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)
349 struct fscrypt_info *ci;
350 int dir_has_key, cached_with_key;
352 dir = dget_parent(dentry);
353 if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
358 ci = d_inode(dir)->i_crypt_info;
359 if (ci && ci->ci_keyring_key &&
360 (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
361 (1 << KEY_FLAG_REVOKED) |
362 (1 << KEY_FLAG_DEAD))))
365 /* this should eventually be an flag in d_flags */
366 spin_lock(&dentry->d_lock);
367 cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
368 spin_unlock(&dentry->d_lock);
369 dir_has_key = (ci != NULL);
373 * If the dentry was cached without the key, and it is a
374 * negative dentry, it might be a valid name. We can't check
375 * if the key has since been made available due to locking
376 * reasons, so we fail the validation so ext4_lookup() can do
379 * We also fail the validation if the dentry was created with
380 * the key present, but we no longer have the key, or vice versa.
382 if ((!cached_with_key && d_is_negative(dentry)) ||
383 (!cached_with_key && dir_has_key) ||
384 (cached_with_key && !dir_has_key))
389 const struct dentry_operations fscrypt_d_ops = {
390 .d_revalidate = fscrypt_d_revalidate,
392 EXPORT_SYMBOL(fscrypt_d_ops);
395 * Call fscrypt_decrypt_page on every single page, reusing the encryption
398 static void completion_pages(struct work_struct *work)
400 struct fscrypt_ctx *ctx =
401 container_of(work, struct fscrypt_ctx, r.work);
402 struct bio *bio = ctx->r.bio;
406 bio_for_each_segment_all(bv, bio, i) {
407 struct page *page = bv->bv_page;
408 int ret = fscrypt_decrypt_page(page);
414 SetPageUptodate(page);
418 fscrypt_release_ctx(ctx);
422 void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *ctx, struct bio *bio)
424 INIT_WORK(&ctx->r.work, completion_pages);
426 queue_work(fscrypt_read_workqueue, &ctx->r.work);
428 EXPORT_SYMBOL(fscrypt_decrypt_bio_pages);
430 void fscrypt_pullback_bio_page(struct page **page, bool restore)
432 struct fscrypt_ctx *ctx;
433 struct page *bounce_page;
435 /* The bounce data pages are unmapped. */
436 if ((*page)->mapping)
439 /* The bounce data page is unmapped. */
441 ctx = (struct fscrypt_ctx *)page_private(bounce_page);
443 /* restore control page */
444 *page = ctx->w.control_page;
447 fscrypt_restore_control_page(bounce_page);
449 EXPORT_SYMBOL(fscrypt_pullback_bio_page);
451 void fscrypt_restore_control_page(struct page *page)
453 struct fscrypt_ctx *ctx;
455 ctx = (struct fscrypt_ctx *)page_private(page);
456 set_page_private(page, (unsigned long)NULL);
457 ClearPagePrivate(page);
459 fscrypt_release_ctx(ctx);
461 EXPORT_SYMBOL(fscrypt_restore_control_page);
463 static void fscrypt_destroy(void)
465 struct fscrypt_ctx *pos, *n;
467 list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
468 kmem_cache_free(fscrypt_ctx_cachep, pos);
469 INIT_LIST_HEAD(&fscrypt_free_ctxs);
470 mempool_destroy(fscrypt_bounce_page_pool);
471 fscrypt_bounce_page_pool = NULL;
475 * fscrypt_initialize() - allocate major buffers for fs encryption.
477 * We only call this when we start accessing encrypted files, since it
478 * results in memory getting allocated that wouldn't otherwise be used.
480 * Return: Zero on success, non-zero otherwise.
482 int fscrypt_initialize(void)
484 int i, res = -ENOMEM;
486 if (fscrypt_bounce_page_pool)
489 mutex_lock(&fscrypt_init_mutex);
490 if (fscrypt_bounce_page_pool)
491 goto already_initialized;
493 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
494 struct fscrypt_ctx *ctx;
496 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
499 list_add(&ctx->free_list, &fscrypt_free_ctxs);
502 fscrypt_bounce_page_pool =
503 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
504 if (!fscrypt_bounce_page_pool)
508 mutex_unlock(&fscrypt_init_mutex);
512 mutex_unlock(&fscrypt_init_mutex);
515 EXPORT_SYMBOL(fscrypt_initialize);
518 * fscrypt_init() - Set up for fs encryption.
520 static int __init fscrypt_init(void)
522 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
524 if (!fscrypt_read_workqueue)
527 fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
528 if (!fscrypt_ctx_cachep)
529 goto fail_free_queue;
531 fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
532 if (!fscrypt_info_cachep)
538 kmem_cache_destroy(fscrypt_ctx_cachep);
540 destroy_workqueue(fscrypt_read_workqueue);
544 module_init(fscrypt_init)
547 * fscrypt_exit() - Shutdown the fs encryption system
549 static void __exit fscrypt_exit(void)
553 if (fscrypt_read_workqueue)
554 destroy_workqueue(fscrypt_read_workqueue);
555 kmem_cache_destroy(fscrypt_ctx_cachep);
556 kmem_cache_destroy(fscrypt_info_cachep);
558 module_exit(fscrypt_exit);
560 MODULE_LICENSE("GPL");