summaryrefslogtreecommitdiff
path: root/fs/ceph/crypto.c
blob: e1f31b86fd4801c6e71f77352d1cd1067e03690b (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
// SPDX-License-Identifier: GPL-2.0
/*
 * The base64 encode/decode code was copied from fscrypt:
 * Copyright (C) 2015, Google, Inc.
 * Copyright (C) 2015, Motorola Mobility
 * Written by Uday Savagaonkar, 2014.
 * Modified by Jaegeuk Kim, 2015.
 */
#include <linux/ceph/ceph_debug.h>
#include <linux/xattr.h>
#include <linux/fscrypt.h>
#include <linux/ceph/striper.h>

#include "super.h"
#include "mds_client.h"
#include "crypto.h"

/*
 * The base64url encoding used by fscrypt includes the '_' character, which may
 * cause problems in snapshot names (which can not start with '_').  Thus, we
 * used the base64 encoding defined for IMAP mailbox names (RFC 3501) instead,
 * which replaces '-' and '_' by '+' and ','.
 */
static const char base64_table[65] =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";

int ceph_base64_encode(const u8 *src, int srclen, char *dst)
{
	u32 ac = 0;
	int bits = 0;
	int i;
	char *cp = dst;

	for (i = 0; i < srclen; i++) {
		ac = (ac << 8) | src[i];
		bits += 8;
		do {
			bits -= 6;
			*cp++ = base64_table[(ac >> bits) & 0x3f];
		} while (bits >= 6);
	}
	if (bits)
		*cp++ = base64_table[(ac << (6 - bits)) & 0x3f];
	return cp - dst;
}

int ceph_base64_decode(const char *src, int srclen, u8 *dst)
{
	u32 ac = 0;
	int bits = 0;
	int i;
	u8 *bp = dst;

	for (i = 0; i < srclen; i++) {
		const char *p = strchr(base64_table, src[i]);

		if (p == NULL || src[i] == 0)
			return -1;
		ac = (ac << 6) | (p - base64_table);
		bits += 6;
		if (bits >= 8) {
			bits -= 8;
			*bp++ = (u8)(ac >> bits);
		}
	}
	if (ac & ((1 << bits) - 1))
		return -1;
	return bp - dst;
}

static int ceph_crypt_get_context(struct inode *inode, void *ctx, size_t len)
{
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_fscrypt_auth *cfa = (struct ceph_fscrypt_auth *)ci->fscrypt_auth;
	u32 ctxlen;

	/* Non existent or too short? */
	if (!cfa || (ci->fscrypt_auth_len < (offsetof(struct ceph_fscrypt_auth, cfa_blob) + 1)))
		return -ENOBUFS;

	/* Some format we don't recognize? */
	if (le32_to_cpu(cfa->cfa_version) != CEPH_FSCRYPT_AUTH_VERSION)
		return -ENOBUFS;

	ctxlen = le32_to_cpu(cfa->cfa_blob_len);
	if (len < ctxlen)
		return -ERANGE;

	memcpy(ctx, cfa->cfa_blob, ctxlen);
	return ctxlen;
}

static int ceph_crypt_set_context(struct inode *inode, const void *ctx,
				  size_t len, void *fs_data)
{
	int ret;
	struct iattr attr = { };
	struct ceph_iattr cia = { };
	struct ceph_fscrypt_auth *cfa;

	WARN_ON_ONCE(fs_data);

	if (len > FSCRYPT_SET_CONTEXT_MAX_SIZE)
		return -EINVAL;

	cfa = kzalloc(sizeof(*cfa), GFP_KERNEL);
	if (!cfa)
		return -ENOMEM;

	cfa->cfa_version = cpu_to_le32(CEPH_FSCRYPT_AUTH_VERSION);
	cfa->cfa_blob_len = cpu_to_le32(len);
	memcpy(cfa->cfa_blob, ctx, len);

	cia.fscrypt_auth = cfa;

	ret = __ceph_setattr(inode, &attr, &cia);
	if (ret == 0)
		inode_set_flags(inode, S_ENCRYPTED, S_ENCRYPTED);
	kfree(cia.fscrypt_auth);
	return ret;
}

static bool ceph_crypt_empty_dir(struct inode *inode)
{
	struct ceph_inode_info *ci = ceph_inode(inode);

	return ci->i_rsubdirs + ci->i_rfiles == 1;
}

static const union fscrypt_policy *ceph_get_dummy_policy(struct super_block *sb)
{
	return ceph_sb_to_client(sb)->fsc_dummy_enc_policy.policy;
}

static struct fscrypt_operations ceph_fscrypt_ops = {
	.get_context		= ceph_crypt_get_context,
	.set_context		= ceph_crypt_set_context,
	.get_dummy_policy	= ceph_get_dummy_policy,
	.empty_dir		= ceph_crypt_empty_dir,
};

void ceph_fscrypt_set_ops(struct super_block *sb)
{
	fscrypt_set_ops(sb, &ceph_fscrypt_ops);
}

void ceph_fscrypt_free_dummy_policy(struct ceph_fs_client *fsc)
{
	fscrypt_free_dummy_policy(&fsc->fsc_dummy_enc_policy);
}

int ceph_fscrypt_prepare_context(struct inode *dir, struct inode *inode,
				 struct ceph_acl_sec_ctx *as)
{
	int ret, ctxsize;
	bool encrypted = false;
	struct ceph_inode_info *ci = ceph_inode(inode);

	ret = fscrypt_prepare_new_inode(dir, inode, &encrypted);
	if (ret)
		return ret;
	if (!encrypted)
		return 0;

	as->fscrypt_auth = kzalloc(sizeof(*as->fscrypt_auth), GFP_KERNEL);
	if (!as->fscrypt_auth)
		return -ENOMEM;

	ctxsize = fscrypt_context_for_new_inode(as->fscrypt_auth->cfa_blob,
						inode);
	if (ctxsize < 0)
		return ctxsize;

	as->fscrypt_auth->cfa_version = cpu_to_le32(CEPH_FSCRYPT_AUTH_VERSION);
	as->fscrypt_auth->cfa_blob_len = cpu_to_le32(ctxsize);

	WARN_ON_ONCE(ci->fscrypt_auth);
	kfree(ci->fscrypt_auth);
	ci->fscrypt_auth_len = ceph_fscrypt_auth_len(as->fscrypt_auth);
	ci->fscrypt_auth = kmemdup(as->fscrypt_auth, ci->fscrypt_auth_len,
				   GFP_KERNEL);
	if (!ci->fscrypt_auth)
		return -ENOMEM;

	inode->i_flags |= S_ENCRYPTED;

	return 0;
}

void ceph_fscrypt_as_ctx_to_req(struct ceph_mds_request *req,
				struct ceph_acl_sec_ctx *as)
{
	swap(req->r_fscrypt_auth, as->fscrypt_auth);
}

/*
 * User-created snapshots can't start with '_'.  Snapshots that start with this
 * character are special (hint: there aren't real snapshots) and use the
 * following format:
 *
 *   _<SNAPSHOT-NAME>_<INODE-NUMBER>
 *
 * where:
 *  - <SNAPSHOT-NAME> - the real snapshot name that may need to be decrypted,
 *  - <INODE-NUMBER> - the inode number (in decimal) for the actual snapshot
 *
 * This function parses these snapshot names and returns the inode
 * <INODE-NUMBER>.  'name_len' will also bet set with the <SNAPSHOT-NAME>
 * length.
 */
static struct inode *parse_longname(const struct inode *parent,
				    const char *name, int *name_len)
{
	struct inode *dir = NULL;
	struct ceph_vino vino = { .snap = CEPH_NOSNAP };
	char *inode_number;
	char *name_end;
	int orig_len = *name_len;
	int ret = -EIO;

	/* Skip initial '_' */
	name++;
	name_end = strrchr(name, '_');
	if (!name_end) {
		dout("Failed to parse long snapshot name: %s\n", name);
		return ERR_PTR(-EIO);
	}
	*name_len = (name_end - name);
	if (*name_len <= 0) {
		pr_err("Failed to parse long snapshot name\n");
		return ERR_PTR(-EIO);
	}

	/* Get the inode number */
	inode_number = kmemdup_nul(name_end + 1,
				   orig_len - *name_len - 2,
				   GFP_KERNEL);
	if (!inode_number)
		return ERR_PTR(-ENOMEM);
	ret = kstrtou64(inode_number, 10, &vino.ino);
	if (ret) {
		dout("Failed to parse inode number: %s\n", name);
		dir = ERR_PTR(ret);
		goto out;
	}

	/* And finally the inode */
	dir = ceph_find_inode(parent->i_sb, vino);
	if (!dir) {
		/* This can happen if we're not mounting cephfs on the root */
		dir = ceph_get_inode(parent->i_sb, vino, NULL);
		if (IS_ERR(dir))
			dout("Can't find inode %s (%s)\n", inode_number, name);
	}

out:
	kfree(inode_number);
	return dir;
}

int ceph_encode_encrypted_dname(struct inode *parent, struct qstr *d_name,
				char *buf)
{
	struct inode *dir = parent;
	struct qstr iname;
	u32 len;
	int name_len;
	int elen;
	int ret;
	u8 *cryptbuf = NULL;

	iname.name = d_name->name;
	name_len = d_name->len;

	/* Handle the special case of snapshot names that start with '_' */
	if ((ceph_snap(dir) == CEPH_SNAPDIR) && (name_len > 0) &&
	    (iname.name[0] == '_')) {
		dir = parse_longname(parent, iname.name, &name_len);
		if (IS_ERR(dir))
			return PTR_ERR(dir);
		iname.name++; /* skip initial '_' */
	}
	iname.len = name_len;

	if (!fscrypt_has_encryption_key(dir)) {
		memcpy(buf, d_name->name, d_name->len);
		elen = d_name->len;
		goto out;
	}

	/*
	 * Convert cleartext d_name to ciphertext. If result is longer than
	 * CEPH_NOHASH_NAME_MAX, sha256 the remaining bytes
	 *
	 * See: fscrypt_setup_filename
	 */
	if (!fscrypt_fname_encrypted_size(dir, iname.len, NAME_MAX, &len)) {
		elen = -ENAMETOOLONG;
		goto out;
	}

	/* Allocate a buffer appropriate to hold the result */
	cryptbuf = kmalloc(len > CEPH_NOHASH_NAME_MAX ? NAME_MAX : len,
			   GFP_KERNEL);
	if (!cryptbuf) {
		elen = -ENOMEM;
		goto out;
	}

	ret = fscrypt_fname_encrypt(dir, &iname, cryptbuf, len);
	if (ret) {
		elen = ret;
		goto out;
	}

	/* hash the end if the name is long enough */
	if (len > CEPH_NOHASH_NAME_MAX) {
		u8 hash[SHA256_DIGEST_SIZE];
		u8 *extra = cryptbuf + CEPH_NOHASH_NAME_MAX;

		/*
		 * hash the extra bytes and overwrite crypttext beyond that
		 * point with it
		 */
		sha256(extra, len - CEPH_NOHASH_NAME_MAX, hash);
		memcpy(extra, hash, SHA256_DIGEST_SIZE);
		len = CEPH_NOHASH_NAME_MAX + SHA256_DIGEST_SIZE;
	}

	/* base64 encode the encrypted name */
	elen = ceph_base64_encode(cryptbuf, len, buf);
	dout("base64-encoded ciphertext name = %.*s\n", elen, buf);

	/* To understand the 240 limit, see CEPH_NOHASH_NAME_MAX comments */
	WARN_ON(elen > 240);
	if ((elen > 0) && (dir != parent)) {
		char tmp_buf[NAME_MAX];

		elen = snprintf(tmp_buf, sizeof(tmp_buf), "_%.*s_%ld",
				elen, buf, dir->i_ino);
		memcpy(buf, tmp_buf, elen);
	}

out:
	kfree(cryptbuf);
	if (dir != parent) {
		if ((dir->i_state & I_NEW))
			discard_new_inode(dir);
		else
			iput(dir);
	}
	return elen;
}

int ceph_encode_encrypted_fname(struct inode *parent, struct dentry *dentry,
				char *buf)
{
	WARN_ON_ONCE(!fscrypt_has_encryption_key(parent));

	return ceph_encode_encrypted_dname(parent, &dentry->d_name, buf);
}

/**
 * ceph_fname_to_usr - convert a filename for userland presentation
 * @fname: ceph_fname to be converted
 * @tname: temporary name buffer to use for conversion (may be NULL)
 * @oname: where converted name should be placed
 * @is_nokey: set to true if key wasn't available during conversion (may be NULL)
 *
 * Given a filename (usually from the MDS), format it for presentation to
 * userland. If @parent is not encrypted, just pass it back as-is.
 *
 * Otherwise, base64 decode the string, and then ask fscrypt to format it
 * for userland presentation.
 *
 * Returns 0 on success or negative error code on error.
 */
int ceph_fname_to_usr(const struct ceph_fname *fname, struct fscrypt_str *tname,
		      struct fscrypt_str *oname, bool *is_nokey)
{
	struct inode *dir = fname->dir;
	struct fscrypt_str _tname = FSTR_INIT(NULL, 0);
	struct fscrypt_str iname;
	char *name = fname->name;
	int name_len = fname->name_len;
	int ret;

	/* Sanity check that the resulting name will fit in the buffer */
	if (fname->name_len > NAME_MAX || fname->ctext_len > NAME_MAX)
		return -EIO;

	/* Handle the special case of snapshot names that start with '_' */
	if ((ceph_snap(dir) == CEPH_SNAPDIR) && (name_len > 0) &&
	    (name[0] == '_')) {
		dir = parse_longname(dir, name, &name_len);
		if (IS_ERR(dir))
			return PTR_ERR(dir);
		name++; /* skip initial '_' */
	}

	if (!IS_ENCRYPTED(dir)) {
		oname->name = fname->name;
		oname->len = fname->name_len;
		ret = 0;
		goto out_inode;
	}

	ret = ceph_fscrypt_prepare_readdir(dir);
	if (ret)
		goto out_inode;

	/*
	 * Use the raw dentry name as sent by the MDS instead of
	 * generating a nokey name via fscrypt.
	 */
	if (!fscrypt_has_encryption_key(dir)) {
		if (fname->no_copy)
			oname->name = fname->name;
		else
			memcpy(oname->name, fname->name, fname->name_len);
		oname->len = fname->name_len;
		if (is_nokey)
			*is_nokey = true;
		ret = 0;
		goto out_inode;
	}

	if (fname->ctext_len == 0) {
		int declen;

		if (!tname) {
			ret = fscrypt_fname_alloc_buffer(NAME_MAX, &_tname);
			if (ret)
				goto out_inode;
			tname = &_tname;
		}

		declen = ceph_base64_decode(name, name_len, tname->name);
		if (declen <= 0) {
			ret = -EIO;
			goto out;
		}
		iname.name = tname->name;
		iname.len = declen;
	} else {
		iname.name = fname->ctext;
		iname.len = fname->ctext_len;
	}

	ret = fscrypt_fname_disk_to_usr(dir, 0, 0, &iname, oname);
	if (!ret && (dir != fname->dir)) {
		char tmp_buf[CEPH_BASE64_CHARS(NAME_MAX)];

		name_len = snprintf(tmp_buf, sizeof(tmp_buf), "_%.*s_%ld",
				    oname->len, oname->name, dir->i_ino);
		memcpy(oname->name, tmp_buf, name_len);
		oname->len = name_len;
	}

out:
	fscrypt_fname_free_buffer(&_tname);
out_inode:
	if ((dir != fname->dir) && !IS_ERR(dir)) {
		if ((dir->i_state & I_NEW))
			discard_new_inode(dir);
		else
			iput(dir);
	}
	return ret;
}

/**
 * ceph_fscrypt_prepare_readdir - simple __fscrypt_prepare_readdir() wrapper
 * @dir: directory inode for readdir prep
 *
 * Simple wrapper around __fscrypt_prepare_readdir() that will mark directory as
 * non-complete if this call results in having the directory unlocked.
 *
 * Returns:
 *     1 - if directory was locked and key is now loaded (i.e. dir is unlocked)
 *     0 - if directory is still locked
 *   < 0 - if __fscrypt_prepare_readdir() fails
 */
int ceph_fscrypt_prepare_readdir(struct inode *dir)
{
	bool had_key = fscrypt_has_encryption_key(dir);
	int err;

	if (!IS_ENCRYPTED(dir))
		return 0;

	err = __fscrypt_prepare_readdir(dir);
	if (err)
		return err;
	if (!had_key && fscrypt_has_encryption_key(dir)) {
		/* directory just got unlocked, mark it as not complete */
		ceph_dir_clear_complete(dir);
		return 1;
	}
	return 0;
}

int ceph_fscrypt_decrypt_block_inplace(const struct inode *inode,
				  struct page *page, unsigned int len,
				  unsigned int offs, u64 lblk_num)
{
	dout("%s: len %u offs %u blk %llu\n", __func__, len, offs, lblk_num);
	return fscrypt_decrypt_block_inplace(inode, page, len, offs, lblk_num);
}

int ceph_fscrypt_encrypt_block_inplace(const struct inode *inode,
				  struct page *page, unsigned int len,
				  unsigned int offs, u64 lblk_num,
				  gfp_t gfp_flags)
{
	dout("%s: len %u offs %u blk %llu\n", __func__, len, offs, lblk_num);
	return fscrypt_encrypt_block_inplace(inode, page, len, offs, lblk_num,
					     gfp_flags);
}

/**
 * ceph_fscrypt_decrypt_pages - decrypt an array of pages
 * @inode: pointer to inode associated with these pages
 * @page: pointer to page array
 * @off: offset into the file that the read data starts
 * @len: max length to decrypt
 *
 * Decrypt an array of fscrypt'ed pages and return the amount of
 * data decrypted. Any data in the page prior to the start of the
 * first complete block in the read is ignored. Any incomplete
 * crypto blocks at the end of the array are ignored (and should
 * probably be zeroed by the caller).
 *
 * Returns the length of the decrypted data or a negative errno.
 */
int ceph_fscrypt_decrypt_pages(struct inode *inode, struct page **page,
			       u64 off, int len)
{
	int i, num_blocks;
	u64 baseblk = off >> CEPH_FSCRYPT_BLOCK_SHIFT;
	int ret = 0;

	/*
	 * We can't deal with partial blocks on an encrypted file, so mask off
	 * the last bit.
	 */
	num_blocks = ceph_fscrypt_blocks(off, len & CEPH_FSCRYPT_BLOCK_MASK);

	/* Decrypt each block */
	for (i = 0; i < num_blocks; ++i) {
		int blkoff = i << CEPH_FSCRYPT_BLOCK_SHIFT;
		int pgidx = blkoff >> PAGE_SHIFT;
		unsigned int pgoffs = offset_in_page(blkoff);
		int fret;

		fret = ceph_fscrypt_decrypt_block_inplace(inode, page[pgidx],
				CEPH_FSCRYPT_BLOCK_SIZE, pgoffs,
				baseblk + i);
		if (fret < 0) {
			if (ret == 0)
				ret = fret;
			break;
		}
		ret += CEPH_FSCRYPT_BLOCK_SIZE;
	}
	return ret;
}

/**
 * ceph_fscrypt_decrypt_extents: decrypt received extents in given buffer
 * @inode: inode associated with pages being decrypted
 * @page: pointer to page array
 * @off: offset into the file that the data in page[0] starts
 * @map: pointer to extent array
 * @ext_cnt: length of extent array
 *
 * Given an extent map and a page array, decrypt the received data in-place,
 * skipping holes. Returns the offset into buffer of end of last decrypted
 * block.
 */
int ceph_fscrypt_decrypt_extents(struct inode *inode, struct page **page,
				 u64 off, struct ceph_sparse_extent *map,
				 u32 ext_cnt)
{
	int i, ret = 0;
	struct ceph_inode_info *ci = ceph_inode(inode);
	u64 objno, objoff;
	u32 xlen;

	/* Nothing to do for empty array */
	if (ext_cnt == 0) {
		dout("%s: empty array, ret 0\n", __func__);
		return 0;
	}

	ceph_calc_file_object_mapping(&ci->i_layout, off, map[0].len,
				      &objno, &objoff, &xlen);

	for (i = 0; i < ext_cnt; ++i) {
		struct ceph_sparse_extent *ext = &map[i];
		int pgsoff = ext->off - objoff;
		int pgidx = pgsoff >> PAGE_SHIFT;
		int fret;

		if ((ext->off | ext->len) & ~CEPH_FSCRYPT_BLOCK_MASK) {
			pr_warn("%s: bad encrypted sparse extent idx %d off %llx len %llx\n",
				__func__, i, ext->off, ext->len);
			return -EIO;
		}
		fret = ceph_fscrypt_decrypt_pages(inode, &page[pgidx],
						 off + pgsoff, ext->len);
		dout("%s: [%d] 0x%llx~0x%llx fret %d\n", __func__, i,
				ext->off, ext->len, fret);
		if (fret < 0) {
			if (ret == 0)
				ret = fret;
			break;
		}
		ret = pgsoff + fret;
	}
	dout("%s: ret %d\n", __func__, ret);
	return ret;
}

/**
 * ceph_fscrypt_encrypt_pages - encrypt an array of pages
 * @inode: pointer to inode associated with these pages
 * @page: pointer to page array
 * @off: offset into the file that the data starts
 * @len: max length to encrypt
 * @gfp: gfp flags to use for allocation
 *
 * Decrypt an array of cleartext pages and return the amount of
 * data encrypted. Any data in the page prior to the start of the
 * first complete block in the read is ignored. Any incomplete
 * crypto blocks at the end of the array are ignored.
 *
 * Returns the length of the encrypted data or a negative errno.
 */
int ceph_fscrypt_encrypt_pages(struct inode *inode, struct page **page, u64 off,
				int len, gfp_t gfp)
{
	int i, num_blocks;
	u64 baseblk = off >> CEPH_FSCRYPT_BLOCK_SHIFT;
	int ret = 0;

	/*
	 * We can't deal with partial blocks on an encrypted file, so mask off
	 * the last bit.
	 */
	num_blocks = ceph_fscrypt_blocks(off, len & CEPH_FSCRYPT_BLOCK_MASK);

	/* Encrypt each block */
	for (i = 0; i < num_blocks; ++i) {
		int blkoff = i << CEPH_FSCRYPT_BLOCK_SHIFT;
		int pgidx = blkoff >> PAGE_SHIFT;
		unsigned int pgoffs = offset_in_page(blkoff);
		int fret;

		fret = ceph_fscrypt_encrypt_block_inplace(inode, page[pgidx],
				CEPH_FSCRYPT_BLOCK_SIZE, pgoffs,
				baseblk + i, gfp);
		if (fret < 0) {
			if (ret == 0)
				ret = fret;
			break;
		}
		ret += CEPH_FSCRYPT_BLOCK_SIZE;
	}
	return ret;
}