Pull battery into release branch
[linux-2.6] / 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 "ecryptfs_kernel.h"
37
38 static int
39 ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
40                              struct page *dst_page, int dst_offset,
41                              struct page *src_page, int src_offset, int size,
42                              unsigned char *iv);
43 static int
44 ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
45                              struct page *dst_page, int dst_offset,
46                              struct page *src_page, int src_offset, int size,
47                              unsigned char *iv);
48
49 /**
50  * ecryptfs_to_hex
51  * @dst: Buffer to take hex character representation of contents of
52  *       src; must be at least of size (src_size * 2)
53  * @src: Buffer to be converted to a hex string respresentation
54  * @src_size: number of bytes to convert
55  */
56 void ecryptfs_to_hex(char *dst, char *src, size_t src_size)
57 {
58         int x;
59
60         for (x = 0; x < src_size; x++)
61                 sprintf(&dst[x * 2], "%.2x", (unsigned char)src[x]);
62 }
63
64 /**
65  * ecryptfs_from_hex
66  * @dst: Buffer to take the bytes from src hex; must be at least of
67  *       size (src_size / 2)
68  * @src: Buffer to be converted from a hex string respresentation to raw value
69  * @dst_size: size of dst buffer, or number of hex characters pairs to convert
70  */
71 void ecryptfs_from_hex(char *dst, char *src, int dst_size)
72 {
73         int x;
74         char tmp[3] = { 0, };
75
76         for (x = 0; x < dst_size; x++) {
77                 tmp[0] = src[x * 2];
78                 tmp[1] = src[x * 2 + 1];
79                 dst[x] = (unsigned char)simple_strtol(tmp, NULL, 16);
80         }
81 }
82
83 /**
84  * ecryptfs_calculate_md5 - calculates the md5 of @src
85  * @dst: Pointer to 16 bytes of allocated memory
86  * @crypt_stat: Pointer to crypt_stat struct for the current inode
87  * @src: Data to be md5'd
88  * @len: Length of @src
89  *
90  * Uses the allocated crypto context that crypt_stat references to
91  * generate the MD5 sum of the contents of src.
92  */
93 static int ecryptfs_calculate_md5(char *dst,
94                                   struct ecryptfs_crypt_stat *crypt_stat,
95                                   char *src, int len)
96 {
97         struct scatterlist sg;
98         struct hash_desc desc = {
99                 .tfm = crypt_stat->hash_tfm,
100                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
101         };
102         int rc = 0;
103
104         mutex_lock(&crypt_stat->cs_hash_tfm_mutex);
105         sg_init_one(&sg, (u8 *)src, len);
106         if (!desc.tfm) {
107                 desc.tfm = crypto_alloc_hash(ECRYPTFS_DEFAULT_HASH, 0,
108                                              CRYPTO_ALG_ASYNC);
109                 if (IS_ERR(desc.tfm)) {
110                         rc = PTR_ERR(desc.tfm);
111                         ecryptfs_printk(KERN_ERR, "Error attempting to "
112                                         "allocate crypto context; rc = [%d]\n",
113                                         rc);
114                         goto out;
115                 }
116                 crypt_stat->hash_tfm = desc.tfm;
117         }
118         crypto_hash_init(&desc);
119         crypto_hash_update(&desc, &sg, len);
120         crypto_hash_final(&desc, dst);
121         mutex_unlock(&crypt_stat->cs_hash_tfm_mutex);
122 out:
123         return rc;
124 }
125
126 int ecryptfs_crypto_api_algify_cipher_name(char **algified_name,
127                                            char *cipher_name,
128                                            char *chaining_modifier)
129 {
130         int cipher_name_len = strlen(cipher_name);
131         int chaining_modifier_len = strlen(chaining_modifier);
132         int algified_name_len;
133         int rc;
134
135         algified_name_len = (chaining_modifier_len + cipher_name_len + 3);
136         (*algified_name) = kmalloc(algified_name_len, GFP_KERNEL);
137         if (!(*algified_name)) {
138                 rc = -ENOMEM;
139                 goto out;
140         }
141         snprintf((*algified_name), algified_name_len, "%s(%s)",
142                  chaining_modifier, cipher_name);
143         rc = 0;
144 out:
145         return rc;
146 }
147
148 /**
149  * ecryptfs_derive_iv
150  * @iv: destination for the derived iv vale
151  * @crypt_stat: Pointer to crypt_stat struct for the current inode
152  * @offset: Offset of the page whose's iv we are to derive
153  *
154  * Generate the initialization vector from the given root IV and page
155  * offset.
156  *
157  * Returns zero on success; non-zero on error.
158  */
159 static int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
160                               pgoff_t offset)
161 {
162         int rc = 0;
163         char dst[MD5_DIGEST_SIZE];
164         char src[ECRYPTFS_MAX_IV_BYTES + 16];
165
166         if (unlikely(ecryptfs_verbosity > 0)) {
167                 ecryptfs_printk(KERN_DEBUG, "root iv:\n");
168                 ecryptfs_dump_hex(crypt_stat->root_iv, crypt_stat->iv_bytes);
169         }
170         /* TODO: It is probably secure to just cast the least
171          * significant bits of the root IV into an unsigned long and
172          * add the offset to that rather than go through all this
173          * hashing business. -Halcrow */
174         memcpy(src, crypt_stat->root_iv, crypt_stat->iv_bytes);
175         memset((src + crypt_stat->iv_bytes), 0, 16);
176         snprintf((src + crypt_stat->iv_bytes), 16, "%ld", offset);
177         if (unlikely(ecryptfs_verbosity > 0)) {
178                 ecryptfs_printk(KERN_DEBUG, "source:\n");
179                 ecryptfs_dump_hex(src, (crypt_stat->iv_bytes + 16));
180         }
181         rc = ecryptfs_calculate_md5(dst, crypt_stat, src,
182                                     (crypt_stat->iv_bytes + 16));
183         if (rc) {
184                 ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
185                                 "MD5 while generating IV for a page\n");
186                 goto out;
187         }
188         memcpy(iv, dst, crypt_stat->iv_bytes);
189         if (unlikely(ecryptfs_verbosity > 0)) {
190                 ecryptfs_printk(KERN_DEBUG, "derived iv:\n");
191                 ecryptfs_dump_hex(iv, crypt_stat->iv_bytes);
192         }
193 out:
194         return rc;
195 }
196
197 /**
198  * ecryptfs_init_crypt_stat
199  * @crypt_stat: Pointer to the crypt_stat struct to initialize.
200  *
201  * Initialize the crypt_stat structure.
202  */
203 void
204 ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
205 {
206         memset((void *)crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
207         mutex_init(&crypt_stat->cs_mutex);
208         mutex_init(&crypt_stat->cs_tfm_mutex);
209         mutex_init(&crypt_stat->cs_hash_tfm_mutex);
210         crypt_stat->flags |= ECRYPTFS_STRUCT_INITIALIZED;
211 }
212
213 /**
214  * ecryptfs_destruct_crypt_stat
215  * @crypt_stat: Pointer to the crypt_stat struct to initialize.
216  *
217  * Releases all memory associated with a crypt_stat struct.
218  */
219 void ecryptfs_destruct_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
220 {
221         if (crypt_stat->tfm)
222                 crypto_free_blkcipher(crypt_stat->tfm);
223         if (crypt_stat->hash_tfm)
224                 crypto_free_hash(crypt_stat->hash_tfm);
225         memset(crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
226 }
227
228 void ecryptfs_destruct_mount_crypt_stat(
229         struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
230 {
231         if (mount_crypt_stat->global_auth_tok_key)
232                 key_put(mount_crypt_stat->global_auth_tok_key);
233         if (mount_crypt_stat->global_key_tfm)
234                 crypto_free_blkcipher(mount_crypt_stat->global_key_tfm);
235         memset(mount_crypt_stat, 0, sizeof(struct ecryptfs_mount_crypt_stat));
236 }
237
238 /**
239  * virt_to_scatterlist
240  * @addr: Virtual address
241  * @size: Size of data; should be an even multiple of the block size
242  * @sg: Pointer to scatterlist array; set to NULL to obtain only
243  *      the number of scatterlist structs required in array
244  * @sg_size: Max array size
245  *
246  * Fills in a scatterlist array with page references for a passed
247  * virtual address.
248  *
249  * Returns the number of scatterlist structs in array used
250  */
251 int virt_to_scatterlist(const void *addr, int size, struct scatterlist *sg,
252                         int sg_size)
253 {
254         int i = 0;
255         struct page *pg;
256         int offset;
257         int remainder_of_page;
258
259         while (size > 0 && i < sg_size) {
260                 pg = virt_to_page(addr);
261                 offset = offset_in_page(addr);
262                 if (sg) {
263                         sg[i].page = pg;
264                         sg[i].offset = offset;
265                 }
266                 remainder_of_page = PAGE_CACHE_SIZE - offset;
267                 if (size >= remainder_of_page) {
268                         if (sg)
269                                 sg[i].length = remainder_of_page;
270                         addr += remainder_of_page;
271                         size -= remainder_of_page;
272                 } else {
273                         if (sg)
274                                 sg[i].length = size;
275                         addr += size;
276                         size = 0;
277                 }
278                 i++;
279         }
280         if (size > 0)
281                 return -ENOMEM;
282         return i;
283 }
284
285 /**
286  * encrypt_scatterlist
287  * @crypt_stat: Pointer to the crypt_stat struct to initialize.
288  * @dest_sg: Destination of encrypted data
289  * @src_sg: Data to be encrypted
290  * @size: Length of data to be encrypted
291  * @iv: iv to use during encryption
292  *
293  * Returns the number of bytes encrypted; negative value on error
294  */
295 static int encrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
296                                struct scatterlist *dest_sg,
297                                struct scatterlist *src_sg, int size,
298                                unsigned char *iv)
299 {
300         struct blkcipher_desc desc = {
301                 .tfm = crypt_stat->tfm,
302                 .info = iv,
303                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
304         };
305         int rc = 0;
306
307         BUG_ON(!crypt_stat || !crypt_stat->tfm
308                || !(crypt_stat->flags & ECRYPTFS_STRUCT_INITIALIZED));
309         if (unlikely(ecryptfs_verbosity > 0)) {
310                 ecryptfs_printk(KERN_DEBUG, "Key size [%d]; key:\n",
311                                 crypt_stat->key_size);
312                 ecryptfs_dump_hex(crypt_stat->key,
313                                   crypt_stat->key_size);
314         }
315         /* Consider doing this once, when the file is opened */
316         mutex_lock(&crypt_stat->cs_tfm_mutex);
317         rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
318                                      crypt_stat->key_size);
319         if (rc) {
320                 ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
321                                 rc);
322                 mutex_unlock(&crypt_stat->cs_tfm_mutex);
323                 rc = -EINVAL;
324                 goto out;
325         }
326         ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes.\n", size);
327         crypto_blkcipher_encrypt_iv(&desc, dest_sg, src_sg, size);
328         mutex_unlock(&crypt_stat->cs_tfm_mutex);
329 out:
330         return rc;
331 }
332
333 static void
334 ecryptfs_extent_to_lwr_pg_idx_and_offset(unsigned long *lower_page_idx,
335                                          int *byte_offset,
336                                          struct ecryptfs_crypt_stat *crypt_stat,
337                                          unsigned long extent_num)
338 {
339         unsigned long lower_extent_num;
340         int extents_occupied_by_headers_at_front;
341         int bytes_occupied_by_headers_at_front;
342         int extent_offset;
343         int extents_per_page;
344
345         bytes_occupied_by_headers_at_front =
346                 ( crypt_stat->header_extent_size
347                   * crypt_stat->num_header_extents_at_front );
348         extents_occupied_by_headers_at_front =
349                 ( bytes_occupied_by_headers_at_front
350                   / crypt_stat->extent_size );
351         lower_extent_num = extents_occupied_by_headers_at_front + extent_num;
352         extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
353         (*lower_page_idx) = lower_extent_num / extents_per_page;
354         extent_offset = lower_extent_num % extents_per_page;
355         (*byte_offset) = extent_offset * crypt_stat->extent_size;
356         ecryptfs_printk(KERN_DEBUG, " * crypt_stat->header_extent_size = "
357                         "[%d]\n", crypt_stat->header_extent_size);
358         ecryptfs_printk(KERN_DEBUG, " * crypt_stat->"
359                         "num_header_extents_at_front = [%d]\n",
360                         crypt_stat->num_header_extents_at_front);
361         ecryptfs_printk(KERN_DEBUG, " * extents_occupied_by_headers_at_"
362                         "front = [%d]\n", extents_occupied_by_headers_at_front);
363         ecryptfs_printk(KERN_DEBUG, " * lower_extent_num = [0x%.16x]\n",
364                         lower_extent_num);
365         ecryptfs_printk(KERN_DEBUG, " * extents_per_page = [%d]\n",
366                         extents_per_page);
367         ecryptfs_printk(KERN_DEBUG, " * (*lower_page_idx) = [0x%.16x]\n",
368                         (*lower_page_idx));
369         ecryptfs_printk(KERN_DEBUG, " * extent_offset = [%d]\n",
370                         extent_offset);
371         ecryptfs_printk(KERN_DEBUG, " * (*byte_offset) = [%d]\n",
372                         (*byte_offset));
373 }
374
375 static int ecryptfs_write_out_page(struct ecryptfs_page_crypt_context *ctx,
376                                    struct page *lower_page,
377                                    struct inode *lower_inode,
378                                    int byte_offset_in_page, int bytes_to_write)
379 {
380         int rc = 0;
381
382         if (ctx->mode == ECRYPTFS_PREPARE_COMMIT_MODE) {
383                 rc = ecryptfs_commit_lower_page(lower_page, lower_inode,
384                                                 ctx->param.lower_file,
385                                                 byte_offset_in_page,
386                                                 bytes_to_write);
387                 if (rc) {
388                         ecryptfs_printk(KERN_ERR, "Error calling lower "
389                                         "commit; rc = [%d]\n", rc);
390                         goto out;
391                 }
392         } else {
393                 rc = ecryptfs_writepage_and_release_lower_page(lower_page,
394                                                                lower_inode,
395                                                                ctx->param.wbc);
396                 if (rc) {
397                         ecryptfs_printk(KERN_ERR, "Error calling lower "
398                                         "writepage(); rc = [%d]\n", rc);
399                         goto out;
400                 }
401         }
402 out:
403         return rc;
404 }
405
406 static int ecryptfs_read_in_page(struct ecryptfs_page_crypt_context *ctx,
407                                  struct page **lower_page,
408                                  struct inode *lower_inode,
409                                  unsigned long lower_page_idx,
410                                  int byte_offset_in_page)
411 {
412         int rc = 0;
413
414         if (ctx->mode == ECRYPTFS_PREPARE_COMMIT_MODE) {
415                 /* TODO: Limit this to only the data extents that are
416                  * needed */
417                 rc = ecryptfs_get_lower_page(lower_page, lower_inode,
418                                              ctx->param.lower_file,
419                                              lower_page_idx,
420                                              byte_offset_in_page,
421                                              (PAGE_CACHE_SIZE
422                                               - byte_offset_in_page));
423                 if (rc) {
424                         ecryptfs_printk(
425                                 KERN_ERR, "Error attempting to grab, map, "
426                                 "and prepare_write lower page with index "
427                                 "[0x%.16x]; rc = [%d]\n", lower_page_idx, rc);
428                         goto out;
429                 }
430         } else {
431                 *lower_page = grab_cache_page(lower_inode->i_mapping,
432                                               lower_page_idx);
433                 if (!(*lower_page)) {
434                         rc = -EINVAL;
435                         ecryptfs_printk(
436                                 KERN_ERR, "Error attempting to grab and map "
437                                 "lower page with index [0x%.16x]; rc = [%d]\n",
438                                 lower_page_idx, rc);
439                         goto out;
440                 }
441         }
442 out:
443         return rc;
444 }
445
446 /**
447  * ecryptfs_encrypt_page
448  * @ctx: The context of the page
449  *
450  * Encrypt an eCryptfs page. This is done on a per-extent basis. Note
451  * that eCryptfs pages may straddle the lower pages -- for instance,
452  * if the file was created on a machine with an 8K page size
453  * (resulting in an 8K header), and then the file is copied onto a
454  * host with a 32K page size, then when reading page 0 of the eCryptfs
455  * file, 24K of page 0 of the lower file will be read and decrypted,
456  * and then 8K of page 1 of the lower file will be read and decrypted.
457  *
458  * The actual operations performed on each page depends on the
459  * contents of the ecryptfs_page_crypt_context struct.
460  *
461  * Returns zero on success; negative on error
462  */
463 int ecryptfs_encrypt_page(struct ecryptfs_page_crypt_context *ctx)
464 {
465         char extent_iv[ECRYPTFS_MAX_IV_BYTES];
466         unsigned long base_extent;
467         unsigned long extent_offset = 0;
468         unsigned long lower_page_idx = 0;
469         unsigned long prior_lower_page_idx = 0;
470         struct page *lower_page;
471         struct inode *lower_inode;
472         struct ecryptfs_inode_info *inode_info;
473         struct ecryptfs_crypt_stat *crypt_stat;
474         int rc = 0;
475         int lower_byte_offset = 0;
476         int orig_byte_offset = 0;
477         int num_extents_per_page;
478 #define ECRYPTFS_PAGE_STATE_UNREAD    0
479 #define ECRYPTFS_PAGE_STATE_READ      1
480 #define ECRYPTFS_PAGE_STATE_MODIFIED  2
481 #define ECRYPTFS_PAGE_STATE_WRITTEN   3
482         int page_state;
483
484         lower_inode = ecryptfs_inode_to_lower(ctx->page->mapping->host);
485         inode_info = ecryptfs_inode_to_private(ctx->page->mapping->host);
486         crypt_stat = &inode_info->crypt_stat;
487         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
488                 rc = ecryptfs_copy_page_to_lower(ctx->page, lower_inode,
489                                                  ctx->param.lower_file);
490                 if (rc)
491                         ecryptfs_printk(KERN_ERR, "Error attempting to copy "
492                                         "page at index [0x%.16x]\n",
493                                         ctx->page->index);
494                 goto out;
495         }
496         num_extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
497         base_extent = (ctx->page->index * num_extents_per_page);
498         page_state = ECRYPTFS_PAGE_STATE_UNREAD;
499         while (extent_offset < num_extents_per_page) {
500                 ecryptfs_extent_to_lwr_pg_idx_and_offset(
501                         &lower_page_idx, &lower_byte_offset, crypt_stat,
502                         (base_extent + extent_offset));
503                 if (prior_lower_page_idx != lower_page_idx
504                     && page_state == ECRYPTFS_PAGE_STATE_MODIFIED) {
505                         rc = ecryptfs_write_out_page(ctx, lower_page,
506                                                      lower_inode,
507                                                      orig_byte_offset,
508                                                      (PAGE_CACHE_SIZE
509                                                       - orig_byte_offset));
510                         if (rc) {
511                                 ecryptfs_printk(KERN_ERR, "Error attempting "
512                                                 "to write out page; rc = [%d]"
513                                                 "\n", rc);
514                                 goto out;
515                         }
516                         page_state = ECRYPTFS_PAGE_STATE_WRITTEN;
517                 }
518                 if (page_state == ECRYPTFS_PAGE_STATE_UNREAD
519                     || page_state == ECRYPTFS_PAGE_STATE_WRITTEN) {
520                         rc = ecryptfs_read_in_page(ctx, &lower_page,
521                                                    lower_inode, lower_page_idx,
522                                                    lower_byte_offset);
523                         if (rc) {
524                                 ecryptfs_printk(KERN_ERR, "Error attempting "
525                                                 "to read in lower page with "
526                                                 "index [0x%.16x]; rc = [%d]\n",
527                                                 lower_page_idx, rc);
528                                 goto out;
529                         }
530                         orig_byte_offset = lower_byte_offset;
531                         prior_lower_page_idx = lower_page_idx;
532                         page_state = ECRYPTFS_PAGE_STATE_READ;
533                 }
534                 BUG_ON(!(page_state == ECRYPTFS_PAGE_STATE_MODIFIED
535                          || page_state == ECRYPTFS_PAGE_STATE_READ));
536                 rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
537                                         (base_extent + extent_offset));
538                 if (rc) {
539                         ecryptfs_printk(KERN_ERR, "Error attempting to "
540                                         "derive IV for extent [0x%.16x]; "
541                                         "rc = [%d]\n",
542                                         (base_extent + extent_offset), rc);
543                         goto out;
544                 }
545                 if (unlikely(ecryptfs_verbosity > 0)) {
546                         ecryptfs_printk(KERN_DEBUG, "Encrypting extent "
547                                         "with iv:\n");
548                         ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
549                         ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
550                                         "encryption:\n");
551                         ecryptfs_dump_hex((char *)
552                                           (page_address(ctx->page)
553                                            + (extent_offset
554                                               * crypt_stat->extent_size)), 8);
555                 }
556                 rc = ecryptfs_encrypt_page_offset(
557                         crypt_stat, lower_page, lower_byte_offset, ctx->page,
558                         (extent_offset * crypt_stat->extent_size),
559                         crypt_stat->extent_size, extent_iv);
560                 ecryptfs_printk(KERN_DEBUG, "Encrypt extent [0x%.16x]; "
561                                 "rc = [%d]\n",
562                                 (base_extent + extent_offset), rc);
563                 if (unlikely(ecryptfs_verbosity > 0)) {
564                         ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
565                                         "encryption:\n");
566                         ecryptfs_dump_hex((char *)(page_address(lower_page)
567                                                    + lower_byte_offset), 8);
568                 }
569                 page_state = ECRYPTFS_PAGE_STATE_MODIFIED;
570                 extent_offset++;
571         }
572         BUG_ON(orig_byte_offset != 0);
573         rc = ecryptfs_write_out_page(ctx, lower_page, lower_inode, 0,
574                                      (lower_byte_offset
575                                       + crypt_stat->extent_size));
576         if (rc) {
577                 ecryptfs_printk(KERN_ERR, "Error attempting to write out "
578                                 "page; rc = [%d]\n", rc);
579                                 goto out;
580         }
581 out:
582         return rc;
583 }
584
585 /**
586  * ecryptfs_decrypt_page
587  * @file: The ecryptfs file
588  * @page: The page in ecryptfs to decrypt
589  *
590  * Decrypt an eCryptfs page. This is done on a per-extent basis. Note
591  * that eCryptfs pages may straddle the lower pages -- for instance,
592  * if the file was created on a machine with an 8K page size
593  * (resulting in an 8K header), and then the file is copied onto a
594  * host with a 32K page size, then when reading page 0 of the eCryptfs
595  * file, 24K of page 0 of the lower file will be read and decrypted,
596  * and then 8K of page 1 of the lower file will be read and decrypted.
597  *
598  * Returns zero on success; negative on error
599  */
600 int ecryptfs_decrypt_page(struct file *file, struct page *page)
601 {
602         char extent_iv[ECRYPTFS_MAX_IV_BYTES];
603         unsigned long base_extent;
604         unsigned long extent_offset = 0;
605         unsigned long lower_page_idx = 0;
606         unsigned long prior_lower_page_idx = 0;
607         struct page *lower_page;
608         char *lower_page_virt = NULL;
609         struct inode *lower_inode;
610         struct ecryptfs_crypt_stat *crypt_stat;
611         int rc = 0;
612         int byte_offset;
613         int num_extents_per_page;
614         int page_state;
615
616         crypt_stat = &(ecryptfs_inode_to_private(
617                                page->mapping->host)->crypt_stat);
618         lower_inode = ecryptfs_inode_to_lower(page->mapping->host);
619         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
620                 rc = ecryptfs_do_readpage(file, page, page->index);
621                 if (rc)
622                         ecryptfs_printk(KERN_ERR, "Error attempting to copy "
623                                         "page at index [0x%.16x]\n",
624                                         page->index);
625                 goto out;
626         }
627         num_extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
628         base_extent = (page->index * num_extents_per_page);
629         lower_page_virt = kmem_cache_alloc(ecryptfs_lower_page_cache,
630                                            GFP_KERNEL);
631         if (!lower_page_virt) {
632                 rc = -ENOMEM;
633                 ecryptfs_printk(KERN_ERR, "Error getting page for encrypted "
634                                 "lower page(s)\n");
635                 goto out;
636         }
637         lower_page = virt_to_page(lower_page_virt);
638         page_state = ECRYPTFS_PAGE_STATE_UNREAD;
639         while (extent_offset < num_extents_per_page) {
640                 ecryptfs_extent_to_lwr_pg_idx_and_offset(
641                         &lower_page_idx, &byte_offset, crypt_stat,
642                         (base_extent + extent_offset));
643                 if (prior_lower_page_idx != lower_page_idx
644                     || page_state == ECRYPTFS_PAGE_STATE_UNREAD) {
645                         rc = ecryptfs_do_readpage(file, lower_page,
646                                                   lower_page_idx);
647                         if (rc) {
648                                 ecryptfs_printk(KERN_ERR, "Error reading "
649                                                 "lower encrypted page; rc = "
650                                                 "[%d]\n", rc);
651                                 goto out;
652                         }
653                         prior_lower_page_idx = lower_page_idx;
654                         page_state = ECRYPTFS_PAGE_STATE_READ;
655                 }
656                 rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
657                                         (base_extent + extent_offset));
658                 if (rc) {
659                         ecryptfs_printk(KERN_ERR, "Error attempting to "
660                                         "derive IV for extent [0x%.16x]; rc = "
661                                         "[%d]\n",
662                                         (base_extent + extent_offset), rc);
663                         goto out;
664                 }
665                 if (unlikely(ecryptfs_verbosity > 0)) {
666                         ecryptfs_printk(KERN_DEBUG, "Decrypting extent "
667                                         "with iv:\n");
668                         ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
669                         ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
670                                         "decryption:\n");
671                         ecryptfs_dump_hex((lower_page_virt + byte_offset), 8);
672                 }
673                 rc = ecryptfs_decrypt_page_offset(crypt_stat, page,
674                                                   (extent_offset
675                                                    * crypt_stat->extent_size),
676                                                   lower_page, byte_offset,
677                                                   crypt_stat->extent_size,
678                                                   extent_iv);
679                 if (rc != crypt_stat->extent_size) {
680                         ecryptfs_printk(KERN_ERR, "Error attempting to "
681                                         "decrypt extent [0x%.16x]\n",
682                                         (base_extent + extent_offset));
683                         goto out;
684                 }
685                 rc = 0;
686                 if (unlikely(ecryptfs_verbosity > 0)) {
687                         ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
688                                         "decryption:\n");
689                         ecryptfs_dump_hex((char *)(page_address(page)
690                                                    + byte_offset), 8);
691                 }
692                 extent_offset++;
693         }
694 out:
695         if (lower_page_virt)
696                 kmem_cache_free(ecryptfs_lower_page_cache, lower_page_virt);
697         return rc;
698 }
699
700 /**
701  * decrypt_scatterlist
702  *
703  * Returns the number of bytes decrypted; negative value on error
704  */
705 static int decrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
706                                struct scatterlist *dest_sg,
707                                struct scatterlist *src_sg, int size,
708                                unsigned char *iv)
709 {
710         struct blkcipher_desc desc = {
711                 .tfm = crypt_stat->tfm,
712                 .info = iv,
713                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP
714         };
715         int rc = 0;
716
717         /* Consider doing this once, when the file is opened */
718         mutex_lock(&crypt_stat->cs_tfm_mutex);
719         rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
720                                      crypt_stat->key_size);
721         if (rc) {
722                 ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
723                                 rc);
724                 mutex_unlock(&crypt_stat->cs_tfm_mutex);
725                 rc = -EINVAL;
726                 goto out;
727         }
728         ecryptfs_printk(KERN_DEBUG, "Decrypting [%d] bytes.\n", size);
729         rc = crypto_blkcipher_decrypt_iv(&desc, dest_sg, src_sg, size);
730         mutex_unlock(&crypt_stat->cs_tfm_mutex);
731         if (rc) {
732                 ecryptfs_printk(KERN_ERR, "Error decrypting; rc = [%d]\n",
733                                 rc);
734                 goto out;
735         }
736         rc = size;
737 out:
738         return rc;
739 }
740
741 /**
742  * ecryptfs_encrypt_page_offset
743  *
744  * Returns the number of bytes encrypted
745  */
746 static int
747 ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
748                              struct page *dst_page, int dst_offset,
749                              struct page *src_page, int src_offset, int size,
750                              unsigned char *iv)
751 {
752         struct scatterlist src_sg, dst_sg;
753
754         src_sg.page = src_page;
755         src_sg.offset = src_offset;
756         src_sg.length = size;
757         dst_sg.page = dst_page;
758         dst_sg.offset = dst_offset;
759         dst_sg.length = size;
760         return encrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
761 }
762
763 /**
764  * ecryptfs_decrypt_page_offset
765  *
766  * Returns the number of bytes decrypted
767  */
768 static int
769 ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
770                              struct page *dst_page, int dst_offset,
771                              struct page *src_page, int src_offset, int size,
772                              unsigned char *iv)
773 {
774         struct scatterlist src_sg, dst_sg;
775
776         src_sg.page = src_page;
777         src_sg.offset = src_offset;
778         src_sg.length = size;
779         dst_sg.page = dst_page;
780         dst_sg.offset = dst_offset;
781         dst_sg.length = size;
782         return decrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
783 }
784
785 #define ECRYPTFS_MAX_SCATTERLIST_LEN 4
786
787 /**
788  * ecryptfs_init_crypt_ctx
789  * @crypt_stat: Uninitilized crypt stats structure
790  *
791  * Initialize the crypto context.
792  *
793  * TODO: Performance: Keep a cache of initialized cipher contexts;
794  * only init if needed
795  */
796 int ecryptfs_init_crypt_ctx(struct ecryptfs_crypt_stat *crypt_stat)
797 {
798         char *full_alg_name;
799         int rc = -EINVAL;
800
801         if (!crypt_stat->cipher) {
802                 ecryptfs_printk(KERN_ERR, "No cipher specified\n");
803                 goto out;
804         }
805         ecryptfs_printk(KERN_DEBUG,
806                         "Initializing cipher [%s]; strlen = [%d]; "
807                         "key_size_bits = [%d]\n",
808                         crypt_stat->cipher, (int)strlen(crypt_stat->cipher),
809                         crypt_stat->key_size << 3);
810         if (crypt_stat->tfm) {
811                 rc = 0;
812                 goto out;
813         }
814         mutex_lock(&crypt_stat->cs_tfm_mutex);
815         rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
816                                                     crypt_stat->cipher, "cbc");
817         if (rc)
818                 goto out;
819         crypt_stat->tfm = crypto_alloc_blkcipher(full_alg_name, 0,
820                                                  CRYPTO_ALG_ASYNC);
821         kfree(full_alg_name);
822         if (IS_ERR(crypt_stat->tfm)) {
823                 rc = PTR_ERR(crypt_stat->tfm);
824                 ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
825                                 "Error initializing cipher [%s]\n",
826                                 crypt_stat->cipher);
827                 mutex_unlock(&crypt_stat->cs_tfm_mutex);
828                 goto out;
829         }
830         crypto_blkcipher_set_flags(crypt_stat->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
831         mutex_unlock(&crypt_stat->cs_tfm_mutex);
832         rc = 0;
833 out:
834         return rc;
835 }
836
837 static void set_extent_mask_and_shift(struct ecryptfs_crypt_stat *crypt_stat)
838 {
839         int extent_size_tmp;
840
841         crypt_stat->extent_mask = 0xFFFFFFFF;
842         crypt_stat->extent_shift = 0;
843         if (crypt_stat->extent_size == 0)
844                 return;
845         extent_size_tmp = crypt_stat->extent_size;
846         while ((extent_size_tmp & 0x01) == 0) {
847                 extent_size_tmp >>= 1;
848                 crypt_stat->extent_mask <<= 1;
849                 crypt_stat->extent_shift++;
850         }
851 }
852
853 void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat)
854 {
855         /* Default values; may be overwritten as we are parsing the
856          * packets. */
857         crypt_stat->extent_size = ECRYPTFS_DEFAULT_EXTENT_SIZE;
858         set_extent_mask_and_shift(crypt_stat);
859         crypt_stat->iv_bytes = ECRYPTFS_DEFAULT_IV_BYTES;
860         if (PAGE_CACHE_SIZE <= ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE) {
861                 crypt_stat->header_extent_size =
862                         ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
863         } else
864                 crypt_stat->header_extent_size = PAGE_CACHE_SIZE;
865         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
866                 crypt_stat->num_header_extents_at_front = 0;
867         else
868                 crypt_stat->num_header_extents_at_front = 1;
869 }
870
871 /**
872  * ecryptfs_compute_root_iv
873  * @crypt_stats
874  *
875  * On error, sets the root IV to all 0's.
876  */
877 int ecryptfs_compute_root_iv(struct ecryptfs_crypt_stat *crypt_stat)
878 {
879         int rc = 0;
880         char dst[MD5_DIGEST_SIZE];
881
882         BUG_ON(crypt_stat->iv_bytes > MD5_DIGEST_SIZE);
883         BUG_ON(crypt_stat->iv_bytes <= 0);
884         if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
885                 rc = -EINVAL;
886                 ecryptfs_printk(KERN_WARNING, "Session key not valid; "
887                                 "cannot generate root IV\n");
888                 goto out;
889         }
890         rc = ecryptfs_calculate_md5(dst, crypt_stat, crypt_stat->key,
891                                     crypt_stat->key_size);
892         if (rc) {
893                 ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
894                                 "MD5 while generating root IV\n");
895                 goto out;
896         }
897         memcpy(crypt_stat->root_iv, dst, crypt_stat->iv_bytes);
898 out:
899         if (rc) {
900                 memset(crypt_stat->root_iv, 0, crypt_stat->iv_bytes);
901                 crypt_stat->flags |= ECRYPTFS_SECURITY_WARNING;
902         }
903         return rc;
904 }
905
906 static void ecryptfs_generate_new_key(struct ecryptfs_crypt_stat *crypt_stat)
907 {
908         get_random_bytes(crypt_stat->key, crypt_stat->key_size);
909         crypt_stat->flags |= ECRYPTFS_KEY_VALID;
910         ecryptfs_compute_root_iv(crypt_stat);
911         if (unlikely(ecryptfs_verbosity > 0)) {
912                 ecryptfs_printk(KERN_DEBUG, "Generated new session key:\n");
913                 ecryptfs_dump_hex(crypt_stat->key,
914                                   crypt_stat->key_size);
915         }
916 }
917
918 /**
919  * ecryptfs_copy_mount_wide_flags_to_inode_flags
920  *
921  * This function propagates the mount-wide flags to individual inode
922  * flags.
923  */
924 static void ecryptfs_copy_mount_wide_flags_to_inode_flags(
925         struct ecryptfs_crypt_stat *crypt_stat,
926         struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
927 {
928         if (mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED)
929                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
930         if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
931                 crypt_stat->flags |= ECRYPTFS_VIEW_AS_ENCRYPTED;
932 }
933
934 /**
935  * ecryptfs_set_default_crypt_stat_vals
936  * @crypt_stat
937  *
938  * Default values in the event that policy does not override them.
939  */
940 static void ecryptfs_set_default_crypt_stat_vals(
941         struct ecryptfs_crypt_stat *crypt_stat,
942         struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
943 {
944         ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
945                                                       mount_crypt_stat);
946         ecryptfs_set_default_sizes(crypt_stat);
947         strcpy(crypt_stat->cipher, ECRYPTFS_DEFAULT_CIPHER);
948         crypt_stat->key_size = ECRYPTFS_DEFAULT_KEY_BYTES;
949         crypt_stat->flags &= ~(ECRYPTFS_KEY_VALID);
950         crypt_stat->file_version = ECRYPTFS_FILE_VERSION;
951         crypt_stat->mount_crypt_stat = mount_crypt_stat;
952 }
953
954 /**
955  * ecryptfs_new_file_context
956  * @ecryptfs_dentry
957  *
958  * If the crypto context for the file has not yet been established,
959  * this is where we do that.  Establishing a new crypto context
960  * involves the following decisions:
961  *  - What cipher to use?
962  *  - What set of authentication tokens to use?
963  * Here we just worry about getting enough information into the
964  * authentication tokens so that we know that they are available.
965  * We associate the available authentication tokens with the new file
966  * via the set of signatures in the crypt_stat struct.  Later, when
967  * the headers are actually written out, we may again defer to
968  * userspace to perform the encryption of the session key; for the
969  * foreseeable future, this will be the case with public key packets.
970  *
971  * Returns zero on success; non-zero otherwise
972  */
973 /* Associate an authentication token(s) with the file */
974 int ecryptfs_new_file_context(struct dentry *ecryptfs_dentry)
975 {
976         int rc = 0;
977         struct ecryptfs_crypt_stat *crypt_stat =
978             &ecryptfs_inode_to_private(ecryptfs_dentry->d_inode)->crypt_stat;
979         struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
980             &ecryptfs_superblock_to_private(
981                     ecryptfs_dentry->d_sb)->mount_crypt_stat;
982         int cipher_name_len;
983
984         ecryptfs_set_default_crypt_stat_vals(crypt_stat, mount_crypt_stat);
985         /* See if there are mount crypt options */
986         if (mount_crypt_stat->global_auth_tok) {
987                 ecryptfs_printk(KERN_DEBUG, "Initializing context for new "
988                                 "file using mount_crypt_stat\n");
989                 crypt_stat->flags |= ECRYPTFS_ENCRYPTED;
990                 crypt_stat->flags |= ECRYPTFS_KEY_VALID;
991                 ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
992                                                               mount_crypt_stat);
993                 memcpy(crypt_stat->keysigs[crypt_stat->num_keysigs++],
994                        mount_crypt_stat->global_auth_tok_sig,
995                        ECRYPTFS_SIG_SIZE_HEX);
996                 cipher_name_len =
997                     strlen(mount_crypt_stat->global_default_cipher_name);
998                 memcpy(crypt_stat->cipher,
999                        mount_crypt_stat->global_default_cipher_name,
1000                        cipher_name_len);
1001                 crypt_stat->cipher[cipher_name_len] = '\0';
1002                 crypt_stat->key_size =
1003                         mount_crypt_stat->global_default_cipher_key_size;
1004                 ecryptfs_generate_new_key(crypt_stat);
1005         } else
1006                 /* We should not encounter this scenario since we
1007                  * should detect lack of global_auth_tok at mount time
1008                  * TODO: Applies to 0.1 release only; remove in future
1009                  * release */
1010                 BUG();
1011         rc = ecryptfs_init_crypt_ctx(crypt_stat);
1012         if (rc)
1013                 ecryptfs_printk(KERN_ERR, "Error initializing cryptographic "
1014                                 "context for cipher [%s]: rc = [%d]\n",
1015                                 crypt_stat->cipher, rc);
1016         return rc;
1017 }
1018
1019 /**
1020  * contains_ecryptfs_marker - check for the ecryptfs marker
1021  * @data: The data block in which to check
1022  *
1023  * Returns one if marker found; zero if not found
1024  */
1025 static int contains_ecryptfs_marker(char *data)
1026 {
1027         u32 m_1, m_2;
1028
1029         memcpy(&m_1, data, 4);
1030         m_1 = be32_to_cpu(m_1);
1031         memcpy(&m_2, (data + 4), 4);
1032         m_2 = be32_to_cpu(m_2);
1033         if ((m_1 ^ MAGIC_ECRYPTFS_MARKER) == m_2)
1034                 return 1;
1035         ecryptfs_printk(KERN_DEBUG, "m_1 = [0x%.8x]; m_2 = [0x%.8x]; "
1036                         "MAGIC_ECRYPTFS_MARKER = [0x%.8x]\n", m_1, m_2,
1037                         MAGIC_ECRYPTFS_MARKER);
1038         ecryptfs_printk(KERN_DEBUG, "(m_1 ^ MAGIC_ECRYPTFS_MARKER) = "
1039                         "[0x%.8x]\n", (m_1 ^ MAGIC_ECRYPTFS_MARKER));
1040         return 0;
1041 }
1042
1043 struct ecryptfs_flag_map_elem {
1044         u32 file_flag;
1045         u32 local_flag;
1046 };
1047
1048 /* Add support for additional flags by adding elements here. */
1049 static struct ecryptfs_flag_map_elem ecryptfs_flag_map[] = {
1050         {0x00000001, ECRYPTFS_ENABLE_HMAC},
1051         {0x00000002, ECRYPTFS_ENCRYPTED},
1052         {0x00000004, ECRYPTFS_METADATA_IN_XATTR}
1053 };
1054
1055 /**
1056  * ecryptfs_process_flags
1057  * @crypt_stat
1058  * @page_virt: Source data to be parsed
1059  * @bytes_read: Updated with the number of bytes read
1060  *
1061  * Returns zero on success; non-zero if the flag set is invalid
1062  */
1063 static int ecryptfs_process_flags(struct ecryptfs_crypt_stat *crypt_stat,
1064                                   char *page_virt, int *bytes_read)
1065 {
1066         int rc = 0;
1067         int i;
1068         u32 flags;
1069
1070         memcpy(&flags, page_virt, 4);
1071         flags = be32_to_cpu(flags);
1072         for (i = 0; i < ((sizeof(ecryptfs_flag_map)
1073                           / sizeof(struct ecryptfs_flag_map_elem))); i++)
1074                 if (flags & ecryptfs_flag_map[i].file_flag) {
1075                         crypt_stat->flags |= ecryptfs_flag_map[i].local_flag;
1076                 } else
1077                         crypt_stat->flags &= ~(ecryptfs_flag_map[i].local_flag);
1078         /* Version is in top 8 bits of the 32-bit flag vector */
1079         crypt_stat->file_version = ((flags >> 24) & 0xFF);
1080         (*bytes_read) = 4;
1081         return rc;
1082 }
1083
1084 /**
1085  * write_ecryptfs_marker
1086  * @page_virt: The pointer to in a page to begin writing the marker
1087  * @written: Number of bytes written
1088  *
1089  * Marker = 0x3c81b7f5
1090  */
1091 static void write_ecryptfs_marker(char *page_virt, size_t *written)
1092 {
1093         u32 m_1, m_2;
1094
1095         get_random_bytes(&m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
1096         m_2 = (m_1 ^ MAGIC_ECRYPTFS_MARKER);
1097         m_1 = cpu_to_be32(m_1);
1098         memcpy(page_virt, &m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
1099         m_2 = cpu_to_be32(m_2);
1100         memcpy(page_virt + (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2), &m_2,
1101                (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
1102         (*written) = MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
1103 }
1104
1105 static void
1106 write_ecryptfs_flags(char *page_virt, struct ecryptfs_crypt_stat *crypt_stat,
1107                      size_t *written)
1108 {
1109         u32 flags = 0;
1110         int i;
1111
1112         for (i = 0; i < ((sizeof(ecryptfs_flag_map)
1113                           / sizeof(struct ecryptfs_flag_map_elem))); i++)
1114                 if (crypt_stat->flags & ecryptfs_flag_map[i].local_flag)
1115                         flags |= ecryptfs_flag_map[i].file_flag;
1116         /* Version is in top 8 bits of the 32-bit flag vector */
1117         flags |= ((((u8)crypt_stat->file_version) << 24) & 0xFF000000);
1118         flags = cpu_to_be32(flags);
1119         memcpy(page_virt, &flags, 4);
1120         (*written) = 4;
1121 }
1122
1123 struct ecryptfs_cipher_code_str_map_elem {
1124         char cipher_str[16];
1125         u16 cipher_code;
1126 };
1127
1128 /* Add support for additional ciphers by adding elements here. The
1129  * cipher_code is whatever OpenPGP applicatoins use to identify the
1130  * ciphers. List in order of probability. */
1131 static struct ecryptfs_cipher_code_str_map_elem
1132 ecryptfs_cipher_code_str_map[] = {
1133         {"aes",RFC2440_CIPHER_AES_128 },
1134         {"blowfish", RFC2440_CIPHER_BLOWFISH},
1135         {"des3_ede", RFC2440_CIPHER_DES3_EDE},
1136         {"cast5", RFC2440_CIPHER_CAST_5},
1137         {"twofish", RFC2440_CIPHER_TWOFISH},
1138         {"cast6", RFC2440_CIPHER_CAST_6},
1139         {"aes", RFC2440_CIPHER_AES_192},
1140         {"aes", RFC2440_CIPHER_AES_256}
1141 };
1142
1143 /**
1144  * ecryptfs_code_for_cipher_string
1145  * @str: The string representing the cipher name
1146  *
1147  * Returns zero on no match, or the cipher code on match
1148  */
1149 u16 ecryptfs_code_for_cipher_string(struct ecryptfs_crypt_stat *crypt_stat)
1150 {
1151         int i;
1152         u16 code = 0;
1153         struct ecryptfs_cipher_code_str_map_elem *map =
1154                 ecryptfs_cipher_code_str_map;
1155
1156         if (strcmp(crypt_stat->cipher, "aes") == 0) {
1157                 switch (crypt_stat->key_size) {
1158                 case 16:
1159                         code = RFC2440_CIPHER_AES_128;
1160                         break;
1161                 case 24:
1162                         code = RFC2440_CIPHER_AES_192;
1163                         break;
1164                 case 32:
1165                         code = RFC2440_CIPHER_AES_256;
1166                 }
1167         } else {
1168                 for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
1169                         if (strcmp(crypt_stat->cipher, map[i].cipher_str) == 0){
1170                                 code = map[i].cipher_code;
1171                                 break;
1172                         }
1173         }
1174         return code;
1175 }
1176
1177 /**
1178  * ecryptfs_cipher_code_to_string
1179  * @str: Destination to write out the cipher name
1180  * @cipher_code: The code to convert to cipher name string
1181  *
1182  * Returns zero on success
1183  */
1184 int ecryptfs_cipher_code_to_string(char *str, u16 cipher_code)
1185 {
1186         int rc = 0;
1187         int i;
1188
1189         str[0] = '\0';
1190         for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
1191                 if (cipher_code == ecryptfs_cipher_code_str_map[i].cipher_code)
1192                         strcpy(str, ecryptfs_cipher_code_str_map[i].cipher_str);
1193         if (str[0] == '\0') {
1194                 ecryptfs_printk(KERN_WARNING, "Cipher code not recognized: "
1195                                 "[%d]\n", cipher_code);
1196                 rc = -EINVAL;
1197         }
1198         return rc;
1199 }
1200
1201 /**
1202  * ecryptfs_read_header_region
1203  * @data
1204  * @dentry
1205  * @nd
1206  *
1207  * Returns zero on success; non-zero otherwise
1208  */
1209 static int ecryptfs_read_header_region(char *data, struct dentry *dentry,
1210                                        struct vfsmount *mnt)
1211 {
1212         struct file *lower_file;
1213         mm_segment_t oldfs;
1214         int rc;
1215
1216         if ((rc = ecryptfs_open_lower_file(&lower_file, dentry, mnt,
1217                                            O_RDONLY))) {
1218                 printk(KERN_ERR
1219                        "Error opening lower_file to read header region\n");
1220                 goto out;
1221         }
1222         lower_file->f_pos = 0;
1223         oldfs = get_fs();
1224         set_fs(get_ds());
1225         /* For releases 0.1 and 0.2, all of the header information
1226          * fits in the first data extent-sized region. */
1227         rc = lower_file->f_op->read(lower_file, (char __user *)data,
1228                               ECRYPTFS_DEFAULT_EXTENT_SIZE, &lower_file->f_pos);
1229         set_fs(oldfs);
1230         if ((rc = ecryptfs_close_lower_file(lower_file))) {
1231                 printk(KERN_ERR "Error closing lower_file\n");
1232                 goto out;
1233         }
1234         rc = 0;
1235 out:
1236         return rc;
1237 }
1238
1239 int ecryptfs_read_and_validate_header_region(char *data, struct dentry *dentry,
1240                                              struct vfsmount *mnt)
1241 {
1242         int rc;
1243
1244         rc = ecryptfs_read_header_region(data, dentry, mnt);
1245         if (rc)
1246                 goto out;
1247         if (!contains_ecryptfs_marker(data + ECRYPTFS_FILE_SIZE_BYTES))
1248                 rc = -EINVAL;
1249 out:
1250         return rc;
1251 }
1252
1253
1254 void
1255 ecryptfs_write_header_metadata(char *virt,
1256                                struct ecryptfs_crypt_stat *crypt_stat,
1257                                size_t *written)
1258 {
1259         u32 header_extent_size;
1260         u16 num_header_extents_at_front;
1261
1262         header_extent_size = (u32)crypt_stat->header_extent_size;
1263         num_header_extents_at_front =
1264                 (u16)crypt_stat->num_header_extents_at_front;
1265         header_extent_size = cpu_to_be32(header_extent_size);
1266         memcpy(virt, &header_extent_size, 4);
1267         virt += 4;
1268         num_header_extents_at_front = cpu_to_be16(num_header_extents_at_front);
1269         memcpy(virt, &num_header_extents_at_front, 2);
1270         (*written) = 6;
1271 }
1272
1273 struct kmem_cache *ecryptfs_header_cache_0;
1274 struct kmem_cache *ecryptfs_header_cache_1;
1275 struct kmem_cache *ecryptfs_header_cache_2;
1276
1277 /**
1278  * ecryptfs_write_headers_virt
1279  * @page_virt
1280  * @crypt_stat
1281  * @ecryptfs_dentry
1282  *
1283  * Format version: 1
1284  *
1285  *   Header Extent:
1286  *     Octets 0-7:        Unencrypted file size (big-endian)
1287  *     Octets 8-15:       eCryptfs special marker
1288  *     Octets 16-19:      Flags
1289  *      Octet 16:         File format version number (between 0 and 255)
1290  *      Octets 17-18:     Reserved
1291  *      Octet 19:         Bit 1 (lsb): Reserved
1292  *                        Bit 2: Encrypted?
1293  *                        Bits 3-8: Reserved
1294  *     Octets 20-23:      Header extent size (big-endian)
1295  *     Octets 24-25:      Number of header extents at front of file
1296  *                        (big-endian)
1297  *     Octet  26:         Begin RFC 2440 authentication token packet set
1298  *   Data Extent 0:
1299  *     Lower data (CBC encrypted)
1300  *   Data Extent 1:
1301  *     Lower data (CBC encrypted)
1302  *   ...
1303  *
1304  * Returns zero on success
1305  */
1306 static int ecryptfs_write_headers_virt(char *page_virt, size_t *size,
1307                                        struct ecryptfs_crypt_stat *crypt_stat,
1308                                        struct dentry *ecryptfs_dentry)
1309 {
1310         int rc;
1311         size_t written;
1312         size_t offset;
1313
1314         offset = ECRYPTFS_FILE_SIZE_BYTES;
1315         write_ecryptfs_marker((page_virt + offset), &written);
1316         offset += written;
1317         write_ecryptfs_flags((page_virt + offset), crypt_stat, &written);
1318         offset += written;
1319         ecryptfs_write_header_metadata((page_virt + offset), crypt_stat,
1320                                        &written);
1321         offset += written;
1322         rc = ecryptfs_generate_key_packet_set((page_virt + offset), crypt_stat,
1323                                               ecryptfs_dentry, &written,
1324                                               PAGE_CACHE_SIZE - offset);
1325         if (rc)
1326                 ecryptfs_printk(KERN_WARNING, "Error generating key packet "
1327                                 "set; rc = [%d]\n", rc);
1328         if (size) {
1329                 offset += written;
1330                 *size = offset;
1331         }
1332         return rc;
1333 }
1334
1335 static int ecryptfs_write_metadata_to_contents(struct ecryptfs_crypt_stat *crypt_stat,
1336                                                struct file *lower_file,
1337                                                char *page_virt)
1338 {
1339         mm_segment_t oldfs;
1340         int current_header_page;
1341         int header_pages;
1342         ssize_t size;
1343         int rc = 0;
1344
1345         lower_file->f_pos = 0;
1346         oldfs = get_fs();
1347         set_fs(get_ds());
1348         size = vfs_write(lower_file, (char __user *)page_virt, PAGE_CACHE_SIZE,
1349                          &lower_file->f_pos);
1350         if (size < 0) {
1351                 rc = (int)size;
1352                 printk(KERN_ERR "Error attempting to write lower page; "
1353                        "rc = [%d]\n", rc);
1354                 set_fs(oldfs);
1355                 goto out;
1356         }
1357         header_pages = ((crypt_stat->header_extent_size
1358                          * crypt_stat->num_header_extents_at_front)
1359                         / PAGE_CACHE_SIZE);
1360         memset(page_virt, 0, PAGE_CACHE_SIZE);
1361         current_header_page = 1;
1362         while (current_header_page < header_pages) {
1363                 size = vfs_write(lower_file, (char __user *)page_virt,
1364                                  PAGE_CACHE_SIZE, &lower_file->f_pos);
1365                 if (size < 0) {
1366                         rc = (int)size;
1367                         printk(KERN_ERR "Error attempting to write lower page; "
1368                                "rc = [%d]\n", rc);
1369                         set_fs(oldfs);
1370                         goto out;
1371                 }
1372                 current_header_page++;
1373         }
1374         set_fs(oldfs);
1375 out:
1376         return rc;
1377 }
1378
1379 static int ecryptfs_write_metadata_to_xattr(struct dentry *ecryptfs_dentry,
1380                                             struct ecryptfs_crypt_stat *crypt_stat,
1381                                             char *page_virt, size_t size)
1382 {
1383         int rc;
1384
1385         rc = ecryptfs_setxattr(ecryptfs_dentry, ECRYPTFS_XATTR_NAME, page_virt,
1386                                size, 0);
1387         return rc;
1388 }
1389
1390 /**
1391  * ecryptfs_write_metadata
1392  * @lower_file: The lower file struct, which was returned from dentry_open
1393  *
1394  * Write the file headers out.  This will likely involve a userspace
1395  * callout, in which the session key is encrypted with one or more
1396  * public keys and/or the passphrase necessary to do the encryption is
1397  * retrieved via a prompt.  Exactly what happens at this point should
1398  * be policy-dependent.
1399  *
1400  * Returns zero on success; non-zero on error
1401  */
1402 int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry,
1403                             struct file *lower_file)
1404 {
1405         struct ecryptfs_crypt_stat *crypt_stat;
1406         char *page_virt;
1407         size_t size;
1408         int rc = 0;
1409
1410         crypt_stat = &ecryptfs_inode_to_private(
1411                 ecryptfs_dentry->d_inode)->crypt_stat;
1412         if (likely(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
1413                 if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
1414                         ecryptfs_printk(KERN_DEBUG, "Key is "
1415                                         "invalid; bailing out\n");
1416                         rc = -EINVAL;
1417                         goto out;
1418                 }
1419         } else {
1420                 rc = -EINVAL;
1421                 ecryptfs_printk(KERN_WARNING,
1422                                 "Called with crypt_stat->encrypted == 0\n");
1423                 goto out;
1424         }
1425         /* Released in this function */
1426         page_virt = kmem_cache_zalloc(ecryptfs_header_cache_0, GFP_USER);
1427         if (!page_virt) {
1428                 ecryptfs_printk(KERN_ERR, "Out of memory\n");
1429                 rc = -ENOMEM;
1430                 goto out;
1431         }
1432         rc = ecryptfs_write_headers_virt(page_virt, &size, crypt_stat,
1433                                          ecryptfs_dentry);
1434         if (unlikely(rc)) {
1435                 ecryptfs_printk(KERN_ERR, "Error whilst writing headers\n");
1436                 memset(page_virt, 0, PAGE_CACHE_SIZE);
1437                 goto out_free;
1438         }
1439         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
1440                 rc = ecryptfs_write_metadata_to_xattr(ecryptfs_dentry,
1441                                                       crypt_stat, page_virt,
1442                                                       size);
1443         else
1444                 rc = ecryptfs_write_metadata_to_contents(crypt_stat, lower_file,
1445                                                          page_virt);
1446         if (rc) {
1447                 printk(KERN_ERR "Error writing metadata out to lower file; "
1448                        "rc = [%d]\n", rc);
1449                 goto out_free;
1450         }
1451 out_free:
1452         kmem_cache_free(ecryptfs_header_cache_0, page_virt);
1453 out:
1454         return rc;
1455 }
1456
1457 #define ECRYPTFS_DONT_VALIDATE_HEADER_SIZE 0
1458 #define ECRYPTFS_VALIDATE_HEADER_SIZE 1
1459 static int parse_header_metadata(struct ecryptfs_crypt_stat *crypt_stat,
1460                                  char *virt, int *bytes_read,
1461                                  int validate_header_size)
1462 {
1463         int rc = 0;
1464         u32 header_extent_size;
1465         u16 num_header_extents_at_front;
1466
1467         memcpy(&header_extent_size, virt, 4);
1468         header_extent_size = be32_to_cpu(header_extent_size);
1469         virt += 4;
1470         memcpy(&num_header_extents_at_front, virt, 2);
1471         num_header_extents_at_front = be16_to_cpu(num_header_extents_at_front);
1472         crypt_stat->header_extent_size = (int)header_extent_size;
1473         crypt_stat->num_header_extents_at_front =
1474                 (int)num_header_extents_at_front;
1475         (*bytes_read) = 6;
1476         if ((validate_header_size == ECRYPTFS_VALIDATE_HEADER_SIZE)
1477             && ((crypt_stat->header_extent_size
1478                  * crypt_stat->num_header_extents_at_front)
1479                 < ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)) {
1480                 rc = -EINVAL;
1481                 ecryptfs_printk(KERN_WARNING, "Invalid header extent size: "
1482                                 "[%d]\n", crypt_stat->header_extent_size);
1483         }
1484         return rc;
1485 }
1486
1487 /**
1488  * set_default_header_data
1489  *
1490  * For version 0 file format; this function is only for backwards
1491  * compatibility for files created with the prior versions of
1492  * eCryptfs.
1493  */
1494 static void set_default_header_data(struct ecryptfs_crypt_stat *crypt_stat)
1495 {
1496         crypt_stat->header_extent_size = 4096;
1497         crypt_stat->num_header_extents_at_front = 1;
1498 }
1499
1500 /**
1501  * ecryptfs_read_headers_virt
1502  *
1503  * Read/parse the header data. The header format is detailed in the
1504  * comment block for the ecryptfs_write_headers_virt() function.
1505  *
1506  * Returns zero on success
1507  */
1508 static int ecryptfs_read_headers_virt(char *page_virt,
1509                                       struct ecryptfs_crypt_stat *crypt_stat,
1510                                       struct dentry *ecryptfs_dentry,
1511                                       int validate_header_size)
1512 {
1513         int rc = 0;
1514         int offset;
1515         int bytes_read;
1516
1517         ecryptfs_set_default_sizes(crypt_stat);
1518         crypt_stat->mount_crypt_stat = &ecryptfs_superblock_to_private(
1519                 ecryptfs_dentry->d_sb)->mount_crypt_stat;
1520         offset = ECRYPTFS_FILE_SIZE_BYTES;
1521         rc = contains_ecryptfs_marker(page_virt + offset);
1522         if (rc == 0) {
1523                 rc = -EINVAL;
1524                 goto out;
1525         }
1526         offset += MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
1527         rc = ecryptfs_process_flags(crypt_stat, (page_virt + offset),
1528                                     &bytes_read);
1529         if (rc) {
1530                 ecryptfs_printk(KERN_WARNING, "Error processing flags\n");
1531                 goto out;
1532         }
1533         if (crypt_stat->file_version > ECRYPTFS_SUPPORTED_FILE_VERSION) {
1534                 ecryptfs_printk(KERN_WARNING, "File version is [%d]; only "
1535                                 "file version [%d] is supported by this "
1536                                 "version of eCryptfs\n",
1537                                 crypt_stat->file_version,
1538                                 ECRYPTFS_SUPPORTED_FILE_VERSION);
1539                 rc = -EINVAL;
1540                 goto out;
1541         }
1542         offset += bytes_read;
1543         if (crypt_stat->file_version >= 1) {
1544                 rc = parse_header_metadata(crypt_stat, (page_virt + offset),
1545                                            &bytes_read, validate_header_size);
1546                 if (rc) {
1547                         ecryptfs_printk(KERN_WARNING, "Error reading header "
1548                                         "metadata; rc = [%d]\n", rc);
1549                 }
1550                 offset += bytes_read;
1551         } else
1552                 set_default_header_data(crypt_stat);
1553         rc = ecryptfs_parse_packet_set(crypt_stat, (page_virt + offset),
1554                                        ecryptfs_dentry);
1555 out:
1556         return rc;
1557 }
1558
1559 /**
1560  * ecryptfs_read_xattr_region
1561  *
1562  * Attempts to read the crypto metadata from the extended attribute
1563  * region of the lower file.
1564  */
1565 int ecryptfs_read_xattr_region(char *page_virt, struct dentry *ecryptfs_dentry)
1566 {
1567         ssize_t size;
1568         int rc = 0;
1569
1570         size = ecryptfs_getxattr(ecryptfs_dentry, ECRYPTFS_XATTR_NAME,
1571                                  page_virt, ECRYPTFS_DEFAULT_EXTENT_SIZE);
1572         if (size < 0) {
1573                 printk(KERN_DEBUG "Error attempting to read the [%s] "
1574                        "xattr from the lower file; return value = [%zd]\n",
1575                        ECRYPTFS_XATTR_NAME, size);
1576                 rc = -EINVAL;
1577                 goto out;
1578         }
1579 out:
1580         return rc;
1581 }
1582
1583 int ecryptfs_read_and_validate_xattr_region(char *page_virt,
1584                                             struct dentry *ecryptfs_dentry)
1585 {
1586         int rc;
1587
1588         rc = ecryptfs_read_xattr_region(page_virt, ecryptfs_dentry);
1589         if (rc)
1590                 goto out;
1591         if (!contains_ecryptfs_marker(page_virt + ECRYPTFS_FILE_SIZE_BYTES)) {
1592                 printk(KERN_WARNING "Valid data found in [%s] xattr, but "
1593                         "the marker is invalid\n", ECRYPTFS_XATTR_NAME);
1594                 rc = -EINVAL;
1595         }
1596 out:
1597         return rc;
1598 }
1599
1600 /**
1601  * ecryptfs_read_metadata
1602  *
1603  * Common entry point for reading file metadata. From here, we could
1604  * retrieve the header information from the header region of the file,
1605  * the xattr region of the file, or some other repostory that is
1606  * stored separately from the file itself. The current implementation
1607  * supports retrieving the metadata information from the file contents
1608  * and from the xattr region.
1609  *
1610  * Returns zero if valid headers found and parsed; non-zero otherwise
1611  */
1612 int ecryptfs_read_metadata(struct dentry *ecryptfs_dentry,
1613                            struct file *lower_file)
1614 {
1615         int rc = 0;
1616         char *page_virt = NULL;
1617         mm_segment_t oldfs;
1618         ssize_t bytes_read;
1619         struct ecryptfs_crypt_stat *crypt_stat =
1620             &ecryptfs_inode_to_private(ecryptfs_dentry->d_inode)->crypt_stat;
1621         struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
1622                 &ecryptfs_superblock_to_private(
1623                         ecryptfs_dentry->d_sb)->mount_crypt_stat;
1624
1625         ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
1626                                                       mount_crypt_stat);
1627         /* Read the first page from the underlying file */
1628         page_virt = kmem_cache_alloc(ecryptfs_header_cache_1, GFP_USER);
1629         if (!page_virt) {
1630                 rc = -ENOMEM;
1631                 ecryptfs_printk(KERN_ERR, "Unable to allocate page_virt\n");
1632                 goto out;
1633         }
1634         lower_file->f_pos = 0;
1635         oldfs = get_fs();
1636         set_fs(get_ds());
1637         bytes_read = lower_file->f_op->read(lower_file,
1638                                             (char __user *)page_virt,
1639                                             ECRYPTFS_DEFAULT_EXTENT_SIZE,
1640                                             &lower_file->f_pos);
1641         set_fs(oldfs);
1642         if (bytes_read != ECRYPTFS_DEFAULT_EXTENT_SIZE) {
1643                 rc = -EINVAL;
1644                 goto out;
1645         }
1646         rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
1647                                         ecryptfs_dentry,
1648                                         ECRYPTFS_VALIDATE_HEADER_SIZE);
1649         if (rc) {
1650                 rc = ecryptfs_read_xattr_region(page_virt,
1651                                                 ecryptfs_dentry);
1652                 if (rc) {
1653                         printk(KERN_DEBUG "Valid eCryptfs headers not found in "
1654                                "file header region or xattr region\n");
1655                         rc = -EINVAL;
1656                         goto out;
1657                 }
1658                 rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
1659                                                 ecryptfs_dentry,
1660                                                 ECRYPTFS_DONT_VALIDATE_HEADER_SIZE);
1661                 if (rc) {
1662                         printk(KERN_DEBUG "Valid eCryptfs headers not found in "
1663                                "file xattr region either\n");
1664                         rc = -EINVAL;
1665                 }
1666                 if (crypt_stat->mount_crypt_stat->flags
1667                     & ECRYPTFS_XATTR_METADATA_ENABLED) {
1668                         crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
1669                 } else {
1670                         printk(KERN_WARNING "Attempt to access file with "
1671                                "crypto metadata only in the extended attribute "
1672                                "region, but eCryptfs was mounted without "
1673                                "xattr support enabled. eCryptfs will not treat "
1674                                "this like an encrypted file.\n");
1675                         rc = -EINVAL;
1676                 }
1677         }
1678 out:
1679         if (page_virt) {
1680                 memset(page_virt, 0, PAGE_CACHE_SIZE);
1681                 kmem_cache_free(ecryptfs_header_cache_1, page_virt);
1682         }
1683         return rc;
1684 }
1685
1686 /**
1687  * ecryptfs_encode_filename - converts a plaintext file name to cipher text
1688  * @crypt_stat: The crypt_stat struct associated with the file anem to encode
1689  * @name: The plaintext name
1690  * @length: The length of the plaintext
1691  * @encoded_name: The encypted name
1692  *
1693  * Encrypts and encodes a filename into something that constitutes a
1694  * valid filename for a filesystem, with printable characters.
1695  *
1696  * We assume that we have a properly initialized crypto context,
1697  * pointed to by crypt_stat->tfm.
1698  *
1699  * TODO: Implement filename decoding and decryption here, in place of
1700  * memcpy. We are keeping the framework around for now to (1)
1701  * facilitate testing of the components needed to implement filename
1702  * encryption and (2) to provide a code base from which other
1703  * developers in the community can easily implement this feature.
1704  *
1705  * Returns the length of encoded filename; negative if error
1706  */
1707 int
1708 ecryptfs_encode_filename(struct ecryptfs_crypt_stat *crypt_stat,
1709                          const char *name, int length, char **encoded_name)
1710 {
1711         int error = 0;
1712
1713         (*encoded_name) = kmalloc(length + 2, GFP_KERNEL);
1714         if (!(*encoded_name)) {
1715                 error = -ENOMEM;
1716                 goto out;
1717         }
1718         /* TODO: Filename encryption is a scheduled feature for a
1719          * future version of eCryptfs. This function is here only for
1720          * the purpose of providing a framework for other developers
1721          * to easily implement filename encryption. Hint: Replace this
1722          * memcpy() with a call to encrypt and encode the
1723          * filename, the set the length accordingly. */
1724         memcpy((void *)(*encoded_name), (void *)name, length);
1725         (*encoded_name)[length] = '\0';
1726         error = length + 1;
1727 out:
1728         return error;
1729 }
1730
1731 /**
1732  * ecryptfs_decode_filename - converts the cipher text name to plaintext
1733  * @crypt_stat: The crypt_stat struct associated with the file
1734  * @name: The filename in cipher text
1735  * @length: The length of the cipher text name
1736  * @decrypted_name: The plaintext name
1737  *
1738  * Decodes and decrypts the filename.
1739  *
1740  * We assume that we have a properly initialized crypto context,
1741  * pointed to by crypt_stat->tfm.
1742  *
1743  * TODO: Implement filename decoding and decryption here, in place of
1744  * memcpy. We are keeping the framework around for now to (1)
1745  * facilitate testing of the components needed to implement filename
1746  * encryption and (2) to provide a code base from which other
1747  * developers in the community can easily implement this feature.
1748  *
1749  * Returns the length of decoded filename; negative if error
1750  */
1751 int
1752 ecryptfs_decode_filename(struct ecryptfs_crypt_stat *crypt_stat,
1753                          const char *name, int length, char **decrypted_name)
1754 {
1755         int error = 0;
1756
1757         (*decrypted_name) = kmalloc(length + 2, GFP_KERNEL);
1758         if (!(*decrypted_name)) {
1759                 error = -ENOMEM;
1760                 goto out;
1761         }
1762         /* TODO: Filename encryption is a scheduled feature for a
1763          * future version of eCryptfs. This function is here only for
1764          * the purpose of providing a framework for other developers
1765          * to easily implement filename encryption. Hint: Replace this
1766          * memcpy() with a call to decode and decrypt the
1767          * filename, the set the length accordingly. */
1768         memcpy((void *)(*decrypted_name), (void *)name, length);
1769         (*decrypted_name)[length + 1] = '\0';   /* Only for convenience
1770                                                  * in printing out the
1771                                                  * string in debug
1772                                                  * messages */
1773         error = length;
1774 out:
1775         return error;
1776 }
1777
1778 /**
1779  * ecryptfs_process_cipher - Perform cipher initialization.
1780  * @key_tfm: Crypto context for key material, set by this function
1781  * @cipher_name: Name of the cipher
1782  * @key_size: Size of the key in bytes
1783  *
1784  * Returns zero on success. Any crypto_tfm structs allocated here
1785  * should be released by other functions, such as on a superblock put
1786  * event, regardless of whether this function succeeds for fails.
1787  */
1788 int
1789 ecryptfs_process_cipher(struct crypto_blkcipher **key_tfm, char *cipher_name,
1790                         size_t *key_size)
1791 {
1792         char dummy_key[ECRYPTFS_MAX_KEY_BYTES];
1793         char *full_alg_name;
1794         int rc;
1795
1796         *key_tfm = NULL;
1797         if (*key_size > ECRYPTFS_MAX_KEY_BYTES) {
1798                 rc = -EINVAL;
1799                 printk(KERN_ERR "Requested key size is [%Zd] bytes; maximum "
1800                       "allowable is [%d]\n", *key_size, ECRYPTFS_MAX_KEY_BYTES);
1801                 goto out;
1802         }
1803         rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name, cipher_name,
1804                                                     "ecb");
1805         if (rc)
1806                 goto out;
1807         *key_tfm = crypto_alloc_blkcipher(full_alg_name, 0, CRYPTO_ALG_ASYNC);
1808         kfree(full_alg_name);
1809         if (IS_ERR(*key_tfm)) {
1810                 rc = PTR_ERR(*key_tfm);
1811                 printk(KERN_ERR "Unable to allocate crypto cipher with name "
1812                        "[%s]; rc = [%d]\n", cipher_name, rc);
1813                 goto out;
1814         }
1815         crypto_blkcipher_set_flags(*key_tfm, CRYPTO_TFM_REQ_WEAK_KEY);
1816         if (*key_size == 0) {
1817                 struct blkcipher_alg *alg = crypto_blkcipher_alg(*key_tfm);
1818
1819                 *key_size = alg->max_keysize;
1820         }
1821         get_random_bytes(dummy_key, *key_size);
1822         rc = crypto_blkcipher_setkey(*key_tfm, dummy_key, *key_size);
1823         if (rc) {
1824                 printk(KERN_ERR "Error attempting to set key of size [%Zd] for "
1825                        "cipher [%s]; rc = [%d]\n", *key_size, cipher_name, rc);
1826                 rc = -EINVAL;
1827                 goto out;
1828         }
1829 out:
1830         return rc;
1831 }