1 /*
2 * chap-new.c - New CHAP implementation.
3 *
4 * Copyright (c) 2003 Paul Mackerras. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 *
13 * 2. The name(s) of the authors of this software must not be used to
14 * endorse or promote products derived from this software without
15 * prior written permission.
16 *
17 * 3. Redistributions of any form whatsoever must retain the following
18 * acknowledgment:
19 * "This product includes software developed by Paul Mackerras
20 * <paulus@samba.org>".
21 *
22 * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
23 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
24 * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
25 * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
26 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
27 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
28 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
29 */
30
31 #define RCSID "$Id: chap-new.c,v 1.9 2007/06/19 02:08:35 carlsonj Exp $"
32
33 #include <stdlib.h>
34 #include <string.h>
35 #include "pppd.h"
36 #include "session.h"
37 #include "chap-new.h"
38 #include "chap-md5.h"
39 #if defined(__ANDROID__)
40 #include "openssl-hash.h"
41 #endif
42
43 #ifdef CHAPMS
44 #include "chap_ms.h"
45 #define MDTYPE_ALL (MDTYPE_MICROSOFT_V2 | MDTYPE_MICROSOFT | MDTYPE_MD5)
46 #else
47 #define MDTYPE_ALL (MDTYPE_MD5)
48 #endif
49
50 int chap_mdtype_all = MDTYPE_ALL;
51
52 /* Hook for a plugin to validate CHAP challenge */
53 int (*chap_verify_hook)(char *name, char *ourname, int id,
54 struct chap_digest_type *digest,
55 unsigned char *challenge, unsigned char *response,
56 char *message, int message_space) = NULL;
57
58 /*
59 * Option variables.
60 */
61 int chap_timeout_time = 3;
62 int chap_max_transmits = 10;
63 int chap_rechallenge_time = 0;
64
65 /*
66 * Command-line options.
67 */
68 static option_t chap_option_list[] = {
69 { "chap-restart", o_int, &chap_timeout_time,
70 "Set timeout for CHAP", OPT_PRIO },
71 { "chap-max-challenge", o_int, &chap_max_transmits,
72 "Set max #xmits for challenge", OPT_PRIO },
73 { "chap-interval", o_int, &chap_rechallenge_time,
74 "Set interval for rechallenge", OPT_PRIO },
75 { NULL }
76 };
77
78 /*
79 * Internal state.
80 */
81 static struct chap_client_state {
82 int flags;
83 char *name;
84 struct chap_digest_type *digest;
85 unsigned char priv[64]; /* private area for digest's use */
86 } client;
87
88 /*
89 * These limits apply to challenge and response packets we send.
90 * The +4 is the +1 that we actually need rounded up.
91 */
92 #define CHAL_MAX_PKTLEN (PPP_HDRLEN + CHAP_HDRLEN + 4 + MAX_CHALLENGE_LEN + MAXNAMELEN)
93 #define RESP_MAX_PKTLEN (PPP_HDRLEN + CHAP_HDRLEN + 4 + MAX_RESPONSE_LEN + MAXNAMELEN)
94
95 static struct chap_server_state {
96 int flags;
97 int id;
98 char *name;
99 struct chap_digest_type *digest;
100 int challenge_xmits;
101 int challenge_pktlen;
102 unsigned char challenge[CHAL_MAX_PKTLEN];
103 char message[256];
104 } server;
105
106 /* Values for flags in chap_client_state and chap_server_state */
107 #define LOWERUP 1
108 #define AUTH_STARTED 2
109 #define AUTH_DONE 4
110 #define AUTH_FAILED 8
111 #define TIMEOUT_PENDING 0x10
112 #define CHALLENGE_VALID 0x20
113
114 /*
115 * Prototypes.
116 */
117 static void chap_init(int unit);
118 static void chap_lowerup(int unit);
119 static void chap_lowerdown(int unit);
120 static void chap_timeout(void *arg);
121 static void chap_generate_challenge(struct chap_server_state *ss);
122 static void chap_handle_response(struct chap_server_state *ss, int code,
123 unsigned char *pkt, int len);
124 static int chap_verify_response(char *name, char *ourname, int id,
125 struct chap_digest_type *digest,
126 unsigned char *challenge, unsigned char *response,
127 char *message, int message_space);
128 static void chap_respond(struct chap_client_state *cs, int id,
129 unsigned char *pkt, int len);
130 static void chap_handle_status(struct chap_client_state *cs, int code, int id,
131 unsigned char *pkt, int len);
132 static void chap_protrej(int unit);
133 static void chap_input(int unit, unsigned char *pkt, int pktlen);
134 static int chap_print_pkt(unsigned char *p, int plen,
135 void (*printer) __P((void *, char *, ...)), void *arg);
136
137 /* List of digest types that we know about */
138 static struct chap_digest_type *chap_digests;
139
140 /*
141 * chap_init - reset to initial state.
142 */
143 static void
chap_init(int unit)144 chap_init(int unit)
145 {
146 memset(&client, 0, sizeof(client));
147 memset(&server, 0, sizeof(server));
148
149 chap_md5_init();
150 #ifdef CHAPMS
151 chapms_init();
152 #endif
153 }
154
155 /*
156 * Add a new digest type to the list.
157 */
158 void
chap_register_digest(struct chap_digest_type * dp)159 chap_register_digest(struct chap_digest_type *dp)
160 {
161 dp->next = chap_digests;
162 chap_digests = dp;
163 }
164
165 /*
166 * chap_lowerup - we can start doing stuff now.
167 */
168 static void
chap_lowerup(int unit)169 chap_lowerup(int unit)
170 {
171 struct chap_client_state *cs = &client;
172 struct chap_server_state *ss = &server;
173
174 cs->flags |= LOWERUP;
175 ss->flags |= LOWERUP;
176 if (ss->flags & AUTH_STARTED)
177 chap_timeout(ss);
178 }
179
180 static void
chap_lowerdown(int unit)181 chap_lowerdown(int unit)
182 {
183 struct chap_client_state *cs = &client;
184 struct chap_server_state *ss = &server;
185
186 cs->flags = 0;
187 if (ss->flags & TIMEOUT_PENDING)
188 UNTIMEOUT(chap_timeout, ss);
189 ss->flags = 0;
190 }
191
192 /*
193 * chap_auth_peer - Start authenticating the peer.
194 * If the lower layer is already up, we start sending challenges,
195 * otherwise we wait for the lower layer to come up.
196 */
197 void
chap_auth_peer(int unit,char * our_name,int digest_code)198 chap_auth_peer(int unit, char *our_name, int digest_code)
199 {
200 struct chap_server_state *ss = &server;
201 struct chap_digest_type *dp;
202
203 if (ss->flags & AUTH_STARTED) {
204 error("CHAP: peer authentication already started!");
205 return;
206 }
207 for (dp = chap_digests; dp != NULL; dp = dp->next)
208 if (dp->code == digest_code)
209 break;
210 if (dp == NULL)
211 fatal("CHAP digest 0x%x requested but not available",
212 digest_code);
213
214 ss->digest = dp;
215 ss->name = our_name;
216 /* Start with a random ID value */
217 ss->id = (unsigned char)(drand48() * 256);
218 ss->flags |= AUTH_STARTED;
219 if (ss->flags & LOWERUP)
220 chap_timeout(ss);
221 }
222
223 /*
224 * chap_auth_with_peer - Prepare to authenticate ourselves to the peer.
225 * There isn't much to do until we receive a challenge.
226 */
227 void
chap_auth_with_peer(int unit,char * our_name,int digest_code)228 chap_auth_with_peer(int unit, char *our_name, int digest_code)
229 {
230 struct chap_client_state *cs = &client;
231 struct chap_digest_type *dp;
232
233 if (cs->flags & AUTH_STARTED) {
234 error("CHAP: authentication with peer already started!");
235 return;
236 }
237 for (dp = chap_digests; dp != NULL; dp = dp->next)
238 if (dp->code == digest_code)
239 break;
240 if (dp == NULL)
241 fatal("CHAP digest 0x%x requested but not available",
242 digest_code);
243
244 cs->digest = dp;
245 cs->name = our_name;
246 cs->flags |= AUTH_STARTED;
247 }
248
249 /*
250 * chap_timeout - It's time to send another challenge to the peer.
251 * This could be either a retransmission of a previous challenge,
252 * or a new challenge to start re-authentication.
253 */
254 static void
chap_timeout(void * arg)255 chap_timeout(void *arg)
256 {
257 struct chap_server_state *ss = arg;
258
259 ss->flags &= ~TIMEOUT_PENDING;
260 if ((ss->flags & CHALLENGE_VALID) == 0) {
261 ss->challenge_xmits = 0;
262 chap_generate_challenge(ss);
263 ss->flags |= CHALLENGE_VALID;
264 } else if (ss->challenge_xmits >= chap_max_transmits) {
265 ss->flags &= ~CHALLENGE_VALID;
266 ss->flags |= AUTH_DONE | AUTH_FAILED;
267 auth_peer_fail(0, PPP_CHAP);
268 return;
269 }
270
271 output(0, ss->challenge, ss->challenge_pktlen);
272 ++ss->challenge_xmits;
273 ss->flags |= TIMEOUT_PENDING;
274 TIMEOUT(chap_timeout, arg, chap_timeout_time);
275 }
276
277 /*
278 * chap_generate_challenge - generate a challenge string and format
279 * the challenge packet in ss->challenge_pkt.
280 */
281 static void
chap_generate_challenge(struct chap_server_state * ss)282 chap_generate_challenge(struct chap_server_state *ss)
283 {
284 int clen = 1, nlen, len;
285 unsigned char *p;
286
287 p = ss->challenge;
288 MAKEHEADER(p, PPP_CHAP);
289 p += CHAP_HDRLEN;
290 ss->digest->generate_challenge(p);
291 clen = *p;
292 nlen = strlen(ss->name);
293 memcpy(p + 1 + clen, ss->name, nlen);
294
295 len = CHAP_HDRLEN + 1 + clen + nlen;
296 ss->challenge_pktlen = PPP_HDRLEN + len;
297
298 p = ss->challenge + PPP_HDRLEN;
299 p[0] = CHAP_CHALLENGE;
300 p[1] = ++ss->id;
301 p[2] = len >> 8;
302 p[3] = len;
303 }
304
305 /*
306 * chap_handle_response - check the response to our challenge.
307 */
308 static void
chap_handle_response(struct chap_server_state * ss,int id,unsigned char * pkt,int len)309 chap_handle_response(struct chap_server_state *ss, int id,
310 unsigned char *pkt, int len)
311 {
312 int response_len, ok, mlen;
313 unsigned char *response, *p;
314 char *name = NULL; /* initialized to shut gcc up */
315 int (*verifier)(char *, char *, int, struct chap_digest_type *,
316 unsigned char *, unsigned char *, char *, int);
317 char rname[MAXNAMELEN+1];
318
319 if ((ss->flags & LOWERUP) == 0)
320 return;
321 if (id != ss->challenge[PPP_HDRLEN+1] || len < 2)
322 return;
323 if (ss->flags & CHALLENGE_VALID) {
324 response = pkt;
325 GETCHAR(response_len, pkt);
326 len -= response_len + 1; /* length of name */
327 name = (char *)pkt + response_len;
328 if (len < 0)
329 return;
330
331 if (ss->flags & TIMEOUT_PENDING) {
332 ss->flags &= ~TIMEOUT_PENDING;
333 UNTIMEOUT(chap_timeout, ss);
334 }
335
336 if (explicit_remote) {
337 name = remote_name;
338 } else {
339 /* Null terminate and clean remote name. */
340 slprintf(rname, sizeof(rname), "%.*v", len, name);
341 name = rname;
342 }
343
344 if (chap_verify_hook)
345 verifier = chap_verify_hook;
346 else
347 verifier = chap_verify_response;
348 ok = (*verifier)(name, ss->name, id, ss->digest,
349 ss->challenge + PPP_HDRLEN + CHAP_HDRLEN,
350 response, ss->message, sizeof(ss->message));
351 if (!ok || !auth_number()) {
352 ss->flags |= AUTH_FAILED;
353 warn("Peer %q failed CHAP authentication", name);
354 }
355 } else if ((ss->flags & AUTH_DONE) == 0)
356 return;
357
358 /* send the response */
359 p = outpacket_buf;
360 MAKEHEADER(p, PPP_CHAP);
361 mlen = strlen(ss->message);
362 len = CHAP_HDRLEN + mlen;
363 p[0] = (ss->flags & AUTH_FAILED)? CHAP_FAILURE: CHAP_SUCCESS;
364 p[1] = id;
365 p[2] = len >> 8;
366 p[3] = len;
367 if (mlen > 0)
368 memcpy(p + CHAP_HDRLEN, ss->message, mlen);
369 output(0, outpacket_buf, PPP_HDRLEN + len);
370
371 if (ss->flags & CHALLENGE_VALID) {
372 ss->flags &= ~CHALLENGE_VALID;
373 if (!(ss->flags & AUTH_DONE) && !(ss->flags & AUTH_FAILED)) {
374 /*
375 * Auth is OK, so now we need to check session restrictions
376 * to ensure everything is OK, but only if we used a
377 * plugin, and only if we're configured to check. This
378 * allows us to do PAM checks on PPP servers that
379 * authenticate against ActiveDirectory, and use AD for
380 * account info (like when using Winbind integrated with
381 * PAM).
382 */
383 if (session_mgmt &&
384 session_check(name, NULL, devnam, NULL) == 0) {
385 ss->flags |= AUTH_FAILED;
386 warn("Peer %q failed CHAP Session verification", name);
387 }
388 }
389 if (ss->flags & AUTH_FAILED) {
390 auth_peer_fail(0, PPP_CHAP);
391 } else {
392 if ((ss->flags & AUTH_DONE) == 0)
393 auth_peer_success(0, PPP_CHAP,
394 ss->digest->code,
395 name, strlen(name));
396 if (chap_rechallenge_time) {
397 ss->flags |= TIMEOUT_PENDING;
398 TIMEOUT(chap_timeout, ss,
399 chap_rechallenge_time);
400 }
401 }
402 ss->flags |= AUTH_DONE;
403 }
404 }
405
406 /*
407 * chap_verify_response - check whether the peer's response matches
408 * what we think it should be. Returns 1 if it does (authentication
409 * succeeded), or 0 if it doesn't.
410 */
411 static int
chap_verify_response(char * name,char * ourname,int id,struct chap_digest_type * digest,unsigned char * challenge,unsigned char * response,char * message,int message_space)412 chap_verify_response(char *name, char *ourname, int id,
413 struct chap_digest_type *digest,
414 unsigned char *challenge, unsigned char *response,
415 char *message, int message_space)
416 {
417 int ok;
418 unsigned char secret[MAXSECRETLEN];
419 int secret_len;
420
421 /* Get the secret that the peer is supposed to know */
422 if (!get_secret(0, name, ourname, (char *)secret, &secret_len, 1)) {
423 error("No CHAP secret found for authenticating %q", name);
424 return 0;
425 }
426
427 ok = digest->verify_response(id, name, secret, secret_len, challenge,
428 response, message, message_space);
429 memset(secret, 0, sizeof(secret));
430
431 return ok;
432 }
433
434 /*
435 * chap_respond - Generate and send a response to a challenge.
436 */
437 static void
chap_respond(struct chap_client_state * cs,int id,unsigned char * pkt,int len)438 chap_respond(struct chap_client_state *cs, int id,
439 unsigned char *pkt, int len)
440 {
441 int clen, nlen;
442 int secret_len;
443 unsigned char *p;
444 unsigned char response[RESP_MAX_PKTLEN];
445 char rname[MAXNAMELEN+1];
446 char secret[MAXSECRETLEN+1];
447
448 if ((cs->flags & (LOWERUP | AUTH_STARTED)) != (LOWERUP | AUTH_STARTED))
449 return; /* not ready */
450 if (len < 2 || len < pkt[0] + 1)
451 return; /* too short */
452 clen = pkt[0];
453 nlen = len - (clen + 1);
454
455 /* Null terminate and clean remote name. */
456 slprintf(rname, sizeof(rname), "%.*v", nlen, pkt + clen + 1);
457
458 /* Microsoft doesn't send their name back in the PPP packet */
459 if (explicit_remote || (remote_name[0] != 0 && rname[0] == 0))
460 strlcpy(rname, remote_name, sizeof(rname));
461
462 /* get secret for authenticating ourselves with the specified host */
463 if (!get_secret(0, cs->name, rname, secret, &secret_len, 0)) {
464 secret_len = 0; /* assume null secret if can't find one */
465 warn("No CHAP secret found for authenticating us to %q", rname);
466 }
467
468 p = response;
469 MAKEHEADER(p, PPP_CHAP);
470 p += CHAP_HDRLEN;
471
472 cs->digest->make_response(p, id, cs->name, pkt,
473 secret, secret_len, cs->priv);
474 memset(secret, 0, secret_len);
475
476 clen = *p;
477 nlen = strlen(cs->name);
478 memcpy(p + clen + 1, cs->name, nlen);
479
480 p = response + PPP_HDRLEN;
481 len = CHAP_HDRLEN + clen + 1 + nlen;
482 p[0] = CHAP_RESPONSE;
483 p[1] = id;
484 p[2] = len >> 8;
485 p[3] = len;
486
487 output(0, response, PPP_HDRLEN + len);
488 }
489
490 static void
chap_handle_status(struct chap_client_state * cs,int code,int id,unsigned char * pkt,int len)491 chap_handle_status(struct chap_client_state *cs, int code, int id,
492 unsigned char *pkt, int len)
493 {
494 const char *msg = NULL;
495
496 if ((cs->flags & (AUTH_DONE|AUTH_STARTED|LOWERUP))
497 != (AUTH_STARTED|LOWERUP))
498 return;
499 cs->flags |= AUTH_DONE;
500
501 if (code == CHAP_SUCCESS) {
502 /* used for MS-CHAP v2 mutual auth, yuck */
503 if (cs->digest->check_success != NULL) {
504 if (!(*cs->digest->check_success)(id, pkt, len))
505 code = CHAP_FAILURE;
506 } else
507 msg = "CHAP authentication succeeded";
508 } else {
509 if (cs->digest->handle_failure != NULL)
510 (*cs->digest->handle_failure)(pkt, len);
511 else
512 msg = "CHAP authentication failed";
513 }
514 if (msg) {
515 if (len > 0)
516 info("%s: %.*v", msg, len, pkt);
517 else
518 info("%s", msg);
519 }
520 if (code == CHAP_SUCCESS)
521 auth_withpeer_success(0, PPP_CHAP, cs->digest->code);
522 else {
523 cs->flags |= AUTH_FAILED;
524 error("CHAP authentication failed");
525 auth_withpeer_fail(0, PPP_CHAP);
526 }
527 }
528
529 static void
chap_input(int unit,unsigned char * pkt,int pktlen)530 chap_input(int unit, unsigned char *pkt, int pktlen)
531 {
532 struct chap_client_state *cs = &client;
533 struct chap_server_state *ss = &server;
534 unsigned char code, id;
535 int len;
536
537 if (pktlen < CHAP_HDRLEN)
538 return;
539 GETCHAR(code, pkt);
540 GETCHAR(id, pkt);
541 GETSHORT(len, pkt);
542 if (len < CHAP_HDRLEN || len > pktlen)
543 return;
544 len -= CHAP_HDRLEN;
545
546 switch (code) {
547 case CHAP_CHALLENGE:
548 chap_respond(cs, id, pkt, len);
549 break;
550 case CHAP_RESPONSE:
551 chap_handle_response(ss, id, pkt, len);
552 break;
553 case CHAP_FAILURE:
554 case CHAP_SUCCESS:
555 chap_handle_status(cs, code, id, pkt, len);
556 break;
557 }
558 }
559
560 static void
chap_protrej(int unit)561 chap_protrej(int unit)
562 {
563 struct chap_client_state *cs = &client;
564 struct chap_server_state *ss = &server;
565
566 if (ss->flags & TIMEOUT_PENDING) {
567 ss->flags &= ~TIMEOUT_PENDING;
568 UNTIMEOUT(chap_timeout, ss);
569 }
570 if (ss->flags & AUTH_STARTED) {
571 ss->flags = 0;
572 auth_peer_fail(0, PPP_CHAP);
573 }
574 if ((cs->flags & (AUTH_STARTED|AUTH_DONE)) == AUTH_STARTED) {
575 cs->flags &= ~AUTH_STARTED;
576 error("CHAP authentication failed due to protocol-reject");
577 auth_withpeer_fail(0, PPP_CHAP);
578 }
579 }
580
581 /*
582 * chap_print_pkt - print the contents of a CHAP packet.
583 */
584 static char *chap_code_names[] = {
585 "Challenge", "Response", "Success", "Failure"
586 };
587
588 static int
chap_print_pkt(unsigned char * p,int plen,void (* printer)__P ((void *,char *,...)),void * arg)589 chap_print_pkt(unsigned char *p, int plen,
590 void (*printer) __P((void *, char *, ...)), void *arg)
591 {
592 int code, id, len;
593 int clen, nlen;
594 unsigned char x;
595
596 if (plen < CHAP_HDRLEN)
597 return 0;
598 GETCHAR(code, p);
599 GETCHAR(id, p);
600 GETSHORT(len, p);
601 if (len < CHAP_HDRLEN || len > plen)
602 return 0;
603
604 if (code >= 1 && code <= sizeof(chap_code_names) / sizeof(char *))
605 printer(arg, " %s", chap_code_names[code-1]);
606 else
607 printer(arg, " code=0x%x", code);
608 printer(arg, " id=0x%x", id);
609 len -= CHAP_HDRLEN;
610 switch (code) {
611 case CHAP_CHALLENGE:
612 case CHAP_RESPONSE:
613 if (len < 1)
614 break;
615 clen = p[0];
616 if (len < clen + 1)
617 break;
618 ++p;
619 nlen = len - clen - 1;
620 printer(arg, " <");
621 for (; clen > 0; --clen) {
622 GETCHAR(x, p);
623 printer(arg, "%.2x", x);
624 }
625 printer(arg, ">, name = ");
626 print_string((char *)p, nlen, printer, arg);
627 break;
628 case CHAP_FAILURE:
629 case CHAP_SUCCESS:
630 printer(arg, " ");
631 print_string((char *)p, len, printer, arg);
632 break;
633 default:
634 for (clen = len; clen > 0; --clen) {
635 GETCHAR(x, p);
636 printer(arg, " %.2x", x);
637 }
638 }
639
640 return len + CHAP_HDRLEN;
641 }
642
643 struct protent chap_protent = {
644 PPP_CHAP,
645 chap_init,
646 chap_input,
647 chap_protrej,
648 chap_lowerup,
649 chap_lowerdown,
650 NULL, /* open */
651 NULL, /* close */
652 chap_print_pkt,
653 NULL, /* datainput */
654 1, /* enabled_flag */
655 "CHAP", /* name */
656 NULL, /* data_name */
657 chap_option_list,
658 NULL, /* check_options */
659 };
660