The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/net80211/ieee80211_crypto_ccmp.c

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    1 /*-
    2  * Copyright (c) 2002-2008 Sam Leffler, Errno Consulting
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   24  */
   25 
   26 #include <sys/cdefs.h>
   27 __FBSDID("$FreeBSD: releng/10.2/sys/net80211/ieee80211_crypto_ccmp.c 209636 2010-07-01 20:50:12Z bschmidt $");
   28 
   29 /*
   30  * IEEE 802.11i AES-CCMP crypto support.
   31  *
   32  * Part of this module is derived from similar code in the Host
   33  * AP driver. The code is used with the consent of the author and
   34  * it's license is included below.
   35  */
   36 #include "opt_wlan.h"
   37 
   38 #include <sys/param.h>
   39 #include <sys/systm.h> 
   40 #include <sys/mbuf.h>   
   41 #include <sys/malloc.h>
   42 #include <sys/kernel.h>
   43 #include <sys/module.h>
   44 
   45 #include <sys/socket.h>
   46 
   47 #include <net/if.h>
   48 #include <net/if_media.h>
   49 #include <net/ethernet.h>
   50 
   51 #include <net80211/ieee80211_var.h>
   52 
   53 #include <crypto/rijndael/rijndael.h>
   54 
   55 #define AES_BLOCK_LEN 16
   56 
   57 struct ccmp_ctx {
   58         struct ieee80211vap *cc_vap;    /* for diagnostics+statistics */
   59         struct ieee80211com *cc_ic;
   60         rijndael_ctx         cc_aes;
   61 };
   62 
   63 static  void *ccmp_attach(struct ieee80211vap *, struct ieee80211_key *);
   64 static  void ccmp_detach(struct ieee80211_key *);
   65 static  int ccmp_setkey(struct ieee80211_key *);
   66 static  int ccmp_encap(struct ieee80211_key *k, struct mbuf *, uint8_t keyid);
   67 static  int ccmp_decap(struct ieee80211_key *, struct mbuf *, int);
   68 static  int ccmp_enmic(struct ieee80211_key *, struct mbuf *, int);
   69 static  int ccmp_demic(struct ieee80211_key *, struct mbuf *, int);
   70 
   71 static const struct ieee80211_cipher ccmp = {
   72         .ic_name        = "AES-CCM",
   73         .ic_cipher      = IEEE80211_CIPHER_AES_CCM,
   74         .ic_header      = IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN +
   75                           IEEE80211_WEP_EXTIVLEN,
   76         .ic_trailer     = IEEE80211_WEP_MICLEN,
   77         .ic_miclen      = 0,
   78         .ic_attach      = ccmp_attach,
   79         .ic_detach      = ccmp_detach,
   80         .ic_setkey      = ccmp_setkey,
   81         .ic_encap       = ccmp_encap,
   82         .ic_decap       = ccmp_decap,
   83         .ic_enmic       = ccmp_enmic,
   84         .ic_demic       = ccmp_demic,
   85 };
   86 
   87 static  int ccmp_encrypt(struct ieee80211_key *, struct mbuf *, int hdrlen);
   88 static  int ccmp_decrypt(struct ieee80211_key *, u_int64_t pn,
   89                 struct mbuf *, int hdrlen);
   90 
   91 /* number of references from net80211 layer */
   92 static  int nrefs = 0;
   93 
   94 static void *
   95 ccmp_attach(struct ieee80211vap *vap, struct ieee80211_key *k)
   96 {
   97         struct ccmp_ctx *ctx;
   98 
   99         ctx = (struct ccmp_ctx *) malloc(sizeof(struct ccmp_ctx),
  100                 M_80211_CRYPTO, M_NOWAIT | M_ZERO);
  101         if (ctx == NULL) {
  102                 vap->iv_stats.is_crypto_nomem++;
  103                 return NULL;
  104         }
  105         ctx->cc_vap = vap;
  106         ctx->cc_ic = vap->iv_ic;
  107         nrefs++;                        /* NB: we assume caller locking */
  108         return ctx;
  109 }
  110 
  111 static void
  112 ccmp_detach(struct ieee80211_key *k)
  113 {
  114         struct ccmp_ctx *ctx = k->wk_private;
  115 
  116         free(ctx, M_80211_CRYPTO);
  117         KASSERT(nrefs > 0, ("imbalanced attach/detach"));
  118         nrefs--;                        /* NB: we assume caller locking */
  119 }
  120 
  121 static int
  122 ccmp_setkey(struct ieee80211_key *k)
  123 {
  124         struct ccmp_ctx *ctx = k->wk_private;
  125 
  126         if (k->wk_keylen != (128/NBBY)) {
  127                 IEEE80211_DPRINTF(ctx->cc_vap, IEEE80211_MSG_CRYPTO,
  128                         "%s: Invalid key length %u, expecting %u\n",
  129                         __func__, k->wk_keylen, 128/NBBY);
  130                 return 0;
  131         }
  132         if (k->wk_flags & IEEE80211_KEY_SWENCRYPT)
  133                 rijndael_set_key(&ctx->cc_aes, k->wk_key, k->wk_keylen*NBBY);
  134         return 1;
  135 }
  136 
  137 /*
  138  * Add privacy headers appropriate for the specified key.
  139  */
  140 static int
  141 ccmp_encap(struct ieee80211_key *k, struct mbuf *m, uint8_t keyid)
  142 {
  143         struct ccmp_ctx *ctx = k->wk_private;
  144         struct ieee80211com *ic = ctx->cc_ic;
  145         uint8_t *ivp;
  146         int hdrlen;
  147 
  148         hdrlen = ieee80211_hdrspace(ic, mtod(m, void *));
  149 
  150         /*
  151          * Copy down 802.11 header and add the IV, KeyID, and ExtIV.
  152          */
  153         M_PREPEND(m, ccmp.ic_header, M_NOWAIT);
  154         if (m == NULL)
  155                 return 0;
  156         ivp = mtod(m, uint8_t *);
  157         ovbcopy(ivp + ccmp.ic_header, ivp, hdrlen);
  158         ivp += hdrlen;
  159 
  160         k->wk_keytsc++;         /* XXX wrap at 48 bits */
  161         ivp[0] = k->wk_keytsc >> 0;             /* PN0 */
  162         ivp[1] = k->wk_keytsc >> 8;             /* PN1 */
  163         ivp[2] = 0;                             /* Reserved */
  164         ivp[3] = keyid | IEEE80211_WEP_EXTIV;   /* KeyID | ExtID */
  165         ivp[4] = k->wk_keytsc >> 16;            /* PN2 */
  166         ivp[5] = k->wk_keytsc >> 24;            /* PN3 */
  167         ivp[6] = k->wk_keytsc >> 32;            /* PN4 */
  168         ivp[7] = k->wk_keytsc >> 40;            /* PN5 */
  169 
  170         /*
  171          * Finally, do software encrypt if neeed.
  172          */
  173         if ((k->wk_flags & IEEE80211_KEY_SWENCRYPT) &&
  174             !ccmp_encrypt(k, m, hdrlen))
  175                 return 0;
  176 
  177         return 1;
  178 }
  179 
  180 /*
  181  * Add MIC to the frame as needed.
  182  */
  183 static int
  184 ccmp_enmic(struct ieee80211_key *k, struct mbuf *m, int force)
  185 {
  186 
  187         return 1;
  188 }
  189 
  190 static __inline uint64_t
  191 READ_6(uint8_t b0, uint8_t b1, uint8_t b2, uint8_t b3, uint8_t b4, uint8_t b5)
  192 {
  193         uint32_t iv32 = (b0 << 0) | (b1 << 8) | (b2 << 16) | (b3 << 24);
  194         uint16_t iv16 = (b4 << 0) | (b5 << 8);
  195         return (((uint64_t)iv16) << 32) | iv32;
  196 }
  197 
  198 /*
  199  * Validate and strip privacy headers (and trailer) for a
  200  * received frame. The specified key should be correct but
  201  * is also verified.
  202  */
  203 static int
  204 ccmp_decap(struct ieee80211_key *k, struct mbuf *m, int hdrlen)
  205 {
  206         struct ccmp_ctx *ctx = k->wk_private;
  207         struct ieee80211vap *vap = ctx->cc_vap;
  208         struct ieee80211_frame *wh;
  209         uint8_t *ivp, tid;
  210         uint64_t pn;
  211 
  212         /*
  213          * Header should have extended IV and sequence number;
  214          * verify the former and validate the latter.
  215          */
  216         wh = mtod(m, struct ieee80211_frame *);
  217         ivp = mtod(m, uint8_t *) + hdrlen;
  218         if ((ivp[IEEE80211_WEP_IVLEN] & IEEE80211_WEP_EXTIV) == 0) {
  219                 /*
  220                  * No extended IV; discard frame.
  221                  */
  222                 IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, wh->i_addr2,
  223                         "%s", "missing ExtIV for AES-CCM cipher");
  224                 vap->iv_stats.is_rx_ccmpformat++;
  225                 return 0;
  226         }
  227         tid = ieee80211_gettid(wh);
  228         pn = READ_6(ivp[0], ivp[1], ivp[4], ivp[5], ivp[6], ivp[7]);
  229         if (pn <= k->wk_keyrsc[tid] &&
  230             (k->wk_flags & IEEE80211_KEY_NOREPLAY) == 0) {
  231                 /*
  232                  * Replay violation.
  233                  */
  234                 ieee80211_notify_replay_failure(vap, wh, k, pn, tid);
  235                 vap->iv_stats.is_rx_ccmpreplay++;
  236                 return 0;
  237         }
  238 
  239         /*
  240          * Check if the device handled the decrypt in hardware.
  241          * If so we just strip the header; otherwise we need to
  242          * handle the decrypt in software.  Note that for the
  243          * latter we leave the header in place for use in the
  244          * decryption work.
  245          */
  246         if ((k->wk_flags & IEEE80211_KEY_SWDECRYPT) &&
  247             !ccmp_decrypt(k, pn, m, hdrlen))
  248                 return 0;
  249 
  250         /*
  251          * Copy up 802.11 header and strip crypto bits.
  252          */
  253         ovbcopy(mtod(m, void *), mtod(m, uint8_t *) + ccmp.ic_header, hdrlen);
  254         m_adj(m, ccmp.ic_header);
  255         m_adj(m, -ccmp.ic_trailer);
  256 
  257         /*
  258          * Ok to update rsc now.
  259          */
  260         k->wk_keyrsc[tid] = pn;
  261 
  262         return 1;
  263 }
  264 
  265 /*
  266  * Verify and strip MIC from the frame.
  267  */
  268 static int
  269 ccmp_demic(struct ieee80211_key *k, struct mbuf *m, int force)
  270 {
  271         return 1;
  272 }
  273 
  274 static __inline void
  275 xor_block(uint8_t *b, const uint8_t *a, size_t len)
  276 {
  277         int i;
  278         for (i = 0; i < len; i++)
  279                 b[i] ^= a[i];
  280 }
  281 
  282 /*
  283  * Host AP crypt: host-based CCMP encryption implementation for Host AP driver
  284  *
  285  * Copyright (c) 2003-2004, Jouni Malinen <jkmaline@cc.hut.fi>
  286  *
  287  * This program is free software; you can redistribute it and/or modify
  288  * it under the terms of the GNU General Public License version 2 as
  289  * published by the Free Software Foundation. See README and COPYING for
  290  * more details.
  291  *
  292  * Alternatively, this software may be distributed under the terms of BSD
  293  * license.
  294  */
  295 
  296 static void
  297 ccmp_init_blocks(rijndael_ctx *ctx, struct ieee80211_frame *wh,
  298         u_int64_t pn, size_t dlen,
  299         uint8_t b0[AES_BLOCK_LEN], uint8_t aad[2 * AES_BLOCK_LEN],
  300         uint8_t auth[AES_BLOCK_LEN], uint8_t s0[AES_BLOCK_LEN])
  301 {
  302 #define IS_QOS_DATA(wh) IEEE80211_QOS_HAS_SEQ(wh)
  303 
  304         /* CCM Initial Block:
  305          * Flag (Include authentication header, M=3 (8-octet MIC),
  306          *       L=1 (2-octet Dlen))
  307          * Nonce: 0x00 | A2 | PN
  308          * Dlen */
  309         b0[0] = 0x59;
  310         /* NB: b0[1] set below */
  311         IEEE80211_ADDR_COPY(b0 + 2, wh->i_addr2);
  312         b0[8] = pn >> 40;
  313         b0[9] = pn >> 32;
  314         b0[10] = pn >> 24;
  315         b0[11] = pn >> 16;
  316         b0[12] = pn >> 8;
  317         b0[13] = pn >> 0;
  318         b0[14] = (dlen >> 8) & 0xff;
  319         b0[15] = dlen & 0xff;
  320 
  321         /* AAD:
  322          * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
  323          * A1 | A2 | A3
  324          * SC with bits 4..15 (seq#) masked to zero
  325          * A4 (if present)
  326          * QC (if present)
  327          */
  328         aad[0] = 0;     /* AAD length >> 8 */
  329         /* NB: aad[1] set below */
  330         aad[2] = wh->i_fc[0] & 0x8f;    /* XXX magic #s */
  331         aad[3] = wh->i_fc[1] & 0xc7;    /* XXX magic #s */
  332         /* NB: we know 3 addresses are contiguous */
  333         memcpy(aad + 4, wh->i_addr1, 3 * IEEE80211_ADDR_LEN);
  334         aad[22] = wh->i_seq[0] & IEEE80211_SEQ_FRAG_MASK;
  335         aad[23] = 0; /* all bits masked */
  336         /*
  337          * Construct variable-length portion of AAD based
  338          * on whether this is a 4-address frame/QOS frame.
  339          * We always zero-pad to 32 bytes before running it
  340          * through the cipher.
  341          *
  342          * We also fill in the priority bits of the CCM
  343          * initial block as we know whether or not we have
  344          * a QOS frame.
  345          */
  346         if (IEEE80211_IS_DSTODS(wh)) {
  347                 IEEE80211_ADDR_COPY(aad + 24,
  348                         ((struct ieee80211_frame_addr4 *)wh)->i_addr4);
  349                 if (IS_QOS_DATA(wh)) {
  350                         struct ieee80211_qosframe_addr4 *qwh4 =
  351                                 (struct ieee80211_qosframe_addr4 *) wh;
  352                         aad[30] = qwh4->i_qos[0] & 0x0f;/* just priority bits */
  353                         aad[31] = 0;
  354                         b0[1] = aad[30];
  355                         aad[1] = 22 + IEEE80211_ADDR_LEN + 2;
  356                 } else {
  357                         *(uint16_t *)&aad[30] = 0;
  358                         b0[1] = 0;
  359                         aad[1] = 22 + IEEE80211_ADDR_LEN;
  360                 }
  361         } else {
  362                 if (IS_QOS_DATA(wh)) {
  363                         struct ieee80211_qosframe *qwh =
  364                                 (struct ieee80211_qosframe*) wh;
  365                         aad[24] = qwh->i_qos[0] & 0x0f; /* just priority bits */
  366                         aad[25] = 0;
  367                         b0[1] = aad[24];
  368                         aad[1] = 22 + 2;
  369                 } else {
  370                         *(uint16_t *)&aad[24] = 0;
  371                         b0[1] = 0;
  372                         aad[1] = 22;
  373                 }
  374                 *(uint16_t *)&aad[26] = 0;
  375                 *(uint32_t *)&aad[28] = 0;
  376         }
  377 
  378         /* Start with the first block and AAD */
  379         rijndael_encrypt(ctx, b0, auth);
  380         xor_block(auth, aad, AES_BLOCK_LEN);
  381         rijndael_encrypt(ctx, auth, auth);
  382         xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
  383         rijndael_encrypt(ctx, auth, auth);
  384         b0[0] &= 0x07;
  385         b0[14] = b0[15] = 0;
  386         rijndael_encrypt(ctx, b0, s0);
  387 #undef  IS_QOS_DATA
  388 }
  389 
  390 #define CCMP_ENCRYPT(_i, _b, _b0, _pos, _e, _len) do {  \
  391         /* Authentication */                            \
  392         xor_block(_b, _pos, _len);                      \
  393         rijndael_encrypt(&ctx->cc_aes, _b, _b);         \
  394         /* Encryption, with counter */                  \
  395         _b0[14] = (_i >> 8) & 0xff;                     \
  396         _b0[15] = _i & 0xff;                            \
  397         rijndael_encrypt(&ctx->cc_aes, _b0, _e);        \
  398         xor_block(_pos, _e, _len);                      \
  399 } while (0)
  400 
  401 static int
  402 ccmp_encrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen)
  403 {
  404         struct ccmp_ctx *ctx = key->wk_private;
  405         struct ieee80211_frame *wh;
  406         struct mbuf *m = m0;
  407         int data_len, i, space;
  408         uint8_t aad[2 * AES_BLOCK_LEN], b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN],
  409                 e[AES_BLOCK_LEN], s0[AES_BLOCK_LEN];
  410         uint8_t *pos;
  411 
  412         ctx->cc_vap->iv_stats.is_crypto_ccmp++;
  413 
  414         wh = mtod(m, struct ieee80211_frame *);
  415         data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header);
  416         ccmp_init_blocks(&ctx->cc_aes, wh, key->wk_keytsc,
  417                 data_len, b0, aad, b, s0);
  418 
  419         i = 1;
  420         pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
  421         /* NB: assumes header is entirely in first mbuf */
  422         space = m->m_len - (hdrlen + ccmp.ic_header);
  423         for (;;) {
  424                 if (space > data_len)
  425                         space = data_len;
  426                 /*
  427                  * Do full blocks.
  428                  */
  429                 while (space >= AES_BLOCK_LEN) {
  430                         CCMP_ENCRYPT(i, b, b0, pos, e, AES_BLOCK_LEN);
  431                         pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
  432                         data_len -= AES_BLOCK_LEN;
  433                         i++;
  434                 }
  435                 if (data_len <= 0)              /* no more data */
  436                         break;
  437                 m = m->m_next;
  438                 if (m == NULL) {                /* last buffer */
  439                         if (space != 0) {
  440                                 /*
  441                                  * Short last block.
  442                                  */
  443                                 CCMP_ENCRYPT(i, b, b0, pos, e, space);
  444                         }
  445                         break;
  446                 }
  447                 if (space != 0) {
  448                         uint8_t *pos_next;
  449                         int space_next;
  450                         int len, dl, sp;
  451                         struct mbuf *n;
  452 
  453                         /*
  454                          * Block straddles one or more mbufs, gather data
  455                          * into the block buffer b, apply the cipher, then
  456                          * scatter the results back into the mbuf chain.
  457                          * The buffer will automatically get space bytes
  458                          * of data at offset 0 copied in+out by the
  459                          * CCMP_ENCRYPT request so we must take care of
  460                          * the remaining data.
  461                          */
  462                         n = m;
  463                         dl = data_len;
  464                         sp = space;
  465                         for (;;) {
  466                                 pos_next = mtod(n, uint8_t *);
  467                                 len = min(dl, AES_BLOCK_LEN);
  468                                 space_next = len > sp ? len - sp : 0;
  469                                 if (n->m_len >= space_next) {
  470                                         /*
  471                                          * This mbuf has enough data; just grab
  472                                          * what we need and stop.
  473                                          */
  474                                         xor_block(b+sp, pos_next, space_next);
  475                                         break;
  476                                 }
  477                                 /*
  478                                  * This mbuf's contents are insufficient,
  479                                  * take 'em all and prepare to advance to
  480                                  * the next mbuf.
  481                                  */
  482                                 xor_block(b+sp, pos_next, n->m_len);
  483                                 sp += n->m_len, dl -= n->m_len;
  484                                 n = n->m_next;
  485                                 if (n == NULL)
  486                                         break;
  487                         }
  488 
  489                         CCMP_ENCRYPT(i, b, b0, pos, e, space);
  490 
  491                         /* NB: just like above, but scatter data to mbufs */
  492                         dl = data_len;
  493                         sp = space;
  494                         for (;;) {
  495                                 pos_next = mtod(m, uint8_t *);
  496                                 len = min(dl, AES_BLOCK_LEN);
  497                                 space_next = len > sp ? len - sp : 0;
  498                                 if (m->m_len >= space_next) {
  499                                         xor_block(pos_next, e+sp, space_next);
  500                                         break;
  501                                 }
  502                                 xor_block(pos_next, e+sp, m->m_len);
  503                                 sp += m->m_len, dl -= m->m_len;
  504                                 m = m->m_next;
  505                                 if (m == NULL)
  506                                         goto done;
  507                         }
  508                         /*
  509                          * Do bookkeeping.  m now points to the last mbuf
  510                          * we grabbed data from.  We know we consumed a
  511                          * full block of data as otherwise we'd have hit
  512                          * the end of the mbuf chain, so deduct from data_len.
  513                          * Otherwise advance the block number (i) and setup
  514                          * pos+space to reflect contents of the new mbuf.
  515                          */
  516                         data_len -= AES_BLOCK_LEN;
  517                         i++;
  518                         pos = pos_next + space_next;
  519                         space = m->m_len - space_next;
  520                 } else {
  521                         /*
  522                          * Setup for next buffer.
  523                          */
  524                         pos = mtod(m, uint8_t *);
  525                         space = m->m_len;
  526                 }
  527         }
  528 done:
  529         /* tack on MIC */
  530         xor_block(b, s0, ccmp.ic_trailer);
  531         return m_append(m0, ccmp.ic_trailer, b);
  532 }
  533 #undef CCMP_ENCRYPT
  534 
  535 #define CCMP_DECRYPT(_i, _b, _b0, _pos, _a, _len) do {  \
  536         /* Decrypt, with counter */                     \
  537         _b0[14] = (_i >> 8) & 0xff;                     \
  538         _b0[15] = _i & 0xff;                            \
  539         rijndael_encrypt(&ctx->cc_aes, _b0, _b);        \
  540         xor_block(_pos, _b, _len);                      \
  541         /* Authentication */                            \
  542         xor_block(_a, _pos, _len);                      \
  543         rijndael_encrypt(&ctx->cc_aes, _a, _a);         \
  544 } while (0)
  545 
  546 static int
  547 ccmp_decrypt(struct ieee80211_key *key, u_int64_t pn, struct mbuf *m, int hdrlen)
  548 {
  549         struct ccmp_ctx *ctx = key->wk_private;
  550         struct ieee80211vap *vap = ctx->cc_vap;
  551         struct ieee80211_frame *wh;
  552         uint8_t aad[2 * AES_BLOCK_LEN];
  553         uint8_t b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN], a[AES_BLOCK_LEN];
  554         uint8_t mic[AES_BLOCK_LEN];
  555         size_t data_len;
  556         int i;
  557         uint8_t *pos;
  558         u_int space;
  559 
  560         ctx->cc_vap->iv_stats.is_crypto_ccmp++;
  561 
  562         wh = mtod(m, struct ieee80211_frame *);
  563         data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header + ccmp.ic_trailer);
  564         ccmp_init_blocks(&ctx->cc_aes, wh, pn, data_len, b0, aad, a, b);
  565         m_copydata(m, m->m_pkthdr.len - ccmp.ic_trailer, ccmp.ic_trailer, mic);
  566         xor_block(mic, b, ccmp.ic_trailer);
  567 
  568         i = 1;
  569         pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
  570         space = m->m_len - (hdrlen + ccmp.ic_header);
  571         for (;;) {
  572                 if (space > data_len)
  573                         space = data_len;
  574                 while (space >= AES_BLOCK_LEN) {
  575                         CCMP_DECRYPT(i, b, b0, pos, a, AES_BLOCK_LEN);
  576                         pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
  577                         data_len -= AES_BLOCK_LEN;
  578                         i++;
  579                 }
  580                 if (data_len <= 0)              /* no more data */
  581                         break;
  582                 m = m->m_next;
  583                 if (m == NULL) {                /* last buffer */
  584                         if (space != 0)         /* short last block */
  585                                 CCMP_DECRYPT(i, b, b0, pos, a, space);
  586                         break;
  587                 }
  588                 if (space != 0) {
  589                         uint8_t *pos_next;
  590                         u_int space_next;
  591                         u_int len;
  592 
  593                         /*
  594                          * Block straddles buffers, split references.  We
  595                          * do not handle splits that require >2 buffers
  596                          * since rx'd frames are never badly fragmented
  597                          * because drivers typically recv in clusters.
  598                          */
  599                         pos_next = mtod(m, uint8_t *);
  600                         len = min(data_len, AES_BLOCK_LEN);
  601                         space_next = len > space ? len - space : 0;
  602                         KASSERT(m->m_len >= space_next,
  603                                 ("not enough data in following buffer, "
  604                                 "m_len %u need %u\n", m->m_len, space_next));
  605 
  606                         xor_block(b+space, pos_next, space_next);
  607                         CCMP_DECRYPT(i, b, b0, pos, a, space);
  608                         xor_block(pos_next, b+space, space_next);
  609                         data_len -= len;
  610                         i++;
  611 
  612                         pos = pos_next + space_next;
  613                         space = m->m_len - space_next;
  614                 } else {
  615                         /*
  616                          * Setup for next buffer.
  617                          */
  618                         pos = mtod(m, uint8_t *);
  619                         space = m->m_len;
  620                 }
  621         }
  622         if (memcmp(mic, a, ccmp.ic_trailer) != 0) {
  623                 IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, wh->i_addr2,
  624                     "%s", "AES-CCM decrypt failed; MIC mismatch");
  625                 vap->iv_stats.is_rx_ccmpmic++;
  626                 return 0;
  627         }
  628         return 1;
  629 }
  630 #undef CCMP_DECRYPT
  631 
  632 /*
  633  * Module glue.
  634  */
  635 IEEE80211_CRYPTO_MODULE(ccmp, 1);

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