1/*
2 * EAP peer method: EAP-PSK (RFC 4764)
3 * Copyright (c) 2004-2008, 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_i.h"
19
20
21struct eap_psk_data {
22	enum { PSK_INIT, PSK_MAC_SENT, PSK_DONE } state;
23	u8 rand_p[EAP_PSK_RAND_LEN];
24	u8 rand_s[EAP_PSK_RAND_LEN];
25	u8 ak[EAP_PSK_AK_LEN], kdk[EAP_PSK_KDK_LEN], tek[EAP_PSK_TEK_LEN];
26	u8 *id_s, *id_p;
27	size_t id_s_len, id_p_len;
28	u8 msk[EAP_MSK_LEN];
29	u8 emsk[EAP_EMSK_LEN];
30};
31
32
33static void * eap_psk_init(struct eap_sm *sm)
34{
35	struct eap_psk_data *data;
36	const u8 *identity, *password;
37	size_t identity_len, password_len;
38
39	password = eap_get_config_password(sm, &password_len);
40	if (!password || password_len != 16) {
41		wpa_printf(MSG_INFO, "EAP-PSK: 16-octet pre-shared key not "
42			   "configured");
43		return NULL;
44	}
45
46	data = os_zalloc(sizeof(*data));
47	if (data == NULL)
48		return NULL;
49	if (eap_psk_key_setup(password, data->ak, data->kdk)) {
50		os_free(data);
51		return NULL;
52	}
53	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: AK", data->ak, EAP_PSK_AK_LEN);
54	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: KDK", data->kdk, EAP_PSK_KDK_LEN);
55	data->state = PSK_INIT;
56
57	identity = eap_get_config_identity(sm, &identity_len);
58	if (identity) {
59		data->id_p = os_malloc(identity_len);
60		if (data->id_p)
61			os_memcpy(data->id_p, identity, identity_len);
62		data->id_p_len = identity_len;
63	}
64	if (data->id_p == NULL) {
65		wpa_printf(MSG_INFO, "EAP-PSK: could not get own identity");
66		os_free(data);
67		return NULL;
68	}
69
70	return data;
71}
72
73
74static void eap_psk_deinit(struct eap_sm *sm, void *priv)
75{
76	struct eap_psk_data *data = priv;
77	os_free(data->id_s);
78	os_free(data->id_p);
79	bin_clear_free(data, sizeof(*data));
80}
81
82
83static struct wpabuf * eap_psk_process_1(struct eap_psk_data *data,
84					 struct eap_method_ret *ret,
85					 const struct wpabuf *reqData)
86{
87	const struct eap_psk_hdr_1 *hdr1;
88	struct eap_psk_hdr_2 *hdr2;
89	struct wpabuf *resp;
90	u8 *buf, *pos;
91	size_t buflen, len;
92	const u8 *cpos;
93
94	wpa_printf(MSG_DEBUG, "EAP-PSK: in INIT state");
95
96	cpos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, reqData, &len);
97	hdr1 = (const struct eap_psk_hdr_1 *) cpos;
98	if (cpos == NULL || len < sizeof(*hdr1)) {
99		wpa_printf(MSG_INFO, "EAP-PSK: Invalid first message "
100			   "length (%lu; expected %lu or more)",
101			   (unsigned long) len,
102			   (unsigned long) sizeof(*hdr1));
103		ret->ignore = TRUE;
104		return NULL;
105	}
106	wpa_printf(MSG_DEBUG, "EAP-PSK: Flags=0x%x", hdr1->flags);
107	if (EAP_PSK_FLAGS_GET_T(hdr1->flags) != 0) {
108		wpa_printf(MSG_INFO, "EAP-PSK: Unexpected T=%d (expected 0)",
109			   EAP_PSK_FLAGS_GET_T(hdr1->flags));
110		ret->methodState = METHOD_DONE;
111		ret->decision = DECISION_FAIL;
112		return NULL;
113	}
114	wpa_hexdump(MSG_DEBUG, "EAP-PSK: RAND_S", hdr1->rand_s,
115		    EAP_PSK_RAND_LEN);
116	os_memcpy(data->rand_s, hdr1->rand_s, EAP_PSK_RAND_LEN);
117	os_free(data->id_s);
118	data->id_s_len = len - sizeof(*hdr1);
119	data->id_s = os_malloc(data->id_s_len);
120	if (data->id_s == NULL) {
121		wpa_printf(MSG_ERROR, "EAP-PSK: Failed to allocate memory for "
122			   "ID_S (len=%lu)", (unsigned long) data->id_s_len);
123		ret->ignore = TRUE;
124		return NULL;
125	}
126	os_memcpy(data->id_s, (u8 *) (hdr1 + 1), data->id_s_len);
127	wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: ID_S",
128			  data->id_s, data->id_s_len);
129
130	if (random_get_bytes(data->rand_p, EAP_PSK_RAND_LEN)) {
131		wpa_printf(MSG_ERROR, "EAP-PSK: Failed to get random data");
132		ret->ignore = TRUE;
133		return NULL;
134	}
135
136	resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK,
137			     sizeof(*hdr2) + data->id_p_len, EAP_CODE_RESPONSE,
138			     eap_get_id(reqData));
139	if (resp == NULL)
140		return NULL;
141	hdr2 = wpabuf_put(resp, sizeof(*hdr2));
142	hdr2->flags = EAP_PSK_FLAGS_SET_T(1); /* T=1 */
143	os_memcpy(hdr2->rand_s, hdr1->rand_s, EAP_PSK_RAND_LEN);
144	os_memcpy(hdr2->rand_p, data->rand_p, EAP_PSK_RAND_LEN);
145	wpabuf_put_data(resp, data->id_p, data->id_p_len);
146	/* MAC_P = OMAC1-AES-128(AK, ID_P||ID_S||RAND_S||RAND_P) */
147	buflen = data->id_p_len + data->id_s_len + 2 * EAP_PSK_RAND_LEN;
148	buf = os_malloc(buflen);
149	if (buf == NULL) {
150		wpabuf_free(resp);
151		return NULL;
152	}
153	os_memcpy(buf, data->id_p, data->id_p_len);
154	pos = buf + data->id_p_len;
155	os_memcpy(pos, data->id_s, data->id_s_len);
156	pos += data->id_s_len;
157	os_memcpy(pos, hdr1->rand_s, EAP_PSK_RAND_LEN);
158	pos += EAP_PSK_RAND_LEN;
159	os_memcpy(pos, data->rand_p, EAP_PSK_RAND_LEN);
160	if (omac1_aes_128(data->ak, buf, buflen, hdr2->mac_p)) {
161		os_free(buf);
162		wpabuf_free(resp);
163		return NULL;
164	}
165	os_free(buf);
166	wpa_hexdump(MSG_DEBUG, "EAP-PSK: RAND_P", hdr2->rand_p,
167		    EAP_PSK_RAND_LEN);
168	wpa_hexdump(MSG_DEBUG, "EAP-PSK: MAC_P", hdr2->mac_p, EAP_PSK_MAC_LEN);
169	wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: ID_P",
170			  data->id_p, data->id_p_len);
171
172	data->state = PSK_MAC_SENT;
173
174	return resp;
175}
176
177
178static struct wpabuf * eap_psk_process_3(struct eap_psk_data *data,
179					 struct eap_method_ret *ret,
180					 const struct wpabuf *reqData)
181{
182	const struct eap_psk_hdr_3 *hdr3;
183	struct eap_psk_hdr_4 *hdr4;
184	struct wpabuf *resp;
185	u8 *buf, *rpchannel, nonce[16], *decrypted;
186	const u8 *pchannel, *tag, *msg;
187	u8 mac[EAP_PSK_MAC_LEN];
188	size_t buflen, left, data_len, len, plen;
189	int failed = 0;
190	const u8 *pos;
191
192	wpa_printf(MSG_DEBUG, "EAP-PSK: in MAC_SENT state");
193
194	pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK,
195			       reqData, &len);
196	hdr3 = (const struct eap_psk_hdr_3 *) pos;
197	if (pos == NULL || len < sizeof(*hdr3)) {
198		wpa_printf(MSG_INFO, "EAP-PSK: Invalid third message "
199			   "length (%lu; expected %lu or more)",
200			   (unsigned long) len,
201			   (unsigned long) sizeof(*hdr3));
202		ret->ignore = TRUE;
203		return NULL;
204	}
205	left = len - sizeof(*hdr3);
206	pchannel = (const u8 *) (hdr3 + 1);
207	wpa_printf(MSG_DEBUG, "EAP-PSK: Flags=0x%x", hdr3->flags);
208	if (EAP_PSK_FLAGS_GET_T(hdr3->flags) != 2) {
209		wpa_printf(MSG_INFO, "EAP-PSK: Unexpected T=%d (expected 2)",
210			   EAP_PSK_FLAGS_GET_T(hdr3->flags));
211		ret->methodState = METHOD_DONE;
212		ret->decision = DECISION_FAIL;
213		return NULL;
214	}
215	wpa_hexdump(MSG_DEBUG, "EAP-PSK: RAND_S", hdr3->rand_s,
216		    EAP_PSK_RAND_LEN);
217	wpa_hexdump(MSG_DEBUG, "EAP-PSK: MAC_S", hdr3->mac_s, EAP_PSK_MAC_LEN);
218	wpa_hexdump(MSG_DEBUG, "EAP-PSK: PCHANNEL", pchannel, left);
219
220	if (left < 4 + 16 + 1) {
221		wpa_printf(MSG_INFO, "EAP-PSK: Too short PCHANNEL data in "
222			   "third message (len=%lu, expected 21)",
223			   (unsigned long) left);
224		ret->ignore = TRUE;
225		return NULL;
226	}
227
228	/* MAC_S = OMAC1-AES-128(AK, ID_S||RAND_P) */
229	buflen = data->id_s_len + EAP_PSK_RAND_LEN;
230	buf = os_malloc(buflen);
231	if (buf == NULL)
232		return NULL;
233	os_memcpy(buf, data->id_s, data->id_s_len);
234	os_memcpy(buf + data->id_s_len, data->rand_p, EAP_PSK_RAND_LEN);
235	if (omac1_aes_128(data->ak, buf, buflen, mac)) {
236		os_free(buf);
237		return NULL;
238	}
239	os_free(buf);
240	if (os_memcmp_const(mac, hdr3->mac_s, EAP_PSK_MAC_LEN) != 0) {
241		wpa_printf(MSG_WARNING, "EAP-PSK: Invalid MAC_S in third "
242			   "message");
243		ret->methodState = METHOD_DONE;
244		ret->decision = DECISION_FAIL;
245		return NULL;
246	}
247	wpa_printf(MSG_DEBUG, "EAP-PSK: MAC_S verified successfully");
248
249	if (eap_psk_derive_keys(data->kdk, data->rand_p, data->tek,
250				data->msk, data->emsk)) {
251		ret->methodState = METHOD_DONE;
252		ret->decision = DECISION_FAIL;
253		return NULL;
254	}
255	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: TEK", data->tek, EAP_PSK_TEK_LEN);
256	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: MSK", data->msk, EAP_MSK_LEN);
257	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: EMSK", data->emsk, EAP_EMSK_LEN);
258
259	os_memset(nonce, 0, 12);
260	os_memcpy(nonce + 12, pchannel, 4);
261	pchannel += 4;
262	left -= 4;
263
264	tag = pchannel;
265	pchannel += 16;
266	left -= 16;
267
268	msg = pchannel;
269
270	wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: PCHANNEL - nonce",
271		    nonce, sizeof(nonce));
272	wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: PCHANNEL - hdr",
273		    wpabuf_head(reqData), 5);
274	wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: PCHANNEL - cipher msg", msg, left);
275
276	decrypted = os_malloc(left);
277	if (decrypted == NULL) {
278		ret->methodState = METHOD_DONE;
279		ret->decision = DECISION_FAIL;
280		return NULL;
281	}
282	os_memcpy(decrypted, msg, left);
283
284	if (aes_128_eax_decrypt(data->tek, nonce, sizeof(nonce),
285				wpabuf_head(reqData),
286				sizeof(struct eap_hdr) + 1 +
287				sizeof(*hdr3) - EAP_PSK_MAC_LEN, decrypted,
288				left, tag)) {
289		wpa_printf(MSG_WARNING, "EAP-PSK: PCHANNEL decryption failed");
290		os_free(decrypted);
291		return NULL;
292	}
293	wpa_hexdump(MSG_DEBUG, "EAP-PSK: Decrypted PCHANNEL message",
294		    decrypted, left);
295
296	/* Verify R flag */
297	switch (decrypted[0] >> 6) {
298	case EAP_PSK_R_FLAG_CONT:
299		wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - CONT - unsupported");
300		failed = 1;
301		break;
302	case EAP_PSK_R_FLAG_DONE_SUCCESS:
303		wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_SUCCESS");
304		break;
305	case EAP_PSK_R_FLAG_DONE_FAILURE:
306		wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_FAILURE");
307		wpa_printf(MSG_INFO, "EAP-PSK: Authentication server rejected "
308			   "authentication");
309		failed = 1;
310		break;
311	}
312
313	data_len = 1;
314	if ((decrypted[0] & EAP_PSK_E_FLAG) && left > 1)
315		data_len++;
316	plen = sizeof(*hdr4) + 4 + 16 + data_len;
317	resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK, plen,
318			     EAP_CODE_RESPONSE, eap_get_id(reqData));
319	if (resp == NULL) {
320		os_free(decrypted);
321		return NULL;
322	}
323	hdr4 = wpabuf_put(resp, sizeof(*hdr4));
324	hdr4->flags = EAP_PSK_FLAGS_SET_T(3); /* T=3 */
325	os_memcpy(hdr4->rand_s, hdr3->rand_s, EAP_PSK_RAND_LEN);
326	rpchannel = wpabuf_put(resp, 4 + 16 + data_len);
327
328	/* nonce++ */
329	inc_byte_array(nonce, sizeof(nonce));
330	os_memcpy(rpchannel, nonce + 12, 4);
331
332	if (decrypted[0] & EAP_PSK_E_FLAG) {
333		wpa_printf(MSG_DEBUG, "EAP-PSK: Unsupported E (Ext) flag");
334		failed = 1;
335		rpchannel[4 + 16] = (EAP_PSK_R_FLAG_DONE_FAILURE << 6) |
336			EAP_PSK_E_FLAG;
337		if (left > 1) {
338			/* Add empty EXT_Payload with same EXT_Type */
339			rpchannel[4 + 16 + 1] = decrypted[1];
340		}
341	} else if (failed)
342		rpchannel[4 + 16] = EAP_PSK_R_FLAG_DONE_FAILURE << 6;
343	else
344		rpchannel[4 + 16] = EAP_PSK_R_FLAG_DONE_SUCCESS << 6;
345
346	wpa_hexdump(MSG_DEBUG, "EAP-PSK: reply message (plaintext)",
347		    rpchannel + 4 + 16, data_len);
348	if (aes_128_eax_encrypt(data->tek, nonce, sizeof(nonce),
349				wpabuf_head(resp),
350				sizeof(struct eap_hdr) + 1 + sizeof(*hdr4),
351				rpchannel + 4 + 16, data_len, rpchannel + 4)) {
352		os_free(decrypted);
353		wpabuf_free(resp);
354		return NULL;
355	}
356	wpa_hexdump(MSG_DEBUG, "EAP-PSK: reply message (PCHANNEL)",
357		    rpchannel, 4 + 16 + data_len);
358
359	wpa_printf(MSG_DEBUG, "EAP-PSK: Completed %ssuccessfully",
360		   failed ? "un" : "");
361	data->state = PSK_DONE;
362	ret->methodState = METHOD_DONE;
363	ret->decision = failed ? DECISION_FAIL : DECISION_UNCOND_SUCC;
364
365	os_free(decrypted);
366
367	return resp;
368}
369
370
371static struct wpabuf * eap_psk_process(struct eap_sm *sm, void *priv,
372				       struct eap_method_ret *ret,
373				       const struct wpabuf *reqData)
374{
375	struct eap_psk_data *data = priv;
376	const u8 *pos;
377	struct wpabuf *resp = NULL;
378	size_t len;
379
380	pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, reqData, &len);
381	if (pos == NULL) {
382		ret->ignore = TRUE;
383		return NULL;
384	}
385
386	ret->ignore = FALSE;
387	ret->methodState = METHOD_MAY_CONT;
388	ret->decision = DECISION_FAIL;
389	ret->allowNotifications = TRUE;
390
391	switch (data->state) {
392	case PSK_INIT:
393		resp = eap_psk_process_1(data, ret, reqData);
394		break;
395	case PSK_MAC_SENT:
396		resp = eap_psk_process_3(data, ret, reqData);
397		break;
398	case PSK_DONE:
399		wpa_printf(MSG_DEBUG, "EAP-PSK: in DONE state - ignore "
400			   "unexpected message");
401		ret->ignore = TRUE;
402		return NULL;
403	}
404
405	if (ret->methodState == METHOD_DONE) {
406		ret->allowNotifications = FALSE;
407	}
408
409	return resp;
410}
411
412
413static Boolean eap_psk_isKeyAvailable(struct eap_sm *sm, void *priv)
414{
415	struct eap_psk_data *data = priv;
416	return data->state == PSK_DONE;
417}
418
419
420static u8 * eap_psk_getKey(struct eap_sm *sm, void *priv, size_t *len)
421{
422	struct eap_psk_data *data = priv;
423	u8 *key;
424
425	if (data->state != PSK_DONE)
426		return NULL;
427
428	key = os_malloc(EAP_MSK_LEN);
429	if (key == NULL)
430		return NULL;
431
432	*len = EAP_MSK_LEN;
433	os_memcpy(key, data->msk, EAP_MSK_LEN);
434
435	return key;
436}
437
438
439static u8 * eap_psk_get_session_id(struct eap_sm *sm, void *priv, size_t *len)
440{
441	struct eap_psk_data *data = priv;
442	u8 *id;
443
444	if (data->state != PSK_DONE)
445		return NULL;
446
447	*len = 1 + 2 * EAP_PSK_RAND_LEN;
448	id = os_malloc(*len);
449	if (id == NULL)
450		return NULL;
451
452	id[0] = EAP_TYPE_PSK;
453	os_memcpy(id + 1, data->rand_p, EAP_PSK_RAND_LEN);
454	os_memcpy(id + 1 + EAP_PSK_RAND_LEN, data->rand_s, EAP_PSK_RAND_LEN);
455	wpa_hexdump(MSG_DEBUG, "EAP-PSK: Derived Session-Id", id, *len);
456
457	return id;
458}
459
460
461static u8 * eap_psk_get_emsk(struct eap_sm *sm, void *priv, size_t *len)
462{
463	struct eap_psk_data *data = priv;
464	u8 *key;
465
466	if (data->state != PSK_DONE)
467		return NULL;
468
469	key = os_malloc(EAP_EMSK_LEN);
470	if (key == NULL)
471		return NULL;
472
473	*len = EAP_EMSK_LEN;
474	os_memcpy(key, data->emsk, EAP_EMSK_LEN);
475
476	return key;
477}
478
479
480int eap_peer_psk_register(void)
481{
482	struct eap_method *eap;
483	int ret;
484
485	eap = eap_peer_method_alloc(EAP_PEER_METHOD_INTERFACE_VERSION,
486				    EAP_VENDOR_IETF, EAP_TYPE_PSK, "PSK");
487	if (eap == NULL)
488		return -1;
489
490	eap->init = eap_psk_init;
491	eap->deinit = eap_psk_deinit;
492	eap->process = eap_psk_process;
493	eap->isKeyAvailable = eap_psk_isKeyAvailable;
494	eap->getKey = eap_psk_getKey;
495	eap->getSessionId = eap_psk_get_session_id;
496	eap->get_emsk = eap_psk_get_emsk;
497
498	ret = eap_peer_method_register(eap);
499	if (ret)
500		eap_peer_method_free(eap);
501	return ret;
502}
503