1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * eCryptfs: Linux filesystem encryption layer
4 * This is where eCryptfs coordinates the symmetric encryption and
5 * decryption of the file data as it passes between the lower
6 * encrypted file and the upper decrypted file.
7 *
8 * Copyright (C) 1997-2003 Erez Zadok
9 * Copyright (C) 2001-2003 Stony Brook University
10 * Copyright (C) 2004-2007 International Business Machines Corp.
11 * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
12 */
13
14#include <linux/pagemap.h>
15#include <linux/writeback.h>
16#include <linux/page-flags.h>
17#include <linux/mount.h>
18#include <linux/file.h>
19#include <linux/scatterlist.h>
20#include <linux/slab.h>
21#include <linux/xattr.h>
22#include <linux/unaligned.h>
23#include "ecryptfs_kernel.h"
24
25/*
26 * This is where we encrypt the data and pass the encrypted data to
27 * the lower filesystem. In OpenPGP-compatible mode, we operate on
28 * entire underlying packets.
29 */
30static int ecryptfs_writepages(struct address_space *mapping,
31 struct writeback_control *wbc)
32{
33 struct folio *folio = NULL;
34 int error;
35
36 while ((folio = writeback_iter(mapping, wbc, folio, error: &error))) {
37 error = ecryptfs_encrypt_page(folio);
38 if (error) {
39 ecryptfs_printk(KERN_WARNING,
40 "Error encrypting folio (index [0x%.16lx])\n",
41 folio->index);
42 folio_clear_uptodate(folio);
43 mapping_set_error(mapping, error);
44 }
45 folio_unlock(folio);
46 }
47
48 return error;
49}
50
51static void strip_xattr_flag(char *page_virt,
52 struct ecryptfs_crypt_stat *crypt_stat)
53{
54 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
55 size_t written;
56
57 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
58 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
59 written: &written);
60 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
61 }
62}
63
64/*
65 * Header Extent:
66 * Octets 0-7: Unencrypted file size (big-endian)
67 * Octets 8-15: eCryptfs special marker
68 * Octets 16-19: Flags
69 * Octet 16: File format version number (between 0 and 255)
70 * Octets 17-18: Reserved
71 * Octet 19: Bit 1 (lsb): Reserved
72 * Bit 2: Encrypted?
73 * Bits 3-8: Reserved
74 * Octets 20-23: Header extent size (big-endian)
75 * Octets 24-25: Number of header extents at front of file
76 * (big-endian)
77 * Octet 26: Begin RFC 2440 authentication token packet set
78 */
79
80/**
81 * ecryptfs_copy_up_encrypted_with_header
82 * @folio: Sort of a ``virtual'' representation of the encrypted lower
83 * file. The actual lower file does not have the metadata in
84 * the header. This is locked.
85 * @crypt_stat: The eCryptfs inode's cryptographic context
86 *
87 * The ``view'' is the version of the file that userspace winds up
88 * seeing, with the header information inserted.
89 */
90static int
91ecryptfs_copy_up_encrypted_with_header(struct folio *folio,
92 struct ecryptfs_crypt_stat *crypt_stat)
93{
94 loff_t extent_num_in_page = 0;
95 loff_t num_extents_per_page = (PAGE_SIZE
96 / crypt_stat->extent_size);
97 int rc = 0;
98
99 while (extent_num_in_page < num_extents_per_page) {
100 loff_t view_extent_num = ((loff_t)folio->index
101 * num_extents_per_page)
102 + extent_num_in_page;
103 size_t num_header_extents_at_front =
104 (crypt_stat->metadata_size / crypt_stat->extent_size);
105
106 if (view_extent_num < num_header_extents_at_front) {
107 /* This is a header extent */
108 char *page_virt;
109
110 page_virt = kmap_local_folio(folio, offset: 0);
111 memset(page_virt, 0, PAGE_SIZE);
112 /* TODO: Support more than one header extent */
113 if (view_extent_num == 0) {
114 size_t written;
115
116 rc = ecryptfs_read_xattr_region(
117 page_virt, ecryptfs_inode: folio->mapping->host);
118 strip_xattr_flag(page_virt: page_virt + 16, crypt_stat);
119 ecryptfs_write_header_metadata(virt: page_virt + 20,
120 crypt_stat,
121 written: &written);
122 }
123 kunmap_local(page_virt);
124 flush_dcache_folio(folio);
125 if (rc) {
126 printk(KERN_ERR "%s: Error reading xattr "
127 "region; rc = [%d]\n", __func__, rc);
128 goto out;
129 }
130 } else {
131 /* This is an encrypted data extent */
132 loff_t lower_offset =
133 ((view_extent_num * crypt_stat->extent_size)
134 - crypt_stat->metadata_size);
135
136 rc = ecryptfs_read_lower_page_segment(
137 folio_for_ecryptfs: folio, page_index: (lower_offset >> PAGE_SHIFT),
138 offset_in_page: (lower_offset & ~PAGE_MASK),
139 size: crypt_stat->extent_size, ecryptfs_inode: folio->mapping->host);
140 if (rc) {
141 printk(KERN_ERR "%s: Error attempting to read "
142 "extent at offset [%lld] in the lower "
143 "file; rc = [%d]\n", __func__,
144 lower_offset, rc);
145 goto out;
146 }
147 }
148 extent_num_in_page++;
149 }
150out:
151 return rc;
152}
153
154/**
155 * ecryptfs_read_folio
156 * @file: An eCryptfs file
157 * @folio: Folio from eCryptfs inode mapping into which to stick the read data
158 *
159 * Read in a folio, decrypting if necessary.
160 *
161 * Returns zero on success; non-zero on error.
162 */
163static int ecryptfs_read_folio(struct file *file, struct folio *folio)
164{
165 struct inode *inode = folio->mapping->host;
166 struct ecryptfs_crypt_stat *crypt_stat =
167 &ecryptfs_inode_to_private(inode)->crypt_stat;
168 int err = 0;
169
170 if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
171 err = ecryptfs_read_lower_page_segment(folio_for_ecryptfs: folio, page_index: folio->index, offset_in_page: 0,
172 size: folio_size(folio), ecryptfs_inode: inode);
173 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
174 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
175 err = ecryptfs_copy_up_encrypted_with_header(folio,
176 crypt_stat);
177 if (err) {
178 printk(KERN_ERR "%s: Error attempting to copy "
179 "the encrypted content from the lower "
180 "file whilst inserting the metadata "
181 "from the xattr into the header; err = "
182 "[%d]\n", __func__, err);
183 goto out;
184 }
185
186 } else {
187 err = ecryptfs_read_lower_page_segment(folio_for_ecryptfs: folio,
188 page_index: folio->index, offset_in_page: 0, size: folio_size(folio),
189 ecryptfs_inode: inode);
190 if (err) {
191 printk(KERN_ERR "Error reading page; err = "
192 "[%d]\n", err);
193 goto out;
194 }
195 }
196 } else {
197 err = ecryptfs_decrypt_page(folio);
198 if (err) {
199 ecryptfs_printk(KERN_ERR, "Error decrypting page; "
200 "err = [%d]\n", err);
201 goto out;
202 }
203 }
204out:
205 ecryptfs_printk(KERN_DEBUG, "Unlocking folio with index = [0x%.16lx]\n",
206 folio->index);
207 folio_end_read(folio, success: err == 0);
208 return err;
209}
210
211/*
212 * Called with lower inode mutex held.
213 */
214static int fill_zeros_to_end_of_page(struct folio *folio, unsigned int to)
215{
216 struct inode *inode = folio->mapping->host;
217 int end_byte_in_page;
218
219 if ((i_size_read(inode) / PAGE_SIZE) != folio->index)
220 goto out;
221 end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
222 if (to > end_byte_in_page)
223 end_byte_in_page = to;
224 folio_zero_segment(folio, start: end_byte_in_page, PAGE_SIZE);
225out:
226 return 0;
227}
228
229/**
230 * ecryptfs_write_begin
231 * @iocb: I/O control block for the eCryptfs file
232 * @mapping: The eCryptfs object
233 * @pos: The file offset at which to start writing
234 * @len: Length of the write
235 * @foliop: Pointer to return the folio
236 * @fsdata: Pointer to return fs data (unused)
237 *
238 * This function must zero any hole we create
239 *
240 * Returns zero on success; non-zero otherwise
241 */
242static int ecryptfs_write_begin(const struct kiocb *iocb,
243 struct address_space *mapping,
244 loff_t pos, unsigned len,
245 struct folio **foliop, void **fsdata)
246{
247 pgoff_t index = pos >> PAGE_SHIFT;
248 struct folio *folio;
249 loff_t prev_page_end_size;
250 int rc = 0;
251
252 folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
253 gfp: mapping_gfp_mask(mapping));
254 if (IS_ERR(ptr: folio))
255 return PTR_ERR(ptr: folio);
256 *foliop = folio;
257
258 prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
259 if (!folio_test_uptodate(folio)) {
260 struct ecryptfs_crypt_stat *crypt_stat =
261 &ecryptfs_inode_to_private(inode: mapping->host)->crypt_stat;
262
263 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
264 rc = ecryptfs_read_lower_page_segment(
265 folio_for_ecryptfs: folio, page_index: index, offset_in_page: 0, PAGE_SIZE, ecryptfs_inode: mapping->host);
266 if (rc) {
267 printk(KERN_ERR "%s: Error attempting to read "
268 "lower page segment; rc = [%d]\n",
269 __func__, rc);
270 folio_clear_uptodate(folio);
271 goto out;
272 } else
273 folio_mark_uptodate(folio);
274 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
275 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
276 rc = ecryptfs_copy_up_encrypted_with_header(
277 folio, crypt_stat);
278 if (rc) {
279 printk(KERN_ERR "%s: Error attempting "
280 "to copy the encrypted content "
281 "from the lower file whilst "
282 "inserting the metadata from "
283 "the xattr into the header; rc "
284 "= [%d]\n", __func__, rc);
285 folio_clear_uptodate(folio);
286 goto out;
287 }
288 folio_mark_uptodate(folio);
289 } else {
290 rc = ecryptfs_read_lower_page_segment(
291 folio_for_ecryptfs: folio, page_index: index, offset_in_page: 0, PAGE_SIZE,
292 ecryptfs_inode: mapping->host);
293 if (rc) {
294 printk(KERN_ERR "%s: Error reading "
295 "page; rc = [%d]\n",
296 __func__, rc);
297 folio_clear_uptodate(folio);
298 goto out;
299 }
300 folio_mark_uptodate(folio);
301 }
302 } else {
303 if (prev_page_end_size
304 >= i_size_read(inode: mapping->host)) {
305 folio_zero_range(folio, start: 0, PAGE_SIZE);
306 folio_mark_uptodate(folio);
307 } else if (len < PAGE_SIZE) {
308 rc = ecryptfs_decrypt_page(folio);
309 if (rc) {
310 printk(KERN_ERR "%s: Error decrypting "
311 "page at index [%ld]; "
312 "rc = [%d]\n",
313 __func__, folio->index, rc);
314 folio_clear_uptodate(folio);
315 goto out;
316 }
317 folio_mark_uptodate(folio);
318 }
319 }
320 }
321 /* If creating a page or more of holes, zero them out via truncate.
322 * Note, this will increase i_size. */
323 if (index != 0) {
324 if (prev_page_end_size > i_size_read(inode: mapping->host)) {
325 rc = ecryptfs_truncate(dentry: iocb->ki_filp->f_path.dentry,
326 new_length: prev_page_end_size);
327 if (rc) {
328 printk(KERN_ERR "%s: Error on attempt to "
329 "truncate to (higher) offset [%lld];"
330 " rc = [%d]\n", __func__,
331 prev_page_end_size, rc);
332 goto out;
333 }
334 }
335 }
336 /* Writing to a new page, and creating a small hole from start
337 * of page? Zero it out. */
338 if ((i_size_read(inode: mapping->host) == prev_page_end_size)
339 && (pos != 0))
340 folio_zero_range(folio, start: 0, PAGE_SIZE);
341out:
342 if (unlikely(rc)) {
343 folio_unlock(folio);
344 folio_put(folio);
345 }
346 return rc;
347}
348
349/*
350 * ecryptfs_write_inode_size_to_header
351 *
352 * Writes the lower file size to the first 8 bytes of the header.
353 *
354 * Returns zero on success; non-zero on error.
355 */
356static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
357{
358 char *file_size_virt;
359 int rc;
360
361 file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
362 if (!file_size_virt) {
363 rc = -ENOMEM;
364 goto out;
365 }
366 put_unaligned_be64(val: i_size_read(inode: ecryptfs_inode), p: file_size_virt);
367 rc = ecryptfs_write_lower(ecryptfs_inode, data: file_size_virt, offset: 0,
368 size: sizeof(u64));
369 kfree(objp: file_size_virt);
370 if (rc < 0)
371 printk(KERN_ERR "%s: Error writing file size to header; "
372 "rc = [%d]\n", __func__, rc);
373 else
374 rc = 0;
375out:
376 return rc;
377}
378
379struct kmem_cache *ecryptfs_xattr_cache;
380
381static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
382{
383 ssize_t size;
384 void *xattr_virt;
385 struct dentry *lower_dentry =
386 ecryptfs_inode_to_private(inode: ecryptfs_inode)->lower_file->f_path.dentry;
387 struct inode *lower_inode = d_inode(dentry: lower_dentry);
388 int rc;
389
390 if (!(lower_inode->i_opflags & IOP_XATTR)) {
391 printk(KERN_WARNING
392 "No support for setting xattr in lower filesystem\n");
393 rc = -ENOSYS;
394 goto out;
395 }
396 xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
397 if (!xattr_virt) {
398 rc = -ENOMEM;
399 goto out;
400 }
401 inode_lock(inode: lower_inode);
402 size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
403 xattr_virt, PAGE_SIZE);
404 if (size < 0)
405 size = 8;
406 put_unaligned_be64(val: i_size_read(inode: ecryptfs_inode), p: xattr_virt);
407 rc = __vfs_setxattr(&nop_mnt_idmap, lower_dentry, lower_inode,
408 ECRYPTFS_XATTR_NAME, xattr_virt, size, 0);
409 inode_unlock(inode: lower_inode);
410 if (rc)
411 printk(KERN_ERR "Error whilst attempting to write inode size "
412 "to lower file xattr; rc = [%d]\n", rc);
413 kmem_cache_free(s: ecryptfs_xattr_cache, objp: xattr_virt);
414out:
415 return rc;
416}
417
418int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
419{
420 struct ecryptfs_crypt_stat *crypt_stat;
421
422 crypt_stat = &ecryptfs_inode_to_private(inode: ecryptfs_inode)->crypt_stat;
423 BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
424 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
425 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
426 else
427 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
428}
429
430/**
431 * ecryptfs_write_end
432 * @iocb: I/O control block for the eCryptfs file
433 * @mapping: The eCryptfs object
434 * @pos: The file position
435 * @len: The length of the data (unused)
436 * @copied: The amount of data copied
437 * @folio: The eCryptfs folio
438 * @fsdata: The fsdata (unused)
439 */
440static int ecryptfs_write_end(const struct kiocb *iocb,
441 struct address_space *mapping,
442 loff_t pos, unsigned len, unsigned copied,
443 struct folio *folio, void *fsdata)
444{
445 pgoff_t index = pos >> PAGE_SHIFT;
446 unsigned from = pos & (PAGE_SIZE - 1);
447 unsigned to = from + copied;
448 struct inode *ecryptfs_inode = mapping->host;
449 struct ecryptfs_crypt_stat *crypt_stat =
450 &ecryptfs_inode_to_private(inode: ecryptfs_inode)->crypt_stat;
451 int rc;
452
453 ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
454 "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
455 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
456 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
457 folio_for_lower: folio, offset_in_page: 0, size: to);
458 if (!rc) {
459 rc = copied;
460 fsstack_copy_inode_size(dst: ecryptfs_inode,
461 src: ecryptfs_inode_to_lower(inode: ecryptfs_inode));
462 }
463 goto out;
464 }
465 if (!folio_test_uptodate(folio)) {
466 if (copied < PAGE_SIZE) {
467 rc = 0;
468 goto out;
469 }
470 folio_mark_uptodate(folio);
471 }
472 /* Fills in zeros if 'to' goes beyond inode size */
473 rc = fill_zeros_to_end_of_page(folio, to);
474 if (rc) {
475 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
476 "zeros in page with index = [0x%.16lx]\n", index);
477 goto out;
478 }
479 rc = ecryptfs_encrypt_page(folio);
480 if (rc) {
481 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
482 "index [0x%.16lx])\n", index);
483 goto out;
484 }
485 if (pos + copied > i_size_read(inode: ecryptfs_inode)) {
486 i_size_write(inode: ecryptfs_inode, i_size: pos + copied);
487 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
488 "[0x%.16llx]\n",
489 (unsigned long long)i_size_read(ecryptfs_inode));
490 }
491 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
492 if (rc)
493 printk(KERN_ERR "Error writing inode size to metadata; "
494 "rc = [%d]\n", rc);
495 else
496 rc = copied;
497out:
498 folio_unlock(folio);
499 folio_put(folio);
500 return rc;
501}
502
503static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
504{
505 struct inode *lower_inode = ecryptfs_inode_to_lower(inode: mapping->host);
506 int ret = bmap(inode: lower_inode, block: &block);
507
508 if (ret)
509 return 0;
510 return block;
511}
512
513#include <linux/buffer_head.h>
514
515const struct address_space_operations ecryptfs_aops = {
516 /*
517 * XXX: This is pretty broken for multiple reasons: ecryptfs does not
518 * actually use buffer_heads, and ecryptfs will crash without
519 * CONFIG_BLOCK. But it matches the behavior before the default for
520 * address_space_operations without the ->dirty_folio method was
521 * cleaned up, so this is the best we can do without maintainer
522 * feedback.
523 */
524#ifdef CONFIG_BLOCK
525 .dirty_folio = block_dirty_folio,
526 .invalidate_folio = block_invalidate_folio,
527#endif
528 .writepages = ecryptfs_writepages,
529 .read_folio = ecryptfs_read_folio,
530 .write_begin = ecryptfs_write_begin,
531 .write_end = ecryptfs_write_end,
532 .migrate_folio = filemap_migrate_folio,
533 .bmap = ecryptfs_bmap,
534};
535

source code of linux/fs/ecryptfs/mmap.c