eap_psk.c revision 189251 
1/*
2 * EAP peer method: EAP-PSK (RFC 4764)
3 * Copyright (c) 2004-2008, Jouni Malinen <j@w1.fi>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 *
9 * Alternatively, this software may be distributed under the terms of BSD
10 * license.
11 *
12 * See README and COPYING for more details.
13 *
14 * Note: EAP-PSK is an EAP authentication method and as such, completely
15 * different from WPA-PSK. This file is not needed for WPA-PSK functionality.
16 */
17
18#include "includes.h"
19
20#include "common.h"
21#include "eap_peer/eap_i.h"
22#include "aes_wrap.h"
23#include "eap_common/eap_psk_common.h"
24
25
26struct eap_psk_data {
27	enum { PSK_INIT, PSK_MAC_SENT, PSK_DONE } state;
28	u8 rand_p[EAP_PSK_RAND_LEN];
29	u8 ak[EAP_PSK_AK_LEN], kdk[EAP_PSK_KDK_LEN], tek[EAP_PSK_TEK_LEN];
30	u8 *id_s, *id_p;
31	size_t id_s_len, id_p_len;
32	u8 msk[EAP_MSK_LEN];
33	u8 emsk[EAP_EMSK_LEN];
34};
35
36
37static void * eap_psk_init(struct eap_sm *sm)
38{
39	struct eap_psk_data *data;
40	const u8 *identity, *password;
41	size_t identity_len, password_len;
42
43	password = eap_get_config_password(sm, &password_len);
44	if (!password || password_len != 16) {
45		wpa_printf(MSG_INFO, "EAP-PSK: 16-octet pre-shared key not "
46			   "configured");
47		return NULL;
48	}
49
50	data = os_zalloc(sizeof(*data));
51	if (data == NULL)
52		return NULL;
53	if (eap_psk_key_setup(password, data->ak, data->kdk)) {
54		os_free(data);
55		return NULL;
56	}
57	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: AK", data->ak, EAP_PSK_AK_LEN);
58	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: KDK", data->kdk, EAP_PSK_KDK_LEN);
59	data->state = PSK_INIT;
60
61	identity = eap_get_config_identity(sm, &identity_len);
62	if (identity) {
63		data->id_p = os_malloc(identity_len);
64		if (data->id_p)
65			os_memcpy(data->id_p, identity, identity_len);
66		data->id_p_len = identity_len;
67	}
68	if (data->id_p == NULL) {
69		wpa_printf(MSG_INFO, "EAP-PSK: could not get own identity");
70		os_free(data);
71		return NULL;
72	}
73
74	return data;
75}
76
77
78static void eap_psk_deinit(struct eap_sm *sm, void *priv)
79{
80	struct eap_psk_data *data = priv;
81	os_free(data->id_s);
82	os_free(data->id_p);
83	os_free(data);
84}
85
86
87static struct wpabuf * eap_psk_process_1(struct eap_psk_data *data,
88					 struct eap_method_ret *ret,
89					 const struct wpabuf *reqData)
90{
91	const struct eap_psk_hdr_1 *hdr1;
92	struct eap_psk_hdr_2 *hdr2;
93	struct wpabuf *resp;
94	u8 *buf, *pos;
95	size_t buflen, len;
96	const u8 *cpos;
97
98	wpa_printf(MSG_DEBUG, "EAP-PSK: in INIT state");
99
100	cpos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, reqData, &len);
101	hdr1 = (const struct eap_psk_hdr_1 *) cpos;
102	if (cpos == NULL || len < sizeof(*hdr1)) {
103		wpa_printf(MSG_INFO, "EAP-PSK: Invalid first message "
104			   "length (%lu; expected %lu or more)",
105			   (unsigned long) len,
106			   (unsigned long) sizeof(*hdr1));
107		ret->ignore = TRUE;
108		return NULL;
109	}
110	wpa_printf(MSG_DEBUG, "EAP-PSK: Flags=0x%x", hdr1->flags);
111	if (EAP_PSK_FLAGS_GET_T(hdr1->flags) != 0) {
112		wpa_printf(MSG_INFO, "EAP-PSK: Unexpected T=%d (expected 0)",
113			   EAP_PSK_FLAGS_GET_T(hdr1->flags));
114		ret->methodState = METHOD_DONE;
115		ret->decision = DECISION_FAIL;
116		return NULL;
117	}
118	wpa_hexdump(MSG_DEBUG, "EAP-PSK: RAND_S", hdr1->rand_s,
119		    EAP_PSK_RAND_LEN);
120	os_free(data->id_s);
121	data->id_s_len = len - sizeof(*hdr1);
122	data->id_s = os_malloc(data->id_s_len);
123	if (data->id_s == NULL) {
124		wpa_printf(MSG_ERROR, "EAP-PSK: Failed to allocate memory for "
125			   "ID_S (len=%lu)", (unsigned long) data->id_s_len);
126		ret->ignore = TRUE;
127		return NULL;
128	}
129	os_memcpy(data->id_s, (u8 *) (hdr1 + 1), data->id_s_len);
130	wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: ID_S",
131			  data->id_s, data->id_s_len);
132
133	if (os_get_random(data->rand_p, EAP_PSK_RAND_LEN)) {
134		wpa_printf(MSG_ERROR, "EAP-PSK: Failed to get random data");
135		ret->ignore = TRUE;
136		return NULL;
137	}
138
139	resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK,
140			     sizeof(*hdr2) + data->id_p_len, EAP_CODE_RESPONSE,
141			     eap_get_id(reqData));
142	if (resp == NULL)
143		return NULL;
144	hdr2 = wpabuf_put(resp, sizeof(*hdr2));
145	hdr2->flags = EAP_PSK_FLAGS_SET_T(1); /* T=1 */
146	os_memcpy(hdr2->rand_s, hdr1->rand_s, EAP_PSK_RAND_LEN);
147	os_memcpy(hdr2->rand_p, data->rand_p, EAP_PSK_RAND_LEN);
148	wpabuf_put_data(resp, data->id_p, data->id_p_len);
149	/* MAC_P = OMAC1-AES-128(AK, ID_P||ID_S||RAND_S||RAND_P) */
150	buflen = data->id_p_len + data->id_s_len + 2 * EAP_PSK_RAND_LEN;
151	buf = os_malloc(buflen);
152	if (buf == NULL) {
153		wpabuf_free(resp);
154		return NULL;
155	}
156	os_memcpy(buf, data->id_p, data->id_p_len);
157	pos = buf + data->id_p_len;
158	os_memcpy(pos, data->id_s, data->id_s_len);
159	pos += data->id_s_len;
160	os_memcpy(pos, hdr1->rand_s, EAP_PSK_RAND_LEN);
161	pos += EAP_PSK_RAND_LEN;
162	os_memcpy(pos, data->rand_p, EAP_PSK_RAND_LEN);
163	if (omac1_aes_128(data->ak, buf, buflen, hdr2->mac_p)) {
164		os_free(buf);
165		wpabuf_free(resp);
166		return NULL;
167	}
168	os_free(buf);
169	wpa_hexdump(MSG_DEBUG, "EAP-PSK: RAND_P", hdr2->rand_p,
170		    EAP_PSK_RAND_LEN);
171	wpa_hexdump(MSG_DEBUG, "EAP-PSK: MAC_P", hdr2->mac_p, EAP_PSK_MAC_LEN);
172	wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: ID_P",
173			  data->id_p, data->id_p_len);
174
175	data->state = PSK_MAC_SENT;
176
177	return resp;
178}
179
180
181static struct wpabuf * eap_psk_process_3(struct eap_psk_data *data,
182					 struct eap_method_ret *ret,
183					 const struct wpabuf *reqData)
184{
185	const struct eap_psk_hdr_3 *hdr3;
186	struct eap_psk_hdr_4 *hdr4;
187	struct wpabuf *resp;
188	u8 *buf, *rpchannel, nonce[16], *decrypted;
189	const u8 *pchannel, *tag, *msg;
190	u8 mac[EAP_PSK_MAC_LEN];
191	size_t buflen, left, data_len, len, plen;
192	int failed = 0;
193	const u8 *pos;
194
195	wpa_printf(MSG_DEBUG, "EAP-PSK: in MAC_SENT state");
196
197	pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK,
198			       reqData, &len);
199	hdr3 = (const struct eap_psk_hdr_3 *) pos;
200	if (pos == NULL || len < sizeof(*hdr3)) {
201		wpa_printf(MSG_INFO, "EAP-PSK: Invalid third message "
202			   "length (%lu; expected %lu or more)",
203			   (unsigned long) len,
204			   (unsigned long) sizeof(*hdr3));
205		ret->ignore = TRUE;
206		return NULL;
207	}
208	left = len - sizeof(*hdr3);
209	pchannel = (const u8 *) (hdr3 + 1);
210	wpa_printf(MSG_DEBUG, "EAP-PSK: Flags=0x%x", hdr3->flags);
211	if (EAP_PSK_FLAGS_GET_T(hdr3->flags) != 2) {
212		wpa_printf(MSG_INFO, "EAP-PSK: Unexpected T=%d (expected 2)",
213			   EAP_PSK_FLAGS_GET_T(hdr3->flags));
214		ret->methodState = METHOD_DONE;
215		ret->decision = DECISION_FAIL;
216		return NULL;
217	}
218	wpa_hexdump(MSG_DEBUG, "EAP-PSK: RAND_S", hdr3->rand_s,
219		    EAP_PSK_RAND_LEN);
220	wpa_hexdump(MSG_DEBUG, "EAP-PSK: MAC_S", hdr3->mac_s, EAP_PSK_MAC_LEN);
221	wpa_hexdump(MSG_DEBUG, "EAP-PSK: PCHANNEL", pchannel, left);
222
223	if (left < 4 + 16 + 1) {
224		wpa_printf(MSG_INFO, "EAP-PSK: Too short PCHANNEL data in "
225			   "third message (len=%lu, expected 21)",
226			   (unsigned long) left);
227		ret->ignore = TRUE;
228		return NULL;
229	}
230
231	/* MAC_S = OMAC1-AES-128(AK, ID_S||RAND_P) */
232	buflen = data->id_s_len + EAP_PSK_RAND_LEN;
233	buf = os_malloc(buflen);
234	if (buf == NULL)
235		return NULL;
236	os_memcpy(buf, data->id_s, data->id_s_len);
237	os_memcpy(buf + data->id_s_len, data->rand_p, EAP_PSK_RAND_LEN);
238	if (omac1_aes_128(data->ak, buf, buflen, mac)) {
239		os_free(buf);
240		return NULL;
241	}
242	os_free(buf);
243	if (os_memcmp(mac, hdr3->mac_s, EAP_PSK_MAC_LEN) != 0) {
244		wpa_printf(MSG_WARNING, "EAP-PSK: Invalid MAC_S in third "
245			   "message");
246		ret->methodState = METHOD_DONE;
247		ret->decision = DECISION_FAIL;
248		return NULL;
249	}
250	wpa_printf(MSG_DEBUG, "EAP-PSK: MAC_S verified successfully");
251
252	if (eap_psk_derive_keys(data->kdk, data->rand_p, data->tek,
253				data->msk, data->emsk)) {
254		ret->methodState = METHOD_DONE;
255		ret->decision = DECISION_FAIL;
256		return NULL;
257	}
258	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: TEK", data->tek, EAP_PSK_TEK_LEN);
259	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: MSK", data->msk, EAP_MSK_LEN);
260	wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: EMSK", data->emsk, EAP_EMSK_LEN);
261
262	os_memset(nonce, 0, 12);
263	os_memcpy(nonce + 12, pchannel, 4);
264	pchannel += 4;
265	left -= 4;
266
267	tag = pchannel;
268	pchannel += 16;
269	left -= 16;
270
271	msg = pchannel;
272
273	wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: PCHANNEL - nonce",
274		    nonce, sizeof(nonce));
275	wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: PCHANNEL - hdr",
276		    wpabuf_head(reqData), 5);
277	wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: PCHANNEL - cipher msg", msg, left);
278
279	decrypted = os_malloc(left);
280	if (decrypted == NULL) {
281		ret->methodState = METHOD_DONE;
282		ret->decision = DECISION_FAIL;
283		return NULL;
284	}
285	os_memcpy(decrypted, msg, left);
286
287	if (aes_128_eax_decrypt(data->tek, nonce, sizeof(nonce),
288				wpabuf_head(reqData),
289				sizeof(struct eap_hdr) + 1 +
290				sizeof(*hdr3) - EAP_PSK_MAC_LEN, decrypted,
291				left, tag)) {
292		wpa_printf(MSG_WARNING, "EAP-PSK: PCHANNEL decryption failed");
293		os_free(decrypted);
294		return NULL;
295	}
296	wpa_hexdump(MSG_DEBUG, "EAP-PSK: Decrypted PCHANNEL message",
297		    decrypted, left);
298
299	/* Verify R flag */
300	switch (decrypted[0] >> 6) {
301	case EAP_PSK_R_FLAG_CONT:
302		wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - CONT - unsupported");
303		failed = 1;
304		break;
305	case EAP_PSK_R_FLAG_DONE_SUCCESS:
306		wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_SUCCESS");
307		break;
308	case EAP_PSK_R_FLAG_DONE_FAILURE:
309		wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_FAILURE");
310		wpa_printf(MSG_INFO, "EAP-PSK: Authentication server rejected "
311			   "authentication");
312		failed = 1;
313		break;
314	}
315
316	data_len = 1;
317	if ((decrypted[0] & EAP_PSK_E_FLAG) && left > 1)
318		data_len++;
319	plen = sizeof(*hdr4) + 4 + 16 + data_len;
320	resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK, plen,
321			     EAP_CODE_RESPONSE, eap_get_id(reqData));
322	if (resp == NULL) {
323		os_free(decrypted);
324		return NULL;
325	}
326	hdr4 = wpabuf_put(resp, sizeof(*hdr4));
327	hdr4->flags = EAP_PSK_FLAGS_SET_T(3); /* T=3 */
328	os_memcpy(hdr4->rand_s, hdr3->rand_s, EAP_PSK_RAND_LEN);
329	rpchannel = wpabuf_put(resp, 4 + 16 + data_len);
330
331	/* nonce++ */
332	inc_byte_array(nonce, sizeof(nonce));
333	os_memcpy(rpchannel, nonce + 12, 4);
334
335	if (decrypted[0] & EAP_PSK_E_FLAG) {
336		wpa_printf(MSG_DEBUG, "EAP-PSK: Unsupported E (Ext) flag");
337		failed = 1;
338		rpchannel[4 + 16] = (EAP_PSK_R_FLAG_DONE_FAILURE << 6) |
339			EAP_PSK_E_FLAG;
340		if (left > 1) {
341			/* Add empty EXT_Payload with same EXT_Type */
342			rpchannel[4 + 16 + 1] = decrypted[1];
343		}
344	} else if (failed)
345		rpchannel[4 + 16] = EAP_PSK_R_FLAG_DONE_FAILURE << 6;
346	else
347		rpchannel[4 + 16] = EAP_PSK_R_FLAG_DONE_SUCCESS << 6;
348
349	wpa_hexdump(MSG_DEBUG, "EAP-PSK: reply message (plaintext)",
350		    rpchannel + 4 + 16, data_len);
351	if (aes_128_eax_encrypt(data->tek, nonce, sizeof(nonce),
352				wpabuf_head(resp),
353				sizeof(struct eap_hdr) + 1 + sizeof(*hdr4),
354				rpchannel + 4 + 16, data_len, rpchannel + 4)) {
355		os_free(decrypted);
356		wpabuf_free(resp);
357		return NULL;
358	}
359	wpa_hexdump(MSG_DEBUG, "EAP-PSK: reply message (PCHANNEL)",
360		    rpchannel, 4 + 16 + data_len);
361
362	wpa_printf(MSG_DEBUG, "EAP-PSK: Completed %ssuccessfully",
363		   failed ? "un" : "");
364	data->state = PSK_DONE;
365	ret->methodState = METHOD_DONE;
366	ret->decision = failed ? DECISION_FAIL : DECISION_UNCOND_SUCC;
367
368	os_free(decrypted);
369
370	return resp;
371}
372
373
374static struct wpabuf * eap_psk_process(struct eap_sm *sm, void *priv,
375				       struct eap_method_ret *ret,
376				       const struct wpabuf *reqData)
377{
378	struct eap_psk_data *data = priv;
379	const u8 *pos;
380	struct wpabuf *resp = NULL;
381	size_t len;
382
383	pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, reqData, &len);
384	if (pos == NULL) {
385		ret->ignore = TRUE;
386		return NULL;
387	}
388
389	ret->ignore = FALSE;
390	ret->methodState = METHOD_MAY_CONT;
391	ret->decision = DECISION_FAIL;
392	ret->allowNotifications = TRUE;
393
394	switch (data->state) {
395	case PSK_INIT:
396		resp = eap_psk_process_1(data, ret, reqData);
397		break;
398	case PSK_MAC_SENT:
399		resp = eap_psk_process_3(data, ret, reqData);
400		break;
401	case PSK_DONE:
402		wpa_printf(MSG_DEBUG, "EAP-PSK: in DONE state - ignore "
403			   "unexpected message");
404		ret->ignore = TRUE;
405		return NULL;
406	}
407
408	if (ret->methodState == METHOD_DONE) {
409		ret->allowNotifications = FALSE;
410	}
411
412	return resp;
413}
414
415
416static Boolean eap_psk_isKeyAvailable(struct eap_sm *sm, void *priv)
417{
418	struct eap_psk_data *data = priv;
419	return data->state == PSK_DONE;
420}
421
422
423static u8 * eap_psk_getKey(struct eap_sm *sm, void *priv, size_t *len)
424{
425	struct eap_psk_data *data = priv;
426	u8 *key;
427
428	if (data->state != PSK_DONE)
429		return NULL;
430
431	key = os_malloc(EAP_MSK_LEN);
432	if (key == NULL)
433		return NULL;
434
435	*len = EAP_MSK_LEN;
436	os_memcpy(key, data->msk, EAP_MSK_LEN);
437
438	return key;
439}
440
441
442static u8 * eap_psk_get_emsk(struct eap_sm *sm, void *priv, size_t *len)
443{
444	struct eap_psk_data *data = priv;
445	u8 *key;
446
447	if (data->state != PSK_DONE)
448		return NULL;
449
450	key = os_malloc(EAP_EMSK_LEN);
451	if (key == NULL)
452		return NULL;
453
454	*len = EAP_EMSK_LEN;
455	os_memcpy(key, data->emsk, EAP_EMSK_LEN);
456
457	return key;
458}
459
460
461int eap_peer_psk_register(void)
462{
463	struct eap_method *eap;
464	int ret;
465
466	eap = eap_peer_method_alloc(EAP_PEER_METHOD_INTERFACE_VERSION,
467				    EAP_VENDOR_IETF, EAP_TYPE_PSK, "PSK");
468	if (eap == NULL)
469		return -1;
470
471	eap->init = eap_psk_init;
472	eap->deinit = eap_psk_deinit;
473	eap->process = eap_psk_process;
474	eap->isKeyAvailable = eap_psk_isKeyAvailable;
475	eap->getKey = eap_psk_getKey;
476	eap->get_emsk = eap_psk_get_emsk;
477
478	ret = eap_peer_method_register(eap);
479	if (ret)
480		eap_peer_method_free(eap);
481	return ret;
482}
483