
395         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
396         if (!file_size_virt) {
397                 rc = -ENOMEM;
398                 goto out;
399         }
400         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
401         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
402                                   sizeof(u64));
403         kfree(file_size_virt);
404         if (rc < 0)
405                 printk(KERN_ERR "%s: Error writing file size to header; "
406                        "rc = [%d]\n", __func__, rc);
407         else
408                 rc = 0;
409 out:
410         return rc;
411 }
412
413 struct kmem_cache *ecryptfs_xattr_cache;
414
415 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
416 {
417         ssize_t size;
418         void *xattr_virt;
419         struct dentry *lower_dentry =
420                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
421         struct inode *lower_inode = lower_dentry->d_inode;
422         int rc;
423
424         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
425                 printk(KERN_WARNING
426                        "No support for setting xattr in lower filesystem\n");
427                 rc = -ENOSYS;
428                 goto out;
429         }
430         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
431         if (!xattr_virt) {
432                 printk(KERN_ERR "Out of memory whilst attempting to write "
433                        "inode size to xattr\n");
434                 rc = -ENOMEM;
435                 goto out;
436         }
437         mutex_lock(&lower_inode->i_mutex);
438         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
439                                            xattr_virt, PAGE_CACHE_SIZE);
440         if (size < 0)
441                 size = 8;
442         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
443         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
444                                          xattr_virt, size, 0);
445         mutex_unlock(&lower_inode->i_mutex);
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
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  *
476  * This is where we encrypt the data and pass the encrypted data to
477  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
478  * entire underlying packets.
479  */
480 static int ecryptfs_write_end(struct file *file,
481                         struct address_space *mapping,
482                         loff_t pos, unsigned len, unsigned copied,
483                         struct page *page, void *fsdata)
484 {
485         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
486         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
487         unsigned to = from + copied;
488         struct inode *ecryptfs_inode = mapping->host;
489         struct ecryptfs_crypt_stat *crypt_stat =
490                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
491         int rc;
492
493         if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
494                 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
495                         "crypt_stat at memory location [%p]\n", crypt_stat);
496                 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
497         } else
498                 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
499         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
500                         "(page w/ index = [0x%.16x], to = [%d])\n", index, to);
501         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
502                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
503                                                        to);
504                 if (!rc) {
505                         rc = copied;
506                         fsstack_copy_inode_size(ecryptfs_inode,
507                                 ecryptfs_inode_to_lower(ecryptfs_inode));
508                 }
509                 goto out;
510         }
511         /* Fills in zeros if 'to' goes beyond inode size */
512         rc = fill_zeros_to_end_of_page(page, to);
513         if (rc) {
514                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
515                         "zeros in page with index = [0x%.16x]\n", index);
516                 goto out;
517         }
518         rc = ecryptfs_encrypt_page(page);
519         if (rc) {
520                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
521                                 "index [0x%.16x])\n", index);
522                 goto out;
523         }
524         if (pos + copied > i_size_read(ecryptfs_inode)) {
525                 i_size_write(ecryptfs_inode, pos + copied);
526                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
527                                 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
528         }
529         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
530         if (rc)
531                 printk(KERN_ERR "Error writing inode size to metadata; "
532                        "rc = [%d]\n", rc);
533         else
534                 rc = copied;
535 out:
536         unlock_page(page);
537         page_cache_release(page);
538         return rc;
539 }
540
541 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
542 {
543         int rc = 0;
544         struct inode *inode;
545         struct inode *lower_inode;
546
547         inode = (struct inode *)mapping->host;
548         lower_inode = ecryptfs_inode_to_lower(inode);
549         if (lower_inode->i_mapping->a_ops->bmap)
550                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
551                                                          block);
552         return rc;
553 }
554
555 const struct address_space_operations ecryptfs_aops = {
556         .writepage = ecryptfs_writepage,
557         .readpage = ecryptfs_readpage,
558         .write_begin = ecryptfs_write_begin,
559         .write_end = ecryptfs_write_end,
560         .bmap = ecryptfs_bmap,
561 };