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 1.14 2006/11/16 01:33:40 christos 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 1.14 2006/11/16 01:33:40 christos 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 #include <crypto/arc4/arc4.h>   /* XXX unneeded? */
   77 static  int _ieee80211_crypto_delkey(struct ieee80211com *,
   78                 struct ieee80211_key *);
   79 
   80 /*
   81  * Default "null" key management routines.
   82  */
   83 static int
   84 null_key_alloc(struct ieee80211com *ic, const struct ieee80211_key *k,
   85         ieee80211_keyix *keyix, ieee80211_keyix *rxkeyix)
   86 {
   87         if (!(&ic->ic_nw_keys[0] <= k &&
   88              k < &ic->ic_nw_keys[IEEE80211_WEP_NKID])) {
   89                 /*
   90                  * Not in the global key table, the driver should handle this
   91                  * by allocating a slot in the h/w key table/cache.  In
   92                  * lieu of that return key slot 0 for any unicast key
   93                  * request.  We disallow the request if this is a group key.
   94                  * This default policy does the right thing for legacy hardware
   95                  * with a 4 key table.  It also handles devices that pass
   96                  * packets through untouched when marked with the WEP bit
   97                  * and key index 0.
   98                  */
   99                 if (k->wk_flags & IEEE80211_KEY_GROUP)
  100                         return 0;
  101                 *keyix = 0;     /* NB: use key index 0 for ucast key */
  102         } else {
  103                 *keyix = k - ic->ic_nw_keys;
  104         }
  105         *rxkeyix = IEEE80211_KEYIX_NONE;        /* XXX maybe *keyix? */
  106         return 1;
  107 }
  108 static int
  109 null_key_delete(struct ieee80211com *ic,
  110     const struct ieee80211_key *k)
  111 {
  112         return 1;
  113 }
  114 static  int
  115 null_key_set(struct ieee80211com *ic,
  116     const struct ieee80211_key *k,
  117     const u_int8_t mac[IEEE80211_ADDR_LEN])
  118 {
  119         return 1;
  120 }
  121 static void null_key_update(struct ieee80211com *ic) {}
  122 
  123 /*
  124  * Write-arounds for common operations.
  125  */
  126 static __inline void
  127 cipher_detach(struct ieee80211_key *key)
  128 {
  129         key->wk_cipher->ic_detach(key);
  130 }
  131 
  132 static __inline void *
  133 cipher_attach(struct ieee80211com *ic, struct ieee80211_key *key)
  134 {
  135         return key->wk_cipher->ic_attach(ic, key);
  136 }
  137 
  138 /* 
  139  * Wrappers for driver key management methods.
  140  */
  141 static __inline int
  142 dev_key_alloc(struct ieee80211com *ic,
  143         const struct ieee80211_key *key,
  144         ieee80211_keyix *keyix, ieee80211_keyix *rxkeyix)
  145 {
  146         return ic->ic_crypto.cs_key_alloc(ic, key, keyix, rxkeyix);
  147 }
  148 
  149 static __inline int
  150 dev_key_delete(struct ieee80211com *ic,
  151         const struct ieee80211_key *key)
  152 {
  153         return ic->ic_crypto.cs_key_delete(ic, key);
  154 }
  155 
  156 static __inline int
  157 dev_key_set(struct ieee80211com *ic, const struct ieee80211_key *key,
  158         const u_int8_t mac[IEEE80211_ADDR_LEN])
  159 {
  160         return ic->ic_crypto.cs_key_set(ic, key, mac);
  161 }
  162 
  163 /*
  164  * Setup crypto support.
  165  */
  166 void
  167 ieee80211_crypto_attach(struct ieee80211com *ic)
  168 {
  169         struct ieee80211_crypto_state *cs = &ic->ic_crypto;
  170         int i;
  171 
  172         /* NB: we assume everything is pre-zero'd */
  173         cs->cs_def_txkey = IEEE80211_KEYIX_NONE;
  174         cs->cs_max_keyix = IEEE80211_WEP_NKID;
  175         ciphers[IEEE80211_CIPHER_NONE] = &ieee80211_cipher_none;
  176         for (i = 0; i < IEEE80211_WEP_NKID; i++)
  177                 ieee80211_crypto_resetkey(ic, &cs->cs_nw_keys[i],
  178                         IEEE80211_KEYIX_NONE);
  179         /*
  180          * Initialize the driver key support routines to noop entries.
  181          * This is useful especially for the cipher test modules.
  182          */
  183         cs->cs_key_alloc = null_key_alloc;
  184         cs->cs_key_set = null_key_set;
  185         cs->cs_key_delete = null_key_delete;
  186         cs->cs_key_update_begin = null_key_update;
  187         cs->cs_key_update_end = null_key_update;
  188 }
  189 
  190 /*
  191  * Teardown crypto support.
  192  */
  193 void
  194 ieee80211_crypto_detach(struct ieee80211com *ic)
  195 {
  196         ieee80211_crypto_delglobalkeys(ic);
  197 }
  198 
  199 /*
  200  * Register a crypto cipher module.
  201  */
  202 void
  203 ieee80211_crypto_register(const struct ieee80211_cipher *cip)
  204 {
  205         if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
  206                 printf("%s: cipher %s has an invalid cipher index %u\n",
  207                         __func__, cip->ic_name, cip->ic_cipher);
  208                 return;
  209         }
  210         if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
  211                 printf("%s: cipher %s registered with a different template\n",
  212                         __func__, cip->ic_name);
  213                 return;
  214         }
  215         ciphers[cip->ic_cipher] = cip;
  216 }
  217 
  218 /*
  219  * Unregister a crypto cipher module.
  220  */
  221 void
  222 ieee80211_crypto_unregister(const struct ieee80211_cipher *cip)
  223 {
  224         if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
  225                 printf("%s: cipher %s has an invalid cipher index %u\n",
  226                         __func__, cip->ic_name, cip->ic_cipher);
  227                 return;
  228         }
  229         if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
  230                 printf("%s: cipher %s registered with a different template\n",
  231                         __func__, cip->ic_name);
  232                 return;
  233         }
  234         /* NB: don't complain about not being registered */
  235         /* XXX disallow if references */
  236         ciphers[cip->ic_cipher] = NULL;
  237 }
  238 
  239 int
  240 ieee80211_crypto_available(u_int cipher)
  241 {
  242         return cipher < IEEE80211_CIPHER_MAX && ciphers[cipher] != NULL;
  243 }
  244 
  245 /* XXX well-known names! */
  246 static const char *cipher_modnames[] = {
  247         "wlan_wep",     /* IEEE80211_CIPHER_WEP */
  248         "wlan_tkip",    /* IEEE80211_CIPHER_TKIP */
  249         "wlan_aes_ocb", /* IEEE80211_CIPHER_AES_OCB */
  250         "wlan_ccmp",    /* IEEE80211_CIPHER_AES_CCM */
  251         "wlan_ckip",    /* IEEE80211_CIPHER_CKIP */
  252 };
  253 
  254 /*
  255  * Establish a relationship between the specified key and cipher
  256  * and, if necessary, allocate a hardware index from the driver.
  257  * Note that when a fixed key index is required it must be specified
  258  * and we blindly assign it w/o consulting the driver (XXX).
  259  *
  260  * This must be the first call applied to a key; all the other key
  261  * routines assume wk_cipher is setup.
  262  *
  263  * Locking must be handled by the caller using:
  264  *      ieee80211_key_update_begin(ic);
  265  *      ieee80211_key_update_end(ic);
  266  */
  267 int
  268 ieee80211_crypto_newkey(struct ieee80211com *ic,
  269         int cipher, int flags, struct ieee80211_key *key)
  270 {
  271 #define N(a)    (sizeof(a) / sizeof(a[0]))
  272         const struct ieee80211_cipher *cip;
  273         ieee80211_keyix keyix, rxkeyix;
  274         void *keyctx;
  275         int oflags;
  276 
  277         /*
  278          * Validate cipher and set reference to cipher routines.
  279          */
  280         if (cipher >= IEEE80211_CIPHER_MAX) {
  281                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  282                         "%s: invalid cipher %u\n", __func__, cipher);
  283                 ic->ic_stats.is_crypto_badcipher++;
  284                 return 0;
  285         }
  286         cip = ciphers[cipher];
  287         if (cip == NULL) {
  288                 /*
  289                  * Auto-load cipher module if we have a well-known name
  290                  * for it.  It might be better to use string names rather
  291                  * than numbers and craft a module name based on the cipher
  292                  * name; e.g. wlan_cipher_<cipher-name>.
  293                  */
  294                 if (cipher < N(cipher_modnames)) {
  295                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  296                                 "%s: unregistered cipher %u, load module %s\n",
  297                                 __func__, cipher, cipher_modnames[cipher]);
  298                         ieee80211_load_module(cipher_modnames[cipher]);
  299                         /*
  300                          * If cipher module loaded it should immediately
  301                          * call ieee80211_crypto_register which will fill
  302                          * in the entry in the ciphers array.
  303                          */
  304                         cip = ciphers[cipher];
  305                 }
  306                 if (cip == NULL) {
  307                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  308                                 "%s: unable to load cipher %u, module %s\n",
  309                                 __func__, cipher,
  310                                 cipher < N(cipher_modnames) ?
  311                                         cipher_modnames[cipher] : "<unknown>");
  312                         ic->ic_stats.is_crypto_nocipher++;
  313                         return 0;
  314                 }
  315         }
  316 
  317         oflags = key->wk_flags;
  318         flags &= IEEE80211_KEY_COMMON;
  319         /*
  320          * If the hardware does not support the cipher then
  321          * fallback to a host-based implementation.
  322          */
  323         if ((ic->ic_caps & (1<<cipher)) == 0) {
  324                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  325                     "%s: no h/w support for cipher %s, falling back to s/w\n",
  326                     __func__, cip->ic_name);
  327                 flags |= IEEE80211_KEY_SWCRYPT;
  328         }
  329         /*
  330          * Hardware TKIP with software MIC is an important
  331          * combination; we handle it by flagging each key,
  332          * the cipher modules honor it.
  333          */
  334         if (cipher == IEEE80211_CIPHER_TKIP &&
  335             (ic->ic_caps & IEEE80211_C_TKIPMIC) == 0) {
  336                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  337                     "%s: no h/w support for TKIP MIC, falling back to s/w\n",
  338                     __func__);
  339                 flags |= IEEE80211_KEY_SWMIC;
  340         }
  341 
  342         /*
  343          * Bind cipher to key instance.  Note we do this
  344          * after checking the device capabilities so the
  345          * cipher module can optimize space usage based on
  346          * whether or not it needs to do the cipher work.
  347          */
  348         if (key->wk_cipher != cip || key->wk_flags != flags) {
  349 again:
  350                 /*
  351                  * Fillin the flags so cipher modules can see s/w
  352                  * crypto requirements and potentially allocate
  353                  * different state and/or attach different method
  354                  * pointers.
  355                  *
  356                  * XXX this is not right when s/w crypto fallback
  357                  *     fails and we try to restore previous state.
  358                  */
  359                 key->wk_flags = flags;
  360                 keyctx = cip->ic_attach(ic, key);
  361                 if (keyctx == NULL) {
  362                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  363                                 "%s: unable to attach cipher %s\n",
  364                                 __func__, cip->ic_name);
  365                         key->wk_flags = oflags; /* restore old flags */
  366                         ic->ic_stats.is_crypto_attachfail++;
  367                         return 0;
  368                 }
  369                 cipher_detach(key);
  370                 key->wk_cipher = cip;           /* XXX refcnt? */
  371                 key->wk_private = keyctx;
  372         }
  373         /*
  374          * Commit to requested usage so driver can see the flags.
  375          */
  376         key->wk_flags = flags;
  377 
  378         /*
  379          * Ask the driver for a key index if we don't have one.
  380          * Note that entries in the global key table always have
  381          * an index; this means it's safe to call this routine
  382          * for these entries just to setup the reference to the
  383          * cipher template.  Note also that when using software
  384          * crypto we also call the driver to give us a key index.
  385          */
  386         if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
  387                 if (!dev_key_alloc(ic, key, &keyix, &rxkeyix)) {
  388                         /*
  389                          * Driver has no room; fallback to doing crypto
  390                          * in the host.  We change the flags and start the
  391                          * procedure over.  If we get back here then there's
  392                          * no hope and we bail.  Note that this can leave
  393                          * the key in a inconsistent state if the caller
  394                          * continues to use it.
  395                          */
  396                         if ((key->wk_flags & IEEE80211_KEY_SWCRYPT) == 0) {
  397                                 ic->ic_stats.is_crypto_swfallback++;
  398                                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  399                                     "%s: no h/w resources for cipher %s, "
  400                                     "falling back to s/w\n", __func__,
  401                                     cip->ic_name);
  402                                 oflags = key->wk_flags;
  403                                 flags |= IEEE80211_KEY_SWCRYPT;
  404                                 if (cipher == IEEE80211_CIPHER_TKIP)
  405                                         flags |= IEEE80211_KEY_SWMIC;
  406                                 goto again;
  407                         }
  408                         ic->ic_stats.is_crypto_keyfail++;
  409                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  410                             "%s: unable to setup cipher %s\n",
  411                             __func__, cip->ic_name);
  412                         return 0;
  413                 }
  414                 key->wk_keyix = keyix;
  415                 key->wk_rxkeyix = rxkeyix;
  416         }
  417         return 1;
  418 #undef N
  419 }
  420 
  421 /*
  422  * Remove the key (no locking, for internal use).
  423  */
  424 static int
  425 _ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
  426 {
  427         ieee80211_keyix keyix;
  428 
  429         IASSERT(key->wk_cipher != NULL, ("No cipher!"));
  430 
  431         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  432             "%s: %s keyix %u flags 0x%x rsc %ju tsc %ju len %u\n",
  433             __func__, key->wk_cipher->ic_name,
  434             key->wk_keyix, key->wk_flags,
  435             key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);
  436 
  437         keyix = key->wk_keyix;
  438         if (keyix != IEEE80211_KEYIX_NONE) {
  439                 /*
  440                  * Remove hardware entry.
  441                  */
  442                 /* XXX key cache */
  443                 if (!dev_key_delete(ic, key)) {
  444                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  445                             "%s: driver did not delete key index %u\n",
  446                             __func__, keyix);
  447                         ic->ic_stats.is_crypto_delkey++;
  448                         /* XXX recovery? */
  449                 }
  450         }
  451         cipher_detach(key);
  452         memset(key, 0, sizeof(*key));
  453         ieee80211_crypto_resetkey(ic, key, IEEE80211_KEYIX_NONE);
  454         return 1;
  455 }
  456 
  457 /*
  458  * Remove the specified key.
  459  */
  460 int
  461 ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
  462 {
  463         int status;
  464 
  465         ieee80211_key_update_begin(ic);
  466         status = _ieee80211_crypto_delkey(ic, key);
  467         ieee80211_key_update_end(ic);
  468         return status;
  469 }
  470 
  471 /*
  472  * Clear the global key table.
  473  */
  474 void
  475 ieee80211_crypto_delglobalkeys(struct ieee80211com *ic)
  476 {
  477         int i;
  478 
  479         ieee80211_key_update_begin(ic);
  480         for (i = 0; i < IEEE80211_WEP_NKID; i++)
  481                 (void) _ieee80211_crypto_delkey(ic, &ic->ic_nw_keys[i]);
  482         ieee80211_key_update_end(ic);
  483 }
  484 
  485 /*
  486  * Set the contents of the specified key.
  487  *
  488  * Locking must be handled by the caller using:
  489  *      ieee80211_key_update_begin(ic);
  490  *      ieee80211_key_update_end(ic);
  491  */
  492 int
  493 ieee80211_crypto_setkey(struct ieee80211com *ic, struct ieee80211_key *key,
  494                 const u_int8_t macaddr[IEEE80211_ADDR_LEN])
  495 {
  496         const struct ieee80211_cipher *cip = key->wk_cipher;
  497 
  498         IASSERT(cip != NULL, ("No cipher!"));
  499 
  500         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  501             "%s: %s keyix %u flags 0x%x mac %s rsc %ju tsc %ju len %u\n",
  502             __func__, cip->ic_name, key->wk_keyix,
  503             key->wk_flags, ether_sprintf(macaddr),
  504             key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);
  505 
  506         /*
  507          * Give cipher a chance to validate key contents.
  508          * XXX should happen before modifying state.
  509          */
  510         if (!cip->ic_setkey(key)) {
  511                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  512                     "%s: cipher %s rejected key index %u len %u flags 0x%x\n",
  513                     __func__, cip->ic_name, key->wk_keyix,
  514                     key->wk_keylen, key->wk_flags);
  515                 ic->ic_stats.is_crypto_setkey_cipher++;
  516                 return 0;
  517         }
  518         if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
  519                 /* XXX nothing allocated, should not happen */
  520                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  521                     "%s: no key index; should not happen!\n", __func__);
  522                 ic->ic_stats.is_crypto_setkey_nokey++;
  523                 return 0;
  524         }
  525         return dev_key_set(ic, key, macaddr);
  526 }
  527 
  528 /*
  529  * Add privacy headers appropriate for the specified key.
  530  */
  531 struct ieee80211_key *
  532 ieee80211_crypto_encap(struct ieee80211com *ic,
  533         struct ieee80211_node *ni, struct mbuf *m)
  534 {
  535         struct ieee80211_key *k;
  536         struct ieee80211_frame *wh;
  537         const struct ieee80211_cipher *cip;
  538         u_int8_t keyid;
  539 
  540         /*
  541          * Multicast traffic always uses the multicast key.
  542          * Otherwise if a unicast key is set we use that and
  543          * it is always key index 0.  When no unicast key is
  544          * set we fall back to the default transmit key.
  545          */
  546         wh = mtod(m, struct ieee80211_frame *);
  547         if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
  548             ni->ni_ucastkey.wk_cipher == &ieee80211_cipher_none) {
  549                 if (ic->ic_def_txkey == IEEE80211_KEYIX_NONE) {
  550                         IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  551                             "[%s] no default transmit key (%s) deftxkey %u\n",
  552                             ether_sprintf(wh->i_addr1), __func__,
  553                             ic->ic_def_txkey);
  554                         ic->ic_stats.is_tx_nodefkey++;
  555                         return NULL;
  556                 }
  557                 keyid = ic->ic_def_txkey;
  558                 k = &ic->ic_nw_keys[ic->ic_def_txkey];
  559         } else {
  560                 keyid = 0;
  561                 k = &ni->ni_ucastkey;
  562         }
  563         cip = k->wk_cipher;
  564         return (cip->ic_encap(k, m, keyid<<6) ? k : NULL);
  565 }
  566 
  567 /*
  568  * Validate and strip privacy headers (and trailer) for a
  569  * received frame that has the WEP/Privacy bit set.
  570  */
  571 struct ieee80211_key *
  572 ieee80211_crypto_decap(struct ieee80211com *ic,
  573         struct ieee80211_node *ni, struct mbuf *m, int hdrlen)
  574 {
  575 #define IEEE80211_WEP_HDRLEN    (IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN)
  576 #define IEEE80211_WEP_MINLEN \
  577         (sizeof(struct ieee80211_frame) + \
  578         IEEE80211_WEP_HDRLEN + IEEE80211_WEP_CRCLEN)
  579         struct ieee80211_key *k;
  580         struct ieee80211_frame *wh;
  581         const struct ieee80211_cipher *cip;
  582         u_int8_t keyid;
  583 
  584         /* NB: this minimum size data frame could be bigger */
  585         if (m->m_pkthdr.len < IEEE80211_WEP_MINLEN) {
  586                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_ANY,
  587                         "%s: WEP data frame too short, len %u\n",
  588                         __func__, m->m_pkthdr.len);
  589                 ic->ic_stats.is_rx_tooshort++;  /* XXX need unique stat? */
  590                 return NULL;
  591         }
  592 
  593         /*
  594          * Locate the key. If unicast and there is no unicast
  595          * key then we fall back to the key id in the header.
  596          * This assumes unicast keys are only configured when
  597          * the key id in the header is meaningless (typically 0).
  598          */
  599         wh = mtod(m, struct ieee80211_frame *);
  600         m_copydata(m, hdrlen + IEEE80211_WEP_IVLEN, sizeof(keyid), &keyid);
  601         if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
  602             ni->ni_ucastkey.wk_cipher == &ieee80211_cipher_none)
  603                 k = &ic->ic_nw_keys[keyid >> 6];
  604         else
  605                 k = &ni->ni_ucastkey;
  606 
  607         /*
  608          * Insure crypto header is contiguous for all decap work.
  609          */
  610         cip = k->wk_cipher;
  611         if (m->m_len < hdrlen + cip->ic_header &&
  612             (m = m_pullup(m, hdrlen + cip->ic_header)) == NULL) {
  613                 IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
  614                     "[%s] unable to pullup %s header\n",
  615                     ether_sprintf(wh->i_addr2), cip->ic_name);
  616                 ic->ic_stats.is_rx_wepfail++;   /* XXX */
  617                 return NULL;
  618         }
  619 
  620         return (cip->ic_decap(k, m, hdrlen) ? k : NULL);
  621 #undef IEEE80211_WEP_MINLEN
  622 #undef IEEE80211_WEP_HDRLEN
  623 }

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