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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 <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
33static unsigned int num_prealloc_crypto_pages = 32;
34
35module_param(num_prealloc_crypto_pages, uint, 0444);
36MODULE_PARM_DESC(num_prealloc_crypto_pages,
37 "Number of crypto pages to preallocate");
38
39static mempool_t *fscrypt_bounce_page_pool = NULL;
40
41static DEFINE_MUTEX(fscrypt_init_mutex);
42
43struct kmem_cache *fscrypt_inode_info_cachep;
44
45static struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
46{
47 if (WARN_ON_ONCE(!fscrypt_bounce_page_pool)) {
48 /*
49 * Oops, the filesystem called a function that uses the bounce
50 * page pool, but it didn't set needs_bounce_pages.
51 */
52 return NULL;
53 }
54 return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
55}
56
57/**
58 * fscrypt_free_bounce_page() - free a ciphertext bounce page
59 * @bounce_page: the bounce page to free, or NULL
60 *
61 * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks().
62 */
63void fscrypt_free_bounce_page(struct page *bounce_page)
64{
65 if (!bounce_page)
66 return;
67 set_page_private(bounce_page, (unsigned long)NULL);
68 ClearPagePrivate(bounce_page);
69 mempool_free(bounce_page, fscrypt_bounce_page_pool);
70}
71EXPORT_SYMBOL(fscrypt_free_bounce_page);
72
73/*
74 * Generate the IV for the given data unit index within the given file.
75 * For filenames encryption, index == 0.
76 *
77 * Keep this in sync with fscrypt_limit_io_blocks(). fscrypt_limit_io_blocks()
78 * needs to know about any IV generation methods where the low bits of IV don't
79 * simply contain the data unit index (e.g., IV_INO_LBLK_32).
80 */
81void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index,
82 const struct fscrypt_inode_info *ci)
83{
84 u8 flags = fscrypt_policy_flags(&ci->ci_policy);
85
86 memset(iv, 0, sizeof(*iv));
87
88 if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
89 WARN_ON_ONCE(index > U32_MAX);
90 WARN_ON_ONCE(ci->ci_inode->i_ino > U32_MAX);
91 index |= (u64)ci->ci_inode->i_ino << 32;
92 } else if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
93 WARN_ON_ONCE(index > U32_MAX);
94 index = (u32)(ci->ci_hashed_ino + index);
95 } else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
96 memcpy(iv->nonce, ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE);
97 }
98 iv->index = cpu_to_le64(index);
99}
100
101typedef enum {
102 FS_DECRYPT = 0,
103 FS_ENCRYPT,
104} fscrypt_direction_t;
105
106/* Encrypt or decrypt a single "data unit" of file contents. */
107static int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci,
108 fscrypt_direction_t rw, u64 index,
109 struct page *src_page,
110 struct page *dest_page, unsigned int len,
111 unsigned int offs)
112{
113 struct crypto_sync_skcipher *tfm;
114 union fscrypt_iv iv;
115 struct scatterlist dst, src;
116 int err;
117
118 if (WARN_ON_ONCE(ci == NULL)) /* File hasn't been opened yet? */
119 return -ENOKEY;
120 tfm = ci->ci_enc_key.tfm;
121 if (WARN_ON_ONCE(tfm == NULL)) /* Called on block-based filesystem? */
122 return -ENOKEY;
123
124 if (WARN_ON_ONCE(len <= 0))
125 return -EINVAL;
126 if (WARN_ON_ONCE(len % FSCRYPT_CONTENTS_ALIGNMENT != 0))
127 return -EINVAL;
128
129 fscrypt_generate_iv(&iv, index, ci);
130
131 {
132 SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm);
133 skcipher_request_set_callback(req,
134 CRYPTO_TFM_REQ_MAY_BACKLOG |
135 CRYPTO_TFM_REQ_MAY_SLEEP,
136 NULL, NULL);
137 sg_init_table(&dst, 1);
138 sg_set_page(&dst, dest_page, len, offs);
139 sg_init_table(&src, 1);
140 sg_set_page(&src, src_page, len, offs);
141 skcipher_request_set_crypt(req, &src, &dst, len, &iv);
142 if (rw == FS_DECRYPT)
143 err = crypto_skcipher_decrypt(req);
144 else
145 err = crypto_skcipher_encrypt(req);
146 }
147 if (err)
148 fscrypt_err(ci->ci_inode,
149 "%scryption failed for data unit %llu: %d",
150 (rw == FS_DECRYPT ? "De" : "En"), index, err);
151 return err;
152}
153
154/**
155 * fscrypt_encrypt_pagecache_blocks() - Encrypt data from a pagecache folio
156 * @folio: the locked pagecache folio containing the data to encrypt
157 * @len: size of the data to encrypt, in bytes
158 * @offs: offset within @page of the data to encrypt, in bytes
159 * @gfp_flags: memory allocation flags; see details below
160 *
161 * This allocates a new bounce page and encrypts the given data into it. The
162 * length and offset of the data must be aligned to the file's crypto data unit
163 * size. Alignment to the filesystem block size fulfills this requirement, as
164 * the filesystem block size is always a multiple of the data unit size.
165 *
166 * In the bounce page, the ciphertext data will be located at the same offset at
167 * which the plaintext data was located in the source page. Any other parts of
168 * the bounce page will be left uninitialized.
169 *
170 * This is for use by the ->writepages() method of non-block-based filesystems.
171 *
172 * The bounce page allocation is mempool-backed, so it will always succeed when
173 * @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS. However,
174 * only the first page of each bio can be allocated this way. To prevent
175 * deadlocks, for any additional pages a mask like GFP_NOWAIT must be used.
176 *
177 * Return: the new encrypted bounce page on success; an ERR_PTR() on failure
178 */
179struct page *fscrypt_encrypt_pagecache_blocks(struct folio *folio,
180 size_t len, size_t offs, gfp_t gfp_flags)
181{
182 const struct inode *inode = folio->mapping->host;
183 const struct fscrypt_inode_info *ci = fscrypt_get_inode_info_raw(inode);
184 unsigned int du_bits;
185 unsigned int du_size;
186 struct page *ciphertext_page;
187 u64 index;
188 unsigned int i;
189 int err;
190
191 if (WARN_ON_ONCE(ci == NULL)) /* File hasn't been opened yet? */
192 return ERR_PTR(-ENOKEY);
193
194 du_bits = ci->ci_data_unit_bits;
195 du_size = 1U << du_bits;
196 index = (folio_pos(folio) + offs) >> du_bits;
197
198 VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
199 if (WARN_ON_ONCE(!folio_test_locked(folio)))
200 return ERR_PTR(-EINVAL);
201
202 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size)))
203 return ERR_PTR(-EINVAL);
204
205 ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
206 if (!ciphertext_page)
207 return ERR_PTR(-ENOMEM);
208
209 for (i = offs; i < offs + len; i += du_size, index++) {
210 err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, index,
211 &folio->page, ciphertext_page,
212 du_size, i);
213 if (err) {
214 fscrypt_free_bounce_page(ciphertext_page);
215 return ERR_PTR(err);
216 }
217 }
218 SetPagePrivate(ciphertext_page);
219 set_page_private(ciphertext_page, (unsigned long)folio);
220 return ciphertext_page;
221}
222EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);
223
224/**
225 * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
226 * @inode: The inode to which this block belongs
227 * @page: The page containing the block to encrypt
228 * @len: Size of block to encrypt. This must be a multiple of
229 * FSCRYPT_CONTENTS_ALIGNMENT.
230 * @offs: Byte offset within @page at which the block to encrypt begins
231 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
232 * number of the block within the file
233 *
234 * Encrypt a possibly-compressed filesystem block that is located in an
235 * arbitrary page, not necessarily in the original pagecache page. The @inode
236 * and @lblk_num must be specified, as they can't be determined from @page.
237 *
238 * This function only supports non-block-based filesystems that don't support
239 * sub-block data units (as indicated by the fscrypt_operations fields).
240 *
241 * Return: 0 on success; -errno on failure
242 */
243int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
244 unsigned int len, unsigned int offs,
245 u64 lblk_num)
246{
247 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units))
248 return -EOPNOTSUPP;
249 return fscrypt_crypt_data_unit(fscrypt_get_inode_info_raw(inode),
250 FS_ENCRYPT, lblk_num, page, page, len,
251 offs);
252}
253EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);
254
255/**
256 * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
257 * @inode: The inode to which this block belongs
258 * @page: The page containing the block to decrypt
259 * @len: Size of block to decrypt. This must be a multiple of
260 * FSCRYPT_CONTENTS_ALIGNMENT.
261 * @offs: Byte offset within @page at which the block to decrypt begins
262 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
263 * number of the block within the file
264 *
265 * Decrypt a possibly-compressed filesystem block that is located in an
266 * arbitrary page, not necessarily in the original pagecache page. The @inode
267 * and @lblk_num must be specified, as they can't be determined from @page.
268 *
269 * This function only supports non-block-based filesystems that don't support
270 * sub-block data units (as indicated by the fscrypt_operations fields).
271 *
272 * Return: 0 on success; -errno on failure
273 */
274int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
275 unsigned int len, unsigned int offs,
276 u64 lblk_num)
277{
278 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units))
279 return -EOPNOTSUPP;
280 return fscrypt_crypt_data_unit(fscrypt_get_inode_info_raw(inode),
281 FS_DECRYPT, lblk_num, page, page, len,
282 offs);
283}
284EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);
285
286/**
287 * fscrypt_initialize() - allocate major buffers for fs encryption.
288 * @sb: the filesystem superblock
289 *
290 * We only call this when we start accessing encrypted files, since it
291 * results in memory getting allocated that wouldn't otherwise be used.
292 *
293 * Return: 0 on success; -errno on failure
294 */
295int fscrypt_initialize(struct super_block *sb)
296{
297 mempool_t *pool;
298
299 /* pairs with smp_store_release() below */
300 if (smp_load_acquire(&fscrypt_bounce_page_pool))
301 return 0;
302
303 /* No need to allocate a bounce page pool if this FS won't use it. */
304 if (!sb->s_cop->needs_bounce_pages)
305 return 0;
306
307 guard(mutex)(&fscrypt_init_mutex);
308 if (fscrypt_bounce_page_pool)
309 return 0;
310
311 pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0);
312 if (!pool)
313 return -ENOMEM;
314 /* pairs with smp_load_acquire() above */
315 smp_store_release(&fscrypt_bounce_page_pool, pool);
316 return 0;
317}
318
319void fscrypt_msg(const struct inode *inode, const char *level,
320 const char *fmt, ...)
321{
322 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
323 DEFAULT_RATELIMIT_BURST);
324 struct va_format vaf;
325 va_list args;
326
327 if (!__ratelimit(&rs))
328 return;
329
330 va_start(args, fmt);
331 vaf.fmt = fmt;
332 vaf.va = &args;
333 if (inode && inode->i_ino)
334 printk("%sfscrypt (%s, inode %llu): %pV\n",
335 level, inode->i_sb->s_id, inode->i_ino, &vaf);
336 else if (inode)
337 printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf);
338 else
339 printk("%sfscrypt: %pV\n", level, &vaf);
340 va_end(args);
341}
342
343static int __init fscrypt_init(void)
344{
345 fscrypt_inode_info_cachep = KMEM_CACHE(fscrypt_inode_info,
346 SLAB_RECLAIM_ACCOUNT |
347 SLAB_PANIC);
348 fscrypt_init_keyring();
349 return 0;
350}
351late_initcall(fscrypt_init)