1 /*
2  * hostapd / EAP-PSK (RFC 4764) server
3  * Copyright (c) 2005-2007, Jouni Malinen <j@w1.fi>
4  *
5  * This software may be distributed under the terms of the BSD license.
6  * See README for more details.
7  *
8  * Note: EAP-PSK is an EAP authentication method and as such, completely
9  * different from WPA-PSK. This file is not needed for WPA-PSK functionality.
10  */
11 
12 #include "includes.h"
13 
14 #include "common.h"
15 #include "crypto/aes_wrap.h"
16 #include "crypto/random.h"
17 #include "eap_common/eap_psk_common.h"
18 #include "eap_server/eap_i.h"
19 
20 
21 struct eap_psk_data {
22 	enum { PSK_1, PSK_3, SUCCESS, FAILURE } state;
23 	u8 rand_s[EAP_PSK_RAND_LEN];
24 	u8 rand_p[EAP_PSK_RAND_LEN];
25 	u8 *id_p;
26 	size_t id_p_len;
27 	u8 ak[EAP_PSK_AK_LEN], kdk[EAP_PSK_KDK_LEN], tek[EAP_PSK_TEK_LEN];
28 	u8 msk[EAP_MSK_LEN];
29 	u8 emsk[EAP_EMSK_LEN];
30 };
31 
32 
eap_psk_init(struct eap_sm * sm)33 static void * eap_psk_init(struct eap_sm *sm)
34 {
35 	struct eap_psk_data *data;
36 
37 	data = os_zalloc(sizeof(*data));
38 	if (data == NULL)
39 		return NULL;
40 	data->state = PSK_1;
41 
42 	return data;
43 }
44 
45 
eap_psk_reset(struct eap_sm * sm,void * priv)46 static void eap_psk_reset(struct eap_sm *sm, void *priv)
47 {
48 	struct eap_psk_data *data = priv;
49 	os_free(data->id_p);
50 	bin_clear_free(data, sizeof(*data));
51 }
52 
53 
eap_psk_build_1(struct eap_sm * sm,struct eap_psk_data * data,u8 id)54 static struct wpabuf * eap_psk_build_1(struct eap_sm *sm,
55 				       struct eap_psk_data *data, u8 id)
56 {
57 	struct wpabuf *req;
58 	struct eap_psk_hdr_1 *psk;
59 
60 	wpa_printf(MSG_DEBUG, "EAP-PSK: PSK-1 (sending)");
61 
62 	if (random_get_bytes(data->rand_s, EAP_PSK_RAND_LEN)) {
63 		wpa_printf(MSG_ERROR, "EAP-PSK: Failed to get random data");
64 		data->state = FAILURE;
65 		return NULL;
66 	}
67 	wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: RAND_S (server rand)",
68 		    data->rand_s, EAP_PSK_RAND_LEN);
69 
70 	req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK,
71 			    sizeof(*psk) + sm->server_id_len,
72 			    EAP_CODE_REQUEST, id);
73 	if (req == NULL) {
74 		wpa_printf(MSG_ERROR, "EAP-PSK: Failed to allocate memory "
75 			   "request");
76 		data->state = FAILURE;
77 		return NULL;
78 	}
79 
80 	psk = wpabuf_put(req, sizeof(*psk));
81 	psk->flags = EAP_PSK_FLAGS_SET_T(0); /* T=0 */
82 	os_memcpy(psk->rand_s, data->rand_s, EAP_PSK_RAND_LEN);
83 	wpabuf_put_data(req, sm->server_id, sm->server_id_len);
84 
85 	return req;
86 }
87 
88 
eap_psk_build_3(struct eap_sm * sm,struct eap_psk_data * data,u8 id)89 static struct wpabuf * eap_psk_build_3(struct eap_sm *sm,
90 				       struct eap_psk_data *data, u8 id)
91 {
92 	struct wpabuf *req;
93 	struct eap_psk_hdr_3 *psk;
94 	u8 *buf, *pchannel, nonce[16];
95 	size_t buflen;
96 
97 	wpa_printf(MSG_DEBUG, "EAP-PSK: PSK-3 (sending)");
98 
99 	req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK,
100 			    sizeof(*psk) + 4 + 16 + 1, EAP_CODE_REQUEST, id);
101 	if (req == NULL) {
102 		wpa_printf(MSG_ERROR, "EAP-PSK: Failed to allocate memory "
103 			   "request");
104 		data->state = FAILURE;
105 		return NULL;
106 	}
107 
108 	psk = wpabuf_put(req, sizeof(*psk));
109 	psk->flags = EAP_PSK_FLAGS_SET_T(2); /* T=2 */
110 	os_memcpy(psk->rand_s, data->rand_s, EAP_PSK_RAND_LEN);
111 
112 	/* MAC_S = OMAC1-AES-128(AK, ID_S||RAND_P) */
113 	buflen = sm->server_id_len + EAP_PSK_RAND_LEN;
114 	buf = os_malloc(buflen);
115 	if (buf == NULL)
116 		goto fail;
117 
118 	os_memcpy(buf, sm->server_id, sm->server_id_len);
119 	os_memcpy(buf + sm->server_id_len, data->rand_p, EAP_PSK_RAND_LEN);
120 	if (omac1_aes_128(data->ak, buf, buflen, psk->mac_s)) {
121 		os_free(buf);
122 		goto fail;
123 	}
124 	os_free(buf);
125 
126 	if (eap_psk_derive_keys(data->kdk, data->rand_p, data->tek, data->msk,
127 				data->emsk))
128 		goto fail;
129 	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: TEK", data->tek, EAP_PSK_TEK_LEN);
130 	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: MSK", data->msk, EAP_MSK_LEN);
131 	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: EMSK", data->emsk, EAP_EMSK_LEN);
132 
133 	os_memset(nonce, 0, sizeof(nonce));
134 	pchannel = wpabuf_put(req, 4 + 16 + 1);
135 	os_memcpy(pchannel, nonce + 12, 4);
136 	os_memset(pchannel + 4, 0, 16); /* Tag */
137 	pchannel[4 + 16] = EAP_PSK_R_FLAG_DONE_SUCCESS << 6;
138 	wpa_hexdump(MSG_DEBUG, "EAP-PSK: PCHANNEL (plaintext)",
139 		    pchannel, 4 + 16 + 1);
140 	if (aes_128_eax_encrypt(data->tek, nonce, sizeof(nonce),
141 				wpabuf_head(req), 22,
142 				pchannel + 4 + 16, 1, pchannel + 4))
143 		goto fail;
144 	wpa_hexdump(MSG_DEBUG, "EAP-PSK: PCHANNEL (encrypted)",
145 		    pchannel, 4 + 16 + 1);
146 
147 	return req;
148 
149 fail:
150 	wpabuf_free(req);
151 	data->state = FAILURE;
152 	return NULL;
153 }
154 
155 
eap_psk_buildReq(struct eap_sm * sm,void * priv,u8 id)156 static struct wpabuf * eap_psk_buildReq(struct eap_sm *sm, void *priv, u8 id)
157 {
158 	struct eap_psk_data *data = priv;
159 
160 	switch (data->state) {
161 	case PSK_1:
162 		return eap_psk_build_1(sm, data, id);
163 	case PSK_3:
164 		return eap_psk_build_3(sm, data, id);
165 	default:
166 		wpa_printf(MSG_DEBUG, "EAP-PSK: Unknown state %d in buildReq",
167 			   data->state);
168 		break;
169 	}
170 	return NULL;
171 }
172 
173 
eap_psk_check(struct eap_sm * sm,void * priv,struct wpabuf * respData)174 static Boolean eap_psk_check(struct eap_sm *sm, void *priv,
175 			     struct wpabuf *respData)
176 {
177 	struct eap_psk_data *data = priv;
178 	size_t len;
179 	u8 t;
180 	const u8 *pos;
181 
182 	pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData, &len);
183 	if (pos == NULL || len < 1) {
184 		wpa_printf(MSG_INFO, "EAP-PSK: Invalid frame");
185 		return TRUE;
186 	}
187 	t = EAP_PSK_FLAGS_GET_T(*pos);
188 
189 	wpa_printf(MSG_DEBUG, "EAP-PSK: received frame: T=%d", t);
190 
191 	if (data->state == PSK_1 && t != 1) {
192 		wpa_printf(MSG_DEBUG, "EAP-PSK: Expected PSK-2 - "
193 			   "ignore T=%d", t);
194 		return TRUE;
195 	}
196 
197 	if (data->state == PSK_3 && t != 3) {
198 		wpa_printf(MSG_DEBUG, "EAP-PSK: Expected PSK-4 - "
199 			   "ignore T=%d", t);
200 		return TRUE;
201 	}
202 
203 	if ((t == 1 && len < sizeof(struct eap_psk_hdr_2)) ||
204 	    (t == 3 && len < sizeof(struct eap_psk_hdr_4))) {
205 		wpa_printf(MSG_DEBUG, "EAP-PSK: Too short frame");
206 		return TRUE;
207 	}
208 
209 	return FALSE;
210 }
211 
212 
eap_psk_process_2(struct eap_sm * sm,struct eap_psk_data * data,struct wpabuf * respData)213 static void eap_psk_process_2(struct eap_sm *sm,
214 			      struct eap_psk_data *data,
215 			      struct wpabuf *respData)
216 {
217 	const struct eap_psk_hdr_2 *resp;
218 	u8 *pos, mac[EAP_PSK_MAC_LEN], *buf;
219 	size_t left, buflen;
220 	int i;
221 	const u8 *cpos;
222 
223 	if (data->state != PSK_1)
224 		return;
225 
226 	wpa_printf(MSG_DEBUG, "EAP-PSK: Received PSK-2");
227 
228 	cpos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData,
229 				&left);
230 	if (cpos == NULL || left < sizeof(*resp)) {
231 		wpa_printf(MSG_INFO, "EAP-PSK: Invalid frame");
232 		return;
233 	}
234 	resp = (const struct eap_psk_hdr_2 *) cpos;
235 	cpos = (const u8 *) (resp + 1);
236 	left -= sizeof(*resp);
237 
238 	os_free(data->id_p);
239 	data->id_p = os_malloc(left);
240 	if (data->id_p == NULL) {
241 		wpa_printf(MSG_INFO, "EAP-PSK: Failed to allocate memory for "
242 			   "ID_P");
243 		return;
244 	}
245 	os_memcpy(data->id_p, cpos, left);
246 	data->id_p_len = left;
247 	wpa_hexdump_ascii(MSG_MSGDUMP, "EAP-PSK: ID_P",
248 			  data->id_p, data->id_p_len);
249 
250 	if (eap_user_get(sm, data->id_p, data->id_p_len, 0) < 0) {
251 		wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: unknown ID_P",
252 				  data->id_p, data->id_p_len);
253 		data->state = FAILURE;
254 		return;
255 	}
256 
257 	for (i = 0;
258 	     i < EAP_MAX_METHODS &&
259 		     (sm->user->methods[i].vendor != EAP_VENDOR_IETF ||
260 		      sm->user->methods[i].method != EAP_TYPE_NONE);
261 	     i++) {
262 		if (sm->user->methods[i].vendor == EAP_VENDOR_IETF &&
263 		    sm->user->methods[i].method == EAP_TYPE_PSK)
264 			break;
265 	}
266 
267 	if (i >= EAP_MAX_METHODS ||
268 	    sm->user->methods[i].vendor != EAP_VENDOR_IETF ||
269 	    sm->user->methods[i].method != EAP_TYPE_PSK) {
270 		wpa_hexdump_ascii(MSG_DEBUG,
271 				  "EAP-PSK: EAP-PSK not enabled for ID_P",
272 				  data->id_p, data->id_p_len);
273 		data->state = FAILURE;
274 		return;
275 	}
276 
277 	if (sm->user->password == NULL ||
278 	    sm->user->password_len != EAP_PSK_PSK_LEN) {
279 		wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: invalid password in "
280 				  "user database for ID_P",
281 				  data->id_p, data->id_p_len);
282 		data->state = FAILURE;
283 		return;
284 	}
285 	if (eap_psk_key_setup(sm->user->password, data->ak, data->kdk)) {
286 		data->state = FAILURE;
287 		return;
288 	}
289 	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: AK", data->ak, EAP_PSK_AK_LEN);
290 	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: KDK", data->kdk, EAP_PSK_KDK_LEN);
291 
292 	wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: RAND_P (client rand)",
293 		    resp->rand_p, EAP_PSK_RAND_LEN);
294 	os_memcpy(data->rand_p, resp->rand_p, EAP_PSK_RAND_LEN);
295 
296 	/* MAC_P = OMAC1-AES-128(AK, ID_P||ID_S||RAND_S||RAND_P) */
297 	buflen = data->id_p_len + sm->server_id_len + 2 * EAP_PSK_RAND_LEN;
298 	buf = os_malloc(buflen);
299 	if (buf == NULL) {
300 		data->state = FAILURE;
301 		return;
302 	}
303 	os_memcpy(buf, data->id_p, data->id_p_len);
304 	pos = buf + data->id_p_len;
305 	os_memcpy(pos, sm->server_id, sm->server_id_len);
306 	pos += sm->server_id_len;
307 	os_memcpy(pos, data->rand_s, EAP_PSK_RAND_LEN);
308 	pos += EAP_PSK_RAND_LEN;
309 	os_memcpy(pos, data->rand_p, EAP_PSK_RAND_LEN);
310 	if (omac1_aes_128(data->ak, buf, buflen, mac)) {
311 		os_free(buf);
312 		data->state = FAILURE;
313 		return;
314 	}
315 	os_free(buf);
316 	wpa_hexdump(MSG_DEBUG, "EAP-PSK: MAC_P", resp->mac_p, EAP_PSK_MAC_LEN);
317 	if (os_memcmp_const(mac, resp->mac_p, EAP_PSK_MAC_LEN) != 0) {
318 		wpa_printf(MSG_INFO, "EAP-PSK: Invalid MAC_P");
319 		wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: Expected MAC_P",
320 			    mac, EAP_PSK_MAC_LEN);
321 		data->state = FAILURE;
322 		return;
323 	}
324 
325 	data->state = PSK_3;
326 }
327 
328 
eap_psk_process_4(struct eap_sm * sm,struct eap_psk_data * data,struct wpabuf * respData)329 static void eap_psk_process_4(struct eap_sm *sm,
330 			      struct eap_psk_data *data,
331 			      struct wpabuf *respData)
332 {
333 	const struct eap_psk_hdr_4 *resp;
334 	u8 *decrypted, nonce[16];
335 	size_t left;
336 	const u8 *pos, *tag;
337 
338 	if (data->state != PSK_3)
339 		return;
340 
341 	wpa_printf(MSG_DEBUG, "EAP-PSK: Received PSK-4");
342 
343 	pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData, &left);
344 	if (pos == NULL || left < sizeof(*resp)) {
345 		wpa_printf(MSG_INFO, "EAP-PSK: Invalid frame");
346 		return;
347 	}
348 	resp = (const struct eap_psk_hdr_4 *) pos;
349 	pos = (const u8 *) (resp + 1);
350 	left -= sizeof(*resp);
351 
352 	wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: Encrypted PCHANNEL", pos, left);
353 
354 	if (left < 4 + 16 + 1) {
355 		wpa_printf(MSG_INFO, "EAP-PSK: Too short PCHANNEL data in "
356 			   "PSK-4 (len=%lu, expected 21)",
357 			   (unsigned long) left);
358 		return;
359 	}
360 
361 	if (pos[0] == 0 && pos[1] == 0 && pos[2] == 0 && pos[3] == 0) {
362 		wpa_printf(MSG_DEBUG, "EAP-PSK: Nonce did not increase");
363 		return;
364 	}
365 
366 	os_memset(nonce, 0, 12);
367 	os_memcpy(nonce + 12, pos, 4);
368 	pos += 4;
369 	left -= 4;
370 	tag = pos;
371 	pos += 16;
372 	left -= 16;
373 
374 	decrypted = os_malloc(left);
375 	if (decrypted == NULL)
376 		return;
377 	os_memcpy(decrypted, pos, left);
378 
379 	if (aes_128_eax_decrypt(data->tek, nonce, sizeof(nonce),
380 				wpabuf_head(respData), 22, decrypted, left,
381 				tag)) {
382 		wpa_printf(MSG_WARNING, "EAP-PSK: PCHANNEL decryption failed");
383 		os_free(decrypted);
384 		data->state = FAILURE;
385 		return;
386 	}
387 	wpa_hexdump(MSG_DEBUG, "EAP-PSK: Decrypted PCHANNEL message",
388 		    decrypted, left);
389 
390 	/* Verify R flag */
391 	switch (decrypted[0] >> 6) {
392 	case EAP_PSK_R_FLAG_CONT:
393 		wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - CONT - unsupported");
394 		data->state = FAILURE;
395 		break;
396 	case EAP_PSK_R_FLAG_DONE_SUCCESS:
397 		wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_SUCCESS");
398 		data->state = SUCCESS;
399 		break;
400 	case EAP_PSK_R_FLAG_DONE_FAILURE:
401 		wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_FAILURE");
402 		data->state = FAILURE;
403 		break;
404 	}
405 	os_free(decrypted);
406 }
407 
408 
eap_psk_process(struct eap_sm * sm,void * priv,struct wpabuf * respData)409 static void eap_psk_process(struct eap_sm *sm, void *priv,
410 			    struct wpabuf *respData)
411 {
412 	struct eap_psk_data *data = priv;
413 	const u8 *pos;
414 	size_t len;
415 
416 	if (sm->user == NULL || sm->user->password == NULL) {
417 		wpa_printf(MSG_INFO, "EAP-PSK: Plaintext password not "
418 			   "configured");
419 		data->state = FAILURE;
420 		return;
421 	}
422 
423 	pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData, &len);
424 	if (pos == NULL || len < 1)
425 		return;
426 
427 	switch (EAP_PSK_FLAGS_GET_T(*pos)) {
428 	case 1:
429 		eap_psk_process_2(sm, data, respData);
430 		break;
431 	case 3:
432 		eap_psk_process_4(sm, data, respData);
433 		break;
434 	}
435 }
436 
437 
eap_psk_isDone(struct eap_sm * sm,void * priv)438 static Boolean eap_psk_isDone(struct eap_sm *sm, void *priv)
439 {
440 	struct eap_psk_data *data = priv;
441 	return data->state == SUCCESS || data->state == FAILURE;
442 }
443 
444 
eap_psk_getKey(struct eap_sm * sm,void * priv,size_t * len)445 static u8 * eap_psk_getKey(struct eap_sm *sm, void *priv, size_t *len)
446 {
447 	struct eap_psk_data *data = priv;
448 	u8 *key;
449 
450 	if (data->state != SUCCESS)
451 		return NULL;
452 
453 	key = os_malloc(EAP_MSK_LEN);
454 	if (key == NULL)
455 		return NULL;
456 	os_memcpy(key, data->msk, EAP_MSK_LEN);
457 	*len = EAP_MSK_LEN;
458 
459 	return key;
460 }
461 
462 
eap_psk_get_emsk(struct eap_sm * sm,void * priv,size_t * len)463 static u8 * eap_psk_get_emsk(struct eap_sm *sm, void *priv, size_t *len)
464 {
465 	struct eap_psk_data *data = priv;
466 	u8 *key;
467 
468 	if (data->state != SUCCESS)
469 		return NULL;
470 
471 	key = os_malloc(EAP_EMSK_LEN);
472 	if (key == NULL)
473 		return NULL;
474 	os_memcpy(key, data->emsk, EAP_EMSK_LEN);
475 	*len = EAP_EMSK_LEN;
476 
477 	return key;
478 }
479 
480 
eap_psk_isSuccess(struct eap_sm * sm,void * priv)481 static Boolean eap_psk_isSuccess(struct eap_sm *sm, void *priv)
482 {
483 	struct eap_psk_data *data = priv;
484 	return data->state == SUCCESS;
485 }
486 
487 
eap_psk_get_session_id(struct eap_sm * sm,void * priv,size_t * len)488 static u8 * eap_psk_get_session_id(struct eap_sm *sm, void *priv, size_t *len)
489 {
490 	struct eap_psk_data *data = priv;
491 	u8 *id;
492 
493 	if (data->state != SUCCESS)
494 		return NULL;
495 
496 	*len = 1 + 2 * EAP_PSK_RAND_LEN;
497 	id = os_malloc(*len);
498 	if (id == NULL)
499 		return NULL;
500 
501 	id[0] = EAP_TYPE_PSK;
502 	os_memcpy(id + 1, data->rand_p, EAP_PSK_RAND_LEN);
503 	os_memcpy(id + 1 + EAP_PSK_RAND_LEN, data->rand_s, EAP_PSK_RAND_LEN);
504 	wpa_hexdump(MSG_DEBUG, "EAP-PSK: Derived Session-Id", id, *len);
505 
506 	return id;
507 }
508 
509 
eap_server_psk_register(void)510 int eap_server_psk_register(void)
511 {
512 	struct eap_method *eap;
513 	int ret;
514 
515 	eap = eap_server_method_alloc(EAP_SERVER_METHOD_INTERFACE_VERSION,
516 				      EAP_VENDOR_IETF, EAP_TYPE_PSK, "PSK");
517 	if (eap == NULL)
518 		return -1;
519 
520 	eap->init = eap_psk_init;
521 	eap->reset = eap_psk_reset;
522 	eap->buildReq = eap_psk_buildReq;
523 	eap->check = eap_psk_check;
524 	eap->process = eap_psk_process;
525 	eap->isDone = eap_psk_isDone;
526 	eap->getKey = eap_psk_getKey;
527 	eap->isSuccess = eap_psk_isSuccess;
528 	eap->get_emsk = eap_psk_get_emsk;
529 	eap->getSessionId = eap_psk_get_session_id;
530 
531 	ret = eap_server_method_register(eap);
532 	if (ret)
533 		eap_server_method_free(eap);
534 	return ret;
535 }
536