1 /*
2  * COPYRIGHT (c) 2008
3  * The Regents of the University of Michigan
4  * ALL RIGHTS RESERVED
5  *
6  * Permission is granted to use, copy, create derivative works
7  * and redistribute this software and such derivative works
8  * for any purpose, so long as the name of The University of
9  * Michigan is not used in any advertising or publicity
10  * pertaining to the use of distribution of this software
11  * without specific, written prior authorization.  If the
12  * above copyright notice or any other identification of the
13  * University of Michigan is included in any copy of any
14  * portion of this software, then the disclaimer below must
15  * also be included.
16  *
17  * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
18  * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
19  * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
20  * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
21  * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
22  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
23  * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
24  * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
25  * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
26  * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
27  * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
28  * SUCH DAMAGES.
29  */
30 
31 #include <crypto/skcipher.h>
32 #include <linux/types.h>
33 #include <linux/jiffies.h>
34 #include <linux/sunrpc/gss_krb5.h>
35 #include <linux/random.h>
36 #include <linux/pagemap.h>
37 
38 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
39 # define RPCDBG_FACILITY	RPCDBG_AUTH
40 #endif
41 
42 static inline int
43 gss_krb5_padding(int blocksize, int length)
44 {
45 	return blocksize - (length % blocksize);
46 }
47 
48 static inline void
49 gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize)
50 {
51 	int padding = gss_krb5_padding(blocksize, buf->len - offset);
52 	char *p;
53 	struct kvec *iov;
54 
55 	if (buf->page_len || buf->tail[0].iov_len)
56 		iov = &buf->tail[0];
57 	else
58 		iov = &buf->head[0];
59 	p = iov->iov_base + iov->iov_len;
60 	iov->iov_len += padding;
61 	buf->len += padding;
62 	memset(p, padding, padding);
63 }
64 
65 static inline int
66 gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize)
67 {
68 	u8 *ptr;
69 	u8 pad;
70 	size_t len = buf->len;
71 
72 	if (len <= buf->head[0].iov_len) {
73 		pad = *(u8 *)(buf->head[0].iov_base + len - 1);
74 		if (pad > buf->head[0].iov_len)
75 			return -EINVAL;
76 		buf->head[0].iov_len -= pad;
77 		goto out;
78 	} else
79 		len -= buf->head[0].iov_len;
80 	if (len <= buf->page_len) {
81 		unsigned int last = (buf->page_base + len - 1)
82 					>>PAGE_SHIFT;
83 		unsigned int offset = (buf->page_base + len - 1)
84 					& (PAGE_SIZE - 1);
85 		ptr = kmap_atomic(buf->pages[last]);
86 		pad = *(ptr + offset);
87 		kunmap_atomic(ptr);
88 		goto out;
89 	} else
90 		len -= buf->page_len;
91 	BUG_ON(len > buf->tail[0].iov_len);
92 	pad = *(u8 *)(buf->tail[0].iov_base + len - 1);
93 out:
94 	/* XXX: NOTE: we do not adjust the page lengths--they represent
95 	 * a range of data in the real filesystem page cache, and we need
96 	 * to know that range so the xdr code can properly place read data.
97 	 * However adjusting the head length, as we do above, is harmless.
98 	 * In the case of a request that fits into a single page, the server
99 	 * also uses length and head length together to determine the original
100 	 * start of the request to copy the request for deferal; so it's
101 	 * easier on the server if we adjust head and tail length in tandem.
102 	 * It's not really a problem that we don't fool with the page and
103 	 * tail lengths, though--at worst badly formed xdr might lead the
104 	 * server to attempt to parse the padding.
105 	 * XXX: Document all these weird requirements for gss mechanism
106 	 * wrap/unwrap functions. */
107 	if (pad > blocksize)
108 		return -EINVAL;
109 	if (buf->len > pad)
110 		buf->len -= pad;
111 	else
112 		return -EINVAL;
113 	return 0;
114 }
115 
116 void
117 gss_krb5_make_confounder(char *p, u32 conflen)
118 {
119 	static u64 i = 0;
120 	u64 *q = (u64 *)p;
121 
122 	/* rfc1964 claims this should be "random".  But all that's really
123 	 * necessary is that it be unique.  And not even that is necessary in
124 	 * our case since our "gssapi" implementation exists only to support
125 	 * rpcsec_gss, so we know that the only buffers we will ever encrypt
126 	 * already begin with a unique sequence number.  Just to hedge my bets
127 	 * I'll make a half-hearted attempt at something unique, but ensuring
128 	 * uniqueness would mean worrying about atomicity and rollover, and I
129 	 * don't care enough. */
130 
131 	/* initialize to random value */
132 	if (i == 0) {
133 		i = prandom_u32();
134 		i = (i << 32) | prandom_u32();
135 	}
136 
137 	switch (conflen) {
138 	case 16:
139 		*q++ = i++;
140 		/* fall through */
141 	case 8:
142 		*q++ = i++;
143 		break;
144 	default:
145 		BUG();
146 	}
147 }
148 
149 /* Assumptions: the head and tail of inbuf are ours to play with.
150  * The pages, however, may be real pages in the page cache and we replace
151  * them with scratch pages from **pages before writing to them. */
152 /* XXX: obviously the above should be documentation of wrap interface,
153  * and shouldn't be in this kerberos-specific file. */
154 
155 /* XXX factor out common code with seal/unseal. */
156 
157 static u32
158 gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
159 		struct xdr_buf *buf, struct page **pages)
160 {
161 	char			cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
162 	struct xdr_netobj	md5cksum = {.len = sizeof(cksumdata),
163 					    .data = cksumdata};
164 	int			blocksize = 0, plainlen;
165 	unsigned char		*ptr, *msg_start;
166 	time64_t		now;
167 	int			headlen;
168 	struct page		**tmp_pages;
169 	u32			seq_send;
170 	u8			*cksumkey;
171 	u32			conflen = kctx->gk5e->conflen;
172 
173 	dprintk("RPC:       %s\n", __func__);
174 
175 	now = ktime_get_real_seconds();
176 
177 	blocksize = crypto_sync_skcipher_blocksize(kctx->enc);
178 	gss_krb5_add_padding(buf, offset, blocksize);
179 	BUG_ON((buf->len - offset) % blocksize);
180 	plainlen = conflen + buf->len - offset;
181 
182 	headlen = g_token_size(&kctx->mech_used,
183 		GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength + plainlen) -
184 		(buf->len - offset);
185 
186 	ptr = buf->head[0].iov_base + offset;
187 	/* shift data to make room for header. */
188 	xdr_extend_head(buf, offset, headlen);
189 
190 	/* XXX Would be cleverer to encrypt while copying. */
191 	BUG_ON((buf->len - offset - headlen) % blocksize);
192 
193 	g_make_token_header(&kctx->mech_used,
194 				GSS_KRB5_TOK_HDR_LEN +
195 				kctx->gk5e->cksumlength + plainlen, &ptr);
196 
197 
198 	/* ptr now at header described in rfc 1964, section 1.2.1: */
199 	ptr[0] = (unsigned char) ((KG_TOK_WRAP_MSG >> 8) & 0xff);
200 	ptr[1] = (unsigned char) (KG_TOK_WRAP_MSG & 0xff);
201 
202 	msg_start = ptr + GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength;
203 
204 	/*
205 	 * signalg and sealalg are stored as if they were converted from LE
206 	 * to host endian, even though they're opaque pairs of bytes according
207 	 * to the RFC.
208 	 */
209 	*(__le16 *)(ptr + 2) = cpu_to_le16(kctx->gk5e->signalg);
210 	*(__le16 *)(ptr + 4) = cpu_to_le16(kctx->gk5e->sealalg);
211 	ptr[6] = 0xff;
212 	ptr[7] = 0xff;
213 
214 	gss_krb5_make_confounder(msg_start, conflen);
215 
216 	if (kctx->gk5e->keyed_cksum)
217 		cksumkey = kctx->cksum;
218 	else
219 		cksumkey = NULL;
220 
221 	/* XXXJBF: UGH!: */
222 	tmp_pages = buf->pages;
223 	buf->pages = pages;
224 	if (make_checksum(kctx, ptr, 8, buf, offset + headlen - conflen,
225 					cksumkey, KG_USAGE_SEAL, &md5cksum))
226 		return GSS_S_FAILURE;
227 	buf->pages = tmp_pages;
228 
229 	memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data, md5cksum.len);
230 
231 	seq_send = atomic_fetch_inc(&kctx->seq_send);
232 
233 	/* XXX would probably be more efficient to compute checksum
234 	 * and encrypt at the same time: */
235 	if ((krb5_make_seq_num(kctx, kctx->seq, kctx->initiate ? 0 : 0xff,
236 			       seq_send, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8)))
237 		return GSS_S_FAILURE;
238 
239 	if (kctx->enctype == ENCTYPE_ARCFOUR_HMAC) {
240 		struct crypto_sync_skcipher *cipher;
241 		int err;
242 		cipher = crypto_alloc_sync_skcipher(kctx->gk5e->encrypt_name,
243 						    0, 0);
244 		if (IS_ERR(cipher))
245 			return GSS_S_FAILURE;
246 
247 		krb5_rc4_setup_enc_key(kctx, cipher, seq_send);
248 
249 		err = gss_encrypt_xdr_buf(cipher, buf,
250 					  offset + headlen - conflen, pages);
251 		crypto_free_sync_skcipher(cipher);
252 		if (err)
253 			return GSS_S_FAILURE;
254 	} else {
255 		if (gss_encrypt_xdr_buf(kctx->enc, buf,
256 					offset + headlen - conflen, pages))
257 			return GSS_S_FAILURE;
258 	}
259 
260 	return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
261 }
262 
263 static u32
264 gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, int len,
265 		       struct xdr_buf *buf, unsigned int *slack,
266 		       unsigned int *align)
267 {
268 	int			signalg;
269 	int			sealalg;
270 	char			cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
271 	struct xdr_netobj	md5cksum = {.len = sizeof(cksumdata),
272 					    .data = cksumdata};
273 	time64_t		now;
274 	int			direction;
275 	s32			seqnum;
276 	unsigned char		*ptr;
277 	int			bodysize;
278 	void			*data_start, *orig_start;
279 	int			data_len;
280 	int			blocksize;
281 	u32			conflen = kctx->gk5e->conflen;
282 	int			crypt_offset;
283 	u8			*cksumkey;
284 	unsigned int		saved_len = buf->len;
285 
286 	dprintk("RPC:       gss_unwrap_kerberos\n");
287 
288 	ptr = (u8 *)buf->head[0].iov_base + offset;
289 	if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
290 					len - offset))
291 		return GSS_S_DEFECTIVE_TOKEN;
292 
293 	if ((ptr[0] != ((KG_TOK_WRAP_MSG >> 8) & 0xff)) ||
294 	    (ptr[1] !=  (KG_TOK_WRAP_MSG & 0xff)))
295 		return GSS_S_DEFECTIVE_TOKEN;
296 
297 	/* XXX sanity-check bodysize?? */
298 
299 	/* get the sign and seal algorithms */
300 
301 	signalg = ptr[2] + (ptr[3] << 8);
302 	if (signalg != kctx->gk5e->signalg)
303 		return GSS_S_DEFECTIVE_TOKEN;
304 
305 	sealalg = ptr[4] + (ptr[5] << 8);
306 	if (sealalg != kctx->gk5e->sealalg)
307 		return GSS_S_DEFECTIVE_TOKEN;
308 
309 	if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
310 		return GSS_S_DEFECTIVE_TOKEN;
311 
312 	/*
313 	 * Data starts after token header and checksum.  ptr points
314 	 * to the beginning of the token header
315 	 */
316 	crypt_offset = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) -
317 					(unsigned char *)buf->head[0].iov_base;
318 
319 	/*
320 	 * Need plaintext seqnum to derive encryption key for arcfour-hmac
321 	 */
322 	if (krb5_get_seq_num(kctx, ptr + GSS_KRB5_TOK_HDR_LEN,
323 			     ptr + 8, &direction, &seqnum))
324 		return GSS_S_BAD_SIG;
325 
326 	if ((kctx->initiate && direction != 0xff) ||
327 	    (!kctx->initiate && direction != 0))
328 		return GSS_S_BAD_SIG;
329 
330 	buf->len = len;
331 	if (kctx->enctype == ENCTYPE_ARCFOUR_HMAC) {
332 		struct crypto_sync_skcipher *cipher;
333 		int err;
334 
335 		cipher = crypto_alloc_sync_skcipher(kctx->gk5e->encrypt_name,
336 						    0, 0);
337 		if (IS_ERR(cipher))
338 			return GSS_S_FAILURE;
339 
340 		krb5_rc4_setup_enc_key(kctx, cipher, seqnum);
341 
342 		err = gss_decrypt_xdr_buf(cipher, buf, crypt_offset);
343 		crypto_free_sync_skcipher(cipher);
344 		if (err)
345 			return GSS_S_DEFECTIVE_TOKEN;
346 	} else {
347 		if (gss_decrypt_xdr_buf(kctx->enc, buf, crypt_offset))
348 			return GSS_S_DEFECTIVE_TOKEN;
349 	}
350 
351 	if (kctx->gk5e->keyed_cksum)
352 		cksumkey = kctx->cksum;
353 	else
354 		cksumkey = NULL;
355 
356 	if (make_checksum(kctx, ptr, 8, buf, crypt_offset,
357 					cksumkey, KG_USAGE_SEAL, &md5cksum))
358 		return GSS_S_FAILURE;
359 
360 	if (memcmp(md5cksum.data, ptr + GSS_KRB5_TOK_HDR_LEN,
361 						kctx->gk5e->cksumlength))
362 		return GSS_S_BAD_SIG;
363 
364 	/* it got through unscathed.  Make sure the context is unexpired */
365 
366 	now = ktime_get_real_seconds();
367 
368 	if (now > kctx->endtime)
369 		return GSS_S_CONTEXT_EXPIRED;
370 
371 	/* do sequencing checks */
372 
373 	/* Copy the data back to the right position.  XXX: Would probably be
374 	 * better to copy and encrypt at the same time. */
375 
376 	blocksize = crypto_sync_skcipher_blocksize(kctx->enc);
377 	data_start = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) +
378 					conflen;
379 	orig_start = buf->head[0].iov_base + offset;
380 	data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
381 	memmove(orig_start, data_start, data_len);
382 	buf->head[0].iov_len -= (data_start - orig_start);
383 	buf->len = len - (data_start - orig_start);
384 
385 	if (gss_krb5_remove_padding(buf, blocksize))
386 		return GSS_S_DEFECTIVE_TOKEN;
387 
388 	/* slack must include room for krb5 padding */
389 	*slack = XDR_QUADLEN(saved_len - buf->len);
390 	/* The GSS blob always precedes the RPC message payload */
391 	*align = *slack;
392 	return GSS_S_COMPLETE;
393 }
394 
395 /*
396  * We can shift data by up to LOCAL_BUF_LEN bytes in a pass.  If we need
397  * to do more than that, we shift repeatedly.  Kevin Coffman reports
398  * seeing 28 bytes as the value used by Microsoft clients and servers
399  * with AES, so this constant is chosen to allow handling 28 in one pass
400  * without using too much stack space.
401  *
402  * If that proves to a problem perhaps we could use a more clever
403  * algorithm.
404  */
405 #define LOCAL_BUF_LEN 32u
406 
407 static void rotate_buf_a_little(struct xdr_buf *buf, unsigned int shift)
408 {
409 	char head[LOCAL_BUF_LEN];
410 	char tmp[LOCAL_BUF_LEN];
411 	unsigned int this_len, i;
412 
413 	BUG_ON(shift > LOCAL_BUF_LEN);
414 
415 	read_bytes_from_xdr_buf(buf, 0, head, shift);
416 	for (i = 0; i + shift < buf->len; i += LOCAL_BUF_LEN) {
417 		this_len = min(LOCAL_BUF_LEN, buf->len - (i + shift));
418 		read_bytes_from_xdr_buf(buf, i+shift, tmp, this_len);
419 		write_bytes_to_xdr_buf(buf, i, tmp, this_len);
420 	}
421 	write_bytes_to_xdr_buf(buf, buf->len - shift, head, shift);
422 }
423 
424 static void _rotate_left(struct xdr_buf *buf, unsigned int shift)
425 {
426 	int shifted = 0;
427 	int this_shift;
428 
429 	shift %= buf->len;
430 	while (shifted < shift) {
431 		this_shift = min(shift - shifted, LOCAL_BUF_LEN);
432 		rotate_buf_a_little(buf, this_shift);
433 		shifted += this_shift;
434 	}
435 }
436 
437 static void rotate_left(u32 base, struct xdr_buf *buf, unsigned int shift)
438 {
439 	struct xdr_buf subbuf;
440 
441 	xdr_buf_subsegment(buf, &subbuf, base, buf->len - base);
442 	_rotate_left(&subbuf, shift);
443 }
444 
445 static u32
446 gss_wrap_kerberos_v2(struct krb5_ctx *kctx, u32 offset,
447 		     struct xdr_buf *buf, struct page **pages)
448 {
449 	u8		*ptr, *plainhdr;
450 	time64_t	now;
451 	u8		flags = 0x00;
452 	__be16		*be16ptr;
453 	__be64		*be64ptr;
454 	u32		err;
455 
456 	dprintk("RPC:       %s\n", __func__);
457 
458 	if (kctx->gk5e->encrypt_v2 == NULL)
459 		return GSS_S_FAILURE;
460 
461 	/* make room for gss token header */
462 	if (xdr_extend_head(buf, offset, GSS_KRB5_TOK_HDR_LEN))
463 		return GSS_S_FAILURE;
464 
465 	/* construct gss token header */
466 	ptr = plainhdr = buf->head[0].iov_base + offset;
467 	*ptr++ = (unsigned char) ((KG2_TOK_WRAP>>8) & 0xff);
468 	*ptr++ = (unsigned char) (KG2_TOK_WRAP & 0xff);
469 
470 	if ((kctx->flags & KRB5_CTX_FLAG_INITIATOR) == 0)
471 		flags |= KG2_TOKEN_FLAG_SENTBYACCEPTOR;
472 	if ((kctx->flags & KRB5_CTX_FLAG_ACCEPTOR_SUBKEY) != 0)
473 		flags |= KG2_TOKEN_FLAG_ACCEPTORSUBKEY;
474 	/* We always do confidentiality in wrap tokens */
475 	flags |= KG2_TOKEN_FLAG_SEALED;
476 
477 	*ptr++ = flags;
478 	*ptr++ = 0xff;
479 	be16ptr = (__be16 *)ptr;
480 
481 	*be16ptr++ = 0;
482 	/* "inner" token header always uses 0 for RRC */
483 	*be16ptr++ = 0;
484 
485 	be64ptr = (__be64 *)be16ptr;
486 	*be64ptr = cpu_to_be64(atomic64_fetch_inc(&kctx->seq_send64));
487 
488 	err = (*kctx->gk5e->encrypt_v2)(kctx, offset, buf, pages);
489 	if (err)
490 		return err;
491 
492 	now = ktime_get_real_seconds();
493 	return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
494 }
495 
496 static u32
497 gss_unwrap_kerberos_v2(struct krb5_ctx *kctx, int offset, int len,
498 		       struct xdr_buf *buf, unsigned int *slack,
499 		       unsigned int *align)
500 {
501 	time64_t	now;
502 	u8		*ptr;
503 	u8		flags = 0x00;
504 	u16		ec, rrc;
505 	int		err;
506 	u32		headskip, tailskip;
507 	u8		decrypted_hdr[GSS_KRB5_TOK_HDR_LEN];
508 	unsigned int	movelen;
509 
510 
511 	dprintk("RPC:       %s\n", __func__);
512 
513 	if (kctx->gk5e->decrypt_v2 == NULL)
514 		return GSS_S_FAILURE;
515 
516 	ptr = buf->head[0].iov_base + offset;
517 
518 	if (be16_to_cpu(*((__be16 *)ptr)) != KG2_TOK_WRAP)
519 		return GSS_S_DEFECTIVE_TOKEN;
520 
521 	flags = ptr[2];
522 	if ((!kctx->initiate && (flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)) ||
523 	    (kctx->initiate && !(flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)))
524 		return GSS_S_BAD_SIG;
525 
526 	if ((flags & KG2_TOKEN_FLAG_SEALED) == 0) {
527 		dprintk("%s: token missing expected sealed flag\n", __func__);
528 		return GSS_S_DEFECTIVE_TOKEN;
529 	}
530 
531 	if (ptr[3] != 0xff)
532 		return GSS_S_DEFECTIVE_TOKEN;
533 
534 	ec = be16_to_cpup((__be16 *)(ptr + 4));
535 	rrc = be16_to_cpup((__be16 *)(ptr + 6));
536 
537 	/*
538 	 * NOTE: the sequence number at ptr + 8 is skipped, rpcsec_gss
539 	 * doesn't want it checked; see page 6 of rfc 2203.
540 	 */
541 
542 	if (rrc != 0)
543 		rotate_left(offset + 16, buf, rrc);
544 
545 	err = (*kctx->gk5e->decrypt_v2)(kctx, offset, len, buf,
546 					&headskip, &tailskip);
547 	if (err)
548 		return GSS_S_FAILURE;
549 
550 	/*
551 	 * Retrieve the decrypted gss token header and verify
552 	 * it against the original
553 	 */
554 	err = read_bytes_from_xdr_buf(buf,
555 				len - GSS_KRB5_TOK_HDR_LEN - tailskip,
556 				decrypted_hdr, GSS_KRB5_TOK_HDR_LEN);
557 	if (err) {
558 		dprintk("%s: error %u getting decrypted_hdr\n", __func__, err);
559 		return GSS_S_FAILURE;
560 	}
561 	if (memcmp(ptr, decrypted_hdr, 6)
562 				|| memcmp(ptr + 8, decrypted_hdr + 8, 8)) {
563 		dprintk("%s: token hdr, plaintext hdr mismatch!\n", __func__);
564 		return GSS_S_FAILURE;
565 	}
566 
567 	/* do sequencing checks */
568 
569 	/* it got through unscathed.  Make sure the context is unexpired */
570 	now = ktime_get_real_seconds();
571 	if (now > kctx->endtime)
572 		return GSS_S_CONTEXT_EXPIRED;
573 
574 	/*
575 	 * Move the head data back to the right position in xdr_buf.
576 	 * We ignore any "ec" data since it might be in the head or
577 	 * the tail, and we really don't need to deal with it.
578 	 * Note that buf->head[0].iov_len may indicate the available
579 	 * head buffer space rather than that actually occupied.
580 	 */
581 	movelen = min_t(unsigned int, buf->head[0].iov_len, len);
582 	movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip;
583 	BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen >
584 							buf->head[0].iov_len);
585 	memmove(ptr, ptr + GSS_KRB5_TOK_HDR_LEN + headskip, movelen);
586 	buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;
587 	buf->len = len - GSS_KRB5_TOK_HDR_LEN + headskip;
588 
589 	/* Trim off the trailing "extra count" and checksum blob */
590 	xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip);
591 
592 	*align = XDR_QUADLEN(GSS_KRB5_TOK_HDR_LEN + headskip);
593 	*slack = *align + XDR_QUADLEN(ec + GSS_KRB5_TOK_HDR_LEN + tailskip);
594 	return GSS_S_COMPLETE;
595 }
596 
597 u32
598 gss_wrap_kerberos(struct gss_ctx *gctx, int offset,
599 		  struct xdr_buf *buf, struct page **pages)
600 {
601 	struct krb5_ctx	*kctx = gctx->internal_ctx_id;
602 
603 	switch (kctx->enctype) {
604 	default:
605 		BUG();
606 	case ENCTYPE_DES_CBC_RAW:
607 	case ENCTYPE_DES3_CBC_RAW:
608 	case ENCTYPE_ARCFOUR_HMAC:
609 		return gss_wrap_kerberos_v1(kctx, offset, buf, pages);
610 	case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
611 	case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
612 		return gss_wrap_kerberos_v2(kctx, offset, buf, pages);
613 	}
614 }
615 
616 u32
617 gss_unwrap_kerberos(struct gss_ctx *gctx, int offset,
618 		    int len, struct xdr_buf *buf)
619 {
620 	struct krb5_ctx	*kctx = gctx->internal_ctx_id;
621 
622 	switch (kctx->enctype) {
623 	default:
624 		BUG();
625 	case ENCTYPE_DES_CBC_RAW:
626 	case ENCTYPE_DES3_CBC_RAW:
627 	case ENCTYPE_ARCFOUR_HMAC:
628 		return gss_unwrap_kerberos_v1(kctx, offset, len, buf,
629 					      &gctx->slack, &gctx->align);
630 	case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
631 	case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
632 		return gss_unwrap_kerberos_v2(kctx, offset, len, buf,
633 					      &gctx->slack, &gctx->align);
634 	}
635 }
636