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