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 #include <crypto/aes.h>
  19
  20 #include "ieee80211_i.h"
  21 #include "michael.h"
  22 #include "tkip.h"
  23 #include "aes_ccm.h"
  24 #include "aes_cmac.h"
  25 #include "wpa.h"
  26
  27 ieee80211_tx_result
  28 ieee80211_tx_h_michael_mic_add(struct ieee80211_tx_data *tx)
  29 {
  30         u8 *data, *key, *mic;
  31         size_t data_len;
  32         unsigned int hdrlen;
  33         struct ieee80211_hdr *hdr;
  34         struct sk_buff *skb = tx->skb;
  35         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
  36         int tail;
  37
  38         hdr = (struct ieee80211_hdr *)skb->data;
  39         if (!tx->key || tx->key->conf.cipher != WLAN_CIPHER_SUITE_TKIP ||
  40             skb->len < 24 || !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 (unlikely(info->flags & IEEE80211_TX_INTFL_TKIP_MIC_FAILURE)) {
  51                 /* Need to use software crypto for the test */
  52                 info->control.hw_key = NULL;
  53         }
  54
  55         if (info->control.hw_key &&
  56             !(tx->flags & IEEE80211_TX_FRAGMENTED) &&
  57             !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_MMIC)) {
  58                 /* hwaccel - with no need for SW-generated MMIC */
  59                 return TX_CONTINUE;
  60         }
  61
  62         tail = MICHAEL_MIC_LEN;
  63         if (!info->control.hw_key)
  64                 tail += TKIP_ICV_LEN;
  65
  66         if (WARN_ON(skb_tailroom(skb) < tail ||
  67                     skb_headroom(skb) < TKIP_IV_LEN))
  68                 return TX_DROP;
  69
  70         key = &tx->key->conf.key[NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY];
  71         mic = skb_put(skb, MICHAEL_MIC_LEN);
  72         michael_mic(key, hdr, data, data_len, mic);
  73         if (unlikely(info->flags & IEEE80211_TX_INTFL_TKIP_MIC_FAILURE))
  74                 mic[0]++;
  75
  76         return TX_CONTINUE;
  77 }
  78
  79
  80 ieee80211_rx_result
  81 ieee80211_rx_h_michael_mic_verify(struct ieee80211_rx_data *rx)
  82 {
  83         u8 *data, *key = NULL;
  84         size_t data_len;
  85         unsigned int hdrlen;
  86         u8 mic[MICHAEL_MIC_LEN];
  87         struct sk_buff *skb = rx->skb;
  88         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
  89         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
  90
  91         /*
  92          * it makes no sense to check for MIC errors on anything other
  93          * than data frames.
  94          */
  95         if (!ieee80211_is_data_present(hdr->frame_control))
  96                 return RX_CONTINUE;
  97
  98         /*
  99          * No way to verify the MIC if the hardware stripped it or
 100          * the IV with the key index. In this case we have solely rely
 101          * on the driver to set RX_FLAG_MMIC_ERROR in the event of a
 102          * MIC failure report.
 103          */
 104         if (status->flag & (RX_FLAG_MMIC_STRIPPED | RX_FLAG_IV_STRIPPED)) {
 105                 if (status->flag & RX_FLAG_MMIC_ERROR)
 106                         goto mic_fail;
 107
 108                 if (!(status->flag & RX_FLAG_IV_STRIPPED))
 109                         goto update_iv;
 110
 111                 return RX_CONTINUE;
 112         }
 113
 114         /*
 115          * Some hardware seems to generate Michael MIC failure reports; even
 116          * though, the frame was not encrypted with TKIP and therefore has no
 117          * MIC. Ignore the flag them to avoid triggering countermeasures.
 118          */
 119         if (!rx->key || rx->key->conf.cipher != WLAN_CIPHER_SUITE_TKIP ||
 120             !(status->flag & RX_FLAG_DECRYPTED))
 121                 return RX_CONTINUE;
 122
 123         if (rx->sdata->vif.type == NL80211_IFTYPE_AP && rx->key->conf.keyidx) {
 124                 /*
 125                  * APs with pairwise keys should never receive Michael MIC
 126                  * errors for non-zero keyidx because these are reserved for
 127                  * group keys and only the AP is sending real multicast
 128                  * frames in the BSS. (
 129                  */
 130                 return RX_DROP_UNUSABLE;
 131         }
 132
 133         if (status->flag & RX_FLAG_MMIC_ERROR)
 134                 goto mic_fail;
 135
 136         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 137         if (skb->len < hdrlen + MICHAEL_MIC_LEN)
 138                 return RX_DROP_UNUSABLE;
 139
 140         data = skb->data + hdrlen;
 141         data_len = skb->len - hdrlen - MICHAEL_MIC_LEN;
 142         key = &rx->key->conf.key[NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY];
 143         michael_mic(key, hdr, data, data_len, mic);
 144         if (memcmp(mic, data + data_len, MICHAEL_MIC_LEN) != 0)
 145                 goto mic_fail;
 146
 147         /* remove Michael MIC from payload */
 148         skb_trim(skb, skb->len - MICHAEL_MIC_LEN);
 149
 150 update_iv:
 151         /* update IV in key information to be able to detect replays */
 152         rx->key->u.tkip.rx[rx->security_idx].iv32 = rx->tkip_iv32;
 153         rx->key->u.tkip.rx[rx->security_idx].iv16 = rx->tkip_iv16;
 154
 155         return RX_CONTINUE;
 156
 157 mic_fail:
 158         /*
 159          * In some cases the key can be unset - e.g. a multicast packet, in
 160          * a driver that supports HW encryption. Send up the key idx only if
 161          * the key is set.
 162          */
 163         mac80211_ev_michael_mic_failure(rx->sdata,
 164                                         rx->key ? rx->key->conf.keyidx : -1,
 165                                         (void *) skb->data, NULL, GFP_ATOMIC);
 166         return RX_DROP_UNUSABLE;
 167 }
 168
 169
 170 static int tkip_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 171 {
 172         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 173         struct ieee80211_key *key = tx->key;
 174         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 175         unsigned long flags;
 176         unsigned int hdrlen;
 177         int len, tail;
 178         u8 *pos;
 179
 180         if (info->control.hw_key &&
 181             !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
 182                 /* hwaccel - with no need for software-generated IV */
 183                 return 0;
 184         }
 185
 186         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 187         len = skb->len - hdrlen;
 188
 189         if (info->control.hw_key)
 190                 tail = 0;
 191         else
 192                 tail = TKIP_ICV_LEN;
 193
 194         if (WARN_ON(skb_tailroom(skb) < tail ||
 195                     skb_headroom(skb) < TKIP_IV_LEN))
 196                 return -1;
 197
 198         pos = skb_push(skb, TKIP_IV_LEN);
 199         memmove(pos, pos + TKIP_IV_LEN, hdrlen);
 200         pos += hdrlen;
 201
 202         /* Increase IV for the frame */
 203         spin_lock_irqsave(&key->u.tkip.txlock, flags);
 204         key->u.tkip.tx.iv16++;
 205         if (key->u.tkip.tx.iv16 == 0)
 206                 key->u.tkip.tx.iv32++;
 207         pos = ieee80211_tkip_add_iv(pos, key);
 208         spin_unlock_irqrestore(&key->u.tkip.txlock, flags);
 209
 210         /* hwaccel - with software IV */
 211         if (info->control.hw_key)
 212                 return 0;
 213
 214         /* Add room for ICV */
 215         skb_put(skb, TKIP_ICV_LEN);
 216
 217         return ieee80211_tkip_encrypt_data(tx->local->wep_tx_tfm,
 218                                            key, skb, pos, len);
 219 }
 220
 221
 222 ieee80211_tx_result
 223 ieee80211_crypto_tkip_encrypt(struct ieee80211_tx_data *tx)
 224 {
 225         struct sk_buff *skb = tx->skb;
 226
 227         ieee80211_tx_set_protected(tx);
 228
 229         do {
 230                 if (tkip_encrypt_skb(tx, skb) < 0)
 231                         return TX_DROP;
 232         } while ((skb = skb->next));
 233
 234         return TX_CONTINUE;
 235 }
 236
 237
 238 ieee80211_rx_result
 239 ieee80211_crypto_tkip_decrypt(struct ieee80211_rx_data *rx)
 240 {
 241         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) rx->skb->data;
 242         int hdrlen, res, hwaccel = 0;
 243         struct ieee80211_key *key = rx->key;
 244         struct sk_buff *skb = rx->skb;
 245         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 246
 247         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 248
 249         if (!ieee80211_is_data(hdr->frame_control))
 250                 return RX_CONTINUE;
 251
 252         if (!rx->sta || skb->len - hdrlen < 12)
 253                 return RX_DROP_UNUSABLE;
 254
 255         /*
 256          * Let TKIP code verify IV, but skip decryption.
 257          * In the case where hardware checks the IV as well,
 258          * we don't even get here, see ieee80211_rx_h_decrypt()
 259          */
 260         if (status->flag & RX_FLAG_DECRYPTED)
 261                 hwaccel = 1;
 262
 263         res = ieee80211_tkip_decrypt_data(rx->local->wep_rx_tfm,
 264                                           key, skb->data + hdrlen,
 265                                           skb->len - hdrlen, rx->sta->sta.addr,
 266                                           hdr->addr1, hwaccel, rx->security_idx,
 267                                           &rx->tkip_iv32,
 268                                           &rx->tkip_iv16);
 269         if (res != TKIP_DECRYPT_OK)
 270                 return RX_DROP_UNUSABLE;
 271
 272         /* Trim ICV */
 273         skb_trim(skb, skb->len - TKIP_ICV_LEN);
 274
 275         /* Remove IV */
 276         memmove(skb->data + TKIP_IV_LEN, skb->data, hdrlen);
 277         skb_pull(skb, TKIP_IV_LEN);
 278
 279         return RX_CONTINUE;
 280 }
 281
 282
 283 static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
 284                                 int encrypted)
 285 {
 286         __le16 mask_fc;
 287         int a4_included, mgmt;
 288         u8 qos_tid;
 289         u8 *b_0, *aad;
 290         u16 data_len, len_a;
 291         unsigned int hdrlen;
 292         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 293
 294         memset(scratch, 0, 6 * AES_BLOCK_SIZE);
 295
 296         b_0 = scratch + 3 * AES_BLOCK_SIZE;
 297         aad = scratch + 4 * AES_BLOCK_SIZE;
 298
 299         /*
 300          * Mask FC: zero subtype b4 b5 b6 (if not mgmt)
 301          * Retry, PwrMgt, MoreData; set Protected
 302          */
 303         mgmt = ieee80211_is_mgmt(hdr->frame_control);
 304         mask_fc = hdr->frame_control;
 305         mask_fc &= ~cpu_to_le16(IEEE80211_FCTL_RETRY |
 306                                 IEEE80211_FCTL_PM | IEEE80211_FCTL_MOREDATA);
 307         if (!mgmt)
 308                 mask_fc &= ~cpu_to_le16(0x0070);
 309         mask_fc |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
 310
 311         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 312         len_a = hdrlen - 2;
 313         a4_included = ieee80211_has_a4(hdr->frame_control);
 314
 315         if (ieee80211_is_data_qos(hdr->frame_control))
 316                 qos_tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
 317         else
 318                 qos_tid = 0;
 319
 320         data_len = skb->len - hdrlen - CCMP_HDR_LEN;
 321         if (encrypted)
 322                 data_len -= CCMP_MIC_LEN;
 323
 324         /* First block, b_0 */
 325         b_0[0] = 0x59; /* flags: Adata: 1, M: 011, L: 001 */
 326         /* Nonce: Nonce Flags | A2 | PN
 327          * Nonce Flags: Priority (b0..b3) | Management (b4) | Reserved (b5..b7)
 328          */
 329         b_0[1] = qos_tid | (mgmt << 4);
 330         memcpy(&b_0[2], hdr->addr2, ETH_ALEN);
 331         memcpy(&b_0[8], pn, CCMP_PN_LEN);
 332         /* l(m) */
 333         put_unaligned_be16(data_len, &b_0[14]);
 334
 335         /* AAD (extra authenticate-only data) / masked 802.11 header
 336          * FC | A1 | A2 | A3 | SC | [A4] | [QC] */
 337         put_unaligned_be16(len_a, &aad[0]);
 338         put_unaligned(mask_fc, (__le16 *)&aad[2]);
 339         memcpy(&aad[4], &hdr->addr1, 3 * ETH_ALEN);
 340
 341         /* Mask Seq#, leave Frag# */
 342         aad[22] = *((u8 *) &hdr->seq_ctrl) & 0x0f;
 343         aad[23] = 0;
 344
 345         if (a4_included) {
 346                 memcpy(&aad[24], hdr->addr4, ETH_ALEN);
 347                 aad[30] = qos_tid;
 348                 aad[31] = 0;
 349         } else {
 350                 memset(&aad[24], 0, ETH_ALEN + IEEE80211_QOS_CTL_LEN);
 351                 aad[24] = qos_tid;
 352         }
 353 }
 354
 355
 356 static inline void ccmp_pn2hdr(u8 *hdr, u8 *pn, int key_id)
 357 {
 358         hdr[0] = pn[5];
 359         hdr[1] = pn[4];
 360         hdr[2] = 0;
 361         hdr[3] = 0x20 | (key_id << 6);
 362         hdr[4] = pn[3];
 363         hdr[5] = pn[2];
 364         hdr[6] = pn[1];
 365         hdr[7] = pn[0];
 366 }
 367
 368
 369 static inline void ccmp_hdr2pn(u8 *pn, u8 *hdr)
 370 {
 371         pn[0] = hdr[7];
 372         pn[1] = hdr[6];
 373         pn[2] = hdr[5];
 374         pn[3] = hdr[4];
 375         pn[4] = hdr[1];
 376         pn[5] = hdr[0];
 377 }
 378
 379
 380 static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 381 {
 382         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 383         struct ieee80211_key *key = tx->key;
 384         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 385         int hdrlen, len, tail;
 386         u8 *pos;
 387         u8 pn[6];
 388         u64 pn64;
 389         u8 scratch[6 * AES_BLOCK_SIZE];
 390
 391         if (info->control.hw_key &&
 392             !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
 393                 /*
 394                  * hwaccel has no need for preallocated room for CCMP
 395                  * header or MIC fields
 396                  */
 397                 return 0;
 398         }
 399
 400         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 401         len = skb->len - hdrlen;
 402
 403         if (info->control.hw_key)
 404                 tail = 0;
 405         else
 406                 tail = CCMP_MIC_LEN;
 407
 408         if (WARN_ON(skb_tailroom(skb) < tail ||
 409                     skb_headroom(skb) < CCMP_HDR_LEN))
 410                 return -1;
 411
 412         pos = skb_push(skb, CCMP_HDR_LEN);
 413         memmove(pos, pos + CCMP_HDR_LEN, hdrlen);
 414         hdr = (struct ieee80211_hdr *) pos;
 415         pos += hdrlen;
 416
 417         pn64 = atomic64_inc_return(&key->u.ccmp.tx_pn);
 418
 419         pn[5] = pn64;
 420         pn[4] = pn64 >> 8;
 421         pn[3] = pn64 >> 16;
 422         pn[2] = pn64 >> 24;
 423         pn[1] = pn64 >> 32;
 424         pn[0] = pn64 >> 40;
 425
 426         ccmp_pn2hdr(pos, pn, key->conf.keyidx);
 427
 428         /* hwaccel - with software CCMP header */
 429         if (info->control.hw_key)
 430                 return 0;
 431
 432         pos += CCMP_HDR_LEN;
 433         ccmp_special_blocks(skb, pn, scratch, 0);
 434         ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, scratch, pos, len,
 435                                   pos, skb_put(skb, CCMP_MIC_LEN));
 436
 437         return 0;
 438 }
 439
 440
 441 ieee80211_tx_result
 442 ieee80211_crypto_ccmp_encrypt(struct ieee80211_tx_data *tx)
 443 {
 444         struct sk_buff *skb = tx->skb;
 445
 446         ieee80211_tx_set_protected(tx);
 447
 448         do {
 449                 if (ccmp_encrypt_skb(tx, skb) < 0)
 450                         return TX_DROP;
 451         } while ((skb = skb->next));
 452
 453         return TX_CONTINUE;
 454 }
 455
 456
 457 ieee80211_rx_result
 458 ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
 459 {
 460         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
 461         int hdrlen;
 462         struct ieee80211_key *key = rx->key;
 463         struct sk_buff *skb = rx->skb;
 464         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 465         u8 pn[CCMP_PN_LEN];
 466         int data_len;
 467         int queue;
 468
 469         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 470
 471         if (!ieee80211_is_data(hdr->frame_control) &&
 472             !ieee80211_is_robust_mgmt_frame(hdr))
 473                 return RX_CONTINUE;
 474
 475         data_len = skb->len - hdrlen - CCMP_HDR_LEN - CCMP_MIC_LEN;
 476         if (!rx->sta || data_len < 0)
 477                 return RX_DROP_UNUSABLE;
 478
 479         ccmp_hdr2pn(pn, skb->data + hdrlen);
 480
 481         queue = rx->security_idx;
 482
 483         if (memcmp(pn, key->u.ccmp.rx_pn[queue], CCMP_PN_LEN) <= 0) {
 484                 key->u.ccmp.replays++;
 485                 return RX_DROP_UNUSABLE;
 486         }
 487
 488         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 489                 u8 scratch[6 * AES_BLOCK_SIZE];
 490                 /* hardware didn't decrypt/verify MIC */
 491                 ccmp_special_blocks(skb, pn, scratch, 1);
 492
 493                 if (ieee80211_aes_ccm_decrypt(
 494                             key->u.ccmp.tfm, scratch,
 495                             skb->data + hdrlen + CCMP_HDR_LEN, data_len,
 496                             skb->data + skb->len - CCMP_MIC_LEN,
 497                             skb->data + hdrlen + CCMP_HDR_LEN))
 498                         return RX_DROP_UNUSABLE;
 499         }
 500
 501         memcpy(key->u.ccmp.rx_pn[queue], pn, CCMP_PN_LEN);
 502
 503         /* Remove CCMP header and MIC */
 504         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 505         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdrlen);
 506         skb_pull(skb, CCMP_HDR_LEN);
 507
 508         return RX_CONTINUE;
 509 }
 510
 511
 512 static void bip_aad(struct sk_buff *skb, u8 *aad)
 513 {
 514         /* BIP AAD: FC(masked) || A1 || A2 || A3 */
 515
 516         /* FC type/subtype */
 517         aad[0] = skb->data[0];
 518         /* Mask FC Retry, PwrMgt, MoreData flags to zero */
 519         aad[1] = skb->data[1] & ~(BIT(4) | BIT(5) | BIT(6));
 520         /* A1 || A2 || A3 */
 521         memcpy(aad + 2, skb->data + 4, 3 * ETH_ALEN);
 522 }
 523
 524
 525 static inline void bip_ipn_set64(u8 *d, u64 pn)
 526 {
 527         *d++ = pn;
 528         *d++ = pn >> 8;
 529         *d++ = pn >> 16;
 530         *d++ = pn >> 24;
 531         *d++ = pn >> 32;
 532         *d = pn >> 40;
 533 }
 534
 535 static inline void bip_ipn_swap(u8 *d, const u8 *s)
 536 {
 537         *d++ = s[5];
 538         *d++ = s[4];
 539         *d++ = s[3];
 540         *d++ = s[2];
 541         *d++ = s[1];
 542         *d = s[0];
 543 }
 544
 545
 546 ieee80211_tx_result
 547 ieee80211_crypto_aes_cmac_encrypt(struct ieee80211_tx_data *tx)
 548 {
 549         struct sk_buff *skb = tx->skb;
 550         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 551         struct ieee80211_key *key = tx->key;
 552         struct ieee80211_mmie *mmie;
 553         u8 aad[20];
 554         u64 pn64;
 555
 556         if (info->control.hw_key)
 557                 return 0;
 558
 559         if (WARN_ON(skb_tailroom(skb) < sizeof(*mmie)))
 560                 return TX_DROP;
 561
 562         mmie = (struct ieee80211_mmie *) skb_put(skb, sizeof(*mmie));
 563         mmie->element_id = WLAN_EID_MMIE;
 564         mmie->length = sizeof(*mmie) - 2;
 565         mmie->key_id = cpu_to_le16(key->conf.keyidx);
 566
 567         /* PN = PN + 1 */
 568         pn64 = atomic64_inc_return(&key->u.aes_cmac.tx_pn);
 569
 570         bip_ipn_set64(mmie->sequence_number, pn64);
 571
 572         bip_aad(skb, aad);
 573
 574         /*
 575          * MIC = AES-128-CMAC(IGTK, AAD || Management Frame Body || MMIE, 64)
 576          */
 577         ieee80211_aes_cmac(key->u.aes_cmac.tfm, aad,
 578                            skb->data + 24, skb->len - 24, mmie->mic);
 579
 580         return TX_CONTINUE;
 581 }
 582
 583
 584 ieee80211_rx_result
 585 ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
 586 {
 587         struct sk_buff *skb = rx->skb;
 588         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 589         struct ieee80211_key *key = rx->key;
 590         struct ieee80211_mmie *mmie;
 591         u8 aad[20], mic[8], ipn[6];
 592         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 593
 594         if (!ieee80211_is_mgmt(hdr->frame_control))
 595                 return RX_CONTINUE;
 596
 597         if (skb->len < 24 + sizeof(*mmie))
 598                 return RX_DROP_UNUSABLE;
 599
 600         mmie = (struct ieee80211_mmie *)
 601                 (skb->data + skb->len - sizeof(*mmie));
 602         if (mmie->element_id != WLAN_EID_MMIE ||
 603             mmie->length != sizeof(*mmie) - 2)
 604                 return RX_DROP_UNUSABLE; /* Invalid MMIE */
 605
 606         bip_ipn_swap(ipn, mmie->sequence_number);
 607
 608         if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
 609                 key->u.aes_cmac.replays++;
 610                 return RX_DROP_UNUSABLE;
 611         }
 612
 613         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 614                 /* hardware didn't decrypt/verify MIC */
 615                 bip_aad(skb, aad);
 616                 ieee80211_aes_cmac(key->u.aes_cmac.tfm, aad,
 617                                    skb->data + 24, skb->len - 24, mic);
 618                 if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
 619                         key->u.aes_cmac.icverrors++;
 620                         return RX_DROP_UNUSABLE;
 621                 }
 622         }
 623
 624         memcpy(key->u.aes_cmac.rx_pn, ipn, 6);
 625
 626         /* Remove MMIE */
 627         skb_trim(skb, skb->len - sizeof(*mmie));
 628
 629         return RX_CONTINUE;
 630 }