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/dcache.h>
28 #include <linux/namei.h>
29 #include <crypto/aes.h>
30 #include <crypto/skcipher.h>
31 #include "fscrypt_private.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 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_CTX_HAS_BOUNCE_BUFFER_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
85 * @gfp_flags: The gfp flag for memory allocation
87 * Allocates and initializes an encryption context.
89 * Return: An allocated and initialized encryption context on success; error
90 * value or NULL otherwise.
92 struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode, gfp_t gfp_flags)
94 struct fscrypt_ctx *ctx = NULL;
95 struct fscrypt_info *ci = inode->i_crypt_info;
99 return ERR_PTR(-ENOKEY);
102 * We first try getting the ctx from a free list because in
103 * the common case the ctx will have an allocated and
104 * initialized crypto tfm, so it's probably a worthwhile
105 * optimization. For the bounce page, we first try getting it
106 * from the kernel allocator because that's just about as fast
107 * as getting it from a list and because a cache of free pages
108 * should generally be a "last resort" option for a filesystem
109 * to be able to do its job.
111 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
112 ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
113 struct fscrypt_ctx, free_list);
115 list_del(&ctx->free_list);
116 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
118 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
120 return ERR_PTR(-ENOMEM);
121 ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
123 ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
125 ctx->flags &= ~FS_CTX_HAS_BOUNCE_BUFFER_FL;
128 EXPORT_SYMBOL(fscrypt_get_ctx);
130 int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
131 u64 lblk_num, struct page *src_page,
132 struct page *dest_page, unsigned int len,
133 unsigned int offs, gfp_t gfp_flags)
137 u8 padding[FS_IV_SIZE - sizeof(__le64)];
139 struct skcipher_request *req = NULL;
140 DECLARE_CRYPTO_WAIT(wait);
141 struct scatterlist dst, src;
142 struct fscrypt_info *ci = inode->i_crypt_info;
143 struct crypto_skcipher *tfm = ci->ci_ctfm;
148 BUILD_BUG_ON(sizeof(iv) != FS_IV_SIZE);
149 BUILD_BUG_ON(AES_BLOCK_SIZE != FS_IV_SIZE);
150 iv.index = cpu_to_le64(lblk_num);
151 memset(iv.padding, 0, sizeof(iv.padding));
153 if (ci->ci_essiv_tfm != NULL) {
154 crypto_cipher_encrypt_one(ci->ci_essiv_tfm, (u8 *)&iv,
158 req = skcipher_request_alloc(tfm, gfp_flags);
162 skcipher_request_set_callback(
163 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
164 crypto_req_done, &wait);
166 sg_init_table(&dst, 1);
167 sg_set_page(&dst, dest_page, len, offs);
168 sg_init_table(&src, 1);
169 sg_set_page(&src, src_page, len, offs);
170 skcipher_request_set_crypt(req, &src, &dst, len, &iv);
171 if (rw == FS_DECRYPT)
172 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
174 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
175 skcipher_request_free(req);
177 fscrypt_err(inode->i_sb,
178 "%scryption failed for inode %lu, block %llu: %d",
179 (rw == FS_DECRYPT ? "de" : "en"),
180 inode->i_ino, lblk_num, res);
186 struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
189 ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
190 if (ctx->w.bounce_page == NULL)
191 return ERR_PTR(-ENOMEM);
192 ctx->flags |= FS_CTX_HAS_BOUNCE_BUFFER_FL;
193 return ctx->w.bounce_page;
197 * fscypt_encrypt_page() - Encrypts a page
198 * @inode: The inode for which the encryption should take place
199 * @page: The page to encrypt. Must be locked for bounce-page
201 * @len: Length of data to encrypt in @page and encrypted
202 * data in returned page.
203 * @offs: Offset of data within @page and returned
204 * page holding encrypted data.
205 * @lblk_num: Logical block number. This must be unique for multiple
206 * calls with same inode, except when overwriting
207 * previously written data.
208 * @gfp_flags: The gfp flag for memory allocation
210 * Encrypts @page using the ctx encryption context. Performs encryption
211 * either in-place or into a newly allocated bounce page.
212 * Called on the page write path.
214 * Bounce page allocation is the default.
215 * In this case, the contents of @page are encrypted and stored in an
216 * allocated bounce page. @page has to be locked and the caller must call
217 * fscrypt_restore_control_page() on the returned ciphertext page to
218 * release the bounce buffer and the encryption context.
220 * In-place encryption is used by setting the FS_CFLG_OWN_PAGES flag in
221 * fscrypt_operations. Here, the input-page is returned with its content
224 * Return: A page with the encrypted content on success. Else, an
225 * error value or NULL.
227 struct page *fscrypt_encrypt_page(const struct inode *inode,
231 u64 lblk_num, gfp_t gfp_flags)
234 struct fscrypt_ctx *ctx;
235 struct page *ciphertext_page = page;
238 BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);
240 if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) {
241 /* with inplace-encryption we just encrypt the page */
242 err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page,
243 ciphertext_page, len, offs,
248 return ciphertext_page;
251 BUG_ON(!PageLocked(page));
253 ctx = fscrypt_get_ctx(inode, gfp_flags);
255 return (struct page *)ctx;
257 /* The encryption operation will require a bounce page. */
258 ciphertext_page = fscrypt_alloc_bounce_page(ctx, gfp_flags);
259 if (IS_ERR(ciphertext_page))
262 ctx->w.control_page = page;
263 err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num,
264 page, ciphertext_page, len, offs,
267 ciphertext_page = ERR_PTR(err);
270 SetPagePrivate(ciphertext_page);
271 set_page_private(ciphertext_page, (unsigned long)ctx);
272 lock_page(ciphertext_page);
273 return ciphertext_page;
276 fscrypt_release_ctx(ctx);
277 return ciphertext_page;
279 EXPORT_SYMBOL(fscrypt_encrypt_page);
282 * fscrypt_decrypt_page() - Decrypts a page in-place
283 * @inode: The corresponding inode for the page to decrypt.
284 * @page: The page to decrypt. Must be locked in case
285 * it is a writeback page (FS_CFLG_OWN_PAGES unset).
286 * @len: Number of bytes in @page to be decrypted.
287 * @offs: Start of data in @page.
288 * @lblk_num: Logical block number.
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, u64 lblk_num)
299 if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES))
300 BUG_ON(!PageLocked(page));
302 return fscrypt_do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page,
303 len, offs, GFP_NOFS);
305 EXPORT_SYMBOL(fscrypt_decrypt_page);
308 * Validate dentries for encrypted directories to make sure we aren't
309 * potentially caching stale data after a key has been added or
312 static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
315 int dir_has_key, cached_with_key;
317 if (flags & LOOKUP_RCU)
320 dir = dget_parent(dentry);
321 if (!IS_ENCRYPTED(d_inode(dir))) {
326 spin_lock(&dentry->d_lock);
327 cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
328 spin_unlock(&dentry->d_lock);
329 dir_has_key = (d_inode(dir)->i_crypt_info != NULL);
333 * If the dentry was cached without the key, and it is a
334 * negative dentry, it might be a valid name. We can't check
335 * if the key has since been made available due to locking
336 * reasons, so we fail the validation so ext4_lookup() can do
339 * We also fail the validation if the dentry was created with
340 * the key present, but we no longer have the key, or vice versa.
342 if ((!cached_with_key && d_is_negative(dentry)) ||
343 (!cached_with_key && dir_has_key) ||
344 (cached_with_key && !dir_has_key))
349 const struct dentry_operations fscrypt_d_ops = {
350 .d_revalidate = fscrypt_d_revalidate,
353 void fscrypt_restore_control_page(struct page *page)
355 struct fscrypt_ctx *ctx;
357 ctx = (struct fscrypt_ctx *)page_private(page);
358 set_page_private(page, (unsigned long)NULL);
359 ClearPagePrivate(page);
361 fscrypt_release_ctx(ctx);
363 EXPORT_SYMBOL(fscrypt_restore_control_page);
365 static void fscrypt_destroy(void)
367 struct fscrypt_ctx *pos, *n;
369 list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
370 kmem_cache_free(fscrypt_ctx_cachep, pos);
371 INIT_LIST_HEAD(&fscrypt_free_ctxs);
372 mempool_destroy(fscrypt_bounce_page_pool);
373 fscrypt_bounce_page_pool = NULL;
377 * fscrypt_initialize() - allocate major buffers for fs encryption.
378 * @cop_flags: fscrypt operations flags
380 * We only call this when we start accessing encrypted files, since it
381 * results in memory getting allocated that wouldn't otherwise be used.
383 * Return: Zero on success, non-zero otherwise.
385 int fscrypt_initialize(unsigned int cop_flags)
387 int i, res = -ENOMEM;
389 /* No need to allocate a bounce page pool if this FS won't use it. */
390 if (cop_flags & FS_CFLG_OWN_PAGES)
393 mutex_lock(&fscrypt_init_mutex);
394 if (fscrypt_bounce_page_pool)
395 goto already_initialized;
397 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
398 struct fscrypt_ctx *ctx;
400 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
403 list_add(&ctx->free_list, &fscrypt_free_ctxs);
406 fscrypt_bounce_page_pool =
407 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
408 if (!fscrypt_bounce_page_pool)
412 mutex_unlock(&fscrypt_init_mutex);
416 mutex_unlock(&fscrypt_init_mutex);
420 void fscrypt_msg(struct super_block *sb, const char *level,
421 const char *fmt, ...)
423 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
424 DEFAULT_RATELIMIT_BURST);
425 struct va_format vaf;
428 if (!__ratelimit(&rs))
435 printk("%sfscrypt (%s): %pV\n", level, sb->s_id, &vaf);
437 printk("%sfscrypt: %pV\n", level, &vaf);
442 * fscrypt_init() - Set up for fs encryption.
444 static int __init fscrypt_init(void)
447 * Use an unbound workqueue to allow bios to be decrypted in parallel
448 * even when they happen to complete on the same CPU. This sacrifices
449 * locality, but it's worthwhile since decryption is CPU-intensive.
451 * Also use a high-priority workqueue to prioritize decryption work,
452 * which blocks reads from completing, over regular application tasks.
454 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
455 WQ_UNBOUND | WQ_HIGHPRI,
457 if (!fscrypt_read_workqueue)
460 fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
461 if (!fscrypt_ctx_cachep)
462 goto fail_free_queue;
464 fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
465 if (!fscrypt_info_cachep)
471 kmem_cache_destroy(fscrypt_ctx_cachep);
473 destroy_workqueue(fscrypt_read_workqueue);
477 module_init(fscrypt_init)
480 * fscrypt_exit() - Shutdown the fs encryption system
482 static void __exit fscrypt_exit(void)
486 if (fscrypt_read_workqueue)
487 destroy_workqueue(fscrypt_read_workqueue);
488 kmem_cache_destroy(fscrypt_ctx_cachep);
489 kmem_cache_destroy(fscrypt_info_cachep);
491 fscrypt_essiv_cleanup();
493 module_exit(fscrypt_exit);
495 MODULE_LICENSE("GPL");