summaryrefslogtreecommitdiffstats
path: root/net/sunrpc/auth_gss/gss_krb5_wrap.c
blob: 962fa84e6db114f95790f8d6bba485fe226ed43e (plain) (blame)
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
/*
 * COPYRIGHT (c) 2008
 * The Regents of the University of Michigan
 * ALL RIGHTS RESERVED
 *
 * Permission is granted to use, copy, create derivative works
 * and redistribute this software and such derivative works
 * for any purpose, so long as the name of The University of
 * Michigan is not used in any advertising or publicity
 * pertaining to the use of distribution of this software
 * without specific, written prior authorization.  If the
 * above copyright notice or any other identification of the
 * University of Michigan is included in any copy of any
 * portion of this software, then the disclaimer below must
 * also be included.
 *
 * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
 * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
 * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
 * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
 * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
 * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
 * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
 * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
 * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGES.
 */

#include <crypto/skcipher.h>
#include <linux/types.h>
#include <linux/jiffies.h>
#include <linux/sunrpc/gss_krb5.h>
#include <linux/random.h>
#include <linux/pagemap.h>

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
# define RPCDBG_FACILITY	RPCDBG_AUTH
#endif

static inline int
gss_krb5_padding(int blocksize, int length)
{
	return blocksize - (length % blocksize);
}

static inline void
gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize)
{
	int padding = gss_krb5_padding(blocksize, buf->len - offset);
	char *p;
	struct kvec *iov;

	if (buf->page_len || buf->tail[0].iov_len)
		iov = &buf->tail[0];
	else
		iov = &buf->head[0];
	p = iov->iov_base + iov->iov_len;
	iov->iov_len += padding;
	buf->len += padding;
	memset(p, padding, padding);
}

static inline int
gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize)
{
	u8 *ptr;
	u8 pad;
	size_t len = buf->len;

	if (len <= buf->head[0].iov_len) {
		pad = *(u8 *)(buf->head[0].iov_base + len - 1);
		if (pad > buf->head[0].iov_len)
			return -EINVAL;
		buf->head[0].iov_len -= pad;
		goto out;
	} else
		len -= buf->head[0].iov_len;
	if (len <= buf->page_len) {
		unsigned int last = (buf->page_base + len - 1)
					>>PAGE_SHIFT;
		unsigned int offset = (buf->page_base + len - 1)
					& (PAGE_SIZE - 1);
		ptr = kmap_atomic(buf->pages[last]);
		pad = *(ptr + offset);
		kunmap_atomic(ptr);
		goto out;
	} else
		len -= buf->page_len;
	BUG_ON(len > buf->tail[0].iov_len);
	pad = *(u8 *)(buf->tail[0].iov_base + len - 1);
out:
	/* XXX: NOTE: we do not adjust the page lengths--they represent
	 * a range of data in the real filesystem page cache, and we need
	 * to know that range so the xdr code can properly place read data.
	 * However adjusting the head length, as we do above, is harmless.
	 * In the case of a request that fits into a single page, the server
	 * also uses length and head length together to determine the original
	 * start of the request to copy the request for deferal; so it's
	 * easier on the server if we adjust head and tail length in tandem.
	 * It's not really a problem that we don't fool with the page and
	 * tail lengths, though--at worst badly formed xdr might lead the
	 * server to attempt to parse the padding.
	 * XXX: Document all these weird requirements for gss mechanism
	 * wrap/unwrap functions. */
	if (pad > blocksize)
		return -EINVAL;
	if (buf->len > pad)
		buf->len -= pad;
	else
		return -EINVAL;
	return 0;
}

void
gss_krb5_make_confounder(char *p, u32 conflen)
{
	static u64 i = 0;
	u64 *q = (u64 *)p;

	/* rfc1964 claims this should be "random".  But all that's really
	 * necessary is that it be unique.  And not even that is necessary in
	 * our case since our "gssapi" implementation exists only to support
	 * rpcsec_gss, so we know that the only buffers we will ever encrypt
	 * already begin with a unique sequence number.  Just to hedge my bets
	 * I'll make a half-hearted attempt at something unique, but ensuring
	 * uniqueness would mean worrying about atomicity and rollover, and I
	 * don't care enough. */

	/* initialize to random value */
	if (i == 0) {
		i = prandom_u32();
		i = (i << 32) | prandom_u32();
	}

	switch (conflen) {
	case 16:
		*q++ = i++;
		/* fall through */
	case 8:
		*q++ = i++;
		break;
	default:
		BUG();
	}
}

/* Assumptions: the head and tail of inbuf are ours to play with.
 * The pages, however, may be real pages in the page cache and we replace
 * them with scratch pages from **pages before writing to them. */
/* XXX: obviously the above should be documentation of wrap interface,
 * and shouldn't be in this kerberos-specific file. */

/* XXX factor out common code with seal/unseal. */

static u32
gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
		struct xdr_buf *buf, struct page **pages)
{
	char			cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
	struct xdr_netobj	md5cksum = {.len = sizeof(cksumdata),
					    .data = cksumdata};
	int			blocksize = 0, plainlen;
	unsigned char		*ptr, *msg_start;
	s32			now;
	int			headlen;
	struct page		**tmp_pages;
	u32			seq_send;
	u8			*cksumkey;
	u32			conflen = kctx->gk5e->conflen;

	dprintk("RPC:       %s\n", __func__);

	now = get_seconds();

	blocksize = crypto_sync_skcipher_blocksize(kctx->enc);
	gss_krb5_add_padding(buf, offset, blocksize);
	BUG_ON((buf->len - offset) % blocksize);
	plainlen = conflen + buf->len - offset;

	headlen = g_token_size(&kctx->mech_used,
		GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength + plainlen) -
		(buf->len - offset);

	ptr = buf->head[0].iov_base + offset;
	/* shift data to make room for header. */
	xdr_extend_head(buf, offset, headlen);

	/* XXX Would be cleverer to encrypt while copying. */
	BUG_ON((buf->len - offset - headlen) % blocksize);

	g_make_token_header(&kctx->mech_used,
				GSS_KRB5_TOK_HDR_LEN +
				kctx->gk5e->cksumlength + plainlen, &ptr);


	/* ptr now at header described in rfc 1964, section 1.2.1: */
	ptr[0] = (unsigned char) ((KG_TOK_WRAP_MSG >> 8) & 0xff);
	ptr[1] = (unsigned char) (KG_TOK_WRAP_MSG & 0xff);

	msg_start = ptr + GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength;

	/*
	 * signalg and sealalg are stored as if they were converted from LE
	 * to host endian, even though they're opaque pairs of bytes according
	 * to the RFC.
	 */
	*(__le16 *)(ptr + 2) = cpu_to_le16(kctx->gk5e->signalg);
	*(__le16 *)(ptr + 4) = cpu_to_le16(kctx->gk5e->sealalg);
	ptr[6] = 0xff;
	ptr[7] = 0xff;

	gss_krb5_make_confounder(msg_start, conflen);

	if (kctx->gk5e->keyed_cksum)
		cksumkey = kctx->cksum;
	else
		cksumkey = NULL;

	/* XXXJBF: UGH!: */
	tmp_pages = buf->pages;
	buf->pages = pages;
	if (make_checksum(kctx, ptr, 8, buf, offset + headlen - conflen,
					cksumkey, KG_USAGE_SEAL, &md5cksum))
		return GSS_S_FAILURE;
	buf->pages = tmp_pages;

	memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data, md5cksum.len);

	seq_send = gss_seq_send_fetch_and_inc(kctx);

	/* XXX would probably be more efficient to compute checksum
	 * and encrypt at the same time: */
	if ((krb5_make_seq_num(kctx, kctx->seq, kctx->initiate ? 0 : 0xff,
			       seq_send, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8)))
		return GSS_S_FAILURE;

	if (kctx->enctype == ENCTYPE_ARCFOUR_HMAC) {
		struct crypto_sync_skcipher *cipher;
		int err;
		cipher = crypto_alloc_sync_skcipher(kctx->gk5e->encrypt_name,
						    0, 0);
		if (IS_ERR(cipher))
			return GSS_S_FAILURE;

		krb5_rc4_setup_enc_key(kctx, cipher, seq_send);

		err = gss_encrypt_xdr_buf(cipher, buf,
					  offset + headlen - conflen, pages);
		crypto_free_sync_skcipher(cipher);
		if (err)
			return GSS_S_FAILURE;
	} else {
		if (gss_encrypt_xdr_buf(kctx->enc, buf,
					offset + headlen - conflen, pages))
			return GSS_S_FAILURE;
	}

	return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
}

static u32
gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
{
	int			signalg;
	int			sealalg;
	char			cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
	struct xdr_netobj	md5cksum = {.len = sizeof(cksumdata),
					    .data = cksumdata};
	s32			now;
	int			direction;
	s32			seqnum;
	unsigned char		*ptr;
	int			bodysize;
	void			*data_start, *orig_start;
	int			data_len;
	int			blocksize;
	u32			conflen = kctx->gk5e->conflen;
	int			crypt_offset;
	u8			*cksumkey;

	dprintk("RPC:       gss_unwrap_kerberos\n");

	ptr = (u8 *)buf->head[0].iov_base + offset;
	if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
					buf->len - offset))
		return GSS_S_DEFECTIVE_TOKEN;

	if ((ptr[0] != ((KG_TOK_WRAP_MSG >> 8) & 0xff)) ||
	    (ptr[1] !=  (KG_TOK_WRAP_MSG & 0xff)))
		return GSS_S_DEFECTIVE_TOKEN;

	/* XXX sanity-check bodysize?? */

	/* get the sign and seal algorithms */

	signalg = ptr[2] + (ptr[3] << 8);
	if (signalg != kctx->gk5e->signalg)
		return GSS_S_DEFECTIVE_TOKEN;

	sealalg = ptr[4] + (ptr[5] << 8);
	if (sealalg != kctx->gk5e->sealalg)
		return GSS_S_DEFECTIVE_TOKEN;

	if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
		return GSS_S_DEFECTIVE_TOKEN;

	/*
	 * Data starts after token header and checksum.  ptr points
	 * to the beginning of the token header
	 */
	crypt_offset = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) -
					(unsigned char *)buf->head[0].iov_base;

	/*
	 * Need plaintext seqnum to derive encryption key for arcfour-hmac
	 */
	if (krb5_get_seq_num(kctx, ptr + GSS_KRB5_TOK_HDR_LEN,
			     ptr + 8, &direction, &seqnum))
		return GSS_S_BAD_SIG;

	if ((kctx->initiate && direction != 0xff) ||
	    (!kctx->initiate && direction != 0))
		return GSS_S_BAD_SIG;

	if (kctx->enctype == ENCTYPE_ARCFOUR_HMAC) {
		struct crypto_sync_skcipher *cipher;
		int err;

		cipher = crypto_alloc_sync_skcipher(kctx->gk5e->encrypt_name,
						    0, 0);
		if (IS_ERR(cipher))
			return GSS_S_FAILURE;

		krb5_rc4_setup_enc_key(kctx, cipher, seqnum);

		err = gss_decrypt_xdr_buf(cipher, buf, crypt_offset);
		crypto_free_sync_skcipher(cipher);
		if (err)
			return GSS_S_DEFECTIVE_TOKEN;
	} else {
		if (gss_decrypt_xdr_buf(kctx->enc, buf, crypt_offset))
			return GSS_S_DEFECTIVE_TOKEN;
	}

	if (kctx->gk5e->keyed_cksum)
		cksumkey = kctx->cksum;
	else
		cksumkey = NULL;

	if (make_checksum(kctx, ptr, 8, buf, crypt_offset,
					cksumkey, KG_USAGE_SEAL, &md5cksum))
		return GSS_S_FAILURE;

	if (memcmp(md5cksum.data, ptr + GSS_KRB5_TOK_HDR_LEN,
						kctx->gk5e->cksumlength))
		return GSS_S_BAD_SIG;

	/* it got through unscathed.  Make sure the context is unexpired */

	now = get_seconds();

	if (now > kctx->endtime)
		return GSS_S_CONTEXT_EXPIRED;

	/* do sequencing checks */

	/* Copy the data back to the right position.  XXX: Would probably be
	 * better to copy and encrypt at the same time. */

	blocksize = crypto_sync_skcipher_blocksize(kctx->enc);
	data_start = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) +
					conflen;
	orig_start = buf->head[0].iov_base + offset;
	data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
	memmove(orig_start, data_start, data_len);
	buf->head[0].iov_len -= (data_start - orig_start);
	buf->len -= (data_start - orig_start);

	if (gss_krb5_remove_padding(buf, blocksize))
		return GSS_S_DEFECTIVE_TOKEN;

	return GSS_S_COMPLETE;
}

/*
 * We can shift data by up to LOCAL_BUF_LEN bytes in a pass.  If we need
 * to do more than that, we shift repeatedly.  Kevin Coffman reports
 * seeing 28 bytes as the value used by Microsoft clients and servers
 * with AES, so this constant is chosen to allow handling 28 in one pass
 * without using too much stack space.
 *
 * If that proves to a problem perhaps we could use a more clever
 * algorithm.
 */
#define LOCAL_BUF_LEN 32u

static void rotate_buf_a_little(struct xdr_buf *buf, unsigned int shift)
{
	char head[LOCAL_BUF_LEN];
	char tmp[LOCAL_BUF_LEN];
	unsigned int this_len, i;

	BUG_ON(shift > LOCAL_BUF_LEN);

	read_bytes_from_xdr_buf(buf, 0, head, shift);
	for (i = 0; i + shift < buf->len; i += LOCAL_BUF_LEN) {
		this_len = min(LOCAL_BUF_LEN, buf->len - (i + shift));
		read_bytes_from_xdr_buf(buf, i+shift, tmp, this_len);
		write_bytes_to_xdr_buf(buf, i, tmp, this_len);
	}
	write_bytes_to_xdr_buf(buf, buf->len - shift, head, shift);
}

static void _rotate_left(struct xdr_buf *buf, unsigned int shift)
{
	int shifted = 0;
	int this_shift;

	shift %= buf->len;
	while (shifted < shift) {
		this_shift = min(shift - shifted, LOCAL_BUF_LEN);
		rotate_buf_a_little(buf, this_shift);
		shifted += this_shift;
	}
}

static void rotate_left(u32 base, struct xdr_buf *buf, unsigned int shift)
{
	struct xdr_buf subbuf;

	xdr_buf_subsegment(buf, &subbuf, base, buf->len - base);
	_rotate_left(&subbuf, shift);
}

static u32
gss_wrap_kerberos_v2(struct krb5_ctx *kctx, u32 offset,
		     struct xdr_buf *buf, struct page **pages)
{
	u8		*ptr, *plainhdr;
	s32		now;
	u8		flags = 0x00;
	__be16		*be16ptr;
	__be64		*be64ptr;
	u32		err;

	dprintk("RPC:       %s\n", __func__);

	if (kctx->gk5e->encrypt_v2 == NULL)
		return GSS_S_FAILURE;

	/* make room for gss token header */
	if (xdr_extend_head(buf, offset, GSS_KRB5_TOK_HDR_LEN))
		return GSS_S_FAILURE;

	/* construct gss token header */
	ptr = plainhdr = buf->head[0].iov_base + offset;
	*ptr++ = (unsigned char) ((KG2_TOK_WRAP>>8) & 0xff);
	*ptr++ = (unsigned char) (KG2_TOK_WRAP & 0xff);

	if ((kctx->flags & KRB5_CTX_FLAG_INITIATOR) == 0)
		flags |= KG2_TOKEN_FLAG_SENTBYACCEPTOR;
	if ((kctx->flags & KRB5_CTX_FLAG_ACCEPTOR_SUBKEY) != 0)
		flags |= KG2_TOKEN_FLAG_ACCEPTORSUBKEY;
	/* We always do confidentiality in wrap tokens */
	flags |= KG2_TOKEN_FLAG_SEALED;

	*ptr++ = flags;
	*ptr++ = 0xff;
	be16ptr = (__be16 *)ptr;

	*be16ptr++ = 0;
	/* "inner" token header always uses 0 for RRC */
	*be16ptr++ = 0;

	be64ptr = (__be64 *)be16ptr;
	*be64ptr = cpu_to_be64(gss_seq_send64_fetch_and_inc(kctx));

	err = (*kctx->gk5e->encrypt_v2)(kctx, offset, buf, pages);
	if (err)
		return err;

	now = get_seconds();
	return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
}

static u32
gss_unwrap_kerberos_v2(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
{
	s32		now;
	u8		*ptr;
	u8		flags = 0x00;
	u16		ec, rrc;
	int		err;
	u32		headskip, tailskip;
	u8		decrypted_hdr[GSS_KRB5_TOK_HDR_LEN];
	unsigned int	movelen;


	dprintk("RPC:       %s\n", __func__);

	if (kctx->gk5e->decrypt_v2 == NULL)
		return GSS_S_FAILURE;

	ptr = buf->head[0].iov_base + offset;

	if (be16_to_cpu(*((__be16 *)ptr)) != KG2_TOK_WRAP)
		return GSS_S_DEFECTIVE_TOKEN;

	flags = ptr[2];
	if ((!kctx->initiate && (flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)) ||
	    (kctx->initiate && !(flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)))
		return GSS_S_BAD_SIG;

	if ((flags & KG2_TOKEN_FLAG_SEALED) == 0) {
		dprintk("%s: token missing expected sealed flag\n", __func__);
		return GSS_S_DEFECTIVE_TOKEN;
	}

	if (ptr[3] != 0xff)
		return GSS_S_DEFECTIVE_TOKEN;

	ec = be16_to_cpup((__be16 *)(ptr + 4));
	rrc = be16_to_cpup((__be16 *)(ptr + 6));

	/*
	 * NOTE: the sequence number at ptr + 8 is skipped, rpcsec_gss
	 * doesn't want it checked; see page 6 of rfc 2203.
	 */

	if (rrc != 0)
		rotate_left(offset + 16, buf, rrc);

	err = (*kctx->gk5e->decrypt_v2)(kctx, offset, buf,
					&headskip, &tailskip);
	if (err)
		return GSS_S_FAILURE;

	/*
	 * Retrieve the decrypted gss token header and verify
	 * it against the original
	 */
	err = read_bytes_from_xdr_buf(buf,
				buf->len - GSS_KRB5_TOK_HDR_LEN - tailskip,
				decrypted_hdr, GSS_KRB5_TOK_HDR_LEN);
	if (err) {
		dprintk("%s: error %u getting decrypted_hdr\n", __func__, err);
		return GSS_S_FAILURE;
	}
	if (memcmp(ptr, decrypted_hdr, 6)
				|| memcmp(ptr + 8, decrypted_hdr + 8, 8)) {
		dprintk("%s: token hdr, plaintext hdr mismatch!\n", __func__);
		return GSS_S_FAILURE;
	}

	/* do sequencing checks */

	/* it got through unscathed.  Make sure the context is unexpired */
	now = get_seconds();
	if (now > kctx->endtime)
		return GSS_S_CONTEXT_EXPIRED;

	/*
	 * Move the head data back to the right position in xdr_buf.
	 * We ignore any "ec" data since it might be in the head or
	 * the tail, and we really don't need to deal with it.
	 * Note that buf->head[0].iov_len may indicate the available
	 * head buffer space rather than that actually occupied.
	 */
	movelen = min_t(unsigned int, buf->head[0].iov_len, buf->len);
	movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip;
	BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen >
							buf->head[0].iov_len);
	memmove(ptr, ptr + GSS_KRB5_TOK_HDR_LEN + headskip, movelen);
	buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;
	buf->len -= GSS_KRB5_TOK_HDR_LEN + headskip;

	/* Trim off the trailing "extra count" and checksum blob */
	xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip);
	return GSS_S_COMPLETE;
}

u32
gss_wrap_kerberos(struct gss_ctx *gctx, int offset,
		  struct xdr_buf *buf, struct page **pages)
{
	struct krb5_ctx	*kctx = gctx->internal_ctx_id;

	switch (kctx->enctype) {
	default:
		BUG();
	case ENCTYPE_DES_CBC_RAW:
	case ENCTYPE_DES3_CBC_RAW:
	case ENCTYPE_ARCFOUR_HMAC:
		return gss_wrap_kerberos_v1(kctx, offset, buf, pages);
	case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
	case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
		return gss_wrap_kerberos_v2(kctx, offset, buf, pages);
	}
}

u32
gss_unwrap_kerberos(struct gss_ctx *gctx, int offset, struct xdr_buf *buf)
{
	struct krb5_ctx	*kctx = gctx->internal_ctx_id;

	switch (kctx->enctype) {
	default:
		BUG();
	case ENCTYPE_DES_CBC_RAW:
	case ENCTYPE_DES3_CBC_RAW:
	case ENCTYPE_ARCFOUR_HMAC:
		return gss_unwrap_kerberos_v1(kctx, offset, buf);
	case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
	case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
		return gss_unwrap_kerberos_v2(kctx, offset, buf);
	}
}