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/crypto.h>
23 #include <linux/ecryptfs.h>
24 #include <linux/pagemap.h>
25 #include <linux/mempool.h>
26 #include <linux/module.h>
27 #include <linux/scatterlist.h>
28 #include <linux/ratelimit.h>
29 #include <linux/bio.h>
30 #include <linux/dcache.h>
31 #include <linux/fscrypto.h>
33 static unsigned int num_prealloc_crypto_pages = 32;
34 static unsigned int num_prealloc_crypto_ctxs = 128;
36 module_param(num_prealloc_crypto_pages, uint, 0444);
37 MODULE_PARM_DESC(num_prealloc_crypto_pages,
38 "Number of crypto pages to preallocate");
39 module_param(num_prealloc_crypto_ctxs, uint, 0444);
40 MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
41 "Number of crypto contexts to preallocate");
43 static mempool_t *fscrypt_bounce_page_pool = NULL;
45 static LIST_HEAD(fscrypt_free_ctxs);
46 static DEFINE_SPINLOCK(fscrypt_ctx_lock);
48 static struct workqueue_struct *fscrypt_read_workqueue;
49 static DEFINE_MUTEX(fscrypt_init_mutex);
51 static struct kmem_cache *fscrypt_ctx_cachep;
52 struct kmem_cache *fscrypt_info_cachep;
55 * fscrypt_release_ctx() - Releases an encryption context
56 * @ctx: The encryption context to release.
58 * If the encryption context was allocated from the pre-allocated pool, returns
59 * it to that pool. Else, frees it.
61 * If there's a bounce page in the context, this frees that.
63 void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
67 if (ctx->flags & FS_WRITE_PATH_FL && ctx->w.bounce_page) {
68 mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
69 ctx->w.bounce_page = NULL;
71 ctx->w.control_page = NULL;
72 if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
73 kmem_cache_free(fscrypt_ctx_cachep, ctx);
75 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
76 list_add(&ctx->free_list, &fscrypt_free_ctxs);
77 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
80 EXPORT_SYMBOL(fscrypt_release_ctx);
83 * fscrypt_get_ctx() - Gets an encryption context
84 * @inode: The inode for which we are doing the crypto
86 * Allocates and initializes an encryption context.
88 * Return: An allocated and initialized encryption context on success; error
89 * value or NULL otherwise.
91 struct fscrypt_ctx *fscrypt_get_ctx(struct inode *inode)
93 struct fscrypt_ctx *ctx = NULL;
94 struct fscrypt_info *ci = inode->i_crypt_info;
98 return ERR_PTR(-ENOKEY);
101 * We first try getting the ctx from a free list because in
102 * the common case the ctx will have an allocated and
103 * initialized crypto tfm, so it's probably a worthwhile
104 * optimization. For the bounce page, we first try getting it
105 * from the kernel allocator because that's just about as fast
106 * as getting it from a list and because a cache of free pages
107 * should generally be a "last resort" option for a filesystem
108 * to be able to do its job.
110 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
111 ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
112 struct fscrypt_ctx, free_list);
114 list_del(&ctx->free_list);
115 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
117 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
119 return ERR_PTR(-ENOMEM);
120 ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
122 ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
124 ctx->flags &= ~FS_WRITE_PATH_FL;
127 EXPORT_SYMBOL(fscrypt_get_ctx);
130 * fscrypt_complete() - The completion callback for page encryption
131 * @req: The asynchronous encryption request context
132 * @res: The result of the encryption operation
134 static void fscrypt_complete(struct crypto_async_request *req, int res)
136 struct fscrypt_completion_result *ecr = req->data;
138 if (res == -EINPROGRESS)
141 complete(&ecr->completion);
147 } fscrypt_direction_t;
149 static int do_page_crypto(struct inode *inode,
150 fscrypt_direction_t rw, pgoff_t index,
151 struct page *src_page, struct page *dest_page)
153 u8 xts_tweak[FS_XTS_TWEAK_SIZE];
154 struct ablkcipher_request *req = NULL;
155 DECLARE_FS_COMPLETION_RESULT(ecr);
156 struct scatterlist dst, src;
157 struct fscrypt_info *ci = inode->i_crypt_info;
158 struct crypto_ablkcipher *tfm = ci->ci_ctfm;
161 req = ablkcipher_request_alloc(tfm, GFP_NOFS);
163 printk_ratelimited(KERN_ERR
164 "%s: crypto_request_alloc() failed\n",
169 ablkcipher_request_set_callback(
170 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
171 fscrypt_complete, &ecr);
173 BUILD_BUG_ON(FS_XTS_TWEAK_SIZE < sizeof(index));
174 memcpy(xts_tweak, &inode->i_ino, sizeof(index));
175 memset(&xts_tweak[sizeof(index)], 0,
176 FS_XTS_TWEAK_SIZE - sizeof(index));
178 sg_init_table(&dst, 1);
179 sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0);
180 sg_init_table(&src, 1);
181 sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0);
182 ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
184 if (rw == FS_DECRYPT)
185 res = crypto_ablkcipher_decrypt(req);
187 res = crypto_ablkcipher_encrypt(req);
188 if (res == -EINPROGRESS || res == -EBUSY) {
189 BUG_ON(req->base.data != &ecr);
190 wait_for_completion(&ecr.completion);
193 ablkcipher_request_free(req);
195 printk_ratelimited(KERN_ERR
196 "%s: crypto_ablkcipher_encrypt() returned %d\n",
203 static struct page *alloc_bounce_page(struct fscrypt_ctx *ctx)
205 ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool,
207 if (ctx->w.bounce_page == NULL)
208 return ERR_PTR(-ENOMEM);
209 ctx->flags |= FS_WRITE_PATH_FL;
210 return ctx->w.bounce_page;
214 * fscypt_encrypt_page() - Encrypts a page
215 * @inode: The inode for which the encryption should take place
216 * @plaintext_page: The page to encrypt. Must be locked.
218 * Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
219 * encryption context.
221 * Called on the page write path. The caller must call
222 * fscrypt_restore_control_page() on the returned ciphertext page to
223 * release the bounce buffer and the encryption context.
225 * Return: An allocated page with the encrypted content on success. Else, an
226 * error value or NULL.
228 struct page *fscrypt_encrypt_page(struct inode *inode,
229 struct page *plaintext_page)
231 struct fscrypt_ctx *ctx;
232 struct page *ciphertext_page = NULL;
235 BUG_ON(!PageLocked(plaintext_page));
237 ctx = fscrypt_get_ctx(inode);
239 return (struct page *)ctx;
241 /* The encryption operation will require a bounce page. */
242 ciphertext_page = alloc_bounce_page(ctx);
243 if (IS_ERR(ciphertext_page))
246 ctx->w.control_page = plaintext_page;
247 err = do_page_crypto(inode, FS_ENCRYPT, plaintext_page->index,
248 plaintext_page, ciphertext_page);
250 ciphertext_page = ERR_PTR(err);
253 SetPagePrivate(ciphertext_page);
254 set_page_private(ciphertext_page, (unsigned long)ctx);
255 lock_page(ciphertext_page);
256 return ciphertext_page;
259 fscrypt_release_ctx(ctx);
260 return ciphertext_page;
262 EXPORT_SYMBOL(fscrypt_encrypt_page);
265 * f2crypt_decrypt_page() - Decrypts a page in-place
266 * @page: The page to decrypt. Must be locked.
268 * Decrypts page in-place using the ctx encryption context.
270 * Called from the read completion callback.
272 * Return: Zero on success, non-zero otherwise.
274 int fscrypt_decrypt_page(struct page *page)
276 BUG_ON(!PageLocked(page));
278 return do_page_crypto(page->mapping->host,
279 FS_DECRYPT, page->index, page, page);
281 EXPORT_SYMBOL(fscrypt_decrypt_page);
283 int fscrypt_zeroout_range(struct inode *inode, pgoff_t lblk,
284 sector_t pblk, unsigned int len)
286 struct fscrypt_ctx *ctx;
287 struct page *ciphertext_page = NULL;
291 BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE);
293 ctx = fscrypt_get_ctx(inode);
297 ciphertext_page = alloc_bounce_page(ctx);
298 if (IS_ERR(ciphertext_page)) {
299 err = PTR_ERR(ciphertext_page);
304 err = do_page_crypto(inode, FS_ENCRYPT, lblk,
305 ZERO_PAGE(0), ciphertext_page);
309 bio = bio_alloc(GFP_KERNEL, 1);
314 bio->bi_bdev = inode->i_sb->s_bdev;
315 bio->bi_iter.bi_sector =
316 pblk << (inode->i_sb->s_blocksize_bits - 9);
317 ret = bio_add_page(bio, ciphertext_page,
318 inode->i_sb->s_blocksize, 0);
319 if (ret != inode->i_sb->s_blocksize) {
320 /* should never happen! */
326 err = submit_bio_wait(WRITE, bio);
327 if ((err == 0) && bio->bi_error)
337 fscrypt_release_ctx(ctx);
340 EXPORT_SYMBOL(fscrypt_zeroout_range);
343 * Validate dentries for encrypted directories to make sure we aren't
344 * potentially caching stale data after a key has been added or
347 static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
349 struct inode *dir = d_inode(dentry->d_parent);
350 struct fscrypt_info *ci = dir->i_crypt_info;
351 int dir_has_key, cached_with_key;
353 if (!dir->i_sb->s_cop->is_encrypted(dir))
356 if (ci && ci->ci_keyring_key &&
357 (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
358 (1 << KEY_FLAG_REVOKED) |
359 (1 << KEY_FLAG_DEAD))))
362 /* this should eventually be an flag in d_flags */
363 spin_lock(&dentry->d_lock);
364 cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
365 spin_unlock(&dentry->d_lock);
366 dir_has_key = (ci != NULL);
369 * If the dentry was cached without the key, and it is a
370 * negative dentry, it might be a valid name. We can't check
371 * if the key has since been made available due to locking
372 * reasons, so we fail the validation so ext4_lookup() can do
375 * We also fail the validation if the dentry was created with
376 * the key present, but we no longer have the key, or vice versa.
378 if ((!cached_with_key && d_is_negative(dentry)) ||
379 (!cached_with_key && dir_has_key) ||
380 (cached_with_key && !dir_has_key))
385 const struct dentry_operations fscrypt_d_ops = {
386 .d_revalidate = fscrypt_d_revalidate,
388 EXPORT_SYMBOL(fscrypt_d_ops);
391 * Call fscrypt_decrypt_page on every single page, reusing the encryption
394 static void completion_pages(struct work_struct *work)
396 struct fscrypt_ctx *ctx =
397 container_of(work, struct fscrypt_ctx, r.work);
398 struct bio *bio = ctx->r.bio;
402 bio_for_each_segment_all(bv, bio, i) {
403 struct page *page = bv->bv_page;
404 int ret = fscrypt_decrypt_page(page);
410 SetPageUptodate(page);
414 fscrypt_release_ctx(ctx);
418 void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *ctx, struct bio *bio)
420 INIT_WORK(&ctx->r.work, completion_pages);
422 queue_work(fscrypt_read_workqueue, &ctx->r.work);
424 EXPORT_SYMBOL(fscrypt_decrypt_bio_pages);
426 void fscrypt_pullback_bio_page(struct page **page, bool restore)
428 struct fscrypt_ctx *ctx;
429 struct page *bounce_page;
431 /* The bounce data pages are unmapped. */
432 if ((*page)->mapping)
435 /* The bounce data page is unmapped. */
437 ctx = (struct fscrypt_ctx *)page_private(bounce_page);
439 /* restore control page */
440 *page = ctx->w.control_page;
443 fscrypt_restore_control_page(bounce_page);
445 EXPORT_SYMBOL(fscrypt_pullback_bio_page);
447 void fscrypt_restore_control_page(struct page *page)
449 struct fscrypt_ctx *ctx;
451 ctx = (struct fscrypt_ctx *)page_private(page);
452 set_page_private(page, (unsigned long)NULL);
453 ClearPagePrivate(page);
455 fscrypt_release_ctx(ctx);
457 EXPORT_SYMBOL(fscrypt_restore_control_page);
459 static void fscrypt_destroy(void)
461 struct fscrypt_ctx *pos, *n;
463 list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
464 kmem_cache_free(fscrypt_ctx_cachep, pos);
465 INIT_LIST_HEAD(&fscrypt_free_ctxs);
466 mempool_destroy(fscrypt_bounce_page_pool);
467 fscrypt_bounce_page_pool = NULL;
471 * fscrypt_initialize() - allocate major buffers for fs encryption.
473 * We only call this when we start accessing encrypted files, since it
474 * results in memory getting allocated that wouldn't otherwise be used.
476 * Return: Zero on success, non-zero otherwise.
478 int fscrypt_initialize(void)
480 int i, res = -ENOMEM;
482 if (fscrypt_bounce_page_pool)
485 mutex_lock(&fscrypt_init_mutex);
486 if (fscrypt_bounce_page_pool)
487 goto already_initialized;
489 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
490 struct fscrypt_ctx *ctx;
492 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
495 list_add(&ctx->free_list, &fscrypt_free_ctxs);
498 fscrypt_bounce_page_pool =
499 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
500 if (!fscrypt_bounce_page_pool)
504 mutex_unlock(&fscrypt_init_mutex);
508 mutex_unlock(&fscrypt_init_mutex);
511 EXPORT_SYMBOL(fscrypt_initialize);
514 * fscrypt_init() - Set up for fs encryption.
516 static int __init fscrypt_init(void)
518 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
520 if (!fscrypt_read_workqueue)
523 fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
524 if (!fscrypt_ctx_cachep)
525 goto fail_free_queue;
527 fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
528 if (!fscrypt_info_cachep)
534 kmem_cache_destroy(fscrypt_ctx_cachep);
536 destroy_workqueue(fscrypt_read_workqueue);
540 module_init(fscrypt_init)
543 * fscrypt_exit() - Shutdown the fs encryption system
545 static void __exit fscrypt_exit(void)
549 if (fscrypt_read_workqueue)
550 destroy_workqueue(fscrypt_read_workqueue);
551 kmem_cache_destroy(fscrypt_ctx_cachep);
552 kmem_cache_destroy(fscrypt_info_cachep);
554 module_exit(fscrypt_exit);
556 MODULE_LICENSE("GPL");