net/mac80211/wpa.c

   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         int queue;
 440
 441         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 442
 443         if (!ieee80211_is_data(hdr->frame_control) &&
 444             !ieee80211_is_robust_mgmt_frame(hdr))
 445                 return RX_CONTINUE;
 446
 447         data_len = skb->len - hdrlen - CCMP_HDR_LEN - CCMP_MIC_LEN;
 448         if (!rx->sta || data_len < 0)
 449                 return RX_DROP_UNUSABLE;
 450
 451         if ((status->flag & RX_FLAG_DECRYPTED) &&
 452             (status->flag & RX_FLAG_IV_STRIPPED))
 453                 return RX_CONTINUE;
 454
 455         ccmp_hdr2pn(pn, skb->data + hdrlen);
 456
 457         queue = ieee80211_is_mgmt(hdr->frame_control) ?
 458                 NUM_RX_DATA_QUEUES : rx->queue;
 459
 460         if (memcmp(pn, key->u.ccmp.rx_pn[queue], CCMP_PN_LEN) <= 0) {
 461                 key->u.ccmp.replays++;
 462                 return RX_DROP_UNUSABLE;
 463         }
 464
 465         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 466                 /* hardware didn't decrypt/verify MIC */
 467                 ccmp_special_blocks(skb, pn, key->u.ccmp.rx_crypto_buf, 1);
 468
 469                 if (ieee80211_aes_ccm_decrypt(
 470                             key->u.ccmp.tfm, key->u.ccmp.rx_crypto_buf,
 471                             skb->data + hdrlen + CCMP_HDR_LEN, data_len,
 472                             skb->data + skb->len - CCMP_MIC_LEN,
 473                             skb->data + hdrlen + CCMP_HDR_LEN))
 474                         return RX_DROP_UNUSABLE;
 475         }
 476
 477         memcpy(key->u.ccmp.rx_pn[queue], pn, CCMP_PN_LEN);
 478
 479         /* Remove CCMP header and MIC */
 480         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 481         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdrlen);
 482         skb_pull(skb, CCMP_HDR_LEN);
 483
 484         return RX_CONTINUE;
 485 }
 486
 487
 488 static void bip_aad(struct sk_buff *skb, u8 *aad)
 489 {
 490         /* BIP AAD: FC(masked) || A1 || A2 || A3 */
 491
 492         /* FC type/subtype */
 493         aad[0] = skb->data[0];
 494         /* Mask FC Retry, PwrMgt, MoreData flags to zero */
 495         aad[1] = skb->data[1] & ~(BIT(4) | BIT(5) | BIT(6));
 496         /* A1 || A2 || A3 */
 497         memcpy(aad + 2, skb->data + 4, 3 * ETH_ALEN);
 498 }
 499
 500
 501 static inline void bip_ipn_swap(u8 *d, const u8 *s)
 502 {
 503         *d++ = s[5];
 504         *d++ = s[4];
 505         *d++ = s[3];
 506         *d++ = s[2];
 507         *d++ = s[1];
 508         *d = s[0];
 509 }
 510
 511
 512 ieee80211_tx_result
 513 ieee80211_crypto_aes_cmac_encrypt(struct ieee80211_tx_data *tx)
 514 {
 515         struct sk_buff *skb = tx->skb;
 516         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 517         struct ieee80211_key *key = tx->key;
 518         struct ieee80211_mmie *mmie;
 519         u8 *pn, aad[20];
 520         int i;
 521
 522         if (info->control.hw_key)
 523                 return 0;
 524
 525         if (WARN_ON(skb_tailroom(skb) < sizeof(*mmie)))
 526                 return TX_DROP;
 527
 528         mmie = (struct ieee80211_mmie *) skb_put(skb, sizeof(*mmie));
 529         mmie->element_id = WLAN_EID_MMIE;
 530         mmie->length = sizeof(*mmie) - 2;
 531         mmie->key_id = cpu_to_le16(key->conf.keyidx);
 532
 533         /* PN = PN + 1 */
 534         pn = key->u.aes_cmac.tx_pn;
 535
 536         for (i = sizeof(key->u.aes_cmac.tx_pn) - 1; i >= 0; i--) {
 537                 pn[i]++;
 538                 if (pn[i])
 539                         break;
 540         }
 541         bip_ipn_swap(mmie->sequence_number, pn);
 542
 543         bip_aad(skb, aad);
 544
 545         /*
 546          * MIC = AES-128-CMAC(IGTK, AAD || Management Frame Body || MMIE, 64)
 547          */
 548         ieee80211_aes_cmac(key->u.aes_cmac.tfm, key->u.aes_cmac.tx_crypto_buf,
 549                            aad, skb->data + 24, skb->len - 24, mmie->mic);
 550
 551         return TX_CONTINUE;
 552 }
 553
 554
 555 ieee80211_rx_result
 556 ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
 557 {
 558         struct sk_buff *skb = rx->skb;
 559         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 560         struct ieee80211_key *key = rx->key;
 561         struct ieee80211_mmie *mmie;
 562         u8 aad[20], mic[8], ipn[6];
 563         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 564
 565         if (!ieee80211_is_mgmt(hdr->frame_control))
 566                 return RX_CONTINUE;
 567
 568         if ((status->flag & RX_FLAG_DECRYPTED) &&
 569             (status->flag & RX_FLAG_IV_STRIPPED))
 570                 return RX_CONTINUE;
 571
 572         if (skb->len < 24 + sizeof(*mmie))
 573                 return RX_DROP_UNUSABLE;
 574
 575         mmie = (struct ieee80211_mmie *)
 576                 (skb->data + skb->len - sizeof(*mmie));
 577         if (mmie->element_id != WLAN_EID_MMIE ||
 578             mmie->length != sizeof(*mmie) - 2)
 579                 return RX_DROP_UNUSABLE; /* Invalid MMIE */
 580
 581         bip_ipn_swap(ipn, mmie->sequence_number);
 582
 583         if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
 584                 key->u.aes_cmac.replays++;
 585                 return RX_DROP_UNUSABLE;
 586         }
 587
 588         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 589                 /* hardware didn't decrypt/verify MIC */
 590                 bip_aad(skb, aad);
 591                 ieee80211_aes_cmac(key->u.aes_cmac.tfm,
 592                                    key->u.aes_cmac.rx_crypto_buf, aad,
 593                                    skb->data + 24, skb->len - 24, mic);
 594                 if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
 595                         key->u.aes_cmac.icverrors++;
 596                         return RX_DROP_UNUSABLE;
 597                 }
 598         }
 599
 600         memcpy(key->u.aes_cmac.rx_pn, ipn, 6);
 601
 602         /* Remove MMIE */
 603         skb_trim(skb, skb->len - sizeof(*mmie));
 604
 605         return RX_CONTINUE;
 606 }