xref: /openbmc/linux/net/mac80211/wpa.c (revision 5a0e3ad6) 
1 /*
2  * Copyright 2002-2004, Instant802 Networks, Inc.
3  * Copyright 2008, Jouni Malinen <j@w1.fi>
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License version 2 as
7  * published by the Free Software Foundation.
8  */
9 
10 #include <linux/netdevice.h>
11 #include <linux/types.h>
12 #include <linux/skbuff.h>
13 #include <linux/compiler.h>
14 #include <linux/ieee80211.h>
15 #include <linux/gfp.h>
16 #include <asm/unaligned.h>
17 #include <net/mac80211.h>
18 
19 #include "ieee80211_i.h"
20 #include "michael.h"
21 #include "tkip.h"
22 #include "aes_ccm.h"
23 #include "aes_cmac.h"
24 #include "wpa.h"
25 
26 ieee80211_tx_result
27 ieee80211_tx_h_michael_mic_add(struct ieee80211_tx_data *tx)
28 {
29 	u8 *data, *key, *mic, key_offset;
30 	size_t data_len;
31 	unsigned int hdrlen;
32 	struct ieee80211_hdr *hdr;
33 	struct sk_buff *skb = tx->skb;
34 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
35 	int authenticator;
36 	int tail;
37 
38 	hdr = (struct ieee80211_hdr *)skb->data;
39 	if (!tx->key || tx->key->conf.alg != ALG_TKIP || skb->len < 24 ||
40 	    !ieee80211_is_data_present(hdr->frame_control))
41 		return TX_CONTINUE;
42 
43 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
44 	if (skb->len < hdrlen)
45 		return TX_DROP;
46 
47 	data = skb->data + hdrlen;
48 	data_len = skb->len - hdrlen;
49 
50 	if (info->control.hw_key &&
51 	    !(tx->flags & IEEE80211_TX_FRAGMENTED) &&
52 	    !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_MMIC)) {
53 		/* hwaccel - with no need for SW-generated MMIC */
54 		return TX_CONTINUE;
55 	}
56 
57 	tail = MICHAEL_MIC_LEN;
58 	if (!info->control.hw_key)
59 		tail += TKIP_ICV_LEN;
60 
61 	if (WARN_ON(skb_tailroom(skb) < tail ||
62 		    skb_headroom(skb) < TKIP_IV_LEN))
63 		return TX_DROP;
64 
65 #if 0
66 	authenticator = fc & IEEE80211_FCTL_FROMDS; /* FIX */
67 #else
68 	authenticator = 1;
69 #endif
70 	key_offset = authenticator ?
71 		NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY :
72 		NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY;
73 	key = &tx->key->conf.key[key_offset];
74 	mic = skb_put(skb, MICHAEL_MIC_LEN);
75 	michael_mic(key, hdr, data, data_len, mic);
76 
77 	return TX_CONTINUE;
78 }
79 
80 
81 ieee80211_rx_result
82 ieee80211_rx_h_michael_mic_verify(struct ieee80211_rx_data *rx)
83 {
84 	u8 *data, *key = NULL, key_offset;
85 	size_t data_len;
86 	unsigned int hdrlen;
87 	u8 mic[MICHAEL_MIC_LEN];
88 	struct sk_buff *skb = rx->skb;
89 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
90 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
91 	int authenticator = 1, wpa_test = 0;
92 
93 	/* No way to verify the MIC if the hardware stripped it */
94 	if (status->flag & RX_FLAG_MMIC_STRIPPED)
95 		return RX_CONTINUE;
96 
97 	if (!rx->key || rx->key->conf.alg != ALG_TKIP ||
98 	    !ieee80211_has_protected(hdr->frame_control) ||
99 	    !ieee80211_is_data_present(hdr->frame_control))
100 		return RX_CONTINUE;
101 
102 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
103 	if (skb->len < hdrlen + MICHAEL_MIC_LEN)
104 		return RX_DROP_UNUSABLE;
105 
106 	data = skb->data + hdrlen;
107 	data_len = skb->len - hdrlen - MICHAEL_MIC_LEN;
108 
109 #if 0
110 	authenticator = fc & IEEE80211_FCTL_TODS; /* FIX */
111 #else
112 	authenticator = 1;
113 #endif
114 	key_offset = authenticator ?
115 		NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY :
116 		NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY;
117 	key = &rx->key->conf.key[key_offset];
118 	michael_mic(key, hdr, data, data_len, mic);
119 	if (memcmp(mic, data + data_len, MICHAEL_MIC_LEN) != 0 || wpa_test) {
120 		if (!(rx->flags & IEEE80211_RX_RA_MATCH))
121 			return RX_DROP_UNUSABLE;
122 
123 		mac80211_ev_michael_mic_failure(rx->sdata, rx->key->conf.keyidx,
124 						(void *) skb->data, NULL,
125 						GFP_ATOMIC);
126 		return RX_DROP_UNUSABLE;
127 	}
128 
129 	/* remove Michael MIC from payload */
130 	skb_trim(skb, skb->len - MICHAEL_MIC_LEN);
131 
132 	/* update IV in key information to be able to detect replays */
133 	rx->key->u.tkip.rx[rx->queue].iv32 = rx->tkip_iv32;
134 	rx->key->u.tkip.rx[rx->queue].iv16 = rx->tkip_iv16;
135 
136 	return RX_CONTINUE;
137 }
138 
139 
140 static int tkip_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
141 {
142 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
143 	struct ieee80211_key *key = tx->key;
144 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
145 	unsigned int hdrlen;
146 	int len, tail;
147 	u8 *pos;
148 
149 	if (info->control.hw_key &&
150 	    !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
151 		/* hwaccel - with no need for software-generated IV */
152 		return 0;
153 	}
154 
155 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
156 	len = skb->len - hdrlen;
157 
158 	if (info->control.hw_key)
159 		tail = 0;
160 	else
161 		tail = TKIP_ICV_LEN;
162 
163 	if (WARN_ON(skb_tailroom(skb) < tail ||
164 		    skb_headroom(skb) < TKIP_IV_LEN))
165 		return -1;
166 
167 	pos = skb_push(skb, TKIP_IV_LEN);
168 	memmove(pos, pos + TKIP_IV_LEN, hdrlen);
169 	pos += hdrlen;
170 
171 	/* Increase IV for the frame */
172 	key->u.tkip.tx.iv16++;
173 	if (key->u.tkip.tx.iv16 == 0)
174 		key->u.tkip.tx.iv32++;
175 
176 	pos = ieee80211_tkip_add_iv(pos, key, key->u.tkip.tx.iv16);
177 
178 	/* hwaccel - with software IV */
179 	if (info->control.hw_key)
180 		return 0;
181 
182 	/* Add room for ICV */
183 	skb_put(skb, TKIP_ICV_LEN);
184 
185 	hdr = (struct ieee80211_hdr *) skb->data;
186 	ieee80211_tkip_encrypt_data(tx->local->wep_tx_tfm,
187 				    key, pos, len, hdr->addr2);
188 	return 0;
189 }
190 
191 
192 ieee80211_tx_result
193 ieee80211_crypto_tkip_encrypt(struct ieee80211_tx_data *tx)
194 {
195 	struct sk_buff *skb = tx->skb;
196 
197 	ieee80211_tx_set_protected(tx);
198 
199 	do {
200 		if (tkip_encrypt_skb(tx, skb) < 0)
201 			return TX_DROP;
202 	} while ((skb = skb->next));
203 
204 	return TX_CONTINUE;
205 }
206 
207 
208 ieee80211_rx_result
209 ieee80211_crypto_tkip_decrypt(struct ieee80211_rx_data *rx)
210 {
211 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) rx->skb->data;
212 	int hdrlen, res, hwaccel = 0, wpa_test = 0;
213 	struct ieee80211_key *key = rx->key;
214 	struct sk_buff *skb = rx->skb;
215 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
216 
217 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
218 
219 	if (!ieee80211_is_data(hdr->frame_control))
220 		return RX_CONTINUE;
221 
222 	if (!rx->sta || skb->len - hdrlen < 12)
223 		return RX_DROP_UNUSABLE;
224 
225 	if (status->flag & RX_FLAG_DECRYPTED) {
226 		if (status->flag & RX_FLAG_IV_STRIPPED) {
227 			/*
228 			 * Hardware took care of all processing, including
229 			 * replay protection, and stripped the ICV/IV so
230 			 * we cannot do any checks here.
231 			 */
232 			return RX_CONTINUE;
233 		}
234 
235 		/* let TKIP code verify IV, but skip decryption */
236 		hwaccel = 1;
237 	}
238 
239 	res = ieee80211_tkip_decrypt_data(rx->local->wep_rx_tfm,
240 					  key, skb->data + hdrlen,
241 					  skb->len - hdrlen, rx->sta->sta.addr,
242 					  hdr->addr1, hwaccel, rx->queue,
243 					  &rx->tkip_iv32,
244 					  &rx->tkip_iv16);
245 	if (res != TKIP_DECRYPT_OK || wpa_test)
246 		return RX_DROP_UNUSABLE;
247 
248 	/* Trim ICV */
249 	skb_trim(skb, skb->len - TKIP_ICV_LEN);
250 
251 	/* Remove IV */
252 	memmove(skb->data + TKIP_IV_LEN, skb->data, hdrlen);
253 	skb_pull(skb, TKIP_IV_LEN);
254 
255 	return RX_CONTINUE;
256 }
257 
258 
259 static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
260 				int encrypted)
261 {
262 	__le16 mask_fc;
263 	int a4_included, mgmt;
264 	u8 qos_tid;
265 	u8 *b_0, *aad;
266 	u16 data_len, len_a;
267 	unsigned int hdrlen;
268 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
269 
270 	b_0 = scratch + 3 * AES_BLOCK_LEN;
271 	aad = scratch + 4 * AES_BLOCK_LEN;
272 
273 	/*
274 	 * Mask FC: zero subtype b4 b5 b6 (if not mgmt)
275 	 * Retry, PwrMgt, MoreData; set Protected
276 	 */
277 	mgmt = ieee80211_is_mgmt(hdr->frame_control);
278 	mask_fc = hdr->frame_control;
279 	mask_fc &= ~cpu_to_le16(IEEE80211_FCTL_RETRY |
280 				IEEE80211_FCTL_PM | IEEE80211_FCTL_MOREDATA);
281 	if (!mgmt)
282 		mask_fc &= ~cpu_to_le16(0x0070);
283 	mask_fc |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
284 
285 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
286 	len_a = hdrlen - 2;
287 	a4_included = ieee80211_has_a4(hdr->frame_control);
288 
289 	if (ieee80211_is_data_qos(hdr->frame_control))
290 		qos_tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
291 	else
292 		qos_tid = 0;
293 
294 	data_len = skb->len - hdrlen - CCMP_HDR_LEN;
295 	if (encrypted)
296 		data_len -= CCMP_MIC_LEN;
297 
298 	/* First block, b_0 */
299 	b_0[0] = 0x59; /* flags: Adata: 1, M: 011, L: 001 */
300 	/* Nonce: Nonce Flags | A2 | PN
301 	 * Nonce Flags: Priority (b0..b3) | Management (b4) | Reserved (b5..b7)
302 	 */
303 	b_0[1] = qos_tid | (mgmt << 4);
304 	memcpy(&b_0[2], hdr->addr2, ETH_ALEN);
305 	memcpy(&b_0[8], pn, CCMP_PN_LEN);
306 	/* l(m) */
307 	put_unaligned_be16(data_len, &b_0[14]);
308 
309 	/* AAD (extra authenticate-only data) / masked 802.11 header
310 	 * FC | A1 | A2 | A3 | SC | [A4] | [QC] */
311 	put_unaligned_be16(len_a, &aad[0]);
312 	put_unaligned(mask_fc, (__le16 *)&aad[2]);
313 	memcpy(&aad[4], &hdr->addr1, 3 * ETH_ALEN);
314 
315 	/* Mask Seq#, leave Frag# */
316 	aad[22] = *((u8 *) &hdr->seq_ctrl) & 0x0f;
317 	aad[23] = 0;
318 
319 	if (a4_included) {
320 		memcpy(&aad[24], hdr->addr4, ETH_ALEN);
321 		aad[30] = qos_tid;
322 		aad[31] = 0;
323 	} else {
324 		memset(&aad[24], 0, ETH_ALEN + IEEE80211_QOS_CTL_LEN);
325 		aad[24] = qos_tid;
326 	}
327 }
328 
329 
330 static inline void ccmp_pn2hdr(u8 *hdr, u8 *pn, int key_id)
331 {
332 	hdr[0] = pn[5];
333 	hdr[1] = pn[4];
334 	hdr[2] = 0;
335 	hdr[3] = 0x20 | (key_id << 6);
336 	hdr[4] = pn[3];
337 	hdr[5] = pn[2];
338 	hdr[6] = pn[1];
339 	hdr[7] = pn[0];
340 }
341 
342 
343 static inline void ccmp_hdr2pn(u8 *pn, u8 *hdr)
344 {
345 	pn[0] = hdr[7];
346 	pn[1] = hdr[6];
347 	pn[2] = hdr[5];
348 	pn[3] = hdr[4];
349 	pn[4] = hdr[1];
350 	pn[5] = hdr[0];
351 }
352 
353 
354 static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
355 {
356 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
357 	struct ieee80211_key *key = tx->key;
358 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
359 	int hdrlen, len, tail;
360 	u8 *pos, *pn;
361 	int i;
362 
363 	if (info->control.hw_key &&
364 	    !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
365 		/*
366 		 * hwaccel has no need for preallocated room for CCMP
367 		 * header or MIC fields
368 		 */
369 		return 0;
370 	}
371 
372 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
373 	len = skb->len - hdrlen;
374 
375 	if (info->control.hw_key)
376 		tail = 0;
377 	else
378 		tail = CCMP_MIC_LEN;
379 
380 	if (WARN_ON(skb_tailroom(skb) < tail ||
381 		    skb_headroom(skb) < CCMP_HDR_LEN))
382 		return -1;
383 
384 	pos = skb_push(skb, CCMP_HDR_LEN);
385 	memmove(pos, pos + CCMP_HDR_LEN, hdrlen);
386 	hdr = (struct ieee80211_hdr *) pos;
387 	pos += hdrlen;
388 
389 	/* PN = PN + 1 */
390 	pn = key->u.ccmp.tx_pn;
391 
392 	for (i = CCMP_PN_LEN - 1; i >= 0; i--) {
393 		pn[i]++;
394 		if (pn[i])
395 			break;
396 	}
397 
398 	ccmp_pn2hdr(pos, pn, key->conf.keyidx);
399 
400 	/* hwaccel - with software CCMP header */
401 	if (info->control.hw_key)
402 		return 0;
403 
404 	pos += CCMP_HDR_LEN;
405 	ccmp_special_blocks(skb, pn, key->u.ccmp.tx_crypto_buf, 0);
406 	ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, key->u.ccmp.tx_crypto_buf, pos, len,
407 				  pos, skb_put(skb, CCMP_MIC_LEN));
408 
409 	return 0;
410 }
411 
412 
413 ieee80211_tx_result
414 ieee80211_crypto_ccmp_encrypt(struct ieee80211_tx_data *tx)
415 {
416 	struct sk_buff *skb = tx->skb;
417 
418 	ieee80211_tx_set_protected(tx);
419 
420 	do {
421 		if (ccmp_encrypt_skb(tx, skb) < 0)
422 			return TX_DROP;
423 	} while ((skb = skb->next));
424 
425 	return TX_CONTINUE;
426 }
427 
428 
429 ieee80211_rx_result
430 ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
431 {
432 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
433 	int hdrlen;
434 	struct ieee80211_key *key = rx->key;
435 	struct sk_buff *skb = rx->skb;
436 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
437 	u8 pn[CCMP_PN_LEN];
438 	int data_len;
439 
440 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
441 
442 	if (!ieee80211_is_data(hdr->frame_control) &&
443 	    !ieee80211_is_robust_mgmt_frame(hdr))
444 		return RX_CONTINUE;
445 
446 	data_len = skb->len - hdrlen - CCMP_HDR_LEN - CCMP_MIC_LEN;
447 	if (!rx->sta || data_len < 0)
448 		return RX_DROP_UNUSABLE;
449 
450 	if ((status->flag & RX_FLAG_DECRYPTED) &&
451 	    (status->flag & RX_FLAG_IV_STRIPPED))
452 		return RX_CONTINUE;
453 
454 	ccmp_hdr2pn(pn, skb->data + hdrlen);
455 
456 	if (memcmp(pn, key->u.ccmp.rx_pn[rx->queue], CCMP_PN_LEN) <= 0) {
457 		key->u.ccmp.replays++;
458 		return RX_DROP_UNUSABLE;
459 	}
460 
461 	if (!(status->flag & RX_FLAG_DECRYPTED)) {
462 		/* hardware didn't decrypt/verify MIC */
463 		ccmp_special_blocks(skb, pn, key->u.ccmp.rx_crypto_buf, 1);
464 
465 		if (ieee80211_aes_ccm_decrypt(
466 			    key->u.ccmp.tfm, key->u.ccmp.rx_crypto_buf,
467 			    skb->data + hdrlen + CCMP_HDR_LEN, data_len,
468 			    skb->data + skb->len - CCMP_MIC_LEN,
469 			    skb->data + hdrlen + CCMP_HDR_LEN))
470 			return RX_DROP_UNUSABLE;
471 	}
472 
473 	memcpy(key->u.ccmp.rx_pn[rx->queue], pn, CCMP_PN_LEN);
474 
475 	/* Remove CCMP header and MIC */
476 	skb_trim(skb, skb->len - CCMP_MIC_LEN);
477 	memmove(skb->data + CCMP_HDR_LEN, skb->data, hdrlen);
478 	skb_pull(skb, CCMP_HDR_LEN);
479 
480 	return RX_CONTINUE;
481 }
482 
483 
484 static void bip_aad(struct sk_buff *skb, u8 *aad)
485 {
486 	/* BIP AAD: FC(masked) || A1 || A2 || A3 */
487 
488 	/* FC type/subtype */
489 	aad[0] = skb->data[0];
490 	/* Mask FC Retry, PwrMgt, MoreData flags to zero */
491 	aad[1] = skb->data[1] & ~(BIT(4) | BIT(5) | BIT(6));
492 	/* A1 || A2 || A3 */
493 	memcpy(aad + 2, skb->data + 4, 3 * ETH_ALEN);
494 }
495 
496 
497 static inline void bip_ipn_swap(u8 *d, const u8 *s)
498 {
499 	*d++ = s[5];
500 	*d++ = s[4];
501 	*d++ = s[3];
502 	*d++ = s[2];
503 	*d++ = s[1];
504 	*d = s[0];
505 }
506 
507 
508 ieee80211_tx_result
509 ieee80211_crypto_aes_cmac_encrypt(struct ieee80211_tx_data *tx)
510 {
511 	struct sk_buff *skb = tx->skb;
512 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
513 	struct ieee80211_key *key = tx->key;
514 	struct ieee80211_mmie *mmie;
515 	u8 *pn, aad[20];
516 	int i;
517 
518 	if (info->control.hw_key)
519 		return 0;
520 
521 	if (WARN_ON(skb_tailroom(skb) < sizeof(*mmie)))
522 		return TX_DROP;
523 
524 	mmie = (struct ieee80211_mmie *) skb_put(skb, sizeof(*mmie));
525 	mmie->element_id = WLAN_EID_MMIE;
526 	mmie->length = sizeof(*mmie) - 2;
527 	mmie->key_id = cpu_to_le16(key->conf.keyidx);
528 
529 	/* PN = PN + 1 */
530 	pn = key->u.aes_cmac.tx_pn;
531 
532 	for (i = sizeof(key->u.aes_cmac.tx_pn) - 1; i >= 0; i--) {
533 		pn[i]++;
534 		if (pn[i])
535 			break;
536 	}
537 	bip_ipn_swap(mmie->sequence_number, pn);
538 
539 	bip_aad(skb, aad);
540 
541 	/*
542 	 * MIC = AES-128-CMAC(IGTK, AAD || Management Frame Body || MMIE, 64)
543 	 */
544 	ieee80211_aes_cmac(key->u.aes_cmac.tfm, key->u.aes_cmac.tx_crypto_buf,
545 			   aad, skb->data + 24, skb->len - 24, mmie->mic);
546 
547 	return TX_CONTINUE;
548 }
549 
550 
551 ieee80211_rx_result
552 ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
553 {
554 	struct sk_buff *skb = rx->skb;
555 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
556 	struct ieee80211_key *key = rx->key;
557 	struct ieee80211_mmie *mmie;
558 	u8 aad[20], mic[8], ipn[6];
559 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
560 
561 	if (!ieee80211_is_mgmt(hdr->frame_control))
562 		return RX_CONTINUE;
563 
564 	if ((status->flag & RX_FLAG_DECRYPTED) &&
565 	    (status->flag & RX_FLAG_IV_STRIPPED))
566 		return RX_CONTINUE;
567 
568 	if (skb->len < 24 + sizeof(*mmie))
569 		return RX_DROP_UNUSABLE;
570 
571 	mmie = (struct ieee80211_mmie *)
572 		(skb->data + skb->len - sizeof(*mmie));
573 	if (mmie->element_id != WLAN_EID_MMIE ||
574 	    mmie->length != sizeof(*mmie) - 2)
575 		return RX_DROP_UNUSABLE; /* Invalid MMIE */
576 
577 	bip_ipn_swap(ipn, mmie->sequence_number);
578 
579 	if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
580 		key->u.aes_cmac.replays++;
581 		return RX_DROP_UNUSABLE;
582 	}
583 
584 	if (!(status->flag & RX_FLAG_DECRYPTED)) {
585 		/* hardware didn't decrypt/verify MIC */
586 		bip_aad(skb, aad);
587 		ieee80211_aes_cmac(key->u.aes_cmac.tfm,
588 				   key->u.aes_cmac.rx_crypto_buf, aad,
589 				   skb->data + 24, skb->len - 24, mic);
590 		if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
591 			key->u.aes_cmac.icverrors++;
592 			return RX_DROP_UNUSABLE;
593 		}
594 	}
595 
596 	memcpy(key->u.aes_cmac.rx_pn, ipn, 6);
597 
598 	/* Remove MMIE */
599 	skb_trim(skb, skb->len - sizeof(*mmie));
600 
601 	return RX_CONTINUE;
602 }
603