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 /*      $NetBSD: ieee80211_crypto.c,v 1.15 2011/05/23 15:37:36 drochner Exp $   */
    2 /*-
    3  * Copyright (c) 2001 Atsushi Onoe
    4  * Copyright (c) 2002-2005 Sam Leffler, Errno Consulting
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. The name of the author may not be used to endorse or promote products
   16  *    derived from this software without specific prior written permission.
   17  *
   18  * Alternatively, this software may be distributed under the terms of the
   19  * GNU General Public License ("GPL") version 2 as published by the Free
   20  * Software Foundation.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   27  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   31  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 #ifdef __FreeBSD__
   36 __FBSDID("$FreeBSD: src/sys/net80211/ieee80211_crypto.c,v 1.12 2005/08/08 18:46:35 sam Exp $");
   37 #endif
   38 #ifdef __NetBSD__
   39 __KERNEL_RCSID(0, "$NetBSD: ieee80211_crypto.c,v 1.15 2011/05/23 15:37:36 drochner Exp $");
   40 #endif
   41 
   42 #include "opt_inet.h"
   43 
   44 /*
   45  * IEEE 802.11 generic crypto support.
   46  */
   47 #include <sys/param.h>
   48 #include <sys/mbuf.h>   
   49 
   50 #include <sys/socket.h>
   51 #include <sys/sockio.h>
   52 #include <sys/endian.h>
   53 #include <sys/errno.h>
   54 #include <sys/proc.h>
   55 #include <sys/sysctl.h>
   56 
   57 #include <net/if.h>
   58 #include <net/if_media.h>
   59 #include <net/if_arp.h>
   60 #include <net/if_ether.h>
   61 #include <net/if_llc.h>
   62 
   63 #include <net80211/ieee80211_netbsd.h>
   64 #include <net80211/ieee80211_var.h>
   65 
   66 /*
   67  * Table of registered cipher modules.
   68  */
   69 static  const struct ieee80211_cipher *ciphers[IEEE80211_CIPHER_MAX];
   70 
   71 #ifdef INET
   72 #include <netinet/in.h> 
   73 #include <net/if_ether.h>
   74 #endif
   75 
   76 static  int _ieee80211_crypto_delkey(struct ieee80211com *,
   77                 struct ieee80211_key *);
   78 
   79 /*
   80  * Default "null" key management routines.
   81  */
   82 static int
   83 null_key_alloc(struct ieee80211com *ic, const struct ieee80211_key *k,
   84         ieee80211_keyix *keyix, ieee80211_keyix *rxkeyix)
   85 {
   86         if (!(&ic->ic_nw_keys[0] <= k &&
   87              k < &ic->ic_nw_keys[IEEE80211_WEP_NKID])) {
   88                 /*
   89                  * Not in the global key table, the driver should handle this
   90                  * by allocating a slot in the h/w key table/cache.  In
   91                  * lieu of that return key slot 0 for any unicast key
   92                  * request.  We disallow the request if this is a group key.
   93                  * This default policy does the right thing for legacy hardware
   94                  * with a 4 key table.  It also handles devices that pass
   95                  * packets through untouched when marked with the WEP bit
   96                  * and key index 0.
   97                  */
   98                 if (k->wk_flags & IEEE80211_KEY_GROUP)
   99                         return 0;
  100                 *keyix = 0;     /* NB: use key index 0 for ucast key */
  101         } else {
  102                 *keyix = k - ic->ic_nw_keys;
  103         }
  104         *rxkeyix = IEEE80211_KEYIX_NONE;        /* XXX maybe *keyix? */
  105         return 1;
  106 }
  107 static int
  108 null_key_delete(struct ieee80211com *ic,
  109     const struct ieee80211_key *k)
  110 {
  111         return 1;
  112 }
  113 static  int
  114 null_key_set(struct ieee80211com *ic,
  115     const struct ieee80211_key *k,
  116     const u_int8_t mac[IEEE80211_ADDR_LEN])
  117 {
  118         return 1;
  119 }
  120 static void null_key_update(struct ieee80211com *ic) {}
  121 
  122 /*
  123  * Write-arounds for common operations.
  124  */
  125 static __inline void
  126 cipher_detach(struct ieee80211_key *key)
  127 {
  128         key->wk_cipher->ic_detach(key);
  129 }
  130 
  131 static __inline void *
  132 cipher_attach(struct ieee80211com *ic, struct ieee80211_key *key)
  133 {
  134         return key->wk_cipher->ic_attach(ic, key);
  135 }
  136 
  137 /* 
  138  * Wrappers for driver key management methods.
  139  */
  140 static __inline int
  141 dev_key_alloc(struct ieee80211com *ic,
  142         const struct ieee80211_key *key,
  143         ieee80211_keyix *keyix, ieee80211_keyix *rxkeyix)
  144 {
  145         return ic->ic_crypto.cs_key_alloc(ic, key, keyix, rxkeyix);
  146 }
  147 
  148 static __inline int
  149 dev_key_delete(struct ieee80211com *ic,
  150         const struct ieee80211_key *key)
  151 {
  152         return ic->ic_crypto.cs_key_delete(ic, key);
  153 }
  154 
  155 static __inline int
  156 dev_key_set(struct ieee80211com *ic, const struct ieee80211_key *key,
  157         const u_int8_t mac[IEEE80211_ADDR_LEN])
  158 {
  159         return ic->ic_crypto.cs_key_set(ic, key, mac);
  160 }
  161 
  162 /*
  163  * Setup crypto support.
  164  */
  165 void
  166 ieee80211_crypto_attach(struct ieee80211com *ic)
  167 {
  168         struct ieee80211_crypto_state *cs = &ic->ic_crypto;
  169         int i;
  170 
  171         /* NB: we assume everything is pre-zero'd */
  172         cs->cs_def_txkey = IEEE80211_KEYIX_NONE;
  173         cs->cs_max_keyix = IEEE80211_WEP_NKID;
  174         ciphers[IEEE80211_CIPHER_NONE] = &ieee80211_cipher_none;
  175         for (i = 0; i < IEEE80211_WEP_NKID; i++)
  176                 ieee80211_crypto_resetkey(ic, &cs->cs_nw_keys[i],
  177                         IEEE80211_KEYIX_NONE);
  178         /*
  179          * Initialize the driver key support routines to noop entries.
  180          * This is useful especially for the cipher test modules.
  181          */
  182         cs->cs_key_alloc = null_key_alloc;
  183         cs->cs_key_set = null_key_set;
  184         cs->cs_key_delete = null_key_delete;
  185         cs->cs_key_update_begin = null_key_update;
  186         cs->cs_key_update_end = null_key_update;
  187 }
  188 
  189 /*
  190  * Teardown crypto support.
  191  */
  192 void
  193 ieee80211_crypto_detach(struct ieee80211com *ic)
  194 {
  195         ieee80211_crypto_delglobalkeys(ic);
  196 }
  197 
  198 /*
  199  * Register a crypto cipher module.
  200  */
  201 void
  202 ieee80211_crypto_register(const struct ieee80211_cipher *cip)
  203 {
  204         if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
  205                 printf("%s: cipher %s has an invalid cipher index %u\n",
  206                         __func__, cip->ic_name, cip->ic_cipher);
  207                 return;
  208         }
  209         if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
  210                 printf("%s: cipher %s registered with a different template\n",
  211                         __func__, cip->ic_name);
  212                 return;
  213         }
  214         ciphers[cip->ic_cipher] = cip;
  215 }
  216 
  217 /*
  218  * Unregister a crypto cipher module.
  219  */
  220 void
  221 ieee80211_crypto_unregister(const struct ieee80211_cipher *cip)
  222 {
  223         if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
  224                 printf("%s: cipher %s has an invalid cipher index %u\n",
  225                         __func__, cip->ic_name, cip->ic_cipher);
  226                 return;
  227         }
  228         if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
  229                 printf("%s: cipher %s registered with a different template\n",
  230                         __func__, cip->ic_name);
  231                 return;
  232         }
  233         /* NB: don't complain about not being registered */
  234         /* XXX disallow if references */
  235         ciphers[cip->ic_cipher] = NULL;
  236 }
  237 
  238 int
  239 ieee80211_crypto_available(u_int cipher)
  240 {
  241         return cipher < IEEE80211_CIPHER_MAX && ciphers[cipher] != NULL;
  242 }
  243 
  244 /* XXX well-known names! */
  245 static const char *cipher_modnames[] = {
  246         "wlan_wep",     /* IEEE80211_CIPHER_WEP */
  247         "wlan_tkip",    /* IEEE80211_CIPHER_TKIP */
  248         "wlan_aes_ocb", /* IEEE80211_CIPHER_AES_OCB */
  249         "wlan_ccmp",    /* IEEE80211_CIPHER_AES_CCM */
  250         "wlan_ckip",    /* IEEE80211_CIPHER_CKIP */
  251 };
  252 
  253 /*
  254  * Establish a relationship between the specified key and cipher
  255  * and, if necessary, allocate a hardware index from the driver.
  256  * Note that when a fixed key index is required it must be specified
  257  * and we blindly assign it w/o consulting the driver (XXX).
  258  *
  259  * This must be the first call applied to a key; all the other key
  260  * routines assume wk_cipher is setup.
  261  *
  262  * Locking must be handled by the caller using:
  263  *      ieee80211_key_update_begin(ic);
  264  *      ieee80211_key_update_end(ic);
  265  */
  266 int
  267 ieee80211_crypto_newkey(struct ieee80211com *ic,
  268         int cipher, int flags, struct ieee80211_key *key)
  269 {
  270 #define N(a)    (sizeof(a) / sizeof(a[0]))
  271         const struct ieee80211_cipher *cip;
  272         ieee80211_keyix keyix, rxkeyix;
  273         void *keyctx;
  274         int oflags;
  275 
  276         /*
  277          * Validate cipher and set reference to cipher routines.
  278          */
  279         if (cipher >= IEEE80211_CIPHER_MAX) {
  280                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  281                         "%s: invalid cipher %u\n", __func__, cipher);
  282                 ic->ic_stats.is_crypto_badcipher++;
  283                 return 0;
  284         }
  285         cip = ciphers[cipher];
  286         if (cip == NULL) {
  287                 /*
  288                  * Auto-load cipher module if we have a well-known name
  289                  * for it.  It might be better to use string names rather
  290                  * than numbers and craft a module name based on the cipher
  291                  * name; e.g. wlan_cipher_<cipher-name>.
  292                  */
  293                 if (cipher < N(cipher_modnames)) {
  294                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  295                                 "%s: unregistered cipher %u, load module %s\n",
  296                                 __func__, cipher, cipher_modnames[cipher]);
  297                         ieee80211_load_module(cipher_modnames[cipher]);
  298                         /*
  299                          * If cipher module loaded it should immediately
  300                          * call ieee80211_crypto_register which will fill
  301                          * in the entry in the ciphers array.
  302                          */
  303                         cip = ciphers[cipher];
  304                 }
  305                 if (cip == NULL) {
  306                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  307                                 "%s: unable to load cipher %u, module %s\n",
  308                                 __func__, cipher,
  309                                 cipher < N(cipher_modnames) ?
  310                                         cipher_modnames[cipher] : "<unknown>");
  311                         ic->ic_stats.is_crypto_nocipher++;
  312                         return 0;
  313                 }
  314         }
  315 
  316         oflags = key->wk_flags;
  317         flags &= IEEE80211_KEY_COMMON;
  318         /*
  319          * If the hardware does not support the cipher then
  320          * fallback to a host-based implementation.
  321          */
  322         if ((ic->ic_caps & (1<<cipher)) == 0) {
  323                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  324                     "%s: no h/w support for cipher %s, falling back to s/w\n",
  325                     __func__, cip->ic_name);
  326                 flags |= IEEE80211_KEY_SWCRYPT;
  327         }
  328         /*
  329          * Hardware TKIP with software MIC is an important
  330          * combination; we handle it by flagging each key,
  331          * the cipher modules honor it.
  332          */
  333         if (cipher == IEEE80211_CIPHER_TKIP &&
  334             (ic->ic_caps & IEEE80211_C_TKIPMIC) == 0) {
  335                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  336                     "%s: no h/w support for TKIP MIC, falling back to s/w\n",
  337                     __func__);
  338                 flags |= IEEE80211_KEY_SWMIC;
  339         }
  340 
  341         /*
  342          * Bind cipher to key instance.  Note we do this
  343          * after checking the device capabilities so the
  344          * cipher module can optimize space usage based on
  345          * whether or not it needs to do the cipher work.
  346          */
  347         if (key->wk_cipher != cip || key->wk_flags != flags) {
  348 again:
  349                 /*
  350                  * Fillin the flags so cipher modules can see s/w
  351                  * crypto requirements and potentially allocate
  352                  * different state and/or attach different method
  353                  * pointers.
  354                  *
  355                  * XXX this is not right when s/w crypto fallback
  356                  *     fails and we try to restore previous state.
  357                  */
  358                 key->wk_flags = flags;
  359                 keyctx = cip->ic_attach(ic, key);
  360                 if (keyctx == NULL) {
  361                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  362                                 "%s: unable to attach cipher %s\n",
  363                                 __func__, cip->ic_name);
  364                         key->wk_flags = oflags; /* restore old flags */
  365                         ic->ic_stats.is_crypto_attachfail++;
  366                         return 0;
  367                 }
  368                 cipher_detach(key);
  369                 key->wk_cipher = cip;           /* XXX refcnt? */
  370                 key->wk_private = keyctx;
  371         }
  372         /*
  373          * Commit to requested usage so driver can see the flags.
  374          */
  375         key->wk_flags = flags;
  376 
  377         /*
  378          * Ask the driver for a key index if we don't have one.
  379          * Note that entries in the global key table always have
  380          * an index; this means it's safe to call this routine
  381          * for these entries just to setup the reference to the
  382          * cipher template.  Note also that when using software
  383          * crypto we also call the driver to give us a key index.
  384          */
  385         if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
  386                 if (!dev_key_alloc(ic, key, &keyix, &rxkeyix)) {
  387                         /*
  388                          * Driver has no room; fallback to doing crypto
  389                          * in the host.  We change the flags and start the
  390                          * procedure over.  If we get back here then there's
  391                          * no hope and we bail.  Note that this can leave
  392                          * the key in a inconsistent state if the caller
  393                          * continues to use it.
  394                          */
  395                         if ((key->wk_flags & IEEE80211_KEY_SWCRYPT) == 0) {
  396                                 ic->ic_stats.is_crypto_swfallback++;
  397                                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  398                                     "%s: no h/w resources for cipher %s, "
  399                                     "falling back to s/w\n", __func__,
  400                                     cip->ic_name);
  401                                 oflags = key->wk_flags;
  402                                 flags |= IEEE80211_KEY_SWCRYPT;
  403                                 if (cipher == IEEE80211_CIPHER_TKIP)
  404                                         flags |= IEEE80211_KEY_SWMIC;
  405                                 goto again;
  406                         }
  407                         ic->ic_stats.is_crypto_keyfail++;
  408                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  409                             "%s: unable to setup cipher %s\n",
  410                             __func__, cip->ic_name);
  411                         return 0;
  412                 }
  413                 key->wk_keyix = keyix;
  414                 key->wk_rxkeyix = rxkeyix;
  415         }
  416         return 1;
  417 #undef N
  418 }
  419 
  420 /*
  421  * Remove the key (no locking, for internal use).
  422  */
  423 static int
  424 _ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
  425 {
  426         ieee80211_keyix keyix;
  427 
  428         IASSERT(key->wk_cipher != NULL, ("No cipher!"));
  429 
  430         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  431             "%s: %s keyix %u flags 0x%x rsc %ju tsc %ju len %u\n",
  432             __func__, key->wk_cipher->ic_name,
  433             key->wk_keyix, key->wk_flags,
  434             key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);
  435 
  436         keyix = key->wk_keyix;
  437         if (keyix != IEEE80211_KEYIX_NONE) {
  438                 /*
  439                  * Remove hardware entry.
  440                  */
  441                 /* XXX key cache */
  442                 if (!dev_key_delete(ic, key)) {
  443                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  444                             "%s: driver did not delete key index %u\n",
  445                             __func__, keyix);
  446                         ic->ic_stats.is_crypto_delkey++;
  447                         /* XXX recovery? */
  448                 }
  449         }
  450         cipher_detach(key);
  451         memset(key, 0, sizeof(*key));
  452         ieee80211_crypto_resetkey(ic, key, IEEE80211_KEYIX_NONE);
  453         return 1;
  454 }
  455 
  456 /*
  457  * Remove the specified key.
  458  */
  459 int
  460 ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
  461 {
  462         int status;
  463 
  464         ieee80211_key_update_begin(ic);
  465         status = _ieee80211_crypto_delkey(ic, key);
  466         ieee80211_key_update_end(ic);
  467         return status;
  468 }
  469 
  470 /*
  471  * Clear the global key table.
  472  */
  473 void
  474 ieee80211_crypto_delglobalkeys(struct ieee80211com *ic)
  475 {
  476         int i;
  477 
  478         ieee80211_key_update_begin(ic);
  479         for (i = 0; i < IEEE80211_WEP_NKID; i++)
  480                 (void) _ieee80211_crypto_delkey(ic, &ic->ic_nw_keys[i]);
  481         ieee80211_key_update_end(ic);
  482 }
  483 
  484 /*
  485  * Set the contents of the specified key.
  486  *
  487  * Locking must be handled by the caller using:
  488  *      ieee80211_key_update_begin(ic);
  489  *      ieee80211_key_update_end(ic);
  490  */
  491 int
  492 ieee80211_crypto_setkey(struct ieee80211com *ic, struct ieee80211_key *key,
  493                 const u_int8_t macaddr[IEEE80211_ADDR_LEN])
  494 {
  495         const struct ieee80211_cipher *cip = key->wk_cipher;
  496 
  497         IASSERT(cip != NULL, ("No cipher!"));
  498 
  499         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  500             "%s: %s keyix %u flags 0x%x mac %s rsc %ju tsc %ju len %u\n",
  501             __func__, cip->ic_name, key->wk_keyix,
  502             key->wk_flags, ether_sprintf(macaddr),
  503             key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);
  504 
  505         /*
  506          * Give cipher a chance to validate key contents.
  507          * XXX should happen before modifying state.
  508          */
  509         if (!cip->ic_setkey(key)) {
  510                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  511                     "%s: cipher %s rejected key index %u len %u flags 0x%x\n",
  512                     __func__, cip->ic_name, key->wk_keyix,
  513                     key->wk_keylen, key->wk_flags);
  514                 ic->ic_stats.is_crypto_setkey_cipher++;
  515                 return 0;
  516         }
  517         if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
  518                 /* XXX nothing allocated, should not happen */
  519                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  520                     "%s: no key index; should not happen!\n", __func__);
  521                 ic->ic_stats.is_crypto_setkey_nokey++;
  522                 return 0;
  523         }
  524         return dev_key_set(ic, key, macaddr);
  525 }
  526 
  527 /*
  528  * Add privacy headers appropriate for the specified key.
  529  */
  530 struct ieee80211_key *
  531 ieee80211_crypto_encap(struct ieee80211com *ic,
  532         struct ieee80211_node *ni, struct mbuf *m)
  533 {
  534         struct ieee80211_key *k;
  535         struct ieee80211_frame *wh;
  536         const struct ieee80211_cipher *cip;
  537         u_int8_t keyid;
  538 
  539         /*
  540          * Multicast traffic always uses the multicast key.
  541          * Otherwise if a unicast key is set we use that and
  542          * it is always key index 0.  When no unicast key is
  543          * set we fall back to the default transmit key.
  544          */
  545         wh = mtod(m, struct ieee80211_frame *);
  546         if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
  547             ni->ni_ucastkey.wk_cipher == &ieee80211_cipher_none) {
  548                 if (ic->ic_def_txkey == IEEE80211_KEYIX_NONE) {
  549                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  550                             "[%s] no default transmit key (%s) deftxkey %u\n",
  551                             ether_sprintf(wh->i_addr1), __func__,
  552                             ic->ic_def_txkey);
  553                         ic->ic_stats.is_tx_nodefkey++;
  554                         return NULL;
  555                 }
  556                 keyid = ic->ic_def_txkey;
  557                 k = &ic->ic_nw_keys[ic->ic_def_txkey];
  558         } else {
  559                 keyid = 0;
  560                 k = &ni->ni_ucastkey;
  561         }
  562         cip = k->wk_cipher;
  563         return (cip->ic_encap(k, m, keyid<<6) ? k : NULL);
  564 }
  565 
  566 /*
  567  * Validate and strip privacy headers (and trailer) for a
  568  * received frame that has the WEP/Privacy bit set.
  569  */
  570 struct ieee80211_key *
  571 ieee80211_crypto_decap(struct ieee80211com *ic,
  572         struct ieee80211_node *ni, struct mbuf *m, int hdrlen)
  573 {
  574 #define IEEE80211_WEP_HDRLEN    (IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN)
  575 #define IEEE80211_WEP_MINLEN \
  576         (sizeof(struct ieee80211_frame) + \
  577         IEEE80211_WEP_HDRLEN + IEEE80211_WEP_CRCLEN)
  578         struct ieee80211_key *k;
  579         struct ieee80211_frame *wh;
  580         const struct ieee80211_cipher *cip;
  581         u_int8_t keyid;
  582 
  583         /* NB: this minimum size data frame could be bigger */
  584         if (m->m_pkthdr.len < IEEE80211_WEP_MINLEN) {
  585                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_ANY,
  586                         "%s: WEP data frame too short, len %u\n",
  587                         __func__, m->m_pkthdr.len);
  588                 ic->ic_stats.is_rx_tooshort++;  /* XXX need unique stat? */
  589                 return NULL;
  590         }
  591 
  592         /*
  593          * Locate the key. If unicast and there is no unicast
  594          * key then we fall back to the key id in the header.
  595          * This assumes unicast keys are only configured when
  596          * the key id in the header is meaningless (typically 0).
  597          */
  598         wh = mtod(m, struct ieee80211_frame *);
  599         m_copydata(m, hdrlen + IEEE80211_WEP_IVLEN, sizeof(keyid), &keyid);
  600         if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
  601             ni->ni_ucastkey.wk_cipher == &ieee80211_cipher_none)
  602                 k = &ic->ic_nw_keys[keyid >> 6];
  603         else
  604                 k = &ni->ni_ucastkey;
  605 
  606         /*
  607          * Insure crypto header is contiguous for all decap work.
  608          */
  609         cip = k->wk_cipher;
  610         if (m->m_len < hdrlen + cip->ic_header &&
  611             (m = m_pullup(m, hdrlen + cip->ic_header)) == NULL) {
  612                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  613                     "[%s] unable to pullup %s header\n",
  614                     ether_sprintf(wh->i_addr2), cip->ic_name);
  615                 ic->ic_stats.is_rx_wepfail++;   /* XXX */
  616                 return NULL;
  617         }
  618 
  619         return (cip->ic_decap(k, m, hdrlen) ? k : NULL);
  620 #undef IEEE80211_WEP_MINLEN
  621 #undef IEEE80211_WEP_HDRLEN
  622 }

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