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             (info->flags & IEEE80211_TX_CTL_DONTFRAG ||
  57              tx->local->ops->set_frag_threshold) &&
  58             !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_MMIC)) {
  59                 /* hwaccel - with no need for SW-generated MMIC */
  60                 return TX_CONTINUE;
  61         }
  62
  63         tail = MICHAEL_MIC_LEN;
  64         if (!info->control.hw_key)
  65                 tail += TKIP_ICV_LEN;
  66
  67         if (WARN_ON(skb_tailroom(skb) < tail ||
  68                     skb_headroom(skb) < TKIP_IV_LEN))
  69                 return TX_DROP;
  70
  71         key = &tx->key->conf.key[NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY];
  72         mic = skb_put(skb, MICHAEL_MIC_LEN);
  73         michael_mic(key, hdr, data, data_len, mic);
  74         if (unlikely(info->flags & IEEE80211_TX_INTFL_TKIP_MIC_FAILURE))
  75                 mic[0]++;
  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;
  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
  92         /*
  93          * it makes no sense to check for MIC errors on anything other
  94          * than data frames.
  95          */
  96         if (!ieee80211_is_data_present(hdr->frame_control))
  97                 return RX_CONTINUE;
  98
  99         /*
 100          * No way to verify the MIC if the hardware stripped it or
 101          * the IV with the key index. In this case we have solely rely
 102          * on the driver to set RX_FLAG_MMIC_ERROR in the event of a
 103          * MIC failure report.
 104          */
 105         if (status->flag & (RX_FLAG_MMIC_STRIPPED | RX_FLAG_IV_STRIPPED)) {
 106                 if (status->flag & RX_FLAG_MMIC_ERROR)
 107                         goto mic_fail;
 108
 109                 if (!(status->flag & RX_FLAG_IV_STRIPPED) && rx->key)
 110                         goto update_iv;
 111
 112                 return RX_CONTINUE;
 113         }
 114
 115         /*
 116          * Some hardware seems to generate Michael MIC failure reports; even
 117          * though, the frame was not encrypted with TKIP and therefore has no
 118          * MIC. Ignore the flag them to avoid triggering countermeasures.
 119          */
 120         if (!rx->key || rx->key->conf.cipher != WLAN_CIPHER_SUITE_TKIP ||
 121             !(status->flag & RX_FLAG_DECRYPTED))
 122                 return RX_CONTINUE;
 123
 124         if (rx->sdata->vif.type == NL80211_IFTYPE_AP && rx->key->conf.keyidx) {
 125                 /*
 126                  * APs with pairwise keys should never receive Michael MIC
 127                  * errors for non-zero keyidx because these are reserved for
 128                  * group keys and only the AP is sending real multicast
 129                  * frames in the BSS. (
 130                  */
 131                 return RX_DROP_UNUSABLE;
 132         }
 133
 134         if (status->flag & RX_FLAG_MMIC_ERROR)
 135                 goto mic_fail;
 136
 137         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 138         if (skb->len < hdrlen + MICHAEL_MIC_LEN)
 139                 return RX_DROP_UNUSABLE;
 140
 141         data = skb->data + hdrlen;
 142         data_len = skb->len - hdrlen - MICHAEL_MIC_LEN;
 143         key = &rx->key->conf.key[NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY];
 144         michael_mic(key, hdr, data, data_len, mic);
 145         if (memcmp(mic, data + data_len, MICHAEL_MIC_LEN) != 0)
 146                 goto mic_fail;
 147
 148         /* remove Michael MIC from payload */
 149         skb_trim(skb, skb->len - MICHAEL_MIC_LEN);
 150
 151 update_iv:
 152         /* update IV in key information to be able to detect replays */
 153         rx->key->u.tkip.rx[rx->security_idx].iv32 = rx->tkip_iv32;
 154         rx->key->u.tkip.rx[rx->security_idx].iv16 = rx->tkip_iv16;
 155
 156         return RX_CONTINUE;
 157
 158 mic_fail:
 159         /*
 160          * In some cases the key can be unset - e.g. a multicast packet, in
 161          * a driver that supports HW encryption. Send up the key idx only if
 162          * the key is set.
 163          */
 164         mac80211_ev_michael_mic_failure(rx->sdata,
 165                                         rx->key ? rx->key->conf.keyidx : -1,
 166                                         (void *) skb->data, NULL, GFP_ATOMIC);
 167         return RX_DROP_UNUSABLE;
 168 }
 169
 170
 171 static int tkip_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 172 {
 173         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 174         struct ieee80211_key *key = tx->key;
 175         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 176         unsigned long flags;
 177         unsigned int hdrlen;
 178         int len, tail;
 179         u8 *pos;
 180
 181         if (info->control.hw_key &&
 182             !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
 183                 /* hwaccel - with no need for software-generated IV */
 184                 return 0;
 185         }
 186
 187         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 188         len = skb->len - hdrlen;
 189
 190         if (info->control.hw_key)
 191                 tail = 0;
 192         else
 193                 tail = TKIP_ICV_LEN;
 194
 195         if (WARN_ON(skb_tailroom(skb) < tail ||
 196                     skb_headroom(skb) < TKIP_IV_LEN))
 197                 return -1;
 198
 199         pos = skb_push(skb, TKIP_IV_LEN);
 200         memmove(pos, pos + TKIP_IV_LEN, hdrlen);
 201         pos += hdrlen;
 202
 203         /* Increase IV for the frame */
 204         spin_lock_irqsave(&key->u.tkip.txlock, flags);
 205         key->u.tkip.tx.iv16++;
 206         if (key->u.tkip.tx.iv16 == 0)
 207                 key->u.tkip.tx.iv32++;
 208         pos = ieee80211_tkip_add_iv(pos, key);
 209         spin_unlock_irqrestore(&key->u.tkip.txlock, flags);
 210
 211         /* hwaccel - with software IV */
 212         if (info->control.hw_key)
 213                 return 0;
 214
 215         /* Add room for ICV */
 216         skb_put(skb, TKIP_ICV_LEN);
 217
 218         return ieee80211_tkip_encrypt_data(tx->local->wep_tx_tfm,
 219                                            key, skb, pos, len);
 220 }
 221
 222
 223 ieee80211_tx_result
 224 ieee80211_crypto_tkip_encrypt(struct ieee80211_tx_data *tx)
 225 {
 226         struct sk_buff *skb = tx->skb;
 227
 228         ieee80211_tx_set_protected(tx);
 229
 230         do {
 231                 if (tkip_encrypt_skb(tx, skb) < 0)
 232                         return TX_DROP;
 233         } while ((skb = skb->next));
 234
 235         return TX_CONTINUE;
 236 }
 237
 238
 239 ieee80211_rx_result
 240 ieee80211_crypto_tkip_decrypt(struct ieee80211_rx_data *rx)
 241 {
 242         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) rx->skb->data;
 243         int hdrlen, res, hwaccel = 0;
 244         struct ieee80211_key *key = rx->key;
 245         struct sk_buff *skb = rx->skb;
 246         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 247
 248         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 249
 250         if (!ieee80211_is_data(hdr->frame_control))
 251                 return RX_CONTINUE;
 252
 253         if (!rx->sta || skb->len - hdrlen < 12)
 254                 return RX_DROP_UNUSABLE;
 255
 256         /*
 257          * Let TKIP code verify IV, but skip decryption.
 258          * In the case where hardware checks the IV as well,
 259          * we don't even get here, see ieee80211_rx_h_decrypt()
 260          */
 261         if (status->flag & RX_FLAG_DECRYPTED)
 262                 hwaccel = 1;
 263
 264         res = ieee80211_tkip_decrypt_data(rx->local->wep_rx_tfm,
 265                                           key, skb->data + hdrlen,
 266                                           skb->len - hdrlen, rx->sta->sta.addr,
 267                                           hdr->addr1, hwaccel, rx->security_idx,
 268                                           &rx->tkip_iv32,
 269                                           &rx->tkip_iv16);
 270         if (res != TKIP_DECRYPT_OK)
 271                 return RX_DROP_UNUSABLE;
 272
 273         /* Trim ICV */
 274         skb_trim(skb, skb->len - TKIP_ICV_LEN);
 275
 276         /* Remove IV */
 277         memmove(skb->data + TKIP_IV_LEN, skb->data, hdrlen);
 278         skb_pull(skb, TKIP_IV_LEN);
 279
 280         return RX_CONTINUE;
 281 }
 282
 283
 284 static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
 285                                 int encrypted)
 286 {
 287         __le16 mask_fc;
 288         int a4_included, mgmt;
 289         u8 qos_tid;
 290         u8 *b_0, *aad;
 291         u16 data_len, len_a;
 292         unsigned int hdrlen;
 293         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 294
 295         memset(scratch, 0, 6 * AES_BLOCK_SIZE);
 296
 297         b_0 = scratch + 3 * AES_BLOCK_SIZE;
 298         aad = scratch + 4 * AES_BLOCK_SIZE;
 299
 300         /*
 301          * Mask FC: zero subtype b4 b5 b6 (if not mgmt)
 302          * Retry, PwrMgt, MoreData; set Protected
 303          */
 304         mgmt = ieee80211_is_mgmt(hdr->frame_control);
 305         mask_fc = hdr->frame_control;
 306         mask_fc &= ~cpu_to_le16(IEEE80211_FCTL_RETRY |
 307                                 IEEE80211_FCTL_PM | IEEE80211_FCTL_MOREDATA);
 308         if (!mgmt)
 309                 mask_fc &= ~cpu_to_le16(0x0070);
 310         mask_fc |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
 311
 312         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 313         len_a = hdrlen - 2;
 314         a4_included = ieee80211_has_a4(hdr->frame_control);
 315
 316         if (ieee80211_is_data_qos(hdr->frame_control))
 317                 qos_tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
 318         else
 319                 qos_tid = 0;
 320
 321         data_len = skb->len - hdrlen - CCMP_HDR_LEN;
 322         if (encrypted)
 323                 data_len -= CCMP_MIC_LEN;
 324
 325         /* First block, b_0 */
 326         b_0[0] = 0x59; /* flags: Adata: 1, M: 011, L: 001 */
 327         /* Nonce: Nonce Flags | A2 | PN
 328          * Nonce Flags: Priority (b0..b3) | Management (b4) | Reserved (b5..b7)
 329          */
 330         b_0[1] = qos_tid | (mgmt << 4);
 331         memcpy(&b_0[2], hdr->addr2, ETH_ALEN);
 332         memcpy(&b_0[8], pn, CCMP_PN_LEN);
 333         /* l(m) */
 334         put_unaligned_be16(data_len, &b_0[14]);
 335
 336         /* AAD (extra authenticate-only data) / masked 802.11 header
 337          * FC | A1 | A2 | A3 | SC | [A4] | [QC] */
 338         put_unaligned_be16(len_a, &aad[0]);
 339         put_unaligned(mask_fc, (__le16 *)&aad[2]);
 340         memcpy(&aad[4], &hdr->addr1, 3 * ETH_ALEN);
 341
 342         /* Mask Seq#, leave Frag# */
 343         aad[22] = *((u8 *) &hdr->seq_ctrl) & 0x0f;
 344         aad[23] = 0;
 345
 346         if (a4_included) {
 347                 memcpy(&aad[24], hdr->addr4, ETH_ALEN);
 348                 aad[30] = qos_tid;
 349                 aad[31] = 0;
 350         } else {
 351                 memset(&aad[24], 0, ETH_ALEN + IEEE80211_QOS_CTL_LEN);
 352                 aad[24] = qos_tid;
 353         }
 354 }
 355
 356
 357 static inline void ccmp_pn2hdr(u8 *hdr, u8 *pn, int key_id)
 358 {
 359         hdr[0] = pn[5];
 360         hdr[1] = pn[4];
 361         hdr[2] = 0;
 362         hdr[3] = 0x20 | (key_id << 6);
 363         hdr[4] = pn[3];
 364         hdr[5] = pn[2];
 365         hdr[6] = pn[1];
 366         hdr[7] = pn[0];
 367 }
 368
 369
 370 static inline void ccmp_hdr2pn(u8 *pn, u8 *hdr)
 371 {
 372         pn[0] = hdr[7];
 373         pn[1] = hdr[6];
 374         pn[2] = hdr[5];
 375         pn[3] = hdr[4];
 376         pn[4] = hdr[1];
 377         pn[5] = hdr[0];
 378 }
 379
 380
 381 static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 382 {
 383         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 384         struct ieee80211_key *key = tx->key;
 385         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 386         int hdrlen, len, tail;
 387         u8 *pos;
 388         u8 pn[6];
 389         u64 pn64;
 390         u8 scratch[6 * AES_BLOCK_SIZE];
 391
 392         if (info->control.hw_key &&
 393             !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
 394                 /*
 395                  * hwaccel has no need for preallocated room for CCMP
 396                  * header or MIC fields
 397                  */
 398                 return 0;
 399         }
 400
 401         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 402         len = skb->len - hdrlen;
 403
 404         if (info->control.hw_key)
 405                 tail = 0;
 406         else
 407                 tail = CCMP_MIC_LEN;
 408
 409         if (WARN_ON(skb_tailroom(skb) < tail ||
 410                     skb_headroom(skb) < CCMP_HDR_LEN))
 411                 return -1;
 412
 413         pos = skb_push(skb, CCMP_HDR_LEN);
 414         memmove(pos, pos + CCMP_HDR_LEN, hdrlen);
 415         hdr = (struct ieee80211_hdr *) pos;
 416         pos += hdrlen;
 417
 418         pn64 = atomic64_inc_return(&key->u.ccmp.tx_pn);
 419
 420         pn[5] = pn64;
 421         pn[4] = pn64 >> 8;
 422         pn[3] = pn64 >> 16;
 423         pn[2] = pn64 >> 24;
 424         pn[1] = pn64 >> 32;
 425         pn[0] = pn64 >> 40;
 426
 427         ccmp_pn2hdr(pos, pn, key->conf.keyidx);
 428
 429         /* hwaccel - with software CCMP header */
 430         if (info->control.hw_key)
 431                 return 0;
 432
 433         pos += CCMP_HDR_LEN;
 434         ccmp_special_blocks(skb, pn, scratch, 0);
 435         ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, scratch, pos, len,
 436                                   pos, skb_put(skb, CCMP_MIC_LEN));
 437
 438         return 0;
 439 }
 440
 441
 442 ieee80211_tx_result
 443 ieee80211_crypto_ccmp_encrypt(struct ieee80211_tx_data *tx)
 444 {
 445         struct sk_buff *skb = tx->skb;
 446
 447         ieee80211_tx_set_protected(tx);
 448
 449         do {
 450                 if (ccmp_encrypt_skb(tx, skb) < 0)
 451                         return TX_DROP;
 452         } while ((skb = skb->next));
 453
 454         return TX_CONTINUE;
 455 }
 456
 457
 458 ieee80211_rx_result
 459 ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
 460 {
 461         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
 462         int hdrlen;
 463         struct ieee80211_key *key = rx->key;
 464         struct sk_buff *skb = rx->skb;
 465         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 466         u8 pn[CCMP_PN_LEN];
 467         int data_len;
 468         int queue;
 469
 470         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 471
 472         if (!ieee80211_is_data(hdr->frame_control) &&
 473             !ieee80211_is_robust_mgmt_frame(hdr))
 474                 return RX_CONTINUE;
 475
 476         data_len = skb->len - hdrlen - CCMP_HDR_LEN - CCMP_MIC_LEN;
 477         if (!rx->sta || data_len < 0)
 478                 return RX_DROP_UNUSABLE;
 479
 480         ccmp_hdr2pn(pn, skb->data + hdrlen);
 481
 482         queue = rx->security_idx;
 483
 484         if (memcmp(pn, key->u.ccmp.rx_pn[queue], CCMP_PN_LEN) <= 0) {
 485                 key->u.ccmp.replays++;
 486                 return RX_DROP_UNUSABLE;
 487         }
 488
 489         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 490                 u8 scratch[6 * AES_BLOCK_SIZE];
 491                 /* hardware didn't decrypt/verify MIC */
 492                 ccmp_special_blocks(skb, pn, scratch, 1);
 493
 494                 if (ieee80211_aes_ccm_decrypt(
 495                             key->u.ccmp.tfm, scratch,
 496                             skb->data + hdrlen + CCMP_HDR_LEN, data_len,
 497                             skb->data + skb->len - CCMP_MIC_LEN,
 498                             skb->data + hdrlen + CCMP_HDR_LEN))
 499                         return RX_DROP_UNUSABLE;
 500         }
 501
 502         memcpy(key->u.ccmp.rx_pn[queue], pn, CCMP_PN_LEN);
 503
 504         /* Remove CCMP header and MIC */
 505         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 506         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdrlen);
 507         skb_pull(skb, CCMP_HDR_LEN);
 508
 509         return RX_CONTINUE;
 510 }
 511
 512
 513 static void bip_aad(struct sk_buff *skb, u8 *aad)
 514 {
 515         /* BIP AAD: FC(masked) || A1 || A2 || A3 */
 516
 517         /* FC type/subtype */
 518         aad[0] = skb->data[0];
 519         /* Mask FC Retry, PwrMgt, MoreData flags to zero */
 520         aad[1] = skb->data[1] & ~(BIT(4) | BIT(5) | BIT(6));
 521         /* A1 || A2 || A3 */
 522         memcpy(aad + 2, skb->data + 4, 3 * ETH_ALEN);
 523 }
 524
 525
 526 static inline void bip_ipn_set64(u8 *d, u64 pn)
 527 {
 528         *d++ = pn;
 529         *d++ = pn >> 8;
 530         *d++ = pn >> 16;
 531         *d++ = pn >> 24;
 532         *d++ = pn >> 32;
 533         *d = pn >> 40;
 534 }
 535
 536 static inline void bip_ipn_swap(u8 *d, const u8 *s)
 537 {
 538         *d++ = s[5];
 539         *d++ = s[4];
 540         *d++ = s[3];
 541         *d++ = s[2];
 542         *d++ = s[1];
 543         *d = s[0];
 544 }
 545
 546
 547 ieee80211_tx_result
 548 ieee80211_crypto_aes_cmac_encrypt(struct ieee80211_tx_data *tx)
 549 {
 550         struct sk_buff *skb = tx->skb;
 551         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 552         struct ieee80211_key *key = tx->key;
 553         struct ieee80211_mmie *mmie;
 554         u8 aad[20];
 555         u64 pn64;
 556
 557         if (info->control.hw_key)
 558                 return 0;
 559
 560         if (WARN_ON(skb_tailroom(skb) < sizeof(*mmie)))
 561                 return TX_DROP;
 562
 563         mmie = (struct ieee80211_mmie *) skb_put(skb, sizeof(*mmie));
 564         mmie->element_id = WLAN_EID_MMIE;
 565         mmie->length = sizeof(*mmie) - 2;
 566         mmie->key_id = cpu_to_le16(key->conf.keyidx);
 567
 568         /* PN = PN + 1 */
 569         pn64 = atomic64_inc_return(&key->u.aes_cmac.tx_pn);
 570
 571         bip_ipn_set64(mmie->sequence_number, pn64);
 572
 573         bip_aad(skb, aad);
 574
 575         /*
 576          * MIC = AES-128-CMAC(IGTK, AAD || Management Frame Body || MMIE, 64)
 577          */
 578         ieee80211_aes_cmac(key->u.aes_cmac.tfm, aad,
 579                            skb->data + 24, skb->len - 24, mmie->mic);
 580
 581         return TX_CONTINUE;
 582 }
 583
 584
 585 ieee80211_rx_result
 586 ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
 587 {
 588         struct sk_buff *skb = rx->skb;
 589         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 590         struct ieee80211_key *key = rx->key;
 591         struct ieee80211_mmie *mmie;
 592         u8 aad[20], mic[8], ipn[6];
 593         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 594
 595         if (!ieee80211_is_mgmt(hdr->frame_control))
 596                 return RX_CONTINUE;
 597
 598         if (skb->len < 24 + sizeof(*mmie))
 599                 return RX_DROP_UNUSABLE;
 600
 601         mmie = (struct ieee80211_mmie *)
 602                 (skb->data + skb->len - sizeof(*mmie));
 603         if (mmie->element_id != WLAN_EID_MMIE ||
 604             mmie->length != sizeof(*mmie) - 2)
 605                 return RX_DROP_UNUSABLE; /* Invalid MMIE */
 606
 607         bip_ipn_swap(ipn, mmie->sequence_number);
 608
 609         if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
 610                 key->u.aes_cmac.replays++;
 611                 return RX_DROP_UNUSABLE;
 612         }
 613
 614         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 615                 /* hardware didn't decrypt/verify MIC */
 616                 bip_aad(skb, aad);
 617                 ieee80211_aes_cmac(key->u.aes_cmac.tfm, aad,
 618                                    skb->data + 24, skb->len - 24, mic);
 619                 if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
 620                         key->u.aes_cmac.icverrors++;
 621                         return RX_DROP_UNUSABLE;
 622                 }
 623         }
 624
 625         memcpy(key->u.aes_cmac.rx_pn, ipn, 6);
 626
 627         /* Remove MMIE */
 628         skb_trim(skb, skb->len - sizeof(*mmie));
 629
 630         return RX_CONTINUE;
 631 }