1 /*
2 * hostapd / EAP-pwd (RFC 5931) server
3 * Copyright (c) 2010, Dan Harkins <dharkins@lounge.org>
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9 #include "includes.h"
10
11 #include "common.h"
12 #include "crypto/sha256.h"
13 #include "eap_server/eap_i.h"
14 #include "eap_common/eap_pwd_common.h"
15
16
17 struct eap_pwd_data {
18 enum {
19 PWD_ID_Req, PWD_Commit_Req, PWD_Confirm_Req, SUCCESS, FAILURE
20 } state;
21 u8 *id_peer;
22 size_t id_peer_len;
23 u8 *id_server;
24 size_t id_server_len;
25 u8 *password;
26 size_t password_len;
27 u32 token;
28 u16 group_num;
29 EAP_PWD_group *grp;
30
31 struct wpabuf *inbuf;
32 size_t in_frag_pos;
33 struct wpabuf *outbuf;
34 size_t out_frag_pos;
35 size_t mtu;
36
37 BIGNUM *k;
38 BIGNUM *private_value;
39 BIGNUM *peer_scalar;
40 BIGNUM *my_scalar;
41 EC_POINT *my_element;
42 EC_POINT *peer_element;
43
44 u8 my_confirm[SHA256_MAC_LEN];
45
46 u8 msk[EAP_MSK_LEN];
47 u8 emsk[EAP_EMSK_LEN];
48 u8 session_id[1 + SHA256_MAC_LEN];
49
50 BN_CTX *bnctx;
51 };
52
53
eap_pwd_state_txt(int state)54 static const char * eap_pwd_state_txt(int state)
55 {
56 switch (state) {
57 case PWD_ID_Req:
58 return "PWD-ID-Req";
59 case PWD_Commit_Req:
60 return "PWD-Commit-Req";
61 case PWD_Confirm_Req:
62 return "PWD-Confirm-Req";
63 case SUCCESS:
64 return "SUCCESS";
65 case FAILURE:
66 return "FAILURE";
67 default:
68 return "PWD-Unk";
69 }
70 }
71
72
eap_pwd_state(struct eap_pwd_data * data,int state)73 static void eap_pwd_state(struct eap_pwd_data *data, int state)
74 {
75 wpa_printf(MSG_DEBUG, "EAP-pwd: %s -> %s",
76 eap_pwd_state_txt(data->state), eap_pwd_state_txt(state));
77 data->state = state;
78 }
79
80
eap_pwd_init(struct eap_sm * sm)81 static void * eap_pwd_init(struct eap_sm *sm)
82 {
83 struct eap_pwd_data *data;
84
85 if (sm->user == NULL || sm->user->password == NULL ||
86 sm->user->password_len == 0) {
87 wpa_printf(MSG_INFO, "EAP-PWD (server): Password is not "
88 "configured");
89 return NULL;
90 }
91
92 data = os_zalloc(sizeof(*data));
93 if (data == NULL)
94 return NULL;
95
96 data->group_num = sm->pwd_group;
97 wpa_printf(MSG_DEBUG, "EAP-pwd: Selected group number %d",
98 data->group_num);
99 data->state = PWD_ID_Req;
100
101 data->id_server = (u8 *) os_strdup("server");
102 if (data->id_server)
103 data->id_server_len = os_strlen((char *) data->id_server);
104
105 data->password = os_malloc(sm->user->password_len);
106 if (data->password == NULL) {
107 wpa_printf(MSG_INFO, "EAP-PWD: Memory allocation password "
108 "fail");
109 bin_clear_free(data->id_server, data->id_server_len);
110 os_free(data);
111 return NULL;
112 }
113 data->password_len = sm->user->password_len;
114 os_memcpy(data->password, sm->user->password, data->password_len);
115
116 data->bnctx = BN_CTX_new();
117 if (data->bnctx == NULL) {
118 wpa_printf(MSG_INFO, "EAP-PWD: bn context allocation fail");
119 bin_clear_free(data->password, data->password_len);
120 bin_clear_free(data->id_server, data->id_server_len);
121 os_free(data);
122 return NULL;
123 }
124
125 data->in_frag_pos = data->out_frag_pos = 0;
126 data->inbuf = data->outbuf = NULL;
127 /* use default MTU from RFC 5931 if not configured otherwise */
128 data->mtu = sm->fragment_size > 0 ? sm->fragment_size : 1020;
129
130 return data;
131 }
132
133
eap_pwd_reset(struct eap_sm * sm,void * priv)134 static void eap_pwd_reset(struct eap_sm *sm, void *priv)
135 {
136 struct eap_pwd_data *data = priv;
137
138 BN_clear_free(data->private_value);
139 BN_clear_free(data->peer_scalar);
140 BN_clear_free(data->my_scalar);
141 BN_clear_free(data->k);
142 BN_CTX_free(data->bnctx);
143 EC_POINT_clear_free(data->my_element);
144 EC_POINT_clear_free(data->peer_element);
145 bin_clear_free(data->id_peer, data->id_peer_len);
146 bin_clear_free(data->id_server, data->id_server_len);
147 bin_clear_free(data->password, data->password_len);
148 if (data->grp) {
149 EC_GROUP_free(data->grp->group);
150 EC_POINT_clear_free(data->grp->pwe);
151 BN_clear_free(data->grp->order);
152 BN_clear_free(data->grp->prime);
153 os_free(data->grp);
154 }
155 wpabuf_free(data->inbuf);
156 wpabuf_free(data->outbuf);
157 bin_clear_free(data, sizeof(*data));
158 }
159
160
eap_pwd_build_id_req(struct eap_sm * sm,struct eap_pwd_data * data,u8 id)161 static void eap_pwd_build_id_req(struct eap_sm *sm, struct eap_pwd_data *data,
162 u8 id)
163 {
164 wpa_printf(MSG_DEBUG, "EAP-pwd: ID/Request");
165 /*
166 * if we're fragmenting then we already have an id request, just return
167 */
168 if (data->out_frag_pos)
169 return;
170
171 data->outbuf = wpabuf_alloc(sizeof(struct eap_pwd_id) +
172 data->id_server_len);
173 if (data->outbuf == NULL) {
174 eap_pwd_state(data, FAILURE);
175 return;
176 }
177
178 /* an lfsr is good enough to generate unpredictable tokens */
179 data->token = os_random();
180 wpabuf_put_be16(data->outbuf, data->group_num);
181 wpabuf_put_u8(data->outbuf, EAP_PWD_DEFAULT_RAND_FUNC);
182 wpabuf_put_u8(data->outbuf, EAP_PWD_DEFAULT_PRF);
183 wpabuf_put_data(data->outbuf, &data->token, sizeof(data->token));
184 wpabuf_put_u8(data->outbuf, EAP_PWD_PREP_NONE);
185 wpabuf_put_data(data->outbuf, data->id_server, data->id_server_len);
186 }
187
188
eap_pwd_build_commit_req(struct eap_sm * sm,struct eap_pwd_data * data,u8 id)189 static void eap_pwd_build_commit_req(struct eap_sm *sm,
190 struct eap_pwd_data *data, u8 id)
191 {
192 BIGNUM *mask = NULL, *x = NULL, *y = NULL;
193 u8 *scalar = NULL, *element = NULL;
194 u16 offset;
195
196 wpa_printf(MSG_DEBUG, "EAP-pwd: Commit/Request");
197 /*
198 * if we're fragmenting then we already have an commit request, just
199 * return
200 */
201 if (data->out_frag_pos)
202 return;
203
204 if (((data->private_value = BN_new()) == NULL) ||
205 ((data->my_element = EC_POINT_new(data->grp->group)) == NULL) ||
206 ((data->my_scalar = BN_new()) == NULL) ||
207 ((mask = BN_new()) == NULL)) {
208 wpa_printf(MSG_INFO, "EAP-PWD (server): scalar allocation "
209 "fail");
210 goto fin;
211 }
212
213 if (BN_rand_range(data->private_value, data->grp->order) != 1 ||
214 BN_rand_range(mask, data->grp->order) != 1 ||
215 BN_add(data->my_scalar, data->private_value, mask) != 1 ||
216 BN_mod(data->my_scalar, data->my_scalar, data->grp->order,
217 data->bnctx) != 1) {
218 wpa_printf(MSG_INFO,
219 "EAP-pwd (server): unable to get randomness");
220 goto fin;
221 }
222
223 if (!EC_POINT_mul(data->grp->group, data->my_element, NULL,
224 data->grp->pwe, mask, data->bnctx)) {
225 wpa_printf(MSG_INFO, "EAP-PWD (server): element allocation "
226 "fail");
227 eap_pwd_state(data, FAILURE);
228 goto fin;
229 }
230
231 if (!EC_POINT_invert(data->grp->group, data->my_element, data->bnctx))
232 {
233 wpa_printf(MSG_INFO, "EAP-PWD (server): element inversion "
234 "fail");
235 goto fin;
236 }
237 BN_clear_free(mask);
238
239 if (((x = BN_new()) == NULL) ||
240 ((y = BN_new()) == NULL)) {
241 wpa_printf(MSG_INFO, "EAP-PWD (server): point allocation "
242 "fail");
243 goto fin;
244 }
245 if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
246 data->my_element, x, y,
247 data->bnctx)) {
248 wpa_printf(MSG_INFO, "EAP-PWD (server): point assignment "
249 "fail");
250 goto fin;
251 }
252
253 if (((scalar = os_malloc(BN_num_bytes(data->grp->order))) == NULL) ||
254 ((element = os_malloc(BN_num_bytes(data->grp->prime) * 2)) ==
255 NULL)) {
256 wpa_printf(MSG_INFO, "EAP-PWD (server): data allocation fail");
257 goto fin;
258 }
259
260 /*
261 * bignums occupy as little memory as possible so one that is
262 * sufficiently smaller than the prime or order might need pre-pending
263 * with zeros.
264 */
265 os_memset(scalar, 0, BN_num_bytes(data->grp->order));
266 os_memset(element, 0, BN_num_bytes(data->grp->prime) * 2);
267 offset = BN_num_bytes(data->grp->order) -
268 BN_num_bytes(data->my_scalar);
269 BN_bn2bin(data->my_scalar, scalar + offset);
270
271 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(x);
272 BN_bn2bin(x, element + offset);
273 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(y);
274 BN_bn2bin(y, element + BN_num_bytes(data->grp->prime) + offset);
275
276 data->outbuf = wpabuf_alloc(2 * BN_num_bytes(data->grp->prime) +
277 BN_num_bytes(data->grp->order));
278 if (data->outbuf == NULL)
279 goto fin;
280
281 /* We send the element as (x,y) followed by the scalar */
282 wpabuf_put_data(data->outbuf, element,
283 2 * BN_num_bytes(data->grp->prime));
284 wpabuf_put_data(data->outbuf, scalar, BN_num_bytes(data->grp->order));
285
286 fin:
287 os_free(scalar);
288 os_free(element);
289 BN_clear_free(x);
290 BN_clear_free(y);
291 if (data->outbuf == NULL)
292 eap_pwd_state(data, FAILURE);
293 }
294
295
eap_pwd_build_confirm_req(struct eap_sm * sm,struct eap_pwd_data * data,u8 id)296 static void eap_pwd_build_confirm_req(struct eap_sm *sm,
297 struct eap_pwd_data *data, u8 id)
298 {
299 BIGNUM *x = NULL, *y = NULL;
300 struct crypto_hash *hash;
301 u8 conf[SHA256_MAC_LEN], *cruft = NULL, *ptr;
302 u16 grp;
303 int offset;
304
305 wpa_printf(MSG_DEBUG, "EAP-pwd: Confirm/Request");
306 /*
307 * if we're fragmenting then we already have an confirm request, just
308 * return
309 */
310 if (data->out_frag_pos)
311 return;
312
313 /* Each component of the cruft will be at most as big as the prime */
314 if (((cruft = os_malloc(BN_num_bytes(data->grp->prime))) == NULL) ||
315 ((x = BN_new()) == NULL) || ((y = BN_new()) == NULL)) {
316 wpa_printf(MSG_INFO, "EAP-PWD (server): debug allocation "
317 "fail");
318 goto fin;
319 }
320
321 /*
322 * commit is H(k | server_element | server_scalar | peer_element |
323 * peer_scalar | ciphersuite)
324 */
325 hash = eap_pwd_h_init();
326 if (hash == NULL)
327 goto fin;
328
329 /*
330 * Zero the memory each time because this is mod prime math and some
331 * value may start with a few zeros and the previous one did not.
332 *
333 * First is k
334 */
335 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
336 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(data->k);
337 BN_bn2bin(data->k, cruft + offset);
338 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->prime));
339
340 /* server element: x, y */
341 if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
342 data->my_element, x, y,
343 data->bnctx)) {
344 wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
345 "assignment fail");
346 goto fin;
347 }
348
349 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
350 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(x);
351 BN_bn2bin(x, cruft + offset);
352 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->prime));
353 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
354 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(y);
355 BN_bn2bin(y, cruft + offset);
356 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->prime));
357
358 /* server scalar */
359 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
360 offset = BN_num_bytes(data->grp->order) -
361 BN_num_bytes(data->my_scalar);
362 BN_bn2bin(data->my_scalar, cruft + offset);
363 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->order));
364
365 /* peer element: x, y */
366 if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
367 data->peer_element, x, y,
368 data->bnctx)) {
369 wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
370 "assignment fail");
371 goto fin;
372 }
373
374 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
375 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(x);
376 BN_bn2bin(x, cruft + offset);
377 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->prime));
378 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
379 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(y);
380 BN_bn2bin(y, cruft + offset);
381 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->prime));
382
383 /* peer scalar */
384 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
385 offset = BN_num_bytes(data->grp->order) -
386 BN_num_bytes(data->peer_scalar);
387 BN_bn2bin(data->peer_scalar, cruft + offset);
388 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->order));
389
390 /* ciphersuite */
391 grp = htons(data->group_num);
392 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
393 ptr = cruft;
394 os_memcpy(ptr, &grp, sizeof(u16));
395 ptr += sizeof(u16);
396 *ptr = EAP_PWD_DEFAULT_RAND_FUNC;
397 ptr += sizeof(u8);
398 *ptr = EAP_PWD_DEFAULT_PRF;
399 ptr += sizeof(u8);
400 eap_pwd_h_update(hash, cruft, ptr - cruft);
401
402 /* all done with the random function */
403 eap_pwd_h_final(hash, conf);
404 os_memcpy(data->my_confirm, conf, SHA256_MAC_LEN);
405
406 data->outbuf = wpabuf_alloc(SHA256_MAC_LEN);
407 if (data->outbuf == NULL)
408 goto fin;
409
410 wpabuf_put_data(data->outbuf, conf, SHA256_MAC_LEN);
411
412 fin:
413 bin_clear_free(cruft, BN_num_bytes(data->grp->prime));
414 BN_clear_free(x);
415 BN_clear_free(y);
416 if (data->outbuf == NULL)
417 eap_pwd_state(data, FAILURE);
418 }
419
420
421 static struct wpabuf *
eap_pwd_build_req(struct eap_sm * sm,void * priv,u8 id)422 eap_pwd_build_req(struct eap_sm *sm, void *priv, u8 id)
423 {
424 struct eap_pwd_data *data = priv;
425 struct wpabuf *req;
426 u8 lm_exch;
427 const u8 *buf;
428 u16 totlen = 0;
429 size_t len;
430
431 /*
432 * if we're buffering response fragments then just ACK
433 */
434 if (data->in_frag_pos) {
435 wpa_printf(MSG_DEBUG, "EAP-pwd: ACKing a fragment!!");
436 req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PWD,
437 EAP_PWD_HDR_SIZE, EAP_CODE_REQUEST, id);
438 if (req == NULL) {
439 eap_pwd_state(data, FAILURE);
440 return NULL;
441 }
442 switch (data->state) {
443 case PWD_ID_Req:
444 wpabuf_put_u8(req, EAP_PWD_OPCODE_ID_EXCH);
445 break;
446 case PWD_Commit_Req:
447 wpabuf_put_u8(req, EAP_PWD_OPCODE_COMMIT_EXCH);
448 break;
449 case PWD_Confirm_Req:
450 wpabuf_put_u8(req, EAP_PWD_OPCODE_CONFIRM_EXCH);
451 break;
452 default:
453 eap_pwd_state(data, FAILURE); /* just to be sure */
454 wpabuf_free(req);
455 return NULL;
456 }
457 return req;
458 }
459
460 /*
461 * build the data portion of a request
462 */
463 switch (data->state) {
464 case PWD_ID_Req:
465 eap_pwd_build_id_req(sm, data, id);
466 lm_exch = EAP_PWD_OPCODE_ID_EXCH;
467 break;
468 case PWD_Commit_Req:
469 eap_pwd_build_commit_req(sm, data, id);
470 lm_exch = EAP_PWD_OPCODE_COMMIT_EXCH;
471 break;
472 case PWD_Confirm_Req:
473 eap_pwd_build_confirm_req(sm, data, id);
474 lm_exch = EAP_PWD_OPCODE_CONFIRM_EXCH;
475 break;
476 default:
477 wpa_printf(MSG_INFO, "EAP-pwd: Unknown state %d in build_req",
478 data->state);
479 eap_pwd_state(data, FAILURE);
480 lm_exch = 0; /* hush now, sweet compiler */
481 break;
482 }
483
484 if (data->state == FAILURE)
485 return NULL;
486
487 /*
488 * determine whether that data needs to be fragmented
489 */
490 len = wpabuf_len(data->outbuf) - data->out_frag_pos;
491 if ((len + EAP_PWD_HDR_SIZE) > data->mtu) {
492 len = data->mtu - EAP_PWD_HDR_SIZE;
493 EAP_PWD_SET_MORE_BIT(lm_exch);
494 /*
495 * if this is the first fragment, need to set the M bit
496 * and add the total length to the eap_pwd_hdr
497 */
498 if (data->out_frag_pos == 0) {
499 EAP_PWD_SET_LENGTH_BIT(lm_exch);
500 totlen = wpabuf_len(data->outbuf) +
501 EAP_PWD_HDR_SIZE + sizeof(u16);
502 len -= sizeof(u16);
503 wpa_printf(MSG_DEBUG, "EAP-pwd: Fragmenting output, "
504 "total length = %d", totlen);
505 }
506 wpa_printf(MSG_DEBUG, "EAP-pwd: Send a %d byte fragment",
507 (int) len);
508 }
509
510 /*
511 * alloc an eap request and populate it with the data
512 */
513 req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PWD,
514 EAP_PWD_HDR_SIZE + len +
515 (totlen ? sizeof(u16) : 0),
516 EAP_CODE_REQUEST, id);
517 if (req == NULL) {
518 eap_pwd_state(data, FAILURE);
519 return NULL;
520 }
521
522 wpabuf_put_u8(req, lm_exch);
523 if (EAP_PWD_GET_LENGTH_BIT(lm_exch))
524 wpabuf_put_be16(req, totlen);
525
526 buf = wpabuf_head_u8(data->outbuf);
527 wpabuf_put_data(req, buf + data->out_frag_pos, len);
528 data->out_frag_pos += len;
529 /*
530 * either not fragged or last fragment, either way free up the data
531 */
532 if (data->out_frag_pos >= wpabuf_len(data->outbuf)) {
533 wpabuf_free(data->outbuf);
534 data->outbuf = NULL;
535 data->out_frag_pos = 0;
536 }
537
538 return req;
539 }
540
541
eap_pwd_check(struct eap_sm * sm,void * priv,struct wpabuf * respData)542 static Boolean eap_pwd_check(struct eap_sm *sm, void *priv,
543 struct wpabuf *respData)
544 {
545 struct eap_pwd_data *data = priv;
546 const u8 *pos;
547 size_t len;
548
549 pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PWD, respData, &len);
550 if (pos == NULL || len < 1) {
551 wpa_printf(MSG_INFO, "EAP-pwd: Invalid frame");
552 return TRUE;
553 }
554
555 wpa_printf(MSG_DEBUG, "EAP-pwd: Received frame: exch = %d, len = %d",
556 EAP_PWD_GET_EXCHANGE(*pos), (int) len);
557
558 if (data->state == PWD_ID_Req &&
559 ((EAP_PWD_GET_EXCHANGE(*pos)) == EAP_PWD_OPCODE_ID_EXCH))
560 return FALSE;
561
562 if (data->state == PWD_Commit_Req &&
563 ((EAP_PWD_GET_EXCHANGE(*pos)) == EAP_PWD_OPCODE_COMMIT_EXCH))
564 return FALSE;
565
566 if (data->state == PWD_Confirm_Req &&
567 ((EAP_PWD_GET_EXCHANGE(*pos)) == EAP_PWD_OPCODE_CONFIRM_EXCH))
568 return FALSE;
569
570 wpa_printf(MSG_INFO, "EAP-pwd: Unexpected opcode=%d in state=%d",
571 *pos, data->state);
572
573 return TRUE;
574 }
575
576
eap_pwd_process_id_resp(struct eap_sm * sm,struct eap_pwd_data * data,const u8 * payload,size_t payload_len)577 static void eap_pwd_process_id_resp(struct eap_sm *sm,
578 struct eap_pwd_data *data,
579 const u8 *payload, size_t payload_len)
580 {
581 struct eap_pwd_id *id;
582
583 if (payload_len < sizeof(struct eap_pwd_id)) {
584 wpa_printf(MSG_INFO, "EAP-pwd: Invalid ID response");
585 return;
586 }
587
588 id = (struct eap_pwd_id *) payload;
589 if ((data->group_num != be_to_host16(id->group_num)) ||
590 (id->random_function != EAP_PWD_DEFAULT_RAND_FUNC) ||
591 (os_memcmp(id->token, (u8 *)&data->token, sizeof(data->token))) ||
592 (id->prf != EAP_PWD_DEFAULT_PRF)) {
593 wpa_printf(MSG_INFO, "EAP-pwd: peer changed parameters");
594 eap_pwd_state(data, FAILURE);
595 return;
596 }
597 data->id_peer = os_malloc(payload_len - sizeof(struct eap_pwd_id));
598 if (data->id_peer == NULL) {
599 wpa_printf(MSG_INFO, "EAP-PWD: memory allocation id fail");
600 return;
601 }
602 data->id_peer_len = payload_len - sizeof(struct eap_pwd_id);
603 os_memcpy(data->id_peer, id->identity, data->id_peer_len);
604 wpa_hexdump_ascii(MSG_DEBUG, "EAP-PWD (server): peer sent id of",
605 data->id_peer, data->id_peer_len);
606
607 data->grp = os_zalloc(sizeof(EAP_PWD_group));
608 if (data->grp == NULL) {
609 wpa_printf(MSG_INFO, "EAP-PWD: failed to allocate memory for "
610 "group");
611 return;
612 }
613 if (compute_password_element(data->grp, data->group_num,
614 data->password, data->password_len,
615 data->id_server, data->id_server_len,
616 data->id_peer, data->id_peer_len,
617 (u8 *) &data->token)) {
618 wpa_printf(MSG_INFO, "EAP-PWD (server): unable to compute "
619 "PWE");
620 return;
621 }
622 wpa_printf(MSG_DEBUG, "EAP-PWD (server): computed %d bit PWE...",
623 BN_num_bits(data->grp->prime));
624
625 eap_pwd_state(data, PWD_Commit_Req);
626 }
627
628
629 static void
eap_pwd_process_commit_resp(struct eap_sm * sm,struct eap_pwd_data * data,const u8 * payload,size_t payload_len)630 eap_pwd_process_commit_resp(struct eap_sm *sm, struct eap_pwd_data *data,
631 const u8 *payload, size_t payload_len)
632 {
633 u8 *ptr;
634 BIGNUM *x = NULL, *y = NULL, *cofactor = NULL;
635 EC_POINT *K = NULL, *point = NULL;
636 int res = 0;
637
638 wpa_printf(MSG_DEBUG, "EAP-pwd: Received commit response");
639
640 if (((data->peer_scalar = BN_new()) == NULL) ||
641 ((data->k = BN_new()) == NULL) ||
642 ((cofactor = BN_new()) == NULL) ||
643 ((x = BN_new()) == NULL) ||
644 ((y = BN_new()) == NULL) ||
645 ((point = EC_POINT_new(data->grp->group)) == NULL) ||
646 ((K = EC_POINT_new(data->grp->group)) == NULL) ||
647 ((data->peer_element = EC_POINT_new(data->grp->group)) == NULL)) {
648 wpa_printf(MSG_INFO, "EAP-PWD (server): peer data allocation "
649 "fail");
650 goto fin;
651 }
652
653 if (!EC_GROUP_get_cofactor(data->grp->group, cofactor, NULL)) {
654 wpa_printf(MSG_INFO, "EAP-PWD (server): unable to get "
655 "cofactor for curve");
656 goto fin;
657 }
658
659 /* element, x then y, followed by scalar */
660 ptr = (u8 *) payload;
661 BN_bin2bn(ptr, BN_num_bytes(data->grp->prime), x);
662 ptr += BN_num_bytes(data->grp->prime);
663 BN_bin2bn(ptr, BN_num_bytes(data->grp->prime), y);
664 ptr += BN_num_bytes(data->grp->prime);
665 BN_bin2bn(ptr, BN_num_bytes(data->grp->order), data->peer_scalar);
666 if (!EC_POINT_set_affine_coordinates_GFp(data->grp->group,
667 data->peer_element, x, y,
668 data->bnctx)) {
669 wpa_printf(MSG_INFO, "EAP-PWD (server): setting peer element "
670 "fail");
671 goto fin;
672 }
673
674 /* check to ensure peer's element is not in a small sub-group */
675 if (BN_cmp(cofactor, BN_value_one())) {
676 if (!EC_POINT_mul(data->grp->group, point, NULL,
677 data->peer_element, cofactor, NULL)) {
678 wpa_printf(MSG_INFO, "EAP-PWD (server): cannot "
679 "multiply peer element by order");
680 goto fin;
681 }
682 if (EC_POINT_is_at_infinity(data->grp->group, point)) {
683 wpa_printf(MSG_INFO, "EAP-PWD (server): peer element "
684 "is at infinity!\n");
685 goto fin;
686 }
687 }
688
689 /* compute the shared key, k */
690 if ((!EC_POINT_mul(data->grp->group, K, NULL, data->grp->pwe,
691 data->peer_scalar, data->bnctx)) ||
692 (!EC_POINT_add(data->grp->group, K, K, data->peer_element,
693 data->bnctx)) ||
694 (!EC_POINT_mul(data->grp->group, K, NULL, K, data->private_value,
695 data->bnctx))) {
696 wpa_printf(MSG_INFO, "EAP-PWD (server): computing shared key "
697 "fail");
698 goto fin;
699 }
700
701 /* ensure that the shared key isn't in a small sub-group */
702 if (BN_cmp(cofactor, BN_value_one())) {
703 if (!EC_POINT_mul(data->grp->group, K, NULL, K, cofactor,
704 NULL)) {
705 wpa_printf(MSG_INFO, "EAP-PWD (server): cannot "
706 "multiply shared key point by order!\n");
707 goto fin;
708 }
709 }
710
711 /*
712 * This check is strictly speaking just for the case above where
713 * co-factor > 1 but it was suggested that even though this is probably
714 * never going to happen it is a simple and safe check "just to be
715 * sure" so let's be safe.
716 */
717 if (EC_POINT_is_at_infinity(data->grp->group, K)) {
718 wpa_printf(MSG_INFO, "EAP-PWD (server): shared key point is "
719 "at infinity");
720 goto fin;
721 }
722 if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group, K, data->k,
723 NULL, data->bnctx)) {
724 wpa_printf(MSG_INFO, "EAP-PWD (server): unable to extract "
725 "shared secret from secret point");
726 goto fin;
727 }
728 res = 1;
729
730 fin:
731 EC_POINT_clear_free(K);
732 EC_POINT_clear_free(point);
733 BN_clear_free(cofactor);
734 BN_clear_free(x);
735 BN_clear_free(y);
736
737 if (res)
738 eap_pwd_state(data, PWD_Confirm_Req);
739 else
740 eap_pwd_state(data, FAILURE);
741 }
742
743
744 static void
eap_pwd_process_confirm_resp(struct eap_sm * sm,struct eap_pwd_data * data,const u8 * payload,size_t payload_len)745 eap_pwd_process_confirm_resp(struct eap_sm *sm, struct eap_pwd_data *data,
746 const u8 *payload, size_t payload_len)
747 {
748 BIGNUM *x = NULL, *y = NULL;
749 struct crypto_hash *hash;
750 u32 cs;
751 u16 grp;
752 u8 conf[SHA256_MAC_LEN], *cruft = NULL, *ptr;
753 int offset;
754
755 /* build up the ciphersuite: group | random_function | prf */
756 grp = htons(data->group_num);
757 ptr = (u8 *) &cs;
758 os_memcpy(ptr, &grp, sizeof(u16));
759 ptr += sizeof(u16);
760 *ptr = EAP_PWD_DEFAULT_RAND_FUNC;
761 ptr += sizeof(u8);
762 *ptr = EAP_PWD_DEFAULT_PRF;
763
764 /* each component of the cruft will be at most as big as the prime */
765 if (((cruft = os_malloc(BN_num_bytes(data->grp->prime))) == NULL) ||
766 ((x = BN_new()) == NULL) || ((y = BN_new()) == NULL)) {
767 wpa_printf(MSG_INFO, "EAP-PWD (peer): allocation fail");
768 goto fin;
769 }
770
771 /*
772 * commit is H(k | peer_element | peer_scalar | server_element |
773 * server_scalar | ciphersuite)
774 */
775 hash = eap_pwd_h_init();
776 if (hash == NULL)
777 goto fin;
778
779 /* k */
780 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
781 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(data->k);
782 BN_bn2bin(data->k, cruft + offset);
783 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->prime));
784
785 /* peer element: x, y */
786 if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
787 data->peer_element, x, y,
788 data->bnctx)) {
789 wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
790 "assignment fail");
791 goto fin;
792 }
793 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
794 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(x);
795 BN_bn2bin(x, cruft + offset);
796 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->prime));
797 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
798 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(y);
799 BN_bn2bin(y, cruft + offset);
800 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->prime));
801
802 /* peer scalar */
803 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
804 offset = BN_num_bytes(data->grp->order) -
805 BN_num_bytes(data->peer_scalar);
806 BN_bn2bin(data->peer_scalar, cruft + offset);
807 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->order));
808
809 /* server element: x, y */
810 if (!EC_POINT_get_affine_coordinates_GFp(data->grp->group,
811 data->my_element, x, y,
812 data->bnctx)) {
813 wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
814 "assignment fail");
815 goto fin;
816 }
817
818 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
819 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(x);
820 BN_bn2bin(x, cruft + offset);
821 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->prime));
822 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
823 offset = BN_num_bytes(data->grp->prime) - BN_num_bytes(y);
824 BN_bn2bin(y, cruft + offset);
825 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->prime));
826
827 /* server scalar */
828 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
829 offset = BN_num_bytes(data->grp->order) -
830 BN_num_bytes(data->my_scalar);
831 BN_bn2bin(data->my_scalar, cruft + offset);
832 eap_pwd_h_update(hash, cruft, BN_num_bytes(data->grp->order));
833
834 /* ciphersuite */
835 os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
836 eap_pwd_h_update(hash, (u8 *) &cs, sizeof(u32));
837
838 /* all done */
839 eap_pwd_h_final(hash, conf);
840
841 ptr = (u8 *) payload;
842 if (os_memcmp_const(conf, ptr, SHA256_MAC_LEN)) {
843 wpa_printf(MSG_INFO, "EAP-PWD (server): confirm did not "
844 "verify");
845 goto fin;
846 }
847
848 wpa_printf(MSG_DEBUG, "EAP-pwd (server): confirm verified");
849 if (compute_keys(data->grp, data->bnctx, data->k,
850 data->peer_scalar, data->my_scalar, conf,
851 data->my_confirm, &cs, data->msk, data->emsk,
852 data->session_id) < 0)
853 eap_pwd_state(data, FAILURE);
854 else
855 eap_pwd_state(data, SUCCESS);
856
857 fin:
858 bin_clear_free(cruft, BN_num_bytes(data->grp->prime));
859 BN_clear_free(x);
860 BN_clear_free(y);
861 }
862
863
eap_pwd_process(struct eap_sm * sm,void * priv,struct wpabuf * respData)864 static void eap_pwd_process(struct eap_sm *sm, void *priv,
865 struct wpabuf *respData)
866 {
867 struct eap_pwd_data *data = priv;
868 const u8 *pos;
869 size_t len;
870 u8 lm_exch;
871 u16 tot_len;
872
873 pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PWD, respData, &len);
874 if ((pos == NULL) || (len < 1)) {
875 wpa_printf(MSG_INFO, "Bad EAP header! pos %s and len = %d",
876 (pos == NULL) ? "is NULL" : "is not NULL",
877 (int) len);
878 return;
879 }
880
881 lm_exch = *pos;
882 pos++; /* skip over the bits and the exch */
883 len--;
884
885 /*
886 * if we're fragmenting then this should be an ACK with no data,
887 * just return and continue fragmenting in the "build" section above
888 */
889 if (data->out_frag_pos) {
890 if (len > 1)
891 wpa_printf(MSG_INFO, "EAP-pwd: Bad response! "
892 "Fragmenting but not an ACK");
893 else
894 wpa_printf(MSG_DEBUG, "EAP-pwd: received ACK from "
895 "peer");
896 return;
897 }
898 /*
899 * if we're receiving fragmented packets then we need to buffer...
900 *
901 * the first fragment has a total length
902 */
903 if (EAP_PWD_GET_LENGTH_BIT(lm_exch)) {
904 tot_len = WPA_GET_BE16(pos);
905 wpa_printf(MSG_DEBUG, "EAP-pwd: Incoming fragments, total "
906 "length = %d", tot_len);
907 if (tot_len > 15000)
908 return;
909 data->inbuf = wpabuf_alloc(tot_len);
910 if (data->inbuf == NULL) {
911 wpa_printf(MSG_INFO, "EAP-pwd: Out of memory to "
912 "buffer fragments!");
913 return;
914 }
915 pos += sizeof(u16);
916 len -= sizeof(u16);
917 }
918 /*
919 * the first and all intermediate fragments have the M bit set
920 */
921 if (EAP_PWD_GET_MORE_BIT(lm_exch)) {
922 if ((data->in_frag_pos + len) > wpabuf_size(data->inbuf)) {
923 wpa_printf(MSG_DEBUG, "EAP-pwd: Buffer overflow "
924 "attack detected! (%d+%d > %d)",
925 (int) data->in_frag_pos, (int) len,
926 (int) wpabuf_size(data->inbuf));
927 eap_pwd_state(data, FAILURE);
928 return;
929 }
930 wpabuf_put_data(data->inbuf, pos, len);
931 data->in_frag_pos += len;
932 wpa_printf(MSG_DEBUG, "EAP-pwd: Got a %d byte fragment",
933 (int) len);
934 return;
935 }
936 /*
937 * last fragment won't have the M bit set (but we're obviously
938 * buffering fragments so that's how we know it's the last)
939 */
940 if (data->in_frag_pos) {
941 wpabuf_put_data(data->inbuf, pos, len);
942 data->in_frag_pos += len;
943 pos = wpabuf_head_u8(data->inbuf);
944 len = data->in_frag_pos;
945 wpa_printf(MSG_DEBUG, "EAP-pwd: Last fragment, %d bytes",
946 (int) len);
947 }
948 switch (EAP_PWD_GET_EXCHANGE(lm_exch)) {
949 case EAP_PWD_OPCODE_ID_EXCH:
950 eap_pwd_process_id_resp(sm, data, pos, len);
951 break;
952 case EAP_PWD_OPCODE_COMMIT_EXCH:
953 eap_pwd_process_commit_resp(sm, data, pos, len);
954 break;
955 case EAP_PWD_OPCODE_CONFIRM_EXCH:
956 eap_pwd_process_confirm_resp(sm, data, pos, len);
957 break;
958 }
959 /*
960 * if we had been buffering fragments, here's a great place
961 * to clean up
962 */
963 if (data->in_frag_pos) {
964 wpabuf_free(data->inbuf);
965 data->inbuf = NULL;
966 data->in_frag_pos = 0;
967 }
968 }
969
970
eap_pwd_getkey(struct eap_sm * sm,void * priv,size_t * len)971 static u8 * eap_pwd_getkey(struct eap_sm *sm, void *priv, size_t *len)
972 {
973 struct eap_pwd_data *data = priv;
974 u8 *key;
975
976 if (data->state != SUCCESS)
977 return NULL;
978
979 key = os_malloc(EAP_MSK_LEN);
980 if (key == NULL)
981 return NULL;
982
983 os_memcpy(key, data->msk, EAP_MSK_LEN);
984 *len = EAP_MSK_LEN;
985
986 return key;
987 }
988
989
eap_pwd_get_emsk(struct eap_sm * sm,void * priv,size_t * len)990 static u8 * eap_pwd_get_emsk(struct eap_sm *sm, void *priv, size_t *len)
991 {
992 struct eap_pwd_data *data = priv;
993 u8 *key;
994
995 if (data->state != SUCCESS)
996 return NULL;
997
998 key = os_malloc(EAP_EMSK_LEN);
999 if (key == NULL)
1000 return NULL;
1001
1002 os_memcpy(key, data->emsk, EAP_EMSK_LEN);
1003 *len = EAP_EMSK_LEN;
1004
1005 return key;
1006 }
1007
1008
eap_pwd_is_success(struct eap_sm * sm,void * priv)1009 static Boolean eap_pwd_is_success(struct eap_sm *sm, void *priv)
1010 {
1011 struct eap_pwd_data *data = priv;
1012 return data->state == SUCCESS;
1013 }
1014
1015
eap_pwd_is_done(struct eap_sm * sm,void * priv)1016 static Boolean eap_pwd_is_done(struct eap_sm *sm, void *priv)
1017 {
1018 struct eap_pwd_data *data = priv;
1019 return (data->state == SUCCESS) || (data->state == FAILURE);
1020 }
1021
1022
eap_server_pwd_register(void)1023 int eap_server_pwd_register(void)
1024 {
1025 struct eap_method *eap;
1026 int ret;
1027 struct timeval tp;
1028 struct timezone tz;
1029 u32 sr;
1030
1031 EVP_add_digest(EVP_sha256());
1032
1033 sr = 0xdeaddada;
1034 (void) gettimeofday(&tp, &tz);
1035 sr ^= (tp.tv_sec ^ tp.tv_usec);
1036 srandom(sr);
1037
1038 eap = eap_server_method_alloc(EAP_SERVER_METHOD_INTERFACE_VERSION,
1039 EAP_VENDOR_IETF, EAP_TYPE_PWD,
1040 "PWD");
1041 if (eap == NULL)
1042 return -1;
1043
1044 eap->init = eap_pwd_init;
1045 eap->reset = eap_pwd_reset;
1046 eap->buildReq = eap_pwd_build_req;
1047 eap->check = eap_pwd_check;
1048 eap->process = eap_pwd_process;
1049 eap->isDone = eap_pwd_is_done;
1050 eap->getKey = eap_pwd_getkey;
1051 eap->get_emsk = eap_pwd_get_emsk;
1052 eap->isSuccess = eap_pwd_is_success;
1053
1054 ret = eap_server_method_register(eap);
1055 if (ret)
1056 eap_server_method_free(eap);
1057 return ret;
1058 }
1059
1060