inotify: invalid mask should return a error number but not set it
[linux-2.6.git] / fs / ecryptfs / crypto.c
1 /**
2  * eCryptfs: Linux filesystem encryption layer
3  *
4  * Copyright (C) 1997-2004 Erez Zadok
5  * Copyright (C) 2001-2004 Stony Brook University
6  * Copyright (C) 2004-2007 International Business Machines Corp.
7  *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
8  *              Michael C. Thompson <mcthomps@us.ibm.com>
9  *
10  * This program is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU General Public License as
12  * published by the Free Software Foundation; either version 2 of the
13  * License, or (at your option) any later version.
14  *
15  * This program is distributed in the hope that it will be useful, but
16  * WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
18  * General Public License for more details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with this program; if not, write to the Free Software
22  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
23  * 02111-1307, USA.
24  */
25
26 #include <linux/fs.h>
27 #include <linux/mount.h>
28 #include <linux/pagemap.h>
29 #include <linux/random.h>
30 #include <linux/compiler.h>
31 #include <linux/key.h>
32 #include <linux/namei.h>
33 #include <linux/crypto.h>
34 #include <linux/file.h>
35 #include <linux/scatterlist.h>
36 #include <linux/slab.h>
37 #include <asm/unaligned.h>
38 #include "ecryptfs_kernel.h"
39
40 static int
41 ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
42                              struct page *dst_page, int dst_offset,
43                              struct page *src_page, int src_offset, int size,
44                              unsigned char *iv);
45 static int
46 ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
47                              struct page *dst_page, int dst_offset,
48                              struct page *src_page, int src_offset, int size,
49                              unsigned char *iv);
50
51 /**
52  * ecryptfs_to_hex
53  * @dst: Buffer to take hex character representation of contents of
54  *       src; must be at least of size (src_size * 2)
55  * @src: Buffer to be converted to a hex string respresentation
56  * @src_size: number of bytes to convert
57  */
58 void ecryptfs_to_hex(char *dst, char *src, size_t src_size)
59 {
60         int x;
61
62         for (x = 0; x < src_size; x++)
63                 sprintf(&dst[x * 2], "%.2x", (unsigned char)src[x]);
64 }
65
66 /**
67  * ecryptfs_from_hex
68  * @dst: Buffer to take the bytes from src hex; must be at least of
69  *       size (src_size / 2)
70  * @src: Buffer to be converted from a hex string respresentation to raw value
71  * @dst_size: size of dst buffer, or number of hex characters pairs to convert
72  */
73 void ecryptfs_from_hex(char *dst, char *src, int dst_size)
74 {
75         int x;
76         char tmp[3] = { 0, };
77
78         for (x = 0; x < dst_size; x++) {
79                 tmp[0] = src[x * 2];
80                 tmp[1] = src[x * 2 + 1];
81                 dst[x] = (unsigned char)simple_strtol(tmp, NULL, 16);
82         }
83 }
84
85 /**
86  * ecryptfs_calculate_md5 - calculates the md5 of @src
87  * @dst: Pointer to 16 bytes of allocated memory
88  * @crypt_stat: Pointer to crypt_stat struct for the current inode
89  * @src: Data to be md5'd
90  * @len: Length of @src
91  *
92  * Uses the allocated crypto context that crypt_stat references to
93  * generate the MD5 sum of the contents of src.
94  */
95 static int ecryptfs_calculate_md5(char *dst,
96                                   struct ecryptfs_crypt_stat *crypt_stat,
97                                   char *src, int len)
98 {
99         struct scatterlist sg;
100         struct hash_desc desc = {
101                 .tfm = crypt_stat->hash_tfm,
102                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
103         };
104         int rc = 0;
105
106         mutex_lock(&crypt_stat->cs_hash_tfm_mutex);
107         sg_init_one(&sg, (u8 *)src, len);
108         if (!desc.tfm) {
109                 desc.tfm = crypto_alloc_hash(ECRYPTFS_DEFAULT_HASH, 0,
110                                              CRYPTO_ALG_ASYNC);
111                 if (IS_ERR(desc.tfm)) {
112                         rc = PTR_ERR(desc.tfm);
113                         ecryptfs_printk(KERN_ERR, "Error attempting to "
114                                         "allocate crypto context; rc = [%d]\n",
115                                         rc);
116                         goto out;
117                 }
118                 crypt_stat->hash_tfm = desc.tfm;
119         }
120         rc = crypto_hash_init(&desc);
121         if (rc) {
122                 printk(KERN_ERR
123                        "%s: Error initializing crypto hash; rc = [%d]\n",
124                        __func__, rc);
125                 goto out;
126         }
127         rc = crypto_hash_update(&desc, &sg, len);
128         if (rc) {
129                 printk(KERN_ERR
130                        "%s: Error updating crypto hash; rc = [%d]\n",
131                        __func__, rc);
132                 goto out;
133         }
134         rc = crypto_hash_final(&desc, dst);
135         if (rc) {
136                 printk(KERN_ERR
137                        "%s: Error finalizing crypto hash; rc = [%d]\n",
138                        __func__, rc);
139                 goto out;
140         }
141 out:
142         mutex_unlock(&crypt_stat->cs_hash_tfm_mutex);
143         return rc;
144 }
145
146 static int ecryptfs_crypto_api_algify_cipher_name(char **algified_name,
147                                                   char *cipher_name,
148                                                   char *chaining_modifier)
149 {
150         int cipher_name_len = strlen(cipher_name);
151         int chaining_modifier_len = strlen(chaining_modifier);
152         int algified_name_len;
153         int rc;
154
155         algified_name_len = (chaining_modifier_len + cipher_name_len + 3);
156         (*algified_name) = kmalloc(algified_name_len, GFP_KERNEL);
157         if (!(*algified_name)) {
158                 rc = -ENOMEM;
159                 goto out;
160         }
161         snprintf((*algified_name), algified_name_len, "%s(%s)",
162                  chaining_modifier, cipher_name);
163         rc = 0;
164 out:
165         return rc;
166 }
167
168 /**
169  * ecryptfs_derive_iv
170  * @iv: destination for the derived iv vale
171  * @crypt_stat: Pointer to crypt_stat struct for the current inode
172  * @offset: Offset of the extent whose IV we are to derive
173  *
174  * Generate the initialization vector from the given root IV and page
175  * offset.
176  *
177  * Returns zero on success; non-zero on error.
178  */
179 int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
180                        loff_t offset)
181 {
182         int rc = 0;
183         char dst[MD5_DIGEST_SIZE];
184         char src[ECRYPTFS_MAX_IV_BYTES + 16];
185
186         if (unlikely(ecryptfs_verbosity > 0)) {
187                 ecryptfs_printk(KERN_DEBUG, "root iv:\n");
188                 ecryptfs_dump_hex(crypt_stat->root_iv, crypt_stat->iv_bytes);
189         }
190         /* TODO: It is probably secure to just cast the least
191          * significant bits of the root IV into an unsigned long and
192          * add the offset to that rather than go through all this
193          * hashing business. -Halcrow */
194         memcpy(src, crypt_stat->root_iv, crypt_stat->iv_bytes);
195         memset((src + crypt_stat->iv_bytes), 0, 16);
196         snprintf((src + crypt_stat->iv_bytes), 16, "%lld", offset);
197         if (unlikely(ecryptfs_verbosity > 0)) {
198                 ecryptfs_printk(KERN_DEBUG, "source:\n");
199                 ecryptfs_dump_hex(src, (crypt_stat->iv_bytes + 16));
200         }
201         rc = ecryptfs_calculate_md5(dst, crypt_stat, src,
202                                     (crypt_stat->iv_bytes + 16));
203         if (rc) {
204                 ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
205                                 "MD5 while generating IV for a page\n");
206                 goto out;
207         }
208         memcpy(iv, dst, crypt_stat->iv_bytes);
209         if (unlikely(ecryptfs_verbosity > 0)) {
210                 ecryptfs_printk(KERN_DEBUG, "derived iv:\n");
211                 ecryptfs_dump_hex(iv, crypt_stat->iv_bytes);
212         }
213 out:
214         return rc;
215 }
216
217 /**
218  * ecryptfs_init_crypt_stat
219  * @crypt_stat: Pointer to the crypt_stat struct to initialize.
220  *
221  * Initialize the crypt_stat structure.
222  */
223 void
224 ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
225 {
226         memset((void *)crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
227         INIT_LIST_HEAD(&crypt_stat->keysig_list);
228         mutex_init(&crypt_stat->keysig_list_mutex);
229         mutex_init(&crypt_stat->cs_mutex);
230         mutex_init(&crypt_stat->cs_tfm_mutex);
231         mutex_init(&crypt_stat->cs_hash_tfm_mutex);
232         crypt_stat->flags |= ECRYPTFS_STRUCT_INITIALIZED;
233 }
234
235 /**
236  * ecryptfs_destroy_crypt_stat
237  * @crypt_stat: Pointer to the crypt_stat struct to initialize.
238  *
239  * Releases all memory associated with a crypt_stat struct.
240  */
241 void ecryptfs_destroy_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
242 {
243         struct ecryptfs_key_sig *key_sig, *key_sig_tmp;
244
245         if (crypt_stat->tfm)
246                 crypto_free_blkcipher(crypt_stat->tfm);
247         if (crypt_stat->hash_tfm)
248                 crypto_free_hash(crypt_stat->hash_tfm);
249         list_for_each_entry_safe(key_sig, key_sig_tmp,
250                                  &crypt_stat->keysig_list, crypt_stat_list) {
251                 list_del(&key_sig->crypt_stat_list);
252                 kmem_cache_free(ecryptfs_key_sig_cache, key_sig);
253         }
254         memset(crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
255 }
256
257 void ecryptfs_destroy_mount_crypt_stat(
258         struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
259 {
260         struct ecryptfs_global_auth_tok *auth_tok, *auth_tok_tmp;
261
262         if (!(mount_crypt_stat->flags & ECRYPTFS_MOUNT_CRYPT_STAT_INITIALIZED))
263                 return;
264         mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
265         list_for_each_entry_safe(auth_tok, auth_tok_tmp,
266                                  &mount_crypt_stat->global_auth_tok_list,
267                                  mount_crypt_stat_list) {
268                 list_del(&auth_tok->mount_crypt_stat_list);
269                 if (auth_tok->global_auth_tok_key
270                     && !(auth_tok->flags & ECRYPTFS_AUTH_TOK_INVALID))
271                         key_put(auth_tok->global_auth_tok_key);
272                 kmem_cache_free(ecryptfs_global_auth_tok_cache, auth_tok);
273         }
274         mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
275         memset(mount_crypt_stat, 0, sizeof(struct ecryptfs_mount_crypt_stat));
276 }
277
278 /**
279  * virt_to_scatterlist
280  * @addr: Virtual address
281  * @size: Size of data; should be an even multiple of the block size
282  * @sg: Pointer to scatterlist array; set to NULL to obtain only
283  *      the number of scatterlist structs required in array
284  * @sg_size: Max array size
285  *
286  * Fills in a scatterlist array with page references for a passed
287  * virtual address.
288  *
289  * Returns the number of scatterlist structs in array used
290  */
291 int virt_to_scatterlist(const void *addr, int size, struct scatterlist *sg,
292                         int sg_size)
293 {
294         int i = 0;
295         struct page *pg;
296         int offset;
297         int remainder_of_page;
298
299         sg_init_table(sg, sg_size);
300
301         while (size > 0 && i < sg_size) {
302                 pg = virt_to_page(addr);
303                 offset = offset_in_page(addr);
304                 if (sg)
305                         sg_set_page(&sg[i], pg, 0, offset);
306                 remainder_of_page = PAGE_CACHE_SIZE - offset;
307                 if (size >= remainder_of_page) {
308                         if (sg)
309                                 sg[i].length = remainder_of_page;
310                         addr += remainder_of_page;
311                         size -= remainder_of_page;
312                 } else {
313                         if (sg)
314                                 sg[i].length = size;
315                         addr += size;
316                         size = 0;
317                 }
318                 i++;
319         }
320         if (size > 0)
321                 return -ENOMEM;
322         return i;
323 }
324
325 /**
326  * encrypt_scatterlist
327  * @crypt_stat: Pointer to the crypt_stat struct to initialize.
328  * @dest_sg: Destination of encrypted data
329  * @src_sg: Data to be encrypted
330  * @size: Length of data to be encrypted
331  * @iv: iv to use during encryption
332  *
333  * Returns the number of bytes encrypted; negative value on error
334  */
335 static int encrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
336                                struct scatterlist *dest_sg,
337                                struct scatterlist *src_sg, int size,
338                                unsigned char *iv)
339 {
340         struct blkcipher_desc desc = {
341                 .tfm = crypt_stat->tfm,
342                 .info = iv,
343                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
344         };
345         int rc = 0;
346
347         BUG_ON(!crypt_stat || !crypt_stat->tfm
348                || !(crypt_stat->flags & ECRYPTFS_STRUCT_INITIALIZED));
349         if (unlikely(ecryptfs_verbosity > 0)) {
350                 ecryptfs_printk(KERN_DEBUG, "Key size [%zd]; key:\n",
351                                 crypt_stat->key_size);
352                 ecryptfs_dump_hex(crypt_stat->key,
353                                   crypt_stat->key_size);
354         }
355         /* Consider doing this once, when the file is opened */
356         mutex_lock(&crypt_stat->cs_tfm_mutex);
357         if (!(crypt_stat->flags & ECRYPTFS_KEY_SET)) {
358                 rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
359                                              crypt_stat->key_size);
360                 crypt_stat->flags |= ECRYPTFS_KEY_SET;
361         }
362         if (rc) {
363                 ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
364                                 rc);
365                 mutex_unlock(&crypt_stat->cs_tfm_mutex);
366                 rc = -EINVAL;
367                 goto out;
368         }
369         ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes.\n", size);
370         crypto_blkcipher_encrypt_iv(&desc, dest_sg, src_sg, size);
371         mutex_unlock(&crypt_stat->cs_tfm_mutex);
372 out:
373         return rc;
374 }
375
376 /**
377  * ecryptfs_lower_offset_for_extent
378  *
379  * Convert an eCryptfs page index into a lower byte offset
380  */
381 static void ecryptfs_lower_offset_for_extent(loff_t *offset, loff_t extent_num,
382                                              struct ecryptfs_crypt_stat *crypt_stat)
383 {
384         (*offset) = ecryptfs_lower_header_size(crypt_stat)
385                     + (crypt_stat->extent_size * extent_num);
386 }
387
388 /**
389  * ecryptfs_encrypt_extent
390  * @enc_extent_page: Allocated page into which to encrypt the data in
391  *                   @page
392  * @crypt_stat: crypt_stat containing cryptographic context for the
393  *              encryption operation
394  * @page: Page containing plaintext data extent to encrypt
395  * @extent_offset: Page extent offset for use in generating IV
396  *
397  * Encrypts one extent of data.
398  *
399  * Return zero on success; non-zero otherwise
400  */
401 static int ecryptfs_encrypt_extent(struct page *enc_extent_page,
402                                    struct ecryptfs_crypt_stat *crypt_stat,
403                                    struct page *page,
404                                    unsigned long extent_offset)
405 {
406         loff_t extent_base;
407         char extent_iv[ECRYPTFS_MAX_IV_BYTES];
408         int rc;
409
410         extent_base = (((loff_t)page->index)
411                        * (PAGE_CACHE_SIZE / crypt_stat->extent_size));
412         rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
413                                 (extent_base + extent_offset));
414         if (rc) {
415                 ecryptfs_printk(KERN_ERR, "Error attempting to derive IV for "
416                         "extent [0x%.16llx]; rc = [%d]\n",
417                         (unsigned long long)(extent_base + extent_offset), rc);
418                 goto out;
419         }
420         rc = ecryptfs_encrypt_page_offset(crypt_stat, enc_extent_page, 0,
421                                           page, (extent_offset
422                                                  * crypt_stat->extent_size),
423                                           crypt_stat->extent_size, extent_iv);
424         if (rc < 0) {
425                 printk(KERN_ERR "%s: Error attempting to encrypt page with "
426                        "page->index = [%ld], extent_offset = [%ld]; "
427                        "rc = [%d]\n", __func__, page->index, extent_offset,
428                        rc);
429                 goto out;
430         }
431         rc = 0;
432 out:
433         return rc;
434 }
435
436 /**
437  * ecryptfs_encrypt_page
438  * @page: Page mapped from the eCryptfs inode for the file; contains
439  *        decrypted content that needs to be encrypted (to a temporary
440  *        page; not in place) and written out to the lower file
441  *
442  * Encrypt an eCryptfs page. This is done on a per-extent basis. Note
443  * that eCryptfs pages may straddle the lower pages -- for instance,
444  * if the file was created on a machine with an 8K page size
445  * (resulting in an 8K header), and then the file is copied onto a
446  * host with a 32K page size, then when reading page 0 of the eCryptfs
447  * file, 24K of page 0 of the lower file will be read and decrypted,
448  * and then 8K of page 1 of the lower file will be read and decrypted.
449  *
450  * Returns zero on success; negative on error
451  */
452 int ecryptfs_encrypt_page(struct page *page)
453 {
454         struct inode *ecryptfs_inode;
455         struct ecryptfs_crypt_stat *crypt_stat;
456         char *enc_extent_virt;
457         struct page *enc_extent_page = NULL;
458         loff_t extent_offset;
459         int rc = 0;
460
461         ecryptfs_inode = page->mapping->host;
462         crypt_stat =
463                 &(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);
464         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
465         enc_extent_page = alloc_page(GFP_USER);
466         if (!enc_extent_page) {
467                 rc = -ENOMEM;
468                 ecryptfs_printk(KERN_ERR, "Error allocating memory for "
469                                 "encrypted extent\n");
470                 goto out;
471         }
472         enc_extent_virt = kmap(enc_extent_page);
473         for (extent_offset = 0;
474              extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
475              extent_offset++) {
476                 loff_t offset;
477
478                 rc = ecryptfs_encrypt_extent(enc_extent_page, crypt_stat, page,
479                                              extent_offset);
480                 if (rc) {
481                         printk(KERN_ERR "%s: Error encrypting extent; "
482                                "rc = [%d]\n", __func__, rc);
483                         goto out;
484                 }
485                 ecryptfs_lower_offset_for_extent(
486                         &offset, ((((loff_t)page->index)
487                                    * (PAGE_CACHE_SIZE
488                                       / crypt_stat->extent_size))
489                                   + extent_offset), crypt_stat);
490                 rc = ecryptfs_write_lower(ecryptfs_inode, enc_extent_virt,
491                                           offset, crypt_stat->extent_size);
492                 if (rc < 0) {
493                         ecryptfs_printk(KERN_ERR, "Error attempting "
494                                         "to write lower page; rc = [%d]"
495                                         "\n", rc);
496                         goto out;
497                 }
498         }
499         rc = 0;
500 out:
501         if (enc_extent_page) {
502                 kunmap(enc_extent_page);
503                 __free_page(enc_extent_page);
504         }
505         return rc;
506 }
507
508 static int ecryptfs_decrypt_extent(struct page *page,
509                                    struct ecryptfs_crypt_stat *crypt_stat,
510                                    struct page *enc_extent_page,
511                                    unsigned long extent_offset)
512 {
513         loff_t extent_base;
514         char extent_iv[ECRYPTFS_MAX_IV_BYTES];
515         int rc;
516
517         extent_base = (((loff_t)page->index)
518                        * (PAGE_CACHE_SIZE / crypt_stat->extent_size));
519         rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
520                                 (extent_base + extent_offset));
521         if (rc) {
522                 ecryptfs_printk(KERN_ERR, "Error attempting to derive IV for "
523                         "extent [0x%.16llx]; rc = [%d]\n",
524                         (unsigned long long)(extent_base + extent_offset), rc);
525                 goto out;
526         }
527         rc = ecryptfs_decrypt_page_offset(crypt_stat, page,
528                                           (extent_offset
529                                            * crypt_stat->extent_size),
530                                           enc_extent_page, 0,
531                                           crypt_stat->extent_size, extent_iv);
532         if (rc < 0) {
533                 printk(KERN_ERR "%s: Error attempting to decrypt to page with "
534                        "page->index = [%ld], extent_offset = [%ld]; "
535                        "rc = [%d]\n", __func__, page->index, extent_offset,
536                        rc);
537                 goto out;
538         }
539         rc = 0;
540 out:
541         return rc;
542 }
543
544 /**
545  * ecryptfs_decrypt_page
546  * @page: Page mapped from the eCryptfs inode for the file; data read
547  *        and decrypted from the lower file will be written into this
548  *        page
549  *
550  * Decrypt an eCryptfs page. This is done on a per-extent basis. Note
551  * that eCryptfs pages may straddle the lower pages -- for instance,
552  * if the file was created on a machine with an 8K page size
553  * (resulting in an 8K header), and then the file is copied onto a
554  * host with a 32K page size, then when reading page 0 of the eCryptfs
555  * file, 24K of page 0 of the lower file will be read and decrypted,
556  * and then 8K of page 1 of the lower file will be read and decrypted.
557  *
558  * Returns zero on success; negative on error
559  */
560 int ecryptfs_decrypt_page(struct page *page)
561 {
562         struct inode *ecryptfs_inode;
563         struct ecryptfs_crypt_stat *crypt_stat;
564         char *enc_extent_virt;
565         struct page *enc_extent_page = NULL;
566         unsigned long extent_offset;
567         int rc = 0;
568
569         ecryptfs_inode = page->mapping->host;
570         crypt_stat =
571                 &(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);
572         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
573         enc_extent_page = alloc_page(GFP_USER);
574         if (!enc_extent_page) {
575                 rc = -ENOMEM;
576                 ecryptfs_printk(KERN_ERR, "Error allocating memory for "
577                                 "encrypted extent\n");
578                 goto out;
579         }
580         enc_extent_virt = kmap(enc_extent_page);
581         for (extent_offset = 0;
582              extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
583              extent_offset++) {
584                 loff_t offset;
585
586                 ecryptfs_lower_offset_for_extent(
587                         &offset, ((page->index * (PAGE_CACHE_SIZE
588                                                   / crypt_stat->extent_size))
589                                   + extent_offset), crypt_stat);
590                 rc = ecryptfs_read_lower(enc_extent_virt, offset,
591                                          crypt_stat->extent_size,
592                                          ecryptfs_inode);
593                 if (rc < 0) {
594                         ecryptfs_printk(KERN_ERR, "Error attempting "
595                                         "to read lower page; rc = [%d]"
596                                         "\n", rc);
597                         goto out;
598                 }
599                 rc = ecryptfs_decrypt_extent(page, crypt_stat, enc_extent_page,
600                                              extent_offset);
601                 if (rc) {
602                         printk(KERN_ERR "%s: Error encrypting extent; "
603                                "rc = [%d]\n", __func__, rc);
604                         goto out;
605                 }
606         }
607 out:
608         if (enc_extent_page) {
609                 kunmap(enc_extent_page);
610                 __free_page(enc_extent_page);
611         }
612         return rc;
613 }
614
615 /**
616  * decrypt_scatterlist
617  * @crypt_stat: Cryptographic context
618  * @dest_sg: The destination scatterlist to decrypt into
619  * @src_sg: The source scatterlist to decrypt from
620  * @size: The number of bytes to decrypt
621  * @iv: The initialization vector to use for the decryption
622  *
623  * Returns the number of bytes decrypted; negative value on error
624  */
625 static int decrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
626                                struct scatterlist *dest_sg,
627                                struct scatterlist *src_sg, int size,
628                                unsigned char *iv)
629 {
630         struct blkcipher_desc desc = {
631                 .tfm = crypt_stat->tfm,
632                 .info = iv,
633                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
634         };
635         int rc = 0;
636
637         /* Consider doing this once, when the file is opened */
638         mutex_lock(&crypt_stat->cs_tfm_mutex);
639         rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
640                                      crypt_stat->key_size);
641         if (rc) {
642                 ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
643                                 rc);
644                 mutex_unlock(&crypt_stat->cs_tfm_mutex);
645                 rc = -EINVAL;
646                 goto out;
647         }
648         ecryptfs_printk(KERN_DEBUG, "Decrypting [%d] bytes.\n", size);
649         rc = crypto_blkcipher_decrypt_iv(&desc, dest_sg, src_sg, size);
650         mutex_unlock(&crypt_stat->cs_tfm_mutex);
651         if (rc) {
652                 ecryptfs_printk(KERN_ERR, "Error decrypting; rc = [%d]\n",
653                                 rc);
654                 goto out;
655         }
656         rc = size;
657 out:
658         return rc;
659 }
660
661 /**
662  * ecryptfs_encrypt_page_offset
663  * @crypt_stat: The cryptographic context
664  * @dst_page: The page to encrypt into
665  * @dst_offset: The offset in the page to encrypt into
666  * @src_page: The page to encrypt from
667  * @src_offset: The offset in the page to encrypt from
668  * @size: The number of bytes to encrypt
669  * @iv: The initialization vector to use for the encryption
670  *
671  * Returns the number of bytes encrypted
672  */
673 static int
674 ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
675                              struct page *dst_page, int dst_offset,
676                              struct page *src_page, int src_offset, int size,
677                              unsigned char *iv)
678 {
679         struct scatterlist src_sg, dst_sg;
680
681         sg_init_table(&src_sg, 1);
682         sg_init_table(&dst_sg, 1);
683
684         sg_set_page(&src_sg, src_page, size, src_offset);
685         sg_set_page(&dst_sg, dst_page, size, dst_offset);
686         return encrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
687 }
688
689 /**
690  * ecryptfs_decrypt_page_offset
691  * @crypt_stat: The cryptographic context
692  * @dst_page: The page to decrypt into
693  * @dst_offset: The offset in the page to decrypt into
694  * @src_page: The page to decrypt from
695  * @src_offset: The offset in the page to decrypt from
696  * @size: The number of bytes to decrypt
697  * @iv: The initialization vector to use for the decryption
698  *
699  * Returns the number of bytes decrypted
700  */
701 static int
702 ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
703                              struct page *dst_page, int dst_offset,
704                              struct page *src_page, int src_offset, int size,
705                              unsigned char *iv)
706 {
707         struct scatterlist src_sg, dst_sg;
708
709         sg_init_table(&src_sg, 1);
710         sg_set_page(&src_sg, src_page, size, src_offset);
711
712         sg_init_table(&dst_sg, 1);
713         sg_set_page(&dst_sg, dst_page, size, dst_offset);
714
715         return decrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
716 }
717
718 #define ECRYPTFS_MAX_SCATTERLIST_LEN 4
719
720 /**
721  * ecryptfs_init_crypt_ctx
722  * @crypt_stat: Uninitialized crypt stats structure
723  *
724  * Initialize the crypto context.
725  *
726  * TODO: Performance: Keep a cache of initialized cipher contexts;
727  * only init if needed
728  */
729 int ecryptfs_init_crypt_ctx(struct ecryptfs_crypt_stat *crypt_stat)
730 {
731         char *full_alg_name;
732         int rc = -EINVAL;
733
734         if (!crypt_stat->cipher) {
735                 ecryptfs_printk(KERN_ERR, "No cipher specified\n");
736                 goto out;
737         }
738         ecryptfs_printk(KERN_DEBUG,
739                         "Initializing cipher [%s]; strlen = [%d]; "
740                         "key_size_bits = [%zd]\n",
741                         crypt_stat->cipher, (int)strlen(crypt_stat->cipher),
742                         crypt_stat->key_size << 3);
743         if (crypt_stat->tfm) {
744                 rc = 0;
745                 goto out;
746         }
747         mutex_lock(&crypt_stat->cs_tfm_mutex);
748         rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
749                                                     crypt_stat->cipher, "cbc");
750         if (rc)
751                 goto out_unlock;
752         crypt_stat->tfm = crypto_alloc_blkcipher(full_alg_name, 0,
753                                                  CRYPTO_ALG_ASYNC);
754         kfree(full_alg_name);
755         if (IS_ERR(crypt_stat->tfm)) {
756                 rc = PTR_ERR(crypt_stat->tfm);
757                 crypt_stat->tfm = NULL;
758                 ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
759                                 "Error initializing cipher [%s]\n",
760                                 crypt_stat->cipher);
761                 goto out_unlock;
762         }
763         crypto_blkcipher_set_flags(crypt_stat->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
764         rc = 0;
765 out_unlock:
766         mutex_unlock(&crypt_stat->cs_tfm_mutex);
767 out:
768         return rc;
769 }
770
771 static void set_extent_mask_and_shift(struct ecryptfs_crypt_stat *crypt_stat)
772 {
773         int extent_size_tmp;
774
775         crypt_stat->extent_mask = 0xFFFFFFFF;
776         crypt_stat->extent_shift = 0;
777         if (crypt_stat->extent_size == 0)
778                 return;
779         extent_size_tmp = crypt_stat->extent_size;
780         while ((extent_size_tmp & 0x01) == 0) {
781                 extent_size_tmp >>= 1;
782                 crypt_stat->extent_mask <<= 1;
783                 crypt_stat->extent_shift++;
784         }
785 }
786
787 void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat)
788 {
789         /* Default values; may be overwritten as we are parsing the
790          * packets. */
791         crypt_stat->extent_size = ECRYPTFS_DEFAULT_EXTENT_SIZE;
792         set_extent_mask_and_shift(crypt_stat);
793         crypt_stat->iv_bytes = ECRYPTFS_DEFAULT_IV_BYTES;
794         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
795                 crypt_stat->metadata_size = ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
796         else {
797                 if (PAGE_CACHE_SIZE <= ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)
798                         crypt_stat->metadata_size =
799                                 ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
800                 else
801                         crypt_stat->metadata_size = PAGE_CACHE_SIZE;
802         }
803 }
804
805 /**
806  * ecryptfs_compute_root_iv
807  * @crypt_stats
808  *
809  * On error, sets the root IV to all 0's.
810  */
811 int ecryptfs_compute_root_iv(struct ecryptfs_crypt_stat *crypt_stat)
812 {
813         int rc = 0;
814         char dst[MD5_DIGEST_SIZE];
815
816         BUG_ON(crypt_stat->iv_bytes > MD5_DIGEST_SIZE);
817         BUG_ON(crypt_stat->iv_bytes <= 0);
818         if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
819                 rc = -EINVAL;
820                 ecryptfs_printk(KERN_WARNING, "Session key not valid; "
821                                 "cannot generate root IV\n");
822                 goto out;
823         }
824         rc = ecryptfs_calculate_md5(dst, crypt_stat, crypt_stat->key,
825                                     crypt_stat->key_size);
826         if (rc) {
827                 ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
828                                 "MD5 while generating root IV\n");
829                 goto out;
830         }
831         memcpy(crypt_stat->root_iv, dst, crypt_stat->iv_bytes);
832 out:
833         if (rc) {
834                 memset(crypt_stat->root_iv, 0, crypt_stat->iv_bytes);
835                 crypt_stat->flags |= ECRYPTFS_SECURITY_WARNING;
836         }
837         return rc;
838 }
839
840 static void ecryptfs_generate_new_key(struct ecryptfs_crypt_stat *crypt_stat)
841 {
842         get_random_bytes(crypt_stat->key, crypt_stat->key_size);
843         crypt_stat->flags |= ECRYPTFS_KEY_VALID;
844         ecryptfs_compute_root_iv(crypt_stat);
845         if (unlikely(ecryptfs_verbosity > 0)) {
846                 ecryptfs_printk(KERN_DEBUG, "Generated new session key:\n");
847                 ecryptfs_dump_hex(crypt_stat->key,
848                                   crypt_stat->key_size);
849         }
850 }
851
852 /**
853  * ecryptfs_copy_mount_wide_flags_to_inode_flags
854  * @crypt_stat: The inode's cryptographic context
855  * @mount_crypt_stat: The mount point's cryptographic context
856  *
857  * This function propagates the mount-wide flags to individual inode
858  * flags.
859  */
860 static void ecryptfs_copy_mount_wide_flags_to_inode_flags(
861         struct ecryptfs_crypt_stat *crypt_stat,
862         struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
863 {
864         if (mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED)
865                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
866         if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
867                 crypt_stat->flags |= ECRYPTFS_VIEW_AS_ENCRYPTED;
868         if (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES) {
869                 crypt_stat->flags |= ECRYPTFS_ENCRYPT_FILENAMES;
870                 if (mount_crypt_stat->flags
871                     & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK)
872                         crypt_stat->flags |= ECRYPTFS_ENCFN_USE_MOUNT_FNEK;
873                 else if (mount_crypt_stat->flags
874                          & ECRYPTFS_GLOBAL_ENCFN_USE_FEK)
875                         crypt_stat->flags |= ECRYPTFS_ENCFN_USE_FEK;
876         }
877 }
878
879 static int ecryptfs_copy_mount_wide_sigs_to_inode_sigs(
880         struct ecryptfs_crypt_stat *crypt_stat,
881         struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
882 {
883         struct ecryptfs_global_auth_tok *global_auth_tok;
884         int rc = 0;
885
886         mutex_lock(&crypt_stat->keysig_list_mutex);
887         mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
888
889         list_for_each_entry(global_auth_tok,
890                             &mount_crypt_stat->global_auth_tok_list,
891                             mount_crypt_stat_list) {
892                 if (global_auth_tok->flags & ECRYPTFS_AUTH_TOK_FNEK)
893                         continue;
894                 rc = ecryptfs_add_keysig(crypt_stat, global_auth_tok->sig);
895                 if (rc) {
896                         printk(KERN_ERR "Error adding keysig; rc = [%d]\n", rc);
897                         goto out;
898                 }
899         }
900
901 out:
902         mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
903         mutex_unlock(&crypt_stat->keysig_list_mutex);
904         return rc;
905 }
906
907 /**
908  * ecryptfs_set_default_crypt_stat_vals
909  * @crypt_stat: The inode's cryptographic context
910  * @mount_crypt_stat: The mount point's cryptographic context
911  *
912  * Default values in the event that policy does not override them.
913  */
914 static void ecryptfs_set_default_crypt_stat_vals(
915         struct ecryptfs_crypt_stat *crypt_stat,
916         struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
917 {
918         ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
919                                                       mount_crypt_stat);
920         ecryptfs_set_default_sizes(crypt_stat);
921         strcpy(crypt_stat->cipher, ECRYPTFS_DEFAULT_CIPHER);
922         crypt_stat->key_size = ECRYPTFS_DEFAULT_KEY_BYTES;
923         crypt_stat->flags &= ~(ECRYPTFS_KEY_VALID);
924         crypt_stat->file_version = ECRYPTFS_FILE_VERSION;
925         crypt_stat->mount_crypt_stat = mount_crypt_stat;
926 }
927
928 /**
929  * ecryptfs_new_file_context
930  * @ecryptfs_inode: The eCryptfs inode
931  *
932  * If the crypto context for the file has not yet been established,
933  * this is where we do that.  Establishing a new crypto context
934  * involves the following decisions:
935  *  - What cipher to use?
936  *  - What set of authentication tokens to use?
937  * Here we just worry about getting enough information into the
938  * authentication tokens so that we know that they are available.
939  * We associate the available authentication tokens with the new file
940  * via the set of signatures in the crypt_stat struct.  Later, when
941  * the headers are actually written out, we may again defer to
942  * userspace to perform the encryption of the session key; for the
943  * foreseeable future, this will be the case with public key packets.
944  *
945  * Returns zero on success; non-zero otherwise
946  */
947 int ecryptfs_new_file_context(struct inode *ecryptfs_inode)
948 {
949         struct ecryptfs_crypt_stat *crypt_stat =
950             &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
951         struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
952             &ecryptfs_superblock_to_private(
953                     ecryptfs_inode->i_sb)->mount_crypt_stat;
954         int cipher_name_len;
955         int rc = 0;
956
957         ecryptfs_set_default_crypt_stat_vals(crypt_stat, mount_crypt_stat);
958         crypt_stat->flags |= (ECRYPTFS_ENCRYPTED | ECRYPTFS_KEY_VALID);
959         ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
960                                                       mount_crypt_stat);
961         rc = ecryptfs_copy_mount_wide_sigs_to_inode_sigs(crypt_stat,
962                                                          mount_crypt_stat);
963         if (rc) {
964                 printk(KERN_ERR "Error attempting to copy mount-wide key sigs "
965                        "to the inode key sigs; rc = [%d]\n", rc);
966                 goto out;
967         }
968         cipher_name_len =
969                 strlen(mount_crypt_stat->global_default_cipher_name);
970         memcpy(crypt_stat->cipher,
971                mount_crypt_stat->global_default_cipher_name,
972                cipher_name_len);
973         crypt_stat->cipher[cipher_name_len] = '\0';
974         crypt_stat->key_size =
975                 mount_crypt_stat->global_default_cipher_key_size;
976         ecryptfs_generate_new_key(crypt_stat);
977         rc = ecryptfs_init_crypt_ctx(crypt_stat);
978         if (rc)
979                 ecryptfs_printk(KERN_ERR, "Error initializing cryptographic "
980                                 "context for cipher [%s]: rc = [%d]\n",
981                                 crypt_stat->cipher, rc);
982 out:
983         return rc;
984 }
985
986 /**
987  * ecryptfs_validate_marker - check for the ecryptfs marker
988  * @data: The data block in which to check
989  *
990  * Returns zero if marker found; -EINVAL if not found
991  */
992 static int ecryptfs_validate_marker(char *data)
993 {
994         u32 m_1, m_2;
995
996         m_1 = get_unaligned_be32(data);
997         m_2 = get_unaligned_be32(data + 4);
998         if ((m_1 ^ MAGIC_ECRYPTFS_MARKER) == m_2)
999                 return 0;
1000         ecryptfs_printk(KERN_DEBUG, "m_1 = [0x%.8x]; m_2 = [0x%.8x]; "
1001                         "MAGIC_ECRYPTFS_MARKER = [0x%.8x]\n", m_1, m_2,
1002                         MAGIC_ECRYPTFS_MARKER);
1003         ecryptfs_printk(KERN_DEBUG, "(m_1 ^ MAGIC_ECRYPTFS_MARKER) = "
1004                         "[0x%.8x]\n", (m_1 ^ MAGIC_ECRYPTFS_MARKER));
1005         return -EINVAL;
1006 }
1007
1008 struct ecryptfs_flag_map_elem {
1009         u32 file_flag;
1010         u32 local_flag;
1011 };
1012
1013 /* Add support for additional flags by adding elements here. */
1014 static struct ecryptfs_flag_map_elem ecryptfs_flag_map[] = {
1015         {0x00000001, ECRYPTFS_ENABLE_HMAC},
1016         {0x00000002, ECRYPTFS_ENCRYPTED},
1017         {0x00000004, ECRYPTFS_METADATA_IN_XATTR},
1018         {0x00000008, ECRYPTFS_ENCRYPT_FILENAMES}
1019 };
1020
1021 /**
1022  * ecryptfs_process_flags
1023  * @crypt_stat: The cryptographic context
1024  * @page_virt: Source data to be parsed
1025  * @bytes_read: Updated with the number of bytes read
1026  *
1027  * Returns zero on success; non-zero if the flag set is invalid
1028  */
1029 static int ecryptfs_process_flags(struct ecryptfs_crypt_stat *crypt_stat,
1030                                   char *page_virt, int *bytes_read)
1031 {
1032         int rc = 0;
1033         int i;
1034         u32 flags;
1035
1036         flags = get_unaligned_be32(page_virt);
1037         for (i = 0; i < ((sizeof(ecryptfs_flag_map)
1038                           / sizeof(struct ecryptfs_flag_map_elem))); i++)
1039                 if (flags & ecryptfs_flag_map[i].file_flag) {
1040                         crypt_stat->flags |= ecryptfs_flag_map[i].local_flag;
1041                 } else
1042                         crypt_stat->flags &= ~(ecryptfs_flag_map[i].local_flag);
1043         /* Version is in top 8 bits of the 32-bit flag vector */
1044         crypt_stat->file_version = ((flags >> 24) & 0xFF);
1045         (*bytes_read) = 4;
1046         return rc;
1047 }
1048
1049 /**
1050  * write_ecryptfs_marker
1051  * @page_virt: The pointer to in a page to begin writing the marker
1052  * @written: Number of bytes written
1053  *
1054  * Marker = 0x3c81b7f5
1055  */
1056 static void write_ecryptfs_marker(char *page_virt, size_t *written)
1057 {
1058         u32 m_1, m_2;
1059
1060         get_random_bytes(&m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
1061         m_2 = (m_1 ^ MAGIC_ECRYPTFS_MARKER);
1062         put_unaligned_be32(m_1, page_virt);
1063         page_virt += (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2);
1064         put_unaligned_be32(m_2, page_virt);
1065         (*written) = MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
1066 }
1067
1068 void ecryptfs_write_crypt_stat_flags(char *page_virt,
1069                                      struct ecryptfs_crypt_stat *crypt_stat,
1070                                      size_t *written)
1071 {
1072         u32 flags = 0;
1073         int i;
1074
1075         for (i = 0; i < ((sizeof(ecryptfs_flag_map)
1076                           / sizeof(struct ecryptfs_flag_map_elem))); i++)
1077                 if (crypt_stat->flags & ecryptfs_flag_map[i].local_flag)
1078                         flags |= ecryptfs_flag_map[i].file_flag;
1079         /* Version is in top 8 bits of the 32-bit flag vector */
1080         flags |= ((((u8)crypt_stat->file_version) << 24) & 0xFF000000);
1081         put_unaligned_be32(flags, page_virt);
1082         (*written) = 4;
1083 }
1084
1085 struct ecryptfs_cipher_code_str_map_elem {
1086         char cipher_str[16];
1087         u8 cipher_code;
1088 };
1089
1090 /* Add support for additional ciphers by adding elements here. The
1091  * cipher_code is whatever OpenPGP applicatoins use to identify the
1092  * ciphers. List in order of probability. */
1093 static struct ecryptfs_cipher_code_str_map_elem
1094 ecryptfs_cipher_code_str_map[] = {
1095         {"aes",RFC2440_CIPHER_AES_128 },
1096         {"blowfish", RFC2440_CIPHER_BLOWFISH},
1097         {"des3_ede", RFC2440_CIPHER_DES3_EDE},
1098         {"cast5", RFC2440_CIPHER_CAST_5},
1099         {"twofish", RFC2440_CIPHER_TWOFISH},
1100         {"cast6", RFC2440_CIPHER_CAST_6},
1101         {"aes", RFC2440_CIPHER_AES_192},
1102         {"aes", RFC2440_CIPHER_AES_256}
1103 };
1104
1105 /**
1106  * ecryptfs_code_for_cipher_string
1107  * @cipher_name: The string alias for the cipher
1108  * @key_bytes: Length of key in bytes; used for AES code selection
1109  *
1110  * Returns zero on no match, or the cipher code on match
1111  */
1112 u8 ecryptfs_code_for_cipher_string(char *cipher_name, size_t key_bytes)
1113 {
1114         int i;
1115         u8 code = 0;
1116         struct ecryptfs_cipher_code_str_map_elem *map =
1117                 ecryptfs_cipher_code_str_map;
1118
1119         if (strcmp(cipher_name, "aes") == 0) {
1120                 switch (key_bytes) {
1121                 case 16:
1122                         code = RFC2440_CIPHER_AES_128;
1123                         break;
1124                 case 24:
1125                         code = RFC2440_CIPHER_AES_192;
1126                         break;
1127                 case 32:
1128                         code = RFC2440_CIPHER_AES_256;
1129                 }
1130         } else {
1131                 for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
1132                         if (strcmp(cipher_name, map[i].cipher_str) == 0) {
1133                                 code = map[i].cipher_code;
1134                                 break;
1135                         }
1136         }
1137         return code;
1138 }
1139
1140 /**
1141  * ecryptfs_cipher_code_to_string
1142  * @str: Destination to write out the cipher name
1143  * @cipher_code: The code to convert to cipher name string
1144  *
1145  * Returns zero on success
1146  */
1147 int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code)
1148 {
1149         int rc = 0;
1150         int i;
1151
1152         str[0] = '\0';
1153         for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
1154                 if (cipher_code == ecryptfs_cipher_code_str_map[i].cipher_code)
1155                         strcpy(str, ecryptfs_cipher_code_str_map[i].cipher_str);
1156         if (str[0] == '\0') {
1157                 ecryptfs_printk(KERN_WARNING, "Cipher code not recognized: "
1158                                 "[%d]\n", cipher_code);
1159                 rc = -EINVAL;
1160         }
1161         return rc;
1162 }
1163
1164 int ecryptfs_read_and_validate_header_region(struct inode *inode)
1165 {
1166         u8 file_size[ECRYPTFS_SIZE_AND_MARKER_BYTES];
1167         u8 *marker = file_size + ECRYPTFS_FILE_SIZE_BYTES;
1168         int rc;
1169
1170         rc = ecryptfs_read_lower(file_size, 0, ECRYPTFS_SIZE_AND_MARKER_BYTES,
1171                                  inode);
1172         if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
1173                 return rc >= 0 ? -EINVAL : rc;
1174         rc = ecryptfs_validate_marker(marker);
1175         if (!rc)
1176                 ecryptfs_i_size_init(file_size, inode);
1177         return rc;
1178 }
1179
1180 void
1181 ecryptfs_write_header_metadata(char *virt,
1182                                struct ecryptfs_crypt_stat *crypt_stat,
1183                                size_t *written)
1184 {
1185         u32 header_extent_size;
1186         u16 num_header_extents_at_front;
1187
1188         header_extent_size = (u32)crypt_stat->extent_size;
1189         num_header_extents_at_front =
1190                 (u16)(crypt_stat->metadata_size / crypt_stat->extent_size);
1191         put_unaligned_be32(header_extent_size, virt);
1192         virt += 4;
1193         put_unaligned_be16(num_header_extents_at_front, virt);
1194         (*written) = 6;
1195 }
1196
1197 struct kmem_cache *ecryptfs_header_cache;
1198
1199 /**
1200  * ecryptfs_write_headers_virt
1201  * @page_virt: The virtual address to write the headers to
1202  * @max: The size of memory allocated at page_virt
1203  * @size: Set to the number of bytes written by this function
1204  * @crypt_stat: The cryptographic context
1205  * @ecryptfs_dentry: The eCryptfs dentry
1206  *
1207  * Format version: 1
1208  *
1209  *   Header Extent:
1210  *     Octets 0-7:        Unencrypted file size (big-endian)
1211  *     Octets 8-15:       eCryptfs special marker
1212  *     Octets 16-19:      Flags
1213  *      Octet 16:         File format version number (between 0 and 255)
1214  *      Octets 17-18:     Reserved
1215  *      Octet 19:         Bit 1 (lsb): Reserved
1216  *                        Bit 2: Encrypted?
1217  *                        Bits 3-8: Reserved
1218  *     Octets 20-23:      Header extent size (big-endian)
1219  *     Octets 24-25:      Number of header extents at front of file
1220  *                        (big-endian)
1221  *     Octet  26:         Begin RFC 2440 authentication token packet set
1222  *   Data Extent 0:
1223  *     Lower data (CBC encrypted)
1224  *   Data Extent 1:
1225  *     Lower data (CBC encrypted)
1226  *   ...
1227  *
1228  * Returns zero on success
1229  */
1230 static int ecryptfs_write_headers_virt(char *page_virt, size_t max,
1231                                        size_t *size,
1232                                        struct ecryptfs_crypt_stat *crypt_stat,
1233                                        struct dentry *ecryptfs_dentry)
1234 {
1235         int rc;
1236         size_t written;
1237         size_t offset;
1238
1239         offset = ECRYPTFS_FILE_SIZE_BYTES;
1240         write_ecryptfs_marker((page_virt + offset), &written);
1241         offset += written;
1242         ecryptfs_write_crypt_stat_flags((page_virt + offset), crypt_stat,
1243                                         &written);
1244         offset += written;
1245         ecryptfs_write_header_metadata((page_virt + offset), crypt_stat,
1246                                        &written);
1247         offset += written;
1248         rc = ecryptfs_generate_key_packet_set((page_virt + offset), crypt_stat,
1249                                               ecryptfs_dentry, &written,
1250                                               max - offset);
1251         if (rc)
1252                 ecryptfs_printk(KERN_WARNING, "Error generating key packet "
1253                                 "set; rc = [%d]\n", rc);
1254         if (size) {
1255                 offset += written;
1256                 *size = offset;
1257         }
1258         return rc;
1259 }
1260
1261 static int
1262 ecryptfs_write_metadata_to_contents(struct inode *ecryptfs_inode,
1263                                     char *virt, size_t virt_len)
1264 {
1265         int rc;
1266
1267         rc = ecryptfs_write_lower(ecryptfs_inode, virt,
1268                                   0, virt_len);
1269         if (rc < 0)
1270                 printk(KERN_ERR "%s: Error attempting to write header "
1271                        "information to lower file; rc = [%d]\n", __func__, rc);
1272         else
1273                 rc = 0;
1274         return rc;
1275 }
1276
1277 static int
1278 ecryptfs_write_metadata_to_xattr(struct dentry *ecryptfs_dentry,
1279                                  char *page_virt, size_t size)
1280 {
1281         int rc;
1282
1283         rc = ecryptfs_setxattr(ecryptfs_dentry, ECRYPTFS_XATTR_NAME, page_virt,
1284                                size, 0);
1285         return rc;
1286 }
1287
1288 static unsigned long ecryptfs_get_zeroed_pages(gfp_t gfp_mask,
1289                                                unsigned int order)
1290 {
1291         struct page *page;
1292
1293         page = alloc_pages(gfp_mask | __GFP_ZERO, order);
1294         if (page)
1295                 return (unsigned long) page_address(page);
1296         return 0;
1297 }
1298
1299 /**
1300  * ecryptfs_write_metadata
1301  * @ecryptfs_dentry: The eCryptfs dentry, which should be negative
1302  * @ecryptfs_inode: The newly created eCryptfs inode
1303  *
1304  * Write the file headers out.  This will likely involve a userspace
1305  * callout, in which the session key is encrypted with one or more
1306  * public keys and/or the passphrase necessary to do the encryption is
1307  * retrieved via a prompt.  Exactly what happens at this point should
1308  * be policy-dependent.
1309  *
1310  * Returns zero on success; non-zero on error
1311  */
1312 int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry,
1313                             struct inode *ecryptfs_inode)
1314 {
1315         struct ecryptfs_crypt_stat *crypt_stat =
1316                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
1317         unsigned int order;
1318         char *virt;
1319         size_t virt_len;
1320         size_t size = 0;
1321         int rc = 0;
1322
1323         if (likely(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
1324                 if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
1325                         printk(KERN_ERR "Key is invalid; bailing out\n");
1326                         rc = -EINVAL;
1327                         goto out;
1328                 }
1329         } else {
1330                 printk(KERN_WARNING "%s: Encrypted flag not set\n",
1331                        __func__);
1332                 rc = -EINVAL;
1333                 goto out;
1334         }
1335         virt_len = crypt_stat->metadata_size;
1336         order = get_order(virt_len);
1337         /* Released in this function */
1338         virt = (char *)ecryptfs_get_zeroed_pages(GFP_KERNEL, order);
1339         if (!virt) {
1340                 printk(KERN_ERR "%s: Out of memory\n", __func__);
1341                 rc = -ENOMEM;
1342                 goto out;
1343         }
1344         /* Zeroed page ensures the in-header unencrypted i_size is set to 0 */
1345         rc = ecryptfs_write_headers_virt(virt, virt_len, &size, crypt_stat,
1346                                          ecryptfs_dentry);
1347         if (unlikely(rc)) {
1348                 printk(KERN_ERR "%s: Error whilst writing headers; rc = [%d]\n",
1349                        __func__, rc);
1350                 goto out_free;
1351         }
1352         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
1353                 rc = ecryptfs_write_metadata_to_xattr(ecryptfs_dentry, virt,
1354                                                       size);
1355         else
1356                 rc = ecryptfs_write_metadata_to_contents(ecryptfs_inode, virt,
1357                                                          virt_len);
1358         if (rc) {
1359                 printk(KERN_ERR "%s: Error writing metadata out to lower file; "
1360                        "rc = [%d]\n", __func__, rc);
1361                 goto out_free;
1362         }
1363 out_free:
1364         free_pages((unsigned long)virt, order);
1365 out:
1366         return rc;
1367 }
1368
1369 #define ECRYPTFS_DONT_VALIDATE_HEADER_SIZE 0
1370 #define ECRYPTFS_VALIDATE_HEADER_SIZE 1
1371 static int parse_header_metadata(struct ecryptfs_crypt_stat *crypt_stat,
1372                                  char *virt, int *bytes_read,
1373                                  int validate_header_size)
1374 {
1375         int rc = 0;
1376         u32 header_extent_size;
1377         u16 num_header_extents_at_front;
1378
1379         header_extent_size = get_unaligned_be32(virt);
1380         virt += sizeof(__be32);
1381         num_header_extents_at_front = get_unaligned_be16(virt);
1382         crypt_stat->metadata_size = (((size_t)num_header_extents_at_front
1383                                      * (size_t)header_extent_size));
1384         (*bytes_read) = (sizeof(__be32) + sizeof(__be16));
1385         if ((validate_header_size == ECRYPTFS_VALIDATE_HEADER_SIZE)
1386             && (crypt_stat->metadata_size
1387                 < ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)) {
1388                 rc = -EINVAL;
1389                 printk(KERN_WARNING "Invalid header size: [%zd]\n",
1390                        crypt_stat->metadata_size);
1391         }
1392         return rc;
1393 }
1394
1395 /**
1396  * set_default_header_data
1397  * @crypt_stat: The cryptographic context
1398  *
1399  * For version 0 file format; this function is only for backwards
1400  * compatibility for files created with the prior versions of
1401  * eCryptfs.
1402  */
1403 static void set_default_header_data(struct ecryptfs_crypt_stat *crypt_stat)
1404 {
1405         crypt_stat->metadata_size = ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
1406 }
1407
1408 void ecryptfs_i_size_init(const char *page_virt, struct inode *inode)
1409 {
1410         struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
1411         struct ecryptfs_crypt_stat *crypt_stat;
1412         u64 file_size;
1413
1414         crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
1415         mount_crypt_stat =
1416                 &ecryptfs_superblock_to_private(inode->i_sb)->mount_crypt_stat;
1417         if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED) {
1418                 file_size = i_size_read(ecryptfs_inode_to_lower(inode));
1419                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
1420                         file_size += crypt_stat->metadata_size;
1421         } else
1422                 file_size = get_unaligned_be64(page_virt);
1423         i_size_write(inode, (loff_t)file_size);
1424         crypt_stat->flags |= ECRYPTFS_I_SIZE_INITIALIZED;
1425 }
1426
1427 /**
1428  * ecryptfs_read_headers_virt
1429  * @page_virt: The virtual address into which to read the headers
1430  * @crypt_stat: The cryptographic context
1431  * @ecryptfs_dentry: The eCryptfs dentry
1432  * @validate_header_size: Whether to validate the header size while reading
1433  *
1434  * Read/parse the header data. The header format is detailed in the
1435  * comment block for the ecryptfs_write_headers_virt() function.
1436  *
1437  * Returns zero on success
1438  */
1439 static int ecryptfs_read_headers_virt(char *page_virt,
1440                                       struct ecryptfs_crypt_stat *crypt_stat,
1441                                       struct dentry *ecryptfs_dentry,
1442                                       int validate_header_size)
1443 {
1444         int rc = 0;
1445         int offset;
1446         int bytes_read;
1447
1448         ecryptfs_set_default_sizes(crypt_stat);
1449         crypt_stat->mount_crypt_stat = &ecryptfs_superblock_to_private(
1450                 ecryptfs_dentry->d_sb)->mount_crypt_stat;
1451         offset = ECRYPTFS_FILE_SIZE_BYTES;
1452         rc = ecryptfs_validate_marker(page_virt + offset);
1453         if (rc)
1454                 goto out;
1455         if (!(crypt_stat->flags & ECRYPTFS_I_SIZE_INITIALIZED))
1456                 ecryptfs_i_size_init(page_virt, ecryptfs_dentry->d_inode);
1457         offset += MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
1458         rc = ecryptfs_process_flags(crypt_stat, (page_virt + offset),
1459                                     &bytes_read);
1460         if (rc) {
1461                 ecryptfs_printk(KERN_WARNING, "Error processing flags\n");
1462                 goto out;
1463         }
1464         if (crypt_stat->file_version > ECRYPTFS_SUPPORTED_FILE_VERSION) {
1465                 ecryptfs_printk(KERN_WARNING, "File version is [%d]; only "
1466                                 "file version [%d] is supported by this "
1467                                 "version of eCryptfs\n",
1468                                 crypt_stat->file_version,
1469                                 ECRYPTFS_SUPPORTED_FILE_VERSION);
1470                 rc = -EINVAL;
1471                 goto out;
1472         }
1473         offset += bytes_read;
1474         if (crypt_stat->file_version >= 1) {
1475                 rc = parse_header_metadata(crypt_stat, (page_virt + offset),
1476                                            &bytes_read, validate_header_size);
1477                 if (rc) {
1478                         ecryptfs_printk(KERN_WARNING, "Error reading header "
1479                                         "metadata; rc = [%d]\n", rc);
1480                 }
1481                 offset += bytes_read;
1482         } else
1483                 set_default_header_data(crypt_stat);
1484         rc = ecryptfs_parse_packet_set(crypt_stat, (page_virt + offset),
1485                                        ecryptfs_dentry);
1486 out:
1487         return rc;
1488 }
1489
1490 /**
1491  * ecryptfs_read_xattr_region
1492  * @page_virt: The vitual address into which to read the xattr data
1493  * @ecryptfs_inode: The eCryptfs inode
1494  *
1495  * Attempts to read the crypto metadata from the extended attribute
1496  * region of the lower file.
1497  *
1498  * Returns zero on success; non-zero on error
1499  */
1500 int ecryptfs_read_xattr_region(char *page_virt, struct inode *ecryptfs_inode)
1501 {
1502         struct dentry *lower_dentry =
1503                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
1504         ssize_t size;
1505         int rc = 0;
1506
1507         size = ecryptfs_getxattr_lower(lower_dentry, ECRYPTFS_XATTR_NAME,
1508                                        page_virt, ECRYPTFS_DEFAULT_EXTENT_SIZE);
1509         if (size < 0) {
1510                 if (unlikely(ecryptfs_verbosity > 0))
1511                         printk(KERN_INFO "Error attempting to read the [%s] "
1512                                "xattr from the lower file; return value = "
1513                                "[%zd]\n", ECRYPTFS_XATTR_NAME, size);
1514                 rc = -EINVAL;
1515                 goto out;
1516         }
1517 out:
1518         return rc;
1519 }
1520
1521 int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,
1522                                             struct inode *inode)
1523 {
1524         u8 file_size[ECRYPTFS_SIZE_AND_MARKER_BYTES];
1525         u8 *marker = file_size + ECRYPTFS_FILE_SIZE_BYTES;
1526         int rc;
1527
1528         rc = ecryptfs_getxattr_lower(ecryptfs_dentry_to_lower(dentry),
1529                                      ECRYPTFS_XATTR_NAME, file_size,
1530                                      ECRYPTFS_SIZE_AND_MARKER_BYTES);
1531         if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
1532                 return rc >= 0 ? -EINVAL : rc;
1533         rc = ecryptfs_validate_marker(marker);
1534         if (!rc)
1535                 ecryptfs_i_size_init(file_size, inode);
1536         return rc;
1537 }
1538
1539 /**
1540  * ecryptfs_read_metadata
1541  *
1542  * Common entry point for reading file metadata. From here, we could
1543  * retrieve the header information from the header region of the file,
1544  * the xattr region of the file, or some other repostory that is
1545  * stored separately from the file itself. The current implementation
1546  * supports retrieving the metadata information from the file contents
1547  * and from the xattr region.
1548  *
1549  * Returns zero if valid headers found and parsed; non-zero otherwise
1550  */
1551 int ecryptfs_read_metadata(struct dentry *ecryptfs_dentry)
1552 {
1553         int rc;
1554         char *page_virt;
1555         struct inode *ecryptfs_inode = ecryptfs_dentry->d_inode;
1556         struct ecryptfs_crypt_stat *crypt_stat =
1557             &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
1558         struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
1559                 &ecryptfs_superblock_to_private(
1560                         ecryptfs_dentry->d_sb)->mount_crypt_stat;
1561
1562         ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
1563                                                       mount_crypt_stat);
1564         /* Read the first page from the underlying file */
1565         page_virt = kmem_cache_alloc(ecryptfs_header_cache, GFP_USER);
1566         if (!page_virt) {
1567                 rc = -ENOMEM;
1568                 printk(KERN_ERR "%s: Unable to allocate page_virt\n",
1569                        __func__);
1570                 goto out;
1571         }
1572         rc = ecryptfs_read_lower(page_virt, 0, crypt_stat->extent_size,
1573                                  ecryptfs_inode);
1574         if (rc >= 0)
1575                 rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
1576                                                 ecryptfs_dentry,
1577                                                 ECRYPTFS_VALIDATE_HEADER_SIZE);
1578         if (rc) {
1579                 /* metadata is not in the file header, so try xattrs */
1580                 memset(page_virt, 0, PAGE_CACHE_SIZE);
1581                 rc = ecryptfs_read_xattr_region(page_virt, ecryptfs_inode);
1582                 if (rc) {
1583                         printk(KERN_DEBUG "Valid eCryptfs headers not found in "
1584                                "file header region or xattr region, inode %lu\n",
1585                                 ecryptfs_inode->i_ino);
1586                         rc = -EINVAL;
1587                         goto out;
1588                 }
1589                 rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
1590                                                 ecryptfs_dentry,
1591                                                 ECRYPTFS_DONT_VALIDATE_HEADER_SIZE);
1592                 if (rc) {
1593                         printk(KERN_DEBUG "Valid eCryptfs headers not found in "
1594                                "file xattr region either, inode %lu\n",
1595                                 ecryptfs_inode->i_ino);
1596                         rc = -EINVAL;
1597                 }
1598                 if (crypt_stat->mount_crypt_stat->flags
1599                     & ECRYPTFS_XATTR_METADATA_ENABLED) {
1600                         crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
1601                 } else {
1602                         printk(KERN_WARNING "Attempt to access file with "
1603                                "crypto metadata only in the extended attribute "
1604                                "region, but eCryptfs was mounted without "
1605                                "xattr support enabled. eCryptfs will not treat "
1606                                "this like an encrypted file, inode %lu\n",
1607                                 ecryptfs_inode->i_ino);
1608                         rc = -EINVAL;
1609                 }
1610         }
1611 out:
1612         if (page_virt) {
1613                 memset(page_virt, 0, PAGE_CACHE_SIZE);
1614                 kmem_cache_free(ecryptfs_header_cache, page_virt);
1615         }
1616         return rc;
1617 }
1618
1619 /**
1620  * ecryptfs_encrypt_filename - encrypt filename
1621  *
1622  * CBC-encrypts the filename. We do not want to encrypt the same
1623  * filename with the same key and IV, which may happen with hard
1624  * links, so we prepend random bits to each filename.
1625  *
1626  * Returns zero on success; non-zero otherwise
1627  */
1628 static int
1629 ecryptfs_encrypt_filename(struct ecryptfs_filename *filename,
1630                           struct ecryptfs_crypt_stat *crypt_stat,
1631                           struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
1632 {
1633         int rc = 0;
1634
1635         filename->encrypted_filename = NULL;
1636         filename->encrypted_filename_size = 0;
1637         if ((crypt_stat && (crypt_stat->flags & ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
1638             || (mount_crypt_stat && (mount_crypt_stat->flags
1639                                      & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK))) {
1640                 size_t packet_size;
1641                 size_t remaining_bytes;
1642
1643                 rc = ecryptfs_write_tag_70_packet(
1644                         NULL, NULL,
1645                         &filename->encrypted_filename_size,
1646                         mount_crypt_stat, NULL,
1647                         filename->filename_size);
1648                 if (rc) {
1649                         printk(KERN_ERR "%s: Error attempting to get packet "
1650                                "size for tag 72; rc = [%d]\n", __func__,
1651                                rc);
1652                         filename->encrypted_filename_size = 0;
1653                         goto out;
1654                 }
1655                 filename->encrypted_filename =
1656                         kmalloc(filename->encrypted_filename_size, GFP_KERNEL);
1657                 if (!filename->encrypted_filename) {
1658                         printk(KERN_ERR "%s: Out of memory whilst attempting "
1659                                "to kmalloc [%zd] bytes\n", __func__,
1660                                filename->encrypted_filename_size);
1661                         rc = -ENOMEM;
1662                         goto out;
1663                 }
1664                 remaining_bytes = filename->encrypted_filename_size;
1665                 rc = ecryptfs_write_tag_70_packet(filename->encrypted_filename,
1666                                                   &remaining_bytes,
1667                                                   &packet_size,
1668                                                   mount_crypt_stat,
1669                                                   filename->filename,
1670                                                   filename->filename_size);
1671                 if (rc) {
1672                         printk(KERN_ERR "%s: Error attempting to generate "
1673                                "tag 70 packet; rc = [%d]\n", __func__,
1674                                rc);
1675                         kfree(filename->encrypted_filename);
1676                         filename->encrypted_filename = NULL;
1677                         filename->encrypted_filename_size = 0;
1678                         goto out;
1679                 }
1680                 filename->encrypted_filename_size = packet_size;
1681         } else {
1682                 printk(KERN_ERR "%s: No support for requested filename "
1683                        "encryption method in this release\n", __func__);
1684                 rc = -EOPNOTSUPP;
1685                 goto out;
1686         }
1687 out:
1688         return rc;
1689 }
1690
1691 static int ecryptfs_copy_filename(char **copied_name, size_t *copied_name_size,
1692                                   const char *name, size_t name_size)
1693 {
1694         int rc = 0;
1695
1696         (*copied_name) = kmalloc((name_size + 1), GFP_KERNEL);
1697         if (!(*copied_name)) {
1698                 rc = -ENOMEM;
1699                 goto out;
1700         }
1701         memcpy((void *)(*copied_name), (void *)name, name_size);
1702         (*copied_name)[(name_size)] = '\0';     /* Only for convenience
1703                                                  * in printing out the
1704                                                  * string in debug
1705                                                  * messages */
1706         (*copied_name_size) = name_size;
1707 out:
1708         return rc;
1709 }
1710
1711 /**
1712  * ecryptfs_process_key_cipher - Perform key cipher initialization.
1713  * @key_tfm: Crypto context for key material, set by this function
1714  * @cipher_name: Name of the cipher
1715  * @key_size: Size of the key in bytes
1716  *
1717  * Returns zero on success. Any crypto_tfm structs allocated here
1718  * should be released by other functions, such as on a superblock put
1719  * event, regardless of whether this function succeeds for fails.
1720  */
1721 static int
1722 ecryptfs_process_key_cipher(struct crypto_blkcipher **key_tfm,
1723                             char *cipher_name, size_t *key_size)
1724 {
1725         char dummy_key[ECRYPTFS_MAX_KEY_BYTES];
1726         char *full_alg_name = NULL;
1727         int rc;
1728
1729         *key_tfm = NULL;
1730         if (*key_size > ECRYPTFS_MAX_KEY_BYTES) {
1731                 rc = -EINVAL;
1732                 printk(KERN_ERR "Requested key size is [%zd] bytes; maximum "
1733                       "allowable is [%d]\n", *key_size, ECRYPTFS_MAX_KEY_BYTES);
1734                 goto out;
1735         }
1736         rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name, cipher_name,
1737                                                     "ecb");
1738         if (rc)
1739                 goto out;
1740         *key_tfm = crypto_alloc_blkcipher(full_alg_name, 0, CRYPTO_ALG_ASYNC);
1741         if (IS_ERR(*key_tfm)) {
1742                 rc = PTR_ERR(*key_tfm);
1743                 printk(KERN_ERR "Unable to allocate crypto cipher with name "
1744                        "[%s]; rc = [%d]\n", full_alg_name, rc);
1745                 goto out;
1746         }
1747         crypto_blkcipher_set_flags(*key_tfm, CRYPTO_TFM_REQ_WEAK_KEY);
1748         if (*key_size == 0) {
1749                 struct blkcipher_alg *alg = crypto_blkcipher_alg(*key_tfm);
1750
1751                 *key_size = alg->max_keysize;
1752         }
1753         get_random_bytes(dummy_key, *key_size);
1754         rc = crypto_blkcipher_setkey(*key_tfm, dummy_key, *key_size);
1755         if (rc) {
1756                 printk(KERN_ERR "Error attempting to set key of size [%zd] for "
1757                        "cipher [%s]; rc = [%d]\n", *key_size, full_alg_name,
1758                        rc);
1759                 rc = -EINVAL;
1760                 goto out;
1761         }
1762 out:
1763         kfree(full_alg_name);
1764         return rc;
1765 }
1766
1767 struct kmem_cache *ecryptfs_key_tfm_cache;
1768 static struct list_head key_tfm_list;
1769 struct mutex key_tfm_list_mutex;
1770
1771 int __init ecryptfs_init_crypto(void)
1772 {
1773         mutex_init(&key_tfm_list_mutex);
1774         INIT_LIST_HEAD(&key_tfm_list);
1775         return 0;
1776 }
1777
1778 /**
1779  * ecryptfs_destroy_crypto - free all cached key_tfms on key_tfm_list
1780  *
1781  * Called only at module unload time
1782  */
1783 int ecryptfs_destroy_crypto(void)
1784 {
1785         struct ecryptfs_key_tfm *key_tfm, *key_tfm_tmp;
1786
1787         mutex_lock(&key_tfm_list_mutex);
1788         list_for_each_entry_safe(key_tfm, key_tfm_tmp, &key_tfm_list,
1789                                  key_tfm_list) {
1790                 list_del(&key_tfm->key_tfm_list);
1791                 if (key_tfm->key_tfm)
1792                         crypto_free_blkcipher(key_tfm->key_tfm);
1793                 kmem_cache_free(ecryptfs_key_tfm_cache, key_tfm);
1794         }
1795         mutex_unlock(&key_tfm_list_mutex);
1796         return 0;
1797 }
1798
1799 int
1800 ecryptfs_add_new_key_tfm(struct ecryptfs_key_tfm **key_tfm, char *cipher_name,
1801                          size_t key_size)
1802 {
1803         struct ecryptfs_key_tfm *tmp_tfm;
1804         int rc = 0;
1805
1806         BUG_ON(!mutex_is_locked(&key_tfm_list_mutex));
1807
1808         tmp_tfm = kmem_cache_alloc(ecryptfs_key_tfm_cache, GFP_KERNEL);
1809         if (key_tfm != NULL)
1810                 (*key_tfm) = tmp_tfm;
1811         if (!tmp_tfm) {
1812                 rc = -ENOMEM;
1813                 printk(KERN_ERR "Error attempting to allocate from "
1814                        "ecryptfs_key_tfm_cache\n");
1815                 goto out;
1816         }
1817         mutex_init(&tmp_tfm->key_tfm_mutex);
1818         strncpy(tmp_tfm->cipher_name, cipher_name,
1819                 ECRYPTFS_MAX_CIPHER_NAME_SIZE);
1820         tmp_tfm->cipher_name[ECRYPTFS_MAX_CIPHER_NAME_SIZE] = '\0';
1821         tmp_tfm->key_size = key_size;
1822         rc = ecryptfs_process_key_cipher(&tmp_tfm->key_tfm,
1823                                          tmp_tfm->cipher_name,
1824                                          &tmp_tfm->key_size);
1825         if (rc) {
1826                 printk(KERN_ERR "Error attempting to initialize key TFM "
1827                        "cipher with name = [%s]; rc = [%d]\n",
1828                        tmp_tfm->cipher_name, rc);
1829                 kmem_cache_free(ecryptfs_key_tfm_cache, tmp_tfm);
1830                 if (key_tfm != NULL)
1831                         (*key_tfm) = NULL;
1832                 goto out;
1833         }
1834         list_add(&tmp_tfm->key_tfm_list, &key_tfm_list);
1835 out:
1836         return rc;
1837 }
1838
1839 /**
1840  * ecryptfs_tfm_exists - Search for existing tfm for cipher_name.
1841  * @cipher_name: the name of the cipher to search for
1842  * @key_tfm: set to corresponding tfm if found
1843  *
1844  * Searches for cached key_tfm matching @cipher_name
1845  * Must be called with &key_tfm_list_mutex held
1846  * Returns 1 if found, with @key_tfm set
1847  * Returns 0 if not found, with @key_tfm set to NULL
1848  */
1849 int ecryptfs_tfm_exists(char *cipher_name, struct ecryptfs_key_tfm **key_tfm)
1850 {
1851         struct ecryptfs_key_tfm *tmp_key_tfm;
1852
1853         BUG_ON(!mutex_is_locked(&key_tfm_list_mutex));
1854
1855         list_for_each_entry(tmp_key_tfm, &key_tfm_list, key_tfm_list) {
1856                 if (strcmp(tmp_key_tfm->cipher_name, cipher_name) == 0) {
1857                         if (key_tfm)
1858                                 (*key_tfm) = tmp_key_tfm;
1859                         return 1;
1860                 }
1861         }
1862         if (key_tfm)
1863                 (*key_tfm) = NULL;
1864         return 0;
1865 }
1866
1867 /**
1868  * ecryptfs_get_tfm_and_mutex_for_cipher_name
1869  *
1870  * @tfm: set to cached tfm found, or new tfm created
1871  * @tfm_mutex: set to mutex for cached tfm found, or new tfm created
1872  * @cipher_name: the name of the cipher to search for and/or add
1873  *
1874  * Sets pointers to @tfm & @tfm_mutex matching @cipher_name.
1875  * Searches for cached item first, and creates new if not found.
1876  * Returns 0 on success, non-zero if adding new cipher failed
1877  */
1878 int ecryptfs_get_tfm_and_mutex_for_cipher_name(struct crypto_blkcipher **tfm,
1879                                                struct mutex **tfm_mutex,
1880                                                char *cipher_name)
1881 {
1882         struct ecryptfs_key_tfm *key_tfm;
1883         int rc = 0;
1884
1885         (*tfm) = NULL;
1886         (*tfm_mutex) = NULL;
1887
1888         mutex_lock(&key_tfm_list_mutex);
1889         if (!ecryptfs_tfm_exists(cipher_name, &key_tfm)) {
1890                 rc = ecryptfs_add_new_key_tfm(&key_tfm, cipher_name, 0);
1891                 if (rc) {
1892                         printk(KERN_ERR "Error adding new key_tfm to list; "
1893                                         "rc = [%d]\n", rc);
1894                         goto out;
1895                 }
1896         }
1897         (*tfm) = key_tfm->key_tfm;
1898         (*tfm_mutex) = &key_tfm->key_tfm_mutex;
1899 out:
1900         mutex_unlock(&key_tfm_list_mutex);
1901         return rc;
1902 }
1903
1904 /* 64 characters forming a 6-bit target field */
1905 static unsigned char *portable_filename_chars = ("-.0123456789ABCD"
1906                                                  "EFGHIJKLMNOPQRST"
1907                                                  "UVWXYZabcdefghij"
1908                                                  "klmnopqrstuvwxyz");
1909
1910 /* We could either offset on every reverse map or just pad some 0x00's
1911  * at the front here */
1912 static const unsigned char filename_rev_map[256] = {
1913         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 7 */
1914         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 15 */
1915         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 23 */
1916         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 31 */
1917         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 39 */
1918         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* 47 */
1919         0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, /* 55 */
1920         0x0A, 0x0B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 63 */
1921         0x00, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, /* 71 */
1922         0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, /* 79 */
1923         0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, /* 87 */
1924         0x23, 0x24, 0x25, 0x00, 0x00, 0x00, 0x00, 0x00, /* 95 */
1925         0x00, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, /* 103 */
1926         0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, /* 111 */
1927         0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, /* 119 */
1928         0x3D, 0x3E, 0x3F /* 123 - 255 initialized to 0x00 */
1929 };
1930
1931 /**
1932  * ecryptfs_encode_for_filename
1933  * @dst: Destination location for encoded filename
1934  * @dst_size: Size of the encoded filename in bytes
1935  * @src: Source location for the filename to encode
1936  * @src_size: Size of the source in bytes
1937  */
1938 void ecryptfs_encode_for_filename(unsigned char *dst, size_t *dst_size,
1939                                   unsigned char *src, size_t src_size)
1940 {
1941         size_t num_blocks;
1942         size_t block_num = 0;
1943         size_t dst_offset = 0;
1944         unsigned char last_block[3];
1945
1946         if (src_size == 0) {
1947                 (*dst_size) = 0;
1948                 goto out;
1949         }
1950         num_blocks = (src_size / 3);
1951         if ((src_size % 3) == 0) {
1952                 memcpy(last_block, (&src[src_size - 3]), 3);
1953         } else {
1954                 num_blocks++;
1955                 last_block[2] = 0x00;
1956                 switch (src_size % 3) {
1957                 case 1:
1958                         last_block[0] = src[src_size - 1];
1959                         last_block[1] = 0x00;
1960                         break;
1961                 case 2:
1962                         last_block[0] = src[src_size - 2];
1963                         last_block[1] = src[src_size - 1];
1964                 }
1965         }
1966         (*dst_size) = (num_blocks * 4);
1967         if (!dst)
1968                 goto out;
1969         while (block_num < num_blocks) {
1970                 unsigned char *src_block;
1971                 unsigned char dst_block[4];
1972
1973                 if (block_num == (num_blocks - 1))
1974                         src_block = last_block;
1975                 else
1976                         src_block = &src[block_num * 3];
1977                 dst_block[0] = ((src_block[0] >> 2) & 0x3F);
1978                 dst_block[1] = (((src_block[0] << 4) & 0x30)
1979                                 | ((src_block[1] >> 4) & 0x0F));
1980                 dst_block[2] = (((src_block[1] << 2) & 0x3C)
1981                                 | ((src_block[2] >> 6) & 0x03));
1982                 dst_block[3] = (src_block[2] & 0x3F);
1983                 dst[dst_offset++] = portable_filename_chars[dst_block[0]];
1984                 dst[dst_offset++] = portable_filename_chars[dst_block[1]];
1985                 dst[dst_offset++] = portable_filename_chars[dst_block[2]];
1986                 dst[dst_offset++] = portable_filename_chars[dst_block[3]];
1987                 block_num++;
1988         }
1989 out:
1990         return;
1991 }
1992
1993 static size_t ecryptfs_max_decoded_size(size_t encoded_size)
1994 {
1995         /* Not exact; conservatively long. Every block of 4
1996          * encoded characters decodes into a block of 3
1997          * decoded characters. This segment of code provides
1998          * the caller with the maximum amount of allocated
1999          * space that @dst will need to point to in a
2000          * subsequent call. */
2001         return ((encoded_size + 1) * 3) / 4;
2002 }
2003
2004 /**
2005  * ecryptfs_decode_from_filename
2006  * @dst: If NULL, this function only sets @dst_size and returns. If
2007  *       non-NULL, this function decodes the encoded octets in @src
2008  *       into the memory that @dst points to.
2009  * @dst_size: Set to the size of the decoded string.
2010  * @src: The encoded set of octets to decode.
2011  * @src_size: The size of the encoded set of octets to decode.
2012  */
2013 static void
2014 ecryptfs_decode_from_filename(unsigned char *dst, size_t *dst_size,
2015                               const unsigned char *src, size_t src_size)
2016 {
2017         u8 current_bit_offset = 0;
2018         size_t src_byte_offset = 0;
2019         size_t dst_byte_offset = 0;
2020
2021         if (dst == NULL) {
2022                 (*dst_size) = ecryptfs_max_decoded_size(src_size);
2023                 goto out;
2024         }
2025         while (src_byte_offset < src_size) {
2026                 unsigned char src_byte =
2027                                 filename_rev_map[(int)src[src_byte_offset]];
2028
2029                 switch (current_bit_offset) {
2030                 case 0:
2031                         dst[dst_byte_offset] = (src_byte << 2);
2032                         current_bit_offset = 6;
2033                         break;
2034                 case 6:
2035                         dst[dst_byte_offset++] |= (src_byte >> 4);
2036                         dst[dst_byte_offset] = ((src_byte & 0xF)
2037                                                  << 4);
2038                         current_bit_offset = 4;
2039                         break;
2040                 case 4:
2041                         dst[dst_byte_offset++] |= (src_byte >> 2);
2042                         dst[dst_byte_offset] = (src_byte << 6);
2043                         current_bit_offset = 2;
2044                         break;
2045                 case 2:
2046                         dst[dst_byte_offset++] |= (src_byte);
2047                         dst[dst_byte_offset] = 0;
2048                         current_bit_offset = 0;
2049                         break;
2050                 }
2051                 src_byte_offset++;
2052         }
2053         (*dst_size) = dst_byte_offset;
2054 out:
2055         return;
2056 }
2057
2058 /**
2059  * ecryptfs_encrypt_and_encode_filename - converts a plaintext file name to cipher text
2060  * @crypt_stat: The crypt_stat struct associated with the file anem to encode
2061  * @name: The plaintext name
2062  * @length: The length of the plaintext
2063  * @encoded_name: The encypted name
2064  *
2065  * Encrypts and encodes a filename into something that constitutes a
2066  * valid filename for a filesystem, with printable characters.
2067  *
2068  * We assume that we have a properly initialized crypto context,
2069  * pointed to by crypt_stat->tfm.
2070  *
2071  * Returns zero on success; non-zero on otherwise
2072  */
2073 int ecryptfs_encrypt_and_encode_filename(
2074         char **encoded_name,
2075         size_t *encoded_name_size,
2076         struct ecryptfs_crypt_stat *crypt_stat,
2077         struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
2078         const char *name, size_t name_size)
2079 {
2080         size_t encoded_name_no_prefix_size;
2081         int rc = 0;
2082
2083         (*encoded_name) = NULL;
2084         (*encoded_name_size) = 0;
2085         if ((crypt_stat && (crypt_stat->flags & ECRYPTFS_ENCRYPT_FILENAMES))
2086             || (mount_crypt_stat && (mount_crypt_stat->flags
2087                                      & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES))) {
2088                 struct ecryptfs_filename *filename;
2089
2090                 filename = kzalloc(sizeof(*filename), GFP_KERNEL);
2091                 if (!filename) {
2092                         printk(KERN_ERR "%s: Out of memory whilst attempting "
2093                                "to kzalloc [%zd] bytes\n", __func__,
2094                                sizeof(*filename));
2095                         rc = -ENOMEM;
2096                         goto out;
2097                 }
2098                 filename->filename = (char *)name;
2099                 filename->filename_size = name_size;
2100                 rc = ecryptfs_encrypt_filename(filename, crypt_stat,
2101                                                mount_crypt_stat);
2102                 if (rc) {
2103                         printk(KERN_ERR "%s: Error attempting to encrypt "
2104                                "filename; rc = [%d]\n", __func__, rc);
2105                         kfree(filename);
2106                         goto out;
2107                 }
2108                 ecryptfs_encode_for_filename(
2109                         NULL, &encoded_name_no_prefix_size,
2110                         filename->encrypted_filename,
2111                         filename->encrypted_filename_size);
2112                 if ((crypt_stat && (crypt_stat->flags
2113                                     & ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
2114                     || (mount_crypt_stat
2115                         && (mount_crypt_stat->flags
2116                             & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK)))
2117                         (*encoded_name_size) =
2118                                 (ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE
2119                                  + encoded_name_no_prefix_size);
2120                 else
2121                         (*encoded_name_size) =
2122                                 (ECRYPTFS_FEK_ENCRYPTED_FILENAME_PREFIX_SIZE
2123                                  + encoded_name_no_prefix_size);
2124                 (*encoded_name) = kmalloc((*encoded_name_size) + 1, GFP_KERNEL);
2125                 if (!(*encoded_name)) {
2126                         printk(KERN_ERR "%s: Out of memory whilst attempting "
2127                                "to kzalloc [%zd] bytes\n", __func__,
2128                                (*encoded_name_size));
2129                         rc = -ENOMEM;
2130                         kfree(filename->encrypted_filename);
2131                         kfree(filename);
2132                         goto out;
2133                 }
2134                 if ((crypt_stat && (crypt_stat->flags
2135                                     & ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
2136                     || (mount_crypt_stat
2137                         && (mount_crypt_stat->flags
2138                             & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK))) {
2139                         memcpy((*encoded_name),
2140                                ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
2141                                ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE);
2142                         ecryptfs_encode_for_filename(
2143                             ((*encoded_name)
2144                              + ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE),
2145                             &encoded_name_no_prefix_size,
2146                             filename->encrypted_filename,
2147                             filename->encrypted_filename_size);
2148                         (*encoded_name_size) =
2149                                 (ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE
2150                                  + encoded_name_no_prefix_size);
2151                         (*encoded_name)[(*encoded_name_size)] = '\0';
2152                 } else {
2153                         rc = -EOPNOTSUPP;
2154                 }
2155                 if (rc) {
2156                         printk(KERN_ERR "%s: Error attempting to encode "
2157                                "encrypted filename; rc = [%d]\n", __func__,
2158                                rc);
2159                         kfree((*encoded_name));
2160                         (*encoded_name) = NULL;
2161                         (*encoded_name_size) = 0;
2162                 }
2163                 kfree(filename->encrypted_filename);
2164                 kfree(filename);
2165         } else {
2166                 rc = ecryptfs_copy_filename(encoded_name,
2167                                             encoded_name_size,
2168                                             name, name_size);
2169         }
2170 out:
2171         return rc;
2172 }
2173
2174 /**
2175  * ecryptfs_decode_and_decrypt_filename - converts the encoded cipher text name to decoded plaintext
2176  * @plaintext_name: The plaintext name
2177  * @plaintext_name_size: The plaintext name size
2178  * @ecryptfs_dir_dentry: eCryptfs directory dentry
2179  * @name: The filename in cipher text
2180  * @name_size: The cipher text name size
2181  *
2182  * Decrypts and decodes the filename.
2183  *
2184  * Returns zero on error; non-zero otherwise
2185  */
2186 int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
2187                                          size_t *plaintext_name_size,
2188                                          struct dentry *ecryptfs_dir_dentry,
2189                                          const char *name, size_t name_size)
2190 {
2191         struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
2192                 &ecryptfs_superblock_to_private(
2193                         ecryptfs_dir_dentry->d_sb)->mount_crypt_stat;
2194         char *decoded_name;
2195         size_t decoded_name_size;
2196         size_t packet_size;
2197         int rc = 0;
2198
2199         if ((mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)
2200             && !(mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
2201             && (name_size > ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE)
2202             && (strncmp(name, ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
2203                         ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE) == 0)) {
2204                 const char *orig_name = name;
2205                 size_t orig_name_size = name_size;
2206
2207                 name += ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
2208                 name_size -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
2209                 ecryptfs_decode_from_filename(NULL, &decoded_name_size,
2210                                               name, name_size);
2211                 decoded_name = kmalloc(decoded_name_size, GFP_KERNEL);
2212                 if (!decoded_name) {
2213                         printk(KERN_ERR "%s: Out of memory whilst attempting "
2214                                "to kmalloc [%zd] bytes\n", __func__,
2215                                decoded_name_size);
2216                         rc = -ENOMEM;
2217                         goto out;
2218                 }
2219                 ecryptfs_decode_from_filename(decoded_name, &decoded_name_size,
2220                                               name, name_size);
2221                 rc = ecryptfs_parse_tag_70_packet(plaintext_name,
2222                                                   plaintext_name_size,
2223                                                   &packet_size,
2224                                                   mount_crypt_stat,
2225                                                   decoded_name,
2226                                                   decoded_name_size);
2227                 if (rc) {
2228                         printk(KERN_INFO "%s: Could not parse tag 70 packet "
2229                                "from filename; copying through filename "
2230                                "as-is\n", __func__);
2231                         rc = ecryptfs_copy_filename(plaintext_name,
2232                                                     plaintext_name_size,
2233                                                     orig_name, orig_name_size);
2234                         goto out_free;
2235                 }
2236         } else {
2237                 rc = ecryptfs_copy_filename(plaintext_name,
2238                                             plaintext_name_size,
2239                                             name, name_size);
2240                 goto out;
2241         }
2242 out_free:
2243         kfree(decoded_name);
2244 out:
2245         return rc;
2246 }
2247
2248 #define ENC_NAME_MAX_BLOCKLEN_8_OR_16   143
2249
2250 int ecryptfs_set_f_namelen(long *namelen, long lower_namelen,
2251                            struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
2252 {
2253         struct blkcipher_desc desc;
2254         struct mutex *tfm_mutex;
2255         size_t cipher_blocksize;
2256         int rc;
2257
2258         if (!(mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
2259                 (*namelen) = lower_namelen;
2260                 return 0;
2261         }
2262
2263         rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(&desc.tfm, &tfm_mutex,
2264                         mount_crypt_stat->global_default_fn_cipher_name);
2265         if (unlikely(rc)) {
2266                 (*namelen) = 0;
2267                 return rc;
2268         }
2269
2270         mutex_lock(tfm_mutex);
2271         cipher_blocksize = crypto_blkcipher_blocksize(desc.tfm);
2272         mutex_unlock(tfm_mutex);
2273
2274         /* Return an exact amount for the common cases */
2275         if (lower_namelen == NAME_MAX
2276             && (cipher_blocksize == 8 || cipher_blocksize == 16)) {
2277                 (*namelen) = ENC_NAME_MAX_BLOCKLEN_8_OR_16;
2278                 return 0;
2279         }
2280
2281         /* Return a safe estimate for the uncommon cases */
2282         (*namelen) = lower_namelen;
2283         (*namelen) -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
2284         /* Since this is the max decoded size, subtract 1 "decoded block" len */
2285         (*namelen) = ecryptfs_max_decoded_size(*namelen) - 3;
2286         (*namelen) -= ECRYPTFS_TAG_70_MAX_METADATA_SIZE;
2287         (*namelen) -= ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES;
2288         /* Worst case is that the filename is padded nearly a full block size */
2289         (*namelen) -= cipher_blocksize - 1;
2290
2291         if ((*namelen) < 0)
2292                 (*namelen) = 0;
2293
2294         return 0;
2295 }