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/namei.h>
30 #include <linux/fscrypto.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
84 * @gfp_flags: The gfp flag for memory allocation
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(const struct inode *inode, gfp_t gfp_flags)
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_flags);
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 * page_crypt_complete() - completion callback for page crypto
131 * @req: The asynchronous cipher request context
132 * @res: The result of the cipher operation
134 static void page_crypt_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(const struct inode *inode,
150 fscrypt_direction_t rw, pgoff_t index,
151 struct page *src_page, struct page *dest_page,
152 unsigned int src_len, unsigned int src_offset,
157 u8 padding[FS_XTS_TWEAK_SIZE - sizeof(__le64)];
159 struct skcipher_request *req = NULL;
160 DECLARE_FS_COMPLETION_RESULT(ecr);
161 struct scatterlist dst, src;
162 struct fscrypt_info *ci = inode->i_crypt_info;
163 struct crypto_skcipher *tfm = ci->ci_ctfm;
166 req = skcipher_request_alloc(tfm, gfp_flags);
168 printk_ratelimited(KERN_ERR
169 "%s: crypto_request_alloc() failed\n",
174 skcipher_request_set_callback(
175 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
176 page_crypt_complete, &ecr);
178 BUILD_BUG_ON(sizeof(xts_tweak) != FS_XTS_TWEAK_SIZE);
179 xts_tweak.index = cpu_to_le64(index);
180 memset(xts_tweak.padding, 0, sizeof(xts_tweak.padding));
182 sg_init_table(&dst, 1);
183 sg_set_page(&dst, dest_page, src_len, src_offset);
184 sg_init_table(&src, 1);
185 sg_set_page(&src, src_page, src_len, src_offset);
186 skcipher_request_set_crypt(req, &src, &dst, src_len, &xts_tweak);
187 if (rw == FS_DECRYPT)
188 res = crypto_skcipher_decrypt(req);
190 res = crypto_skcipher_encrypt(req);
191 if (res == -EINPROGRESS || res == -EBUSY) {
192 BUG_ON(req->base.data != &ecr);
193 wait_for_completion(&ecr.completion);
196 skcipher_request_free(req);
198 printk_ratelimited(KERN_ERR
199 "%s: crypto_skcipher_encrypt() returned %d\n",
206 static struct page *alloc_bounce_page(struct fscrypt_ctx *ctx, gfp_t gfp_flags)
208 ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
209 if (ctx->w.bounce_page == NULL)
210 return ERR_PTR(-ENOMEM);
211 ctx->flags |= FS_WRITE_PATH_FL;
212 return ctx->w.bounce_page;
216 * fscypt_encrypt_page() - Encrypts a page
217 * @inode: The inode for which the encryption should take place
218 * @plaintext_page: The page to encrypt. Must be locked.
219 * @plaintext_len: Length of plaintext within page
220 * @plaintext_offset: Offset of plaintext within page
221 * @index: Index for encryption. This is mainly the page index, but
222 * but might be different for multiple calls on same page.
223 * @gfp_flags: The gfp flag for memory allocation
225 * Encrypts plaintext_page using the ctx encryption context. If
226 * the filesystem supports it, encryption is performed in-place, otherwise a
227 * new ciphertext_page is allocated and returned.
229 * Called on the page write path. The caller must call
230 * fscrypt_restore_control_page() on the returned ciphertext page to
231 * release the bounce buffer and the encryption context.
233 * Return: An allocated page with the encrypted content on success. Else, an
234 * error value or NULL.
236 struct page *fscrypt_encrypt_page(const struct inode *inode,
237 struct page *plaintext_page,
238 unsigned int plaintext_len,
239 unsigned int plaintext_offset,
240 pgoff_t index, gfp_t gfp_flags)
243 struct fscrypt_ctx *ctx;
244 struct page *ciphertext_page = plaintext_page;
247 BUG_ON(plaintext_len % FS_CRYPTO_BLOCK_SIZE != 0);
249 ctx = fscrypt_get_ctx(inode, gfp_flags);
251 return (struct page *)ctx;
253 if (!(inode->i_sb->s_cop->flags & FS_CFLG_INPLACE_ENCRYPTION)) {
254 /* The encryption operation will require a bounce page. */
255 ciphertext_page = alloc_bounce_page(ctx, gfp_flags);
256 if (IS_ERR(ciphertext_page))
260 ctx->w.control_page = plaintext_page;
261 err = do_page_crypto(inode, FS_ENCRYPT, index,
262 plaintext_page, ciphertext_page,
263 plaintext_len, plaintext_offset,
266 ciphertext_page = ERR_PTR(err);
269 if (!(inode->i_sb->s_cop->flags & FS_CFLG_INPLACE_ENCRYPTION)) {
270 SetPagePrivate(ciphertext_page);
271 set_page_private(ciphertext_page, (unsigned long)ctx);
272 lock_page(ciphertext_page);
274 return ciphertext_page;
277 fscrypt_release_ctx(ctx);
278 return ciphertext_page;
280 EXPORT_SYMBOL(fscrypt_encrypt_page);
283 * fscrypt_decrypt_page() - Decrypts a page in-place
284 * @inode: Encrypted inode to decrypt.
285 * @page: The page to decrypt. Must be locked.
286 * @len: Number of bytes in @page to be decrypted.
287 * @offs: Start of data in @page.
288 * @index: Index for encryption.
290 * Decrypts page in-place using the ctx encryption context.
292 * Called from the read completion callback.
294 * Return: Zero on success, non-zero otherwise.
296 int fscrypt_decrypt_page(const struct inode *inode, struct page *page,
297 unsigned int len, unsigned int offs, pgoff_t index)
299 return do_page_crypto(inode, FS_DECRYPT, page->index, page, page, len, offs,
302 EXPORT_SYMBOL(fscrypt_decrypt_page);
304 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
305 sector_t pblk, unsigned int len)
307 struct fscrypt_ctx *ctx;
308 struct page *ciphertext_page = NULL;
312 BUG_ON(inode->i_sb->s_blocksize != PAGE_SIZE);
314 ctx = fscrypt_get_ctx(inode, GFP_NOFS);
318 ciphertext_page = alloc_bounce_page(ctx, GFP_NOWAIT);
319 if (IS_ERR(ciphertext_page)) {
320 err = PTR_ERR(ciphertext_page);
325 err = do_page_crypto(inode, FS_ENCRYPT, lblk,
326 ZERO_PAGE(0), ciphertext_page,
327 PAGE_SIZE, 0, GFP_NOFS);
331 bio = bio_alloc(GFP_NOWAIT, 1);
336 bio->bi_bdev = inode->i_sb->s_bdev;
337 bio->bi_iter.bi_sector =
338 pblk << (inode->i_sb->s_blocksize_bits - 9);
339 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
340 ret = bio_add_page(bio, ciphertext_page,
341 inode->i_sb->s_blocksize, 0);
342 if (ret != inode->i_sb->s_blocksize) {
343 /* should never happen! */
349 err = submit_bio_wait(bio);
350 if ((err == 0) && bio->bi_error)
360 fscrypt_release_ctx(ctx);
363 EXPORT_SYMBOL(fscrypt_zeroout_range);
366 * Validate dentries for encrypted directories to make sure we aren't
367 * potentially caching stale data after a key has been added or
370 static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
373 struct fscrypt_info *ci;
374 int dir_has_key, cached_with_key;
376 if (flags & LOOKUP_RCU)
379 dir = dget_parent(dentry);
380 if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
385 ci = d_inode(dir)->i_crypt_info;
386 if (ci && ci->ci_keyring_key &&
387 (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
388 (1 << KEY_FLAG_REVOKED) |
389 (1 << KEY_FLAG_DEAD))))
392 /* this should eventually be an flag in d_flags */
393 spin_lock(&dentry->d_lock);
394 cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
395 spin_unlock(&dentry->d_lock);
396 dir_has_key = (ci != NULL);
400 * If the dentry was cached without the key, and it is a
401 * negative dentry, it might be a valid name. We can't check
402 * if the key has since been made available due to locking
403 * reasons, so we fail the validation so ext4_lookup() can do
406 * We also fail the validation if the dentry was created with
407 * the key present, but we no longer have the key, or vice versa.
409 if ((!cached_with_key && d_is_negative(dentry)) ||
410 (!cached_with_key && dir_has_key) ||
411 (cached_with_key && !dir_has_key))
416 const struct dentry_operations fscrypt_d_ops = {
417 .d_revalidate = fscrypt_d_revalidate,
419 EXPORT_SYMBOL(fscrypt_d_ops);
422 * Call fscrypt_decrypt_page on every single page, reusing the encryption
425 static void completion_pages(struct work_struct *work)
427 struct fscrypt_ctx *ctx =
428 container_of(work, struct fscrypt_ctx, r.work);
429 struct bio *bio = ctx->r.bio;
433 bio_for_each_segment_all(bv, bio, i) {
434 struct page *page = bv->bv_page;
435 int ret = fscrypt_decrypt_page(page->mapping->host, page,
436 PAGE_SIZE, 0, page->index);
442 SetPageUptodate(page);
446 fscrypt_release_ctx(ctx);
450 void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *ctx, struct bio *bio)
452 INIT_WORK(&ctx->r.work, completion_pages);
454 queue_work(fscrypt_read_workqueue, &ctx->r.work);
456 EXPORT_SYMBOL(fscrypt_decrypt_bio_pages);
458 void fscrypt_pullback_bio_page(struct page **page, bool restore)
460 struct fscrypt_ctx *ctx;
461 struct page *bounce_page;
463 /* The bounce data pages are unmapped. */
464 if ((*page)->mapping)
467 /* The bounce data page is unmapped. */
469 ctx = (struct fscrypt_ctx *)page_private(bounce_page);
471 /* restore control page */
472 *page = ctx->w.control_page;
475 fscrypt_restore_control_page(bounce_page);
477 EXPORT_SYMBOL(fscrypt_pullback_bio_page);
479 void fscrypt_restore_control_page(struct page *page)
481 struct fscrypt_ctx *ctx;
483 ctx = (struct fscrypt_ctx *)page_private(page);
484 set_page_private(page, (unsigned long)NULL);
485 ClearPagePrivate(page);
487 fscrypt_release_ctx(ctx);
489 EXPORT_SYMBOL(fscrypt_restore_control_page);
491 static void fscrypt_destroy(void)
493 struct fscrypt_ctx *pos, *n;
495 list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
496 kmem_cache_free(fscrypt_ctx_cachep, pos);
497 INIT_LIST_HEAD(&fscrypt_free_ctxs);
498 mempool_destroy(fscrypt_bounce_page_pool);
499 fscrypt_bounce_page_pool = NULL;
503 * fscrypt_initialize() - allocate major buffers for fs encryption.
505 * We only call this when we start accessing encrypted files, since it
506 * results in memory getting allocated that wouldn't otherwise be used.
508 * Return: Zero on success, non-zero otherwise.
510 int fscrypt_initialize(void)
512 int i, res = -ENOMEM;
514 if (fscrypt_bounce_page_pool)
517 mutex_lock(&fscrypt_init_mutex);
518 if (fscrypt_bounce_page_pool)
519 goto already_initialized;
521 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
522 struct fscrypt_ctx *ctx;
524 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
527 list_add(&ctx->free_list, &fscrypt_free_ctxs);
530 fscrypt_bounce_page_pool =
531 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
532 if (!fscrypt_bounce_page_pool)
536 mutex_unlock(&fscrypt_init_mutex);
540 mutex_unlock(&fscrypt_init_mutex);
543 EXPORT_SYMBOL(fscrypt_initialize);
546 * fscrypt_init() - Set up for fs encryption.
548 static int __init fscrypt_init(void)
550 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
552 if (!fscrypt_read_workqueue)
555 fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
556 if (!fscrypt_ctx_cachep)
557 goto fail_free_queue;
559 fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
560 if (!fscrypt_info_cachep)
566 kmem_cache_destroy(fscrypt_ctx_cachep);
568 destroy_workqueue(fscrypt_read_workqueue);
572 module_init(fscrypt_init)
575 * fscrypt_exit() - Shutdown the fs encryption system
577 static void __exit fscrypt_exit(void)
581 if (fscrypt_read_workqueue)
582 destroy_workqueue(fscrypt_read_workqueue);
583 kmem_cache_destroy(fscrypt_ctx_cachep);
584 kmem_cache_destroy(fscrypt_info_cachep);
586 module_exit(fscrypt_exit);
588 MODULE_LICENSE("GPL");