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); |
0b81d077 JK |
159 | if (!req) { |
160 | printk_ratelimited(KERN_ERR | |
161 | "%s: crypto_request_alloc() failed\n", | |
162 | __func__); | |
163 | return -ENOMEM; | |
164 | } | |
165 | ||
d407574e | 166 | skcipher_request_set_callback( |
0b81d077 | 167 | req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, |
d0082e1a | 168 | crypto_req_done, &wait); |
0b81d077 | 169 | |
0b81d077 | 170 | sg_init_table(&dst, 1); |
1400451f | 171 | sg_set_page(&dst, dest_page, len, offs); |
0b81d077 | 172 | sg_init_table(&src, 1); |
1400451f | 173 | sg_set_page(&src, src_page, len, offs); |
b7e7cf7a | 174 | skcipher_request_set_crypt(req, &src, &dst, len, &iv); |
0b81d077 | 175 | if (rw == FS_DECRYPT) |
d0082e1a | 176 | res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait); |
0b81d077 | 177 | else |
d0082e1a | 178 | res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); |
d407574e | 179 | skcipher_request_free(req); |
0b81d077 JK |
180 | if (res) { |
181 | printk_ratelimited(KERN_ERR | |
d407574e | 182 | "%s: crypto_skcipher_encrypt() returned %d\n", |
0b81d077 JK |
183 | __func__, res); |
184 | return res; | |
185 | } | |
186 | return 0; | |
187 | } | |
188 | ||
58ae7468 RW |
189 | struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx, |
190 | gfp_t gfp_flags) | |
0b81d077 | 191 | { |
b32e4482 | 192 | ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags); |
0b81d077 JK |
193 | if (ctx->w.bounce_page == NULL) |
194 | return ERR_PTR(-ENOMEM); | |
6a34e4d2 | 195 | ctx->flags |= FS_CTX_HAS_BOUNCE_BUFFER_FL; |
0b81d077 JK |
196 | return ctx->w.bounce_page; |
197 | } | |
198 | ||
199 | /** | |
200 | * fscypt_encrypt_page() - Encrypts a page | |
1400451f DG |
201 | * @inode: The inode for which the encryption should take place |
202 | * @page: The page to encrypt. Must be locked for bounce-page | |
203 | * encryption. | |
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 | |
0b81d077 | 212 | * |
1400451f DG |
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. | |
0b81d077 | 216 | * |
1400451f DG |
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 | |
0b81d077 JK |
220 | * fscrypt_restore_control_page() on the returned ciphertext page to |
221 | * release the bounce buffer and the encryption context. | |
222 | * | |
bd7b8290 | 223 | * In-place encryption is used by setting the FS_CFLG_OWN_PAGES flag in |
1400451f DG |
224 | * fscrypt_operations. Here, the input-page is returned with its content |
225 | * encrypted. | |
226 | * | |
227 | * Return: A page with the encrypted content on success. Else, an | |
0b81d077 JK |
228 | * error value or NULL. |
229 | */ | |
0b93e1b9 | 230 | struct page *fscrypt_encrypt_page(const struct inode *inode, |
1400451f DG |
231 | struct page *page, |
232 | unsigned int len, | |
233 | unsigned int offs, | |
234 | u64 lblk_num, gfp_t gfp_flags) | |
7821d4dd | 235 | |
0b81d077 JK |
236 | { |
237 | struct fscrypt_ctx *ctx; | |
1400451f | 238 | struct page *ciphertext_page = page; |
0b81d077 JK |
239 | int err; |
240 | ||
1400451f | 241 | BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0); |
0b81d077 | 242 | |
bd7b8290 | 243 | if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) { |
9e532772 | 244 | /* with inplace-encryption we just encrypt the page */ |
58ae7468 RW |
245 | err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page, |
246 | ciphertext_page, len, offs, | |
247 | gfp_flags); | |
9e532772 DG |
248 | if (err) |
249 | return ERR_PTR(err); | |
250 | ||
251 | return ciphertext_page; | |
252 | } | |
253 | ||
bd7b8290 DG |
254 | BUG_ON(!PageLocked(page)); |
255 | ||
b32e4482 | 256 | ctx = fscrypt_get_ctx(inode, gfp_flags); |
0b81d077 JK |
257 | if (IS_ERR(ctx)) |
258 | return (struct page *)ctx; | |
259 | ||
9e532772 | 260 | /* The encryption operation will require a bounce page. */ |
58ae7468 | 261 | ciphertext_page = fscrypt_alloc_bounce_page(ctx, gfp_flags); |
9e532772 DG |
262 | if (IS_ERR(ciphertext_page)) |
263 | goto errout; | |
0b81d077 | 264 | |
1400451f | 265 | ctx->w.control_page = page; |
58ae7468 RW |
266 | err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, |
267 | page, ciphertext_page, len, offs, | |
268 | gfp_flags); | |
0b81d077 JK |
269 | if (err) { |
270 | ciphertext_page = ERR_PTR(err); | |
271 | goto errout; | |
272 | } | |
9e532772 DG |
273 | SetPagePrivate(ciphertext_page); |
274 | set_page_private(ciphertext_page, (unsigned long)ctx); | |
275 | lock_page(ciphertext_page); | |
0b81d077 JK |
276 | return ciphertext_page; |
277 | ||
278 | errout: | |
279 | fscrypt_release_ctx(ctx); | |
280 | return ciphertext_page; | |
281 | } | |
282 | EXPORT_SYMBOL(fscrypt_encrypt_page); | |
283 | ||
284 | /** | |
7821d4dd | 285 | * fscrypt_decrypt_page() - Decrypts a page in-place |
1400451f DG |
286 | * @inode: The corresponding inode for the page to decrypt. |
287 | * @page: The page to decrypt. Must be locked in case | |
bd7b8290 | 288 | * it is a writeback page (FS_CFLG_OWN_PAGES unset). |
1400451f DG |
289 | * @len: Number of bytes in @page to be decrypted. |
290 | * @offs: Start of data in @page. | |
291 | * @lblk_num: Logical block number. | |
0b81d077 JK |
292 | * |
293 | * Decrypts page in-place using the ctx encryption context. | |
294 | * | |
295 | * Called from the read completion callback. | |
296 | * | |
297 | * Return: Zero on success, non-zero otherwise. | |
298 | */ | |
0b93e1b9 | 299 | int fscrypt_decrypt_page(const struct inode *inode, struct page *page, |
1400451f | 300 | unsigned int len, unsigned int offs, u64 lblk_num) |
0b81d077 | 301 | { |
bd7b8290 DG |
302 | if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES)) |
303 | BUG_ON(!PageLocked(page)); | |
304 | ||
58ae7468 RW |
305 | return fscrypt_do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page, |
306 | len, offs, GFP_NOFS); | |
0b81d077 JK |
307 | } |
308 | EXPORT_SYMBOL(fscrypt_decrypt_page); | |
309 | ||
0b81d077 JK |
310 | /* |
311 | * Validate dentries for encrypted directories to make sure we aren't | |
312 | * potentially caching stale data after a key has been added or | |
313 | * removed. | |
314 | */ | |
315 | static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags) | |
316 | { | |
d7d75352 | 317 | struct dentry *dir; |
0b81d077 JK |
318 | int dir_has_key, cached_with_key; |
319 | ||
03a8bb0e JK |
320 | if (flags & LOOKUP_RCU) |
321 | return -ECHILD; | |
322 | ||
d7d75352 | 323 | dir = dget_parent(dentry); |
e0428a26 | 324 | if (!IS_ENCRYPTED(d_inode(dir))) { |
d7d75352 | 325 | dput(dir); |
0b81d077 | 326 | return 0; |
d7d75352 | 327 | } |
0b81d077 | 328 | |
0b81d077 JK |
329 | /* this should eventually be an flag in d_flags */ |
330 | spin_lock(&dentry->d_lock); | |
331 | cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY; | |
332 | spin_unlock(&dentry->d_lock); | |
1b53cf98 | 333 | dir_has_key = (d_inode(dir)->i_crypt_info != NULL); |
d7d75352 | 334 | dput(dir); |
0b81d077 JK |
335 | |
336 | /* | |
337 | * If the dentry was cached without the key, and it is a | |
338 | * negative dentry, it might be a valid name. We can't check | |
339 | * if the key has since been made available due to locking | |
340 | * reasons, so we fail the validation so ext4_lookup() can do | |
341 | * this check. | |
342 | * | |
343 | * We also fail the validation if the dentry was created with | |
344 | * the key present, but we no longer have the key, or vice versa. | |
345 | */ | |
346 | if ((!cached_with_key && d_is_negative(dentry)) || | |
347 | (!cached_with_key && dir_has_key) || | |
348 | (cached_with_key && !dir_has_key)) | |
349 | return 0; | |
350 | return 1; | |
351 | } | |
352 | ||
353 | const struct dentry_operations fscrypt_d_ops = { | |
354 | .d_revalidate = fscrypt_d_revalidate, | |
355 | }; | |
356 | EXPORT_SYMBOL(fscrypt_d_ops); | |
357 | ||
0b81d077 JK |
358 | void fscrypt_restore_control_page(struct page *page) |
359 | { | |
360 | struct fscrypt_ctx *ctx; | |
361 | ||
362 | ctx = (struct fscrypt_ctx *)page_private(page); | |
363 | set_page_private(page, (unsigned long)NULL); | |
364 | ClearPagePrivate(page); | |
365 | unlock_page(page); | |
366 | fscrypt_release_ctx(ctx); | |
367 | } | |
368 | EXPORT_SYMBOL(fscrypt_restore_control_page); | |
369 | ||
370 | static void fscrypt_destroy(void) | |
371 | { | |
372 | struct fscrypt_ctx *pos, *n; | |
373 | ||
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; | |
379 | } | |
380 | ||
381 | /** | |
382 | * fscrypt_initialize() - allocate major buffers for fs encryption. | |
f32d7ac2 | 383 | * @cop_flags: fscrypt operations flags |
0b81d077 JK |
384 | * |
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. | |
387 | * | |
388 | * Return: Zero on success, non-zero otherwise. | |
389 | */ | |
f32d7ac2 | 390 | int fscrypt_initialize(unsigned int cop_flags) |
0b81d077 JK |
391 | { |
392 | int i, res = -ENOMEM; | |
393 | ||
a0b3bc85 EB |
394 | /* No need to allocate a bounce page pool if this FS won't use it. */ |
395 | if (cop_flags & FS_CFLG_OWN_PAGES) | |
0b81d077 JK |
396 | return 0; |
397 | ||
398 | mutex_lock(&fscrypt_init_mutex); | |
399 | if (fscrypt_bounce_page_pool) | |
400 | goto already_initialized; | |
401 | ||
402 | for (i = 0; i < num_prealloc_crypto_ctxs; i++) { | |
403 | struct fscrypt_ctx *ctx; | |
404 | ||
405 | ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS); | |
406 | if (!ctx) | |
407 | goto fail; | |
408 | list_add(&ctx->free_list, &fscrypt_free_ctxs); | |
409 | } | |
410 | ||
411 | fscrypt_bounce_page_pool = | |
412 | mempool_create_page_pool(num_prealloc_crypto_pages, 0); | |
413 | if (!fscrypt_bounce_page_pool) | |
414 | goto fail; | |
415 | ||
416 | already_initialized: | |
417 | mutex_unlock(&fscrypt_init_mutex); | |
418 | return 0; | |
419 | fail: | |
420 | fscrypt_destroy(); | |
421 | mutex_unlock(&fscrypt_init_mutex); | |
422 | return res; | |
423 | } | |
0b81d077 JK |
424 | |
425 | /** | |
426 | * fscrypt_init() - Set up for fs encryption. | |
427 | */ | |
428 | static int __init fscrypt_init(void) | |
429 | { | |
430 | fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue", | |
431 | WQ_HIGHPRI, 0); | |
432 | if (!fscrypt_read_workqueue) | |
433 | goto fail; | |
434 | ||
435 | fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT); | |
436 | if (!fscrypt_ctx_cachep) | |
437 | goto fail_free_queue; | |
438 | ||
439 | fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT); | |
440 | if (!fscrypt_info_cachep) | |
441 | goto fail_free_ctx; | |
442 | ||
443 | return 0; | |
444 | ||
445 | fail_free_ctx: | |
446 | kmem_cache_destroy(fscrypt_ctx_cachep); | |
447 | fail_free_queue: | |
448 | destroy_workqueue(fscrypt_read_workqueue); | |
449 | fail: | |
450 | return -ENOMEM; | |
451 | } | |
452 | module_init(fscrypt_init) | |
453 | ||
454 | /** | |
455 | * fscrypt_exit() - Shutdown the fs encryption system | |
456 | */ | |
457 | static void __exit fscrypt_exit(void) | |
458 | { | |
459 | fscrypt_destroy(); | |
460 | ||
461 | if (fscrypt_read_workqueue) | |
462 | destroy_workqueue(fscrypt_read_workqueue); | |
463 | kmem_cache_destroy(fscrypt_ctx_cachep); | |
464 | kmem_cache_destroy(fscrypt_info_cachep); | |
b7e7cf7a DW |
465 | |
466 | fscrypt_essiv_cleanup(); | |
0b81d077 JK |
467 | } |
468 | module_exit(fscrypt_exit); | |
469 | ||
470 | MODULE_LICENSE("GPL"); |