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) 2002-2007 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("$FreeBSD$");
   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 <sys/param.h>
   37 #include <sys/systm.h> 
   38 #include <sys/mbuf.h>   
   39 #include <sys/malloc.h>
   40 #include <sys/kernel.h>
   41 #include <sys/module.h>
   42 
   43 #include <sys/socket.h>
   44 
   45 #include <net/if.h>
   46 #include <net/if_media.h>
   47 #include <net/ethernet.h>
   48 
   49 #include <net80211/ieee80211_var.h>
   50 
   51 #include <crypto/rijndael/rijndael.h>
   52 
   53 #define AES_BLOCK_LEN 16
   54 
   55 struct ccmp_ctx {
   56         struct ieee80211com *cc_ic;     /* for diagnostics */
   57         rijndael_ctx         cc_aes;
   58 };
   59 
   60 static  void *ccmp_attach(struct ieee80211com *, struct ieee80211_key *);
   61 static  void ccmp_detach(struct ieee80211_key *);
   62 static  int ccmp_setkey(struct ieee80211_key *);
   63 static  int ccmp_encap(struct ieee80211_key *k, struct mbuf *, uint8_t keyid);
   64 static  int ccmp_decap(struct ieee80211_key *, struct mbuf *, int);
   65 static  int ccmp_enmic(struct ieee80211_key *, struct mbuf *, int);
   66 static  int ccmp_demic(struct ieee80211_key *, struct mbuf *, int);
   67 
   68 static const struct ieee80211_cipher ccmp = {
   69         .ic_name        = "AES-CCM",
   70         .ic_cipher      = IEEE80211_CIPHER_AES_CCM,
   71         .ic_header      = IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN +
   72                           IEEE80211_WEP_EXTIVLEN,
   73         .ic_trailer     = IEEE80211_WEP_MICLEN,
   74         .ic_miclen      = 0,
   75         .ic_attach      = ccmp_attach,
   76         .ic_detach      = ccmp_detach,
   77         .ic_setkey      = ccmp_setkey,
   78         .ic_encap       = ccmp_encap,
   79         .ic_decap       = ccmp_decap,
   80         .ic_enmic       = ccmp_enmic,
   81         .ic_demic       = ccmp_demic,
   82 };
   83 
   84 static  int ccmp_encrypt(struct ieee80211_key *, struct mbuf *, int hdrlen);
   85 static  int ccmp_decrypt(struct ieee80211_key *, u_int64_t pn,
   86                 struct mbuf *, int hdrlen);
   87 
   88 /* number of references from net80211 layer */
   89 static  int nrefs = 0;
   90 
   91 static void *
   92 ccmp_attach(struct ieee80211com *ic, struct ieee80211_key *k)
   93 {
   94         struct ccmp_ctx *ctx;
   95 
   96         MALLOC(ctx, struct ccmp_ctx *, sizeof(struct ccmp_ctx),
   97                 M_DEVBUF, M_NOWAIT | M_ZERO);
   98         if (ctx == NULL) {
   99                 ic->ic_stats.is_crypto_nomem++;
  100                 return NULL;
  101         }
  102         ctx->cc_ic = ic;
  103         nrefs++;                        /* NB: we assume caller locking */
  104         return ctx;
  105 }
  106 
  107 static void
  108 ccmp_detach(struct ieee80211_key *k)
  109 {
  110         struct ccmp_ctx *ctx = k->wk_private;
  111 
  112         FREE(ctx, M_DEVBUF);
  113         KASSERT(nrefs > 0, ("imbalanced attach/detach"));
  114         nrefs--;                        /* NB: we assume caller locking */
  115 }
  116 
  117 static int
  118 ccmp_setkey(struct ieee80211_key *k)
  119 {
  120         struct ccmp_ctx *ctx = k->wk_private;
  121 
  122         if (k->wk_keylen != (128/NBBY)) {
  123                 IEEE80211_DPRINTF(ctx->cc_ic, IEEE80211_MSG_CRYPTO,
  124                         "%s: Invalid key length %u, expecting %u\n",
  125                         __func__, k->wk_keylen, 128/NBBY);
  126                 return 0;
  127         }
  128         if (k->wk_flags & IEEE80211_KEY_SWCRYPT)
  129                 rijndael_set_key(&ctx->cc_aes, k->wk_key, k->wk_keylen*NBBY);
  130         return 1;
  131 }
  132 
  133 /*
  134  * Add privacy headers appropriate for the specified key.
  135  */
  136 static int
  137 ccmp_encap(struct ieee80211_key *k, struct mbuf *m, uint8_t keyid)
  138 {
  139         struct ccmp_ctx *ctx = k->wk_private;
  140         struct ieee80211com *ic = ctx->cc_ic;
  141         uint8_t *ivp;
  142         int hdrlen;
  143 
  144         hdrlen = ieee80211_hdrspace(ic, mtod(m, void *));
  145 
  146         /*
  147          * Copy down 802.11 header and add the IV, KeyID, and ExtIV.
  148          */
  149         M_PREPEND(m, ccmp.ic_header, M_NOWAIT);
  150         if (m == NULL)
  151                 return 0;
  152         ivp = mtod(m, uint8_t *);
  153         ovbcopy(ivp + ccmp.ic_header, ivp, hdrlen);
  154         ivp += hdrlen;
  155 
  156         k->wk_keytsc++;         /* XXX wrap at 48 bits */
  157         ivp[0] = k->wk_keytsc >> 0;             /* PN0 */
  158         ivp[1] = k->wk_keytsc >> 8;             /* PN1 */
  159         ivp[2] = 0;                             /* Reserved */
  160         ivp[3] = keyid | IEEE80211_WEP_EXTIV;   /* KeyID | ExtID */
  161         ivp[4] = k->wk_keytsc >> 16;            /* PN2 */
  162         ivp[5] = k->wk_keytsc >> 24;            /* PN3 */
  163         ivp[6] = k->wk_keytsc >> 32;            /* PN4 */
  164         ivp[7] = k->wk_keytsc >> 40;            /* PN5 */
  165 
  166         /*
  167          * Finally, do software encrypt if neeed.
  168          */
  169         if ((k->wk_flags & IEEE80211_KEY_SWCRYPT) &&
  170             !ccmp_encrypt(k, m, hdrlen))
  171                 return 0;
  172 
  173         return 1;
  174 }
  175 
  176 /*
  177  * Add MIC to the frame as needed.
  178  */
  179 static int
  180 ccmp_enmic(struct ieee80211_key *k, struct mbuf *m, int force)
  181 {
  182 
  183         return 1;
  184 }
  185 
  186 static __inline uint64_t
  187 READ_6(uint8_t b0, uint8_t b1, uint8_t b2, uint8_t b3, uint8_t b4, uint8_t b5)
  188 {
  189         uint32_t iv32 = (b0 << 0) | (b1 << 8) | (b2 << 16) | (b3 << 24);
  190         uint16_t iv16 = (b4 << 0) | (b5 << 8);
  191         return (((uint64_t)iv16) << 32) | iv32;
  192 }
  193 
  194 /*
  195  * Validate and strip privacy headers (and trailer) for a
  196  * received frame. The specified key should be correct but
  197  * is also verified.
  198  */
  199 static int
  200 ccmp_decap(struct ieee80211_key *k, struct mbuf *m, int hdrlen)
  201 {
  202         struct ccmp_ctx *ctx = k->wk_private;
  203         struct ieee80211_frame *wh;
  204         uint8_t *ivp;
  205         uint64_t pn;
  206 
  207         /*
  208          * Header should have extended IV and sequence number;
  209          * verify the former and validate the latter.
  210          */
  211         wh = mtod(m, struct ieee80211_frame *);
  212         ivp = mtod(m, uint8_t *) + hdrlen;
  213         if ((ivp[IEEE80211_WEP_IVLEN] & IEEE80211_WEP_EXTIV) == 0) {
  214                 /*
  215                  * No extended IV; discard frame.
  216                  */
  217                 IEEE80211_DPRINTF(ctx->cc_ic, IEEE80211_MSG_CRYPTO,
  218                         "[%s] Missing ExtIV for AES-CCM cipher\n",
  219                         ether_sprintf(wh->i_addr2));
  220                 ctx->cc_ic->ic_stats.is_rx_ccmpformat++;
  221                 return 0;
  222         }
  223         pn = READ_6(ivp[0], ivp[1], ivp[4], ivp[5], ivp[6], ivp[7]);
  224         if (pn <= k->wk_keyrsc) {
  225                 /*
  226                  * Replay violation.
  227                  */
  228                 ieee80211_notify_replay_failure(ctx->cc_ic, wh, k, pn);
  229                 ctx->cc_ic->ic_stats.is_rx_ccmpreplay++;
  230                 return 0;
  231         }
  232 
  233         /*
  234          * Check if the device handled the decrypt in hardware.
  235          * If so we just strip the header; otherwise we need to
  236          * handle the decrypt in software.  Note that for the
  237          * latter we leave the header in place for use in the
  238          * decryption work.
  239          */
  240         if ((k->wk_flags & IEEE80211_KEY_SWCRYPT) &&
  241             !ccmp_decrypt(k, pn, m, hdrlen))
  242                 return 0;
  243 
  244         /*
  245          * Copy up 802.11 header and strip crypto bits.
  246          */
  247         ovbcopy(mtod(m, void *), mtod(m, uint8_t *) + ccmp.ic_header, hdrlen);
  248         m_adj(m, ccmp.ic_header);
  249         m_adj(m, -ccmp.ic_trailer);
  250 
  251         /*
  252          * Ok to update rsc now.
  253          */
  254         k->wk_keyrsc = pn;
  255 
  256         return 1;
  257 }
  258 
  259 /*
  260  * Verify and strip MIC from the frame.
  261  */
  262 static int
  263 ccmp_demic(struct ieee80211_key *k, struct mbuf *m, int force)
  264 {
  265         return 1;
  266 }
  267 
  268 static __inline void
  269 xor_block(uint8_t *b, const uint8_t *a, size_t len)
  270 {
  271         int i;
  272         for (i = 0; i < len; i++)
  273                 b[i] ^= a[i];
  274 }
  275 
  276 /*
  277  * Host AP crypt: host-based CCMP encryption implementation for Host AP driver
  278  *
  279  * Copyright (c) 2003-2004, Jouni Malinen <jkmaline@cc.hut.fi>
  280  *
  281  * This program is free software; you can redistribute it and/or modify
  282  * it under the terms of the GNU General Public License version 2 as
  283  * published by the Free Software Foundation. See README and COPYING for
  284  * more details.
  285  *
  286  * Alternatively, this software may be distributed under the terms of BSD
  287  * license.
  288  */
  289 
  290 static void
  291 ccmp_init_blocks(rijndael_ctx *ctx, struct ieee80211_frame *wh,
  292         u_int64_t pn, size_t dlen,
  293         uint8_t b0[AES_BLOCK_LEN], uint8_t aad[2 * AES_BLOCK_LEN],
  294         uint8_t auth[AES_BLOCK_LEN], uint8_t s0[AES_BLOCK_LEN])
  295 {
  296 #define IS_4ADDRESS(wh) \
  297         ((wh->i_fc[1] & IEEE80211_FC1_DIR_MASK) == IEEE80211_FC1_DIR_DSTODS)
  298 #define IS_QOS_DATA(wh) IEEE80211_QOS_HAS_SEQ(wh)
  299 
  300         /* CCM Initial Block:
  301          * Flag (Include authentication header, M=3 (8-octet MIC),
  302          *       L=1 (2-octet Dlen))
  303          * Nonce: 0x00 | A2 | PN
  304          * Dlen */
  305         b0[0] = 0x59;
  306         /* NB: b0[1] set below */
  307         IEEE80211_ADDR_COPY(b0 + 2, wh->i_addr2);
  308         b0[8] = pn >> 40;
  309         b0[9] = pn >> 32;
  310         b0[10] = pn >> 24;
  311         b0[11] = pn >> 16;
  312         b0[12] = pn >> 8;
  313         b0[13] = pn >> 0;
  314         b0[14] = (dlen >> 8) & 0xff;
  315         b0[15] = dlen & 0xff;
  316 
  317         /* AAD:
  318          * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
  319          * A1 | A2 | A3
  320          * SC with bits 4..15 (seq#) masked to zero
  321          * A4 (if present)
  322          * QC (if present)
  323          */
  324         aad[0] = 0;     /* AAD length >> 8 */
  325         /* NB: aad[1] set below */
  326         aad[2] = wh->i_fc[0] & 0x8f;    /* XXX magic #s */
  327         aad[3] = wh->i_fc[1] & 0xc7;    /* XXX magic #s */
  328         /* NB: we know 3 addresses are contiguous */
  329         memcpy(aad + 4, wh->i_addr1, 3 * IEEE80211_ADDR_LEN);
  330         aad[22] = wh->i_seq[0] & IEEE80211_SEQ_FRAG_MASK;
  331         aad[23] = 0; /* all bits masked */
  332         /*
  333          * Construct variable-length portion of AAD based
  334          * on whether this is a 4-address frame/QOS frame.
  335          * We always zero-pad to 32 bytes before running it
  336          * through the cipher.
  337          *
  338          * We also fill in the priority bits of the CCM
  339          * initial block as we know whether or not we have
  340          * a QOS frame.
  341          */
  342         if (IS_4ADDRESS(wh)) {
  343                 IEEE80211_ADDR_COPY(aad + 24,
  344                         ((struct ieee80211_frame_addr4 *)wh)->i_addr4);
  345                 if (IS_QOS_DATA(wh)) {
  346                         struct ieee80211_qosframe_addr4 *qwh4 =
  347                                 (struct ieee80211_qosframe_addr4 *) wh;
  348                         aad[30] = qwh4->i_qos[0] & 0x0f;/* just priority bits */
  349                         aad[31] = 0;
  350                         b0[1] = aad[30];
  351                         aad[1] = 22 + IEEE80211_ADDR_LEN + 2;
  352                 } else {
  353                         *(uint16_t *)&aad[30] = 0;
  354                         b0[1] = 0;
  355                         aad[1] = 22 + IEEE80211_ADDR_LEN;
  356                 }
  357         } else {
  358                 if (IS_QOS_DATA(wh)) {
  359                         struct ieee80211_qosframe *qwh =
  360                                 (struct ieee80211_qosframe*) wh;
  361                         aad[24] = qwh->i_qos[0] & 0x0f; /* just priority bits */
  362                         aad[25] = 0;
  363                         b0[1] = aad[24];
  364                         aad[1] = 22 + 2;
  365                 } else {
  366                         *(uint16_t *)&aad[24] = 0;
  367                         b0[1] = 0;
  368                         aad[1] = 22;
  369                 }
  370                 *(uint16_t *)&aad[26] = 0;
  371                 *(uint32_t *)&aad[28] = 0;
  372         }
  373 
  374         /* Start with the first block and AAD */
  375         rijndael_encrypt(ctx, b0, auth);
  376         xor_block(auth, aad, AES_BLOCK_LEN);
  377         rijndael_encrypt(ctx, auth, auth);
  378         xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
  379         rijndael_encrypt(ctx, auth, auth);
  380         b0[0] &= 0x07;
  381         b0[14] = b0[15] = 0;
  382         rijndael_encrypt(ctx, b0, s0);
  383 #undef  IS_QOS_DATA
  384 #undef  IS_4ADDRESS
  385 }
  386 
  387 #define CCMP_ENCRYPT(_i, _b, _b0, _pos, _e, _len) do {  \
  388         /* Authentication */                            \
  389         xor_block(_b, _pos, _len);                      \
  390         rijndael_encrypt(&ctx->cc_aes, _b, _b);         \
  391         /* Encryption, with counter */                  \
  392         _b0[14] = (_i >> 8) & 0xff;                     \
  393         _b0[15] = _i & 0xff;                            \
  394         rijndael_encrypt(&ctx->cc_aes, _b0, _e);        \
  395         xor_block(_pos, _e, _len);                      \
  396 } while (0)
  397 
  398 static int
  399 ccmp_encrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen)
  400 {
  401         struct ccmp_ctx *ctx = key->wk_private;
  402         struct ieee80211_frame *wh;
  403         struct mbuf *m = m0;
  404         int data_len, i, space;
  405         uint8_t aad[2 * AES_BLOCK_LEN], b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN],
  406                 e[AES_BLOCK_LEN], s0[AES_BLOCK_LEN];
  407         uint8_t *pos;
  408 
  409         ctx->cc_ic->ic_stats.is_crypto_ccmp++;
  410 
  411         wh = mtod(m, struct ieee80211_frame *);
  412         data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header);
  413         ccmp_init_blocks(&ctx->cc_aes, wh, key->wk_keytsc,
  414                 data_len, b0, aad, b, s0);
  415 
  416         i = 1;
  417         pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
  418         /* NB: assumes header is entirely in first mbuf */
  419         space = m->m_len - (hdrlen + ccmp.ic_header);
  420         for (;;) {
  421                 if (space > data_len)
  422                         space = data_len;
  423                 /*
  424                  * Do full blocks.
  425                  */
  426                 while (space >= AES_BLOCK_LEN) {
  427                         CCMP_ENCRYPT(i, b, b0, pos, e, AES_BLOCK_LEN);
  428                         pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
  429                         data_len -= AES_BLOCK_LEN;
  430                         i++;
  431                 }
  432                 if (data_len <= 0)              /* no more data */
  433                         break;
  434                 m = m->m_next;
  435                 if (m == NULL) {                /* last buffer */
  436                         if (space != 0) {
  437                                 /*
  438                                  * Short last block.
  439                                  */
  440                                 CCMP_ENCRYPT(i, b, b0, pos, e, space);
  441                         }
  442                         break;
  443                 }
  444                 if (space != 0) {
  445                         uint8_t *pos_next;
  446                         int space_next;
  447                         int len, dl, sp;
  448                         struct mbuf *n;
  449 
  450                         /*
  451                          * Block straddles one or more mbufs, gather data
  452                          * into the block buffer b, apply the cipher, then
  453                          * scatter the results back into the mbuf chain.
  454                          * The buffer will automatically get space bytes
  455                          * of data at offset 0 copied in+out by the
  456                          * CCMP_ENCRYPT request so we must take care of
  457                          * the remaining data.
  458                          */
  459                         n = m;
  460                         dl = data_len;
  461                         sp = space;
  462                         for (;;) {
  463                                 pos_next = mtod(n, uint8_t *);
  464                                 len = min(dl, AES_BLOCK_LEN);
  465                                 space_next = len > sp ? len - sp : 0;
  466                                 if (n->m_len >= space_next) {
  467                                         /*
  468                                          * This mbuf has enough data; just grab
  469                                          * what we need and stop.
  470                                          */
  471                                         xor_block(b+sp, pos_next, space_next);
  472                                         break;
  473                                 }
  474                                 /*
  475                                  * This mbuf's contents are insufficient,
  476                                  * take 'em all and prepare to advance to
  477                                  * the next mbuf.
  478                                  */
  479                                 xor_block(b+sp, pos_next, n->m_len);
  480                                 sp += n->m_len, dl -= n->m_len;
  481                                 n = n->m_next;
  482                                 if (n == NULL)
  483                                         break;
  484                         }
  485 
  486                         CCMP_ENCRYPT(i, b, b0, pos, e, space);
  487 
  488                         /* NB: just like above, but scatter data to mbufs */
  489                         dl = data_len;
  490                         sp = space;
  491                         for (;;) {
  492                                 pos_next = mtod(m, uint8_t *);
  493                                 len = min(dl, AES_BLOCK_LEN);
  494                                 space_next = len > sp ? len - sp : 0;
  495                                 if (m->m_len >= space_next) {
  496                                         xor_block(pos_next, e+sp, space_next);
  497                                         break;
  498                                 }
  499                                 xor_block(pos_next, e+sp, m->m_len);
  500                                 sp += m->m_len, dl -= m->m_len;
  501                                 m = m->m_next;
  502                                 if (m == NULL)
  503                                         goto done;
  504                         }
  505                         /*
  506                          * Do bookkeeping.  m now points to the last mbuf
  507                          * we grabbed data from.  We know we consumed a
  508                          * full block of data as otherwise we'd have hit
  509                          * the end of the mbuf chain, so deduct from data_len.
  510                          * Otherwise advance the block number (i) and setup
  511                          * pos+space to reflect contents of the new mbuf.
  512                          */
  513                         data_len -= AES_BLOCK_LEN;
  514                         i++;
  515                         pos = pos_next + space_next;
  516                         space = m->m_len - space_next;
  517                 } else {
  518                         /*
  519                          * Setup for next buffer.
  520                          */
  521                         pos = mtod(m, uint8_t *);
  522                         space = m->m_len;
  523                 }
  524         }
  525 done:
  526         /* tack on MIC */
  527         xor_block(b, s0, ccmp.ic_trailer);
  528         return m_append(m0, ccmp.ic_trailer, b);
  529 }
  530 #undef CCMP_ENCRYPT
  531 
  532 #define CCMP_DECRYPT(_i, _b, _b0, _pos, _a, _len) do {  \
  533         /* Decrypt, with counter */                     \
  534         _b0[14] = (_i >> 8) & 0xff;                     \
  535         _b0[15] = _i & 0xff;                            \
  536         rijndael_encrypt(&ctx->cc_aes, _b0, _b);        \
  537         xor_block(_pos, _b, _len);                      \
  538         /* Authentication */                            \
  539         xor_block(_a, _pos, _len);                      \
  540         rijndael_encrypt(&ctx->cc_aes, _a, _a);         \
  541 } while (0)
  542 
  543 static int
  544 ccmp_decrypt(struct ieee80211_key *key, u_int64_t pn, struct mbuf *m, int hdrlen)
  545 {
  546         struct ccmp_ctx *ctx = key->wk_private;
  547         struct ieee80211_frame *wh;
  548         uint8_t aad[2 * AES_BLOCK_LEN];
  549         uint8_t b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN], a[AES_BLOCK_LEN];
  550         uint8_t mic[AES_BLOCK_LEN];
  551         size_t data_len;
  552         int i;
  553         uint8_t *pos;
  554         u_int space;
  555 
  556         ctx->cc_ic->ic_stats.is_crypto_ccmp++;
  557 
  558         wh = mtod(m, struct ieee80211_frame *);
  559         data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header + ccmp.ic_trailer);
  560         ccmp_init_blocks(&ctx->cc_aes, wh, pn, data_len, b0, aad, a, b);
  561         m_copydata(m, m->m_pkthdr.len - ccmp.ic_trailer, ccmp.ic_trailer, mic);
  562         xor_block(mic, b, ccmp.ic_trailer);
  563 
  564         i = 1;
  565         pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
  566         space = m->m_len - (hdrlen + ccmp.ic_header);
  567         for (;;) {
  568                 if (space > data_len)
  569                         space = data_len;
  570                 while (space >= AES_BLOCK_LEN) {
  571                         CCMP_DECRYPT(i, b, b0, pos, a, AES_BLOCK_LEN);
  572                         pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
  573                         data_len -= AES_BLOCK_LEN;
  574                         i++;
  575                 }
  576                 if (data_len <= 0)              /* no more data */
  577                         break;
  578                 m = m->m_next;
  579                 if (m == NULL) {                /* last buffer */
  580                         if (space != 0)         /* short last block */
  581                                 CCMP_DECRYPT(i, b, b0, pos, a, space);
  582                         break;
  583                 }
  584                 if (space != 0) {
  585                         uint8_t *pos_next;
  586                         u_int space_next;
  587                         u_int len;
  588 
  589                         /*
  590                          * Block straddles buffers, split references.  We
  591                          * do not handle splits that require >2 buffers
  592                          * since rx'd frames are never badly fragmented
  593                          * because drivers typically recv in clusters.
  594                          */
  595                         pos_next = mtod(m, uint8_t *);
  596                         len = min(data_len, AES_BLOCK_LEN);
  597                         space_next = len > space ? len - space : 0;
  598                         KASSERT(m->m_len >= space_next,
  599                                 ("not enough data in following buffer, "
  600                                 "m_len %u need %u\n", m->m_len, space_next));
  601 
  602                         xor_block(b+space, pos_next, space_next);
  603                         CCMP_DECRYPT(i, b, b0, pos, a, space);
  604                         xor_block(pos_next, b+space, space_next);
  605                         data_len -= len;
  606                         i++;
  607 
  608                         pos = pos_next + space_next;
  609                         space = m->m_len - space_next;
  610                 } else {
  611                         /*
  612                          * Setup for next buffer.
  613                          */
  614                         pos = mtod(m, uint8_t *);
  615                         space = m->m_len;
  616                 }
  617         }
  618         if (memcmp(mic, a, ccmp.ic_trailer) != 0) {
  619                 IEEE80211_DPRINTF(ctx->cc_ic, IEEE80211_MSG_CRYPTO,
  620                         "[%s] AES-CCM decrypt failed; MIC mismatch\n",
  621                         ether_sprintf(wh->i_addr2));
  622                 ctx->cc_ic->ic_stats.is_rx_ccmpmic++;
  623                 return 0;
  624         }
  625         return 1;
  626 }
  627 #undef CCMP_DECRYPT
  628 
  629 /*
  630  * Module glue.
  631  */
  632 IEEE80211_CRYPTO_MODULE(ccmp, 1);

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