crypto.c

  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 struct workqueue_struct *fscrypt_read_workqueue;
 42static DEFINE_MUTEX(fscrypt_init_mutex);
 43
 44struct kmem_cache *fscrypt_inode_info_cachep;
 45
 46void fscrypt_enqueue_decrypt_work(struct work_struct *work)
 47{
 48	queue_work(fscrypt_read_workqueue, work);
 49}
 50EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);
 51
 52struct 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 */
 71void 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}
 79EXPORT_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 */
 89void 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. */
110int 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 */
172struct 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 = fscrypt_get_inode_info_raw(inode);
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}
209EXPORT_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 */
229int 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(fscrypt_get_inode_info_raw(inode),
236				       FS_ENCRYPT, lblk_num, page, page, len,
237				       offs);
238}
239EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);
240
241/**
242 * fscrypt_decrypt_pagecache_blocks() - Decrypt data from a pagecache folio
243 * @folio: the pagecache folio containing the data to decrypt
244 * @len: size of the data to decrypt, in bytes
245 * @offs: offset within @folio of the data to decrypt, in bytes
246 *
247 * Decrypt data that has just been read from an encrypted file.  The data must
248 * be located in a pagecache folio that is still locked and not yet uptodate.
249 * The length and offset of the data must be aligned to the file's crypto data
250 * unit size.  Alignment to the filesystem block size fulfills this requirement,
251 * as the filesystem block size is always a multiple of the data unit size.
252 *
253 * Return: 0 on success; -errno on failure
254 */
255int fscrypt_decrypt_pagecache_blocks(struct folio *folio, size_t len,
256				     size_t offs)
257{
258	const struct inode *inode = folio->mapping->host;
259	const struct fscrypt_inode_info *ci = fscrypt_get_inode_info_raw(inode);
260	const unsigned int du_bits = ci->ci_data_unit_bits;
261	const unsigned int du_size = 1U << du_bits;
262	u64 index = ((u64)folio->index << (PAGE_SHIFT - du_bits)) +
263		    (offs >> du_bits);
264	size_t i;
265	int err;
266
267	if (WARN_ON_ONCE(!folio_test_locked(folio)))
268		return -EINVAL;
269
270	if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size)))
271		return -EINVAL;
272
273	for (i = offs; i < offs + len; i += du_size, index++) {
274		struct page *page = folio_page(folio, i >> PAGE_SHIFT);
275
276		err = fscrypt_crypt_data_unit(ci, FS_DECRYPT, index, page,
277					      page, du_size, i & ~PAGE_MASK);
278		if (err)
279			return err;
280	}
281	return 0;
282}
283EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);
284
285/**
286 * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
287 * @inode:     The inode to which this block belongs
288 * @page:      The page containing the block to decrypt
289 * @len:       Size of block to decrypt.  This must be a multiple of
290 *		FSCRYPT_CONTENTS_ALIGNMENT.
291 * @offs:      Byte offset within @page at which the block to decrypt begins
292 * @lblk_num:  Filesystem logical block number of the block, i.e. the 0-based
293 *		number of the block within the file
294 *
295 * Decrypt a possibly-compressed filesystem block that is located in an
296 * arbitrary page, not necessarily in the original pagecache page.  The @inode
297 * and @lblk_num must be specified, as they can't be determined from @page.
298 *
299 * This is not compatible with fscrypt_operations::supports_subblock_data_units.
300 *
301 * Return: 0 on success; -errno on failure
302 */
303int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
304				  unsigned int len, unsigned int offs,
305				  u64 lblk_num)
306{
307	if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units))
308		return -EOPNOTSUPP;
309	return fscrypt_crypt_data_unit(fscrypt_get_inode_info_raw(inode),
310				       FS_DECRYPT, lblk_num, page, page, len,
311				       offs);
312}
313EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);
314
315/**
316 * fscrypt_initialize() - allocate major buffers for fs encryption.
317 * @sb: the filesystem superblock
318 *
319 * We only call this when we start accessing encrypted files, since it
320 * results in memory getting allocated that wouldn't otherwise be used.
321 *
322 * Return: 0 on success; -errno on failure
323 */
324int fscrypt_initialize(struct super_block *sb)
325{
326	int err = 0;
327	mempool_t *pool;
328
329	/* pairs with smp_store_release() below */
330	if (likely(smp_load_acquire(&fscrypt_bounce_page_pool)))
331		return 0;
332
333	/* No need to allocate a bounce page pool if this FS won't use it. */
334	if (!sb->s_cop->needs_bounce_pages)
335		return 0;
336
337	mutex_lock(&fscrypt_init_mutex);
338	if (fscrypt_bounce_page_pool)
339		goto out_unlock;
340
341	err = -ENOMEM;
342	pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0);
343	if (!pool)
344		goto out_unlock;
345	/* pairs with smp_load_acquire() above */
346	smp_store_release(&fscrypt_bounce_page_pool, pool);
347	err = 0;
348out_unlock:
349	mutex_unlock(&fscrypt_init_mutex);
350	return err;
351}
352
353void fscrypt_msg(const struct inode *inode, const char *level,
354		 const char *fmt, ...)
355{
356	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
357				      DEFAULT_RATELIMIT_BURST);
358	struct va_format vaf;
359	va_list args;
360
361	if (!__ratelimit(&rs))
362		return;
363
364	va_start(args, fmt);
365	vaf.fmt = fmt;
366	vaf.va = &args;
367	if (inode && inode->i_ino)
368		printk("%sfscrypt (%s, inode %lu): %pV\n",
369		       level, inode->i_sb->s_id, inode->i_ino, &vaf);
370	else if (inode)
371		printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf);
372	else
373		printk("%sfscrypt: %pV\n", level, &vaf);
374	va_end(args);
375}
376
377/**
378 * fscrypt_init() - Set up for fs encryption.
379 *
380 * Return: 0 on success; -errno on failure
381 */
382static int __init fscrypt_init(void)
383{
384	int err = -ENOMEM;
385
386	/*
387	 * Use an unbound workqueue to allow bios to be decrypted in parallel
388	 * even when they happen to complete on the same CPU.  This sacrifices
389	 * locality, but it's worthwhile since decryption is CPU-intensive.
390	 *
391	 * Also use a high-priority workqueue to prioritize decryption work,
392	 * which blocks reads from completing, over regular application tasks.
393	 */
394	fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
395						 WQ_UNBOUND | WQ_HIGHPRI,
396						 num_online_cpus());
397	if (!fscrypt_read_workqueue)
398		goto fail;
399
400	fscrypt_inode_info_cachep = KMEM_CACHE(fscrypt_inode_info,
401					       SLAB_RECLAIM_ACCOUNT);
402	if (!fscrypt_inode_info_cachep)
403		goto fail_free_queue;
404
405	err = fscrypt_init_keyring();
406	if (err)
407		goto fail_free_inode_info;
408
409	return 0;
410
411fail_free_inode_info:
412	kmem_cache_destroy(fscrypt_inode_info_cachep);
413fail_free_queue:
414	destroy_workqueue(fscrypt_read_workqueue);
415fail:
416	return err;
417}
418late_initcall(fscrypt_init)