Commit | Line | Data |
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0b81d077 JK |
1 | /* |
2 | * This contains encryption functions for per-file encryption. | |
3 | * | |
4 | * Copyright (C) 2015, Google, Inc. | |
5 | * Copyright (C) 2015, Motorola Mobility | |
6 | * | |
7 | * Written by Michael Halcrow, 2014. | |
8 | * | |
9 | * Filename encryption additions | |
10 | * Uday Savagaonkar, 2014 | |
11 | * Encryption policy handling additions | |
12 | * Ildar Muslukhov, 2014 | |
13 | * Add fscrypt_pullback_bio_page() | |
14 | * Jaegeuk Kim, 2015. | |
15 | * | |
16 | * This has not yet undergone a rigorous security audit. | |
17 | * | |
18 | * The usage of AES-XTS should conform to recommendations in NIST | |
19 | * Special Publication 800-38E and IEEE P1619/D16. | |
20 | */ | |
21 | ||
0b81d077 JK |
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> | |
0b81d077 | 27 | #include <linux/dcache.h> |
03a8bb0e | 28 | #include <linux/namei.h> |
b7e7cf7a | 29 | #include <crypto/aes.h> |
a575784c | 30 | #include <crypto/skcipher.h> |
cc4e0df0 | 31 | #include "fscrypt_private.h" |
0b81d077 JK |
32 | |
33 | static unsigned int num_prealloc_crypto_pages = 32; | |
34 | static unsigned int num_prealloc_crypto_ctxs = 128; | |
35 | ||
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"); | |
42 | ||
43 | static mempool_t *fscrypt_bounce_page_pool = NULL; | |
44 | ||
45 | static LIST_HEAD(fscrypt_free_ctxs); | |
46 | static DEFINE_SPINLOCK(fscrypt_ctx_lock); | |
47 | ||
58ae7468 | 48 | struct workqueue_struct *fscrypt_read_workqueue; |
0b81d077 JK |
49 | static DEFINE_MUTEX(fscrypt_init_mutex); |
50 | ||
51 | static struct kmem_cache *fscrypt_ctx_cachep; | |
52 | struct kmem_cache *fscrypt_info_cachep; | |
53 | ||
54 | /** | |
55 | * fscrypt_release_ctx() - Releases an encryption context | |
56 | * @ctx: The encryption context to release. | |
57 | * | |
58 | * If the encryption context was allocated from the pre-allocated pool, returns | |
59 | * it to that pool. Else, frees it. | |
60 | * | |
61 | * If there's a bounce page in the context, this frees that. | |
62 | */ | |
63 | void fscrypt_release_ctx(struct fscrypt_ctx *ctx) | |
64 | { | |
65 | unsigned long flags; | |
66 | ||
6a34e4d2 | 67 | if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->w.bounce_page) { |
0b81d077 JK |
68 | mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool); |
69 | ctx->w.bounce_page = NULL; | |
70 | } | |
71 | ctx->w.control_page = NULL; | |
72 | if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) { | |
73 | kmem_cache_free(fscrypt_ctx_cachep, ctx); | |
74 | } else { | |
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); | |
78 | } | |
79 | } | |
80 | EXPORT_SYMBOL(fscrypt_release_ctx); | |
81 | ||
82 | /** | |
83 | * fscrypt_get_ctx() - Gets an encryption context | |
84 | * @inode: The inode for which we are doing the crypto | |
b32e4482 | 85 | * @gfp_flags: The gfp flag for memory allocation |
0b81d077 JK |
86 | * |
87 | * Allocates and initializes an encryption context. | |
88 | * | |
89 | * Return: An allocated and initialized encryption context on success; error | |
90 | * value or NULL otherwise. | |
91 | */ | |
0b93e1b9 | 92 | struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode, gfp_t gfp_flags) |
0b81d077 JK |
93 | { |
94 | struct fscrypt_ctx *ctx = NULL; | |
95 | struct fscrypt_info *ci = inode->i_crypt_info; | |
96 | unsigned long flags; | |
97 | ||
98 | if (ci == NULL) | |
99 | return ERR_PTR(-ENOKEY); | |
100 | ||
101 | /* | |
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. | |
110 | */ | |
111 | spin_lock_irqsave(&fscrypt_ctx_lock, flags); | |
112 | ctx = list_first_entry_or_null(&fscrypt_free_ctxs, | |
113 | struct fscrypt_ctx, free_list); | |
114 | if (ctx) | |
115 | list_del(&ctx->free_list); | |
116 | spin_unlock_irqrestore(&fscrypt_ctx_lock, flags); | |
117 | if (!ctx) { | |
b32e4482 | 118 | ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags); |
0b81d077 JK |
119 | if (!ctx) |
120 | return ERR_PTR(-ENOMEM); | |
121 | ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL; | |
122 | } else { | |
123 | ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL; | |
124 | } | |
6a34e4d2 | 125 | ctx->flags &= ~FS_CTX_HAS_BOUNCE_BUFFER_FL; |
0b81d077 JK |
126 | return ctx; |
127 | } | |
128 | EXPORT_SYMBOL(fscrypt_get_ctx); | |
129 | ||
58ae7468 RW |
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) | |
0b81d077 | 134 | { |
fb445437 EB |
135 | struct { |
136 | __le64 index; | |
b7e7cf7a DW |
137 | u8 padding[FS_IV_SIZE - sizeof(__le64)]; |
138 | } iv; | |
d407574e | 139 | struct skcipher_request *req = NULL; |
d0082e1a | 140 | DECLARE_CRYPTO_WAIT(wait); |
0b81d077 JK |
141 | struct scatterlist dst, src; |
142 | struct fscrypt_info *ci = inode->i_crypt_info; | |
d407574e | 143 | struct crypto_skcipher *tfm = ci->ci_ctfm; |
0b81d077 JK |
144 | int res = 0; |
145 | ||
1400451f DG |
146 | BUG_ON(len == 0); |
147 | ||
b7e7cf7a DW |
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)); | |
152 | ||
153 | if (ci->ci_essiv_tfm != NULL) { | |
154 | crypto_cipher_encrypt_one(ci->ci_essiv_tfm, (u8 *)&iv, | |
155 | (u8 *)&iv); | |
156 | } | |
157 | ||
b32e4482 | 158 | req = skcipher_request_alloc(tfm, gfp_flags); |
c90fd775 | 159 | if (!req) |
0b81d077 | 160 | return -ENOMEM; |
0b81d077 | 161 | |
d407574e | 162 | skcipher_request_set_callback( |
0b81d077 | 163 | req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, |
d0082e1a | 164 | crypto_req_done, &wait); |
0b81d077 | 165 | |
0b81d077 | 166 | sg_init_table(&dst, 1); |
1400451f | 167 | sg_set_page(&dst, dest_page, len, offs); |
0b81d077 | 168 | sg_init_table(&src, 1); |
1400451f | 169 | sg_set_page(&src, src_page, len, offs); |
b7e7cf7a | 170 | skcipher_request_set_crypt(req, &src, &dst, len, &iv); |
0b81d077 | 171 | if (rw == FS_DECRYPT) |
d0082e1a | 172 | res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait); |
0b81d077 | 173 | else |
d0082e1a | 174 | res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); |
d407574e | 175 | skcipher_request_free(req); |
0b81d077 JK |
176 | if (res) { |
177 | printk_ratelimited(KERN_ERR | |
d407574e | 178 | "%s: crypto_skcipher_encrypt() returned %d\n", |
0b81d077 JK |
179 | __func__, res); |
180 | return res; | |
181 | } | |
182 | return 0; | |
183 | } | |
184 | ||
58ae7468 RW |
185 | struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx, |
186 | gfp_t gfp_flags) | |
0b81d077 | 187 | { |
b32e4482 | 188 | ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags); |
0b81d077 JK |
189 | if (ctx->w.bounce_page == NULL) |
190 | return ERR_PTR(-ENOMEM); | |
6a34e4d2 | 191 | ctx->flags |= FS_CTX_HAS_BOUNCE_BUFFER_FL; |
0b81d077 JK |
192 | return ctx->w.bounce_page; |
193 | } | |
194 | ||
195 | /** | |
196 | * fscypt_encrypt_page() - Encrypts a page | |
1400451f DG |
197 | * @inode: The inode for which the encryption should take place |
198 | * @page: The page to encrypt. Must be locked for bounce-page | |
199 | * encryption. | |
200 | * @len: Length of data to encrypt in @page and encrypted | |
201 | * data in returned page. | |
202 | * @offs: Offset of data within @page and returned | |
203 | * page holding encrypted data. | |
204 | * @lblk_num: Logical block number. This must be unique for multiple | |
205 | * calls with same inode, except when overwriting | |
206 | * previously written data. | |
207 | * @gfp_flags: The gfp flag for memory allocation | |
0b81d077 | 208 | * |
1400451f DG |
209 | * Encrypts @page using the ctx encryption context. Performs encryption |
210 | * either in-place or into a newly allocated bounce page. | |
211 | * Called on the page write path. | |
0b81d077 | 212 | * |
1400451f DG |
213 | * Bounce page allocation is the default. |
214 | * In this case, the contents of @page are encrypted and stored in an | |
215 | * allocated bounce page. @page has to be locked and the caller must call | |
0b81d077 JK |
216 | * fscrypt_restore_control_page() on the returned ciphertext page to |
217 | * release the bounce buffer and the encryption context. | |
218 | * | |
bd7b8290 | 219 | * In-place encryption is used by setting the FS_CFLG_OWN_PAGES flag in |
1400451f DG |
220 | * fscrypt_operations. Here, the input-page is returned with its content |
221 | * encrypted. | |
222 | * | |
223 | * Return: A page with the encrypted content on success. Else, an | |
0b81d077 JK |
224 | * error value or NULL. |
225 | */ | |
0b93e1b9 | 226 | struct page *fscrypt_encrypt_page(const struct inode *inode, |
1400451f DG |
227 | struct page *page, |
228 | unsigned int len, | |
229 | unsigned int offs, | |
230 | u64 lblk_num, gfp_t gfp_flags) | |
7821d4dd | 231 | |
0b81d077 JK |
232 | { |
233 | struct fscrypt_ctx *ctx; | |
1400451f | 234 | struct page *ciphertext_page = page; |
0b81d077 JK |
235 | int err; |
236 | ||
1400451f | 237 | BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0); |
0b81d077 | 238 | |
bd7b8290 | 239 | if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) { |
9e532772 | 240 | /* with inplace-encryption we just encrypt the page */ |
58ae7468 RW |
241 | err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page, |
242 | ciphertext_page, len, offs, | |
243 | gfp_flags); | |
9e532772 DG |
244 | if (err) |
245 | return ERR_PTR(err); | |
246 | ||
247 | return ciphertext_page; | |
248 | } | |
249 | ||
bd7b8290 DG |
250 | BUG_ON(!PageLocked(page)); |
251 | ||
b32e4482 | 252 | ctx = fscrypt_get_ctx(inode, gfp_flags); |
0b81d077 JK |
253 | if (IS_ERR(ctx)) |
254 | return (struct page *)ctx; | |
255 | ||
9e532772 | 256 | /* The encryption operation will require a bounce page. */ |
58ae7468 | 257 | ciphertext_page = fscrypt_alloc_bounce_page(ctx, gfp_flags); |
9e532772 DG |
258 | if (IS_ERR(ciphertext_page)) |
259 | goto errout; | |
0b81d077 | 260 | |
1400451f | 261 | ctx->w.control_page = page; |
58ae7468 RW |
262 | err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, |
263 | page, ciphertext_page, len, offs, | |
264 | gfp_flags); | |
0b81d077 JK |
265 | if (err) { |
266 | ciphertext_page = ERR_PTR(err); | |
267 | goto errout; | |
268 | } | |
9e532772 DG |
269 | SetPagePrivate(ciphertext_page); |
270 | set_page_private(ciphertext_page, (unsigned long)ctx); | |
271 | lock_page(ciphertext_page); | |
0b81d077 JK |
272 | return ciphertext_page; |
273 | ||
274 | errout: | |
275 | fscrypt_release_ctx(ctx); | |
276 | return ciphertext_page; | |
277 | } | |
278 | EXPORT_SYMBOL(fscrypt_encrypt_page); | |
279 | ||
280 | /** | |
7821d4dd | 281 | * fscrypt_decrypt_page() - Decrypts a page in-place |
1400451f DG |
282 | * @inode: The corresponding inode for the page to decrypt. |
283 | * @page: The page to decrypt. Must be locked in case | |
bd7b8290 | 284 | * it is a writeback page (FS_CFLG_OWN_PAGES unset). |
1400451f DG |
285 | * @len: Number of bytes in @page to be decrypted. |
286 | * @offs: Start of data in @page. | |
287 | * @lblk_num: Logical block number. | |
0b81d077 JK |
288 | * |
289 | * Decrypts page in-place using the ctx encryption context. | |
290 | * | |
291 | * Called from the read completion callback. | |
292 | * | |
293 | * Return: Zero on success, non-zero otherwise. | |
294 | */ | |
0b93e1b9 | 295 | int fscrypt_decrypt_page(const struct inode *inode, struct page *page, |
1400451f | 296 | unsigned int len, unsigned int offs, u64 lblk_num) |
0b81d077 | 297 | { |
bd7b8290 DG |
298 | if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES)) |
299 | BUG_ON(!PageLocked(page)); | |
300 | ||
58ae7468 RW |
301 | return fscrypt_do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page, |
302 | len, offs, GFP_NOFS); | |
0b81d077 JK |
303 | } |
304 | EXPORT_SYMBOL(fscrypt_decrypt_page); | |
305 | ||
0b81d077 JK |
306 | /* |
307 | * Validate dentries for encrypted directories to make sure we aren't | |
308 | * potentially caching stale data after a key has been added or | |
309 | * removed. | |
310 | */ | |
311 | static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags) | |
312 | { | |
d7d75352 | 313 | struct dentry *dir; |
0b81d077 JK |
314 | int dir_has_key, cached_with_key; |
315 | ||
03a8bb0e JK |
316 | if (flags & LOOKUP_RCU) |
317 | return -ECHILD; | |
318 | ||
d7d75352 | 319 | dir = dget_parent(dentry); |
e0428a26 | 320 | if (!IS_ENCRYPTED(d_inode(dir))) { |
d7d75352 | 321 | dput(dir); |
0b81d077 | 322 | return 0; |
d7d75352 | 323 | } |
0b81d077 | 324 | |
0b81d077 JK |
325 | spin_lock(&dentry->d_lock); |
326 | cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY; | |
327 | spin_unlock(&dentry->d_lock); | |
1b53cf98 | 328 | dir_has_key = (d_inode(dir)->i_crypt_info != NULL); |
d7d75352 | 329 | dput(dir); |
0b81d077 JK |
330 | |
331 | /* | |
332 | * If the dentry was cached without the key, and it is a | |
333 | * negative dentry, it might be a valid name. We can't check | |
334 | * if the key has since been made available due to locking | |
335 | * reasons, so we fail the validation so ext4_lookup() can do | |
336 | * this check. | |
337 | * | |
338 | * We also fail the validation if the dentry was created with | |
339 | * the key present, but we no longer have the key, or vice versa. | |
340 | */ | |
341 | if ((!cached_with_key && d_is_negative(dentry)) || | |
342 | (!cached_with_key && dir_has_key) || | |
343 | (cached_with_key && !dir_has_key)) | |
344 | return 0; | |
345 | return 1; | |
346 | } | |
347 | ||
348 | const struct dentry_operations fscrypt_d_ops = { | |
349 | .d_revalidate = fscrypt_d_revalidate, | |
350 | }; | |
0b81d077 | 351 | |
0b81d077 JK |
352 | void fscrypt_restore_control_page(struct page *page) |
353 | { | |
354 | struct fscrypt_ctx *ctx; | |
355 | ||
356 | ctx = (struct fscrypt_ctx *)page_private(page); | |
357 | set_page_private(page, (unsigned long)NULL); | |
358 | ClearPagePrivate(page); | |
359 | unlock_page(page); | |
360 | fscrypt_release_ctx(ctx); | |
361 | } | |
362 | EXPORT_SYMBOL(fscrypt_restore_control_page); | |
363 | ||
364 | static void fscrypt_destroy(void) | |
365 | { | |
366 | struct fscrypt_ctx *pos, *n; | |
367 | ||
368 | list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list) | |
369 | kmem_cache_free(fscrypt_ctx_cachep, pos); | |
370 | INIT_LIST_HEAD(&fscrypt_free_ctxs); | |
371 | mempool_destroy(fscrypt_bounce_page_pool); | |
372 | fscrypt_bounce_page_pool = NULL; | |
373 | } | |
374 | ||
375 | /** | |
376 | * fscrypt_initialize() - allocate major buffers for fs encryption. | |
f32d7ac2 | 377 | * @cop_flags: fscrypt operations flags |
0b81d077 JK |
378 | * |
379 | * We only call this when we start accessing encrypted files, since it | |
380 | * results in memory getting allocated that wouldn't otherwise be used. | |
381 | * | |
382 | * Return: Zero on success, non-zero otherwise. | |
383 | */ | |
f32d7ac2 | 384 | int fscrypt_initialize(unsigned int cop_flags) |
0b81d077 JK |
385 | { |
386 | int i, res = -ENOMEM; | |
387 | ||
a0b3bc85 EB |
388 | /* No need to allocate a bounce page pool if this FS won't use it. */ |
389 | if (cop_flags & FS_CFLG_OWN_PAGES) | |
0b81d077 JK |
390 | return 0; |
391 | ||
392 | mutex_lock(&fscrypt_init_mutex); | |
393 | if (fscrypt_bounce_page_pool) | |
394 | goto already_initialized; | |
395 | ||
396 | for (i = 0; i < num_prealloc_crypto_ctxs; i++) { | |
397 | struct fscrypt_ctx *ctx; | |
398 | ||
399 | ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS); | |
400 | if (!ctx) | |
401 | goto fail; | |
402 | list_add(&ctx->free_list, &fscrypt_free_ctxs); | |
403 | } | |
404 | ||
405 | fscrypt_bounce_page_pool = | |
406 | mempool_create_page_pool(num_prealloc_crypto_pages, 0); | |
407 | if (!fscrypt_bounce_page_pool) | |
408 | goto fail; | |
409 | ||
410 | already_initialized: | |
411 | mutex_unlock(&fscrypt_init_mutex); | |
412 | return 0; | |
413 | fail: | |
414 | fscrypt_destroy(); | |
415 | mutex_unlock(&fscrypt_init_mutex); | |
416 | return res; | |
417 | } | |
0b81d077 JK |
418 | |
419 | /** | |
420 | * fscrypt_init() - Set up for fs encryption. | |
421 | */ | |
422 | static int __init fscrypt_init(void) | |
423 | { | |
36dd26e0 EB |
424 | /* |
425 | * Use an unbound workqueue to allow bios to be decrypted in parallel | |
426 | * even when they happen to complete on the same CPU. This sacrifices | |
427 | * locality, but it's worthwhile since decryption is CPU-intensive. | |
428 | * | |
429 | * Also use a high-priority workqueue to prioritize decryption work, | |
430 | * which blocks reads from completing, over regular application tasks. | |
431 | */ | |
0b81d077 | 432 | fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue", |
36dd26e0 EB |
433 | WQ_UNBOUND | WQ_HIGHPRI, |
434 | num_online_cpus()); | |
0b81d077 JK |
435 | if (!fscrypt_read_workqueue) |
436 | goto fail; | |
437 | ||
438 | fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT); | |
439 | if (!fscrypt_ctx_cachep) | |
440 | goto fail_free_queue; | |
441 | ||
442 | fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT); | |
443 | if (!fscrypt_info_cachep) | |
444 | goto fail_free_ctx; | |
445 | ||
446 | return 0; | |
447 | ||
448 | fail_free_ctx: | |
449 | kmem_cache_destroy(fscrypt_ctx_cachep); | |
450 | fail_free_queue: | |
451 | destroy_workqueue(fscrypt_read_workqueue); | |
452 | fail: | |
453 | return -ENOMEM; | |
454 | } | |
455 | module_init(fscrypt_init) | |
456 | ||
457 | /** | |
458 | * fscrypt_exit() - Shutdown the fs encryption system | |
459 | */ | |
460 | static void __exit fscrypt_exit(void) | |
461 | { | |
462 | fscrypt_destroy(); | |
463 | ||
464 | if (fscrypt_read_workqueue) | |
465 | destroy_workqueue(fscrypt_read_workqueue); | |
466 | kmem_cache_destroy(fscrypt_ctx_cachep); | |
467 | kmem_cache_destroy(fscrypt_info_cachep); | |
b7e7cf7a DW |
468 | |
469 | fscrypt_essiv_cleanup(); | |
0b81d077 JK |
470 | } |
471 | module_exit(fscrypt_exit); | |
472 | ||
473 | MODULE_LICENSE("GPL"); |