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