summaryrefslogtreecommitdiff
path: root/fs/crypto/crypto.c
blob: 6a837e4b80dcb3a052508d7e64bca409956236d1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
// SPDX-License-Identifier: GPL-2.0-only
/*
 * This contains encryption functions for per-file encryption.
 *
 * Copyright (C) 2015, Google, Inc.
 * Copyright (C) 2015, Motorola Mobility
 *
 * Written by Michael Halcrow, 2014.
 *
 * Filename encryption additions
 *	Uday Savagaonkar, 2014
 * Encryption policy handling additions
 *	Ildar Muslukhov, 2014
 * Add fscrypt_pullback_bio_page()
 *	Jaegeuk Kim, 2015.
 *
 * This has not yet undergone a rigorous security audit.
 *
 * The usage of AES-XTS should conform to recommendations in NIST
 * Special Publication 800-38E and IEEE P1619/D16.
 */

#include <linux/pagemap.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/ratelimit.h>
#include <crypto/skcipher.h>
#include "fscrypt_private.h"

static unsigned int num_prealloc_crypto_pages = 32;

module_param(num_prealloc_crypto_pages, uint, 0444);
MODULE_PARM_DESC(num_prealloc_crypto_pages,
		"Number of crypto pages to preallocate");

static mempool_t *fscrypt_bounce_page_pool = NULL;

static struct workqueue_struct *fscrypt_read_workqueue;
static DEFINE_MUTEX(fscrypt_init_mutex);

struct kmem_cache *fscrypt_info_cachep;

void fscrypt_enqueue_decrypt_work(struct work_struct *work)
{
	queue_work(fscrypt_read_workqueue, work);
}
EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);

struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
{
	return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
}

/**
 * fscrypt_free_bounce_page() - free a ciphertext bounce page
 * @bounce_page: the bounce page to free, or NULL
 *
 * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(),
 * or by fscrypt_alloc_bounce_page() directly.
 */
void fscrypt_free_bounce_page(struct page *bounce_page)
{
	if (!bounce_page)
		return;
	set_page_private(bounce_page, (unsigned long)NULL);
	ClearPagePrivate(bounce_page);
	mempool_free(bounce_page, fscrypt_bounce_page_pool);
}
EXPORT_SYMBOL(fscrypt_free_bounce_page);

/*
 * Generate the IV for the given logical block number within the given file.
 * For filenames encryption, lblk_num == 0.
 *
 * Keep this in sync with fscrypt_limit_io_blocks().  fscrypt_limit_io_blocks()
 * needs to know about any IV generation methods where the low bits of IV don't
 * simply contain the lblk_num (e.g., IV_INO_LBLK_32).
 */
void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
			 const struct fscrypt_info *ci)
{
	u8 flags = fscrypt_policy_flags(&ci->ci_policy);

	memset(iv, 0, ci->ci_mode->ivsize);

	if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
		WARN_ON_ONCE(lblk_num > U32_MAX);
		WARN_ON_ONCE(ci->ci_inode->i_ino > U32_MAX);
		lblk_num |= (u64)ci->ci_inode->i_ino << 32;
	} else if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
		WARN_ON_ONCE(lblk_num > U32_MAX);
		lblk_num = (u32)(ci->ci_hashed_ino + lblk_num);
	} else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
		memcpy(iv->nonce, ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE);
	}
	iv->lblk_num = cpu_to_le64(lblk_num);
}

/* Encrypt or decrypt a single filesystem block of file contents */
int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
			u64 lblk_num, struct page *src_page,
			struct page *dest_page, unsigned int len,
			unsigned int offs, gfp_t gfp_flags)
{
	union fscrypt_iv iv;
	struct skcipher_request *req = NULL;
	DECLARE_CRYPTO_WAIT(wait);
	struct scatterlist dst, src;
	struct fscrypt_info *ci = inode->i_crypt_info;
	struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
	int res = 0;

	if (WARN_ON_ONCE(len <= 0))
		return -EINVAL;
	if (WARN_ON_ONCE(len % FSCRYPT_CONTENTS_ALIGNMENT != 0))
		return -EINVAL;

	fscrypt_generate_iv(&iv, lblk_num, ci);

	req = skcipher_request_alloc(tfm, gfp_flags);
	if (!req)
		return -ENOMEM;

	skcipher_request_set_callback(
		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
		crypto_req_done, &wait);

	sg_init_table(&dst, 1);
	sg_set_page(&dst, dest_page, len, offs);
	sg_init_table(&src, 1);
	sg_set_page(&src, src_page, len, offs);
	skcipher_request_set_crypt(req, &src, &dst, len, &iv);
	if (rw == FS_DECRYPT)
		res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
	else
		res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
	skcipher_request_free(req);
	if (res) {
		fscrypt_err(inode, "%scryption failed for block %llu: %d",
			    (rw == FS_DECRYPT ? "De" : "En"), lblk_num, res);
		return res;
	}
	return 0;
}

/**
 * fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a
 *					pagecache page
 * @page:      The locked pagecache page containing the block(s) to encrypt
 * @len:       Total size of the block(s) to encrypt.  Must be a nonzero
 *		multiple of the filesystem's block size.
 * @offs:      Byte offset within @page of the first block to encrypt.  Must be
 *		a multiple of the filesystem's block size.
 * @gfp_flags: Memory allocation flags.  See details below.
 *
 * A new bounce page is allocated, and the specified block(s) are encrypted into
 * it.  In the bounce page, the ciphertext block(s) will be located at the same
 * offsets at which the plaintext block(s) were located in the source page; any
 * other parts of the bounce page will be left uninitialized.  However, normally
 * blocksize == PAGE_SIZE and the whole page is encrypted at once.
 *
 * This is for use by the filesystem's ->writepages() method.
 *
 * The bounce page allocation is mempool-backed, so it will always succeed when
 * @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS.  However,
 * only the first page of each bio can be allocated this way.  To prevent
 * deadlocks, for any additional pages a mask like GFP_NOWAIT must be used.
 *
 * Return: the new encrypted bounce page on success; an ERR_PTR() on failure
 */
struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
					      unsigned int len,
					      unsigned int offs,
					      gfp_t gfp_flags)

{
	const struct inode *inode = page->mapping->host;
	const unsigned int blockbits = inode->i_blkbits;
	const unsigned int blocksize = 1 << blockbits;
	struct page *ciphertext_page;
	u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
		       (offs >> blockbits);
	unsigned int i;
	int err;

	if (WARN_ON_ONCE(!PageLocked(page)))
		return ERR_PTR(-EINVAL);

	if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
		return ERR_PTR(-EINVAL);

	ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
	if (!ciphertext_page)
		return ERR_PTR(-ENOMEM);

	for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
		err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num,
					  page, ciphertext_page,
					  blocksize, i, gfp_flags);
		if (err) {
			fscrypt_free_bounce_page(ciphertext_page);
			return ERR_PTR(err);
		}
	}
	SetPagePrivate(ciphertext_page);
	set_page_private(ciphertext_page, (unsigned long)page);
	return ciphertext_page;
}
EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);

/**
 * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
 * @inode:     The inode to which this block belongs
 * @page:      The page containing the block to encrypt
 * @len:       Size of block to encrypt.  This must be a multiple of
 *		FSCRYPT_CONTENTS_ALIGNMENT.
 * @offs:      Byte offset within @page at which the block to encrypt begins
 * @lblk_num:  Filesystem logical block number of the block, i.e. the 0-based
 *		number of the block within the file
 * @gfp_flags: Memory allocation flags
 *
 * Encrypt a possibly-compressed filesystem block that is located in an
 * arbitrary page, not necessarily in the original pagecache page.  The @inode
 * and @lblk_num must be specified, as they can't be determined from @page.
 *
 * Return: 0 on success; -errno on failure
 */
int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
				  unsigned int len, unsigned int offs,
				  u64 lblk_num, gfp_t gfp_flags)
{
	return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page,
				   len, offs, gfp_flags);
}
EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);

/**
 * fscrypt_decrypt_pagecache_blocks() - Decrypt filesystem blocks in a
 *					pagecache folio
 * @folio:     The locked pagecache folio containing the block(s) to decrypt
 * @len:       Total size of the block(s) to decrypt.  Must be a nonzero
 *		multiple of the filesystem's block size.
 * @offs:      Byte offset within @folio of the first block to decrypt.  Must be
 *		a multiple of the filesystem's block size.
 *
 * The specified block(s) are decrypted in-place within the pagecache folio,
 * which must still be locked and not uptodate.
 *
 * This is for use by the filesystem's ->readahead() method.
 *
 * Return: 0 on success; -errno on failure
 */
int fscrypt_decrypt_pagecache_blocks(struct folio *folio, size_t len,
				     size_t offs)
{
	const struct inode *inode = folio->mapping->host;
	const unsigned int blockbits = inode->i_blkbits;
	const unsigned int blocksize = 1 << blockbits;
	u64 lblk_num = ((u64)folio->index << (PAGE_SHIFT - blockbits)) +
		       (offs >> blockbits);
	size_t i;
	int err;

	if (WARN_ON_ONCE(!folio_test_locked(folio)))
		return -EINVAL;

	if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
		return -EINVAL;

	for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
		struct page *page = folio_page(folio, i >> PAGE_SHIFT);

		err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page,
					  page, blocksize, i & ~PAGE_MASK,
					  GFP_NOFS);
		if (err)
			return err;
	}
	return 0;
}
EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);

/**
 * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
 * @inode:     The inode to which this block belongs
 * @page:      The page containing the block to decrypt
 * @len:       Size of block to decrypt.  This must be a multiple of
 *		FSCRYPT_CONTENTS_ALIGNMENT.
 * @offs:      Byte offset within @page at which the block to decrypt begins
 * @lblk_num:  Filesystem logical block number of the block, i.e. the 0-based
 *		number of the block within the file
 *
 * Decrypt a possibly-compressed filesystem block that is located in an
 * arbitrary page, not necessarily in the original pagecache page.  The @inode
 * and @lblk_num must be specified, as they can't be determined from @page.
 *
 * Return: 0 on success; -errno on failure
 */
int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
				  unsigned int len, unsigned int offs,
				  u64 lblk_num)
{
	return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page,
				   len, offs, GFP_NOFS);
}
EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);

/**
 * fscrypt_initialize() - allocate major buffers for fs encryption.
 * @sb: the filesystem superblock
 *
 * We only call this when we start accessing encrypted files, since it
 * results in memory getting allocated that wouldn't otherwise be used.
 *
 * Return: 0 on success; -errno on failure
 */
int fscrypt_initialize(struct super_block *sb)
{
	int err = 0;
	mempool_t *pool;

	/* pairs with smp_store_release() below */
	if (likely(smp_load_acquire(&fscrypt_bounce_page_pool)))
		return 0;

	/* No need to allocate a bounce page pool if this FS won't use it. */
	if (sb->s_cop->flags & FS_CFLG_OWN_PAGES)
		return 0;

	mutex_lock(&fscrypt_init_mutex);
	if (fscrypt_bounce_page_pool)
		goto out_unlock;

	err = -ENOMEM;
	pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0);
	if (!pool)
		goto out_unlock;
	/* pairs with smp_load_acquire() above */
	smp_store_release(&fscrypt_bounce_page_pool, pool);
	err = 0;
out_unlock:
	mutex_unlock(&fscrypt_init_mutex);
	return err;
}

void fscrypt_msg(const struct inode *inode, const char *level,
		 const char *fmt, ...)
{
	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
				      DEFAULT_RATELIMIT_BURST);
	struct va_format vaf;
	va_list args;

	if (!__ratelimit(&rs))
		return;

	va_start(args, fmt);
	vaf.fmt = fmt;
	vaf.va = &args;
	if (inode && inode->i_ino)
		printk("%sfscrypt (%s, inode %lu): %pV\n",
		       level, inode->i_sb->s_id, inode->i_ino, &vaf);
	else if (inode)
		printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf);
	else
		printk("%sfscrypt: %pV\n", level, &vaf);
	va_end(args);
}

/**
 * fscrypt_init() - Set up for fs encryption.
 *
 * Return: 0 on success; -errno on failure
 */
static int __init fscrypt_init(void)
{
	int err = -ENOMEM;

	/*
	 * Use an unbound workqueue to allow bios to be decrypted in parallel
	 * even when they happen to complete on the same CPU.  This sacrifices
	 * locality, but it's worthwhile since decryption is CPU-intensive.
	 *
	 * Also use a high-priority workqueue to prioritize decryption work,
	 * which blocks reads from completing, over regular application tasks.
	 */
	fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
						 WQ_UNBOUND | WQ_HIGHPRI,
						 num_online_cpus());
	if (!fscrypt_read_workqueue)
		goto fail;

	fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
	if (!fscrypt_info_cachep)
		goto fail_free_queue;

	err = fscrypt_init_keyring();
	if (err)
		goto fail_free_info;

	return 0;

fail_free_info:
	kmem_cache_destroy(fscrypt_info_cachep);
fail_free_queue:
	destroy_workqueue(fscrypt_read_workqueue);
fail:
	return err;
}
late_initcall(fscrypt_init)