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         u8 mic[MICHAEL_MIC_LEN];
  89         struct sk_buff *skb = rx->skb;
  90         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
  91         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
  92         int authenticator = 1, wpa_test = 0;
  93
  94         /* No way to verify the MIC if the hardware stripped it */
  95         if (status->flag & RX_FLAG_MMIC_STRIPPED)
  96                 return RX_CONTINUE;
  97
  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                                                 GFP_ATOMIC);
 127                 return RX_DROP_UNUSABLE;
 128         }
 129
 130         /* remove Michael MIC from payload */
 131         skb_trim(skb, skb->len - MICHAEL_MIC_LEN);
 132
 133         /* update IV in key information to be able to detect replays */
 134         rx->key->u.tkip.rx[rx->queue].iv32 = rx->tkip_iv32;
 135         rx->key->u.tkip.rx[rx->queue].iv16 = rx->tkip_iv16;
 136
 137         return RX_CONTINUE;
 138 }
 139
 140
 141 static int tkip_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 142 {
 143         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 144         struct ieee80211_key *key = tx->key;
 145         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 146         unsigned int hdrlen;
 147         int len, tail;
 148         u8 *pos;
 149
 150         if ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
 151             !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
 152                 /* hwaccel - with no need for preallocated room for IV/ICV */
 153                 info->control.hw_key = &tx->key->conf;
 154                 return 0;
 155         }
 156
 157         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 158         len = skb->len - hdrlen;
 159
 160         if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)
 161                 tail = 0;
 162         else
 163                 tail = TKIP_ICV_LEN;
 164
 165         if (WARN_ON(skb_tailroom(skb) < tail ||
 166                     skb_headroom(skb) < TKIP_IV_LEN))
 167                 return -1;
 168
 169         pos = skb_push(skb, TKIP_IV_LEN);
 170         memmove(pos, pos + TKIP_IV_LEN, hdrlen);
 171         pos += hdrlen;
 172
 173         /* Increase IV for the frame */
 174         key->u.tkip.tx.iv16++;
 175         if (key->u.tkip.tx.iv16 == 0)
 176                 key->u.tkip.tx.iv32++;
 177
 178         if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) {
 179                 /* hwaccel - with preallocated room for IV */
 180                 ieee80211_tkip_add_iv(pos, key, key->u.tkip.tx.iv16);
 181
 182                 info->control.hw_key = &tx->key->conf;
 183                 return 0;
 184         }
 185
 186         /* Add room for ICV */
 187         skb_put(skb, TKIP_ICV_LEN);
 188
 189         hdr = (struct ieee80211_hdr *) skb->data;
 190         ieee80211_tkip_encrypt_data(tx->local->wep_tx_tfm,
 191                                     key, pos, len, hdr->addr2);
 192         return 0;
 193 }
 194
 195
 196 ieee80211_tx_result
 197 ieee80211_crypto_tkip_encrypt(struct ieee80211_tx_data *tx)
 198 {
 199         struct sk_buff *skb = tx->skb;
 200
 201         ieee80211_tx_set_protected(tx);
 202
 203         do {
 204                 if (tkip_encrypt_skb(tx, skb) < 0)
 205                         return TX_DROP;
 206         } while ((skb = skb->next));
 207
 208         return TX_CONTINUE;
 209 }
 210
 211
 212 ieee80211_rx_result
 213 ieee80211_crypto_tkip_decrypt(struct ieee80211_rx_data *rx)
 214 {
 215         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) rx->skb->data;
 216         int hdrlen, res, hwaccel = 0, wpa_test = 0;
 217         struct ieee80211_key *key = rx->key;
 218         struct sk_buff *skb = rx->skb;
 219         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 220
 221         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 222
 223         if (!ieee80211_is_data(hdr->frame_control))
 224                 return RX_CONTINUE;
 225
 226         if (!rx->sta || skb->len - hdrlen < 12)
 227                 return RX_DROP_UNUSABLE;
 228
 229         if (status->flag & RX_FLAG_DECRYPTED) {
 230                 if (status->flag & RX_FLAG_IV_STRIPPED) {
 231                         /*
 232                          * Hardware took care of all processing, including
 233                          * replay protection, and stripped the ICV/IV so
 234                          * we cannot do any checks here.
 235                          */
 236                         return RX_CONTINUE;
 237                 }
 238
 239                 /* let TKIP code verify IV, but skip decryption */
 240                 hwaccel = 1;
 241         }
 242
 243         res = ieee80211_tkip_decrypt_data(rx->local->wep_rx_tfm,
 244                                           key, skb->data + hdrlen,
 245                                           skb->len - hdrlen, rx->sta->sta.addr,
 246                                           hdr->addr1, hwaccel, rx->queue,
 247                                           &rx->tkip_iv32,
 248                                           &rx->tkip_iv16);
 249         if (res != TKIP_DECRYPT_OK || wpa_test)
 250                 return RX_DROP_UNUSABLE;
 251
 252         /* Trim ICV */
 253         skb_trim(skb, skb->len - TKIP_ICV_LEN);
 254
 255         /* Remove IV */
 256         memmove(skb->data + TKIP_IV_LEN, skb->data, hdrlen);
 257         skb_pull(skb, TKIP_IV_LEN);
 258
 259         return RX_CONTINUE;
 260 }
 261
 262
 263 static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
 264                                 int encrypted)
 265 {
 266         __le16 mask_fc;
 267         int a4_included, mgmt;
 268         u8 qos_tid;
 269         u8 *b_0, *aad;
 270         u16 data_len, len_a;
 271         unsigned int hdrlen;
 272         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 273
 274         b_0 = scratch + 3 * AES_BLOCK_LEN;
 275         aad = scratch + 4 * AES_BLOCK_LEN;
 276
 277         /*
 278          * Mask FC: zero subtype b4 b5 b6 (if not mgmt)
 279          * Retry, PwrMgt, MoreData; set Protected
 280          */
 281         mgmt = ieee80211_is_mgmt(hdr->frame_control);
 282         mask_fc = hdr->frame_control;
 283         mask_fc &= ~cpu_to_le16(IEEE80211_FCTL_RETRY |
 284                                 IEEE80211_FCTL_PM | IEEE80211_FCTL_MOREDATA);
 285         if (!mgmt)
 286                 mask_fc &= ~cpu_to_le16(0x0070);
 287         mask_fc |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
 288
 289         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 290         len_a = hdrlen - 2;
 291         a4_included = ieee80211_has_a4(hdr->frame_control);
 292
 293         if (ieee80211_is_data_qos(hdr->frame_control))
 294                 qos_tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
 295         else
 296                 qos_tid = 0;
 297
 298         data_len = skb->len - hdrlen - CCMP_HDR_LEN;
 299         if (encrypted)
 300                 data_len -= CCMP_MIC_LEN;
 301
 302         /* First block, b_0 */
 303         b_0[0] = 0x59; /* flags: Adata: 1, M: 011, L: 001 */
 304         /* Nonce: Nonce Flags | A2 | PN
 305          * Nonce Flags: Priority (b0..b3) | Management (b4) | Reserved (b5..b7)
 306          */
 307         b_0[1] = qos_tid | (mgmt << 4);
 308         memcpy(&b_0[2], hdr->addr2, ETH_ALEN);
 309         memcpy(&b_0[8], pn, CCMP_PN_LEN);
 310         /* l(m) */
 311         put_unaligned_be16(data_len, &b_0[14]);
 312
 313         /* AAD (extra authenticate-only data) / masked 802.11 header
 314          * FC | A1 | A2 | A3 | SC | [A4] | [QC] */
 315         put_unaligned_be16(len_a, &aad[0]);
 316         put_unaligned(mask_fc, (__le16 *)&aad[2]);
 317         memcpy(&aad[4], &hdr->addr1, 3 * ETH_ALEN);
 318
 319         /* Mask Seq#, leave Frag# */
 320         aad[22] = *((u8 *) &hdr->seq_ctrl) & 0x0f;
 321         aad[23] = 0;
 322
 323         if (a4_included) {
 324                 memcpy(&aad[24], hdr->addr4, ETH_ALEN);
 325                 aad[30] = qos_tid;
 326                 aad[31] = 0;
 327         } else {
 328                 memset(&aad[24], 0, ETH_ALEN + IEEE80211_QOS_CTL_LEN);
 329                 aad[24] = qos_tid;
 330         }
 331 }
 332
 333
 334 static inline void ccmp_pn2hdr(u8 *hdr, u8 *pn, int key_id)
 335 {
 336         hdr[0] = pn[5];
 337         hdr[1] = pn[4];
 338         hdr[2] = 0;
 339         hdr[3] = 0x20 | (key_id << 6);
 340         hdr[4] = pn[3];
 341         hdr[5] = pn[2];
 342         hdr[6] = pn[1];
 343         hdr[7] = pn[0];
 344 }
 345
 346
 347 static inline void ccmp_hdr2pn(u8 *pn, u8 *hdr)
 348 {
 349         pn[0] = hdr[7];
 350         pn[1] = hdr[6];
 351         pn[2] = hdr[5];
 352         pn[3] = hdr[4];
 353         pn[4] = hdr[1];
 354         pn[5] = hdr[0];
 355 }
 356
 357
 358 static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 359 {
 360         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 361         struct ieee80211_key *key = tx->key;
 362         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 363         int hdrlen, len, tail;
 364         u8 *pos, *pn;
 365         int i;
 366         bool skip_hw;
 367
 368         skip_hw = (tx->key->conf.flags & IEEE80211_KEY_FLAG_SW_MGMT) &&
 369                 ieee80211_is_mgmt(hdr->frame_control);
 370
 371         if ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
 372             !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) &&
 373             !skip_hw) {
 374                 /* hwaccel - with no need for preallocated room for CCMP
 375                  * header or MIC fields */
 376                 info->control.hw_key = &tx->key->conf;
 377                 return 0;
 378         }
 379
 380         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 381         len = skb->len - hdrlen;
 382
 383         if (key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)
 384                 tail = 0;
 385         else
 386                 tail = CCMP_MIC_LEN;
 387
 388         if (WARN_ON(skb_tailroom(skb) < tail ||
 389                     skb_headroom(skb) < CCMP_HDR_LEN))
 390                 return -1;
 391
 392         pos = skb_push(skb, CCMP_HDR_LEN);
 393         memmove(pos, pos + CCMP_HDR_LEN, hdrlen);
 394         hdr = (struct ieee80211_hdr *) pos;
 395         pos += hdrlen;
 396
 397         /* PN = PN + 1 */
 398         pn = key->u.ccmp.tx_pn;
 399
 400         for (i = CCMP_PN_LEN - 1; i >= 0; i--) {
 401                 pn[i]++;
 402                 if (pn[i])
 403                         break;
 404         }
 405
 406         ccmp_pn2hdr(pos, pn, key->conf.keyidx);
 407
 408         if ((key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) && !skip_hw) {
 409                 /* hwaccel - with preallocated room for CCMP header */
 410                 info->control.hw_key = &tx->key->conf;
 411                 return 0;
 412         }
 413
 414         pos += CCMP_HDR_LEN;
 415         ccmp_special_blocks(skb, pn, key->u.ccmp.tx_crypto_buf, 0);
 416         ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, key->u.ccmp.tx_crypto_buf, pos, len,
 417                                   pos, skb_put(skb, CCMP_MIC_LEN));
 418
 419         return 0;
 420 }
 421
 422
 423 ieee80211_tx_result
 424 ieee80211_crypto_ccmp_encrypt(struct ieee80211_tx_data *tx)
 425 {
 426         struct sk_buff *skb = tx->skb;
 427
 428         ieee80211_tx_set_protected(tx);
 429
 430         do {
 431                 if (ccmp_encrypt_skb(tx, skb) < 0)
 432                         return TX_DROP;
 433         } while ((skb = skb->next));
 434
 435         return TX_CONTINUE;
 436 }
 437
 438
 439 ieee80211_rx_result
 440 ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
 441 {
 442         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
 443         int hdrlen;
 444         struct ieee80211_key *key = rx->key;
 445         struct sk_buff *skb = rx->skb;
 446         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 447         u8 pn[CCMP_PN_LEN];
 448         int data_len;
 449
 450         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 451
 452         if (!ieee80211_is_data(hdr->frame_control) &&
 453             !ieee80211_is_robust_mgmt_frame(hdr))
 454                 return RX_CONTINUE;
 455
 456         data_len = skb->len - hdrlen - CCMP_HDR_LEN - CCMP_MIC_LEN;
 457         if (!rx->sta || data_len < 0)
 458                 return RX_DROP_UNUSABLE;
 459
 460         if ((status->flag & RX_FLAG_DECRYPTED) &&
 461             (status->flag & RX_FLAG_IV_STRIPPED))
 462                 return RX_CONTINUE;
 463
 464         ccmp_hdr2pn(pn, skb->data + hdrlen);
 465
 466         if (memcmp(pn, key->u.ccmp.rx_pn[rx->queue], CCMP_PN_LEN) <= 0) {
 467                 key->u.ccmp.replays++;
 468                 return RX_DROP_UNUSABLE;
 469         }
 470
 471         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 472                 /* hardware didn't decrypt/verify MIC */
 473                 ccmp_special_blocks(skb, pn, key->u.ccmp.rx_crypto_buf, 1);
 474
 475                 if (ieee80211_aes_ccm_decrypt(
 476                             key->u.ccmp.tfm, key->u.ccmp.rx_crypto_buf,
 477                             skb->data + hdrlen + CCMP_HDR_LEN, data_len,
 478                             skb->data + skb->len - CCMP_MIC_LEN,
 479                             skb->data + hdrlen + CCMP_HDR_LEN))
 480                         return RX_DROP_UNUSABLE;
 481         }
 482
 483         memcpy(key->u.ccmp.rx_pn[rx->queue], pn, CCMP_PN_LEN);
 484
 485         /* Remove CCMP header and MIC */
 486         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 487         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdrlen);
 488         skb_pull(skb, CCMP_HDR_LEN);
 489
 490         return RX_CONTINUE;
 491 }
 492
 493
 494 static void bip_aad(struct sk_buff *skb, u8 *aad)
 495 {
 496         /* BIP AAD: FC(masked) || A1 || A2 || A3 */
 497
 498         /* FC type/subtype */
 499         aad[0] = skb->data[0];
 500         /* Mask FC Retry, PwrMgt, MoreData flags to zero */
 501         aad[1] = skb->data[1] & ~(BIT(4) | BIT(5) | BIT(6));
 502         /* A1 || A2 || A3 */
 503         memcpy(aad + 2, skb->data + 4, 3 * ETH_ALEN);
 504 }
 505
 506
 507 static inline void bip_ipn_swap(u8 *d, const u8 *s)
 508 {
 509         *d++ = s[5];
 510         *d++ = s[4];
 511         *d++ = s[3];
 512         *d++ = s[2];
 513         *d++ = s[1];
 514         *d = s[0];
 515 }
 516
 517
 518 ieee80211_tx_result
 519 ieee80211_crypto_aes_cmac_encrypt(struct ieee80211_tx_data *tx)
 520 {
 521         struct sk_buff *skb = tx->skb;
 522         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 523         struct ieee80211_key *key = tx->key;
 524         struct ieee80211_mmie *mmie;
 525         u8 *pn, aad[20];
 526         int i;
 527
 528         if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) {
 529                 /* hwaccel */
 530                 info->control.hw_key = &tx->key->conf;
 531                 return 0;
 532         }
 533
 534         if (WARN_ON(skb_tailroom(skb) < sizeof(*mmie)))
 535                 return TX_DROP;
 536
 537         mmie = (struct ieee80211_mmie *) skb_put(skb, sizeof(*mmie));
 538         mmie->element_id = WLAN_EID_MMIE;
 539         mmie->length = sizeof(*mmie) - 2;
 540         mmie->key_id = cpu_to_le16(key->conf.keyidx);
 541
 542         /* PN = PN + 1 */
 543         pn = key->u.aes_cmac.tx_pn;
 544
 545         for (i = sizeof(key->u.aes_cmac.tx_pn) - 1; i >= 0; i--) {
 546                 pn[i]++;
 547                 if (pn[i])
 548                         break;
 549         }
 550         bip_ipn_swap(mmie->sequence_number, pn);
 551
 552         bip_aad(skb, aad);
 553
 554         /*
 555          * MIC = AES-128-CMAC(IGTK, AAD || Management Frame Body || MMIE, 64)
 556          */
 557         ieee80211_aes_cmac(key->u.aes_cmac.tfm, key->u.aes_cmac.tx_crypto_buf,
 558                            aad, skb->data + 24, skb->len - 24, mmie->mic);
 559
 560         return TX_CONTINUE;
 561 }
 562
 563
 564 ieee80211_rx_result
 565 ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
 566 {
 567         struct sk_buff *skb = rx->skb;
 568         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 569         struct ieee80211_key *key = rx->key;
 570         struct ieee80211_mmie *mmie;
 571         u8 aad[20], mic[8], ipn[6];
 572         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 573
 574         if (!ieee80211_is_mgmt(hdr->frame_control))
 575                 return RX_CONTINUE;
 576
 577         if ((status->flag & RX_FLAG_DECRYPTED) &&
 578             (status->flag & RX_FLAG_IV_STRIPPED))
 579                 return RX_CONTINUE;
 580
 581         if (skb->len < 24 + sizeof(*mmie))
 582                 return RX_DROP_UNUSABLE;
 583
 584         mmie = (struct ieee80211_mmie *)
 585                 (skb->data + skb->len - sizeof(*mmie));
 586         if (mmie->element_id != WLAN_EID_MMIE ||
 587             mmie->length != sizeof(*mmie) - 2)
 588                 return RX_DROP_UNUSABLE; /* Invalid MMIE */
 589
 590         bip_ipn_swap(ipn, mmie->sequence_number);
 591
 592         if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
 593                 key->u.aes_cmac.replays++;
 594                 return RX_DROP_UNUSABLE;
 595         }
 596
 597         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 598                 /* hardware didn't decrypt/verify MIC */
 599                 bip_aad(skb, aad);
 600                 ieee80211_aes_cmac(key->u.aes_cmac.tfm,
 601                                    key->u.aes_cmac.rx_crypto_buf, aad,
 602                                    skb->data + 24, skb->len - 24, mic);
 603                 if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
 604                         key->u.aes_cmac.icverrors++;
 605                         return RX_DROP_UNUSABLE;
 606                 }
 607         }
 608
 609         memcpy(key->u.aes_cmac.rx_pn, ipn, 6);
 610
 611         /* Remove MMIE */
 612         skb_trim(skb, skb->len - sizeof(*mmie));
 613
 614         return RX_CONTINUE;
 615 }