1/*
2 * linux/fs/ext4/crypto_fname.c
3 *
4 * Copyright (C) 2015, Google, Inc.
5 *
6 * This contains functions for filename crypto management in ext4
7 *
8 * Written by Uday Savagaonkar, 2014.
9 *
10 * This has not yet undergone a rigorous security audit.
11 *
12 */
13
14#include <crypto/hash.h>
15#include <crypto/sha.h>
16#include <keys/encrypted-type.h>
17#include <keys/user-type.h>
18#include <linux/crypto.h>
19#include <linux/gfp.h>
20#include <linux/kernel.h>
21#include <linux/key.h>
22#include <linux/key.h>
23#include <linux/list.h>
24#include <linux/mempool.h>
25#include <linux/random.h>
26#include <linux/scatterlist.h>
27#include <linux/spinlock_types.h>
28
29#include "ext4.h"
30#include "ext4_crypto.h"
31#include "xattr.h"
32
33/**
34 * ext4_dir_crypt_complete() -
35 */
36static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res)
37{
38	struct ext4_completion_result *ecr = req->data;
39
40	if (res == -EINPROGRESS)
41		return;
42	ecr->res = res;
43	complete(&ecr->completion);
44}
45
46bool ext4_valid_filenames_enc_mode(uint32_t mode)
47{
48	return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS);
49}
50
51/**
52 * ext4_fname_encrypt() -
53 *
54 * This function encrypts the input filename, and returns the length of the
55 * ciphertext. Errors are returned as negative numbers.  We trust the caller to
56 * allocate sufficient memory to oname string.
57 */
58static int ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx,
59			      const struct qstr *iname,
60			      struct ext4_str *oname)
61{
62	u32 ciphertext_len;
63	struct ablkcipher_request *req = NULL;
64	DECLARE_EXT4_COMPLETION_RESULT(ecr);
65	struct crypto_ablkcipher *tfm = ctx->ctfm;
66	int res = 0;
67	char iv[EXT4_CRYPTO_BLOCK_SIZE];
68	struct scatterlist sg[1];
69	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);
70	char *workbuf;
71
72	if (iname->len <= 0 || iname->len > ctx->lim)
73		return -EIO;
74
75	ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ?
76		EXT4_CRYPTO_BLOCK_SIZE : iname->len;
77	ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
78	ciphertext_len = (ciphertext_len > ctx->lim)
79			? ctx->lim : ciphertext_len;
80
81	/* Allocate request */
82	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
83	if (!req) {
84		printk_ratelimited(
85		    KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
86		return -ENOMEM;
87	}
88	ablkcipher_request_set_callback(req,
89		CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
90		ext4_dir_crypt_complete, &ecr);
91
92	/* Map the workpage */
93	workbuf = kmap(ctx->workpage);
94
95	/* Copy the input */
96	memcpy(workbuf, iname->name, iname->len);
97	if (iname->len < ciphertext_len)
98		memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
99
100	/* Initialize IV */
101	memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
102
103	/* Create encryption request */
104	sg_init_table(sg, 1);
105	sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
106	ablkcipher_request_set_crypt(req, sg, sg, ciphertext_len, iv);
107	res = crypto_ablkcipher_encrypt(req);
108	if (res == -EINPROGRESS || res == -EBUSY) {
109		BUG_ON(req->base.data != &ecr);
110		wait_for_completion(&ecr.completion);
111		res = ecr.res;
112	}
113	if (res >= 0) {
114		/* Copy the result to output */
115		memcpy(oname->name, workbuf, ciphertext_len);
116		res = ciphertext_len;
117	}
118	kunmap(ctx->workpage);
119	ablkcipher_request_free(req);
120	if (res < 0) {
121		printk_ratelimited(
122		    KERN_ERR "%s: Error (error code %d)\n", __func__, res);
123	}
124	oname->len = ciphertext_len;
125	return res;
126}
127
128/*
129 * ext4_fname_decrypt()
130 *	This function decrypts the input filename, and returns
131 *	the length of the plaintext.
132 *	Errors are returned as negative numbers.
133 *	We trust the caller to allocate sufficient memory to oname string.
134 */
135static int ext4_fname_decrypt(struct ext4_fname_crypto_ctx *ctx,
136			      const struct ext4_str *iname,
137			      struct ext4_str *oname)
138{
139	struct ext4_str tmp_in[2], tmp_out[1];
140	struct ablkcipher_request *req = NULL;
141	DECLARE_EXT4_COMPLETION_RESULT(ecr);
142	struct scatterlist sg[1];
143	struct crypto_ablkcipher *tfm = ctx->ctfm;
144	int res = 0;
145	char iv[EXT4_CRYPTO_BLOCK_SIZE];
146	char *workbuf;
147
148	if (iname->len <= 0 || iname->len > ctx->lim)
149		return -EIO;
150
151	tmp_in[0].name = iname->name;
152	tmp_in[0].len = iname->len;
153	tmp_out[0].name = oname->name;
154
155	/* Allocate request */
156	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
157	if (!req) {
158		printk_ratelimited(
159		    KERN_ERR "%s: crypto_request_alloc() failed\n",  __func__);
160		return -ENOMEM;
161	}
162	ablkcipher_request_set_callback(req,
163		CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
164		ext4_dir_crypt_complete, &ecr);
165
166	/* Map the workpage */
167	workbuf = kmap(ctx->workpage);
168
169	/* Copy the input */
170	memcpy(workbuf, iname->name, iname->len);
171
172	/* Initialize IV */
173	memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
174
175	/* Create encryption request */
176	sg_init_table(sg, 1);
177	sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
178	ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
179	res = crypto_ablkcipher_decrypt(req);
180	if (res == -EINPROGRESS || res == -EBUSY) {
181		BUG_ON(req->base.data != &ecr);
182		wait_for_completion(&ecr.completion);
183		res = ecr.res;
184	}
185	if (res >= 0) {
186		/* Copy the result to output */
187		memcpy(oname->name, workbuf, iname->len);
188		res = iname->len;
189	}
190	kunmap(ctx->workpage);
191	ablkcipher_request_free(req);
192	if (res < 0) {
193		printk_ratelimited(
194		    KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n",
195		    __func__, res);
196		return res;
197	}
198
199	oname->len = strnlen(oname->name, iname->len);
200	return oname->len;
201}
202
203static const char *lookup_table =
204	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
205
206/**
207 * ext4_fname_encode_digest() -
208 *
209 * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
210 * The encoded string is roughly 4/3 times the size of the input string.
211 */
212static int digest_encode(const char *src, int len, char *dst)
213{
214	int i = 0, bits = 0, ac = 0;
215	char *cp = dst;
216
217	while (i < len) {
218		ac += (((unsigned char) src[i]) << bits);
219		bits += 8;
220		do {
221			*cp++ = lookup_table[ac & 0x3f];
222			ac >>= 6;
223			bits -= 6;
224		} while (bits >= 6);
225		i++;
226	}
227	if (bits)
228		*cp++ = lookup_table[ac & 0x3f];
229	return cp - dst;
230}
231
232static int digest_decode(const char *src, int len, char *dst)
233{
234	int i = 0, bits = 0, ac = 0;
235	const char *p;
236	char *cp = dst;
237
238	while (i < len) {
239		p = strchr(lookup_table, src[i]);
240		if (p == NULL || src[i] == 0)
241			return -2;
242		ac += (p - lookup_table) << bits;
243		bits += 6;
244		if (bits >= 8) {
245			*cp++ = ac & 0xff;
246			ac >>= 8;
247			bits -= 8;
248		}
249		i++;
250	}
251	if (ac)
252		return -1;
253	return cp - dst;
254}
255
256/**
257 * ext4_free_fname_crypto_ctx() -
258 *
259 * Frees up a crypto context.
260 */
261void ext4_free_fname_crypto_ctx(struct ext4_fname_crypto_ctx *ctx)
262{
263	if (ctx == NULL || IS_ERR(ctx))
264		return;
265
266	if (ctx->ctfm && !IS_ERR(ctx->ctfm))
267		crypto_free_ablkcipher(ctx->ctfm);
268	if (ctx->htfm && !IS_ERR(ctx->htfm))
269		crypto_free_hash(ctx->htfm);
270	if (ctx->workpage && !IS_ERR(ctx->workpage))
271		__free_page(ctx->workpage);
272	kfree(ctx);
273}
274
275/**
276 * ext4_put_fname_crypto_ctx() -
277 *
278 * Return: The crypto context onto free list. If the free list is above a
279 * threshold, completely frees up the context, and returns the memory.
280 *
281 * TODO: Currently we directly free the crypto context. Eventually we should
282 * add code it to return to free list. Such an approach will increase
283 * efficiency of directory lookup.
284 */
285void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx)
286{
287	if (*ctx == NULL || IS_ERR(*ctx))
288		return;
289	ext4_free_fname_crypto_ctx(*ctx);
290	*ctx = NULL;
291}
292
293/**
294 * ext4_search_fname_crypto_ctx() -
295 */
296static struct ext4_fname_crypto_ctx *ext4_search_fname_crypto_ctx(
297		const struct ext4_encryption_key *key)
298{
299	return NULL;
300}
301
302/**
303 * ext4_alloc_fname_crypto_ctx() -
304 */
305struct ext4_fname_crypto_ctx *ext4_alloc_fname_crypto_ctx(
306	const struct ext4_encryption_key *key)
307{
308	struct ext4_fname_crypto_ctx *ctx;
309
310	ctx = kmalloc(sizeof(struct ext4_fname_crypto_ctx), GFP_NOFS);
311	if (ctx == NULL)
312		return ERR_PTR(-ENOMEM);
313	if (key->mode == EXT4_ENCRYPTION_MODE_INVALID) {
314		/* This will automatically set key mode to invalid
315		 * As enum for ENCRYPTION_MODE_INVALID is zero */
316		memset(&ctx->key, 0, sizeof(ctx->key));
317	} else {
318		memcpy(&ctx->key, key, sizeof(struct ext4_encryption_key));
319	}
320	ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == key->mode)
321		? 0 : 1;
322	ctx->ctfm_key_is_ready = 0;
323	ctx->ctfm = NULL;
324	ctx->htfm = NULL;
325	ctx->workpage = NULL;
326	return ctx;
327}
328
329/**
330 * ext4_get_fname_crypto_ctx() -
331 *
332 * Allocates a free crypto context and initializes it to hold
333 * the crypto material for the inode.
334 *
335 * Return: NULL if not encrypted. Error value on error. Valid pointer otherwise.
336 */
337struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
338	struct inode *inode, u32 max_ciphertext_len)
339{
340	struct ext4_fname_crypto_ctx *ctx;
341	struct ext4_inode_info *ei = EXT4_I(inode);
342	int res;
343
344	/* Check if the crypto policy is set on the inode */
345	res = ext4_encrypted_inode(inode);
346	if (res == 0)
347		return NULL;
348
349	if (!ext4_has_encryption_key(inode))
350		ext4_generate_encryption_key(inode);
351
352	/* Get a crypto context based on the key.
353	 * A new context is allocated if no context matches the requested key.
354	 */
355	ctx = ext4_search_fname_crypto_ctx(&(ei->i_encryption_key));
356	if (ctx == NULL)
357		ctx = ext4_alloc_fname_crypto_ctx(&(ei->i_encryption_key));
358	if (IS_ERR(ctx))
359		return ctx;
360
361	ctx->flags = ei->i_crypt_policy_flags;
362	if (ctx->has_valid_key) {
363		if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
364			printk_once(KERN_WARNING
365				    "ext4: unsupported key mode %d\n",
366				    ctx->key.mode);
367			return ERR_PTR(-ENOKEY);
368		}
369
370		/* As a first cut, we will allocate new tfm in every call.
371		 * later, we will keep the tfm around, in case the key gets
372		 * re-used */
373		if (ctx->ctfm == NULL) {
374			ctx->ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))",
375					0, 0);
376		}
377		if (IS_ERR(ctx->ctfm)) {
378			res = PTR_ERR(ctx->ctfm);
379			printk(
380			    KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
381			    __func__, res);
382			ctx->ctfm = NULL;
383			ext4_put_fname_crypto_ctx(&ctx);
384			return ERR_PTR(res);
385		}
386		if (ctx->ctfm == NULL) {
387			printk(
388			    KERN_DEBUG "%s: could not allocate crypto tfm\n",
389			    __func__);
390			ext4_put_fname_crypto_ctx(&ctx);
391			return ERR_PTR(-ENOMEM);
392		}
393		if (ctx->workpage == NULL)
394			ctx->workpage = alloc_page(GFP_NOFS);
395		if (IS_ERR(ctx->workpage)) {
396			res = PTR_ERR(ctx->workpage);
397			printk(
398			    KERN_DEBUG "%s: error (%d) allocating work page\n",
399			    __func__, res);
400			ctx->workpage = NULL;
401			ext4_put_fname_crypto_ctx(&ctx);
402			return ERR_PTR(res);
403		}
404		if (ctx->workpage == NULL) {
405			printk(
406			    KERN_DEBUG "%s: could not allocate work page\n",
407			    __func__);
408			ext4_put_fname_crypto_ctx(&ctx);
409			return ERR_PTR(-ENOMEM);
410		}
411		ctx->lim = max_ciphertext_len;
412		crypto_ablkcipher_clear_flags(ctx->ctfm, ~0);
413		crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctx->ctfm),
414			CRYPTO_TFM_REQ_WEAK_KEY);
415
416		/* If we are lucky, we will get a context that is already
417		 * set up with the right key. Else, we will have to
418		 * set the key */
419		if (!ctx->ctfm_key_is_ready) {
420			/* Since our crypto objectives for filename encryption
421			 * are pretty weak,
422			 * we directly use the inode master key */
423			res = crypto_ablkcipher_setkey(ctx->ctfm,
424					ctx->key.raw, ctx->key.size);
425			if (res) {
426				ext4_put_fname_crypto_ctx(&ctx);
427				return ERR_PTR(-EIO);
428			}
429			ctx->ctfm_key_is_ready = 1;
430		} else {
431			/* In the current implementation, key should never be
432			 * marked "ready" for a context that has just been
433			 * allocated. So we should never reach here */
434			 BUG();
435		}
436	}
437	if (ctx->htfm == NULL)
438		ctx->htfm = crypto_alloc_hash("sha256", 0, CRYPTO_ALG_ASYNC);
439	if (IS_ERR(ctx->htfm)) {
440		res = PTR_ERR(ctx->htfm);
441		printk(KERN_DEBUG "%s: error (%d) allocating hash tfm\n",
442			__func__, res);
443		ctx->htfm = NULL;
444		ext4_put_fname_crypto_ctx(&ctx);
445		return ERR_PTR(res);
446	}
447	if (ctx->htfm == NULL) {
448		printk(KERN_DEBUG "%s: could not allocate hash tfm\n",
449				__func__);
450		ext4_put_fname_crypto_ctx(&ctx);
451		return ERR_PTR(-ENOMEM);
452	}
453
454	return ctx;
455}
456
457/**
458 * ext4_fname_crypto_round_up() -
459 *
460 * Return: The next multiple of block size
461 */
462u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
463{
464	return ((size+blksize-1)/blksize)*blksize;
465}
466
467/**
468 * ext4_fname_crypto_namelen_on_disk() -
469 */
470int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,
471				      u32 namelen)
472{
473	u32 ciphertext_len;
474	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);
475
476	if (ctx == NULL)
477		return -EIO;
478	if (!(ctx->has_valid_key))
479		return -EACCES;
480	ciphertext_len = (namelen < EXT4_CRYPTO_BLOCK_SIZE) ?
481		EXT4_CRYPTO_BLOCK_SIZE : namelen;
482	ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
483	ciphertext_len = (ciphertext_len > ctx->lim)
484			? ctx->lim : ciphertext_len;
485	return (int) ciphertext_len;
486}
487
488/**
489 * ext4_fname_crypto_alloc_obuff() -
490 *
491 * Allocates an output buffer that is sufficient for the crypto operation
492 * specified by the context and the direction.
493 */
494int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,
495				   u32 ilen, struct ext4_str *crypto_str)
496{
497	unsigned int olen;
498	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);
499
500	if (!ctx)
501		return -EIO;
502	if (padding < EXT4_CRYPTO_BLOCK_SIZE)
503		padding = EXT4_CRYPTO_BLOCK_SIZE;
504	olen = ext4_fname_crypto_round_up(ilen, padding);
505	crypto_str->len = olen;
506	if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
507		olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;
508	/* Allocated buffer can hold one more character to null-terminate the
509	 * string */
510	crypto_str->name = kmalloc(olen+1, GFP_NOFS);
511	if (!(crypto_str->name))
512		return -ENOMEM;
513	return 0;
514}
515
516/**
517 * ext4_fname_crypto_free_buffer() -
518 *
519 * Frees the buffer allocated for crypto operation.
520 */
521void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str)
522{
523	if (!crypto_str)
524		return;
525	kfree(crypto_str->name);
526	crypto_str->name = NULL;
527}
528
529/**
530 * ext4_fname_disk_to_usr() - converts a filename from disk space to user space
531 */
532int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
533			    struct dx_hash_info *hinfo,
534			    const struct ext4_str *iname,
535			    struct ext4_str *oname)
536{
537	char buf[24];
538	int ret;
539
540	if (ctx == NULL)
541		return -EIO;
542	if (iname->len < 3) {
543		/*Check for . and .. */
544		if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') {
545			oname->name[0] = '.';
546			oname->name[iname->len-1] = '.';
547			oname->len = iname->len;
548			return oname->len;
549		}
550	}
551	if (ctx->has_valid_key)
552		return ext4_fname_decrypt(ctx, iname, oname);
553
554	if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {
555		ret = digest_encode(iname->name, iname->len, oname->name);
556		oname->len = ret;
557		return ret;
558	}
559	if (hinfo) {
560		memcpy(buf, &hinfo->hash, 4);
561		memcpy(buf+4, &hinfo->minor_hash, 4);
562	} else
563		memset(buf, 0, 8);
564	memcpy(buf + 8, iname->name + iname->len - 16, 16);
565	oname->name[0] = '_';
566	ret = digest_encode(buf, 24, oname->name+1);
567	oname->len = ret + 1;
568	return ret + 1;
569}
570
571int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
572			   struct dx_hash_info *hinfo,
573			   const struct ext4_dir_entry_2 *de,
574			   struct ext4_str *oname)
575{
576	struct ext4_str iname = {.name = (unsigned char *) de->name,
577				 .len = de->name_len };
578
579	return _ext4_fname_disk_to_usr(ctx, hinfo, &iname, oname);
580}
581
582
583/**
584 * ext4_fname_usr_to_disk() - converts a filename from user space to disk space
585 */
586int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
587			   const struct qstr *iname,
588			   struct ext4_str *oname)
589{
590	int res;
591
592	if (ctx == NULL)
593		return -EIO;
594	if (iname->len < 3) {
595		/*Check for . and .. */
596		if (iname->name[0] == '.' &&
597				iname->name[iname->len-1] == '.') {
598			oname->name[0] = '.';
599			oname->name[iname->len-1] = '.';
600			oname->len = iname->len;
601			return oname->len;
602		}
603	}
604	if (ctx->has_valid_key) {
605		res = ext4_fname_encrypt(ctx, iname, oname);
606		return res;
607	}
608	/* Without a proper key, a user is not allowed to modify the filenames
609	 * in a directory. Consequently, a user space name cannot be mapped to
610	 * a disk-space name */
611	return -EACCES;
612}
613
614/*
615 * Calculate the htree hash from a filename from user space
616 */
617int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,
618			    const struct qstr *iname,
619			    struct dx_hash_info *hinfo)
620{
621	struct ext4_str tmp;
622	int ret = 0;
623	char buf[EXT4_FNAME_CRYPTO_DIGEST_SIZE+1];
624
625	if (!ctx ||
626	    ((iname->name[0] == '.') &&
627	     ((iname->len == 1) ||
628	      ((iname->name[1] == '.') && (iname->len == 2))))) {
629		ext4fs_dirhash(iname->name, iname->len, hinfo);
630		return 0;
631	}
632
633	if (!ctx->has_valid_key && iname->name[0] == '_') {
634		if (iname->len != 33)
635			return -ENOENT;
636		ret = digest_decode(iname->name+1, iname->len, buf);
637		if (ret != 24)
638			return -ENOENT;
639		memcpy(&hinfo->hash, buf, 4);
640		memcpy(&hinfo->minor_hash, buf + 4, 4);
641		return 0;
642	}
643
644	if (!ctx->has_valid_key && iname->name[0] != '_') {
645		if (iname->len > 43)
646			return -ENOENT;
647		ret = digest_decode(iname->name, iname->len, buf);
648		ext4fs_dirhash(buf, ret, hinfo);
649		return 0;
650	}
651
652	/* First encrypt the plaintext name */
653	ret = ext4_fname_crypto_alloc_buffer(ctx, iname->len, &tmp);
654	if (ret < 0)
655		return ret;
656
657	ret = ext4_fname_encrypt(ctx, iname, &tmp);
658	if (ret >= 0) {
659		ext4fs_dirhash(tmp.name, tmp.len, hinfo);
660		ret = 0;
661	}
662
663	ext4_fname_crypto_free_buffer(&tmp);
664	return ret;
665}
666
667int ext4_fname_match(struct ext4_fname_crypto_ctx *ctx, struct ext4_str *cstr,
668		     int len, const char * const name,
669		     struct ext4_dir_entry_2 *de)
670{
671	int ret = -ENOENT;
672	int bigname = (*name == '_');
673
674	if (ctx->has_valid_key) {
675		if (cstr->name == NULL) {
676			struct qstr istr;
677
678			ret = ext4_fname_crypto_alloc_buffer(ctx, len, cstr);
679			if (ret < 0)
680				goto errout;
681			istr.name = name;
682			istr.len = len;
683			ret = ext4_fname_encrypt(ctx, &istr, cstr);
684			if (ret < 0)
685				goto errout;
686		}
687	} else {
688		if (cstr->name == NULL) {
689			cstr->name = kmalloc(32, GFP_KERNEL);
690			if (cstr->name == NULL)
691				return -ENOMEM;
692			if ((bigname && (len != 33)) ||
693			    (!bigname && (len > 43)))
694				goto errout;
695			ret = digest_decode(name+bigname, len-bigname,
696					    cstr->name);
697			if (ret < 0) {
698				ret = -ENOENT;
699				goto errout;
700			}
701			cstr->len = ret;
702		}
703		if (bigname) {
704			if (de->name_len < 16)
705				return 0;
706			ret = memcmp(de->name + de->name_len - 16,
707				     cstr->name + 8, 16);
708			return (ret == 0) ? 1 : 0;
709		}
710	}
711	if (de->name_len != cstr->len)
712		return 0;
713	ret = memcmp(de->name, cstr->name, cstr->len);
714	return (ret == 0) ? 1 : 0;
715errout:
716	kfree(cstr->name);
717	cstr->name = NULL;
718	return ret;
719}
720