xref: /linux/net/sunrpc/auth_gss/gss_krb5_wrap.c (revision 74ce1896c6c65b2f8cccbf59162d542988835835)
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 	s32			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 = get_seconds();
176 
177 	blocksize = crypto_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 	spin_lock(&krb5_seq_lock);
232 	seq_send = kctx->seq_send++;
233 	spin_unlock(&krb5_seq_lock);
234 
235 	/* XXX would probably be more efficient to compute checksum
236 	 * and encrypt at the same time: */
237 	if ((krb5_make_seq_num(kctx, kctx->seq, kctx->initiate ? 0 : 0xff,
238 			       seq_send, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8)))
239 		return GSS_S_FAILURE;
240 
241 	if (kctx->enctype == ENCTYPE_ARCFOUR_HMAC) {
242 		struct crypto_skcipher *cipher;
243 		int err;
244 		cipher = crypto_alloc_skcipher(kctx->gk5e->encrypt_name, 0,
245 					       CRYPTO_ALG_ASYNC);
246 		if (IS_ERR(cipher))
247 			return GSS_S_FAILURE;
248 
249 		krb5_rc4_setup_enc_key(kctx, cipher, seq_send);
250 
251 		err = gss_encrypt_xdr_buf(cipher, buf,
252 					  offset + headlen - conflen, pages);
253 		crypto_free_skcipher(cipher);
254 		if (err)
255 			return GSS_S_FAILURE;
256 	} else {
257 		if (gss_encrypt_xdr_buf(kctx->enc, buf,
258 					offset + headlen - conflen, pages))
259 			return GSS_S_FAILURE;
260 	}
261 
262 	return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
263 }
264 
265 static u32
266 gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
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 	s32			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 
285 	dprintk("RPC:       gss_unwrap_kerberos\n");
286 
287 	ptr = (u8 *)buf->head[0].iov_base + offset;
288 	if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
289 					buf->len - offset))
290 		return GSS_S_DEFECTIVE_TOKEN;
291 
292 	if ((ptr[0] != ((KG_TOK_WRAP_MSG >> 8) & 0xff)) ||
293 	    (ptr[1] !=  (KG_TOK_WRAP_MSG & 0xff)))
294 		return GSS_S_DEFECTIVE_TOKEN;
295 
296 	/* XXX sanity-check bodysize?? */
297 
298 	/* get the sign and seal algorithms */
299 
300 	signalg = ptr[2] + (ptr[3] << 8);
301 	if (signalg != kctx->gk5e->signalg)
302 		return GSS_S_DEFECTIVE_TOKEN;
303 
304 	sealalg = ptr[4] + (ptr[5] << 8);
305 	if (sealalg != kctx->gk5e->sealalg)
306 		return GSS_S_DEFECTIVE_TOKEN;
307 
308 	if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
309 		return GSS_S_DEFECTIVE_TOKEN;
310 
311 	/*
312 	 * Data starts after token header and checksum.  ptr points
313 	 * to the beginning of the token header
314 	 */
315 	crypt_offset = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) -
316 					(unsigned char *)buf->head[0].iov_base;
317 
318 	/*
319 	 * Need plaintext seqnum to derive encryption key for arcfour-hmac
320 	 */
321 	if (krb5_get_seq_num(kctx, ptr + GSS_KRB5_TOK_HDR_LEN,
322 			     ptr + 8, &direction, &seqnum))
323 		return GSS_S_BAD_SIG;
324 
325 	if ((kctx->initiate && direction != 0xff) ||
326 	    (!kctx->initiate && direction != 0))
327 		return GSS_S_BAD_SIG;
328 
329 	if (kctx->enctype == ENCTYPE_ARCFOUR_HMAC) {
330 		struct crypto_skcipher *cipher;
331 		int err;
332 
333 		cipher = crypto_alloc_skcipher(kctx->gk5e->encrypt_name, 0,
334 					       CRYPTO_ALG_ASYNC);
335 		if (IS_ERR(cipher))
336 			return GSS_S_FAILURE;
337 
338 		krb5_rc4_setup_enc_key(kctx, cipher, seqnum);
339 
340 		err = gss_decrypt_xdr_buf(cipher, buf, crypt_offset);
341 		crypto_free_skcipher(cipher);
342 		if (err)
343 			return GSS_S_DEFECTIVE_TOKEN;
344 	} else {
345 		if (gss_decrypt_xdr_buf(kctx->enc, buf, crypt_offset))
346 			return GSS_S_DEFECTIVE_TOKEN;
347 	}
348 
349 	if (kctx->gk5e->keyed_cksum)
350 		cksumkey = kctx->cksum;
351 	else
352 		cksumkey = NULL;
353 
354 	if (make_checksum(kctx, ptr, 8, buf, crypt_offset,
355 					cksumkey, KG_USAGE_SEAL, &md5cksum))
356 		return GSS_S_FAILURE;
357 
358 	if (memcmp(md5cksum.data, ptr + GSS_KRB5_TOK_HDR_LEN,
359 						kctx->gk5e->cksumlength))
360 		return GSS_S_BAD_SIG;
361 
362 	/* it got through unscathed.  Make sure the context is unexpired */
363 
364 	now = get_seconds();
365 
366 	if (now > kctx->endtime)
367 		return GSS_S_CONTEXT_EXPIRED;
368 
369 	/* do sequencing checks */
370 
371 	/* Copy the data back to the right position.  XXX: Would probably be
372 	 * better to copy and encrypt at the same time. */
373 
374 	blocksize = crypto_skcipher_blocksize(kctx->enc);
375 	data_start = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) +
376 					conflen;
377 	orig_start = buf->head[0].iov_base + offset;
378 	data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
379 	memmove(orig_start, data_start, data_len);
380 	buf->head[0].iov_len -= (data_start - orig_start);
381 	buf->len -= (data_start - orig_start);
382 
383 	if (gss_krb5_remove_padding(buf, blocksize))
384 		return GSS_S_DEFECTIVE_TOKEN;
385 
386 	return GSS_S_COMPLETE;
387 }
388 
389 /*
390  * We can shift data by up to LOCAL_BUF_LEN bytes in a pass.  If we need
391  * to do more than that, we shift repeatedly.  Kevin Coffman reports
392  * seeing 28 bytes as the value used by Microsoft clients and servers
393  * with AES, so this constant is chosen to allow handling 28 in one pass
394  * without using too much stack space.
395  *
396  * If that proves to a problem perhaps we could use a more clever
397  * algorithm.
398  */
399 #define LOCAL_BUF_LEN 32u
400 
401 static void rotate_buf_a_little(struct xdr_buf *buf, unsigned int shift)
402 {
403 	char head[LOCAL_BUF_LEN];
404 	char tmp[LOCAL_BUF_LEN];
405 	unsigned int this_len, i;
406 
407 	BUG_ON(shift > LOCAL_BUF_LEN);
408 
409 	read_bytes_from_xdr_buf(buf, 0, head, shift);
410 	for (i = 0; i + shift < buf->len; i += LOCAL_BUF_LEN) {
411 		this_len = min(LOCAL_BUF_LEN, buf->len - (i + shift));
412 		read_bytes_from_xdr_buf(buf, i+shift, tmp, this_len);
413 		write_bytes_to_xdr_buf(buf, i, tmp, this_len);
414 	}
415 	write_bytes_to_xdr_buf(buf, buf->len - shift, head, shift);
416 }
417 
418 static void _rotate_left(struct xdr_buf *buf, unsigned int shift)
419 {
420 	int shifted = 0;
421 	int this_shift;
422 
423 	shift %= buf->len;
424 	while (shifted < shift) {
425 		this_shift = min(shift - shifted, LOCAL_BUF_LEN);
426 		rotate_buf_a_little(buf, this_shift);
427 		shifted += this_shift;
428 	}
429 }
430 
431 static void rotate_left(u32 base, struct xdr_buf *buf, unsigned int shift)
432 {
433 	struct xdr_buf subbuf;
434 
435 	xdr_buf_subsegment(buf, &subbuf, base, buf->len - base);
436 	_rotate_left(&subbuf, shift);
437 }
438 
439 static u32
440 gss_wrap_kerberos_v2(struct krb5_ctx *kctx, u32 offset,
441 		     struct xdr_buf *buf, struct page **pages)
442 {
443 	int		blocksize;
444 	u8		*ptr, *plainhdr;
445 	s32		now;
446 	u8		flags = 0x00;
447 	__be16		*be16ptr;
448 	__be64		*be64ptr;
449 	u32		err;
450 
451 	dprintk("RPC:       %s\n", __func__);
452 
453 	if (kctx->gk5e->encrypt_v2 == NULL)
454 		return GSS_S_FAILURE;
455 
456 	/* make room for gss token header */
457 	if (xdr_extend_head(buf, offset, GSS_KRB5_TOK_HDR_LEN))
458 		return GSS_S_FAILURE;
459 
460 	/* construct gss token header */
461 	ptr = plainhdr = buf->head[0].iov_base + offset;
462 	*ptr++ = (unsigned char) ((KG2_TOK_WRAP>>8) & 0xff);
463 	*ptr++ = (unsigned char) (KG2_TOK_WRAP & 0xff);
464 
465 	if ((kctx->flags & KRB5_CTX_FLAG_INITIATOR) == 0)
466 		flags |= KG2_TOKEN_FLAG_SENTBYACCEPTOR;
467 	if ((kctx->flags & KRB5_CTX_FLAG_ACCEPTOR_SUBKEY) != 0)
468 		flags |= KG2_TOKEN_FLAG_ACCEPTORSUBKEY;
469 	/* We always do confidentiality in wrap tokens */
470 	flags |= KG2_TOKEN_FLAG_SEALED;
471 
472 	*ptr++ = flags;
473 	*ptr++ = 0xff;
474 	be16ptr = (__be16 *)ptr;
475 
476 	blocksize = crypto_skcipher_blocksize(kctx->acceptor_enc);
477 	*be16ptr++ = 0;
478 	/* "inner" token header always uses 0 for RRC */
479 	*be16ptr++ = 0;
480 
481 	be64ptr = (__be64 *)be16ptr;
482 	spin_lock(&krb5_seq_lock);
483 	*be64ptr = cpu_to_be64(kctx->seq_send64++);
484 	spin_unlock(&krb5_seq_lock);
485 
486 	err = (*kctx->gk5e->encrypt_v2)(kctx, offset, buf, pages);
487 	if (err)
488 		return err;
489 
490 	now = get_seconds();
491 	return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
492 }
493 
494 static u32
495 gss_unwrap_kerberos_v2(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
496 {
497 	s32		now;
498 	u8		*ptr;
499 	u8		flags = 0x00;
500 	u16		ec, rrc;
501 	int		err;
502 	u32		headskip, tailskip;
503 	u8		decrypted_hdr[GSS_KRB5_TOK_HDR_LEN];
504 	unsigned int	movelen;
505 
506 
507 	dprintk("RPC:       %s\n", __func__);
508 
509 	if (kctx->gk5e->decrypt_v2 == NULL)
510 		return GSS_S_FAILURE;
511 
512 	ptr = buf->head[0].iov_base + offset;
513 
514 	if (be16_to_cpu(*((__be16 *)ptr)) != KG2_TOK_WRAP)
515 		return GSS_S_DEFECTIVE_TOKEN;
516 
517 	flags = ptr[2];
518 	if ((!kctx->initiate && (flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)) ||
519 	    (kctx->initiate && !(flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)))
520 		return GSS_S_BAD_SIG;
521 
522 	if ((flags & KG2_TOKEN_FLAG_SEALED) == 0) {
523 		dprintk("%s: token missing expected sealed flag\n", __func__);
524 		return GSS_S_DEFECTIVE_TOKEN;
525 	}
526 
527 	if (ptr[3] != 0xff)
528 		return GSS_S_DEFECTIVE_TOKEN;
529 
530 	ec = be16_to_cpup((__be16 *)(ptr + 4));
531 	rrc = be16_to_cpup((__be16 *)(ptr + 6));
532 
533 	/*
534 	 * NOTE: the sequence number at ptr + 8 is skipped, rpcsec_gss
535 	 * doesn't want it checked; see page 6 of rfc 2203.
536 	 */
537 
538 	if (rrc != 0)
539 		rotate_left(offset + 16, buf, rrc);
540 
541 	err = (*kctx->gk5e->decrypt_v2)(kctx, offset, buf,
542 					&headskip, &tailskip);
543 	if (err)
544 		return GSS_S_FAILURE;
545 
546 	/*
547 	 * Retrieve the decrypted gss token header and verify
548 	 * it against the original
549 	 */
550 	err = read_bytes_from_xdr_buf(buf,
551 				buf->len - GSS_KRB5_TOK_HDR_LEN - tailskip,
552 				decrypted_hdr, GSS_KRB5_TOK_HDR_LEN);
553 	if (err) {
554 		dprintk("%s: error %u getting decrypted_hdr\n", __func__, err);
555 		return GSS_S_FAILURE;
556 	}
557 	if (memcmp(ptr, decrypted_hdr, 6)
558 				|| memcmp(ptr + 8, decrypted_hdr + 8, 8)) {
559 		dprintk("%s: token hdr, plaintext hdr mismatch!\n", __func__);
560 		return GSS_S_FAILURE;
561 	}
562 
563 	/* do sequencing checks */
564 
565 	/* it got through unscathed.  Make sure the context is unexpired */
566 	now = get_seconds();
567 	if (now > kctx->endtime)
568 		return GSS_S_CONTEXT_EXPIRED;
569 
570 	/*
571 	 * Move the head data back to the right position in xdr_buf.
572 	 * We ignore any "ec" data since it might be in the head or
573 	 * the tail, and we really don't need to deal with it.
574 	 * Note that buf->head[0].iov_len may indicate the available
575 	 * head buffer space rather than that actually occupied.
576 	 */
577 	movelen = min_t(unsigned int, buf->head[0].iov_len, buf->len);
578 	movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip;
579 	BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen >
580 							buf->head[0].iov_len);
581 	memmove(ptr, ptr + GSS_KRB5_TOK_HDR_LEN + headskip, movelen);
582 	buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;
583 	buf->len -= GSS_KRB5_TOK_HDR_LEN + headskip;
584 
585 	/* Trim off the trailing "extra count" and checksum blob */
586 	xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip);
587 	return GSS_S_COMPLETE;
588 }
589 
590 u32
591 gss_wrap_kerberos(struct gss_ctx *gctx, int offset,
592 		  struct xdr_buf *buf, struct page **pages)
593 {
594 	struct krb5_ctx	*kctx = gctx->internal_ctx_id;
595 
596 	switch (kctx->enctype) {
597 	default:
598 		BUG();
599 	case ENCTYPE_DES_CBC_RAW:
600 	case ENCTYPE_DES3_CBC_RAW:
601 	case ENCTYPE_ARCFOUR_HMAC:
602 		return gss_wrap_kerberos_v1(kctx, offset, buf, pages);
603 	case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
604 	case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
605 		return gss_wrap_kerberos_v2(kctx, offset, buf, pages);
606 	}
607 }
608 
609 u32
610 gss_unwrap_kerberos(struct gss_ctx *gctx, int offset, struct xdr_buf *buf)
611 {
612 	struct krb5_ctx	*kctx = gctx->internal_ctx_id;
613 
614 	switch (kctx->enctype) {
615 	default:
616 		BUG();
617 	case ENCTYPE_DES_CBC_RAW:
618 	case ENCTYPE_DES3_CBC_RAW:
619 	case ENCTYPE_ARCFOUR_HMAC:
620 		return gss_unwrap_kerberos_v1(kctx, offset, buf);
621 	case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
622 	case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
623 		return gss_unwrap_kerberos_v2(kctx, offset, buf);
624 	}
625 }
626 
627