2 * This contains encryption functions for per-file encryption.
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility
7 * Written by Michael Halcrow, 2014.
9 * Filename encryption additions
10 * Uday Savagaonkar, 2014
11 * Encryption policy handling additions
12 * Ildar Muslukhov, 2014
13 * Add fscrypt_pullback_bio_page()
16 * This has not yet undergone a rigorous security audit.
18 * The usage of AES-XTS should conform to recommendations in NIST
19 * Special Publication 800-38E and IEEE P1619/D16.
22 #include <linux/pagemap.h>
23 #include <linux/mempool.h>
24 #include <linux/module.h>
25 #include <linux/scatterlist.h>
26 #include <linux/ratelimit.h>
27 #include <linux/bio.h>
28 #include <linux/dcache.h>
29 #include <linux/fscrypto.h>
30 #include <linux/ecryptfs.h>
32 static unsigned int num_prealloc_crypto_pages
= 32;
33 static unsigned int num_prealloc_crypto_ctxs
= 128;
35 module_param(num_prealloc_crypto_pages
, uint
, 0444);
36 MODULE_PARM_DESC(num_prealloc_crypto_pages
,
37 "Number of crypto pages to preallocate");
38 module_param(num_prealloc_crypto_ctxs
, uint
, 0444);
39 MODULE_PARM_DESC(num_prealloc_crypto_ctxs
,
40 "Number of crypto contexts to preallocate");
42 static mempool_t
*fscrypt_bounce_page_pool
= NULL
;
44 static LIST_HEAD(fscrypt_free_ctxs
);
45 static DEFINE_SPINLOCK(fscrypt_ctx_lock
);
47 static struct workqueue_struct
*fscrypt_read_workqueue
;
48 static DEFINE_MUTEX(fscrypt_init_mutex
);
50 static struct kmem_cache
*fscrypt_ctx_cachep
;
51 struct kmem_cache
*fscrypt_info_cachep
;
54 * fscrypt_release_ctx() - Releases an encryption context
55 * @ctx: The encryption context to release.
57 * If the encryption context was allocated from the pre-allocated pool, returns
58 * it to that pool. Else, frees it.
60 * If there's a bounce page in the context, this frees that.
62 void fscrypt_release_ctx(struct fscrypt_ctx
*ctx
)
66 if (ctx
->flags
& FS_WRITE_PATH_FL
&& ctx
->w
.bounce_page
) {
67 mempool_free(ctx
->w
.bounce_page
, fscrypt_bounce_page_pool
);
68 ctx
->w
.bounce_page
= NULL
;
70 ctx
->w
.control_page
= NULL
;
71 if (ctx
->flags
& FS_CTX_REQUIRES_FREE_ENCRYPT_FL
) {
72 kmem_cache_free(fscrypt_ctx_cachep
, ctx
);
74 spin_lock_irqsave(&fscrypt_ctx_lock
, flags
);
75 list_add(&ctx
->free_list
, &fscrypt_free_ctxs
);
76 spin_unlock_irqrestore(&fscrypt_ctx_lock
, flags
);
79 EXPORT_SYMBOL(fscrypt_release_ctx
);
82 * fscrypt_get_ctx() - Gets an encryption context
83 * @inode: The inode for which we are doing the crypto
85 * Allocates and initializes an encryption context.
87 * Return: An allocated and initialized encryption context on success; error
88 * value or NULL otherwise.
90 struct fscrypt_ctx
*fscrypt_get_ctx(struct inode
*inode
)
92 struct fscrypt_ctx
*ctx
= NULL
;
93 struct fscrypt_info
*ci
= inode
->i_crypt_info
;
97 return ERR_PTR(-ENOKEY
);
100 * We first try getting the ctx from a free list because in
101 * the common case the ctx will have an allocated and
102 * initialized crypto tfm, so it's probably a worthwhile
103 * optimization. For the bounce page, we first try getting it
104 * from the kernel allocator because that's just about as fast
105 * as getting it from a list and because a cache of free pages
106 * should generally be a "last resort" option for a filesystem
107 * to be able to do its job.
109 spin_lock_irqsave(&fscrypt_ctx_lock
, flags
);
110 ctx
= list_first_entry_or_null(&fscrypt_free_ctxs
,
111 struct fscrypt_ctx
, free_list
);
113 list_del(&ctx
->free_list
);
114 spin_unlock_irqrestore(&fscrypt_ctx_lock
, flags
);
116 ctx
= kmem_cache_zalloc(fscrypt_ctx_cachep
, GFP_NOFS
);
118 return ERR_PTR(-ENOMEM
);
119 ctx
->flags
|= FS_CTX_REQUIRES_FREE_ENCRYPT_FL
;
121 ctx
->flags
&= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL
;
123 ctx
->flags
&= ~FS_WRITE_PATH_FL
;
126 EXPORT_SYMBOL(fscrypt_get_ctx
);
129 * fscrypt_complete() - The completion callback for page encryption
130 * @req: The asynchronous encryption request context
131 * @res: The result of the encryption operation
133 static void fscrypt_complete(struct crypto_async_request
*req
, int res
)
135 struct fscrypt_completion_result
*ecr
= req
->data
;
137 if (res
== -EINPROGRESS
)
140 complete(&ecr
->completion
);
146 } fscrypt_direction_t
;
148 static int do_page_crypto(struct inode
*inode
,
149 fscrypt_direction_t rw
, pgoff_t index
,
150 struct page
*src_page
, struct page
*dest_page
)
152 u8 xts_tweak
[FS_XTS_TWEAK_SIZE
];
153 struct skcipher_request
*req
= NULL
;
154 DECLARE_FS_COMPLETION_RESULT(ecr
);
155 struct scatterlist dst
, src
;
156 struct fscrypt_info
*ci
= inode
->i_crypt_info
;
157 struct crypto_skcipher
*tfm
= ci
->ci_ctfm
;
160 req
= skcipher_request_alloc(tfm
, GFP_NOFS
);
162 printk_ratelimited(KERN_ERR
163 "%s: crypto_request_alloc() failed\n",
168 skcipher_request_set_callback(
169 req
, CRYPTO_TFM_REQ_MAY_BACKLOG
| CRYPTO_TFM_REQ_MAY_SLEEP
,
170 fscrypt_complete
, &ecr
);
172 BUILD_BUG_ON(FS_XTS_TWEAK_SIZE
< sizeof(index
));
173 memcpy(xts_tweak
, &index
, sizeof(index
));
174 memset(&xts_tweak
[sizeof(index
)], 0,
175 FS_XTS_TWEAK_SIZE
- sizeof(index
));
177 sg_init_table(&dst
, 1);
178 sg_set_page(&dst
, dest_page
, PAGE_SIZE
, 0);
179 sg_init_table(&src
, 1);
180 sg_set_page(&src
, src_page
, PAGE_SIZE
, 0);
181 skcipher_request_set_crypt(req
, &src
, &dst
, PAGE_SIZE
,
183 if (rw
== FS_DECRYPT
)
184 res
= crypto_skcipher_decrypt(req
);
186 res
= crypto_skcipher_encrypt(req
);
187 if (res
== -EINPROGRESS
|| res
== -EBUSY
) {
188 BUG_ON(req
->base
.data
!= &ecr
);
189 wait_for_completion(&ecr
.completion
);
192 skcipher_request_free(req
);
194 printk_ratelimited(KERN_ERR
195 "%s: crypto_skcipher_encrypt() returned %d\n",
202 static struct page
*alloc_bounce_page(struct fscrypt_ctx
*ctx
)
204 ctx
->w
.bounce_page
= mempool_alloc(fscrypt_bounce_page_pool
,
206 if (ctx
->w
.bounce_page
== NULL
)
207 return ERR_PTR(-ENOMEM
);
208 ctx
->flags
|= FS_WRITE_PATH_FL
;
209 return ctx
->w
.bounce_page
;
213 * fscypt_encrypt_page() - Encrypts a page
214 * @inode: The inode for which the encryption should take place
215 * @plaintext_page: The page to encrypt. Must be locked.
217 * Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
218 * encryption context.
220 * Called on the page write path. The caller must call
221 * fscrypt_restore_control_page() on the returned ciphertext page to
222 * release the bounce buffer and the encryption context.
224 * Return: An allocated page with the encrypted content on success. Else, an
225 * error value or NULL.
227 struct page
*fscrypt_encrypt_page(struct inode
*inode
,
228 struct page
*plaintext_page
)
230 struct fscrypt_ctx
*ctx
;
231 struct page
*ciphertext_page
= NULL
;
234 BUG_ON(!PageLocked(plaintext_page
));
236 ctx
= fscrypt_get_ctx(inode
);
238 return (struct page
*)ctx
;
240 /* The encryption operation will require a bounce page. */
241 ciphertext_page
= alloc_bounce_page(ctx
);
242 if (IS_ERR(ciphertext_page
))
245 ctx
->w
.control_page
= plaintext_page
;
246 err
= do_page_crypto(inode
, FS_ENCRYPT
, plaintext_page
->index
,
247 plaintext_page
, ciphertext_page
);
249 ciphertext_page
= ERR_PTR(err
);
252 SetPagePrivate(ciphertext_page
);
253 set_page_private(ciphertext_page
, (unsigned long)ctx
);
254 lock_page(ciphertext_page
);
255 return ciphertext_page
;
258 fscrypt_release_ctx(ctx
);
259 return ciphertext_page
;
261 EXPORT_SYMBOL(fscrypt_encrypt_page
);
264 * f2crypt_decrypt_page() - Decrypts a page in-place
265 * @page: The page to decrypt. Must be locked.
267 * Decrypts page in-place using the ctx encryption context.
269 * Called from the read completion callback.
271 * Return: Zero on success, non-zero otherwise.
273 int fscrypt_decrypt_page(struct page
*page
)
275 BUG_ON(!PageLocked(page
));
277 return do_page_crypto(page
->mapping
->host
,
278 FS_DECRYPT
, page
->index
, page
, page
);
280 EXPORT_SYMBOL(fscrypt_decrypt_page
);
282 int fscrypt_zeroout_range(struct inode
*inode
, pgoff_t lblk
,
283 sector_t pblk
, unsigned int len
)
285 struct fscrypt_ctx
*ctx
;
286 struct page
*ciphertext_page
= NULL
;
290 BUG_ON(inode
->i_sb
->s_blocksize
!= PAGE_SIZE
);
292 ctx
= fscrypt_get_ctx(inode
);
296 ciphertext_page
= alloc_bounce_page(ctx
);
297 if (IS_ERR(ciphertext_page
)) {
298 err
= PTR_ERR(ciphertext_page
);
303 err
= do_page_crypto(inode
, FS_ENCRYPT
, lblk
,
304 ZERO_PAGE(0), ciphertext_page
);
308 bio
= bio_alloc(GFP_KERNEL
, 1);
313 bio
->bi_bdev
= inode
->i_sb
->s_bdev
;
314 bio
->bi_iter
.bi_sector
=
315 pblk
<< (inode
->i_sb
->s_blocksize_bits
- 9);
316 ret
= bio_add_page(bio
, ciphertext_page
,
317 inode
->i_sb
->s_blocksize
, 0);
318 if (ret
!= inode
->i_sb
->s_blocksize
) {
319 /* should never happen! */
325 err
= submit_bio_wait(WRITE
, bio
);
326 if ((err
== 0) && bio
->bi_error
)
336 fscrypt_release_ctx(ctx
);
339 EXPORT_SYMBOL(fscrypt_zeroout_range
);
342 * Validate dentries for encrypted directories to make sure we aren't
343 * potentially caching stale data after a key has been added or
346 static int fscrypt_d_revalidate(struct dentry
*dentry
, unsigned int flags
)
348 struct inode
*dir
= d_inode(dentry
->d_parent
);
349 struct fscrypt_info
*ci
= dir
->i_crypt_info
;
350 int dir_has_key
, cached_with_key
;
352 if (!dir
->i_sb
->s_cop
->is_encrypted(dir
))
355 if (ci
&& ci
->ci_keyring_key
&&
356 (ci
->ci_keyring_key
->flags
& ((1 << KEY_FLAG_INVALIDATED
) |
357 (1 << KEY_FLAG_REVOKED
) |
358 (1 << KEY_FLAG_DEAD
))))
361 /* this should eventually be an flag in d_flags */
362 spin_lock(&dentry
->d_lock
);
363 cached_with_key
= dentry
->d_flags
& DCACHE_ENCRYPTED_WITH_KEY
;
364 spin_unlock(&dentry
->d_lock
);
365 dir_has_key
= (ci
!= NULL
);
368 * If the dentry was cached without the key, and it is a
369 * negative dentry, it might be a valid name. We can't check
370 * if the key has since been made available due to locking
371 * reasons, so we fail the validation so ext4_lookup() can do
374 * We also fail the validation if the dentry was created with
375 * the key present, but we no longer have the key, or vice versa.
377 if ((!cached_with_key
&& d_is_negative(dentry
)) ||
378 (!cached_with_key
&& dir_has_key
) ||
379 (cached_with_key
&& !dir_has_key
))
384 const struct dentry_operations fscrypt_d_ops
= {
385 .d_revalidate
= fscrypt_d_revalidate
,
387 EXPORT_SYMBOL(fscrypt_d_ops
);
390 * Call fscrypt_decrypt_page on every single page, reusing the encryption
393 static void completion_pages(struct work_struct
*work
)
395 struct fscrypt_ctx
*ctx
=
396 container_of(work
, struct fscrypt_ctx
, r
.work
);
397 struct bio
*bio
= ctx
->r
.bio
;
401 bio_for_each_segment_all(bv
, bio
, i
) {
402 struct page
*page
= bv
->bv_page
;
403 int ret
= fscrypt_decrypt_page(page
);
409 SetPageUptodate(page
);
413 fscrypt_release_ctx(ctx
);
417 void fscrypt_decrypt_bio_pages(struct fscrypt_ctx
*ctx
, struct bio
*bio
)
419 INIT_WORK(&ctx
->r
.work
, completion_pages
);
421 queue_work(fscrypt_read_workqueue
, &ctx
->r
.work
);
423 EXPORT_SYMBOL(fscrypt_decrypt_bio_pages
);
425 void fscrypt_pullback_bio_page(struct page
**page
, bool restore
)
427 struct fscrypt_ctx
*ctx
;
428 struct page
*bounce_page
;
430 /* The bounce data pages are unmapped. */
431 if ((*page
)->mapping
)
434 /* The bounce data page is unmapped. */
436 ctx
= (struct fscrypt_ctx
*)page_private(bounce_page
);
438 /* restore control page */
439 *page
= ctx
->w
.control_page
;
442 fscrypt_restore_control_page(bounce_page
);
444 EXPORT_SYMBOL(fscrypt_pullback_bio_page
);
446 void fscrypt_restore_control_page(struct page
*page
)
448 struct fscrypt_ctx
*ctx
;
450 ctx
= (struct fscrypt_ctx
*)page_private(page
);
451 set_page_private(page
, (unsigned long)NULL
);
452 ClearPagePrivate(page
);
454 fscrypt_release_ctx(ctx
);
456 EXPORT_SYMBOL(fscrypt_restore_control_page
);
458 static void fscrypt_destroy(void)
460 struct fscrypt_ctx
*pos
, *n
;
462 list_for_each_entry_safe(pos
, n
, &fscrypt_free_ctxs
, free_list
)
463 kmem_cache_free(fscrypt_ctx_cachep
, pos
);
464 INIT_LIST_HEAD(&fscrypt_free_ctxs
);
465 mempool_destroy(fscrypt_bounce_page_pool
);
466 fscrypt_bounce_page_pool
= NULL
;
470 * fscrypt_initialize() - allocate major buffers for fs encryption.
472 * We only call this when we start accessing encrypted files, since it
473 * results in memory getting allocated that wouldn't otherwise be used.
475 * Return: Zero on success, non-zero otherwise.
477 int fscrypt_initialize(void)
479 int i
, res
= -ENOMEM
;
481 if (fscrypt_bounce_page_pool
)
484 mutex_lock(&fscrypt_init_mutex
);
485 if (fscrypt_bounce_page_pool
)
486 goto already_initialized
;
488 for (i
= 0; i
< num_prealloc_crypto_ctxs
; i
++) {
489 struct fscrypt_ctx
*ctx
;
491 ctx
= kmem_cache_zalloc(fscrypt_ctx_cachep
, GFP_NOFS
);
494 list_add(&ctx
->free_list
, &fscrypt_free_ctxs
);
497 fscrypt_bounce_page_pool
=
498 mempool_create_page_pool(num_prealloc_crypto_pages
, 0);
499 if (!fscrypt_bounce_page_pool
)
503 mutex_unlock(&fscrypt_init_mutex
);
507 mutex_unlock(&fscrypt_init_mutex
);
510 EXPORT_SYMBOL(fscrypt_initialize
);
513 * fscrypt_init() - Set up for fs encryption.
515 static int __init
fscrypt_init(void)
517 fscrypt_read_workqueue
= alloc_workqueue("fscrypt_read_queue",
519 if (!fscrypt_read_workqueue
)
522 fscrypt_ctx_cachep
= KMEM_CACHE(fscrypt_ctx
, SLAB_RECLAIM_ACCOUNT
);
523 if (!fscrypt_ctx_cachep
)
524 goto fail_free_queue
;
526 fscrypt_info_cachep
= KMEM_CACHE(fscrypt_info
, SLAB_RECLAIM_ACCOUNT
);
527 if (!fscrypt_info_cachep
)
533 kmem_cache_destroy(fscrypt_ctx_cachep
);
535 destroy_workqueue(fscrypt_read_workqueue
);
539 module_init(fscrypt_init
)
542 * fscrypt_exit() - Shutdown the fs encryption system
544 static void __exit
fscrypt_exit(void)
548 if (fscrypt_read_workqueue
)
549 destroy_workqueue(fscrypt_read_workqueue
);
550 kmem_cache_destroy(fscrypt_ctx_cachep
);
551 kmem_cache_destroy(fscrypt_info_cachep
);
553 module_exit(fscrypt_exit
);
555 MODULE_LICENSE("GPL");