2 * linux/fs/ext4/crypto.c
4 * Copyright (C) 2015, Google, Inc.
6 * This contains encryption functions for ext4
8 * Written by Michael Halcrow, 2014.
10 * Filename encryption additions
11 * Uday Savagaonkar, 2014
12 * Encryption policy handling additions
13 * Ildar Muslukhov, 2014
15 * This has not yet undergone a rigorous security audit.
17 * The usage of AES-XTS should conform to recommendations in NIST
18 * Special Publication 800-38E and IEEE P1619/D16.
21 #include <crypto/skcipher.h>
22 #include <keys/user-type.h>
23 #include <keys/encrypted-type.h>
24 #include <linux/ecryptfs.h>
25 #include <linux/gfp.h>
26 #include <linux/kernel.h>
27 #include <linux/key.h>
28 #include <linux/list.h>
29 #include <linux/mempool.h>
30 #include <linux/module.h>
31 #include <linux/mutex.h>
32 #include <linux/random.h>
33 #include <linux/scatterlist.h>
34 #include <linux/spinlock_types.h>
36 #include "ext4_extents.h"
39 /* Encryption added and removed here! (L: */
41 static unsigned int num_prealloc_crypto_pages = 32;
42 static unsigned int num_prealloc_crypto_ctxs = 128;
44 module_param(num_prealloc_crypto_pages, uint, 0444);
45 MODULE_PARM_DESC(num_prealloc_crypto_pages,
46 "Number of crypto pages to preallocate");
47 module_param(num_prealloc_crypto_ctxs, uint, 0444);
48 MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
49 "Number of crypto contexts to preallocate");
51 static mempool_t *ext4_bounce_page_pool;
53 static LIST_HEAD(ext4_free_crypto_ctxs);
54 static DEFINE_SPINLOCK(ext4_crypto_ctx_lock);
56 static struct kmem_cache *ext4_crypto_ctx_cachep;
57 struct kmem_cache *ext4_crypt_info_cachep;
60 * ext4_release_crypto_ctx() - Releases an encryption context
61 * @ctx: The encryption context to release.
63 * If the encryption context was allocated from the pre-allocated pool, returns
64 * it to that pool. Else, frees it.
66 * If there's a bounce page in the context, this frees that.
68 void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx)
72 if (ctx->flags & EXT4_WRITE_PATH_FL && ctx->w.bounce_page)
73 mempool_free(ctx->w.bounce_page, ext4_bounce_page_pool);
74 ctx->w.bounce_page = NULL;
75 ctx->w.control_page = NULL;
76 if (ctx->flags & EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL) {
77 kmem_cache_free(ext4_crypto_ctx_cachep, ctx);
79 spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
80 list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
81 spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
86 * ext4_get_crypto_ctx() - Gets an encryption context
87 * @inode: The inode for which we are doing the crypto
89 * Allocates and initializes an encryption context.
91 * Return: An allocated and initialized encryption context on success; error
92 * value or NULL otherwise.
94 struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode)
96 struct ext4_crypto_ctx *ctx = NULL;
99 struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
102 return ERR_PTR(-ENOKEY);
105 * We first try getting the ctx from a free list because in
106 * the common case the ctx will have an allocated and
107 * initialized crypto tfm, so it's probably a worthwhile
108 * optimization. For the bounce page, we first try getting it
109 * from the kernel allocator because that's just about as fast
110 * as getting it from a list and because a cache of free pages
111 * should generally be a "last resort" option for a filesystem
112 * to be able to do its job.
114 spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
115 ctx = list_first_entry_or_null(&ext4_free_crypto_ctxs,
116 struct ext4_crypto_ctx, free_list);
118 list_del(&ctx->free_list);
119 spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
121 ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS);
126 ctx->flags |= EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
128 ctx->flags &= ~EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
130 ctx->flags &= ~EXT4_WRITE_PATH_FL;
134 if (!IS_ERR_OR_NULL(ctx))
135 ext4_release_crypto_ctx(ctx);
141 struct workqueue_struct *ext4_read_workqueue;
142 static DEFINE_MUTEX(crypto_init);
145 * ext4_exit_crypto() - Shutdown the ext4 encryption system
147 void ext4_exit_crypto(void)
149 struct ext4_crypto_ctx *pos, *n;
151 list_for_each_entry_safe(pos, n, &ext4_free_crypto_ctxs, free_list)
152 kmem_cache_free(ext4_crypto_ctx_cachep, pos);
153 INIT_LIST_HEAD(&ext4_free_crypto_ctxs);
154 if (ext4_bounce_page_pool)
155 mempool_destroy(ext4_bounce_page_pool);
156 ext4_bounce_page_pool = NULL;
157 if (ext4_read_workqueue)
158 destroy_workqueue(ext4_read_workqueue);
159 ext4_read_workqueue = NULL;
160 if (ext4_crypto_ctx_cachep)
161 kmem_cache_destroy(ext4_crypto_ctx_cachep);
162 ext4_crypto_ctx_cachep = NULL;
163 if (ext4_crypt_info_cachep)
164 kmem_cache_destroy(ext4_crypt_info_cachep);
165 ext4_crypt_info_cachep = NULL;
169 * ext4_init_crypto() - Set up for ext4 encryption.
171 * We only call this when we start accessing encrypted files, since it
172 * results in memory getting allocated that wouldn't otherwise be used.
174 * Return: Zero on success, non-zero otherwise.
176 int ext4_init_crypto(void)
178 int i, res = -ENOMEM;
180 mutex_lock(&crypto_init);
181 if (ext4_read_workqueue)
182 goto already_initialized;
183 ext4_read_workqueue = alloc_workqueue("ext4_crypto", WQ_HIGHPRI, 0);
184 if (!ext4_read_workqueue)
187 ext4_crypto_ctx_cachep = KMEM_CACHE(ext4_crypto_ctx,
188 SLAB_RECLAIM_ACCOUNT);
189 if (!ext4_crypto_ctx_cachep)
192 ext4_crypt_info_cachep = KMEM_CACHE(ext4_crypt_info,
193 SLAB_RECLAIM_ACCOUNT);
194 if (!ext4_crypt_info_cachep)
197 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
198 struct ext4_crypto_ctx *ctx;
200 ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS);
205 list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
208 ext4_bounce_page_pool =
209 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
210 if (!ext4_bounce_page_pool) {
215 mutex_unlock(&crypto_init);
219 mutex_unlock(&crypto_init);
223 void ext4_restore_control_page(struct page *data_page)
225 struct ext4_crypto_ctx *ctx =
226 (struct ext4_crypto_ctx *)page_private(data_page);
228 set_page_private(data_page, (unsigned long)NULL);
229 ClearPagePrivate(data_page);
230 unlock_page(data_page);
231 ext4_release_crypto_ctx(ctx);
235 * ext4_crypt_complete() - The completion callback for page encryption
236 * @req: The asynchronous encryption request context
237 * @res: The result of the encryption operation
239 static void ext4_crypt_complete(struct crypto_async_request *req, int res)
241 struct ext4_completion_result *ecr = req->data;
243 if (res == -EINPROGRESS)
246 complete(&ecr->completion);
254 static int ext4_page_crypto(struct inode *inode,
257 struct page *src_page,
258 struct page *dest_page)
261 u8 xts_tweak[EXT4_XTS_TWEAK_SIZE];
262 struct skcipher_request *req = NULL;
263 DECLARE_EXT4_COMPLETION_RESULT(ecr);
264 struct scatterlist dst, src;
265 struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
266 struct crypto_skcipher *tfm = ci->ci_ctfm;
269 req = skcipher_request_alloc(tfm, GFP_NOFS);
271 printk_ratelimited(KERN_ERR
272 "%s: crypto_request_alloc() failed\n",
276 skcipher_request_set_callback(
277 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
278 ext4_crypt_complete, &ecr);
280 BUILD_BUG_ON(EXT4_XTS_TWEAK_SIZE < sizeof(index));
281 memcpy(xts_tweak, &index, sizeof(index));
282 memset(&xts_tweak[sizeof(index)], 0,
283 EXT4_XTS_TWEAK_SIZE - sizeof(index));
285 sg_init_table(&dst, 1);
286 sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0);
287 sg_init_table(&src, 1);
288 sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0);
289 skcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
291 if (rw == EXT4_DECRYPT)
292 res = crypto_skcipher_decrypt(req);
294 res = crypto_skcipher_encrypt(req);
295 if (res == -EINPROGRESS || res == -EBUSY) {
296 wait_for_completion(&ecr.completion);
299 skcipher_request_free(req);
303 "%s: crypto_skcipher_encrypt() returned %d\n",
310 static struct page *alloc_bounce_page(struct ext4_crypto_ctx *ctx)
312 ctx->w.bounce_page = mempool_alloc(ext4_bounce_page_pool, GFP_NOWAIT);
313 if (ctx->w.bounce_page == NULL)
314 return ERR_PTR(-ENOMEM);
315 ctx->flags |= EXT4_WRITE_PATH_FL;
316 return ctx->w.bounce_page;
320 * ext4_encrypt() - Encrypts a page
321 * @inode: The inode for which the encryption should take place
322 * @plaintext_page: The page to encrypt. Must be locked.
324 * Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
325 * encryption context.
327 * Called on the page write path. The caller must call
328 * ext4_restore_control_page() on the returned ciphertext page to
329 * release the bounce buffer and the encryption context.
331 * Return: An allocated page with the encrypted content on success. Else, an
332 * error value or NULL.
334 struct page *ext4_encrypt(struct inode *inode,
335 struct page *plaintext_page)
337 struct ext4_crypto_ctx *ctx;
338 struct page *ciphertext_page = NULL;
341 BUG_ON(!PageLocked(plaintext_page));
343 ctx = ext4_get_crypto_ctx(inode);
345 return (struct page *) ctx;
347 /* The encryption operation will require a bounce page. */
348 ciphertext_page = alloc_bounce_page(ctx);
349 if (IS_ERR(ciphertext_page))
351 ctx->w.control_page = plaintext_page;
352 err = ext4_page_crypto(inode, EXT4_ENCRYPT, plaintext_page->index,
353 plaintext_page, ciphertext_page);
355 ciphertext_page = ERR_PTR(err);
357 ext4_release_crypto_ctx(ctx);
358 return ciphertext_page;
360 SetPagePrivate(ciphertext_page);
361 set_page_private(ciphertext_page, (unsigned long)ctx);
362 lock_page(ciphertext_page);
363 return ciphertext_page;
367 * ext4_decrypt() - Decrypts a page in-place
368 * @ctx: The encryption context.
369 * @page: The page to decrypt. Must be locked.
371 * Decrypts page in-place using the ctx encryption context.
373 * Called from the read completion callback.
375 * Return: Zero on success, non-zero otherwise.
377 int ext4_decrypt(struct page *page)
379 BUG_ON(!PageLocked(page));
381 return ext4_page_crypto(page->mapping->host,
382 EXT4_DECRYPT, page->index, page, page);
385 int ext4_encrypted_zeroout(struct inode *inode, ext4_lblk_t lblk,
386 ext4_fsblk_t pblk, ext4_lblk_t len)
388 struct ext4_crypto_ctx *ctx;
389 struct page *ciphertext_page = NULL;
394 ext4_msg(inode->i_sb, KERN_CRIT,
395 "ext4_encrypted_zeroout ino %lu lblk %u len %u",
396 (unsigned long) inode->i_ino, lblk, len);
399 BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE);
401 ctx = ext4_get_crypto_ctx(inode);
405 ciphertext_page = alloc_bounce_page(ctx);
406 if (IS_ERR(ciphertext_page)) {
407 err = PTR_ERR(ciphertext_page);
412 err = ext4_page_crypto(inode, EXT4_ENCRYPT, lblk,
413 ZERO_PAGE(0), ciphertext_page);
417 bio = bio_alloc(GFP_KERNEL, 1);
422 bio->bi_bdev = inode->i_sb->s_bdev;
423 bio->bi_iter.bi_sector =
424 pblk << (inode->i_sb->s_blocksize_bits - 9);
425 ret = bio_add_page(bio, ciphertext_page,
426 inode->i_sb->s_blocksize, 0);
427 if (ret != inode->i_sb->s_blocksize) {
428 /* should never happen! */
429 ext4_msg(inode->i_sb, KERN_ERR,
430 "bio_add_page failed: %d", ret);
436 err = submit_bio_wait(WRITE, bio);
437 if ((err == 0) && bio->bi_error)
446 ext4_release_crypto_ctx(ctx);
450 bool ext4_valid_contents_enc_mode(uint32_t mode)
452 return (mode == EXT4_ENCRYPTION_MODE_AES_256_XTS);
456 * ext4_validate_encryption_key_size() - Validate the encryption key size
457 * @mode: The key mode.
458 * @size: The key size to validate.
460 * Return: The validated key size for @mode. Zero if invalid.
462 uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size)
464 if (size == ext4_encryption_key_size(mode))
470 * Validate dentries for encrypted directories to make sure we aren't
471 * potentially caching stale data after a key has been added or
474 static int ext4_d_revalidate(struct dentry *dentry, unsigned int flags)
476 struct inode *dir = d_inode(dentry->d_parent);
477 struct ext4_crypt_info *ci = EXT4_I(dir)->i_crypt_info;
478 int dir_has_key, cached_with_key;
480 if (!ext4_encrypted_inode(dir))
483 if (ci && ci->ci_keyring_key &&
484 (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
485 (1 << KEY_FLAG_REVOKED) |
486 (1 << KEY_FLAG_DEAD))))
489 /* this should eventually be an flag in d_flags */
490 cached_with_key = dentry->d_fsdata != NULL;
491 dir_has_key = (ci != NULL);
494 * If the dentry was cached without the key, and it is a
495 * negative dentry, it might be a valid name. We can't check
496 * if the key has since been made available due to locking
497 * reasons, so we fail the validation so ext4_lookup() can do
500 * We also fail the validation if the dentry was created with
501 * the key present, but we no longer have the key, or vice versa.
503 if ((!cached_with_key && d_is_negative(dentry)) ||
504 (!cached_with_key && dir_has_key) ||
505 (cached_with_key && !dir_has_key)) {
506 #if 0 /* Revalidation debug */
508 char *cp = simple_dname(dentry, buf, sizeof(buf));
512 pr_err("revalidate: %s %p %d %d %d\n", cp, dentry->d_fsdata,
513 cached_with_key, d_is_negative(dentry),
521 const struct dentry_operations ext4_encrypted_d_ops = {
522 .d_revalidate = ext4_d_revalidate,