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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
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"
32
33static unsigned int num_prealloc_crypto_pages = 32;
34static unsigned int num_prealloc_crypto_ctxs = 128;
35
36module_param(num_prealloc_crypto_pages, uint, 0444);
37MODULE_PARM_DESC(num_prealloc_crypto_pages,
38 "Number of crypto pages to preallocate");
39module_param(num_prealloc_crypto_ctxs, uint, 0444);
40MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
41 "Number of crypto contexts to preallocate");
42
43static mempool_t *fscrypt_bounce_page_pool = NULL;
44
45static LIST_HEAD(fscrypt_free_ctxs);
46static DEFINE_SPINLOCK(fscrypt_ctx_lock);
47
48struct workqueue_struct *fscrypt_read_workqueue;
49static DEFINE_MUTEX(fscrypt_init_mutex);
50
51static struct kmem_cache *fscrypt_ctx_cachep;
52struct 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 */
63void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
64{
65 unsigned long flags;
66
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;
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}
80EXPORT_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
85 * @gfp_flags: The gfp flag for memory allocation
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 */
92struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode, gfp_t gfp_flags)
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) {
118 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
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 }
125 ctx->flags &= ~FS_CTX_HAS_BOUNCE_BUFFER_FL;
126 return ctx;
127}
128EXPORT_SYMBOL(fscrypt_get_ctx);
129
130int 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)
134{
135 struct {
136 __le64 index;
137 u8 padding[FS_IV_SIZE - sizeof(__le64)];
138 } iv;
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;
144 int res = 0;
145
146 BUG_ON(len == 0);
147
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
158 req = skcipher_request_alloc(tfm, gfp_flags);
159 if (!req) {
160 printk_ratelimited(KERN_ERR
161 "%s: crypto_request_alloc() failed\n",
162 __func__);
163 return -ENOMEM;
164 }
165
166 skcipher_request_set_callback(
167 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
168 crypto_req_done, &wait);
169
170 sg_init_table(&dst, 1);
171 sg_set_page(&dst, dest_page, len, offs);
172 sg_init_table(&src, 1);
173 sg_set_page(&src, src_page, len, offs);
174 skcipher_request_set_crypt(req, &src, &dst, len, &iv);
175 if (rw == FS_DECRYPT)
176 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
177 else
178 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
179 skcipher_request_free(req);
180 if (res) {
181 printk_ratelimited(KERN_ERR
182 "%s: crypto_skcipher_encrypt() returned %d\n",
183 __func__, res);
184 return res;
185 }
186 return 0;
187}
188
189struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
190 gfp_t gfp_flags)
191{
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;
197}
198
199/**
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
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
212 *
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.
216 *
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.
222 *
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
225 * encrypted.
226 *
227 * Return: A page with the encrypted content on success. Else, an
228 * error value or NULL.
229 */
230struct page *fscrypt_encrypt_page(const struct inode *inode,
231 struct page *page,
232 unsigned int len,
233 unsigned int offs,
234 u64 lblk_num, gfp_t gfp_flags)
235
236{
237 struct fscrypt_ctx *ctx;
238 struct page *ciphertext_page = page;
239 int err;
240
241 BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);
242
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,
247 gfp_flags);
248 if (err)
249 return ERR_PTR(err);
250
251 return ciphertext_page;
252 }
253
254 BUG_ON(!PageLocked(page));
255
256 ctx = fscrypt_get_ctx(inode, gfp_flags);
257 if (IS_ERR(ctx))
258 return (struct page *)ctx;
259
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))
263 goto errout;
264
265 ctx->w.control_page = page;
266 err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num,
267 page, ciphertext_page, len, offs,
268 gfp_flags);
269 if (err) {
270 ciphertext_page = ERR_PTR(err);
271 goto errout;
272 }
273 SetPagePrivate(ciphertext_page);
274 set_page_private(ciphertext_page, (unsigned long)ctx);
275 lock_page(ciphertext_page);
276 return ciphertext_page;
277
278errout:
279 fscrypt_release_ctx(ctx);
280 return ciphertext_page;
281}
282EXPORT_SYMBOL(fscrypt_encrypt_page);
283
284/**
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.
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 */
299int fscrypt_decrypt_page(const struct inode *inode, struct page *page,
300 unsigned int len, unsigned int offs, u64 lblk_num)
301{
302 if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES))
303 BUG_ON(!PageLocked(page));
304
305 return fscrypt_do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page,
306 len, offs, GFP_NOFS);
307}
308EXPORT_SYMBOL(fscrypt_decrypt_page);
309
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 */
315static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
316{
317 struct dentry *dir;
318 int dir_has_key, cached_with_key;
319
320 if (flags & LOOKUP_RCU)
321 return -ECHILD;
322
323 dir = dget_parent(dentry);
324 if (!IS_ENCRYPTED(d_inode(dir))) {
325 dput(dir);
326 return 0;
327 }
328
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);
333 dir_has_key = (d_inode(dir)->i_crypt_info != NULL);
334 dput(dir);
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
353const struct dentry_operations fscrypt_d_ops = {
354 .d_revalidate = fscrypt_d_revalidate,
355};
356EXPORT_SYMBOL(fscrypt_d_ops);
357
358void 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}
368EXPORT_SYMBOL(fscrypt_restore_control_page);
369
370static 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.
383 * @cop_flags: fscrypt operations flags
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 */
390int fscrypt_initialize(unsigned int cop_flags)
391{
392 int i, res = -ENOMEM;
393
394 /* No need to allocate a bounce page pool if this FS won't use it. */
395 if (cop_flags & FS_CFLG_OWN_PAGES)
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
416already_initialized:
417 mutex_unlock(&fscrypt_init_mutex);
418 return 0;
419fail:
420 fscrypt_destroy();
421 mutex_unlock(&fscrypt_init_mutex);
422 return res;
423}
424
425/**
426 * fscrypt_init() - Set up for fs encryption.
427 */
428static 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
445fail_free_ctx:
446 kmem_cache_destroy(fscrypt_ctx_cachep);
447fail_free_queue:
448 destroy_workqueue(fscrypt_read_workqueue);
449fail:
450 return -ENOMEM;
451}
452module_init(fscrypt_init)
453
454/**
455 * fscrypt_exit() - Shutdown the fs encryption system
456 */
457static 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);
465
466 fscrypt_essiv_cleanup();
467}
468module_exit(fscrypt_exit);
469
470MODULE_LICENSE("GPL");