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