xref: /netbsd-src/sys/net80211/ieee80211_crypto.c (revision 6a493d6bc668897c91594964a732d38505b70cbb)
1 /*	$NetBSD: ieee80211_crypto.c,v 1.16 2013/09/13 20:19:53 joerg 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 1.16 2013/09/13 20:19:53 joerg 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 /*
132  * Wrappers for driver key management methods.
133  */
134 static __inline int
135 dev_key_alloc(struct ieee80211com *ic,
136 	const struct ieee80211_key *key,
137 	ieee80211_keyix *keyix, ieee80211_keyix *rxkeyix)
138 {
139 	return ic->ic_crypto.cs_key_alloc(ic, key, keyix, rxkeyix);
140 }
141 
142 static __inline int
143 dev_key_delete(struct ieee80211com *ic,
144 	const struct ieee80211_key *key)
145 {
146 	return ic->ic_crypto.cs_key_delete(ic, key);
147 }
148 
149 static __inline int
150 dev_key_set(struct ieee80211com *ic, const struct ieee80211_key *key,
151 	const u_int8_t mac[IEEE80211_ADDR_LEN])
152 {
153 	return ic->ic_crypto.cs_key_set(ic, key, mac);
154 }
155 
156 /*
157  * Setup crypto support.
158  */
159 void
160 ieee80211_crypto_attach(struct ieee80211com *ic)
161 {
162 	struct ieee80211_crypto_state *cs = &ic->ic_crypto;
163 	int i;
164 
165 	/* NB: we assume everything is pre-zero'd */
166 	cs->cs_def_txkey = IEEE80211_KEYIX_NONE;
167 	cs->cs_max_keyix = IEEE80211_WEP_NKID;
168 	ciphers[IEEE80211_CIPHER_NONE] = &ieee80211_cipher_none;
169 	for (i = 0; i < IEEE80211_WEP_NKID; i++)
170 		ieee80211_crypto_resetkey(ic, &cs->cs_nw_keys[i],
171 			IEEE80211_KEYIX_NONE);
172 	/*
173 	 * Initialize the driver key support routines to noop entries.
174 	 * This is useful especially for the cipher test modules.
175 	 */
176 	cs->cs_key_alloc = null_key_alloc;
177 	cs->cs_key_set = null_key_set;
178 	cs->cs_key_delete = null_key_delete;
179 	cs->cs_key_update_begin = null_key_update;
180 	cs->cs_key_update_end = null_key_update;
181 }
182 
183 /*
184  * Teardown crypto support.
185  */
186 void
187 ieee80211_crypto_detach(struct ieee80211com *ic)
188 {
189 	ieee80211_crypto_delglobalkeys(ic);
190 }
191 
192 /*
193  * Register a crypto cipher module.
194  */
195 void
196 ieee80211_crypto_register(const struct ieee80211_cipher *cip)
197 {
198 	if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
199 		printf("%s: cipher %s has an invalid cipher index %u\n",
200 			__func__, cip->ic_name, cip->ic_cipher);
201 		return;
202 	}
203 	if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
204 		printf("%s: cipher %s registered with a different template\n",
205 			__func__, cip->ic_name);
206 		return;
207 	}
208 	ciphers[cip->ic_cipher] = cip;
209 }
210 
211 /*
212  * Unregister a crypto cipher module.
213  */
214 void
215 ieee80211_crypto_unregister(const struct ieee80211_cipher *cip)
216 {
217 	if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
218 		printf("%s: cipher %s has an invalid cipher index %u\n",
219 			__func__, cip->ic_name, cip->ic_cipher);
220 		return;
221 	}
222 	if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
223 		printf("%s: cipher %s registered with a different template\n",
224 			__func__, cip->ic_name);
225 		return;
226 	}
227 	/* NB: don't complain about not being registered */
228 	/* XXX disallow if references */
229 	ciphers[cip->ic_cipher] = NULL;
230 }
231 
232 int
233 ieee80211_crypto_available(u_int cipher)
234 {
235 	return cipher < IEEE80211_CIPHER_MAX && ciphers[cipher] != NULL;
236 }
237 
238 /* XXX well-known names! */
239 static const char *cipher_modnames[] = {
240 	"wlan_wep",	/* IEEE80211_CIPHER_WEP */
241 	"wlan_tkip",	/* IEEE80211_CIPHER_TKIP */
242 	"wlan_aes_ocb",	/* IEEE80211_CIPHER_AES_OCB */
243 	"wlan_ccmp",	/* IEEE80211_CIPHER_AES_CCM */
244 	"wlan_ckip",	/* IEEE80211_CIPHER_CKIP */
245 };
246 
247 /*
248  * Establish a relationship between the specified key and cipher
249  * and, if necessary, allocate a hardware index from the driver.
250  * Note that when a fixed key index is required it must be specified
251  * and we blindly assign it w/o consulting the driver (XXX).
252  *
253  * This must be the first call applied to a key; all the other key
254  * routines assume wk_cipher is setup.
255  *
256  * Locking must be handled by the caller using:
257  *	ieee80211_key_update_begin(ic);
258  *	ieee80211_key_update_end(ic);
259  */
260 int
261 ieee80211_crypto_newkey(struct ieee80211com *ic,
262 	int cipher, int flags, struct ieee80211_key *key)
263 {
264 #define	N(a)	(sizeof(a) / sizeof(a[0]))
265 	const struct ieee80211_cipher *cip;
266 	ieee80211_keyix keyix, rxkeyix;
267 	void *keyctx;
268 	int oflags;
269 
270 	/*
271 	 * Validate cipher and set reference to cipher routines.
272 	 */
273 	if (cipher >= IEEE80211_CIPHER_MAX) {
274 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
275 			"%s: invalid cipher %u\n", __func__, cipher);
276 		ic->ic_stats.is_crypto_badcipher++;
277 		return 0;
278 	}
279 	cip = ciphers[cipher];
280 	if (cip == NULL) {
281 		/*
282 		 * Auto-load cipher module if we have a well-known name
283 		 * for it.  It might be better to use string names rather
284 		 * than numbers and craft a module name based on the cipher
285 		 * name; e.g. wlan_cipher_<cipher-name>.
286 		 */
287 		if (cipher < N(cipher_modnames)) {
288 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
289 				"%s: unregistered cipher %u, load module %s\n",
290 				__func__, cipher, cipher_modnames[cipher]);
291 			ieee80211_load_module(cipher_modnames[cipher]);
292 			/*
293 			 * If cipher module loaded it should immediately
294 			 * call ieee80211_crypto_register which will fill
295 			 * in the entry in the ciphers array.
296 			 */
297 			cip = ciphers[cipher];
298 		}
299 		if (cip == NULL) {
300 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
301 				"%s: unable to load cipher %u, module %s\n",
302 				__func__, cipher,
303 				cipher < N(cipher_modnames) ?
304 					cipher_modnames[cipher] : "<unknown>");
305 			ic->ic_stats.is_crypto_nocipher++;
306 			return 0;
307 		}
308 	}
309 
310 	oflags = key->wk_flags;
311 	flags &= IEEE80211_KEY_COMMON;
312 	/*
313 	 * If the hardware does not support the cipher then
314 	 * fallback to a host-based implementation.
315 	 */
316 	if ((ic->ic_caps & (1<<cipher)) == 0) {
317 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
318 		    "%s: no h/w support for cipher %s, falling back to s/w\n",
319 		    __func__, cip->ic_name);
320 		flags |= IEEE80211_KEY_SWCRYPT;
321 	}
322 	/*
323 	 * Hardware TKIP with software MIC is an important
324 	 * combination; we handle it by flagging each key,
325 	 * the cipher modules honor it.
326 	 */
327 	if (cipher == IEEE80211_CIPHER_TKIP &&
328 	    (ic->ic_caps & IEEE80211_C_TKIPMIC) == 0) {
329 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
330 		    "%s: no h/w support for TKIP MIC, falling back to s/w\n",
331 		    __func__);
332 		flags |= IEEE80211_KEY_SWMIC;
333 	}
334 
335 	/*
336 	 * Bind cipher to key instance.  Note we do this
337 	 * after checking the device capabilities so the
338 	 * cipher module can optimize space usage based on
339 	 * whether or not it needs to do the cipher work.
340 	 */
341 	if (key->wk_cipher != cip || key->wk_flags != flags) {
342 again:
343 		/*
344 		 * Fillin the flags so cipher modules can see s/w
345 		 * crypto requirements and potentially allocate
346 		 * different state and/or attach different method
347 		 * pointers.
348 		 *
349 		 * XXX this is not right when s/w crypto fallback
350 		 *     fails and we try to restore previous state.
351 		 */
352 		key->wk_flags = flags;
353 		keyctx = cip->ic_attach(ic, key);
354 		if (keyctx == NULL) {
355 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
356 				"%s: unable to attach cipher %s\n",
357 				__func__, cip->ic_name);
358 			key->wk_flags = oflags;	/* restore old flags */
359 			ic->ic_stats.is_crypto_attachfail++;
360 			return 0;
361 		}
362 		cipher_detach(key);
363 		key->wk_cipher = cip;		/* XXX refcnt? */
364 		key->wk_private = keyctx;
365 	}
366 	/*
367 	 * Commit to requested usage so driver can see the flags.
368 	 */
369 	key->wk_flags = flags;
370 
371 	/*
372 	 * Ask the driver for a key index if we don't have one.
373 	 * Note that entries in the global key table always have
374 	 * an index; this means it's safe to call this routine
375 	 * for these entries just to setup the reference to the
376 	 * cipher template.  Note also that when using software
377 	 * crypto we also call the driver to give us a key index.
378 	 */
379 	if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
380 		if (!dev_key_alloc(ic, key, &keyix, &rxkeyix)) {
381 			/*
382 			 * Driver has no room; fallback to doing crypto
383 			 * in the host.  We change the flags and start the
384 			 * procedure over.  If we get back here then there's
385 			 * no hope and we bail.  Note that this can leave
386 			 * the key in a inconsistent state if the caller
387 			 * continues to use it.
388 			 */
389 			if ((key->wk_flags & IEEE80211_KEY_SWCRYPT) == 0) {
390 				ic->ic_stats.is_crypto_swfallback++;
391 				IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
392 				    "%s: no h/w resources for cipher %s, "
393 				    "falling back to s/w\n", __func__,
394 				    cip->ic_name);
395 				oflags = key->wk_flags;
396 				flags |= IEEE80211_KEY_SWCRYPT;
397 				if (cipher == IEEE80211_CIPHER_TKIP)
398 					flags |= IEEE80211_KEY_SWMIC;
399 				goto again;
400 			}
401 			ic->ic_stats.is_crypto_keyfail++;
402 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
403 			    "%s: unable to setup cipher %s\n",
404 			    __func__, cip->ic_name);
405 			return 0;
406 		}
407 		key->wk_keyix = keyix;
408 		key->wk_rxkeyix = rxkeyix;
409 	}
410 	return 1;
411 #undef N
412 }
413 
414 /*
415  * Remove the key (no locking, for internal use).
416  */
417 static int
418 _ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
419 {
420 	ieee80211_keyix keyix;
421 
422 	IASSERT(key->wk_cipher != NULL, ("No cipher!"));
423 
424 	IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
425 	    "%s: %s keyix %u flags 0x%x rsc %ju tsc %ju len %u\n",
426 	    __func__, key->wk_cipher->ic_name,
427 	    key->wk_keyix, key->wk_flags,
428 	    key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);
429 
430 	keyix = key->wk_keyix;
431 	if (keyix != IEEE80211_KEYIX_NONE) {
432 		/*
433 		 * Remove hardware entry.
434 		 */
435 		/* XXX key cache */
436 		if (!dev_key_delete(ic, key)) {
437 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
438 			    "%s: driver did not delete key index %u\n",
439 			    __func__, keyix);
440 			ic->ic_stats.is_crypto_delkey++;
441 			/* XXX recovery? */
442 		}
443 	}
444 	cipher_detach(key);
445 	memset(key, 0, sizeof(*key));
446 	ieee80211_crypto_resetkey(ic, key, IEEE80211_KEYIX_NONE);
447 	return 1;
448 }
449 
450 /*
451  * Remove the specified key.
452  */
453 int
454 ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
455 {
456 	int status;
457 
458 	ieee80211_key_update_begin(ic);
459 	status = _ieee80211_crypto_delkey(ic, key);
460 	ieee80211_key_update_end(ic);
461 	return status;
462 }
463 
464 /*
465  * Clear the global key table.
466  */
467 void
468 ieee80211_crypto_delglobalkeys(struct ieee80211com *ic)
469 {
470 	int i;
471 
472 	ieee80211_key_update_begin(ic);
473 	for (i = 0; i < IEEE80211_WEP_NKID; i++)
474 		(void) _ieee80211_crypto_delkey(ic, &ic->ic_nw_keys[i]);
475 	ieee80211_key_update_end(ic);
476 }
477 
478 /*
479  * Set the contents of the specified key.
480  *
481  * Locking must be handled by the caller using:
482  *	ieee80211_key_update_begin(ic);
483  *	ieee80211_key_update_end(ic);
484  */
485 int
486 ieee80211_crypto_setkey(struct ieee80211com *ic, struct ieee80211_key *key,
487 		const u_int8_t macaddr[IEEE80211_ADDR_LEN])
488 {
489 	const struct ieee80211_cipher *cip = key->wk_cipher;
490 
491 	IASSERT(cip != NULL, ("No cipher!"));
492 
493 	IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
494 	    "%s: %s keyix %u flags 0x%x mac %s rsc %ju tsc %ju len %u\n",
495 	    __func__, cip->ic_name, key->wk_keyix,
496 	    key->wk_flags, ether_sprintf(macaddr),
497 	    key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);
498 
499 	/*
500 	 * Give cipher a chance to validate key contents.
501 	 * XXX should happen before modifying state.
502 	 */
503 	if (!cip->ic_setkey(key)) {
504 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
505 		    "%s: cipher %s rejected key index %u len %u flags 0x%x\n",
506 		    __func__, cip->ic_name, key->wk_keyix,
507 		    key->wk_keylen, key->wk_flags);
508 		ic->ic_stats.is_crypto_setkey_cipher++;
509 		return 0;
510 	}
511 	if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
512 		/* XXX nothing allocated, should not happen */
513 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
514 		    "%s: no key index; should not happen!\n", __func__);
515 		ic->ic_stats.is_crypto_setkey_nokey++;
516 		return 0;
517 	}
518 	return dev_key_set(ic, key, macaddr);
519 }
520 
521 /*
522  * Add privacy headers appropriate for the specified key.
523  */
524 struct ieee80211_key *
525 ieee80211_crypto_encap(struct ieee80211com *ic,
526 	struct ieee80211_node *ni, struct mbuf *m)
527 {
528 	struct ieee80211_key *k;
529 	struct ieee80211_frame *wh;
530 	const struct ieee80211_cipher *cip;
531 	u_int8_t keyid;
532 
533 	/*
534 	 * Multicast traffic always uses the multicast key.
535 	 * Otherwise if a unicast key is set we use that and
536 	 * it is always key index 0.  When no unicast key is
537 	 * set we fall back to the default transmit key.
538 	 */
539 	wh = mtod(m, struct ieee80211_frame *);
540 	if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
541 	    ni->ni_ucastkey.wk_cipher == &ieee80211_cipher_none) {
542 		if (ic->ic_def_txkey == IEEE80211_KEYIX_NONE) {
543 			IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
544 			    "[%s] no default transmit key (%s) deftxkey %u\n",
545 			    ether_sprintf(wh->i_addr1), __func__,
546 			    ic->ic_def_txkey);
547 			ic->ic_stats.is_tx_nodefkey++;
548 			return NULL;
549 		}
550 		keyid = ic->ic_def_txkey;
551 		k = &ic->ic_nw_keys[ic->ic_def_txkey];
552 	} else {
553 		keyid = 0;
554 		k = &ni->ni_ucastkey;
555 	}
556 	cip = k->wk_cipher;
557 	return (cip->ic_encap(k, m, keyid<<6) ? k : NULL);
558 }
559 
560 /*
561  * Validate and strip privacy headers (and trailer) for a
562  * received frame that has the WEP/Privacy bit set.
563  */
564 struct ieee80211_key *
565 ieee80211_crypto_decap(struct ieee80211com *ic,
566 	struct ieee80211_node *ni, struct mbuf *m, int hdrlen)
567 {
568 #define	IEEE80211_WEP_HDRLEN	(IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN)
569 #define	IEEE80211_WEP_MINLEN \
570 	(sizeof(struct ieee80211_frame) + \
571 	IEEE80211_WEP_HDRLEN + IEEE80211_WEP_CRCLEN)
572 	struct ieee80211_key *k;
573 	struct ieee80211_frame *wh;
574 	const struct ieee80211_cipher *cip;
575 	u_int8_t keyid;
576 
577 	/* NB: this minimum size data frame could be bigger */
578 	if (m->m_pkthdr.len < IEEE80211_WEP_MINLEN) {
579 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_ANY,
580 			"%s: WEP data frame too short, len %u\n",
581 			__func__, m->m_pkthdr.len);
582 		ic->ic_stats.is_rx_tooshort++;	/* XXX need unique stat? */
583 		return NULL;
584 	}
585 
586 	/*
587 	 * Locate the key. If unicast and there is no unicast
588 	 * key then we fall back to the key id in the header.
589 	 * This assumes unicast keys are only configured when
590 	 * the key id in the header is meaningless (typically 0).
591 	 */
592 	wh = mtod(m, struct ieee80211_frame *);
593 	m_copydata(m, hdrlen + IEEE80211_WEP_IVLEN, sizeof(keyid), &keyid);
594 	if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
595 	    ni->ni_ucastkey.wk_cipher == &ieee80211_cipher_none)
596 		k = &ic->ic_nw_keys[keyid >> 6];
597 	else
598 		k = &ni->ni_ucastkey;
599 
600 	/*
601 	 * Insure crypto header is contiguous for all decap work.
602 	 */
603 	cip = k->wk_cipher;
604 	if (m->m_len < hdrlen + cip->ic_header &&
605 	    (m = m_pullup(m, hdrlen + cip->ic_header)) == NULL) {
606 		IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
607 		    "[%s] unable to pullup %s header\n",
608 		    ether_sprintf(wh->i_addr2), cip->ic_name);
609 		ic->ic_stats.is_rx_wepfail++;	/* XXX */
610 		return NULL;
611 	}
612 
613 	return (cip->ic_decap(k, m, hdrlen) ? k : NULL);
614 #undef IEEE80211_WEP_MINLEN
615 #undef IEEE80211_WEP_HDRLEN
616 }
617