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) 2002-2005 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  * 3. The name of the author may not be used to endorse or promote products
   14  *    derived from this software without specific prior written permission.
   15  *
   16  * Alternatively, this software may be distributed under the terms of the
   17  * GNU General Public License ("GPL") version 2 as published by the Free
   18  * Software Foundation.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   21  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   22  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   23  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   24  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   25  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   29  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 #ifdef __FreeBSD__
   34 __FBSDID("$FreeBSD: src/sys/net80211/ieee80211_crypto_ccmp.c,v 1.7 2005/07/11 03:06:23 sam Exp $");
   35 #endif
   36 #ifdef __NetBSD__
   37 __KERNEL_RCSID(0, "$NetBSD: ieee80211_crypto_ccmp.c,v 1.8 2008/12/17 20:51:37 cegger Exp $");
   38 #endif
   39 
   40 /*
   41  * IEEE 802.11i AES-CCMP crypto support.
   42  *
   43  * Part of this module is derived from similar code in the Host
   44  * AP driver. The code is used with the consent of the author and
   45  * it's license is included below.
   46  */
   47 #include <sys/param.h>
   48 #include <sys/systm.h> 
   49 #include <sys/mbuf.h>   
   50 #include <sys/malloc.h>
   51 #include <sys/kernel.h>
   52 
   53 #include <sys/socket.h>
   54 
   55 #include <net/if.h>
   56 #include <net/if_ether.h>
   57 #include <net/if_media.h>
   58 
   59 #include <net80211/ieee80211_var.h>
   60 
   61 #include <crypto/rijndael/rijndael.h>
   62 
   63 #define AES_BLOCK_LEN 16
   64 
   65 struct ccmp_ctx {
   66         struct ieee80211com *cc_ic;     /* for diagnostics */
   67         rijndael_ctx         cc_aes;
   68 };
   69 
   70 static  void *ccmp_attach(struct ieee80211com *, struct ieee80211_key *);
   71 static  void ccmp_detach(struct ieee80211_key *);
   72 static  int ccmp_setkey(struct ieee80211_key *);
   73 static  int ccmp_encap(struct ieee80211_key *k, struct mbuf *, u_int8_t keyid);
   74 static  int ccmp_decap(struct ieee80211_key *, struct mbuf *, int);
   75 static  int ccmp_enmic(struct ieee80211_key *, struct mbuf *, int);
   76 static  int ccmp_demic(struct ieee80211_key *, struct mbuf *, int);
   77 
   78 const struct ieee80211_cipher ieee80211_cipher_ccmp = {
   79         .ic_name        = "AES-CCM",
   80         .ic_cipher      = IEEE80211_CIPHER_AES_CCM,
   81         .ic_header      = IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN +
   82                           IEEE80211_WEP_EXTIVLEN,
   83         .ic_trailer     = IEEE80211_WEP_MICLEN,
   84         .ic_miclen      = 0,
   85         .ic_attach      = ccmp_attach,
   86         .ic_detach      = ccmp_detach,
   87         .ic_setkey      = ccmp_setkey,
   88         .ic_encap       = ccmp_encap,
   89         .ic_decap       = ccmp_decap,
   90         .ic_enmic       = ccmp_enmic,
   91         .ic_demic       = ccmp_demic,
   92 };
   93 
   94 #define ccmp    ieee80211_cipher_ccmp
   95 
   96 static  int ccmp_encrypt(struct ieee80211_key *, struct mbuf *, int hdrlen);
   97 static  int ccmp_decrypt(struct ieee80211_key *, u_int64_t pn,
   98                 struct mbuf *, int hdrlen);
   99 
  100 static void *
  101 ccmp_attach(struct ieee80211com *ic, struct ieee80211_key *k)
  102 {
  103         struct ccmp_ctx *ctx;
  104 
  105         ctx = malloc(sizeof(struct ccmp_ctx),
  106                 M_DEVBUF, M_NOWAIT | M_ZERO);
  107         if (ctx == NULL) {
  108                 ic->ic_stats.is_crypto_nomem++;
  109                 return NULL;
  110         }
  111         ctx->cc_ic = ic;
  112         return ctx;
  113 }
  114 
  115 static void
  116 ccmp_detach(struct ieee80211_key *k)
  117 {
  118         struct ccmp_ctx *ctx = k->wk_private;
  119 
  120         free(ctx, M_DEVBUF);
  121 }
  122 
  123 static int
  124 ccmp_setkey(struct ieee80211_key *k)
  125 {
  126         struct ccmp_ctx *ctx = k->wk_private;
  127 
  128         if (k->wk_keylen != (128/NBBY)) {
  129                 IEEE80211_DPRINTF(ctx->cc_ic, IEEE80211_MSG_CRYPTO,
  130                         "%s: Invalid key length %u, expecting %u\n",
  131                         __func__, k->wk_keylen, 128/NBBY);
  132                 return 0;
  133         }
  134         if (k->wk_flags & IEEE80211_KEY_SWCRYPT)
  135                 rijndael_set_key(&ctx->cc_aes, k->wk_key, k->wk_keylen*NBBY);
  136         return 1;
  137 }
  138 
  139 /*
  140  * Add privacy headers appropriate for the specified key.
  141  */
  142 static int
  143 ccmp_encap(struct ieee80211_key *k, struct mbuf *m, u_int8_t keyid)
  144 {
  145         struct ccmp_ctx *ctx = k->wk_private;
  146         struct ieee80211com *ic = ctx->cc_ic;
  147         u_int8_t *ivp;
  148         int hdrlen;
  149 
  150         hdrlen = ieee80211_hdrspace(ic, mtod(m, void *));
  151 
  152         /*
  153          * Copy down 802.11 header and add the IV, KeyID, and ExtIV.
  154          */
  155         M_PREPEND(m, ccmp.ic_header, M_NOWAIT);
  156         if (m == NULL)
  157                 return 0;
  158         ivp = mtod(m, u_int8_t *);
  159         ovbcopy(ivp + ccmp.ic_header, ivp, hdrlen);
  160         ivp += hdrlen;
  161 
  162         k->wk_keytsc++;         /* XXX wrap at 48 bits */
  163         ivp[0] = k->wk_keytsc >> 0;             /* PN0 */
  164         ivp[1] = k->wk_keytsc >> 8;             /* PN1 */
  165         ivp[2] = 0;                             /* Reserved */
  166         ivp[3] = keyid | IEEE80211_WEP_EXTIV;   /* KeyID | ExtID */
  167         ivp[4] = k->wk_keytsc >> 16;            /* PN2 */
  168         ivp[5] = k->wk_keytsc >> 24;            /* PN3 */
  169         ivp[6] = k->wk_keytsc >> 32;            /* PN4 */
  170         ivp[7] = k->wk_keytsc >> 40;            /* PN5 */
  171 
  172         /*
  173          * Finally, do software encrypt if neeed.
  174          */
  175         if ((k->wk_flags & IEEE80211_KEY_SWCRYPT) &&
  176             !ccmp_encrypt(k, m, hdrlen))
  177                 return 0;
  178 
  179         return 1;
  180 }
  181 
  182 /*
  183  * Add MIC to the frame as needed.
  184  */
  185 static int
  186 ccmp_enmic(struct ieee80211_key *k, struct mbuf *m,
  187     int force)
  188 {
  189 
  190         return 1;
  191 }
  192 
  193 static __inline uint64_t
  194 READ_6(uint8_t b0, uint8_t b1, uint8_t b2, uint8_t b3, uint8_t b4, uint8_t b5)
  195 {
  196         uint32_t iv32 = (b0 << 0) | (b1 << 8) | (b2 << 16) | (b3 << 24);
  197         uint16_t iv16 = (b4 << 0) | (b5 << 8);
  198         return (((uint64_t)iv16) << 32) | iv32;
  199 }
  200 
  201 /*
  202  * Validate and strip privacy headers (and trailer) for a
  203  * received frame. The specified key should be correct but
  204  * is also verified.
  205  */
  206 static int
  207 ccmp_decap(struct ieee80211_key *k, struct mbuf *m, int hdrlen)
  208 {
  209         struct ccmp_ctx *ctx = k->wk_private;
  210         struct ieee80211_frame *wh;
  211         uint8_t *ivp;
  212         uint64_t pn;
  213 
  214         /*
  215          * Header should have extended IV and sequence number;
  216          * verify the former and validate the latter.
  217          */
  218         wh = mtod(m, struct ieee80211_frame *);
  219         ivp = mtod(m, uint8_t *) + hdrlen;
  220         if ((ivp[IEEE80211_WEP_IVLEN] & IEEE80211_WEP_EXTIV) == 0) {
  221                 /*
  222                  * No extended IV; discard frame.
  223                  */
  224                 IEEE80211_DPRINTF(ctx->cc_ic, IEEE80211_MSG_CRYPTO,
  225                         "[%s] Missing ExtIV for AES-CCM cipher\n",
  226                         ether_sprintf(wh->i_addr2));
  227                 ctx->cc_ic->ic_stats.is_rx_ccmpformat++;
  228                 return 0;
  229         }
  230         pn = READ_6(ivp[0], ivp[1], ivp[4], ivp[5], ivp[6], ivp[7]);
  231         if (pn <= k->wk_keyrsc) {
  232                 /*
  233                  * Replay violation.
  234                  */
  235                 ieee80211_notify_replay_failure(ctx->cc_ic, wh, k, pn);
  236                 ctx->cc_ic->ic_stats.is_rx_ccmpreplay++;
  237                 return 0;
  238         }
  239 
  240         /*
  241          * Check if the device handled the decrypt in hardware.
  242          * If so we just strip the header; otherwise we need to
  243          * handle the decrypt in software.  Note that for the
  244          * latter we leave the header in place for use in the
  245          * decryption work.
  246          */
  247         if ((k->wk_flags & IEEE80211_KEY_SWCRYPT) &&
  248             !ccmp_decrypt(k, pn, m, hdrlen))
  249                 return 0;
  250 
  251         /*
  252          * Copy up 802.11 header and strip crypto bits.
  253          */
  254         ovbcopy(mtod(m, void *), mtod(m, u_int8_t *) + ccmp.ic_header, hdrlen);
  255         m_adj(m, ccmp.ic_header);
  256         m_adj(m, -ccmp.ic_trailer);
  257 
  258         /*
  259          * Ok to update rsc now.
  260          */
  261         k->wk_keyrsc = pn;
  262 
  263         return 1;
  264 }
  265 
  266 /*
  267  * Verify and strip MIC from the frame.
  268  */
  269 static int
  270 ccmp_demic(struct ieee80211_key *k, struct mbuf *m,
  271     int force)
  272 {
  273         return 1;
  274 }
  275 
  276 static __inline void
  277 xor_block(uint8_t *b, const uint8_t *a, size_t len)
  278 {
  279         int i;
  280         for (i = 0; i < len; i++)
  281                 b[i] ^= a[i];
  282 }
  283 
  284 /*
  285  * Host AP crypt: host-based CCMP encryption implementation for Host AP driver
  286  *
  287  * Copyright (c) 2003-2004, Jouni Malinen <jkmaline@cc.hut.fi>
  288  *
  289  * This program is free software; you can redistribute it and/or modify
  290  * it under the terms of the GNU General Public License version 2 as
  291  * published by the Free Software Foundation. See README and COPYING for
  292  * more details.
  293  *
  294  * Alternatively, this software may be distributed under the terms of BSD
  295  * license.
  296  */
  297 
  298 static void
  299 ccmp_init_blocks(rijndael_ctx *ctx, struct ieee80211_frame *wh,
  300         u_int64_t pn, size_t dlen,
  301         uint8_t b0[AES_BLOCK_LEN], uint8_t aad[2 * AES_BLOCK_LEN],
  302         uint8_t auth[AES_BLOCK_LEN], uint8_t s0[AES_BLOCK_LEN])
  303 {
  304 #define IS_4ADDRESS(wh) \
  305         ((wh->i_fc[1] & IEEE80211_FC1_DIR_MASK) == IEEE80211_FC1_DIR_DSTODS)
  306 #define IS_QOS_DATA(wh) IEEE80211_QOS_HAS_SEQ(wh)
  307 
  308         /* CCM Initial Block:
  309          * Flag (Include authentication header, M=3 (8-octet MIC),
  310          *       L=1 (2-octet Dlen))
  311          * Nonce: 0x00 | A2 | PN
  312          * Dlen */
  313         b0[0] = 0x59;
  314         /* NB: b0[1] set below */
  315         IEEE80211_ADDR_COPY(b0 + 2, wh->i_addr2);
  316         b0[8] = pn >> 40;
  317         b0[9] = pn >> 32;
  318         b0[10] = pn >> 24;
  319         b0[11] = pn >> 16;
  320         b0[12] = pn >> 8;
  321         b0[13] = pn >> 0;
  322         b0[14] = (dlen >> 8) & 0xff;
  323         b0[15] = dlen & 0xff;
  324 
  325         /* AAD:
  326          * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
  327          * A1 | A2 | A3
  328          * SC with bits 4..15 (seq#) masked to zero
  329          * A4 (if present)
  330          * QC (if present)
  331          */
  332         aad[0] = 0;     /* AAD length >> 8 */
  333         /* NB: aad[1] set below */
  334         aad[2] = wh->i_fc[0] & 0x8f;    /* XXX magic #s */
  335         aad[3] = wh->i_fc[1] & 0xc7;    /* XXX magic #s */
  336         /* NB: we know 3 addresses are contiguous */
  337         memcpy(aad + 4, wh->i_addr1, 3 * IEEE80211_ADDR_LEN);
  338         aad[22] = wh->i_seq[0] & IEEE80211_SEQ_FRAG_MASK;
  339         aad[23] = 0; /* all bits masked */
  340         /*
  341          * Construct variable-length portion of AAD based
  342          * on whether this is a 4-address frame/QOS frame.
  343          * We always zero-pad to 32 bytes before running it
  344          * through the cipher.
  345          *
  346          * We also fill in the priority bits of the CCM
  347          * initial block as we know whether or not we have
  348          * a QOS frame.
  349          */
  350         if (IS_4ADDRESS(wh)) {
  351                 IEEE80211_ADDR_COPY(aad + 24,
  352                         ((struct ieee80211_frame_addr4 *)wh)->i_addr4);
  353                 if (IS_QOS_DATA(wh)) {
  354                         struct ieee80211_qosframe_addr4 *qwh4 =
  355                                 (struct ieee80211_qosframe_addr4 *) wh;
  356                         aad[30] = qwh4->i_qos[0] & 0x0f;/* just priority bits */
  357                         aad[31] = 0;
  358                         b0[1] = aad[30];
  359                         aad[1] = 22 + IEEE80211_ADDR_LEN + 2;
  360                 } else {
  361                         *(u_int16_t *)&aad[30] = 0;
  362                         b0[1] = 0;
  363                         aad[1] = 22 + IEEE80211_ADDR_LEN;
  364                 }
  365         } else {
  366                 if (IS_QOS_DATA(wh)) {
  367                         struct ieee80211_qosframe *qwh =
  368                                 (struct ieee80211_qosframe*) wh;
  369                         aad[24] = qwh->i_qos[0] & 0x0f; /* just priority bits */
  370                         aad[25] = 0;
  371                         b0[1] = aad[24];
  372                         aad[1] = 22 + 2;
  373                 } else {
  374                         *(u_int16_t *)&aad[24] = 0;
  375                         b0[1] = 0;
  376                         aad[1] = 22;
  377                 }
  378                 *(u_int16_t *)&aad[26] = 0;
  379                 *(u_int32_t *)&aad[28] = 0;
  380         }
  381 
  382         /* Start with the first block and AAD */
  383         rijndael_encrypt(ctx, b0, auth);
  384         xor_block(auth, aad, AES_BLOCK_LEN);
  385         rijndael_encrypt(ctx, auth, auth);
  386         xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
  387         rijndael_encrypt(ctx, auth, auth);
  388         b0[0] &= 0x07;
  389         b0[14] = b0[15] = 0;
  390         rijndael_encrypt(ctx, b0, s0);
  391 #undef  IS_QOS_DATA
  392 #undef  IS_4ADDRESS
  393 }
  394 
  395 #define CCMP_ENCRYPT(_i, _b, _b0, _pos, _e, _len) do {  \
  396         /* Authentication */                            \
  397         xor_block(_b, _pos, _len);                      \
  398         rijndael_encrypt(&ctx->cc_aes, _b, _b);         \
  399         /* Encryption, with counter */                  \
  400         _b0[14] = (_i >> 8) & 0xff;                     \
  401         _b0[15] = _i & 0xff;                            \
  402         rijndael_encrypt(&ctx->cc_aes, _b0, _e);        \
  403         xor_block(_pos, _e, _len);                      \
  404 } while (0)
  405 
  406 static int
  407 ccmp_encrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen)
  408 {
  409         struct ccmp_ctx *ctx = key->wk_private;
  410         struct ieee80211_frame *wh;
  411         struct mbuf *m = m0;
  412         int data_len, i, space;
  413         uint8_t aad[2 * AES_BLOCK_LEN], b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN],
  414                 e[AES_BLOCK_LEN], s0[AES_BLOCK_LEN];
  415         uint8_t *pos;
  416 
  417         ctx->cc_ic->ic_stats.is_crypto_ccmp++;
  418 
  419         wh = mtod(m, struct ieee80211_frame *);
  420         data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header);
  421         ccmp_init_blocks(&ctx->cc_aes, wh, key->wk_keytsc,
  422                 data_len, b0, aad, b, s0);
  423 
  424         i = 1;
  425         pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
  426         /* NB: assumes header is entirely in first mbuf */
  427         space = m->m_len - (hdrlen + ccmp.ic_header);
  428         for (;;) {
  429                 if (space > data_len)
  430                         space = data_len;
  431                 /*
  432                  * Do full blocks.
  433                  */
  434                 while (space >= AES_BLOCK_LEN) {
  435                         CCMP_ENCRYPT(i, b, b0, pos, e, AES_BLOCK_LEN);
  436                         pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
  437                         data_len -= AES_BLOCK_LEN;
  438                         i++;
  439                 }
  440                 if (data_len <= 0)              /* no more data */
  441                         break;
  442                 m = m->m_next;
  443                 if (m == NULL) {                /* last buffer */
  444                         if (space != 0) {
  445                                 /*
  446                                  * Short last block.
  447                                  */
  448                                 CCMP_ENCRYPT(i, b, b0, pos, e, space);
  449                         }
  450                         break;
  451                 }
  452                 if (space != 0) {
  453                         uint8_t *pos_next;
  454                         int space_next;
  455                         int len, dl, sp;
  456                         struct mbuf *n;
  457 
  458                         /*
  459                          * Block straddles one or more mbufs, gather data
  460                          * into the block buffer b, apply the cipher, then
  461                          * scatter the results back into the mbuf chain.
  462                          * The buffer will automatically get space bytes
  463                          * of data at offset 0 copied in+out by the
  464                          * CCMP_ENCRYPT request so we must take care of
  465                          * the remaining data.
  466                          */
  467                         n = m;
  468                         dl = data_len;
  469                         sp = space;
  470                         for (;;) {
  471                                 pos_next = mtod(n, uint8_t *);
  472                                 len = min(dl, AES_BLOCK_LEN);
  473                                 space_next = len > sp ? len - sp : 0;
  474                                 if (n->m_len >= space_next) {
  475                                         /*
  476                                          * This mbuf has enough data; just grab
  477                                          * what we need and stop.
  478                                          */
  479                                         xor_block(b+sp, pos_next, space_next);
  480                                         break;
  481                                 }
  482                                 /*
  483                                  * This mbuf's contents are insufficient,
  484                                  * take 'em all and prepare to advance to
  485                                  * the next mbuf.
  486                                  */
  487                                 xor_block(b+sp, pos_next, n->m_len);
  488                                 sp += n->m_len, dl -= n->m_len;
  489                                 n = n->m_next;
  490                                 if (n == NULL)
  491                                         break;
  492                         }
  493 
  494                         CCMP_ENCRYPT(i, b, b0, pos, e, space);
  495 
  496                         /* NB: just like above, but scatter data to mbufs */
  497                         dl = data_len;
  498                         sp = space;
  499                         for (;;) {
  500                                 pos_next = mtod(m, uint8_t *);
  501                                 len = min(dl, AES_BLOCK_LEN);
  502                                 space_next = len > sp ? len - sp : 0;
  503                                 if (m->m_len >= space_next) {
  504                                         xor_block(pos_next, e+sp, space_next);
  505                                         break;
  506                                 }
  507                                 xor_block(pos_next, e+sp, m->m_len);
  508                                 sp += m->m_len, dl -= m->m_len;
  509                                 m = m->m_next;
  510                                 if (m == NULL)
  511                                         goto done;
  512                         }
  513                         /*
  514                          * Do bookkeeping.  m now points to the last mbuf
  515                          * we grabbed data from.  We know we consumed a
  516                          * full block of data as otherwise we'd have hit
  517                          * the end of the mbuf chain, so deduct from data_len.
  518                          * Otherwise advance the block number (i) and setup
  519                          * pos+space to reflect contents of the new mbuf.
  520                          */
  521                         data_len -= AES_BLOCK_LEN;
  522                         i++;
  523                         pos = pos_next + space_next;
  524                         space = m->m_len - space_next;
  525                 } else {
  526                         /*
  527                          * Setup for next buffer.
  528                          */
  529                         pos = mtod(m, uint8_t *);
  530                         space = m->m_len;
  531                 }
  532         }
  533 done:
  534         /* tack on MIC */
  535         xor_block(b, s0, ccmp.ic_trailer);
  536         return m_append(m0, ccmp.ic_trailer, b);
  537 }
  538 #undef CCMP_ENCRYPT
  539 
  540 #define CCMP_DECRYPT(_i, _b, _b0, _pos, _a, _len) do {  \
  541         /* Decrypt, with counter */                     \
  542         _b0[14] = (_i >> 8) & 0xff;                     \
  543         _b0[15] = _i & 0xff;                            \
  544         rijndael_encrypt(&ctx->cc_aes, _b0, _b);        \
  545         xor_block(_pos, _b, _len);                      \
  546         /* Authentication */                            \
  547         xor_block(_a, _pos, _len);                      \
  548         rijndael_encrypt(&ctx->cc_aes, _a, _a);         \
  549 } while (0)
  550 
  551 static int
  552 ccmp_decrypt(struct ieee80211_key *key, u_int64_t pn, struct mbuf *m, int hdrlen)
  553 {
  554         struct ccmp_ctx *ctx = key->wk_private;
  555         struct ieee80211_frame *wh;
  556         uint8_t aad[2 * AES_BLOCK_LEN];
  557         uint8_t b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN], a[AES_BLOCK_LEN];
  558         uint8_t mic[AES_BLOCK_LEN];
  559         size_t data_len;
  560         int i;
  561         uint8_t *pos;
  562         u_int space;
  563 
  564         ctx->cc_ic->ic_stats.is_crypto_ccmp++;
  565 
  566         wh = mtod(m, struct ieee80211_frame *);
  567         data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header + ccmp.ic_trailer);
  568         ccmp_init_blocks(&ctx->cc_aes, wh, pn, data_len, b0, aad, a, b);
  569         m_copydata(m, m->m_pkthdr.len - ccmp.ic_trailer, ccmp.ic_trailer, mic);
  570         xor_block(mic, b, ccmp.ic_trailer);
  571 
  572         i = 1;
  573         pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
  574         space = m->m_len - (hdrlen + ccmp.ic_header);
  575         for (;;) {
  576                 if (space > data_len)
  577                         space = data_len;
  578                 while (space >= AES_BLOCK_LEN) {
  579                         CCMP_DECRYPT(i, b, b0, pos, a, AES_BLOCK_LEN);
  580                         pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
  581                         data_len -= AES_BLOCK_LEN;
  582                         i++;
  583                 }
  584                 if (data_len <= 0)              /* no more data */
  585                         break;
  586                 m = m->m_next;
  587                 if (m == NULL) {                /* last buffer */
  588                         if (space != 0)         /* short last block */
  589                                 CCMP_DECRYPT(i, b, b0, pos, a, space);
  590                         break;
  591                 }
  592                 if (space != 0) {
  593                         uint8_t *pos_next;
  594                         u_int space_next;
  595                         u_int len;
  596 
  597                         /*
  598                          * Block straddles buffers, split references.  We
  599                          * do not handle splits that require >2 buffers
  600                          * since rx'd frames are never badly fragmented
  601                          * because drivers typically recv in clusters.
  602                          */
  603                         pos_next = mtod(m, uint8_t *);
  604                         len = min(data_len, AES_BLOCK_LEN);
  605                         space_next = len > space ? len - space : 0;
  606                         IASSERT(m->m_len >= space_next,
  607                                 ("not enough data in following buffer, "
  608                                 "m_len %u need %u\n", m->m_len, space_next));
  609 
  610                         xor_block(b+space, pos_next, space_next);
  611                         CCMP_DECRYPT(i, b, b0, pos, a, space);
  612                         xor_block(pos_next, b+space, space_next);
  613                         data_len -= len;
  614                         i++;
  615 
  616                         pos = pos_next + space_next;
  617                         space = m->m_len - space_next;
  618                 } else {
  619                         /*
  620                          * Setup for next buffer.
  621                          */
  622                         pos = mtod(m, uint8_t *);
  623                         space = m->m_len;
  624                 }
  625         }
  626         if (memcmp(mic, a, ccmp.ic_trailer) != 0) {
  627                 IEEE80211_DPRINTF(ctx->cc_ic, IEEE80211_MSG_CRYPTO,
  628                         "[%s] AES-CCM decrypt failed; MIC mismatch\n",
  629                         ether_sprintf(wh->i_addr2));
  630                 ctx->cc_ic->ic_stats.is_rx_ccmpmic++;
  631                 return 0;
  632         }
  633         return 1;
  634 }
  635 #undef CCMP_DECRYPT
  636 
  637 IEEE80211_CRYPTO_SETUP(ccmp_register)
  638 {
  639         ieee80211_crypto_register(&ccmp);
  640 }

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