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 
26 #include <sys/cdefs.h>
27 __FBSDID("$FreeBSD$");
28 
29 /*
30  * IEEE 802.11i AES-CCMP crypto support.
31  *
32  * Part of this module is derived from similar code in the Host
33  * AP driver. The code is used with the consent of the author and
34  * it's license is included below.
35  */
36 #include "opt_wlan.h"
37 
38 #include <sys/param.h>
39 #include <sys/systm.h>
40 #include <sys/mbuf.h>
41 #include <sys/malloc.h>
42 #include <sys/kernel.h>
43 #include <sys/module.h>
44 
45 #include <sys/socket.h>
46 
47 #include <net/if.h>
48 #include <net/if_media.h>
49 #include <net/ethernet.h>
50 
51 #include <net80211/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 *) malloc(sizeof(struct ccmp_ctx),
100 		M_80211_CRYPTO, M_NOWAIT | 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 	free(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, M_NOWAIT);
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 	/*
230 	 * NB: Multiple stations are using the same key in
231 	 * IBSS mode, there is currently no way to sync keyrsc
232 	 * counters without discarding too many frames.
233 	 */
234 	if (vap->iv_opmode != IEEE80211_M_IBSS &&
235 	    vap->iv_opmode != IEEE80211_M_AHDEMO &&
236 	    pn <= k->wk_keyrsc[tid]) {
237 		/*
238 		 * Replay violation.
239 		 */
240 		ieee80211_notify_replay_failure(vap, wh, k, pn, tid);
241 		vap->iv_stats.is_rx_ccmpreplay++;
242 		return 0;
243 	}
244 
245 	/*
246 	 * Check if the device handled the decrypt in hardware.
247 	 * If so we just strip the header; otherwise we need to
248 	 * handle the decrypt in software.  Note that for the
249 	 * latter we leave the header in place for use in the
250 	 * decryption work.
251 	 */
252 	if ((k->wk_flags & IEEE80211_KEY_SWDECRYPT) &&
253 	    !ccmp_decrypt(k, pn, m, hdrlen))
254 		return 0;
255 
256 	/*
257 	 * Copy up 802.11 header and strip crypto bits.
258 	 */
259 	ovbcopy(mtod(m, void *), mtod(m, uint8_t *) + ccmp.ic_header, hdrlen);
260 	m_adj(m, ccmp.ic_header);
261 	m_adj(m, -ccmp.ic_trailer);
262 
263 	/*
264 	 * Ok to update rsc now.
265 	 */
266 	k->wk_keyrsc[tid] = pn;
267 
268 	return 1;
269 }
270 
271 /*
272  * Verify and strip MIC from the frame.
273  */
274 static int
275 ccmp_demic(struct ieee80211_key *k, struct mbuf *m, int force)
276 {
277 	return 1;
278 }
279 
280 static __inline void
281 xor_block(uint8_t *b, const uint8_t *a, size_t len)
282 {
283 	int i;
284 	for (i = 0; i < len; i++)
285 		b[i] ^= a[i];
286 }
287 
288 /*
289  * Host AP crypt: host-based CCMP encryption implementation for Host AP driver
290  *
291  * Copyright (c) 2003-2004, Jouni Malinen <jkmaline@cc.hut.fi>
292  *
293  * This program is free software; you can redistribute it and/or modify
294  * it under the terms of the GNU General Public License version 2 as
295  * published by the Free Software Foundation. See README and COPYING for
296  * more details.
297  *
298  * Alternatively, this software may be distributed under the terms of BSD
299  * license.
300  */
301 
302 static void
303 ccmp_init_blocks(rijndael_ctx *ctx, struct ieee80211_frame *wh,
304 	u_int64_t pn, size_t dlen,
305 	uint8_t b0[AES_BLOCK_LEN], uint8_t aad[2 * AES_BLOCK_LEN],
306 	uint8_t auth[AES_BLOCK_LEN], uint8_t s0[AES_BLOCK_LEN])
307 {
308 #define	IS_QOS_DATA(wh)	IEEE80211_QOS_HAS_SEQ(wh)
309 
310 	/* CCM Initial Block:
311 	 * Flag (Include authentication header, M=3 (8-octet MIC),
312 	 *       L=1 (2-octet Dlen))
313 	 * Nonce: 0x00 | A2 | PN
314 	 * Dlen */
315 	b0[0] = 0x59;
316 	/* NB: b0[1] set below */
317 	IEEE80211_ADDR_COPY(b0 + 2, wh->i_addr2);
318 	b0[8] = pn >> 40;
319 	b0[9] = pn >> 32;
320 	b0[10] = pn >> 24;
321 	b0[11] = pn >> 16;
322 	b0[12] = pn >> 8;
323 	b0[13] = pn >> 0;
324 	b0[14] = (dlen >> 8) & 0xff;
325 	b0[15] = dlen & 0xff;
326 
327 	/* AAD:
328 	 * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
329 	 * A1 | A2 | A3
330 	 * SC with bits 4..15 (seq#) masked to zero
331 	 * A4 (if present)
332 	 * QC (if present)
333 	 */
334 	aad[0] = 0;	/* AAD length >> 8 */
335 	/* NB: aad[1] set below */
336 	aad[2] = wh->i_fc[0] & 0x8f;	/* XXX magic #s */
337 	aad[3] = wh->i_fc[1] & 0xc7;	/* XXX magic #s */
338 	/* NB: we know 3 addresses are contiguous */
339 	memcpy(aad + 4, wh->i_addr1, 3 * IEEE80211_ADDR_LEN);
340 	aad[22] = wh->i_seq[0] & IEEE80211_SEQ_FRAG_MASK;
341 	aad[23] = 0; /* all bits masked */
342 	/*
343 	 * Construct variable-length portion of AAD based
344 	 * on whether this is a 4-address frame/QOS frame.
345 	 * We always zero-pad to 32 bytes before running it
346 	 * through the cipher.
347 	 *
348 	 * We also fill in the priority bits of the CCM
349 	 * initial block as we know whether or not we have
350 	 * a QOS frame.
351 	 */
352 	if (IEEE80211_IS_DSTODS(wh)) {
353 		IEEE80211_ADDR_COPY(aad + 24,
354 			((struct ieee80211_frame_addr4 *)wh)->i_addr4);
355 		if (IS_QOS_DATA(wh)) {
356 			struct ieee80211_qosframe_addr4 *qwh4 =
357 				(struct ieee80211_qosframe_addr4 *) wh;
358 			aad[30] = qwh4->i_qos[0] & 0x0f;/* just priority bits */
359 			aad[31] = 0;
360 			b0[1] = aad[30];
361 			aad[1] = 22 + IEEE80211_ADDR_LEN + 2;
362 		} else {
363 			*(uint16_t *)&aad[30] = 0;
364 			b0[1] = 0;
365 			aad[1] = 22 + IEEE80211_ADDR_LEN;
366 		}
367 	} else {
368 		if (IS_QOS_DATA(wh)) {
369 			struct ieee80211_qosframe *qwh =
370 				(struct ieee80211_qosframe*) wh;
371 			aad[24] = qwh->i_qos[0] & 0x0f;	/* just priority bits */
372 			aad[25] = 0;
373 			b0[1] = aad[24];
374 			aad[1] = 22 + 2;
375 		} else {
376 			*(uint16_t *)&aad[24] = 0;
377 			b0[1] = 0;
378 			aad[1] = 22;
379 		}
380 		*(uint16_t *)&aad[26] = 0;
381 		*(uint32_t *)&aad[28] = 0;
382 	}
383 
384 	/* Start with the first block and AAD */
385 	rijndael_encrypt(ctx, b0, auth);
386 	xor_block(auth, aad, AES_BLOCK_LEN);
387 	rijndael_encrypt(ctx, auth, auth);
388 	xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
389 	rijndael_encrypt(ctx, auth, auth);
390 	b0[0] &= 0x07;
391 	b0[14] = b0[15] = 0;
392 	rijndael_encrypt(ctx, b0, s0);
393 #undef	IS_QOS_DATA
394 }
395 
396 #define	CCMP_ENCRYPT(_i, _b, _b0, _pos, _e, _len) do {	\
397 	/* Authentication */				\
398 	xor_block(_b, _pos, _len);			\
399 	rijndael_encrypt(&ctx->cc_aes, _b, _b);		\
400 	/* Encryption, with counter */			\
401 	_b0[14] = (_i >> 8) & 0xff;			\
402 	_b0[15] = _i & 0xff;				\
403 	rijndael_encrypt(&ctx->cc_aes, _b0, _e);	\
404 	xor_block(_pos, _e, _len);			\
405 } while (0)
406 
407 static int
408 ccmp_encrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen)
409 {
410 	struct ccmp_ctx *ctx = key->wk_private;
411 	struct ieee80211_frame *wh;
412 	struct mbuf *m = m0;
413 	int data_len, i, space;
414 	uint8_t aad[2 * AES_BLOCK_LEN], b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN],
415 		e[AES_BLOCK_LEN], s0[AES_BLOCK_LEN];
416 	uint8_t *pos;
417 
418 	ctx->cc_vap->iv_stats.is_crypto_ccmp++;
419 
420 	wh = mtod(m, struct ieee80211_frame *);
421 	data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header);
422 	ccmp_init_blocks(&ctx->cc_aes, wh, key->wk_keytsc,
423 		data_len, b0, aad, b, s0);
424 
425 	i = 1;
426 	pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
427 	/* NB: assumes header is entirely in first mbuf */
428 	space = m->m_len - (hdrlen + ccmp.ic_header);
429 	for (;;) {
430 		if (space > data_len)
431 			space = data_len;
432 		/*
433 		 * Do full blocks.
434 		 */
435 		while (space >= AES_BLOCK_LEN) {
436 			CCMP_ENCRYPT(i, b, b0, pos, e, AES_BLOCK_LEN);
437 			pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
438 			data_len -= AES_BLOCK_LEN;
439 			i++;
440 		}
441 		if (data_len <= 0)		/* no more data */
442 			break;
443 		m = m->m_next;
444 		if (m == NULL) {		/* last buffer */
445 			if (space != 0) {
446 				/*
447 				 * Short last block.
448 				 */
449 				CCMP_ENCRYPT(i, b, b0, pos, e, space);
450 			}
451 			break;
452 		}
453 		if (space != 0) {
454 			uint8_t *pos_next;
455 			int space_next;
456 			int len, dl, sp;
457 			struct mbuf *n;
458 
459 			/*
460 			 * Block straddles one or more mbufs, gather data
461 			 * into the block buffer b, apply the cipher, then
462 			 * scatter the results back into the mbuf chain.
463 			 * The buffer will automatically get space bytes
464 			 * of data at offset 0 copied in+out by the
465 			 * CCMP_ENCRYPT request so we must take care of
466 			 * the remaining data.
467 			 */
468 			n = m;
469 			dl = data_len;
470 			sp = space;
471 			for (;;) {
472 				pos_next = mtod(n, uint8_t *);
473 				len = min(dl, AES_BLOCK_LEN);
474 				space_next = len > sp ? len - sp : 0;
475 				if (n->m_len >= space_next) {
476 					/*
477 					 * This mbuf has enough data; just grab
478 					 * what we need and stop.
479 					 */
480 					xor_block(b+sp, pos_next, space_next);
481 					break;
482 				}
483 				/*
484 				 * This mbuf's contents are insufficient,
485 				 * take 'em all and prepare to advance to
486 				 * the next mbuf.
487 				 */
488 				xor_block(b+sp, pos_next, n->m_len);
489 				sp += n->m_len, dl -= n->m_len;
490 				n = n->m_next;
491 				if (n == NULL)
492 					break;
493 			}
494 
495 			CCMP_ENCRYPT(i, b, b0, pos, e, space);
496 
497 			/* NB: just like above, but scatter data to mbufs */
498 			dl = data_len;
499 			sp = space;
500 			for (;;) {
501 				pos_next = mtod(m, uint8_t *);
502 				len = min(dl, AES_BLOCK_LEN);
503 				space_next = len > sp ? len - sp : 0;
504 				if (m->m_len >= space_next) {
505 					xor_block(pos_next, e+sp, space_next);
506 					break;
507 				}
508 				xor_block(pos_next, e+sp, m->m_len);
509 				sp += m->m_len, dl -= m->m_len;
510 				m = m->m_next;
511 				if (m == NULL)
512 					goto done;
513 			}
514 			/*
515 			 * Do bookkeeping.  m now points to the last mbuf
516 			 * we grabbed data from.  We know we consumed a
517 			 * full block of data as otherwise we'd have hit
518 			 * the end of the mbuf chain, so deduct from data_len.
519 			 * Otherwise advance the block number (i) and setup
520 			 * pos+space to reflect contents of the new mbuf.
521 			 */
522 			data_len -= AES_BLOCK_LEN;
523 			i++;
524 			pos = pos_next + space_next;
525 			space = m->m_len - space_next;
526 		} else {
527 			/*
528 			 * Setup for next buffer.
529 			 */
530 			pos = mtod(m, uint8_t *);
531 			space = m->m_len;
532 		}
533 	}
534 done:
535 	/* tack on MIC */
536 	xor_block(b, s0, ccmp.ic_trailer);
537 	return m_append(m0, ccmp.ic_trailer, b);
538 }
539 #undef CCMP_ENCRYPT
540 
541 #define	CCMP_DECRYPT(_i, _b, _b0, _pos, _a, _len) do {	\
542 	/* Decrypt, with counter */			\
543 	_b0[14] = (_i >> 8) & 0xff;			\
544 	_b0[15] = _i & 0xff;				\
545 	rijndael_encrypt(&ctx->cc_aes, _b0, _b);	\
546 	xor_block(_pos, _b, _len);			\
547 	/* Authentication */				\
548 	xor_block(_a, _pos, _len);			\
549 	rijndael_encrypt(&ctx->cc_aes, _a, _a);		\
550 } while (0)
551 
552 static int
553 ccmp_decrypt(struct ieee80211_key *key, u_int64_t pn, struct mbuf *m, int hdrlen)
554 {
555 	struct ccmp_ctx *ctx = key->wk_private;
556 	struct ieee80211vap *vap = ctx->cc_vap;
557 	struct ieee80211_frame *wh;
558 	uint8_t aad[2 * AES_BLOCK_LEN];
559 	uint8_t b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN], a[AES_BLOCK_LEN];
560 	uint8_t mic[AES_BLOCK_LEN];
561 	size_t data_len;
562 	int i;
563 	uint8_t *pos;
564 	u_int space;
565 
566 	ctx->cc_vap->iv_stats.is_crypto_ccmp++;
567 
568 	wh = mtod(m, struct ieee80211_frame *);
569 	data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header + ccmp.ic_trailer);
570 	ccmp_init_blocks(&ctx->cc_aes, wh, pn, data_len, b0, aad, a, b);
571 	m_copydata(m, m->m_pkthdr.len - ccmp.ic_trailer, ccmp.ic_trailer, mic);
572 	xor_block(mic, b, ccmp.ic_trailer);
573 
574 	i = 1;
575 	pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
576 	space = m->m_len - (hdrlen + ccmp.ic_header);
577 	for (;;) {
578 		if (space > data_len)
579 			space = data_len;
580 		while (space >= AES_BLOCK_LEN) {
581 			CCMP_DECRYPT(i, b, b0, pos, a, AES_BLOCK_LEN);
582 			pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
583 			data_len -= AES_BLOCK_LEN;
584 			i++;
585 		}
586 		if (data_len <= 0)		/* no more data */
587 			break;
588 		m = m->m_next;
589 		if (m == NULL) {		/* last buffer */
590 			if (space != 0)		/* short last block */
591 				CCMP_DECRYPT(i, b, b0, pos, a, space);
592 			break;
593 		}
594 		if (space != 0) {
595 			uint8_t *pos_next;
596 			u_int space_next;
597 			u_int len;
598 
599 			/*
600 			 * Block straddles buffers, split references.  We
601 			 * do not handle splits that require >2 buffers
602 			 * since rx'd frames are never badly fragmented
603 			 * because drivers typically recv in clusters.
604 			 */
605 			pos_next = mtod(m, uint8_t *);
606 			len = min(data_len, AES_BLOCK_LEN);
607 			space_next = len > space ? len - space : 0;
608 			KASSERT(m->m_len >= space_next,
609 				("not enough data in following buffer, "
610 				"m_len %u need %u\n", m->m_len, space_next));
611 
612 			xor_block(b+space, pos_next, space_next);
613 			CCMP_DECRYPT(i, b, b0, pos, a, space);
614 			xor_block(pos_next, b+space, space_next);
615 			data_len -= len;
616 			i++;
617 
618 			pos = pos_next + space_next;
619 			space = m->m_len - space_next;
620 		} else {
621 			/*
622 			 * Setup for next buffer.
623 			 */
624 			pos = mtod(m, uint8_t *);
625 			space = m->m_len;
626 		}
627 	}
628 	if (memcmp(mic, a, ccmp.ic_trailer) != 0) {
629 		IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, wh->i_addr2,
630 		    "%s", "AES-CCM decrypt failed; MIC mismatch");
631 		vap->iv_stats.is_rx_ccmpmic++;
632 		return 0;
633 	}
634 	return 1;
635 }
636 #undef CCMP_DECRYPT
637 
638 /*
639  * Module glue.
640  */
641 IEEE80211_CRYPTO_MODULE(ccmp, 1);
642