1 // SPDX-License-Identifier: GPL-2.0-only
3 * This contains encryption functions for per-file encryption.
5 * Copyright (C) 2015, Google, Inc.
6 * Copyright (C) 2015, Motorola Mobility
8 * Written by Michael Halcrow, 2014.
10 * Filename encryption additions
11 * Uday Savagaonkar, 2014
12 * Encryption policy handling additions
13 * Ildar Muslukhov, 2014
14 * Add fscrypt_pullback_bio_page()
17 * This has not yet undergone a rigorous security audit.
19 * The usage of AES-XTS should conform to recommendations in NIST
20 * Special Publication 800-38E and IEEE P1619/D16.
23 #include <linux/pagemap.h>
24 #include <linux/mempool.h>
25 #include <linux/module.h>
26 #include <linux/scatterlist.h>
27 #include <linux/ratelimit.h>
28 #include <linux/dcache.h>
29 #include <linux/namei.h>
30 #include <crypto/aes.h>
31 #include <crypto/skcipher.h>
32 #include "fscrypt_private.h"
34 static unsigned int num_prealloc_crypto_pages = 32;
35 static unsigned int num_prealloc_crypto_ctxs = 128;
37 module_param(num_prealloc_crypto_pages, uint, 0444);
38 MODULE_PARM_DESC(num_prealloc_crypto_pages,
39 "Number of crypto pages to preallocate");
40 module_param(num_prealloc_crypto_ctxs, uint, 0444);
41 MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
42 "Number of crypto contexts to preallocate");
44 static mempool_t *fscrypt_bounce_page_pool = NULL;
46 static LIST_HEAD(fscrypt_free_ctxs);
47 static DEFINE_SPINLOCK(fscrypt_ctx_lock);
49 static struct workqueue_struct *fscrypt_read_workqueue;
50 static DEFINE_MUTEX(fscrypt_init_mutex);
52 static struct kmem_cache *fscrypt_ctx_cachep;
53 struct kmem_cache *fscrypt_info_cachep;
55 void fscrypt_enqueue_decrypt_work(struct work_struct *work)
57 queue_work(fscrypt_read_workqueue, work);
59 EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);
62 * fscrypt_release_ctx() - Releases an encryption context
63 * @ctx: The encryption context to release.
65 * If the encryption context was allocated from the pre-allocated pool, returns
66 * it to that pool. Else, frees it.
68 * If there's a bounce page in the context, this frees that.
70 void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
74 if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->w.bounce_page) {
75 mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
76 ctx->w.bounce_page = NULL;
78 ctx->w.control_page = NULL;
79 if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
80 kmem_cache_free(fscrypt_ctx_cachep, ctx);
82 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
83 list_add(&ctx->free_list, &fscrypt_free_ctxs);
84 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
87 EXPORT_SYMBOL(fscrypt_release_ctx);
90 * fscrypt_get_ctx() - Gets an encryption context
91 * @gfp_flags: The gfp flag for memory allocation
93 * Allocates and initializes an encryption context.
95 * Return: A new encryption context on success; an ERR_PTR() otherwise.
97 struct fscrypt_ctx *fscrypt_get_ctx(gfp_t gfp_flags)
99 struct fscrypt_ctx *ctx;
103 * We first try getting the ctx from a free list because in
104 * the common case the ctx will have an allocated and
105 * initialized crypto tfm, so it's probably a worthwhile
106 * optimization. For the bounce page, we first try getting it
107 * from the kernel allocator because that's just about as fast
108 * as getting it from a list and because a cache of free pages
109 * should generally be a "last resort" option for a filesystem
110 * to be able to do its job.
112 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
113 ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
114 struct fscrypt_ctx, free_list);
116 list_del(&ctx->free_list);
117 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
119 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
121 return ERR_PTR(-ENOMEM);
122 ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
124 ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
126 ctx->flags &= ~FS_CTX_HAS_BOUNCE_BUFFER_FL;
129 EXPORT_SYMBOL(fscrypt_get_ctx);
131 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
132 const struct fscrypt_info *ci)
134 memset(iv, 0, ci->ci_mode->ivsize);
135 iv->lblk_num = cpu_to_le64(lblk_num);
137 if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY)
138 memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
140 if (ci->ci_essiv_tfm != NULL)
141 crypto_cipher_encrypt_one(ci->ci_essiv_tfm, iv->raw, iv->raw);
144 int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
145 u64 lblk_num, struct page *src_page,
146 struct page *dest_page, unsigned int len,
147 unsigned int offs, gfp_t gfp_flags)
150 struct skcipher_request *req = NULL;
151 DECLARE_CRYPTO_WAIT(wait);
152 struct scatterlist dst, src;
153 struct fscrypt_info *ci = inode->i_crypt_info;
154 struct crypto_skcipher *tfm = ci->ci_ctfm;
159 fscrypt_generate_iv(&iv, lblk_num, ci);
161 req = skcipher_request_alloc(tfm, gfp_flags);
165 skcipher_request_set_callback(
166 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
167 crypto_req_done, &wait);
169 sg_init_table(&dst, 1);
170 sg_set_page(&dst, dest_page, len, offs);
171 sg_init_table(&src, 1);
172 sg_set_page(&src, src_page, len, offs);
173 skcipher_request_set_crypt(req, &src, &dst, len, &iv);
174 if (rw == FS_DECRYPT)
175 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
177 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
178 skcipher_request_free(req);
180 fscrypt_err(inode->i_sb,
181 "%scryption failed for inode %lu, block %llu: %d",
182 (rw == FS_DECRYPT ? "de" : "en"),
183 inode->i_ino, lblk_num, res);
189 struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
192 ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
193 if (ctx->w.bounce_page == NULL)
194 return ERR_PTR(-ENOMEM);
195 ctx->flags |= FS_CTX_HAS_BOUNCE_BUFFER_FL;
196 return ctx->w.bounce_page;
200 * fscypt_encrypt_page() - Encrypts a page
201 * @inode: The inode for which the encryption should take place
202 * @page: The page to encrypt. Must be locked for bounce-page
204 * @len: Length of data to encrypt in @page and encrypted
205 * data in returned page.
206 * @offs: Offset of data within @page and returned
207 * page holding encrypted data.
208 * @lblk_num: Logical block number. This must be unique for multiple
209 * calls with same inode, except when overwriting
210 * previously written data.
211 * @gfp_flags: The gfp flag for memory allocation
213 * Encrypts @page using the ctx encryption context. Performs encryption
214 * either in-place or into a newly allocated bounce page.
215 * Called on the page write path.
217 * Bounce page allocation is the default.
218 * In this case, the contents of @page are encrypted and stored in an
219 * allocated bounce page. @page has to be locked and the caller must call
220 * fscrypt_restore_control_page() on the returned ciphertext page to
221 * release the bounce buffer and the encryption context.
223 * In-place encryption is used by setting the FS_CFLG_OWN_PAGES flag in
224 * fscrypt_operations. Here, the input-page is returned with its content
227 * Return: A page with the encrypted content on success. Else, an
228 * error value or NULL.
230 struct page *fscrypt_encrypt_page(const struct inode *inode,
234 u64 lblk_num, gfp_t gfp_flags)
237 struct fscrypt_ctx *ctx;
238 struct page *ciphertext_page = page;
241 BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);
243 if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) {
244 /* with inplace-encryption we just encrypt the page */
245 err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page,
246 ciphertext_page, len, offs,
251 return ciphertext_page;
254 BUG_ON(!PageLocked(page));
256 ctx = fscrypt_get_ctx(gfp_flags);
258 return ERR_CAST(ctx);
260 /* The encryption operation will require a bounce page. */
261 ciphertext_page = fscrypt_alloc_bounce_page(ctx, gfp_flags);
262 if (IS_ERR(ciphertext_page))
265 ctx->w.control_page = page;
266 err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num,
267 page, ciphertext_page, len, offs,
270 ciphertext_page = ERR_PTR(err);
273 SetPagePrivate(ciphertext_page);
274 set_page_private(ciphertext_page, (unsigned long)ctx);
275 lock_page(ciphertext_page);
276 return ciphertext_page;
279 fscrypt_release_ctx(ctx);
280 return ciphertext_page;
282 EXPORT_SYMBOL(fscrypt_encrypt_page);
285 * fscrypt_decrypt_page() - Decrypts a page in-place
286 * @inode: The corresponding inode for the page to decrypt.
287 * @page: The page to decrypt. Must be locked in case
288 * it is a writeback page (FS_CFLG_OWN_PAGES unset).
289 * @len: Number of bytes in @page to be decrypted.
290 * @offs: Start of data in @page.
291 * @lblk_num: Logical block number.
293 * Decrypts page in-place using the ctx encryption context.
295 * Called from the read completion callback.
297 * Return: Zero on success, non-zero otherwise.
299 int fscrypt_decrypt_page(const struct inode *inode, struct page *page,
300 unsigned int len, unsigned int offs, u64 lblk_num)
302 if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES))
303 BUG_ON(!PageLocked(page));
305 return fscrypt_do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page,
306 len, offs, GFP_NOFS);
308 EXPORT_SYMBOL(fscrypt_decrypt_page);
311 * Validate dentries in encrypted directories to make sure we aren't potentially
312 * caching stale dentries after a key has been added.
314 static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
321 * Plaintext names are always valid, since fscrypt doesn't support
322 * reverting to ciphertext names without evicting the directory's inode
323 * -- which implies eviction of the dentries in the directory.
325 if (!(dentry->d_flags & DCACHE_ENCRYPTED_NAME))
329 * Ciphertext name; valid if the directory's key is still unavailable.
331 * Although fscrypt forbids rename() on ciphertext names, we still must
332 * use dget_parent() here rather than use ->d_parent directly. That's
333 * because a corrupted fs image may contain directory hard links, which
334 * the VFS handles by moving the directory's dentry tree in the dcache
335 * each time ->lookup() finds the directory and it already has a dentry
336 * elsewhere. Thus ->d_parent can be changing, and we must safely grab
337 * a reference to some ->d_parent to prevent it from being freed.
340 if (flags & LOOKUP_RCU)
343 dir = dget_parent(dentry);
344 err = fscrypt_get_encryption_info(d_inode(dir));
345 valid = !fscrypt_has_encryption_key(d_inode(dir));
354 const struct dentry_operations fscrypt_d_ops = {
355 .d_revalidate = fscrypt_d_revalidate,
358 void fscrypt_restore_control_page(struct page *page)
360 struct fscrypt_ctx *ctx;
362 ctx = (struct fscrypt_ctx *)page_private(page);
363 set_page_private(page, (unsigned long)NULL);
364 ClearPagePrivate(page);
366 fscrypt_release_ctx(ctx);
368 EXPORT_SYMBOL(fscrypt_restore_control_page);
370 static void fscrypt_destroy(void)
372 struct fscrypt_ctx *pos, *n;
374 list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
375 kmem_cache_free(fscrypt_ctx_cachep, pos);
376 INIT_LIST_HEAD(&fscrypt_free_ctxs);
377 mempool_destroy(fscrypt_bounce_page_pool);
378 fscrypt_bounce_page_pool = NULL;
382 * fscrypt_initialize() - allocate major buffers for fs encryption.
383 * @cop_flags: fscrypt operations flags
385 * We only call this when we start accessing encrypted files, since it
386 * results in memory getting allocated that wouldn't otherwise be used.
388 * Return: Zero on success, non-zero otherwise.
390 int fscrypt_initialize(unsigned int cop_flags)
392 int i, res = -ENOMEM;
394 /* No need to allocate a bounce page pool if this FS won't use it. */
395 if (cop_flags & FS_CFLG_OWN_PAGES)
398 mutex_lock(&fscrypt_init_mutex);
399 if (fscrypt_bounce_page_pool)
400 goto already_initialized;
402 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
403 struct fscrypt_ctx *ctx;
405 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
408 list_add(&ctx->free_list, &fscrypt_free_ctxs);
411 fscrypt_bounce_page_pool =
412 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
413 if (!fscrypt_bounce_page_pool)
417 mutex_unlock(&fscrypt_init_mutex);
421 mutex_unlock(&fscrypt_init_mutex);
425 void fscrypt_msg(struct super_block *sb, const char *level,
426 const char *fmt, ...)
428 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
429 DEFAULT_RATELIMIT_BURST);
430 struct va_format vaf;
433 if (!__ratelimit(&rs))
440 printk("%sfscrypt (%s): %pV\n", level, sb->s_id, &vaf);
442 printk("%sfscrypt: %pV\n", level, &vaf);
447 * fscrypt_init() - Set up for fs encryption.
449 static int __init fscrypt_init(void)
452 * Use an unbound workqueue to allow bios to be decrypted in parallel
453 * even when they happen to complete on the same CPU. This sacrifices
454 * locality, but it's worthwhile since decryption is CPU-intensive.
456 * Also use a high-priority workqueue to prioritize decryption work,
457 * which blocks reads from completing, over regular application tasks.
459 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
460 WQ_UNBOUND | WQ_HIGHPRI,
462 if (!fscrypt_read_workqueue)
465 fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
466 if (!fscrypt_ctx_cachep)
467 goto fail_free_queue;
469 fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
470 if (!fscrypt_info_cachep)
476 kmem_cache_destroy(fscrypt_ctx_cachep);
478 destroy_workqueue(fscrypt_read_workqueue);
482 module_init(fscrypt_init)
485 * fscrypt_exit() - Shutdown the fs encryption system
487 static void __exit fscrypt_exit(void)
491 if (fscrypt_read_workqueue)
492 destroy_workqueue(fscrypt_read_workqueue);
493 kmem_cache_destroy(fscrypt_ctx_cachep);
494 kmem_cache_destroy(fscrypt_info_cachep);
496 fscrypt_essiv_cleanup();
498 module_exit(fscrypt_exit);
500 MODULE_LICENSE("GPL");