xref: /openbsd-src/sys/net80211/ieee80211_crypto.c (revision 99fd087599a8791921855f21bd7e36130f39aadc) 
1 /*	$OpenBSD: ieee80211_crypto.c,v 1.75 2019/08/16 19:53:32 procter Exp $	*/
2 
3 /*-
4  * Copyright (c) 2008 Damien Bergamini <damien.bergamini@free.fr>
5  *
6  * Permission to use, copy, modify, and distribute this software for any
7  * purpose with or without fee is hereby granted, provided that the above
8  * copyright notice and this permission notice appear in all copies.
9  *
10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17  */
18 
19 #include <sys/param.h>
20 #include <sys/systm.h>
21 #include <sys/mbuf.h>
22 #include <sys/malloc.h>
23 #include <sys/kernel.h>
24 #include <sys/socket.h>
25 #include <sys/sockio.h>
26 #include <sys/endian.h>
27 #include <sys/errno.h>
28 #include <sys/sysctl.h>
29 
30 #include <net/if.h>
31 #include <net/if_dl.h>
32 #include <net/if_media.h>
33 
34 #include <netinet/in.h>
35 #include <netinet/if_ether.h>
36 
37 #include <net80211/ieee80211_var.h>
38 #include <net80211/ieee80211_priv.h>
39 
40 #include <crypto/arc4.h>
41 #include <crypto/md5.h>
42 #include <crypto/sha1.h>
43 #include <crypto/sha2.h>
44 #include <crypto/hmac.h>
45 #include <crypto/aes.h>
46 #include <crypto/cmac.h>
47 #include <crypto/key_wrap.h>
48 
49 void	ieee80211_prf(const u_int8_t *, size_t, const u_int8_t *, size_t,
50 	    const u_int8_t *, size_t, u_int8_t *, size_t);
51 void	ieee80211_kdf(const u_int8_t *, size_t, const u_int8_t *, size_t,
52 	    const u_int8_t *, size_t, u_int8_t *, size_t);
53 void	ieee80211_derive_pmkid(enum ieee80211_akm, const u_int8_t *,
54 	    const u_int8_t *, const u_int8_t *, u_int8_t *);
55 
56 void
57 ieee80211_crypto_attach(struct ifnet *ifp)
58 {
59 	struct ieee80211com *ic = (void *)ifp;
60 
61 	TAILQ_INIT(&ic->ic_pmksa);
62 	if (ic->ic_caps & IEEE80211_C_RSN) {
63 		ic->ic_rsnprotos = IEEE80211_PROTO_RSN;
64 		ic->ic_rsnakms = IEEE80211_AKM_PSK;
65 		ic->ic_rsnciphers = IEEE80211_CIPHER_CCMP;
66 		ic->ic_rsngroupcipher = IEEE80211_CIPHER_CCMP;
67 		ic->ic_rsngroupmgmtcipher = IEEE80211_CIPHER_BIP;
68 	}
69 	ic->ic_set_key = ieee80211_set_key;
70 	ic->ic_delete_key = ieee80211_delete_key;
71 #ifndef IEEE80211_STA_ONLY
72 	timeout_set(&ic->ic_tkip_micfail_timeout,
73 	    ieee80211_michael_mic_failure_timeout, ic);
74 #endif
75 }
76 
77 void
78 ieee80211_crypto_detach(struct ifnet *ifp)
79 {
80 	struct ieee80211com *ic = (void *)ifp;
81 	struct ieee80211_pmk *pmk;
82 
83 	/* purge the PMKSA cache */
84 	while ((pmk = TAILQ_FIRST(&ic->ic_pmksa)) != NULL) {
85 		TAILQ_REMOVE(&ic->ic_pmksa, pmk, pmk_next);
86 		explicit_bzero(pmk, sizeof(*pmk));
87 		free(pmk, M_DEVBUF, sizeof(*pmk));
88 	}
89 
90 	/* clear all group keys from memory */
91 	ieee80211_crypto_clear_groupkeys(ic);
92 
93 	/* clear pre-shared key from memory */
94 	explicit_bzero(ic->ic_psk, IEEE80211_PMK_LEN);
95 
96 #ifndef IEEE80211_STA_ONLY
97 	timeout_del(&ic->ic_tkip_micfail_timeout);
98 #endif
99 }
100 
101 void
102 ieee80211_crypto_clear_groupkeys(struct ieee80211com *ic)
103 {
104 	int i;
105 
106 	for (i = 0; i < IEEE80211_GROUP_NKID; i++) {
107 		struct ieee80211_key *k = &ic->ic_nw_keys[i];
108 		if (k->k_cipher != IEEE80211_CIPHER_NONE)
109 			(*ic->ic_delete_key)(ic, NULL, k);
110 		explicit_bzero(k, sizeof(*k));
111 	}
112 }
113 
114 /*
115  * Return the length in bytes of a cipher suite key (see Table 60).
116  */
117 int
118 ieee80211_cipher_keylen(enum ieee80211_cipher cipher)
119 {
120 	switch (cipher) {
121 	case IEEE80211_CIPHER_WEP40:
122 		return 5;
123 	case IEEE80211_CIPHER_TKIP:
124 		return 32;
125 	case IEEE80211_CIPHER_CCMP:
126 		return 16;
127 	case IEEE80211_CIPHER_WEP104:
128 		return 13;
129 	case IEEE80211_CIPHER_BIP:
130 		return 16;
131 	default:	/* unknown cipher */
132 		return 0;
133 	}
134 }
135 
136 int
137 ieee80211_set_key(struct ieee80211com *ic, struct ieee80211_node *ni,
138     struct ieee80211_key *k)
139 {
140 	int error;
141 
142 	switch (k->k_cipher) {
143 	case IEEE80211_CIPHER_WEP40:
144 	case IEEE80211_CIPHER_WEP104:
145 		error = ieee80211_wep_set_key(ic, k);
146 		break;
147 	case IEEE80211_CIPHER_TKIP:
148 		error = ieee80211_tkip_set_key(ic, k);
149 		break;
150 	case IEEE80211_CIPHER_CCMP:
151 		error = ieee80211_ccmp_set_key(ic, k);
152 		break;
153 	case IEEE80211_CIPHER_BIP:
154 		error = ieee80211_bip_set_key(ic, k);
155 		break;
156 	default:
157 		/* should not get there */
158 		error = EINVAL;
159 	}
160 
161 	if (error == 0)
162 		k->k_flags |= IEEE80211_KEY_SWCRYPTO;
163 
164 	return error;
165 }
166 
167 void
168 ieee80211_delete_key(struct ieee80211com *ic, struct ieee80211_node *ni,
169     struct ieee80211_key *k)
170 {
171 	switch (k->k_cipher) {
172 	case IEEE80211_CIPHER_WEP40:
173 	case IEEE80211_CIPHER_WEP104:
174 		ieee80211_wep_delete_key(ic, k);
175 		break;
176 	case IEEE80211_CIPHER_TKIP:
177 		ieee80211_tkip_delete_key(ic, k);
178 		break;
179 	case IEEE80211_CIPHER_CCMP:
180 		ieee80211_ccmp_delete_key(ic, k);
181 		break;
182 	case IEEE80211_CIPHER_BIP:
183 		ieee80211_bip_delete_key(ic, k);
184 		break;
185 	default:
186 		/* should not get there */
187 		break;
188 	}
189 	explicit_bzero(k, sizeof(*k));
190 }
191 
192 struct ieee80211_key *
193 ieee80211_get_txkey(struct ieee80211com *ic, const struct ieee80211_frame *wh,
194     struct ieee80211_node *ni)
195 {
196 	int kid;
197 
198 	if ((ic->ic_flags & IEEE80211_F_RSNON) &&
199 	    !IEEE80211_IS_MULTICAST(wh->i_addr1) &&
200 	    ni->ni_rsncipher != IEEE80211_CIPHER_USEGROUP)
201 		return &ni->ni_pairwise_key;
202 
203 	/* All other cases (including WEP) use a group key. */
204 	if (ni->ni_flags & IEEE80211_NODE_MFP)
205 		kid = ic->ic_igtk_kid;
206 	else
207 		kid = ic->ic_def_txkey;
208 
209 	return &ic->ic_nw_keys[kid];
210 }
211 
212 struct mbuf *
213 ieee80211_encrypt(struct ieee80211com *ic, struct mbuf *m0,
214     struct ieee80211_key *k)
215 {
216 	if ((k->k_flags & IEEE80211_KEY_SWCRYPTO) == 0)
217 		panic("%s: key unset for sw crypto: %d", __func__, k->k_id);
218 
219 	switch (k->k_cipher) {
220 	case IEEE80211_CIPHER_WEP40:
221 	case IEEE80211_CIPHER_WEP104:
222 		m0 = ieee80211_wep_encrypt(ic, m0, k);
223 		break;
224 	case IEEE80211_CIPHER_TKIP:
225 		m0 = ieee80211_tkip_encrypt(ic, m0, k);
226 		break;
227 	case IEEE80211_CIPHER_CCMP:
228 		m0 = ieee80211_ccmp_encrypt(ic, m0, k);
229 		break;
230 	case IEEE80211_CIPHER_BIP:
231 		m0 = ieee80211_bip_encap(ic, m0, k);
232 		break;
233 	default:
234 		/* should not get there */
235 		panic("invalid key cipher 0x%x", k->k_cipher);
236 	}
237 	return m0;
238 }
239 
240 struct mbuf *
241 ieee80211_decrypt(struct ieee80211com *ic, struct mbuf *m0,
242     struct ieee80211_node *ni)
243 {
244 	struct ieee80211_frame *wh;
245 	struct ieee80211_key *k;
246 	u_int8_t *ivp, *mmie;
247 	u_int16_t kid;
248 	int hdrlen;
249 
250 	/* find key for decryption */
251 	wh = mtod(m0, struct ieee80211_frame *);
252 	if ((ic->ic_flags & IEEE80211_F_RSNON) &&
253 	    !IEEE80211_IS_MULTICAST(wh->i_addr1) &&
254 	    ni->ni_rsncipher != IEEE80211_CIPHER_USEGROUP) {
255 		k = &ni->ni_pairwise_key;
256 
257 	} else if (!IEEE80211_IS_MULTICAST(wh->i_addr1) ||
258 	    (wh->i_fc[0] & IEEE80211_FC0_TYPE_MASK) !=
259 	    IEEE80211_FC0_TYPE_MGT) {
260 		/* retrieve group data key id from IV field */
261 		hdrlen = ieee80211_get_hdrlen(wh);
262 		/* check that IV field is present */
263 		if (m0->m_len < hdrlen + 4) {
264 			m_freem(m0);
265 			return NULL;
266 		}
267 		ivp = (u_int8_t *)wh + hdrlen;
268 		kid = ivp[3] >> 6;
269 		k = &ic->ic_nw_keys[kid];
270 	} else {
271 		/* retrieve integrity group key id from MMIE */
272 		if (m0->m_len < sizeof(*wh) + IEEE80211_MMIE_LEN) {
273 			m_freem(m0);
274 			return NULL;
275 		}
276 		/* it is assumed management frames are contiguous */
277 		mmie = (u_int8_t *)wh + m0->m_len - IEEE80211_MMIE_LEN;
278 		/* check that MMIE is valid */
279 		if (mmie[0] != IEEE80211_ELEMID_MMIE || mmie[1] != 16) {
280 			m_freem(m0);
281 			return NULL;
282 		}
283 		kid = LE_READ_2(&mmie[2]);
284 		if (kid != 4 && kid != 5) {
285 			m_freem(m0);
286 			return NULL;
287 		}
288 		k = &ic->ic_nw_keys[kid];
289 	}
290 
291 	if ((k->k_flags & IEEE80211_KEY_SWCRYPTO) == 0) {
292 		m_free(m0);
293 		return NULL;
294 	}
295 
296 	switch (k->k_cipher) {
297 	case IEEE80211_CIPHER_WEP40:
298 	case IEEE80211_CIPHER_WEP104:
299 		m0 = ieee80211_wep_decrypt(ic, m0, k);
300 		break;
301 	case IEEE80211_CIPHER_TKIP:
302 		m0 = ieee80211_tkip_decrypt(ic, m0, k);
303 		break;
304 	case IEEE80211_CIPHER_CCMP:
305 		m0 = ieee80211_ccmp_decrypt(ic, m0, k);
306 		break;
307 	case IEEE80211_CIPHER_BIP:
308 		m0 = ieee80211_bip_decap(ic, m0, k);
309 		break;
310 	default:
311 		/* key not defined */
312 		m_freem(m0);
313 		m0 = NULL;
314 	}
315 	return m0;
316 }
317 
318 /*
319  * SHA1-based Pseudo-Random Function (see 8.5.1.1).
320  */
321 void
322 ieee80211_prf(const u_int8_t *key, size_t key_len, const u_int8_t *label,
323     size_t label_len, const u_int8_t *context, size_t context_len,
324     u_int8_t *output, size_t len)
325 {
326 	HMAC_SHA1_CTX ctx;
327 	u_int8_t digest[SHA1_DIGEST_LENGTH];
328 	u_int8_t count;
329 
330 	for (count = 0; len != 0; count++) {
331 		HMAC_SHA1_Init(&ctx, key, key_len);
332 		HMAC_SHA1_Update(&ctx, label, label_len);
333 		HMAC_SHA1_Update(&ctx, context, context_len);
334 		HMAC_SHA1_Update(&ctx, &count, 1);
335 		if (len < SHA1_DIGEST_LENGTH) {
336 			HMAC_SHA1_Final(digest, &ctx);
337 			/* truncate HMAC-SHA1 to len bytes */
338 			memcpy(output, digest, len);
339 			break;
340 		}
341 		HMAC_SHA1_Final(output, &ctx);
342 		output += SHA1_DIGEST_LENGTH;
343 		len -= SHA1_DIGEST_LENGTH;
344 	}
345 }
346 
347 /*
348  * SHA256-based Key Derivation Function (see 8.5.1.5.2).
349  */
350 void
351 ieee80211_kdf(const u_int8_t *key, size_t key_len, const u_int8_t *label,
352     size_t label_len, const u_int8_t *context, size_t context_len,
353     u_int8_t *output, size_t len)
354 {
355 	HMAC_SHA256_CTX ctx;
356 	u_int8_t digest[SHA256_DIGEST_LENGTH];
357 	u_int16_t i, iter, length;
358 
359 	length = htole16(len * NBBY);
360 	for (i = 1; len != 0; i++) {
361 		HMAC_SHA256_Init(&ctx, key, key_len);
362 		iter = htole16(i);
363 		HMAC_SHA256_Update(&ctx, (u_int8_t *)&iter, sizeof iter);
364 		HMAC_SHA256_Update(&ctx, label, label_len);
365 		HMAC_SHA256_Update(&ctx, context, context_len);
366 		HMAC_SHA256_Update(&ctx, (u_int8_t *)&length, sizeof length);
367 		if (len < SHA256_DIGEST_LENGTH) {
368 			HMAC_SHA256_Final(digest, &ctx);
369 			/* truncate HMAC-SHA-256 to len bytes */
370 			memcpy(output, digest, len);
371 			break;
372 		}
373 		HMAC_SHA256_Final(output, &ctx);
374 		output += SHA256_DIGEST_LENGTH;
375 		len -= SHA256_DIGEST_LENGTH;
376 	}
377 }
378 
379 /*
380  * Derive Pairwise Transient Key (PTK) (see 8.5.1.2).
381  */
382 void
383 ieee80211_derive_ptk(enum ieee80211_akm akm, const u_int8_t *pmk,
384     const u_int8_t *aa, const u_int8_t *spa, const u_int8_t *anonce,
385     const u_int8_t *snonce, struct ieee80211_ptk *ptk)
386 {
387 	void (*kdf)(const u_int8_t *, size_t, const u_int8_t *, size_t,
388 	    const u_int8_t *, size_t, u_int8_t *, size_t);
389 	u_int8_t buf[2 * IEEE80211_ADDR_LEN + 2 * EAPOL_KEY_NONCE_LEN];
390 	int ret;
391 
392 	/* Min(AA,SPA) || Max(AA,SPA) */
393 	ret = memcmp(aa, spa, IEEE80211_ADDR_LEN) < 0;
394 	memcpy(&buf[ 0], ret ? aa : spa, IEEE80211_ADDR_LEN);
395 	memcpy(&buf[ 6], ret ? spa : aa, IEEE80211_ADDR_LEN);
396 
397 	/* Min(ANonce,SNonce) || Max(ANonce,SNonce) */
398 	ret = memcmp(anonce, snonce, EAPOL_KEY_NONCE_LEN) < 0;
399 	memcpy(&buf[12], ret ? anonce : snonce, EAPOL_KEY_NONCE_LEN);
400 	memcpy(&buf[44], ret ? snonce : anonce, EAPOL_KEY_NONCE_LEN);
401 
402 	kdf = ieee80211_is_sha256_akm(akm) ? ieee80211_kdf : ieee80211_prf;
403 	(*kdf)(pmk, IEEE80211_PMK_LEN, "Pairwise key expansion", 23,
404 	    buf, sizeof buf, (u_int8_t *)ptk, sizeof(*ptk));
405 }
406 
407 static void
408 ieee80211_pmkid_sha1(const u_int8_t *pmk, const u_int8_t *aa,
409     const u_int8_t *spa, u_int8_t *pmkid)
410 {
411 	HMAC_SHA1_CTX ctx;
412 	u_int8_t digest[SHA1_DIGEST_LENGTH];
413 
414 	HMAC_SHA1_Init(&ctx, pmk, IEEE80211_PMK_LEN);
415 	HMAC_SHA1_Update(&ctx, "PMK Name", 8);
416 	HMAC_SHA1_Update(&ctx, aa, IEEE80211_ADDR_LEN);
417 	HMAC_SHA1_Update(&ctx, spa, IEEE80211_ADDR_LEN);
418 	HMAC_SHA1_Final(digest, &ctx);
419 	/* use the first 128 bits of HMAC-SHA1 */
420 	memcpy(pmkid, digest, IEEE80211_PMKID_LEN);
421 }
422 
423 static void
424 ieee80211_pmkid_sha256(const u_int8_t *pmk, const u_int8_t *aa,
425     const u_int8_t *spa, u_int8_t *pmkid)
426 {
427 	HMAC_SHA256_CTX ctx;
428 	u_int8_t digest[SHA256_DIGEST_LENGTH];
429 
430 	HMAC_SHA256_Init(&ctx, pmk, IEEE80211_PMK_LEN);
431 	HMAC_SHA256_Update(&ctx, "PMK Name", 8);
432 	HMAC_SHA256_Update(&ctx, aa, IEEE80211_ADDR_LEN);
433 	HMAC_SHA256_Update(&ctx, spa, IEEE80211_ADDR_LEN);
434 	HMAC_SHA256_Final(digest, &ctx);
435 	/* use the first 128 bits of HMAC-SHA-256 */
436 	memcpy(pmkid, digest, IEEE80211_PMKID_LEN);
437 }
438 
439 /*
440  * Derive Pairwise Master Key Identifier (PMKID) (see 8.5.1.2).
441  */
442 void
443 ieee80211_derive_pmkid(enum ieee80211_akm akm, const u_int8_t *pmk,
444     const u_int8_t *aa, const u_int8_t *spa, u_int8_t *pmkid)
445 {
446 	if (ieee80211_is_sha256_akm(akm))
447 		ieee80211_pmkid_sha256(pmk, aa, spa, pmkid);
448 	else
449 		ieee80211_pmkid_sha1(pmk, aa, spa, pmkid);
450 }
451 
452 typedef union _ANY_CTX {
453 	HMAC_MD5_CTX	md5;
454 	HMAC_SHA1_CTX	sha1;
455 	AES_CMAC_CTX	cmac;
456 } ANY_CTX;
457 
458 /*
459  * Compute the Key MIC field of an EAPOL-Key frame using the specified Key
460  * Confirmation Key (KCK).  The hash function can be HMAC-MD5, HMAC-SHA1
461  * or AES-128-CMAC depending on the EAPOL-Key Key Descriptor Version.
462  */
463 void
464 ieee80211_eapol_key_mic(struct ieee80211_eapol_key *key, const u_int8_t *kck)
465 {
466 	u_int8_t digest[SHA1_DIGEST_LENGTH];
467 	ANY_CTX ctx;	/* XXX off stack? */
468 	u_int len;
469 
470 	len = BE_READ_2(key->len) + 4;
471 
472 	switch (BE_READ_2(key->info) & EAPOL_KEY_VERSION_MASK) {
473 	case EAPOL_KEY_DESC_V1:
474 		HMAC_MD5_Init(&ctx.md5, kck, 16);
475 		HMAC_MD5_Update(&ctx.md5, (u_int8_t *)key, len);
476 		HMAC_MD5_Final(key->mic, &ctx.md5);
477 		break;
478 	case EAPOL_KEY_DESC_V2:
479 		HMAC_SHA1_Init(&ctx.sha1, kck, 16);
480 		HMAC_SHA1_Update(&ctx.sha1, (u_int8_t *)key, len);
481 		HMAC_SHA1_Final(digest, &ctx.sha1);
482 		/* truncate HMAC-SHA1 to its 128 MSBs */
483 		memcpy(key->mic, digest, EAPOL_KEY_MIC_LEN);
484 		break;
485 	case EAPOL_KEY_DESC_V3:
486 		AES_CMAC_Init(&ctx.cmac);
487 		AES_CMAC_SetKey(&ctx.cmac, kck);
488 		AES_CMAC_Update(&ctx.cmac, (u_int8_t *)key, len);
489 		AES_CMAC_Final(key->mic, &ctx.cmac);
490 		break;
491 	}
492 }
493 
494 /*
495  * Check the MIC of a received EAPOL-Key frame using the specified Key
496  * Confirmation Key (KCK).
497  */
498 int
499 ieee80211_eapol_key_check_mic(struct ieee80211_eapol_key *key,
500     const u_int8_t *kck)
501 {
502 	u_int8_t mic[EAPOL_KEY_MIC_LEN];
503 
504 	memcpy(mic, key->mic, EAPOL_KEY_MIC_LEN);
505 	memset(key->mic, 0, EAPOL_KEY_MIC_LEN);
506 	ieee80211_eapol_key_mic(key, kck);
507 
508 	return timingsafe_bcmp(key->mic, mic, EAPOL_KEY_MIC_LEN) != 0;
509 }
510 
511 #ifndef IEEE80211_STA_ONLY
512 /*
513  * Encrypt the Key Data field of an EAPOL-Key frame using the specified Key
514  * Encryption Key (KEK).  The encryption algorithm can be either ARC4 or
515  * AES Key Wrap depending on the EAPOL-Key Key Descriptor Version.
516  */
517 void
518 ieee80211_eapol_key_encrypt(struct ieee80211com *ic,
519     struct ieee80211_eapol_key *key, const u_int8_t *kek)
520 {
521 	union {
522 		struct rc4_ctx rc4;
523 		aes_key_wrap_ctx aes;
524 	} ctx;	/* XXX off stack? */
525 	u_int8_t keybuf[EAPOL_KEY_IV_LEN + 16];
526 	u_int16_t len, info;
527 	u_int8_t *data;
528 	int n;
529 
530 	len  = BE_READ_2(key->paylen);
531 	info = BE_READ_2(key->info);
532 	data = (u_int8_t *)(key + 1);
533 
534 	switch (info & EAPOL_KEY_VERSION_MASK) {
535 	case EAPOL_KEY_DESC_V1:
536 		/* set IV to the lower 16 octets of our global key counter */
537 		memcpy(key->iv, ic->ic_globalcnt + 16, 16);
538 		/* increment our global key counter (256-bit, big-endian) */
539 		for (n = 31; n >= 0 && ++ic->ic_globalcnt[n] == 0; n--);
540 
541 		/* concatenate the EAPOL-Key IV field and the KEK */
542 		memcpy(keybuf, key->iv, EAPOL_KEY_IV_LEN);
543 		memcpy(keybuf + EAPOL_KEY_IV_LEN, kek, 16);
544 
545 		rc4_keysetup(&ctx.rc4, keybuf, sizeof keybuf);
546 		/* discard the first 256 octets of the ARC4 key stream */
547 		rc4_skip(&ctx.rc4, RC4STATE);
548 		rc4_crypt(&ctx.rc4, data, data, len);
549 		break;
550 	case EAPOL_KEY_DESC_V2:
551 	case EAPOL_KEY_DESC_V3:
552 		if (len < 16 || (len & 7) != 0) {
553 			/* insert padding */
554 			n = (len < 16) ? 16 - len : 8 - (len & 7);
555 			data[len++] = IEEE80211_ELEMID_VENDOR;
556 			memset(&data[len], 0, n - 1);
557 			len += n - 1;
558 		}
559 		aes_key_wrap_set_key_wrap_only(&ctx.aes, kek, 16);
560 		aes_key_wrap(&ctx.aes, data, len / 8, data);
561 		len += 8;	/* AES Key Wrap adds 8 bytes */
562 		/* update key data length */
563 		BE_WRITE_2(key->paylen, len);
564 		/* update packet body length */
565 		BE_WRITE_2(key->len, sizeof(*key) + len - 4);
566 		break;
567 	}
568 }
569 #endif	/* IEEE80211_STA_ONLY */
570 
571 /*
572  * Decrypt the Key Data field of an EAPOL-Key frame using the specified Key
573  * Encryption Key (KEK).  The encryption algorithm can be either ARC4 or
574  * AES Key Wrap depending on the EAPOL-Key Key Descriptor Version.
575  */
576 int
577 ieee80211_eapol_key_decrypt(struct ieee80211_eapol_key *key,
578     const u_int8_t *kek)
579 {
580 	union {
581 		struct rc4_ctx rc4;
582 		aes_key_wrap_ctx aes;
583 	} ctx;	/* XXX off stack? */
584 	u_int8_t keybuf[EAPOL_KEY_IV_LEN + 16];
585 	u_int16_t len, info;
586 	u_int8_t *data;
587 
588 	len  = BE_READ_2(key->paylen);
589 	info = BE_READ_2(key->info);
590 	data = (u_int8_t *)(key + 1);
591 
592 	switch (info & EAPOL_KEY_VERSION_MASK) {
593 	case EAPOL_KEY_DESC_V1:
594 		/* concatenate the EAPOL-Key IV field and the KEK */
595 		memcpy(keybuf, key->iv, EAPOL_KEY_IV_LEN);
596 		memcpy(keybuf + EAPOL_KEY_IV_LEN, kek, 16);
597 
598 		rc4_keysetup(&ctx.rc4, keybuf, sizeof keybuf);
599 		/* discard the first 256 octets of the ARC4 key stream */
600 		rc4_skip(&ctx.rc4, RC4STATE);
601 		rc4_crypt(&ctx.rc4, data, data, len);
602 		return 0;
603 	case EAPOL_KEY_DESC_V2:
604 	case EAPOL_KEY_DESC_V3:
605 		/* Key Data Length must be a multiple of 8 */
606 		if (len < 16 + 8 || (len & 7) != 0)
607 			return 1;
608 		len -= 8;	/* AES Key Wrap adds 8 bytes */
609 		aes_key_wrap_set_key(&ctx.aes, kek, 16);
610 		return aes_key_unwrap(&ctx.aes, data, data, len / 8);
611 	}
612 
613 	return 1;	/* unknown Key Descriptor Version */
614 }
615 
616 /*
617  * Add a PMK entry to the PMKSA cache.
618  */
619 struct ieee80211_pmk *
620 ieee80211_pmksa_add(struct ieee80211com *ic, enum ieee80211_akm akm,
621     const u_int8_t *macaddr, const u_int8_t *key, u_int32_t lifetime)
622 {
623 	struct ieee80211_pmk *pmk;
624 
625 	/* check if an entry already exists for this (STA,AKMP) */
626 	TAILQ_FOREACH(pmk, &ic->ic_pmksa, pmk_next) {
627 		if (pmk->pmk_akm == akm &&
628 		    IEEE80211_ADDR_EQ(pmk->pmk_macaddr, macaddr))
629 			break;
630 	}
631 	if (pmk == NULL) {
632 		/* allocate a new PMKSA entry */
633 		if ((pmk = malloc(sizeof(*pmk), M_DEVBUF, M_NOWAIT)) == NULL)
634 			return NULL;
635 		pmk->pmk_akm = akm;
636 		IEEE80211_ADDR_COPY(pmk->pmk_macaddr, macaddr);
637 		TAILQ_INSERT_TAIL(&ic->ic_pmksa, pmk, pmk_next);
638 	}
639 	memcpy(pmk->pmk_key, key, IEEE80211_PMK_LEN);
640 	pmk->pmk_lifetime = lifetime;	/* XXX not used yet */
641 #ifndef IEEE80211_STA_ONLY
642 	if (ic->ic_opmode == IEEE80211_M_HOSTAP) {
643 		ieee80211_derive_pmkid(pmk->pmk_akm, pmk->pmk_key,
644 		    ic->ic_myaddr, macaddr, pmk->pmk_pmkid);
645 	} else
646 #endif
647 	{
648 		ieee80211_derive_pmkid(pmk->pmk_akm, pmk->pmk_key,
649 		    macaddr, ic->ic_myaddr, pmk->pmk_pmkid);
650 	}
651 	return pmk;
652 }
653 
654 /*
655  * Check if we have a cached PMK entry for the specified node and PMKID.
656  */
657 struct ieee80211_pmk *
658 ieee80211_pmksa_find(struct ieee80211com *ic, struct ieee80211_node *ni,
659     const u_int8_t *pmkid)
660 {
661 	struct ieee80211_pmk *pmk;
662 
663 	TAILQ_FOREACH(pmk, &ic->ic_pmksa, pmk_next) {
664 		if (pmk->pmk_akm == ni->ni_rsnakms &&
665 		    IEEE80211_ADDR_EQ(pmk->pmk_macaddr, ni->ni_macaddr) &&
666 		    (pmkid == NULL ||
667 		     memcmp(pmk->pmk_pmkid, pmkid, IEEE80211_PMKID_LEN) == 0))
668 			break;
669 	}
670 	return pmk;
671 }
672