1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * This contains encryption functions for per-file encryption.
4 *
5 * Copyright (C) 2015, Google, Inc.
6 * Copyright (C) 2015, Motorola Mobility
7 *
8 * Written by Michael Halcrow, 2014.
9 *
10 * Filename encryption additions
11 * Uday Savagaonkar, 2014
12 * Encryption policy handling additions
13 * Ildar Muslukhov, 2014
14 * Add fscrypt_pullback_bio_page()
15 * Jaegeuk Kim, 2015.
16 *
17 * This has not yet undergone a rigorous security audit.
18 *
19 * The usage of AES-XTS should conform to recommendations in NIST
20 * Special Publication 800-38E and IEEE P1619/D16.
21 */
22
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 <crypto/skcipher.h>
29 #include "fscrypt_private.h"
30
31 static unsigned int num_prealloc_crypto_pages = 32;
32
33 module_param(num_prealloc_crypto_pages, uint, 0444);
34 MODULE_PARM_DESC(num_prealloc_crypto_pages,
35 "Number of crypto pages to preallocate");
36
37 static mempool_t *fscrypt_bounce_page_pool = NULL;
38
39 static struct workqueue_struct *fscrypt_read_workqueue;
40 static DEFINE_MUTEX(fscrypt_init_mutex);
41
42 struct kmem_cache *fscrypt_inode_info_cachep;
43
44 void fscrypt_enqueue_decrypt_work(struct work_struct *work)
45 {
46 queue_work(fscrypt_read_workqueue, work);
47 }
48 EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);
49
50 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
51 {
52 if (WARN_ON_ONCE(!fscrypt_bounce_page_pool)) {
53 /*
54 * Oops, the filesystem called a function that uses the bounce
55 * page pool, but it didn't set needs_bounce_pages.
56 */
57 return NULL;
58 }
59 return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
60 }
61
62 /**
63 * fscrypt_free_bounce_page() - free a ciphertext bounce page
64 * @bounce_page: the bounce page to free, or NULL
65 *
66 * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(),
67 * or by fscrypt_alloc_bounce_page() directly.
68 */
69 void fscrypt_free_bounce_page(struct page *bounce_page)
70 {
71 if (!bounce_page)
72 return;
73 set_page_private(bounce_page, (unsigned long)NULL);
74 ClearPagePrivate(bounce_page);
75 mempool_free(bounce_page, fscrypt_bounce_page_pool);
76 }
77 EXPORT_SYMBOL(fscrypt_free_bounce_page);
78
79 /*
80 * Generate the IV for the given data unit index within the given file.
81 * For filenames encryption, index == 0.
82 *
83 * Keep this in sync with fscrypt_limit_io_blocks(). fscrypt_limit_io_blocks()
84 * needs to know about any IV generation methods where the low bits of IV don't
85 * simply contain the data unit index (e.g., IV_INO_LBLK_32).
86 */
87 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index,
88 const struct fscrypt_inode_info *ci)
89 {
90 u8 flags = fscrypt_policy_flags(&ci->ci_policy);
91
92 memset(iv, 0, ci->ci_mode->ivsize);
93
94 if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
95 WARN_ON_ONCE(index > U32_MAX);
96 WARN_ON_ONCE(ci->ci_inode->i_ino > U32_MAX);
97 index |= (u64)ci->ci_inode->i_ino << 32;
98 } else if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
99 WARN_ON_ONCE(index > U32_MAX);
100 index = (u32)(ci->ci_hashed_ino + index);
101 } else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
102 memcpy(iv->nonce, ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE);
103 }
104 iv->index = cpu_to_le64(index);
105 }
106
107 /* Encrypt or decrypt a single "data unit" of file contents. */
108 int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci,
109 fscrypt_direction_t rw, u64 index,
110 struct page *src_page, struct page *dest_page,
111 unsigned int len, unsigned int offs,
112 gfp_t gfp_flags)
113 {
114 union fscrypt_iv iv;
115 struct skcipher_request *req = NULL;
116 DECLARE_CRYPTO_WAIT(wait);
117 struct scatterlist dst, src;
118 struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
119 int res = 0;
120
121 if (WARN_ON_ONCE(len <= 0))
122 return -EINVAL;
123 if (WARN_ON_ONCE(len % FSCRYPT_CONTENTS_ALIGNMENT != 0))
124 return -EINVAL;
125
126 fscrypt_generate_iv(&iv, index, ci);
127
128 req = skcipher_request_alloc(tfm, gfp_flags);
129 if (!req)
130 return -ENOMEM;
131
132 skcipher_request_set_callback(
133 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
134 crypto_req_done, &wait);
135
136 sg_init_table(&dst, 1);
137 sg_set_page(&dst, dest_page, len, offs);
138 sg_init_table(&src, 1);
139 sg_set_page(&src, src_page, len, offs);
140 skcipher_request_set_crypt(req, &src, &dst, len, &iv);
141 if (rw == FS_DECRYPT)
142 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
143 else
144 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
145 skcipher_request_free(req);
146 if (res) {
147 fscrypt_err(ci->ci_inode,
148 "%scryption failed for data unit %llu: %d",
149 (rw == FS_DECRYPT ? "De" : "En"), index, res);
150 return res;
151 }
152 return 0;
153 }
154
155 /**
156 * fscrypt_encrypt_pagecache_blocks() - Encrypt data from a pagecache page
157 * @page: the locked pagecache page containing the data to encrypt
158 * @len: size of the data to encrypt, in bytes
159 * @offs: offset within @page of the data to encrypt, in bytes
160 * @gfp_flags: memory allocation flags; see details below
161 *
162 * This allocates a new bounce page and encrypts the given data into it. The
163 * length and offset of the data must be aligned to the file's crypto data unit
164 * size. Alignment to the filesystem block size fulfills this requirement, as
165 * the filesystem block size is always a multiple of the data unit size.
166 *
167 * In the bounce page, the ciphertext data will be located at the same offset at
168 * which the plaintext data was located in the source page. Any other parts of
169 * the bounce page will be left uninitialized.
170 *
171 * This is for use by the filesystem's ->writepages() method.
172 *
173 * The bounce page allocation is mempool-backed, so it will always succeed when
174 * @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS. However,
175 * only the first page of each bio can be allocated this way. To prevent
176 * deadlocks, for any additional pages a mask like GFP_NOWAIT must be used.
177 *
178 * Return: the new encrypted bounce page on success; an ERR_PTR() on failure
179 */
180 struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
181 unsigned int len,
182 unsigned int offs,
183 gfp_t gfp_flags)
184
185 {
186 const struct inode *inode = page->mapping->host;
187 const struct fscrypt_inode_info *ci = inode->i_crypt_info;
188 const unsigned int du_bits = ci->ci_data_unit_bits;
189 const unsigned int du_size = 1U << du_bits;
190 struct page *ciphertext_page;
191 u64 index = ((u64)page->index << (PAGE_SHIFT - du_bits)) +
192 (offs >> du_bits);
193 unsigned int i;
194 int err;
195
196 if (WARN_ON_ONCE(!PageLocked(page)))
197 return ERR_PTR(-EINVAL);
198
199 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size)))
200 return ERR_PTR(-EINVAL);
201
202 ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
203 if (!ciphertext_page)
204 return ERR_PTR(-ENOMEM);
205
206 for (i = offs; i < offs + len; i += du_size, index++) {
207 err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, index,
208 page, ciphertext_page,
209 du_size, i, gfp_flags);
210 if (err) {
211 fscrypt_free_bounce_page(ciphertext_page);
212 return ERR_PTR(err);
213 }
214 }
215 SetPagePrivate(ciphertext_page);
216 set_page_private(ciphertext_page, (unsigned long)page);
217 return ciphertext_page;
218 }
219 EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);
220
221 /**
222 * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
223 * @inode: The inode to which this block belongs
224 * @page: The page containing the block to encrypt
225 * @len: Size of block to encrypt. This must be a multiple of
226 * FSCRYPT_CONTENTS_ALIGNMENT.
227 * @offs: Byte offset within @page at which the block to encrypt begins
228 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
229 * number of the block within the file
230 * @gfp_flags: Memory allocation flags
231 *
232 * Encrypt a possibly-compressed filesystem block that is located in an
233 * arbitrary page, not necessarily in the original pagecache page. The @inode
234 * and @lblk_num must be specified, as they can't be determined from @page.
235 *
236 * This is not compatible with fscrypt_operations::supports_subblock_data_units.
237 *
238 * Return: 0 on success; -errno on failure
239 */
240 int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
241 unsigned int len, unsigned int offs,
242 u64 lblk_num, gfp_t gfp_flags)
243 {
244 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units))
245 return -EOPNOTSUPP;
246 return fscrypt_crypt_data_unit(inode->i_crypt_info, FS_ENCRYPT,
247 lblk_num, page, page, len, offs,
248 gfp_flags);
249 }
250 EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);
251
252 /**
253 * fscrypt_decrypt_pagecache_blocks() - Decrypt data from a pagecache folio
254 * @folio: the pagecache folio containing the data to decrypt
255 * @len: size of the data to decrypt, in bytes
256 * @offs: offset within @folio of the data to decrypt, in bytes
257 *
258 * Decrypt data that has just been read from an encrypted file. The data must
259 * be located in a pagecache folio that is still locked and not yet uptodate.
260 * The length and offset of the data must be aligned to the file's crypto data
261 * unit size. Alignment to the filesystem block size fulfills this requirement,
262 * as the filesystem block size is always a multiple of the data unit size.
263 *
264 * Return: 0 on success; -errno on failure
265 */
266 int fscrypt_decrypt_pagecache_blocks(struct folio *folio, size_t len,
267 size_t offs)
268 {
269 const struct inode *inode = folio->mapping->host;
270 const struct fscrypt_inode_info *ci = inode->i_crypt_info;
271 const unsigned int du_bits = ci->ci_data_unit_bits;
272 const unsigned int du_size = 1U << du_bits;
273 u64 index = ((u64)folio->index << (PAGE_SHIFT - du_bits)) +
274 (offs >> du_bits);
275 size_t i;
276 int err;
277
278 if (WARN_ON_ONCE(!folio_test_locked(folio)))
279 return -EINVAL;
280
281 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size)))
282 return -EINVAL;
283
284 for (i = offs; i < offs + len; i += du_size, index++) {
285 struct page *page = folio_page(folio, i >> PAGE_SHIFT);
286
287 err = fscrypt_crypt_data_unit(ci, FS_DECRYPT, index, page,
288 page, du_size, i & ~PAGE_MASK,
289 GFP_NOFS);
290 if (err)
291 return err;
292 }
293 return 0;
294 }
295 EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);
296
297 /**
298 * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
299 * @inode: The inode to which this block belongs
300 * @page: The page containing the block to decrypt
301 * @len: Size of block to decrypt. This must be a multiple of
302 * FSCRYPT_CONTENTS_ALIGNMENT.
303 * @offs: Byte offset within @page at which the block to decrypt begins
304 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
305 * number of the block within the file
306 *
307 * Decrypt a possibly-compressed filesystem block that is located in an
308 * arbitrary page, not necessarily in the original pagecache page. The @inode
309 * and @lblk_num must be specified, as they can't be determined from @page.
310 *
311 * This is not compatible with fscrypt_operations::supports_subblock_data_units.
312 *
313 * Return: 0 on success; -errno on failure
314 */
315 int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
316 unsigned int len, unsigned int offs,
317 u64 lblk_num)
318 {
319 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units))
320 return -EOPNOTSUPP;
321 return fscrypt_crypt_data_unit(inode->i_crypt_info, FS_DECRYPT,
322 lblk_num, page, page, len, offs,
323 GFP_NOFS);
324 }
325 EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);
326
327 /**
328 * fscrypt_initialize() - allocate major buffers for fs encryption.
329 * @sb: the filesystem superblock
330 *
331 * We only call this when we start accessing encrypted files, since it
332 * results in memory getting allocated that wouldn't otherwise be used.
333 *
334 * Return: 0 on success; -errno on failure
335 */
336 int fscrypt_initialize(struct super_block *sb)
337 {
338 int err = 0;
339 mempool_t *pool;
340
341 /* pairs with smp_store_release() below */
342 if (likely(smp_load_acquire(&fscrypt_bounce_page_pool)))
343 return 0;
344
345 /* No need to allocate a bounce page pool if this FS won't use it. */
346 if (!sb->s_cop->needs_bounce_pages)
347 return 0;
348
349 mutex_lock(&fscrypt_init_mutex);
350 if (fscrypt_bounce_page_pool)
351 goto out_unlock;
352
353 err = -ENOMEM;
354 pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0);
355 if (!pool)
356 goto out_unlock;
357 /* pairs with smp_load_acquire() above */
358 smp_store_release(&fscrypt_bounce_page_pool, pool);
359 err = 0;
360 out_unlock:
361 mutex_unlock(&fscrypt_init_mutex);
362 return err;
363 }
364
365 void fscrypt_msg(const struct inode *inode, const char *level,
366 const char *fmt, ...)
367 {
368 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
369 DEFAULT_RATELIMIT_BURST);
370 struct va_format vaf;
371 va_list args;
372
373 if (!__ratelimit(&rs))
374 return;
375
376 va_start(args, fmt);
377 vaf.fmt = fmt;
378 vaf.va = &args;
379 if (inode && inode->i_ino)
380 printk("%sfscrypt (%s, inode %lu): %pV\n",
381 level, inode->i_sb->s_id, inode->i_ino, &vaf);
382 else if (inode)
383 printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf);
384 else
385 printk("%sfscrypt: %pV\n", level, &vaf);
386 va_end(args);
387 }
388
389 /**
390 * fscrypt_init() - Set up for fs encryption.
391 *
392 * Return: 0 on success; -errno on failure
393 */
394 static int __init fscrypt_init(void)
395 {
396 int err = -ENOMEM;
397
398 /*
399 * Use an unbound workqueue to allow bios to be decrypted in parallel
400 * even when they happen to complete on the same CPU. This sacrifices
401 * locality, but it's worthwhile since decryption is CPU-intensive.
402 *
403 * Also use a high-priority workqueue to prioritize decryption work,
404 * which blocks reads from completing, over regular application tasks.
405 */
406 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
407 WQ_UNBOUND | WQ_HIGHPRI,
408 num_online_cpus());
409 if (!fscrypt_read_workqueue)
410 goto fail;
411
412 fscrypt_inode_info_cachep = KMEM_CACHE(fscrypt_inode_info,
413 SLAB_RECLAIM_ACCOUNT);
414 if (!fscrypt_inode_info_cachep)
415 goto fail_free_queue;
416
417 err = fscrypt_init_keyring();
418 if (err)
419 goto fail_free_inode_info;
420
421 return 0;
422
423 fail_free_inode_info:
424 kmem_cache_destroy(fscrypt_inode_info_cachep);
425 fail_free_queue:
426 destroy_workqueue(fscrypt_read_workqueue);
427 fail:
428 return err;
429 }
430 late_initcall(fscrypt_init)
431
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