xref: /netbsd-src/sys/net80211/ieee80211_crypto.c (revision e5548b402ae4c44fb816de42c7bba9581ce23ef5)
1 /*	$NetBSD: ieee80211_crypto.c,v 1.10 2005/11/18 16:40:08 skrll 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 1.10 2005/11/18 16:40:08 skrll 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, const struct ieee80211_key *k)
110 {
111 	return 1;
112 }
113 static 	int
114 null_key_set(struct ieee80211com *ic, const struct ieee80211_key *k,
115 	     const u_int8_t mac[IEEE80211_ADDR_LEN])
116 {
117 	return 1;
118 }
119 static void null_key_update(struct ieee80211com *ic) {}
120 
121 /*
122  * Write-arounds for common operations.
123  */
124 static __inline void
125 cipher_detach(struct ieee80211_key *key)
126 {
127 	key->wk_cipher->ic_detach(key);
128 }
129 
130 static __inline void *
131 cipher_attach(struct ieee80211com *ic, struct ieee80211_key *key)
132 {
133 	return key->wk_cipher->ic_attach(ic, key);
134 }
135 
136 /*
137  * Wrappers for driver key management methods.
138  */
139 static __inline int
140 dev_key_alloc(struct ieee80211com *ic,
141 	const struct ieee80211_key *key,
142 	ieee80211_keyix *keyix, ieee80211_keyix *rxkeyix)
143 {
144 	return ic->ic_crypto.cs_key_alloc(ic, key, keyix, rxkeyix);
145 }
146 
147 static __inline int
148 dev_key_delete(struct ieee80211com *ic,
149 	const struct ieee80211_key *key)
150 {
151 	return ic->ic_crypto.cs_key_delete(ic, key);
152 }
153 
154 static __inline int
155 dev_key_set(struct ieee80211com *ic, const struct ieee80211_key *key,
156 	const u_int8_t mac[IEEE80211_ADDR_LEN])
157 {
158 	return ic->ic_crypto.cs_key_set(ic, key, mac);
159 }
160 
161 /*
162  * Setup crypto support.
163  */
164 void
165 ieee80211_crypto_attach(struct ieee80211com *ic)
166 {
167 	struct ieee80211_crypto_state *cs = &ic->ic_crypto;
168 	int i;
169 
170 	/* NB: we assume everything is pre-zero'd */
171 	cs->cs_def_txkey = IEEE80211_KEYIX_NONE;
172 	cs->cs_max_keyix = IEEE80211_WEP_NKID;
173 	ciphers[IEEE80211_CIPHER_NONE] = &ieee80211_cipher_none;
174 	for (i = 0; i < IEEE80211_WEP_NKID; i++)
175 		ieee80211_crypto_resetkey(ic, &cs->cs_nw_keys[i],
176 			IEEE80211_KEYIX_NONE);
177 	/*
178 	 * Initialize the driver key support routines to noop entries.
179 	 * This is useful especially for the cipher test modules.
180 	 */
181 	cs->cs_key_alloc = null_key_alloc;
182 	cs->cs_key_set = null_key_set;
183 	cs->cs_key_delete = null_key_delete;
184 	cs->cs_key_update_begin = null_key_update;
185 	cs->cs_key_update_end = null_key_update;
186 }
187 
188 /*
189  * Teardown crypto support.
190  */
191 void
192 ieee80211_crypto_detach(struct ieee80211com *ic)
193 {
194 	ieee80211_crypto_delglobalkeys(ic);
195 }
196 
197 /*
198  * Register a crypto cipher module.
199  */
200 void
201 ieee80211_crypto_register(const struct ieee80211_cipher *cip)
202 {
203 	if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
204 		printf("%s: cipher %s has an invalid cipher index %u\n",
205 			__func__, cip->ic_name, cip->ic_cipher);
206 		return;
207 	}
208 	if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
209 		printf("%s: cipher %s registered with a different template\n",
210 			__func__, cip->ic_name);
211 		return;
212 	}
213 	ciphers[cip->ic_cipher] = cip;
214 }
215 
216 /*
217  * Unregister a crypto cipher module.
218  */
219 void
220 ieee80211_crypto_unregister(const struct ieee80211_cipher *cip)
221 {
222 	if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
223 		printf("%s: cipher %s has an invalid cipher index %u\n",
224 			__func__, cip->ic_name, cip->ic_cipher);
225 		return;
226 	}
227 	if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
228 		printf("%s: cipher %s registered with a different template\n",
229 			__func__, cip->ic_name);
230 		return;
231 	}
232 	/* NB: don't complain about not being registered */
233 	/* XXX disallow if references */
234 	ciphers[cip->ic_cipher] = NULL;
235 }
236 
237 int
238 ieee80211_crypto_available(u_int cipher)
239 {
240 	return cipher < IEEE80211_CIPHER_MAX && ciphers[cipher] != NULL;
241 }
242 
243 /* XXX well-known names! */
244 static const char *cipher_modnames[] = {
245 	"wlan_wep",	/* IEEE80211_CIPHER_WEP */
246 	"wlan_tkip",	/* IEEE80211_CIPHER_TKIP */
247 	"wlan_aes_ocb",	/* IEEE80211_CIPHER_AES_OCB */
248 	"wlan_ccmp",	/* IEEE80211_CIPHER_AES_CCM */
249 	"wlan_ckip",	/* IEEE80211_CIPHER_CKIP */
250 };
251 
252 /*
253  * Establish a relationship between the specified key and cipher
254  * and, if necessary, allocate a hardware index from the driver.
255  * Note that when a fixed key index is required it must be specified
256  * and we blindly assign it w/o consulting the driver (XXX).
257  *
258  * This must be the first call applied to a key; all the other key
259  * routines assume wk_cipher is setup.
260  *
261  * Locking must be handled by the caller using:
262  *	ieee80211_key_update_begin(ic);
263  *	ieee80211_key_update_end(ic);
264  */
265 int
266 ieee80211_crypto_newkey(struct ieee80211com *ic,
267 	int cipher, int flags, struct ieee80211_key *key)
268 {
269 #define	N(a)	(sizeof(a) / sizeof(a[0]))
270 	const struct ieee80211_cipher *cip;
271 	ieee80211_keyix keyix, rxkeyix;
272 	void *keyctx;
273 	int oflags;
274 
275 	/*
276 	 * Validate cipher and set reference to cipher routines.
277 	 */
278 	if (cipher >= IEEE80211_CIPHER_MAX) {
279 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
280 			"%s: invalid cipher %u\n", __func__, cipher);
281 		ic->ic_stats.is_crypto_badcipher++;
282 		return 0;
283 	}
284 	cip = ciphers[cipher];
285 	if (cip == NULL) {
286 		/*
287 		 * Auto-load cipher module if we have a well-known name
288 		 * for it.  It might be better to use string names rather
289 		 * than numbers and craft a module name based on the cipher
290 		 * name; e.g. wlan_cipher_<cipher-name>.
291 		 */
292 		if (cipher < N(cipher_modnames)) {
293 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
294 				"%s: unregistered cipher %u, load module %s\n",
295 				__func__, cipher, cipher_modnames[cipher]);
296 			ieee80211_load_module(cipher_modnames[cipher]);
297 			/*
298 			 * If cipher module loaded it should immediately
299 			 * call ieee80211_crypto_register which will fill
300 			 * in the entry in the ciphers array.
301 			 */
302 			cip = ciphers[cipher];
303 		}
304 		if (cip == NULL) {
305 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
306 				"%s: unable to load cipher %u, module %s\n",
307 				__func__, cipher,
308 				cipher < N(cipher_modnames) ?
309 					cipher_modnames[cipher] : "<unknown>");
310 			ic->ic_stats.is_crypto_nocipher++;
311 			return 0;
312 		}
313 	}
314 
315 	oflags = key->wk_flags;
316 	flags &= IEEE80211_KEY_COMMON;
317 	/*
318 	 * If the hardware does not support the cipher then
319 	 * fallback to a host-based implementation.
320 	 */
321 	if ((ic->ic_caps & (1<<cipher)) == 0) {
322 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
323 		    "%s: no h/w support for cipher %s, falling back to s/w\n",
324 		    __func__, cip->ic_name);
325 		flags |= IEEE80211_KEY_SWCRYPT;
326 	}
327 	/*
328 	 * Hardware TKIP with software MIC is an important
329 	 * combination; we handle it by flagging each key,
330 	 * the cipher modules honor it.
331 	 */
332 	if (cipher == IEEE80211_CIPHER_TKIP &&
333 	    (ic->ic_caps & IEEE80211_C_TKIPMIC) == 0) {
334 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
335 		    "%s: no h/w support for TKIP MIC, falling back to s/w\n",
336 		    __func__);
337 		flags |= IEEE80211_KEY_SWMIC;
338 	}
339 
340 	/*
341 	 * Bind cipher to key instance.  Note we do this
342 	 * after checking the device capabilities so the
343 	 * cipher module can optimize space usage based on
344 	 * whether or not it needs to do the cipher work.
345 	 */
346 	if (key->wk_cipher != cip || key->wk_flags != flags) {
347 again:
348 		/*
349 		 * Fillin the flags so cipher modules can see s/w
350 		 * crypto requirements and potentially allocate
351 		 * different state and/or attach different method
352 		 * pointers.
353 		 *
354 		 * XXX this is not right when s/w crypto fallback
355 		 *     fails and we try to restore previous state.
356 		 */
357 		key->wk_flags = flags;
358 		keyctx = cip->ic_attach(ic, key);
359 		if (keyctx == NULL) {
360 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
361 				"%s: unable to attach cipher %s\n",
362 				__func__, cip->ic_name);
363 			key->wk_flags = oflags;	/* restore old flags */
364 			ic->ic_stats.is_crypto_attachfail++;
365 			return 0;
366 		}
367 		cipher_detach(key);
368 		key->wk_cipher = cip;		/* XXX refcnt? */
369 		key->wk_private = keyctx;
370 	}
371 	/*
372 	 * Commit to requested usage so driver can see the flags.
373 	 */
374 	key->wk_flags = flags;
375 
376 	/*
377 	 * Ask the driver for a key index if we don't have one.
378 	 * Note that entries in the global key table always have
379 	 * an index; this means it's safe to call this routine
380 	 * for these entries just to setup the reference to the
381 	 * cipher template.  Note also that when using software
382 	 * crypto we also call the driver to give us a key index.
383 	 */
384 	if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
385 		if (!dev_key_alloc(ic, key, &keyix, &rxkeyix)) {
386 			/*
387 			 * Driver has no room; fallback to doing crypto
388 			 * in the host.  We change the flags and start the
389 			 * procedure over.  If we get back here then there's
390 			 * no hope and we bail.  Note that this can leave
391 			 * the key in a inconsistent state if the caller
392 			 * continues to use it.
393 			 */
394 			if ((key->wk_flags & IEEE80211_KEY_SWCRYPT) == 0) {
395 				ic->ic_stats.is_crypto_swfallback++;
396 				IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
397 				    "%s: no h/w resources for cipher %s, "
398 				    "falling back to s/w\n", __func__,
399 				    cip->ic_name);
400 				oflags = key->wk_flags;
401 				flags |= IEEE80211_KEY_SWCRYPT;
402 				if (cipher == IEEE80211_CIPHER_TKIP)
403 					flags |= IEEE80211_KEY_SWMIC;
404 				goto again;
405 			}
406 			ic->ic_stats.is_crypto_keyfail++;
407 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
408 			    "%s: unable to setup cipher %s\n",
409 			    __func__, cip->ic_name);
410 			return 0;
411 		}
412 		key->wk_keyix = keyix;
413 		key->wk_rxkeyix = rxkeyix;
414 	}
415 	return 1;
416 #undef N
417 }
418 
419 /*
420  * Remove the key (no locking, for internal use).
421  */
422 static int
423 _ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
424 {
425 	ieee80211_keyix keyix;
426 
427 	IASSERT(key->wk_cipher != NULL, ("No cipher!"));
428 
429 	IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
430 	    "%s: %s keyix %u flags 0x%x rsc %ju tsc %ju len %u\n",
431 	    __func__, key->wk_cipher->ic_name,
432 	    key->wk_keyix, key->wk_flags,
433 	    key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);
434 
435 	keyix = key->wk_keyix;
436 	if (keyix != IEEE80211_KEYIX_NONE) {
437 		/*
438 		 * Remove hardware entry.
439 		 */
440 		/* XXX key cache */
441 		if (!dev_key_delete(ic, key)) {
442 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
443 			    "%s: driver did not delete key index %u\n",
444 			    __func__, keyix);
445 			ic->ic_stats.is_crypto_delkey++;
446 			/* XXX recovery? */
447 		}
448 	}
449 	cipher_detach(key);
450 	memset(key, 0, sizeof(*key));
451 	ieee80211_crypto_resetkey(ic, key, IEEE80211_KEYIX_NONE);
452 	return 1;
453 }
454 
455 /*
456  * Remove the specified key.
457  */
458 int
459 ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
460 {
461 	int status;
462 
463 	ieee80211_key_update_begin(ic);
464 	status = _ieee80211_crypto_delkey(ic, key);
465 	ieee80211_key_update_end(ic);
466 	return status;
467 }
468 
469 /*
470  * Clear the global key table.
471  */
472 void
473 ieee80211_crypto_delglobalkeys(struct ieee80211com *ic)
474 {
475 	int i;
476 
477 	ieee80211_key_update_begin(ic);
478 	for (i = 0; i < IEEE80211_WEP_NKID; i++)
479 		(void) _ieee80211_crypto_delkey(ic, &ic->ic_nw_keys[i]);
480 	ieee80211_key_update_end(ic);
481 }
482 
483 /*
484  * Set the contents of the specified key.
485  *
486  * Locking must be handled by the caller using:
487  *	ieee80211_key_update_begin(ic);
488  *	ieee80211_key_update_end(ic);
489  */
490 int
491 ieee80211_crypto_setkey(struct ieee80211com *ic, struct ieee80211_key *key,
492 		const u_int8_t macaddr[IEEE80211_ADDR_LEN])
493 {
494 	const struct ieee80211_cipher *cip = key->wk_cipher;
495 
496 	IASSERT(cip != NULL, ("No cipher!"));
497 
498 	IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
499 	    "%s: %s keyix %u flags 0x%x mac %s rsc %ju tsc %ju len %u\n",
500 	    __func__, cip->ic_name, key->wk_keyix,
501 	    key->wk_flags, ether_sprintf(macaddr),
502 	    key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);
503 
504 	/*
505 	 * Give cipher a chance to validate key contents.
506 	 * XXX should happen before modifying state.
507 	 */
508 	if (!cip->ic_setkey(key)) {
509 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
510 		    "%s: cipher %s rejected key index %u len %u flags 0x%x\n",
511 		    __func__, cip->ic_name, key->wk_keyix,
512 		    key->wk_keylen, key->wk_flags);
513 		ic->ic_stats.is_crypto_setkey_cipher++;
514 		return 0;
515 	}
516 	if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
517 		/* XXX nothing allocated, should not happen */
518 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
519 		    "%s: no key index; should not happen!\n", __func__);
520 		ic->ic_stats.is_crypto_setkey_nokey++;
521 		return 0;
522 	}
523 	return dev_key_set(ic, key, macaddr);
524 }
525 
526 /*
527  * Add privacy headers appropriate for the specified key.
528  */
529 struct ieee80211_key *
530 ieee80211_crypto_encap(struct ieee80211com *ic,
531 	struct ieee80211_node *ni, struct mbuf *m)
532 {
533 	struct ieee80211_key *k;
534 	struct ieee80211_frame *wh;
535 	const struct ieee80211_cipher *cip;
536 	u_int8_t keyid;
537 
538 	/*
539 	 * Multicast traffic always uses the multicast key.
540 	 * Otherwise if a unicast key is set we use that and
541 	 * it is always key index 0.  When no unicast key is
542 	 * set we fall back to the default transmit key.
543 	 */
544 	wh = mtod(m, struct ieee80211_frame *);
545 	if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
546 	    ni->ni_ucastkey.wk_cipher == &ieee80211_cipher_none) {
547 		if (ic->ic_def_txkey == IEEE80211_KEYIX_NONE) {
548 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
549 			    "[%s] no default transmit key (%s) deftxkey %u\n",
550 			    ether_sprintf(wh->i_addr1), __func__,
551 			    ic->ic_def_txkey);
552 			ic->ic_stats.is_tx_nodefkey++;
553 			return NULL;
554 		}
555 		keyid = ic->ic_def_txkey;
556 		k = &ic->ic_nw_keys[ic->ic_def_txkey];
557 	} else {
558 		keyid = 0;
559 		k = &ni->ni_ucastkey;
560 	}
561 	cip = k->wk_cipher;
562 	return (cip->ic_encap(k, m, keyid<<6) ? k : NULL);
563 }
564 
565 /*
566  * Validate and strip privacy headers (and trailer) for a
567  * received frame that has the WEP/Privacy bit set.
568  */
569 struct ieee80211_key *
570 ieee80211_crypto_decap(struct ieee80211com *ic,
571 	struct ieee80211_node *ni, struct mbuf *m, int hdrlen)
572 {
573 #define	IEEE80211_WEP_HDRLEN	(IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN)
574 #define	IEEE80211_WEP_MINLEN \
575 	(sizeof(struct ieee80211_frame) + \
576 	IEEE80211_WEP_HDRLEN + IEEE80211_WEP_CRCLEN)
577 	struct ieee80211_key *k;
578 	struct ieee80211_frame *wh;
579 	const struct ieee80211_cipher *cip;
580 	const u_int8_t *ivp;
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 	ivp = mtod(m, const u_int8_t *) + hdrlen;	/* XXX contig */
600 	keyid = ivp[IEEE80211_WEP_IVLEN];
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 0;
618 	}
619 
620 	return (cip->ic_decap(k, m, hdrlen) ? k : NULL);
621 #undef IEEE80211_WEP_MINLEN
622 #undef IEEE80211_WEP_HDRLEN
623 }
624