xref: /openbmc/linux/fs/ecryptfs/crypto.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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 }
1832