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/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, NULL);
 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 }