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