xref: /openbmc/linux/net/mac80211/wpa.c (revision b8bb76713ec50df2f11efee386e16f93d51e1076) 
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 	struct ieee80211_hdr *hdr;
89 	u8 mic[MICHAEL_MIC_LEN];
90 	struct sk_buff *skb = rx->skb;
91 	int authenticator = 1, wpa_test = 0;
92 
93 	/* No way to verify the MIC if the hardware stripped it */
94 	if (rx->status->flag & RX_FLAG_MMIC_STRIPPED)
95 		return RX_CONTINUE;
96 
97 	hdr = (struct ieee80211_hdr *)skb->data;
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);
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 ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
150 	    !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
151 		/* hwaccel - with no need for preallocated room for IV/ICV */
152 		info->control.hw_key = &tx->key->conf;
153 		return 0;
154 	}
155 
156 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
157 	len = skb->len - hdrlen;
158 
159 	if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)
160 		tail = 0;
161 	else
162 		tail = TKIP_ICV_LEN;
163 
164 	if (WARN_ON(skb_tailroom(skb) < tail ||
165 		    skb_headroom(skb) < TKIP_IV_LEN))
166 		return -1;
167 
168 	pos = skb_push(skb, TKIP_IV_LEN);
169 	memmove(pos, pos + TKIP_IV_LEN, hdrlen);
170 	pos += hdrlen;
171 
172 	/* Increase IV for the frame */
173 	key->u.tkip.tx.iv16++;
174 	if (key->u.tkip.tx.iv16 == 0)
175 		key->u.tkip.tx.iv32++;
176 
177 	if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) {
178 		/* hwaccel - with preallocated room for IV */
179 		ieee80211_tkip_add_iv(pos, key, key->u.tkip.tx.iv16);
180 
181 		info->control.hw_key = &tx->key->conf;
182 		return 0;
183 	}
184 
185 	/* Add room for ICV */
186 	skb_put(skb, TKIP_ICV_LEN);
187 
188 	hdr = (struct ieee80211_hdr *) skb->data;
189 	ieee80211_tkip_encrypt_data(tx->local->wep_tx_tfm,
190 				    key, pos, len, hdr->addr2);
191 	return 0;
192 }
193 
194 
195 ieee80211_tx_result
196 ieee80211_crypto_tkip_encrypt(struct ieee80211_tx_data *tx)
197 {
198 	struct sk_buff *skb = tx->skb;
199 
200 	ieee80211_tx_set_protected(tx);
201 
202 	do {
203 		if (tkip_encrypt_skb(tx, skb) < 0)
204 			return TX_DROP;
205 	} while ((skb = skb->next));
206 
207 	return TX_CONTINUE;
208 }
209 
210 
211 ieee80211_rx_result
212 ieee80211_crypto_tkip_decrypt(struct ieee80211_rx_data *rx)
213 {
214 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) rx->skb->data;
215 	int hdrlen, res, hwaccel = 0, wpa_test = 0;
216 	struct ieee80211_key *key = rx->key;
217 	struct sk_buff *skb = rx->skb;
218 
219 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
220 
221 	if (!ieee80211_is_data(hdr->frame_control))
222 		return RX_CONTINUE;
223 
224 	if (!rx->sta || skb->len - hdrlen < 12)
225 		return RX_DROP_UNUSABLE;
226 
227 	if (rx->status->flag & RX_FLAG_DECRYPTED) {
228 		if (rx->status->flag & RX_FLAG_IV_STRIPPED) {
229 			/*
230 			 * Hardware took care of all processing, including
231 			 * replay protection, and stripped the ICV/IV so
232 			 * we cannot do any checks here.
233 			 */
234 			return RX_CONTINUE;
235 		}
236 
237 		/* let TKIP code verify IV, but skip decryption */
238 		hwaccel = 1;
239 	}
240 
241 	res = ieee80211_tkip_decrypt_data(rx->local->wep_rx_tfm,
242 					  key, skb->data + hdrlen,
243 					  skb->len - hdrlen, rx->sta->sta.addr,
244 					  hdr->addr1, hwaccel, rx->queue,
245 					  &rx->tkip_iv32,
246 					  &rx->tkip_iv16);
247 	if (res != TKIP_DECRYPT_OK || wpa_test)
248 		return RX_DROP_UNUSABLE;
249 
250 	/* Trim ICV */
251 	skb_trim(skb, skb->len - TKIP_ICV_LEN);
252 
253 	/* Remove IV */
254 	memmove(skb->data + TKIP_IV_LEN, skb->data, hdrlen);
255 	skb_pull(skb, TKIP_IV_LEN);
256 
257 	return RX_CONTINUE;
258 }
259 
260 
261 static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
262 				int encrypted)
263 {
264 	__le16 mask_fc;
265 	int a4_included, mgmt;
266 	u8 qos_tid;
267 	u8 *b_0, *aad;
268 	u16 data_len, len_a;
269 	unsigned int hdrlen;
270 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
271 
272 	b_0 = scratch + 3 * AES_BLOCK_LEN;
273 	aad = scratch + 4 * AES_BLOCK_LEN;
274 
275 	/*
276 	 * Mask FC: zero subtype b4 b5 b6 (if not mgmt)
277 	 * Retry, PwrMgt, MoreData; set Protected
278 	 */
279 	mgmt = ieee80211_is_mgmt(hdr->frame_control);
280 	mask_fc = hdr->frame_control;
281 	mask_fc &= ~cpu_to_le16(IEEE80211_FCTL_RETRY |
282 				IEEE80211_FCTL_PM | IEEE80211_FCTL_MOREDATA);
283 	if (!mgmt)
284 		mask_fc &= ~cpu_to_le16(0x0070);
285 	mask_fc |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
286 
287 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
288 	len_a = hdrlen - 2;
289 	a4_included = ieee80211_has_a4(hdr->frame_control);
290 
291 	if (ieee80211_is_data_qos(hdr->frame_control))
292 		qos_tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
293 	else
294 		qos_tid = 0;
295 
296 	data_len = skb->len - hdrlen - CCMP_HDR_LEN;
297 	if (encrypted)
298 		data_len -= CCMP_MIC_LEN;
299 
300 	/* First block, b_0 */
301 	b_0[0] = 0x59; /* flags: Adata: 1, M: 011, L: 001 */
302 	/* Nonce: Nonce Flags | A2 | PN
303 	 * Nonce Flags: Priority (b0..b3) | Management (b4) | Reserved (b5..b7)
304 	 */
305 	b_0[1] = qos_tid | (mgmt << 4);
306 	memcpy(&b_0[2], hdr->addr2, ETH_ALEN);
307 	memcpy(&b_0[8], pn, CCMP_PN_LEN);
308 	/* l(m) */
309 	put_unaligned_be16(data_len, &b_0[14]);
310 
311 	/* AAD (extra authenticate-only data) / masked 802.11 header
312 	 * FC | A1 | A2 | A3 | SC | [A4] | [QC] */
313 	put_unaligned_be16(len_a, &aad[0]);
314 	put_unaligned(mask_fc, (__le16 *)&aad[2]);
315 	memcpy(&aad[4], &hdr->addr1, 3 * ETH_ALEN);
316 
317 	/* Mask Seq#, leave Frag# */
318 	aad[22] = *((u8 *) &hdr->seq_ctrl) & 0x0f;
319 	aad[23] = 0;
320 
321 	if (a4_included) {
322 		memcpy(&aad[24], hdr->addr4, ETH_ALEN);
323 		aad[30] = qos_tid;
324 		aad[31] = 0;
325 	} else {
326 		memset(&aad[24], 0, ETH_ALEN + IEEE80211_QOS_CTL_LEN);
327 		aad[24] = qos_tid;
328 	}
329 }
330 
331 
332 static inline void ccmp_pn2hdr(u8 *hdr, u8 *pn, int key_id)
333 {
334 	hdr[0] = pn[5];
335 	hdr[1] = pn[4];
336 	hdr[2] = 0;
337 	hdr[3] = 0x20 | (key_id << 6);
338 	hdr[4] = pn[3];
339 	hdr[5] = pn[2];
340 	hdr[6] = pn[1];
341 	hdr[7] = pn[0];
342 }
343 
344 
345 static inline void ccmp_hdr2pn(u8 *pn, u8 *hdr)
346 {
347 	pn[0] = hdr[7];
348 	pn[1] = hdr[6];
349 	pn[2] = hdr[5];
350 	pn[3] = hdr[4];
351 	pn[4] = hdr[1];
352 	pn[5] = hdr[0];
353 }
354 
355 
356 static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
357 {
358 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
359 	struct ieee80211_key *key = tx->key;
360 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
361 	int hdrlen, len, tail;
362 	u8 *pos, *pn;
363 	int i;
364 	bool skip_hw;
365 
366 	skip_hw = (tx->key->conf.flags & IEEE80211_KEY_FLAG_SW_MGMT) &&
367 		ieee80211_is_mgmt(hdr->frame_control);
368 
369 	if ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
370 	    !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) &&
371 	    !skip_hw) {
372 		/* hwaccel - with no need for preallocated room for CCMP
373 		 * header or MIC fields */
374 		info->control.hw_key = &tx->key->conf;
375 		return 0;
376 	}
377 
378 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
379 	len = skb->len - hdrlen;
380 
381 	if (key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)
382 		tail = 0;
383 	else
384 		tail = CCMP_MIC_LEN;
385 
386 	if (WARN_ON(skb_tailroom(skb) < tail ||
387 		    skb_headroom(skb) < CCMP_HDR_LEN))
388 		return -1;
389 
390 	pos = skb_push(skb, CCMP_HDR_LEN);
391 	memmove(pos, pos + CCMP_HDR_LEN, hdrlen);
392 	hdr = (struct ieee80211_hdr *) pos;
393 	pos += hdrlen;
394 
395 	/* PN = PN + 1 */
396 	pn = key->u.ccmp.tx_pn;
397 
398 	for (i = CCMP_PN_LEN - 1; i >= 0; i--) {
399 		pn[i]++;
400 		if (pn[i])
401 			break;
402 	}
403 
404 	ccmp_pn2hdr(pos, pn, key->conf.keyidx);
405 
406 	if ((key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) && !skip_hw) {
407 		/* hwaccel - with preallocated room for CCMP header */
408 		info->control.hw_key = &tx->key->conf;
409 		return 0;
410 	}
411 
412 	pos += CCMP_HDR_LEN;
413 	ccmp_special_blocks(skb, pn, key->u.ccmp.tx_crypto_buf, 0);
414 	ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, key->u.ccmp.tx_crypto_buf, pos, len,
415 				  pos, skb_put(skb, CCMP_MIC_LEN));
416 
417 	return 0;
418 }
419 
420 
421 ieee80211_tx_result
422 ieee80211_crypto_ccmp_encrypt(struct ieee80211_tx_data *tx)
423 {
424 	struct sk_buff *skb = tx->skb;
425 
426 	ieee80211_tx_set_protected(tx);
427 
428 	do {
429 		if (ccmp_encrypt_skb(tx, skb) < 0)
430 			return TX_DROP;
431 	} while ((skb = skb->next));
432 
433 	return TX_CONTINUE;
434 }
435 
436 
437 ieee80211_rx_result
438 ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
439 {
440 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
441 	int hdrlen;
442 	struct ieee80211_key *key = rx->key;
443 	struct sk_buff *skb = rx->skb;
444 	u8 pn[CCMP_PN_LEN];
445 	int data_len;
446 
447 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
448 
449 	if (!ieee80211_is_data(hdr->frame_control) &&
450 	    !ieee80211_is_robust_mgmt_frame(hdr))
451 		return RX_CONTINUE;
452 
453 	data_len = skb->len - hdrlen - CCMP_HDR_LEN - CCMP_MIC_LEN;
454 	if (!rx->sta || data_len < 0)
455 		return RX_DROP_UNUSABLE;
456 
457 	if ((rx->status->flag & RX_FLAG_DECRYPTED) &&
458 	    (rx->status->flag & RX_FLAG_IV_STRIPPED))
459 		return RX_CONTINUE;
460 
461 	ccmp_hdr2pn(pn, skb->data + hdrlen);
462 
463 	if (memcmp(pn, key->u.ccmp.rx_pn[rx->queue], CCMP_PN_LEN) <= 0) {
464 		key->u.ccmp.replays++;
465 		return RX_DROP_UNUSABLE;
466 	}
467 
468 	if (!(rx->status->flag & RX_FLAG_DECRYPTED)) {
469 		/* hardware didn't decrypt/verify MIC */
470 		ccmp_special_blocks(skb, pn, key->u.ccmp.rx_crypto_buf, 1);
471 
472 		if (ieee80211_aes_ccm_decrypt(
473 			    key->u.ccmp.tfm, key->u.ccmp.rx_crypto_buf,
474 			    skb->data + hdrlen + CCMP_HDR_LEN, data_len,
475 			    skb->data + skb->len - CCMP_MIC_LEN,
476 			    skb->data + hdrlen + CCMP_HDR_LEN))
477 			return RX_DROP_UNUSABLE;
478 	}
479 
480 	memcpy(key->u.ccmp.rx_pn[rx->queue], pn, CCMP_PN_LEN);
481 
482 	/* Remove CCMP header and MIC */
483 	skb_trim(skb, skb->len - CCMP_MIC_LEN);
484 	memmove(skb->data + CCMP_HDR_LEN, skb->data, hdrlen);
485 	skb_pull(skb, CCMP_HDR_LEN);
486 
487 	return RX_CONTINUE;
488 }
489 
490 
491 static void bip_aad(struct sk_buff *skb, u8 *aad)
492 {
493 	/* BIP AAD: FC(masked) || A1 || A2 || A3 */
494 
495 	/* FC type/subtype */
496 	aad[0] = skb->data[0];
497 	/* Mask FC Retry, PwrMgt, MoreData flags to zero */
498 	aad[1] = skb->data[1] & ~(BIT(4) | BIT(5) | BIT(6));
499 	/* A1 || A2 || A3 */
500 	memcpy(aad + 2, skb->data + 4, 3 * ETH_ALEN);
501 }
502 
503 
504 static inline void bip_ipn_swap(u8 *d, const u8 *s)
505 {
506 	*d++ = s[5];
507 	*d++ = s[4];
508 	*d++ = s[3];
509 	*d++ = s[2];
510 	*d++ = s[1];
511 	*d = s[0];
512 }
513 
514 
515 ieee80211_tx_result
516 ieee80211_crypto_aes_cmac_encrypt(struct ieee80211_tx_data *tx)
517 {
518 	struct sk_buff *skb = tx->skb;
519 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
520 	struct ieee80211_key *key = tx->key;
521 	struct ieee80211_mmie *mmie;
522 	u8 *pn, aad[20];
523 	int i;
524 
525 	if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) {
526 		/* hwaccel */
527 		info->control.hw_key = &tx->key->conf;
528 		return 0;
529 	}
530 
531 	if (WARN_ON(skb_tailroom(skb) < sizeof(*mmie)))
532 		return TX_DROP;
533 
534 	mmie = (struct ieee80211_mmie *) skb_put(skb, sizeof(*mmie));
535 	mmie->element_id = WLAN_EID_MMIE;
536 	mmie->length = sizeof(*mmie) - 2;
537 	mmie->key_id = cpu_to_le16(key->conf.keyidx);
538 
539 	/* PN = PN + 1 */
540 	pn = key->u.aes_cmac.tx_pn;
541 
542 	for (i = sizeof(key->u.aes_cmac.tx_pn) - 1; i >= 0; i--) {
543 		pn[i]++;
544 		if (pn[i])
545 			break;
546 	}
547 	bip_ipn_swap(mmie->sequence_number, pn);
548 
549 	bip_aad(skb, aad);
550 
551 	/*
552 	 * MIC = AES-128-CMAC(IGTK, AAD || Management Frame Body || MMIE, 64)
553 	 */
554 	ieee80211_aes_cmac(key->u.aes_cmac.tfm, key->u.aes_cmac.tx_crypto_buf,
555 			   aad, skb->data + 24, skb->len - 24, mmie->mic);
556 
557 	return TX_CONTINUE;
558 }
559 
560 
561 ieee80211_rx_result
562 ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
563 {
564 	struct sk_buff *skb = rx->skb;
565 	struct ieee80211_key *key = rx->key;
566 	struct ieee80211_mmie *mmie;
567 	u8 aad[20], mic[8], ipn[6];
568 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
569 
570 	if (!ieee80211_is_mgmt(hdr->frame_control))
571 		return RX_CONTINUE;
572 
573 	if ((rx->status->flag & RX_FLAG_DECRYPTED) &&
574 	    (rx->status->flag & RX_FLAG_IV_STRIPPED))
575 		return RX_CONTINUE;
576 
577 	if (skb->len < 24 + sizeof(*mmie))
578 		return RX_DROP_UNUSABLE;
579 
580 	mmie = (struct ieee80211_mmie *)
581 		(skb->data + skb->len - sizeof(*mmie));
582 	if (mmie->element_id != WLAN_EID_MMIE ||
583 	    mmie->length != sizeof(*mmie) - 2)
584 		return RX_DROP_UNUSABLE; /* Invalid MMIE */
585 
586 	bip_ipn_swap(ipn, mmie->sequence_number);
587 
588 	if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
589 		key->u.aes_cmac.replays++;
590 		return RX_DROP_UNUSABLE;
591 	}
592 
593 	if (!(rx->status->flag & RX_FLAG_DECRYPTED)) {
594 		/* hardware didn't decrypt/verify MIC */
595 		bip_aad(skb, aad);
596 		ieee80211_aes_cmac(key->u.aes_cmac.tfm,
597 				   key->u.aes_cmac.rx_crypto_buf, aad,
598 				   skb->data + 24, skb->len - 24, mic);
599 		if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
600 			key->u.aes_cmac.icverrors++;
601 			return RX_DROP_UNUSABLE;
602 		}
603 	}
604 
605 	memcpy(key->u.aes_cmac.rx_pn, ipn, 6);
606 
607 	/* Remove MMIE */
608 	skb_trim(skb, skb->len - sizeof(*mmie));
609 
610 	return RX_CONTINUE;
611 }
612