1 /*-
2  * Copyright (c) 2002-2008 Sam Leffler, Errno Consulting
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24  *
25  * $FreeBSD: head/sys/net80211/ieee80211_crypto_ccmp.c 193840 2009-06-09 16:32:07Z sam $
26  */
27 
28 /*
29  * IEEE 802.11i AES-CCMP crypto support.
30  *
31  * Part of this module is derived from similar code in the Host
32  * AP driver. The code is used with the consent of the author and
33  * it's license is included below.
34  */
35 #include "opt_wlan.h"
36 
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/mbuf.h>
40 #include <sys/malloc.h>
41 #include <sys/kernel.h>
42 #include <sys/module.h>
43 
44 #include <sys/socket.h>
45 
46 #include <net/if.h>
47 #include <net/if_media.h>
48 #include <net/ethernet.h>
49 #include <net/route.h>
50 
51 #include <netproto/802_11/ieee80211_var.h>
52 
53 #include <crypto/rijndael/rijndael.h>
54 
55 #define AES_BLOCK_LEN 16
56 
57 struct ccmp_ctx {
58 	struct ieee80211vap *cc_vap;	/* for diagnostics+statistics */
59 	struct ieee80211com *cc_ic;
60 	rijndael_ctx	     cc_aes;
61 };
62 
63 static	void *ccmp_attach(struct ieee80211vap *, struct ieee80211_key *);
64 static	void ccmp_detach(struct ieee80211_key *);
65 static	int ccmp_setkey(struct ieee80211_key *);
66 static	int ccmp_encap(struct ieee80211_key *k, struct mbuf *, uint8_t keyid);
67 static	int ccmp_decap(struct ieee80211_key *, struct mbuf *, int);
68 static	int ccmp_enmic(struct ieee80211_key *, struct mbuf *, int);
69 static	int ccmp_demic(struct ieee80211_key *, struct mbuf *, int);
70 
71 static const struct ieee80211_cipher ccmp = {
72 	.ic_name	= "AES-CCM",
73 	.ic_cipher	= IEEE80211_CIPHER_AES_CCM,
74 	.ic_header	= IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN +
75 			  IEEE80211_WEP_EXTIVLEN,
76 	.ic_trailer	= IEEE80211_WEP_MICLEN,
77 	.ic_miclen	= 0,
78 	.ic_attach	= ccmp_attach,
79 	.ic_detach	= ccmp_detach,
80 	.ic_setkey	= ccmp_setkey,
81 	.ic_encap	= ccmp_encap,
82 	.ic_decap	= ccmp_decap,
83 	.ic_enmic	= ccmp_enmic,
84 	.ic_demic	= ccmp_demic,
85 };
86 
87 static	int ccmp_encrypt(struct ieee80211_key *, struct mbuf *, int hdrlen);
88 static	int ccmp_decrypt(struct ieee80211_key *, u_int64_t pn,
89 		struct mbuf *, int hdrlen);
90 
91 /* number of references from net80211 layer */
92 static	int nrefs = 0;
93 
94 static void *
95 ccmp_attach(struct ieee80211vap *vap, struct ieee80211_key *k)
96 {
97 	struct ccmp_ctx *ctx;
98 
99 	ctx = (struct ccmp_ctx *) kmalloc(sizeof(struct ccmp_ctx),
100 		M_80211_CRYPTO, M_INTWAIT | M_ZERO);
101 	if (ctx == NULL) {
102 		vap->iv_stats.is_crypto_nomem++;
103 		return NULL;
104 	}
105 	ctx->cc_vap = vap;
106 	ctx->cc_ic = vap->iv_ic;
107 	nrefs++;			/* NB: we assume caller locking */
108 	return ctx;
109 }
110 
111 static void
112 ccmp_detach(struct ieee80211_key *k)
113 {
114 	struct ccmp_ctx *ctx = k->wk_private;
115 
116 	kfree(ctx, M_80211_CRYPTO);
117 	KASSERT(nrefs > 0, ("imbalanced attach/detach"));
118 	nrefs--;			/* NB: we assume caller locking */
119 }
120 
121 static int
122 ccmp_setkey(struct ieee80211_key *k)
123 {
124 	struct ccmp_ctx *ctx = k->wk_private;
125 
126 	if (k->wk_keylen != (128/NBBY)) {
127 		IEEE80211_DPRINTF(ctx->cc_vap, IEEE80211_MSG_CRYPTO,
128 			"%s: Invalid key length %u, expecting %u\n",
129 			__func__, k->wk_keylen, 128/NBBY);
130 		return 0;
131 	}
132 	if (k->wk_flags & IEEE80211_KEY_SWENCRYPT)
133 		rijndael_set_key(&ctx->cc_aes, k->wk_key, k->wk_keylen*NBBY);
134 	return 1;
135 }
136 
137 /*
138  * Add privacy headers appropriate for the specified key.
139  */
140 static int
141 ccmp_encap(struct ieee80211_key *k, struct mbuf *m, uint8_t keyid)
142 {
143 	struct ccmp_ctx *ctx = k->wk_private;
144 	struct ieee80211com *ic = ctx->cc_ic;
145 	uint8_t *ivp;
146 	int hdrlen;
147 
148 	hdrlen = ieee80211_hdrspace(ic, mtod(m, void *));
149 
150 	/*
151 	 * Copy down 802.11 header and add the IV, KeyID, and ExtIV.
152 	 */
153 	M_PREPEND(m, ccmp.ic_header, MB_DONTWAIT);
154 	if (m == NULL)
155 		return 0;
156 	ivp = mtod(m, uint8_t *);
157 	ovbcopy(ivp + ccmp.ic_header, ivp, hdrlen);
158 	ivp += hdrlen;
159 
160 	k->wk_keytsc++;		/* XXX wrap at 48 bits */
161 	ivp[0] = k->wk_keytsc >> 0;		/* PN0 */
162 	ivp[1] = k->wk_keytsc >> 8;		/* PN1 */
163 	ivp[2] = 0;				/* Reserved */
164 	ivp[3] = keyid | IEEE80211_WEP_EXTIV;	/* KeyID | ExtID */
165 	ivp[4] = k->wk_keytsc >> 16;		/* PN2 */
166 	ivp[5] = k->wk_keytsc >> 24;		/* PN3 */
167 	ivp[6] = k->wk_keytsc >> 32;		/* PN4 */
168 	ivp[7] = k->wk_keytsc >> 40;		/* PN5 */
169 
170 	/*
171 	 * Finally, do software encrypt if neeed.
172 	 */
173 	if ((k->wk_flags & IEEE80211_KEY_SWENCRYPT) &&
174 	    !ccmp_encrypt(k, m, hdrlen))
175 		return 0;
176 
177 	return 1;
178 }
179 
180 /*
181  * Add MIC to the frame as needed.
182  */
183 static int
184 ccmp_enmic(struct ieee80211_key *k, struct mbuf *m, int force)
185 {
186 
187 	return 1;
188 }
189 
190 static __inline uint64_t
191 READ_6(uint8_t b0, uint8_t b1, uint8_t b2, uint8_t b3, uint8_t b4, uint8_t b5)
192 {
193 	uint32_t iv32 = (b0 << 0) | (b1 << 8) | (b2 << 16) | (b3 << 24);
194 	uint16_t iv16 = (b4 << 0) | (b5 << 8);
195 	return (((uint64_t)iv16) << 32) | iv32;
196 }
197 
198 /*
199  * Validate and strip privacy headers (and trailer) for a
200  * received frame. The specified key should be correct but
201  * is also verified.
202  */
203 static int
204 ccmp_decap(struct ieee80211_key *k, struct mbuf *m, int hdrlen)
205 {
206 	struct ccmp_ctx *ctx = k->wk_private;
207 	struct ieee80211vap *vap = ctx->cc_vap;
208 	struct ieee80211_frame *wh;
209 	uint8_t *ivp, tid;
210 	uint64_t pn;
211 
212 	/*
213 	 * Header should have extended IV and sequence number;
214 	 * verify the former and validate the latter.
215 	 */
216 	wh = mtod(m, struct ieee80211_frame *);
217 	ivp = mtod(m, uint8_t *) + hdrlen;
218 	if ((ivp[IEEE80211_WEP_IVLEN] & IEEE80211_WEP_EXTIV) == 0) {
219 		/*
220 		 * No extended IV; discard frame.
221 		 */
222 		IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, wh->i_addr2,
223 			"%s", "missing ExtIV for AES-CCM cipher");
224 		vap->iv_stats.is_rx_ccmpformat++;
225 		return 0;
226 	}
227 	tid = ieee80211_gettid(wh);
228 	pn = READ_6(ivp[0], ivp[1], ivp[4], ivp[5], ivp[6], ivp[7]);
229 	if (pn <= k->wk_keyrsc[tid]) {
230 		/*
231 		 * Replay violation.
232 		 */
233 		ieee80211_notify_replay_failure(vap, wh, k, pn, tid);
234 		vap->iv_stats.is_rx_ccmpreplay++;
235 		return 0;
236 	}
237 
238 	/*
239 	 * Check if the device handled the decrypt in hardware.
240 	 * If so we just strip the header; otherwise we need to
241 	 * handle the decrypt in software.  Note that for the
242 	 * latter we leave the header in place for use in the
243 	 * decryption work.
244 	 */
245 	if ((k->wk_flags & IEEE80211_KEY_SWDECRYPT) &&
246 	    !ccmp_decrypt(k, pn, m, hdrlen))
247 		return 0;
248 
249 	/*
250 	 * Copy up 802.11 header and strip crypto bits.
251 	 */
252 	ovbcopy(mtod(m, void *), mtod(m, uint8_t *) + ccmp.ic_header, hdrlen);
253 	m_adj(m, ccmp.ic_header);
254 	m_adj(m, -ccmp.ic_trailer);
255 
256 	/*
257 	 * Ok to update rsc now.
258 	 */
259 	k->wk_keyrsc[tid] = pn;
260 
261 	return 1;
262 }
263 
264 /*
265  * Verify and strip MIC from the frame.
266  */
267 static int
268 ccmp_demic(struct ieee80211_key *k, struct mbuf *m, int force)
269 {
270 	return 1;
271 }
272 
273 static __inline void
274 xor_block(uint8_t *b, const uint8_t *a, size_t len)
275 {
276 	int i;
277 	for (i = 0; i < len; i++)
278 		b[i] ^= a[i];
279 }
280 
281 /*
282  * Host AP crypt: host-based CCMP encryption implementation for Host AP driver
283  *
284  * Copyright (c) 2003-2004, Jouni Malinen <jkmaline@cc.hut.fi>
285  *
286  * This program is free software; you can redistribute it and/or modify
287  * it under the terms of the GNU General Public License version 2 as
288  * published by the Free Software Foundation. See README and COPYING for
289  * more details.
290  *
291  * Alternatively, this software may be distributed under the terms of BSD
292  * license.
293  */
294 
295 static void
296 ccmp_init_blocks(rijndael_ctx *ctx, struct ieee80211_frame *wh,
297 	u_int64_t pn, size_t dlen,
298 	uint8_t b0[AES_BLOCK_LEN], uint8_t aad[2 * AES_BLOCK_LEN],
299 	uint8_t auth[AES_BLOCK_LEN], uint8_t s0[AES_BLOCK_LEN])
300 {
301 #define	IS_QOS_DATA(wh)	IEEE80211_QOS_HAS_SEQ(wh)
302 
303 	/* CCM Initial Block:
304 	 * Flag (Include authentication header, M=3 (8-octet MIC),
305 	 *       L=1 (2-octet Dlen))
306 	 * Nonce: 0x00 | A2 | PN
307 	 * Dlen */
308 	b0[0] = 0x59;
309 	/* NB: b0[1] set below */
310 	IEEE80211_ADDR_COPY(b0 + 2, wh->i_addr2);
311 	b0[8] = pn >> 40;
312 	b0[9] = pn >> 32;
313 	b0[10] = pn >> 24;
314 	b0[11] = pn >> 16;
315 	b0[12] = pn >> 8;
316 	b0[13] = pn >> 0;
317 	b0[14] = (dlen >> 8) & 0xff;
318 	b0[15] = dlen & 0xff;
319 
320 	/* AAD:
321 	 * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
322 	 * A1 | A2 | A3
323 	 * SC with bits 4..15 (seq#) masked to zero
324 	 * A4 (if present)
325 	 * QC (if present)
326 	 */
327 	aad[0] = 0;	/* AAD length >> 8 */
328 	/* NB: aad[1] set below */
329 	aad[2] = wh->i_fc[0] & 0x8f;	/* XXX magic #s */
330 	aad[3] = wh->i_fc[1] & 0xc7;	/* XXX magic #s */
331 	/* NB: we know 3 addresses are contiguous */
332 	memcpy(aad + 4, wh->i_addr1, 3 * IEEE80211_ADDR_LEN);
333 	aad[22] = wh->i_seq[0] & IEEE80211_SEQ_FRAG_MASK;
334 	aad[23] = 0; /* all bits masked */
335 	/*
336 	 * Construct variable-length portion of AAD based
337 	 * on whether this is a 4-address frame/QOS frame.
338 	 * We always zero-pad to 32 bytes before running it
339 	 * through the cipher.
340 	 *
341 	 * We also fill in the priority bits of the CCM
342 	 * initial block as we know whether or not we have
343 	 * a QOS frame.
344 	 */
345 	if (IEEE80211_IS_DSTODS(wh)) {
346 		IEEE80211_ADDR_COPY(aad + 24,
347 			((struct ieee80211_frame_addr4 *)wh)->i_addr4);
348 		if (IS_QOS_DATA(wh)) {
349 			struct ieee80211_qosframe_addr4 *qwh4 =
350 				(struct ieee80211_qosframe_addr4 *) wh;
351 			aad[30] = qwh4->i_qos[0] & 0x0f;/* just priority bits */
352 			aad[31] = 0;
353 			b0[1] = aad[30];
354 			aad[1] = 22 + IEEE80211_ADDR_LEN + 2;
355 		} else {
356 			*(uint16_t *)&aad[30] = 0;
357 			b0[1] = 0;
358 			aad[1] = 22 + IEEE80211_ADDR_LEN;
359 		}
360 	} else {
361 		if (IS_QOS_DATA(wh)) {
362 			struct ieee80211_qosframe *qwh =
363 				(struct ieee80211_qosframe*) wh;
364 			aad[24] = qwh->i_qos[0] & 0x0f;	/* just priority bits */
365 			aad[25] = 0;
366 			b0[1] = aad[24];
367 			aad[1] = 22 + 2;
368 		} else {
369 			*(uint16_t *)&aad[24] = 0;
370 			b0[1] = 0;
371 			aad[1] = 22;
372 		}
373 		*(uint16_t *)&aad[26] = 0;
374 		*(uint32_t *)&aad[28] = 0;
375 	}
376 
377 	/* Start with the first block and AAD */
378 	rijndael_encrypt(ctx, b0, auth);
379 	xor_block(auth, aad, AES_BLOCK_LEN);
380 	rijndael_encrypt(ctx, auth, auth);
381 	xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
382 	rijndael_encrypt(ctx, auth, auth);
383 	b0[0] &= 0x07;
384 	b0[14] = b0[15] = 0;
385 	rijndael_encrypt(ctx, b0, s0);
386 #undef	IS_QOS_DATA
387 }
388 
389 #define	CCMP_ENCRYPT(_i, _b, _b0, _pos, _e, _len) do {	\
390 	/* Authentication */				\
391 	xor_block(_b, _pos, _len);			\
392 	rijndael_encrypt(&ctx->cc_aes, _b, _b);		\
393 	/* Encryption, with counter */			\
394 	_b0[14] = (_i >> 8) & 0xff;			\
395 	_b0[15] = _i & 0xff;				\
396 	rijndael_encrypt(&ctx->cc_aes, _b0, _e);	\
397 	xor_block(_pos, _e, _len);			\
398 } while (0)
399 
400 static int
401 ccmp_encrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen)
402 {
403 	struct ccmp_ctx *ctx = key->wk_private;
404 	struct ieee80211_frame *wh;
405 	struct mbuf *m = m0;
406 	int data_len, i, space;
407 	uint8_t aad[2 * AES_BLOCK_LEN], b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN],
408 		e[AES_BLOCK_LEN], s0[AES_BLOCK_LEN];
409 	uint8_t *pos;
410 
411 	ctx->cc_vap->iv_stats.is_crypto_ccmp++;
412 
413 	wh = mtod(m, struct ieee80211_frame *);
414 	data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header);
415 	ccmp_init_blocks(&ctx->cc_aes, wh, key->wk_keytsc,
416 		data_len, b0, aad, b, s0);
417 
418 	i = 1;
419 	pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
420 	/* NB: assumes header is entirely in first mbuf */
421 	space = m->m_len - (hdrlen + ccmp.ic_header);
422 	for (;;) {
423 		if (space > data_len)
424 			space = data_len;
425 		/*
426 		 * Do full blocks.
427 		 */
428 		while (space >= AES_BLOCK_LEN) {
429 			CCMP_ENCRYPT(i, b, b0, pos, e, AES_BLOCK_LEN);
430 			pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
431 			data_len -= AES_BLOCK_LEN;
432 			i++;
433 		}
434 		if (data_len <= 0)		/* no more data */
435 			break;
436 		m = m->m_next;
437 		if (m == NULL) {		/* last buffer */
438 			if (space != 0) {
439 				/*
440 				 * Short last block.
441 				 */
442 				CCMP_ENCRYPT(i, b, b0, pos, e, space);
443 			}
444 			break;
445 		}
446 		if (space != 0) {
447 			uint8_t *pos_next;
448 			int space_next;
449 			int len, dl, sp;
450 			struct mbuf *n;
451 
452 			/*
453 			 * Block straddles one or more mbufs, gather data
454 			 * into the block buffer b, apply the cipher, then
455 			 * scatter the results back into the mbuf chain.
456 			 * The buffer will automatically get space bytes
457 			 * of data at offset 0 copied in+out by the
458 			 * CCMP_ENCRYPT request so we must take care of
459 			 * the remaining data.
460 			 */
461 			n = m;
462 			dl = data_len;
463 			sp = space;
464 			for (;;) {
465 				pos_next = mtod(n, uint8_t *);
466 				len = min(dl, AES_BLOCK_LEN);
467 				space_next = len > sp ? len - sp : 0;
468 				if (n->m_len >= space_next) {
469 					/*
470 					 * This mbuf has enough data; just grab
471 					 * what we need and stop.
472 					 */
473 					xor_block(b+sp, pos_next, space_next);
474 					break;
475 				}
476 				/*
477 				 * This mbuf's contents are insufficient,
478 				 * take 'em all and prepare to advance to
479 				 * the next mbuf.
480 				 */
481 				xor_block(b+sp, pos_next, n->m_len);
482 				sp += n->m_len, dl -= n->m_len;
483 				n = n->m_next;
484 				if (n == NULL)
485 					break;
486 			}
487 
488 			CCMP_ENCRYPT(i, b, b0, pos, e, space);
489 
490 			/* NB: just like above, but scatter data to mbufs */
491 			dl = data_len;
492 			sp = space;
493 			for (;;) {
494 				pos_next = mtod(m, uint8_t *);
495 				len = min(dl, AES_BLOCK_LEN);
496 				space_next = len > sp ? len - sp : 0;
497 				if (m->m_len >= space_next) {
498 					xor_block(pos_next, e+sp, space_next);
499 					break;
500 				}
501 				xor_block(pos_next, e+sp, m->m_len);
502 				sp += m->m_len, dl -= m->m_len;
503 				m = m->m_next;
504 				if (m == NULL)
505 					goto done;
506 			}
507 			/*
508 			 * Do bookkeeping.  m now points to the last mbuf
509 			 * we grabbed data from.  We know we consumed a
510 			 * full block of data as otherwise we'd have hit
511 			 * the end of the mbuf chain, so deduct from data_len.
512 			 * Otherwise advance the block number (i) and setup
513 			 * pos+space to reflect contents of the new mbuf.
514 			 */
515 			data_len -= AES_BLOCK_LEN;
516 			i++;
517 			pos = pos_next + space_next;
518 			space = m->m_len - space_next;
519 		} else {
520 			/*
521 			 * Setup for next buffer.
522 			 */
523 			pos = mtod(m, uint8_t *);
524 			space = m->m_len;
525 		}
526 	}
527 done:
528 	/* tack on MIC */
529 	xor_block(b, s0, ccmp.ic_trailer);
530 	return m_append(m0, ccmp.ic_trailer, b);
531 }
532 #undef CCMP_ENCRYPT
533 
534 #define	CCMP_DECRYPT(_i, _b, _b0, _pos, _a, _len) do {	\
535 	/* Decrypt, with counter */			\
536 	_b0[14] = (_i >> 8) & 0xff;			\
537 	_b0[15] = _i & 0xff;				\
538 	rijndael_encrypt(&ctx->cc_aes, _b0, _b);	\
539 	xor_block(_pos, _b, _len);			\
540 	/* Authentication */				\
541 	xor_block(_a, _pos, _len);			\
542 	rijndael_encrypt(&ctx->cc_aes, _a, _a);		\
543 } while (0)
544 
545 static int
546 ccmp_decrypt(struct ieee80211_key *key, u_int64_t pn, struct mbuf *m, int hdrlen)
547 {
548 	struct ccmp_ctx *ctx = key->wk_private;
549 	struct ieee80211vap *vap = ctx->cc_vap;
550 	struct ieee80211_frame *wh;
551 	uint8_t aad[2 * AES_BLOCK_LEN];
552 	uint8_t b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN], a[AES_BLOCK_LEN];
553 	uint8_t mic[AES_BLOCK_LEN];
554 	size_t data_len;
555 	int i;
556 	uint8_t *pos;
557 	u_int space;
558 
559 	ctx->cc_vap->iv_stats.is_crypto_ccmp++;
560 
561 	wh = mtod(m, struct ieee80211_frame *);
562 	data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header + ccmp.ic_trailer);
563 	ccmp_init_blocks(&ctx->cc_aes, wh, pn, data_len, b0, aad, a, b);
564 	m_copydata(m, m->m_pkthdr.len - ccmp.ic_trailer, ccmp.ic_trailer, mic);
565 	xor_block(mic, b, ccmp.ic_trailer);
566 
567 	i = 1;
568 	pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
569 	space = m->m_len - (hdrlen + ccmp.ic_header);
570 	for (;;) {
571 		if (space > data_len)
572 			space = data_len;
573 		while (space >= AES_BLOCK_LEN) {
574 			CCMP_DECRYPT(i, b, b0, pos, a, AES_BLOCK_LEN);
575 			pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
576 			data_len -= AES_BLOCK_LEN;
577 			i++;
578 		}
579 		if (data_len <= 0)		/* no more data */
580 			break;
581 		m = m->m_next;
582 		if (m == NULL) {		/* last buffer */
583 			if (space != 0)		/* short last block */
584 				CCMP_DECRYPT(i, b, b0, pos, a, space);
585 			break;
586 		}
587 		if (space != 0) {
588 			uint8_t *pos_next;
589 			u_int space_next;
590 			u_int len;
591 
592 			/*
593 			 * Block straddles buffers, split references.  We
594 			 * do not handle splits that require >2 buffers
595 			 * since rx'd frames are never badly fragmented
596 			 * because drivers typically recv in clusters.
597 			 */
598 			pos_next = mtod(m, uint8_t *);
599 			len = min(data_len, AES_BLOCK_LEN);
600 			space_next = len > space ? len - space : 0;
601 			KASSERT(m->m_len >= space_next,
602 				("not enough data in following buffer, "
603 				"m_len %u need %u", m->m_len, space_next));
604 
605 			xor_block(b+space, pos_next, space_next);
606 			CCMP_DECRYPT(i, b, b0, pos, a, space);
607 			xor_block(pos_next, b+space, space_next);
608 			data_len -= len;
609 			i++;
610 
611 			pos = pos_next + space_next;
612 			space = m->m_len - space_next;
613 		} else {
614 			/*
615 			 * Setup for next buffer.
616 			 */
617 			pos = mtod(m, uint8_t *);
618 			space = m->m_len;
619 		}
620 	}
621 	if (memcmp(mic, a, ccmp.ic_trailer) != 0) {
622 		IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, wh->i_addr2,
623 		    "%s", "AES-CCM decrypt failed; MIC mismatch");
624 		vap->iv_stats.is_rx_ccmpmic++;
625 		return 0;
626 	}
627 	return 1;
628 }
629 #undef CCMP_DECRYPT
630 
631 /*
632  * Module glue.
633  */
634 IEEE80211_CRYPTO_MODULE(ccmp, 1);
635