summaryrefslogtreecommitdiffstats
path: root/fs/ext4/crypto_fname.c
blob: fded02f7229921a8693909ade14c2e7b16095f5e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
/*
 * linux/fs/ext4/crypto_fname.c
 *
 * Copyright (C) 2015, Google, Inc.
 *
 * This contains functions for filename crypto management in ext4
 *
 * Written by Uday Savagaonkar, 2014.
 *
 * This has not yet undergone a rigorous security audit.
 *
 */

#include <crypto/hash.h>
#include <crypto/sha.h>
#include <keys/encrypted-type.h>
#include <keys/user-type.h>
#include <linux/crypto.h>
#include <linux/gfp.h>
#include <linux/kernel.h>
#include <linux/key.h>
#include <linux/key.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/spinlock_types.h>

#include "ext4.h"
#include "ext4_crypto.h"
#include "xattr.h"

/**
 * ext4_dir_crypt_complete() -
 */
static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res)
{
	struct ext4_completion_result *ecr = req->data;

	if (res == -EINPROGRESS)
		return;
	ecr->res = res;
	complete(&ecr->completion);
}

bool ext4_valid_filenames_enc_mode(uint32_t mode)
{
	return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS);
}

/**
 * ext4_fname_encrypt() -
 *
 * This function encrypts the input filename, and returns the length of the
 * ciphertext. Errors are returned as negative numbers.  We trust the caller to
 * allocate sufficient memory to oname string.
 */
static int ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx,
			      const struct qstr *iname,
			      struct ext4_str *oname)
{
	u32 ciphertext_len;
	struct ablkcipher_request *req = NULL;
	DECLARE_EXT4_COMPLETION_RESULT(ecr);
	struct crypto_ablkcipher *tfm = ctx->ctfm;
	int res = 0;
	char iv[EXT4_CRYPTO_BLOCK_SIZE];
	struct scatterlist sg[1];
	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);
	char *workbuf;

	if (iname->len <= 0 || iname->len > ctx->lim)
		return -EIO;

	ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ?
		EXT4_CRYPTO_BLOCK_SIZE : iname->len;
	ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
	ciphertext_len = (ciphertext_len > ctx->lim)
			? ctx->lim : ciphertext_len;

	/* Allocate request */
	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
	if (!req) {
		printk_ratelimited(
		    KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
		return -ENOMEM;
	}
	ablkcipher_request_set_callback(req,
		CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
		ext4_dir_crypt_complete, &ecr);

	/* Map the workpage */
	workbuf = kmap(ctx->workpage);

	/* Copy the input */
	memcpy(workbuf, iname->name, iname->len);
	if (iname->len < ciphertext_len)
		memset(workbuf + iname->len, 0, ciphertext_len - iname->len);

	/* Initialize IV */
	memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);

	/* Create encryption request */
	sg_init_table(sg, 1);
	sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
	ablkcipher_request_set_crypt(req, sg, sg, ciphertext_len, iv);
	res = crypto_ablkcipher_encrypt(req);
	if (res == -EINPROGRESS || res == -EBUSY) {
		BUG_ON(req->base.data != &ecr);
		wait_for_completion(&ecr.completion);
		res = ecr.res;
	}
	if (res >= 0) {
		/* Copy the result to output */
		memcpy(oname->name, workbuf, ciphertext_len);
		res = ciphertext_len;
	}
	kunmap(ctx->workpage);
	ablkcipher_request_free(req);
	if (res < 0) {
		printk_ratelimited(
		    KERN_ERR "%s: Error (error code %d)\n", __func__, res);
	}
	oname->len = ciphertext_len;
	return res;
}

/*
 * ext4_fname_decrypt()
 *	This function decrypts the input filename, and returns
 *	the length of the plaintext.
 *	Errors are returned as negative numbers.
 *	We trust the caller to allocate sufficient memory to oname string.
 */
static int ext4_fname_decrypt(struct ext4_fname_crypto_ctx *ctx,
			      const struct ext4_str *iname,
			      struct ext4_str *oname)
{
	struct ext4_str tmp_in[2], tmp_out[1];
	struct ablkcipher_request *req = NULL;
	DECLARE_EXT4_COMPLETION_RESULT(ecr);
	struct scatterlist sg[1];
	struct crypto_ablkcipher *tfm = ctx->ctfm;
	int res = 0;
	char iv[EXT4_CRYPTO_BLOCK_SIZE];
	char *workbuf;

	if (iname->len <= 0 || iname->len > ctx->lim)
		return -EIO;

	tmp_in[0].name = iname->name;
	tmp_in[0].len = iname->len;
	tmp_out[0].name = oname->name;

	/* Allocate request */
	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
	if (!req) {
		printk_ratelimited(
		    KERN_ERR "%s: crypto_request_alloc() failed\n",  __func__);
		return -ENOMEM;
	}
	ablkcipher_request_set_callback(req,
		CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
		ext4_dir_crypt_complete, &ecr);

	/* Map the workpage */
	workbuf = kmap(ctx->workpage);

	/* Copy the input */
	memcpy(workbuf, iname->name, iname->len);

	/* Initialize IV */
	memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);

	/* Create encryption request */
	sg_init_table(sg, 1);
	sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
	ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
	res = crypto_ablkcipher_decrypt(req);
	if (res == -EINPROGRESS || res == -EBUSY) {
		BUG_ON(req->base.data != &ecr);
		wait_for_completion(&ecr.completion);
		res = ecr.res;
	}
	if (res >= 0) {
		/* Copy the result to output */
		memcpy(oname->name, workbuf, iname->len);
		res = iname->len;
	}
	kunmap(ctx->workpage);
	ablkcipher_request_free(req);
	if (res < 0) {
		printk_ratelimited(
		    KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n",
		    __func__, res);
		return res;
	}

	oname->len = strnlen(oname->name, iname->len);
	return oname->len;
}

static const char *lookup_table =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";

/**
 * ext4_fname_encode_digest() -
 *
 * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
 * The encoded string is roughly 4/3 times the size of the input string.
 */
static int digest_encode(const char *src, int len, char *dst)
{
	int i = 0, bits = 0, ac = 0;
	char *cp = dst;

	while (i < len) {
		ac += (((unsigned char) src[i]) << bits);
		bits += 8;
		do {
			*cp++ = lookup_table[ac & 0x3f];
			ac >>= 6;
			bits -= 6;
		} while (bits >= 6);
		i++;
	}
	if (bits)
		*cp++ = lookup_table[ac & 0x3f];
	return cp - dst;
}

static int digest_decode(const char *src, int len, char *dst)
{
	int i = 0, bits = 0, ac = 0;
	const char *p;
	char *cp = dst;

	while (i < len) {
		p = strchr(lookup_table, src[i]);
		if (p == NULL || src[i] == 0)
			return -2;
		ac += (p - lookup_table) << bits;
		bits += 6;
		if (bits >= 8) {
			*cp++ = ac & 0xff;
			ac >>= 8;
			bits -= 8;
		}
		i++;
	}
	if (ac)
		return -1;
	return cp - dst;
}

/**
 * ext4_free_fname_crypto_ctx() -
 *
 * Frees up a crypto context.
 */
void ext4_free_fname_crypto_ctx(struct ext4_fname_crypto_ctx *ctx)
{
	if (ctx == NULL || IS_ERR(ctx))
		return;

	if (ctx->ctfm && !IS_ERR(ctx->ctfm))
		crypto_free_ablkcipher(ctx->ctfm);
	if (ctx->htfm && !IS_ERR(ctx->htfm))
		crypto_free_hash(ctx->htfm);
	if (ctx->workpage && !IS_ERR(ctx->workpage))
		__free_page(ctx->workpage);
	kfree(ctx);
}

/**
 * ext4_put_fname_crypto_ctx() -
 *
 * Return: The crypto context onto free list. If the free list is above a
 * threshold, completely frees up the context, and returns the memory.
 *
 * TODO: Currently we directly free the crypto context. Eventually we should
 * add code it to return to free list. Such an approach will increase
 * efficiency of directory lookup.
 */
void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx)
{
	if (*ctx == NULL || IS_ERR(*ctx))
		return;
	ext4_free_fname_crypto_ctx(*ctx);
	*ctx = NULL;
}

/**
 * ext4_search_fname_crypto_ctx() -
 */
static struct ext4_fname_crypto_ctx *ext4_search_fname_crypto_ctx(
		const struct ext4_encryption_key *key)
{
	return NULL;
}

/**
 * ext4_alloc_fname_crypto_ctx() -
 */
struct ext4_fname_crypto_ctx *ext4_alloc_fname_crypto_ctx(
	const struct ext4_encryption_key *key)
{
	struct ext4_fname_crypto_ctx *ctx;

	ctx = kmalloc(sizeof(struct ext4_fname_crypto_ctx), GFP_NOFS);
	if (ctx == NULL)
		return ERR_PTR(-ENOMEM);
	if (key->mode == EXT4_ENCRYPTION_MODE_INVALID) {
		/* This will automatically set key mode to invalid
		 * As enum for ENCRYPTION_MODE_INVALID is zero */
		memset(&ctx->key, 0, sizeof(ctx->key));
	} else {
		memcpy(&ctx->key, key, sizeof(struct ext4_encryption_key));
	}
	ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == key->mode)
		? 0 : 1;
	ctx->ctfm_key_is_ready = 0;
	ctx->ctfm = NULL;
	ctx->htfm = NULL;
	ctx->workpage = NULL;
	return ctx;
}

/**
 * ext4_get_fname_crypto_ctx() -
 *
 * Allocates a free crypto context and initializes it to hold
 * the crypto material for the inode.
 *
 * Return: NULL if not encrypted. Error value on error. Valid pointer otherwise.
 */
struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
	struct inode *inode, u32 max_ciphertext_len)
{
	struct ext4_fname_crypto_ctx *ctx;
	struct ext4_inode_info *ei = EXT4_I(inode);
	int res;

	/* Check if the crypto policy is set on the inode */
	res = ext4_encrypted_inode(inode);
	if (res == 0)
		return NULL;

	if (!ext4_has_encryption_key(inode))
		ext4_generate_encryption_key(inode);

	/* Get a crypto context based on the key.
	 * A new context is allocated if no context matches the requested key.
	 */
	ctx = ext4_search_fname_crypto_ctx(&(ei->i_encryption_key));
	if (ctx == NULL)
		ctx = ext4_alloc_fname_crypto_ctx(&(ei->i_encryption_key));
	if (IS_ERR(ctx))
		return ctx;

	ctx->flags = ei->i_crypt_policy_flags;
	if (ctx->has_valid_key) {
		if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
			printk_once(KERN_WARNING
				    "ext4: unsupported key mode %d\n",
				    ctx->key.mode);
			return ERR_PTR(-ENOKEY);
		}

		/* As a first cut, we will allocate new tfm in every call.
		 * later, we will keep the tfm around, in case the key gets
		 * re-used */
		if (ctx->ctfm == NULL) {
			ctx->ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))",
					0, 0);
		}
		if (IS_ERR(ctx->ctfm)) {
			res = PTR_ERR(ctx->ctfm);
			printk(
			    KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
			    __func__, res);
			ctx->ctfm = NULL;
			ext4_put_fname_crypto_ctx(&ctx);
			return ERR_PTR(res);
		}
		if (ctx->ctfm == NULL) {
			printk(
			    KERN_DEBUG "%s: could not allocate crypto tfm\n",
			    __func__);
			ext4_put_fname_crypto_ctx(&ctx);
			return ERR_PTR(-ENOMEM);
		}
		if (ctx->workpage == NULL)
			ctx->workpage = alloc_page(GFP_NOFS);
		if (IS_ERR(ctx->workpage)) {
			res = PTR_ERR(ctx->workpage);
			printk(
			    KERN_DEBUG "%s: error (%d) allocating work page\n",
			    __func__, res);
			ctx->workpage = NULL;
			ext4_put_fname_crypto_ctx(&ctx);
			return ERR_PTR(res);
		}
		if (ctx->workpage == NULL) {
			printk(
			    KERN_DEBUG "%s: could not allocate work page\n",
			    __func__);
			ext4_put_fname_crypto_ctx(&ctx);
			return ERR_PTR(-ENOMEM);
		}
		ctx->lim = max_ciphertext_len;
		crypto_ablkcipher_clear_flags(ctx->ctfm, ~0);
		crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctx->ctfm),
			CRYPTO_TFM_REQ_WEAK_KEY);

		/* If we are lucky, we will get a context that is already
		 * set up with the right key. Else, we will have to
		 * set the key */
		if (!ctx->ctfm_key_is_ready) {
			/* Since our crypto objectives for filename encryption
			 * are pretty weak,
			 * we directly use the inode master key */
			res = crypto_ablkcipher_setkey(ctx->ctfm,
					ctx->key.raw, ctx->key.size);
			if (res) {
				ext4_put_fname_crypto_ctx(&ctx);
				return ERR_PTR(-EIO);
			}
			ctx->ctfm_key_is_ready = 1;
		} else {
			/* In the current implementation, key should never be
			 * marked "ready" for a context that has just been
			 * allocated. So we should never reach here */
			 BUG();
		}
	}
	if (ctx->htfm == NULL)
		ctx->htfm = crypto_alloc_hash("sha256", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(ctx->htfm)) {
		res = PTR_ERR(ctx->htfm);
		printk(KERN_DEBUG "%s: error (%d) allocating hash tfm\n",
			__func__, res);
		ctx->htfm = NULL;
		ext4_put_fname_crypto_ctx(&ctx);
		return ERR_PTR(res);
	}
	if (ctx->htfm == NULL) {
		printk(KERN_DEBUG "%s: could not allocate hash tfm\n",
				__func__);
		ext4_put_fname_crypto_ctx(&ctx);
		return ERR_PTR(-ENOMEM);
	}

	return ctx;
}

/**
 * ext4_fname_crypto_round_up() -
 *
 * Return: The next multiple of block size
 */
u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
{
	return ((size+blksize-1)/blksize)*blksize;
}

/**
 * ext4_fname_crypto_namelen_on_disk() -
 */
int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,
				      u32 namelen)
{
	u32 ciphertext_len;
	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);

	if (ctx == NULL)
		return -EIO;
	if (!(ctx->has_valid_key))
		return -EACCES;
	ciphertext_len = (namelen < EXT4_CRYPTO_BLOCK_SIZE) ?
		EXT4_CRYPTO_BLOCK_SIZE : namelen;
	ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
	ciphertext_len = (ciphertext_len > ctx->lim)
			? ctx->lim : ciphertext_len;
	return (int) ciphertext_len;
}

/**
 * ext4_fname_crypto_alloc_obuff() -
 *
 * Allocates an output buffer that is sufficient for the crypto operation
 * specified by the context and the direction.
 */
int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,
				   u32 ilen, struct ext4_str *crypto_str)
{
	unsigned int olen;
	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);

	if (!ctx)
		return -EIO;
	if (padding < EXT4_CRYPTO_BLOCK_SIZE)
		padding = EXT4_CRYPTO_BLOCK_SIZE;
	olen = ext4_fname_crypto_round_up(ilen, padding);
	crypto_str->len = olen;
	if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
		olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;
	/* Allocated buffer can hold one more character to null-terminate the
	 * string */
	crypto_str->name = kmalloc(olen+1, GFP_NOFS);
	if (!(crypto_str->name))
		return -ENOMEM;
	return 0;
}

/**
 * ext4_fname_crypto_free_buffer() -
 *
 * Frees the buffer allocated for crypto operation.
 */
void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str)
{
	if (!crypto_str)
		return;
	kfree(crypto_str->name);
	crypto_str->name = NULL;
}

/**
 * ext4_fname_disk_to_usr() - converts a filename from disk space to user space
 */
int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
			    struct dx_hash_info *hinfo,
			    const struct ext4_str *iname,
			    struct ext4_str *oname)
{
	char buf[24];
	int ret;

	if (ctx == NULL)
		return -EIO;
	if (iname->len < 3) {
		/*Check for . and .. */
		if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') {
			oname->name[0] = '.';
			oname->name[iname->len-1] = '.';
			oname->len = iname->len;
			return oname->len;
		}
	}
	if (ctx->has_valid_key)
		return ext4_fname_decrypt(ctx, iname, oname);

	if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {
		ret = digest_encode(iname->name, iname->len, oname->name);
		oname->len = ret;
		return ret;
	}
	if (hinfo) {
		memcpy(buf, &hinfo->hash, 4);
		memcpy(buf+4, &hinfo->minor_hash, 4);
	} else
		memset(buf, 0, 8);
	memcpy(buf + 8, iname->name + iname->len - 16, 16);
	oname->name[0] = '_';
	ret = digest_encode(buf, 24, oname->name+1);
	oname->len = ret + 1;
	return ret + 1;
}

int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
			   struct dx_hash_info *hinfo,
			   const struct ext4_dir_entry_2 *de,
			   struct ext4_str *oname)
{
	struct ext4_str iname = {.name = (unsigned char *) de->name,
				 .len = de->name_len };

	return _ext4_fname_disk_to_usr(ctx, hinfo, &iname, oname);
}


/**
 * ext4_fname_usr_to_disk() - converts a filename from user space to disk space
 */
int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
			   const struct qstr *iname,
			   struct ext4_str *oname)
{
	int res;

	if (ctx == NULL)
		return -EIO;
	if (iname->len < 3) {
		/*Check for . and .. */
		if (iname->name[0] == '.' &&
				iname->name[iname->len-1] == '.') {
			oname->name[0] = '.';
			oname->name[iname->len-1] = '.';
			oname->len = iname->len;
			return oname->len;
		}
	}
	if (ctx->has_valid_key) {
		res = ext4_fname_encrypt(ctx, iname, oname);
		return res;
	}
	/* Without a proper key, a user is not allowed to modify the filenames
	 * in a directory. Consequently, a user space name cannot be mapped to
	 * a disk-space name */
	return -EACCES;
}

/*
 * Calculate the htree hash from a filename from user space
 */
int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,
			    const struct qstr *iname,
			    struct dx_hash_info *hinfo)
{
	struct ext4_str tmp;
	int ret = 0;
	char buf[EXT4_FNAME_CRYPTO_DIGEST_SIZE+1];

	if (!ctx ||
	    ((iname->name[0] == '.') &&
	     ((iname->len == 1) ||
	      ((iname->name[1] == '.') && (iname->len == 2))))) {
		ext4fs_dirhash(iname->name, iname->len, hinfo);
		return 0;
	}

	if (!ctx->has_valid_key && iname->name[0] == '_') {
		if (iname->len != 33)
			return -ENOENT;
		ret = digest_decode(iname->name+1, iname->len, buf);
		if (ret != 24)
			return -ENOENT;
		memcpy(&hinfo->hash, buf, 4);
		memcpy(&hinfo->minor_hash, buf + 4, 4);
		return 0;
	}

	if (!ctx->has_valid_key && iname->name[0] != '_') {
		if (iname->len > 43)
			return -ENOENT;
		ret = digest_decode(iname->name, iname->len, buf);
		ext4fs_dirhash(buf, ret, hinfo);
		return 0;
	}

	/* First encrypt the plaintext name */
	ret = ext4_fname_crypto_alloc_buffer(ctx, iname->len, &tmp);
	if (ret < 0)
		return ret;

	ret = ext4_fname_encrypt(ctx, iname, &tmp);
	if (ret >= 0) {
		ext4fs_dirhash(tmp.name, tmp.len, hinfo);
		ret = 0;
	}

	ext4_fname_crypto_free_buffer(&tmp);
	return ret;
}

int ext4_fname_match(struct ext4_fname_crypto_ctx *ctx, struct ext4_str *cstr,
		     int len, const char * const name,
		     struct ext4_dir_entry_2 *de)
{
	int ret = -ENOENT;
	int bigname = (*name == '_');

	if (ctx->has_valid_key) {
		if (cstr->name == NULL) {
			struct qstr istr;

			ret = ext4_fname_crypto_alloc_buffer(ctx, len, cstr);
			if (ret < 0)
				goto errout;
			istr.name = name;
			istr.len = len;
			ret = ext4_fname_encrypt(ctx, &istr, cstr);
			if (ret < 0)
				goto errout;
		}
	} else {
		if (cstr->name == NULL) {
			cstr->name = kmalloc(32, GFP_KERNEL);
			if (cstr->name == NULL)
				return -ENOMEM;
			if ((bigname && (len != 33)) ||
			    (!bigname && (len > 43)))
				goto errout;
			ret = digest_decode(name+bigname, len-bigname,
					    cstr->name);
			if (ret < 0) {
				ret = -ENOENT;
				goto errout;
			}
			cstr->len = ret;
		}
		if (bigname) {
			if (de->name_len < 16)
				return 0;
			ret = memcmp(de->name + de->name_len - 16,
				     cstr->name + 8, 16);
			return (ret == 0) ? 1 : 0;
		}
	}
	if (de->name_len != cstr->len)
		return 0;
	ret = memcmp(de->name, cstr->name, cstr->len);
	return (ret == 0) ? 1 : 0;
errout:
	kfree(cstr->name);
	cstr->name = NULL;
	return ret;
}