xref: /openbmc/linux/net/mac80211/wpa.c (revision 5499b451) 
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/slab.h>
13 #include <linux/skbuff.h>
14 #include <linux/compiler.h>
15 #include <linux/ieee80211.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 	int authenticator;
35 	int wpa_test = 0;
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 ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
51 	    !(tx->flags & IEEE80211_TX_FRAGMENTED) &&
52 	    !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_MMIC) &&
53 	    !wpa_test) {
54 		/* hwaccel - with no need for preallocated room for MMIC */
55 		return TX_CONTINUE;
56 	}
57 
58 	tail = MICHAEL_MIC_LEN;
59 	if (!(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE))
60 		tail += TKIP_ICV_LEN;
61 
62 	if (WARN_ON(skb_tailroom(skb) < tail ||
63 		    skb_headroom(skb) < TKIP_IV_LEN))
64 		return TX_DROP;
65 
66 #if 0
67 	authenticator = fc & IEEE80211_FCTL_FROMDS; /* FIX */
68 #else
69 	authenticator = 1;
70 #endif
71 	key_offset = authenticator ?
72 		NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY :
73 		NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY;
74 	key = &tx->key->conf.key[key_offset];
75 	mic = skb_put(skb, MICHAEL_MIC_LEN);
76 	michael_mic(key, hdr, data, data_len, mic);
77 
78 	return TX_CONTINUE;
79 }
80 
81 
82 ieee80211_rx_result
83 ieee80211_rx_h_michael_mic_verify(struct ieee80211_rx_data *rx)
84 {
85 	u8 *data, *key = NULL, key_offset;
86 	size_t data_len;
87 	unsigned int hdrlen;
88 	u8 mic[MICHAEL_MIC_LEN];
89 	struct sk_buff *skb = rx->skb;
90 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
91 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
92 	int authenticator = 1, wpa_test = 0;
93 
94 	/* No way to verify the MIC if the hardware stripped it */
95 	if (status->flag & RX_FLAG_MMIC_STRIPPED)
96 		return RX_CONTINUE;
97 
98 	if (!rx->key || rx->key->conf.alg != ALG_TKIP ||
99 	    !ieee80211_has_protected(hdr->frame_control) ||
100 	    !ieee80211_is_data_present(hdr->frame_control))
101 		return RX_CONTINUE;
102 
103 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
104 	if (skb->len < hdrlen + MICHAEL_MIC_LEN)
105 		return RX_DROP_UNUSABLE;
106 
107 	data = skb->data + hdrlen;
108 	data_len = skb->len - hdrlen - MICHAEL_MIC_LEN;
109 
110 #if 0
111 	authenticator = fc & IEEE80211_FCTL_TODS; /* FIX */
112 #else
113 	authenticator = 1;
114 #endif
115 	key_offset = authenticator ?
116 		NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY :
117 		NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY;
118 	key = &rx->key->conf.key[key_offset];
119 	michael_mic(key, hdr, data, data_len, mic);
120 	if (memcmp(mic, data + data_len, MICHAEL_MIC_LEN) != 0 || wpa_test) {
121 		if (!(rx->flags & IEEE80211_RX_RA_MATCH))
122 			return RX_DROP_UNUSABLE;
123 
124 		mac80211_ev_michael_mic_failure(rx->sdata, rx->key->conf.keyidx,
125 						(void *) skb->data, NULL,
126 						GFP_ATOMIC);
127 		return RX_DROP_UNUSABLE;
128 	}
129 
130 	/* remove Michael MIC from payload */
131 	skb_trim(skb, skb->len - MICHAEL_MIC_LEN);
132 
133 	/* update IV in key information to be able to detect replays */
134 	rx->key->u.tkip.rx[rx->queue].iv32 = rx->tkip_iv32;
135 	rx->key->u.tkip.rx[rx->queue].iv16 = rx->tkip_iv16;
136 
137 	return RX_CONTINUE;
138 }
139 
140 
141 static int tkip_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
142 {
143 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
144 	struct ieee80211_key *key = tx->key;
145 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
146 	unsigned int hdrlen;
147 	int len, tail;
148 	u8 *pos;
149 
150 	if ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
151 	    !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
152 		/* hwaccel - with no need for preallocated room for IV/ICV */
153 		info->control.hw_key = &tx->key->conf;
154 		return 0;
155 	}
156 
157 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
158 	len = skb->len - hdrlen;
159 
160 	if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)
161 		tail = 0;
162 	else
163 		tail = TKIP_ICV_LEN;
164 
165 	if (WARN_ON(skb_tailroom(skb) < tail ||
166 		    skb_headroom(skb) < TKIP_IV_LEN))
167 		return -1;
168 
169 	pos = skb_push(skb, TKIP_IV_LEN);
170 	memmove(pos, pos + TKIP_IV_LEN, hdrlen);
171 	pos += hdrlen;
172 
173 	/* Increase IV for the frame */
174 	key->u.tkip.tx.iv16++;
175 	if (key->u.tkip.tx.iv16 == 0)
176 		key->u.tkip.tx.iv32++;
177 
178 	if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) {
179 		/* hwaccel - with preallocated room for IV */
180 		ieee80211_tkip_add_iv(pos, key, key->u.tkip.tx.iv16);
181 
182 		info->control.hw_key = &tx->key->conf;
183 		return 0;
184 	}
185 
186 	/* Add room for ICV */
187 	skb_put(skb, TKIP_ICV_LEN);
188 
189 	hdr = (struct ieee80211_hdr *) skb->data;
190 	ieee80211_tkip_encrypt_data(tx->local->wep_tx_tfm,
191 				    key, pos, len, hdr->addr2);
192 	return 0;
193 }
194 
195 
196 ieee80211_tx_result
197 ieee80211_crypto_tkip_encrypt(struct ieee80211_tx_data *tx)
198 {
199 	struct sk_buff *skb = tx->skb;
200 
201 	ieee80211_tx_set_protected(tx);
202 
203 	do {
204 		if (tkip_encrypt_skb(tx, skb) < 0)
205 			return TX_DROP;
206 	} while ((skb = skb->next));
207 
208 	return TX_CONTINUE;
209 }
210 
211 
212 ieee80211_rx_result
213 ieee80211_crypto_tkip_decrypt(struct ieee80211_rx_data *rx)
214 {
215 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) rx->skb->data;
216 	int hdrlen, res, hwaccel = 0, wpa_test = 0;
217 	struct ieee80211_key *key = rx->key;
218 	struct sk_buff *skb = rx->skb;
219 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
220 
221 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
222 
223 	if (!ieee80211_is_data(hdr->frame_control))
224 		return RX_CONTINUE;
225 
226 	if (!rx->sta || skb->len - hdrlen < 12)
227 		return RX_DROP_UNUSABLE;
228 
229 	if (status->flag & RX_FLAG_DECRYPTED) {
230 		if (status->flag & RX_FLAG_IV_STRIPPED) {
231 			/*
232 			 * Hardware took care of all processing, including
233 			 * replay protection, and stripped the ICV/IV so
234 			 * we cannot do any checks here.
235 			 */
236 			return RX_CONTINUE;
237 		}
238 
239 		/* let TKIP code verify IV, but skip decryption */
240 		hwaccel = 1;
241 	}
242 
243 	res = ieee80211_tkip_decrypt_data(rx->local->wep_rx_tfm,
244 					  key, skb->data + hdrlen,
245 					  skb->len - hdrlen, rx->sta->sta.addr,
246 					  hdr->addr1, hwaccel, rx->queue,
247 					  &rx->tkip_iv32,
248 					  &rx->tkip_iv16);
249 	if (res != TKIP_DECRYPT_OK || wpa_test)
250 		return RX_DROP_UNUSABLE;
251 
252 	/* Trim ICV */
253 	skb_trim(skb, skb->len - TKIP_ICV_LEN);
254 
255 	/* Remove IV */
256 	memmove(skb->data + TKIP_IV_LEN, skb->data, hdrlen);
257 	skb_pull(skb, TKIP_IV_LEN);
258 
259 	return RX_CONTINUE;
260 }
261 
262 
263 static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
264 				int encrypted)
265 {
266 	__le16 mask_fc;
267 	int a4_included, mgmt;
268 	u8 qos_tid;
269 	u8 *b_0, *aad;
270 	u16 data_len, len_a;
271 	unsigned int hdrlen;
272 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
273 
274 	b_0 = scratch + 3 * AES_BLOCK_LEN;
275 	aad = scratch + 4 * AES_BLOCK_LEN;
276 
277 	/*
278 	 * Mask FC: zero subtype b4 b5 b6 (if not mgmt)
279 	 * Retry, PwrMgt, MoreData; set Protected
280 	 */
281 	mgmt = ieee80211_is_mgmt(hdr->frame_control);
282 	mask_fc = hdr->frame_control;
283 	mask_fc &= ~cpu_to_le16(IEEE80211_FCTL_RETRY |
284 				IEEE80211_FCTL_PM | IEEE80211_FCTL_MOREDATA);
285 	if (!mgmt)
286 		mask_fc &= ~cpu_to_le16(0x0070);
287 	mask_fc |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
288 
289 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
290 	len_a = hdrlen - 2;
291 	a4_included = ieee80211_has_a4(hdr->frame_control);
292 
293 	if (ieee80211_is_data_qos(hdr->frame_control))
294 		qos_tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
295 	else
296 		qos_tid = 0;
297 
298 	data_len = skb->len - hdrlen - CCMP_HDR_LEN;
299 	if (encrypted)
300 		data_len -= CCMP_MIC_LEN;
301 
302 	/* First block, b_0 */
303 	b_0[0] = 0x59; /* flags: Adata: 1, M: 011, L: 001 */
304 	/* Nonce: Nonce Flags | A2 | PN
305 	 * Nonce Flags: Priority (b0..b3) | Management (b4) | Reserved (b5..b7)
306 	 */
307 	b_0[1] = qos_tid | (mgmt << 4);
308 	memcpy(&b_0[2], hdr->addr2, ETH_ALEN);
309 	memcpy(&b_0[8], pn, CCMP_PN_LEN);
310 	/* l(m) */
311 	put_unaligned_be16(data_len, &b_0[14]);
312 
313 	/* AAD (extra authenticate-only data) / masked 802.11 header
314 	 * FC | A1 | A2 | A3 | SC | [A4] | [QC] */
315 	put_unaligned_be16(len_a, &aad[0]);
316 	put_unaligned(mask_fc, (__le16 *)&aad[2]);
317 	memcpy(&aad[4], &hdr->addr1, 3 * ETH_ALEN);
318 
319 	/* Mask Seq#, leave Frag# */
320 	aad[22] = *((u8 *) &hdr->seq_ctrl) & 0x0f;
321 	aad[23] = 0;
322 
323 	if (a4_included) {
324 		memcpy(&aad[24], hdr->addr4, ETH_ALEN);
325 		aad[30] = qos_tid;
326 		aad[31] = 0;
327 	} else {
328 		memset(&aad[24], 0, ETH_ALEN + IEEE80211_QOS_CTL_LEN);
329 		aad[24] = qos_tid;
330 	}
331 }
332 
333 
334 static inline void ccmp_pn2hdr(u8 *hdr, u8 *pn, int key_id)
335 {
336 	hdr[0] = pn[5];
337 	hdr[1] = pn[4];
338 	hdr[2] = 0;
339 	hdr[3] = 0x20 | (key_id << 6);
340 	hdr[4] = pn[3];
341 	hdr[5] = pn[2];
342 	hdr[6] = pn[1];
343 	hdr[7] = pn[0];
344 }
345 
346 
347 static inline void ccmp_hdr2pn(u8 *pn, u8 *hdr)
348 {
349 	pn[0] = hdr[7];
350 	pn[1] = hdr[6];
351 	pn[2] = hdr[5];
352 	pn[3] = hdr[4];
353 	pn[4] = hdr[1];
354 	pn[5] = hdr[0];
355 }
356 
357 
358 static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
359 {
360 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
361 	struct ieee80211_key *key = tx->key;
362 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
363 	int hdrlen, len, tail;
364 	u8 *pos, *pn;
365 	int i;
366 	bool skip_hw;
367 
368 	skip_hw = (tx->key->conf.flags & IEEE80211_KEY_FLAG_SW_MGMT) &&
369 		ieee80211_is_mgmt(hdr->frame_control);
370 
371 	if ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
372 	    !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) &&
373 	    !skip_hw) {
374 		/* hwaccel - with no need for preallocated room for CCMP
375 		 * header or MIC fields */
376 		info->control.hw_key = &tx->key->conf;
377 		return 0;
378 	}
379 
380 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
381 	len = skb->len - hdrlen;
382 
383 	if (key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)
384 		tail = 0;
385 	else
386 		tail = CCMP_MIC_LEN;
387 
388 	if (WARN_ON(skb_tailroom(skb) < tail ||
389 		    skb_headroom(skb) < CCMP_HDR_LEN))
390 		return -1;
391 
392 	pos = skb_push(skb, CCMP_HDR_LEN);
393 	memmove(pos, pos + CCMP_HDR_LEN, hdrlen);
394 	hdr = (struct ieee80211_hdr *) pos;
395 	pos += hdrlen;
396 
397 	/* PN = PN + 1 */
398 	pn = key->u.ccmp.tx_pn;
399 
400 	for (i = CCMP_PN_LEN - 1; i >= 0; i--) {
401 		pn[i]++;
402 		if (pn[i])
403 			break;
404 	}
405 
406 	ccmp_pn2hdr(pos, pn, key->conf.keyidx);
407 
408 	if ((key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) && !skip_hw) {
409 		/* hwaccel - with preallocated room for CCMP header */
410 		info->control.hw_key = &tx->key->conf;
411 		return 0;
412 	}
413 
414 	pos += CCMP_HDR_LEN;
415 	ccmp_special_blocks(skb, pn, key->u.ccmp.tx_crypto_buf, 0);
416 	ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, key->u.ccmp.tx_crypto_buf, pos, len,
417 				  pos, skb_put(skb, CCMP_MIC_LEN));
418 
419 	return 0;
420 }
421 
422 
423 ieee80211_tx_result
424 ieee80211_crypto_ccmp_encrypt(struct ieee80211_tx_data *tx)
425 {
426 	struct sk_buff *skb = tx->skb;
427 
428 	ieee80211_tx_set_protected(tx);
429 
430 	do {
431 		if (ccmp_encrypt_skb(tx, skb) < 0)
432 			return TX_DROP;
433 	} while ((skb = skb->next));
434 
435 	return TX_CONTINUE;
436 }
437 
438 
439 ieee80211_rx_result
440 ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
441 {
442 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
443 	int hdrlen;
444 	struct ieee80211_key *key = rx->key;
445 	struct sk_buff *skb = rx->skb;
446 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
447 	u8 pn[CCMP_PN_LEN];
448 	int data_len;
449 
450 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
451 
452 	if (!ieee80211_is_data(hdr->frame_control) &&
453 	    !ieee80211_is_robust_mgmt_frame(hdr))
454 		return RX_CONTINUE;
455 
456 	data_len = skb->len - hdrlen - CCMP_HDR_LEN - CCMP_MIC_LEN;
457 	if (!rx->sta || data_len < 0)
458 		return RX_DROP_UNUSABLE;
459 
460 	if ((status->flag & RX_FLAG_DECRYPTED) &&
461 	    (status->flag & RX_FLAG_IV_STRIPPED))
462 		return RX_CONTINUE;
463 
464 	ccmp_hdr2pn(pn, skb->data + hdrlen);
465 
466 	if (memcmp(pn, key->u.ccmp.rx_pn[rx->queue], CCMP_PN_LEN) <= 0) {
467 		key->u.ccmp.replays++;
468 		return RX_DROP_UNUSABLE;
469 	}
470 
471 	if (!(status->flag & RX_FLAG_DECRYPTED)) {
472 		/* hardware didn't decrypt/verify MIC */
473 		ccmp_special_blocks(skb, pn, key->u.ccmp.rx_crypto_buf, 1);
474 
475 		if (ieee80211_aes_ccm_decrypt(
476 			    key->u.ccmp.tfm, key->u.ccmp.rx_crypto_buf,
477 			    skb->data + hdrlen + CCMP_HDR_LEN, data_len,
478 			    skb->data + skb->len - CCMP_MIC_LEN,
479 			    skb->data + hdrlen + CCMP_HDR_LEN))
480 			return RX_DROP_UNUSABLE;
481 	}
482 
483 	memcpy(key->u.ccmp.rx_pn[rx->queue], pn, CCMP_PN_LEN);
484 
485 	/* Remove CCMP header and MIC */
486 	skb_trim(skb, skb->len - CCMP_MIC_LEN);
487 	memmove(skb->data + CCMP_HDR_LEN, skb->data, hdrlen);
488 	skb_pull(skb, CCMP_HDR_LEN);
489 
490 	return RX_CONTINUE;
491 }
492 
493 
494 static void bip_aad(struct sk_buff *skb, u8 *aad)
495 {
496 	/* BIP AAD: FC(masked) || A1 || A2 || A3 */
497 
498 	/* FC type/subtype */
499 	aad[0] = skb->data[0];
500 	/* Mask FC Retry, PwrMgt, MoreData flags to zero */
501 	aad[1] = skb->data[1] & ~(BIT(4) | BIT(5) | BIT(6));
502 	/* A1 || A2 || A3 */
503 	memcpy(aad + 2, skb->data + 4, 3 * ETH_ALEN);
504 }
505 
506 
507 static inline void bip_ipn_swap(u8 *d, const u8 *s)
508 {
509 	*d++ = s[5];
510 	*d++ = s[4];
511 	*d++ = s[3];
512 	*d++ = s[2];
513 	*d++ = s[1];
514 	*d = s[0];
515 }
516 
517 
518 ieee80211_tx_result
519 ieee80211_crypto_aes_cmac_encrypt(struct ieee80211_tx_data *tx)
520 {
521 	struct sk_buff *skb = tx->skb;
522 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
523 	struct ieee80211_key *key = tx->key;
524 	struct ieee80211_mmie *mmie;
525 	u8 *pn, aad[20];
526 	int i;
527 
528 	if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) {
529 		/* hwaccel */
530 		info->control.hw_key = &tx->key->conf;
531 		return 0;
532 	}
533 
534 	if (WARN_ON(skb_tailroom(skb) < sizeof(*mmie)))
535 		return TX_DROP;
536 
537 	mmie = (struct ieee80211_mmie *) skb_put(skb, sizeof(*mmie));
538 	mmie->element_id = WLAN_EID_MMIE;
539 	mmie->length = sizeof(*mmie) - 2;
540 	mmie->key_id = cpu_to_le16(key->conf.keyidx);
541 
542 	/* PN = PN + 1 */
543 	pn = key->u.aes_cmac.tx_pn;
544 
545 	for (i = sizeof(key->u.aes_cmac.tx_pn) - 1; i >= 0; i--) {
546 		pn[i]++;
547 		if (pn[i])
548 			break;
549 	}
550 	bip_ipn_swap(mmie->sequence_number, pn);
551 
552 	bip_aad(skb, aad);
553 
554 	/*
555 	 * MIC = AES-128-CMAC(IGTK, AAD || Management Frame Body || MMIE, 64)
556 	 */
557 	ieee80211_aes_cmac(key->u.aes_cmac.tfm, key->u.aes_cmac.tx_crypto_buf,
558 			   aad, skb->data + 24, skb->len - 24, mmie->mic);
559 
560 	return TX_CONTINUE;
561 }
562 
563 
564 ieee80211_rx_result
565 ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
566 {
567 	struct sk_buff *skb = rx->skb;
568 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
569 	struct ieee80211_key *key = rx->key;
570 	struct ieee80211_mmie *mmie;
571 	u8 aad[20], mic[8], ipn[6];
572 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
573 
574 	if (!ieee80211_is_mgmt(hdr->frame_control))
575 		return RX_CONTINUE;
576 
577 	if ((status->flag & RX_FLAG_DECRYPTED) &&
578 	    (status->flag & RX_FLAG_IV_STRIPPED))
579 		return RX_CONTINUE;
580 
581 	if (skb->len < 24 + sizeof(*mmie))
582 		return RX_DROP_UNUSABLE;
583 
584 	mmie = (struct ieee80211_mmie *)
585 		(skb->data + skb->len - sizeof(*mmie));
586 	if (mmie->element_id != WLAN_EID_MMIE ||
587 	    mmie->length != sizeof(*mmie) - 2)
588 		return RX_DROP_UNUSABLE; /* Invalid MMIE */
589 
590 	bip_ipn_swap(ipn, mmie->sequence_number);
591 
592 	if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
593 		key->u.aes_cmac.replays++;
594 		return RX_DROP_UNUSABLE;
595 	}
596 
597 	if (!(status->flag & RX_FLAG_DECRYPTED)) {
598 		/* hardware didn't decrypt/verify MIC */
599 		bip_aad(skb, aad);
600 		ieee80211_aes_cmac(key->u.aes_cmac.tfm,
601 				   key->u.aes_cmac.rx_crypto_buf, aad,
602 				   skb->data + 24, skb->len - 24, mic);
603 		if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
604 			key->u.aes_cmac.icverrors++;
605 			return RX_DROP_UNUSABLE;
606 		}
607 	}
608 
609 	memcpy(key->u.aes_cmac.rx_pn, ipn, 6);
610 
611 	/* Remove MMIE */
612 	skb_trim(skb, skb->len - sizeof(*mmie));
613 
614 	return RX_CONTINUE;
615 }
616