The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/net80211/ieee80211_crypto.c

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    1 /*-
    2  * Copyright (c) 2001 Atsushi Onoe
    3  * Copyright (c) 2002-2007 Sam Leffler, Errno Consulting
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD$");
   29 
   30 /*
   31  * IEEE 802.11 generic crypto support.
   32  */
   33 #include <sys/param.h>
   34 #include <sys/mbuf.h>   
   35 
   36 #include <sys/socket.h>
   37 
   38 #include <net/if.h>
   39 #include <net/if_media.h>
   40 #include <net/ethernet.h>               /* XXX ETHER_HDR_LEN */
   41 
   42 #include <net80211/ieee80211_var.h>
   43 
   44 /*
   45  * Table of registered cipher modules.
   46  */
   47 static  const struct ieee80211_cipher *ciphers[IEEE80211_CIPHER_MAX];
   48 
   49 static  int _ieee80211_crypto_delkey(struct ieee80211com *,
   50                 struct ieee80211_key *);
   51 
   52 /*
   53  * Default "null" key management routines.
   54  */
   55 static int
   56 null_key_alloc(struct ieee80211com *ic, const struct ieee80211_key *k,
   57         ieee80211_keyix *keyix, ieee80211_keyix *rxkeyix)
   58 {
   59         if (!(&ic->ic_nw_keys[0] <= k &&
   60              k < &ic->ic_nw_keys[IEEE80211_WEP_NKID])) {
   61                 /*
   62                  * Not in the global key table, the driver should handle this
   63                  * by allocating a slot in the h/w key table/cache.  In
   64                  * lieu of that return key slot 0 for any unicast key
   65                  * request.  We disallow the request if this is a group key.
   66                  * This default policy does the right thing for legacy hardware
   67                  * with a 4 key table.  It also handles devices that pass
   68                  * packets through untouched when marked with the WEP bit
   69                  * and key index 0.
   70                  */
   71                 if (k->wk_flags & IEEE80211_KEY_GROUP)
   72                         return 0;
   73                 *keyix = 0;     /* NB: use key index 0 for ucast key */
   74         } else {
   75                 *keyix = k - ic->ic_nw_keys;
   76         }
   77         *rxkeyix = IEEE80211_KEYIX_NONE;        /* XXX maybe *keyix? */
   78         return 1;
   79 }
   80 static int
   81 null_key_delete(struct ieee80211com *ic, const struct ieee80211_key *k)
   82 {
   83         return 1;
   84 }
   85 static  int
   86 null_key_set(struct ieee80211com *ic, const struct ieee80211_key *k,
   87         const uint8_t mac[IEEE80211_ADDR_LEN])
   88 {
   89         return 1;
   90 }
   91 static void null_key_update(struct ieee80211com *ic) {}
   92 
   93 /*
   94  * Write-arounds for common operations.
   95  */
   96 static __inline void
   97 cipher_detach(struct ieee80211_key *key)
   98 {
   99         key->wk_cipher->ic_detach(key);
  100 }
  101 
  102 static __inline void *
  103 cipher_attach(struct ieee80211com *ic, struct ieee80211_key *key)
  104 {
  105         return key->wk_cipher->ic_attach(ic, key);
  106 }
  107 
  108 /* 
  109  * Wrappers for driver key management methods.
  110  */
  111 static __inline int
  112 dev_key_alloc(struct ieee80211com *ic,
  113         const struct ieee80211_key *key,
  114         ieee80211_keyix *keyix, ieee80211_keyix *rxkeyix)
  115 {
  116         return ic->ic_crypto.cs_key_alloc(ic, key, keyix, rxkeyix);
  117 }
  118 
  119 static __inline int
  120 dev_key_delete(struct ieee80211com *ic,
  121         const struct ieee80211_key *key)
  122 {
  123         return ic->ic_crypto.cs_key_delete(ic, key);
  124 }
  125 
  126 static __inline int
  127 dev_key_set(struct ieee80211com *ic, const struct ieee80211_key *key,
  128         const uint8_t mac[IEEE80211_ADDR_LEN])
  129 {
  130         return ic->ic_crypto.cs_key_set(ic, key, mac);
  131 }
  132 
  133 /*
  134  * Setup crypto support.
  135  */
  136 void
  137 ieee80211_crypto_attach(struct ieee80211com *ic)
  138 {
  139         struct ieee80211_crypto_state *cs = &ic->ic_crypto;
  140         int i;
  141 
  142         /* NB: we assume everything is pre-zero'd */
  143         cs->cs_def_txkey = IEEE80211_KEYIX_NONE;
  144         cs->cs_max_keyix = IEEE80211_WEP_NKID;
  145         ciphers[IEEE80211_CIPHER_NONE] = &ieee80211_cipher_none;
  146         for (i = 0; i < IEEE80211_WEP_NKID; i++)
  147                 ieee80211_crypto_resetkey(ic, &cs->cs_nw_keys[i],
  148                         IEEE80211_KEYIX_NONE);
  149         /*
  150          * Initialize the driver key support routines to noop entries.
  151          * This is useful especially for the cipher test modules.
  152          */
  153         cs->cs_key_alloc = null_key_alloc;
  154         cs->cs_key_set = null_key_set;
  155         cs->cs_key_delete = null_key_delete;
  156         cs->cs_key_update_begin = null_key_update;
  157         cs->cs_key_update_end = null_key_update;
  158 }
  159 
  160 /*
  161  * Teardown crypto support.
  162  */
  163 void
  164 ieee80211_crypto_detach(struct ieee80211com *ic)
  165 {
  166         ieee80211_crypto_delglobalkeys(ic);
  167 }
  168 
  169 /*
  170  * Register a crypto cipher module.
  171  */
  172 void
  173 ieee80211_crypto_register(const struct ieee80211_cipher *cip)
  174 {
  175         if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
  176                 printf("%s: cipher %s has an invalid cipher index %u\n",
  177                         __func__, cip->ic_name, cip->ic_cipher);
  178                 return;
  179         }
  180         if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
  181                 printf("%s: cipher %s registered with a different template\n",
  182                         __func__, cip->ic_name);
  183                 return;
  184         }
  185         ciphers[cip->ic_cipher] = cip;
  186 }
  187 
  188 /*
  189  * Unregister a crypto cipher module.
  190  */
  191 void
  192 ieee80211_crypto_unregister(const struct ieee80211_cipher *cip)
  193 {
  194         if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
  195                 printf("%s: cipher %s has an invalid cipher index %u\n",
  196                         __func__, cip->ic_name, cip->ic_cipher);
  197                 return;
  198         }
  199         if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
  200                 printf("%s: cipher %s registered with a different template\n",
  201                         __func__, cip->ic_name);
  202                 return;
  203         }
  204         /* NB: don't complain about not being registered */
  205         /* XXX disallow if references */
  206         ciphers[cip->ic_cipher] = NULL;
  207 }
  208 
  209 int
  210 ieee80211_crypto_available(u_int cipher)
  211 {
  212         return cipher < IEEE80211_CIPHER_MAX && ciphers[cipher] != NULL;
  213 }
  214 
  215 /* XXX well-known names! */
  216 static const char *cipher_modnames[] = {
  217         "wlan_wep",     /* IEEE80211_CIPHER_WEP */
  218         "wlan_tkip",    /* IEEE80211_CIPHER_TKIP */
  219         "wlan_aes_ocb", /* IEEE80211_CIPHER_AES_OCB */
  220         "wlan_ccmp",    /* IEEE80211_CIPHER_AES_CCM */
  221         "wlan_ckip",    /* IEEE80211_CIPHER_CKIP */
  222 };
  223 
  224 /*
  225  * Establish a relationship between the specified key and cipher
  226  * and, if necessary, allocate a hardware index from the driver.
  227  * Note that when a fixed key index is required it must be specified
  228  * and we blindly assign it w/o consulting the driver (XXX).
  229  *
  230  * This must be the first call applied to a key; all the other key
  231  * routines assume wk_cipher is setup.
  232  *
  233  * Locking must be handled by the caller using:
  234  *      ieee80211_key_update_begin(ic);
  235  *      ieee80211_key_update_end(ic);
  236  */
  237 int
  238 ieee80211_crypto_newkey(struct ieee80211com *ic,
  239         int cipher, int flags, struct ieee80211_key *key)
  240 {
  241 #define N(a)    (sizeof(a) / sizeof(a[0]))
  242         const struct ieee80211_cipher *cip;
  243         ieee80211_keyix keyix, rxkeyix;
  244         void *keyctx;
  245         int oflags;
  246 
  247         /*
  248          * Validate cipher and set reference to cipher routines.
  249          */
  250         if (cipher >= IEEE80211_CIPHER_MAX) {
  251                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  252                         "%s: invalid cipher %u\n", __func__, cipher);
  253                 ic->ic_stats.is_crypto_badcipher++;
  254                 return 0;
  255         }
  256         cip = ciphers[cipher];
  257         if (cip == NULL) {
  258                 /*
  259                  * Auto-load cipher module if we have a well-known name
  260                  * for it.  It might be better to use string names rather
  261                  * than numbers and craft a module name based on the cipher
  262                  * name; e.g. wlan_cipher_<cipher-name>.
  263                  */
  264                 if (cipher < N(cipher_modnames)) {
  265                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  266                                 "%s: unregistered cipher %u, load module %s\n",
  267                                 __func__, cipher, cipher_modnames[cipher]);
  268                         ieee80211_load_module(cipher_modnames[cipher]);
  269                         /*
  270                          * If cipher module loaded it should immediately
  271                          * call ieee80211_crypto_register which will fill
  272                          * in the entry in the ciphers array.
  273                          */
  274                         cip = ciphers[cipher];
  275                 }
  276                 if (cip == NULL) {
  277                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  278                                 "%s: unable to load cipher %u, module %s\n",
  279                                 __func__, cipher,
  280                                 cipher < N(cipher_modnames) ?
  281                                         cipher_modnames[cipher] : "<unknown>");
  282                         ic->ic_stats.is_crypto_nocipher++;
  283                         return 0;
  284                 }
  285         }
  286 
  287         oflags = key->wk_flags;
  288         flags &= IEEE80211_KEY_COMMON;
  289         /*
  290          * If the hardware does not support the cipher then
  291          * fallback to a host-based implementation.
  292          */
  293         if ((ic->ic_caps & (1<<cipher)) == 0) {
  294                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  295                     "%s: no h/w support for cipher %s, falling back to s/w\n",
  296                     __func__, cip->ic_name);
  297                 flags |= IEEE80211_KEY_SWCRYPT;
  298         }
  299         /*
  300          * Hardware TKIP with software MIC is an important
  301          * combination; we handle it by flagging each key,
  302          * the cipher modules honor it.
  303          */
  304         if (cipher == IEEE80211_CIPHER_TKIP &&
  305             (ic->ic_caps & IEEE80211_C_TKIPMIC) == 0) {
  306                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  307                     "%s: no h/w support for TKIP MIC, falling back to s/w\n",
  308                     __func__);
  309                 flags |= IEEE80211_KEY_SWMIC;
  310         }
  311 
  312         /*
  313          * Bind cipher to key instance.  Note we do this
  314          * after checking the device capabilities so the
  315          * cipher module can optimize space usage based on
  316          * whether or not it needs to do the cipher work.
  317          */
  318         if (key->wk_cipher != cip || key->wk_flags != flags) {
  319 again:
  320                 /*
  321                  * Fillin the flags so cipher modules can see s/w
  322                  * crypto requirements and potentially allocate
  323                  * different state and/or attach different method
  324                  * pointers.
  325                  *
  326                  * XXX this is not right when s/w crypto fallback
  327                  *     fails and we try to restore previous state.
  328                  */
  329                 key->wk_flags = flags;
  330                 keyctx = cip->ic_attach(ic, key);
  331                 if (keyctx == NULL) {
  332                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  333                                 "%s: unable to attach cipher %s\n",
  334                                 __func__, cip->ic_name);
  335                         key->wk_flags = oflags; /* restore old flags */
  336                         ic->ic_stats.is_crypto_attachfail++;
  337                         return 0;
  338                 }
  339                 cipher_detach(key);
  340                 key->wk_cipher = cip;           /* XXX refcnt? */
  341                 key->wk_private = keyctx;
  342         }
  343         /*
  344          * Commit to requested usage so driver can see the flags.
  345          */
  346         key->wk_flags = flags;
  347 
  348         /*
  349          * Ask the driver for a key index if we don't have one.
  350          * Note that entries in the global key table always have
  351          * an index; this means it's safe to call this routine
  352          * for these entries just to setup the reference to the
  353          * cipher template.  Note also that when using software
  354          * crypto we also call the driver to give us a key index.
  355          */
  356         if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
  357                 if (!dev_key_alloc(ic, key, &keyix, &rxkeyix)) {
  358                         /*
  359                          * Driver has no room; fallback to doing crypto
  360                          * in the host.  We change the flags and start the
  361                          * procedure over.  If we get back here then there's
  362                          * no hope and we bail.  Note that this can leave
  363                          * the key in a inconsistent state if the caller
  364                          * continues to use it.
  365                          */
  366                         if ((key->wk_flags & IEEE80211_KEY_SWCRYPT) == 0) {
  367                                 ic->ic_stats.is_crypto_swfallback++;
  368                                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  369                                     "%s: no h/w resources for cipher %s, "
  370                                     "falling back to s/w\n", __func__,
  371                                     cip->ic_name);
  372                                 oflags = key->wk_flags;
  373                                 flags |= IEEE80211_KEY_SWCRYPT;
  374                                 if (cipher == IEEE80211_CIPHER_TKIP)
  375                                         flags |= IEEE80211_KEY_SWMIC;
  376                                 goto again;
  377                         }
  378                         ic->ic_stats.is_crypto_keyfail++;
  379                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  380                             "%s: unable to setup cipher %s\n",
  381                             __func__, cip->ic_name);
  382                         return 0;
  383                 }
  384                 key->wk_keyix = keyix;
  385                 key->wk_rxkeyix = rxkeyix;
  386         }
  387         return 1;
  388 #undef N
  389 }
  390 
  391 /*
  392  * Remove the key (no locking, for internal use).
  393  */
  394 static int
  395 _ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
  396 {
  397         ieee80211_keyix keyix;
  398 
  399         KASSERT(key->wk_cipher != NULL, ("No cipher!"));
  400 
  401         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  402             "%s: %s keyix %u flags 0x%x rsc %ju tsc %ju len %u\n",
  403             __func__, key->wk_cipher->ic_name,
  404             key->wk_keyix, key->wk_flags,
  405             key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);
  406 
  407         keyix = key->wk_keyix;
  408         if (keyix != IEEE80211_KEYIX_NONE) {
  409                 /*
  410                  * Remove hardware entry.
  411                  */
  412                 /* XXX key cache */
  413                 if (!dev_key_delete(ic, key)) {
  414                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  415                             "%s: driver did not delete key index %u\n",
  416                             __func__, keyix);
  417                         ic->ic_stats.is_crypto_delkey++;
  418                         /* XXX recovery? */
  419                 }
  420         }
  421         cipher_detach(key);
  422         memset(key, 0, sizeof(*key));
  423         ieee80211_crypto_resetkey(ic, key, IEEE80211_KEYIX_NONE);
  424         return 1;
  425 }
  426 
  427 /*
  428  * Remove the specified key.
  429  */
  430 int
  431 ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
  432 {
  433         int status;
  434 
  435         ieee80211_key_update_begin(ic);
  436         status = _ieee80211_crypto_delkey(ic, key);
  437         ieee80211_key_update_end(ic);
  438         return status;
  439 }
  440 
  441 /*
  442  * Clear the global key table.
  443  */
  444 void
  445 ieee80211_crypto_delglobalkeys(struct ieee80211com *ic)
  446 {
  447         int i;
  448 
  449         ieee80211_key_update_begin(ic);
  450         for (i = 0; i < IEEE80211_WEP_NKID; i++)
  451                 (void) _ieee80211_crypto_delkey(ic, &ic->ic_nw_keys[i]);
  452         ieee80211_key_update_end(ic);
  453 }
  454 
  455 /*
  456  * Set the contents of the specified key.
  457  *
  458  * Locking must be handled by the caller using:
  459  *      ieee80211_key_update_begin(ic);
  460  *      ieee80211_key_update_end(ic);
  461  */
  462 int
  463 ieee80211_crypto_setkey(struct ieee80211com *ic, struct ieee80211_key *key,
  464                 const uint8_t macaddr[IEEE80211_ADDR_LEN])
  465 {
  466         const struct ieee80211_cipher *cip = key->wk_cipher;
  467 
  468         KASSERT(cip != NULL, ("No cipher!"));
  469 
  470         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  471             "%s: %s keyix %u flags 0x%x mac %s rsc %ju tsc %ju len %u\n",
  472             __func__, cip->ic_name, key->wk_keyix,
  473             key->wk_flags, ether_sprintf(macaddr),
  474             key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);
  475 
  476         /*
  477          * Give cipher a chance to validate key contents.
  478          * XXX should happen before modifying state.
  479          */
  480         if (!cip->ic_setkey(key)) {
  481                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  482                     "%s: cipher %s rejected key index %u len %u flags 0x%x\n",
  483                     __func__, cip->ic_name, key->wk_keyix,
  484                     key->wk_keylen, key->wk_flags);
  485                 ic->ic_stats.is_crypto_setkey_cipher++;
  486                 return 0;
  487         }
  488         if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
  489                 /* XXX nothing allocated, should not happen */
  490                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  491                     "%s: no key index; should not happen!\n", __func__);
  492                 ic->ic_stats.is_crypto_setkey_nokey++;
  493                 return 0;
  494         }
  495         return dev_key_set(ic, key, macaddr);
  496 }
  497 
  498 /*
  499  * Add privacy headers appropriate for the specified key.
  500  */
  501 struct ieee80211_key *
  502 ieee80211_crypto_encap(struct ieee80211com *ic,
  503         struct ieee80211_node *ni, struct mbuf *m)
  504 {
  505         struct ieee80211_key *k;
  506         struct ieee80211_frame *wh;
  507         const struct ieee80211_cipher *cip;
  508         uint8_t keyid;
  509 
  510         /*
  511          * Multicast traffic always uses the multicast key.
  512          * Otherwise if a unicast key is set we use that and
  513          * it is always key index 0.  When no unicast key is
  514          * set we fall back to the default transmit key.
  515          */
  516         wh = mtod(m, struct ieee80211_frame *);
  517         if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
  518             IEEE80211_KEY_UNDEFINED(&ni->ni_ucastkey)) {
  519                 if (ic->ic_def_txkey == IEEE80211_KEYIX_NONE) {
  520                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  521                             "[%s] no default transmit key (%s) deftxkey %u\n",
  522                             ether_sprintf(wh->i_addr1), __func__,
  523                             ic->ic_def_txkey);
  524                         ic->ic_stats.is_tx_nodefkey++;
  525                         return NULL;
  526                 }
  527                 keyid = ic->ic_def_txkey;
  528                 k = &ic->ic_nw_keys[ic->ic_def_txkey];
  529         } else {
  530                 keyid = 0;
  531                 k = &ni->ni_ucastkey;
  532         }
  533         cip = k->wk_cipher;
  534         return (cip->ic_encap(k, m, keyid<<6) ? k : NULL);
  535 }
  536 
  537 /*
  538  * Validate and strip privacy headers (and trailer) for a
  539  * received frame that has the WEP/Privacy bit set.
  540  */
  541 struct ieee80211_key *
  542 ieee80211_crypto_decap(struct ieee80211com *ic,
  543         struct ieee80211_node *ni, struct mbuf *m, int hdrlen)
  544 {
  545 #define IEEE80211_WEP_HDRLEN    (IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN)
  546 #define IEEE80211_WEP_MINLEN \
  547         (sizeof(struct ieee80211_frame) + \
  548         IEEE80211_WEP_HDRLEN + IEEE80211_WEP_CRCLEN)
  549         struct ieee80211_key *k;
  550         struct ieee80211_frame *wh;
  551         const struct ieee80211_cipher *cip;
  552         const uint8_t *ivp;
  553         uint8_t keyid;
  554 
  555         /* NB: this minimum size data frame could be bigger */
  556         if (m->m_pkthdr.len < IEEE80211_WEP_MINLEN) {
  557                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_ANY,
  558                         "%s: WEP data frame too short, len %u\n",
  559                         __func__, m->m_pkthdr.len);
  560                 ic->ic_stats.is_rx_tooshort++;  /* XXX need unique stat? */
  561                 return NULL;
  562         }
  563 
  564         /*
  565          * Locate the key. If unicast and there is no unicast
  566          * key then we fall back to the key id in the header.
  567          * This assumes unicast keys are only configured when
  568          * the key id in the header is meaningless (typically 0).
  569          */
  570         wh = mtod(m, struct ieee80211_frame *);
  571         ivp = mtod(m, const uint8_t *) + hdrlen;        /* XXX contig */
  572         keyid = ivp[IEEE80211_WEP_IVLEN];
  573         if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
  574             IEEE80211_KEY_UNDEFINED(&ni->ni_ucastkey))
  575                 k = &ic->ic_nw_keys[keyid >> 6];
  576         else
  577                 k = &ni->ni_ucastkey;
  578 
  579         /*
  580          * Insure crypto header is contiguous for all decap work.
  581          */
  582         cip = k->wk_cipher;
  583         if (m->m_len < hdrlen + cip->ic_header &&
  584             (m = m_pullup(m, hdrlen + cip->ic_header)) == NULL) {
  585                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  586                     "[%s] unable to pullup %s header\n",
  587                     ether_sprintf(wh->i_addr2), cip->ic_name);
  588                 ic->ic_stats.is_rx_wepfail++;   /* XXX */
  589                 return NULL;
  590         }
  591 
  592         return (cip->ic_decap(k, m, hdrlen) ? k : NULL);
  593 #undef IEEE80211_WEP_MINLEN
  594 #undef IEEE80211_WEP_HDRLEN
  595 }

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