1 /*
2 * Copyright (C) 2012 by Darren Reed.
3 *
4 * Simple PPTP transparent proxy for in-kernel use. For use with the NAT
5 * code.
6 *
7 * $Id$
8 *
9 */
10 #define IPF_PPTP_PROXY
11
12
13
14 /*
15 * PPTP proxy
16 */
17 typedef struct pptp_side {
18 u_32_t pptps_nexthdr;
19 u_32_t pptps_next;
20 int pptps_state;
21 int pptps_gothdr;
22 int pptps_len;
23 int pptps_bytes;
24 char *pptps_wptr;
25 char pptps_buffer[512];
26 } pptp_side_t;
27
28 typedef struct pptp_pxy {
29 nat_t *pptp_nat;
30 struct ipstate *pptp_state;
31 u_short pptp_call[2];
32 pptp_side_t pptp_side[2];
33 ipnat_t *pptp_rule;
34 } pptp_pxy_t;
35
36 typedef struct pptp_hdr {
37 u_short pptph_len;
38 u_short pptph_type;
39 u_32_t pptph_cookie;
40 } pptp_hdr_t;
41
42 #define PPTP_MSGTYPE_CTL 1
43 #define PPTP_MTCTL_STARTREQ 1
44 #define PPTP_MTCTL_STARTREP 2
45 #define PPTP_MTCTL_STOPREQ 3
46 #define PPTP_MTCTL_STOPREP 4
47 #define PPTP_MTCTL_ECHOREQ 5
48 #define PPTP_MTCTL_ECHOREP 6
49 #define PPTP_MTCTL_OUTREQ 7
50 #define PPTP_MTCTL_OUTREP 8
51 #define PPTP_MTCTL_INREQ 9
52 #define PPTP_MTCTL_INREP 10
53 #define PPTP_MTCTL_INCONNECT 11
54 #define PPTP_MTCTL_CLEAR 12
55 #define PPTP_MTCTL_DISCONNECT 13
56 #define PPTP_MTCTL_WANERROR 14
57 #define PPTP_MTCTL_LINKINFO 15
58
59
60 void ipf_p_pptp_main_load(void);
61 void ipf_p_pptp_main_unload(void);
62 int ipf_p_pptp_new(void *, fr_info_t *, ap_session_t *, nat_t *);
63 void ipf_p_pptp_del(ipf_main_softc_t *, ap_session_t *);
64 int ipf_p_pptp_inout(void *, fr_info_t *, ap_session_t *, nat_t *);
65 void ipf_p_pptp_donatstate(fr_info_t *, nat_t *, pptp_pxy_t *);
66 int ipf_p_pptp_message(fr_info_t *, nat_t *, pptp_pxy_t *, pptp_side_t *);
67 int ipf_p_pptp_nextmessage(fr_info_t *, nat_t *, pptp_pxy_t *, int);
68 int ipf_p_pptp_mctl(fr_info_t *, nat_t *, pptp_pxy_t *, pptp_side_t *);
69
70 static frentry_t pptpfr;
71
72 static int pptp_proxy_init = 0;
73 static int ipf_p_pptp_debug = 0;
74 static int ipf_p_pptp_gretimeout = IPF_TTLVAL(120); /* 2 minutes */
75
76
77 /*
78 * PPTP application proxy initialization.
79 */
80 void
ipf_p_pptp_main_load(void)81 ipf_p_pptp_main_load(void)
82 {
83 bzero((char *)&pptpfr, sizeof(pptpfr));
84 pptpfr.fr_ref = 1;
85 pptpfr.fr_age[0] = ipf_p_pptp_gretimeout;
86 pptpfr.fr_age[1] = ipf_p_pptp_gretimeout;
87 pptpfr.fr_flags = FR_OUTQUE|FR_PASS|FR_QUICK|FR_KEEPSTATE;
88 MUTEX_INIT(&pptpfr.fr_lock, "PPTP proxy rule lock");
89 pptp_proxy_init = 1;
90 }
91
92
93 void
ipf_p_pptp_main_unload(void)94 ipf_p_pptp_main_unload(void)
95 {
96 if (pptp_proxy_init == 1) {
97 MUTEX_DESTROY(&pptpfr.fr_lock);
98 pptp_proxy_init = 0;
99 }
100 }
101
102
103 /*
104 * Setup for a new PPTP proxy.
105 *
106 * NOTE: The printf's are broken up with %s in them to prevent them being
107 * optimised into puts statements on FreeBSD (this doesn't exist in the kernel)
108 */
109 int
ipf_p_pptp_new(void * arg,fr_info_t * fin,ap_session_t * aps,nat_t * nat)110 ipf_p_pptp_new(void *arg, fr_info_t *fin, ap_session_t *aps, nat_t *nat)
111 {
112 pptp_pxy_t *pptp;
113 ipnat_t *ipn;
114 ipnat_t *np;
115 int size;
116 ip_t *ip;
117
118 if (fin->fin_v != 4)
119 return (-1);
120
121 ip = fin->fin_ip;
122 np = nat->nat_ptr;
123 size = np->in_size;
124
125 if (ipf_nat_outlookup(fin, 0, IPPROTO_GRE, nat->nat_osrcip,
126 ip->ip_dst) != NULL) {
127 if (ipf_p_pptp_debug > 0)
128 printf("ipf_p_pptp_new: GRE session already exists\n");
129 return (-1);
130 }
131
132 KMALLOC(pptp, pptp_pxy_t *);
133 if (pptp == NULL) {
134 if (ipf_p_pptp_debug > 0)
135 printf("ipf_p_pptp_new: malloc for aps_data failed\n");
136 return (-1);
137 }
138 KMALLOCS(ipn, ipnat_t *, size);
139 if (ipn == NULL) {
140 KFREE(pptp);
141 return (-1);
142 }
143
144 aps->aps_data = pptp;
145 aps->aps_psiz = sizeof(*pptp);
146 bzero((char *)pptp, sizeof(*pptp));
147 bzero((char *)ipn, size);
148 pptp->pptp_rule = ipn;
149
150 /*
151 * Create NAT rule against which the tunnel/transport mapping is
152 * created. This is required because the current NAT rule does not
153 * describe GRE but TCP instead.
154 */
155 ipn->in_size = size;
156 ipn->in_ifps[0] = fin->fin_ifp;
157 ipn->in_apr = NULL;
158 ipn->in_use = 1;
159 ipn->in_hits = 1;
160 ipn->in_ippip = 1;
161 ipn->in_snip = ntohl(nat->nat_nsrcaddr);
162 ipn->in_nsrcaddr = fin->fin_saddr;
163 ipn->in_dnip = ntohl(nat->nat_ndstaddr);
164 ipn->in_ndstaddr = nat->nat_ndstaddr;
165 ipn->in_redir = np->in_redir;
166 ipn->in_osrcaddr = nat->nat_osrcaddr;
167 ipn->in_odstaddr = nat->nat_odstaddr;
168 ipn->in_osrcmsk = 0xffffffff;
169 ipn->in_nsrcmsk = 0xffffffff;
170 ipn->in_odstmsk = 0xffffffff;
171 ipn->in_ndstmsk = 0xffffffff;
172 ipn->in_flags = (np->in_flags | IPN_PROXYRULE);
173 MUTEX_INIT(&ipn->in_lock, "pptp proxy NAT rule");
174
175 ipn->in_namelen = np->in_namelen;
176 bcopy(np->in_names, ipn->in_ifnames, ipn->in_namelen);
177 ipn->in_ifnames[0] = np->in_ifnames[0];
178 ipn->in_ifnames[1] = np->in_ifnames[1];
179
180 ipn->in_pr[0] = IPPROTO_GRE;
181 ipn->in_pr[1] = IPPROTO_GRE;
182
183 pptp->pptp_side[0].pptps_wptr = pptp->pptp_side[0].pptps_buffer;
184 pptp->pptp_side[1].pptps_wptr = pptp->pptp_side[1].pptps_buffer;
185 return (0);
186 }
187
188
189 void
ipf_p_pptp_donatstate(fr_info_t * fin,nat_t * nat,pptp_pxy_t * pptp)190 ipf_p_pptp_donatstate(fr_info_t *fin, nat_t *nat, pptp_pxy_t *pptp)
191 {
192 ipf_main_softc_t *softc = fin->fin_main_soft;
193 fr_info_t fi;
194 grehdr_t gre;
195 nat_t *nat2;
196 u_char p;
197 ip_t *ip;
198
199 ip = fin->fin_ip;
200 p = ip->ip_p;
201
202 nat2 = pptp->pptp_nat;
203 if ((nat2 == NULL) || (pptp->pptp_state == NULL)) {
204 bcopy((char *)fin, (char *)&fi, sizeof(fi));
205 bzero((char *)&gre, sizeof(gre));
206 fi.fin_fi.fi_p = IPPROTO_GRE;
207 fi.fin_fr = &pptpfr;
208 if ((nat->nat_dir == NAT_OUTBOUND && fin->fin_out) ||
209 (nat->nat_dir == NAT_INBOUND && !fin->fin_out)) {
210 fi.fin_data[0] = pptp->pptp_call[0];
211 fi.fin_data[1] = pptp->pptp_call[1];
212 } else {
213 fi.fin_data[0] = pptp->pptp_call[1];
214 fi.fin_data[1] = pptp->pptp_call[0];
215 }
216 ip = fin->fin_ip;
217 ip->ip_p = IPPROTO_GRE;
218 fi.fin_flx &= ~(FI_TCPUDP|FI_STATE|FI_FRAG);
219 fi.fin_flx |= FI_IGNORE;
220 fi.fin_dp = &gre;
221 gre.gr_flags = htons(1 << 13);
222
223 fi.fin_fi.fi_saddr = nat->nat_osrcaddr;
224 fi.fin_fi.fi_daddr = nat->nat_odstaddr;
225 }
226
227 /*
228 * Update NAT timeout/create NAT if missing.
229 */
230 if (nat2 != NULL)
231 ipf_queueback(softc->ipf_ticks, &nat2->nat_tqe);
232 else {
233 #ifdef USE_MUTEXES
234 ipf_nat_softc_t *softn = softc->ipf_nat_soft;
235 #endif
236
237 MUTEX_ENTER(&softn->ipf_nat_new);
238 nat2 = ipf_nat_add(&fi, pptp->pptp_rule, &pptp->pptp_nat,
239 NAT_SLAVE, nat->nat_dir);
240 MUTEX_EXIT(&softn->ipf_nat_new);
241 if (nat2 != NULL) {
242 (void) ipf_nat_proto(&fi, nat2, 0);
243 MUTEX_ENTER(&nat2->nat_lock);
244 ipf_nat_update(&fi, nat2);
245 MUTEX_EXIT(&nat2->nat_lock);
246 }
247 }
248
249 READ_ENTER(&softc->ipf_state);
250 if (pptp->pptp_state != NULL) {
251 ipf_queueback(softc->ipf_ticks, &pptp->pptp_state->is_sti);
252 RWLOCK_EXIT(&softc->ipf_state);
253 } else {
254 RWLOCK_EXIT(&softc->ipf_state);
255 if (nat2 != NULL) {
256 if (nat->nat_dir == NAT_INBOUND)
257 fi.fin_fi.fi_daddr = nat2->nat_ndstaddr;
258 else
259 fi.fin_fi.fi_saddr = nat2->nat_osrcaddr;
260 }
261 fi.fin_ifp = NULL;
262 (void) ipf_state_add(softc, &fi, &pptp->pptp_state, 0);
263 }
264 ip->ip_p = p;
265 return;
266 }
267
268
269 /*
270 * Try and build up the next PPTP message in the TCP stream and if we can
271 * build it up completely (fits in our buffer) then pass it off to the message
272 * parsing function.
273 */
274 int
ipf_p_pptp_nextmessage(fr_info_t * fin,nat_t * nat,pptp_pxy_t * pptp,int rev)275 ipf_p_pptp_nextmessage(fr_info_t *fin, nat_t *nat, pptp_pxy_t *pptp, int rev)
276 {
277 static const char *funcname = "ipf_p_pptp_nextmessage";
278 pptp_side_t *pptps;
279 u_32_t start, end;
280 pptp_hdr_t *hdr;
281 tcphdr_t *tcp;
282 int dlen, off;
283 u_short len;
284
285 tcp = fin->fin_dp;
286 dlen = fin->fin_dlen - (TCP_OFF(tcp) << 2);
287 start = ntohl(tcp->th_seq);
288 pptps = &pptp->pptp_side[rev];
289 off = (char *)tcp - (char *)fin->fin_ip + (TCP_OFF(tcp) << 2) +
290 fin->fin_ipoff;
291
292 if (dlen <= 0)
293 return (0);
294 /*
295 * If the complete data packet is before what we expect to see
296 * "next", just ignore it as the chances are we've already seen it.
297 * The next if statement following this one really just causes packets
298 * ahead of what we've seen to be dropped, implying that something in
299 * the middle went missing and we want to see that first.
300 */
301 end = start + dlen;
302 if (pptps->pptps_next > end && pptps->pptps_next > start)
303 return (0);
304
305 if (pptps->pptps_next != start) {
306 if (ipf_p_pptp_debug > 5)
307 printf("%s: next (%x) != start (%x)\n", funcname,
308 pptps->pptps_next, start);
309 return (-1);
310 }
311
312 while (dlen > 0) {
313 off += pptps->pptps_bytes;
314 if (pptps->pptps_gothdr == 0) {
315 /*
316 * PPTP has an 8 byte header that inclues the cookie.
317 * The start of every message should include one and
318 * it should match 1a2b3c4d. Byte order is ignored,
319 * deliberately, when printing out the error.
320 */
321 len = MIN(8 - pptps->pptps_bytes, dlen);
322 COPYDATA(fin->fin_m, off, len, pptps->pptps_wptr);
323 pptps->pptps_bytes += len;
324 pptps->pptps_wptr += len;
325 hdr = (pptp_hdr_t *)pptps->pptps_buffer;
326 if (pptps->pptps_bytes == 8) {
327 pptps->pptps_next += 8;
328 if (ntohl(hdr->pptph_cookie) != 0x1a2b3c4d) {
329 if (ipf_p_pptp_debug > 1)
330 printf("%s: bad cookie (%x)\n",
331 funcname,
332 hdr->pptph_cookie);
333 return (-1);
334 }
335 }
336 dlen -= len;
337 off += len;
338
339 pptps->pptps_gothdr = 1;
340 len = ntohs(hdr->pptph_len);
341 pptps->pptps_len = len;
342 pptps->pptps_nexthdr += len;
343
344 /*
345 * If a message is too big for the buffer, just set
346 * the fields for the next message to come along.
347 * The messages defined in RFC 2637 will not exceed
348 * 512 bytes (in total length) so this is likely a
349 * bad data packet, anyway.
350 */
351 if (len > sizeof(pptps->pptps_buffer)) {
352 if (ipf_p_pptp_debug > 3)
353 printf("%s: message too big (%d)\n",
354 funcname, len);
355 pptps->pptps_next = pptps->pptps_nexthdr;
356 pptps->pptps_wptr = pptps->pptps_buffer;
357 pptps->pptps_gothdr = 0;
358 pptps->pptps_bytes = 0;
359 pptps->pptps_len = 0;
360 break;
361 }
362 }
363
364 len = MIN(pptps->pptps_len - pptps->pptps_bytes, dlen);
365 COPYDATA(fin->fin_m, off, len, pptps->pptps_wptr);
366 pptps->pptps_bytes += len;
367 pptps->pptps_wptr += len;
368 pptps->pptps_next += len;
369
370 if (pptps->pptps_len > pptps->pptps_bytes)
371 break;
372
373 ipf_p_pptp_message(fin, nat, pptp, pptps);
374 pptps->pptps_wptr = pptps->pptps_buffer;
375 pptps->pptps_gothdr = 0;
376 pptps->pptps_bytes = 0;
377 pptps->pptps_len = 0;
378
379 start += len;
380 dlen -= len;
381 }
382
383 return (0);
384 }
385
386
387 /*
388 * handle a complete PPTP message
389 */
390 int
ipf_p_pptp_message(fr_info_t * fin,nat_t * nat,pptp_pxy_t * pptp,pptp_side_t * pptps)391 ipf_p_pptp_message(fr_info_t *fin, nat_t *nat, pptp_pxy_t *pptp,
392 pptp_side_t *pptps)
393 {
394 pptp_hdr_t *hdr = (pptp_hdr_t *)pptps->pptps_buffer;
395
396 switch (ntohs(hdr->pptph_type))
397 {
398 case PPTP_MSGTYPE_CTL :
399 ipf_p_pptp_mctl(fin, nat, pptp, pptps);
400 break;
401
402 default :
403 break;
404 }
405 return (0);
406 }
407
408
409 /*
410 * handle a complete PPTP control message
411 */
412 int
ipf_p_pptp_mctl(fr_info_t * fin,nat_t * nat,pptp_pxy_t * pptp,pptp_side_t * pptps)413 ipf_p_pptp_mctl(fr_info_t *fin, nat_t *nat, pptp_pxy_t *pptp,
414 pptp_side_t *pptps)
415 {
416 u_short *buffer = (u_short *)(pptps->pptps_buffer);
417 pptp_side_t *pptpo;
418
419 if (pptps == &pptp->pptp_side[0])
420 pptpo = &pptp->pptp_side[1];
421 else
422 pptpo = &pptp->pptp_side[0];
423
424 /*
425 * Breakout to handle all the various messages. Most are just state
426 * transition.
427 */
428 switch (ntohs(buffer[4]))
429 {
430 case PPTP_MTCTL_STARTREQ :
431 pptps->pptps_state = PPTP_MTCTL_STARTREQ;
432 break;
433 case PPTP_MTCTL_STARTREP :
434 if (pptpo->pptps_state == PPTP_MTCTL_STARTREQ)
435 pptps->pptps_state = PPTP_MTCTL_STARTREP;
436 break;
437 case PPTP_MTCTL_STOPREQ :
438 pptps->pptps_state = PPTP_MTCTL_STOPREQ;
439 break;
440 case PPTP_MTCTL_STOPREP :
441 if (pptpo->pptps_state == PPTP_MTCTL_STOPREQ)
442 pptps->pptps_state = PPTP_MTCTL_STOPREP;
443 break;
444 case PPTP_MTCTL_ECHOREQ :
445 pptps->pptps_state = PPTP_MTCTL_ECHOREQ;
446 break;
447 case PPTP_MTCTL_ECHOREP :
448 if (pptpo->pptps_state == PPTP_MTCTL_ECHOREQ)
449 pptps->pptps_state = PPTP_MTCTL_ECHOREP;
450 break;
451 case PPTP_MTCTL_OUTREQ :
452 pptps->pptps_state = PPTP_MTCTL_OUTREQ;
453 break;
454 case PPTP_MTCTL_OUTREP :
455 if (pptpo->pptps_state == PPTP_MTCTL_OUTREQ) {
456 pptps->pptps_state = PPTP_MTCTL_OUTREP;
457 pptp->pptp_call[0] = buffer[7];
458 pptp->pptp_call[1] = buffer[6];
459 ipf_p_pptp_donatstate(fin, nat, pptp);
460 }
461 break;
462 case PPTP_MTCTL_INREQ :
463 pptps->pptps_state = PPTP_MTCTL_INREQ;
464 break;
465 case PPTP_MTCTL_INREP :
466 if (pptpo->pptps_state == PPTP_MTCTL_INREQ) {
467 pptps->pptps_state = PPTP_MTCTL_INREP;
468 pptp->pptp_call[0] = buffer[7];
469 pptp->pptp_call[1] = buffer[6];
470 ipf_p_pptp_donatstate(fin, nat, pptp);
471 }
472 break;
473 case PPTP_MTCTL_INCONNECT :
474 pptps->pptps_state = PPTP_MTCTL_INCONNECT;
475 break;
476 case PPTP_MTCTL_CLEAR :
477 pptps->pptps_state = PPTP_MTCTL_CLEAR;
478 break;
479 case PPTP_MTCTL_DISCONNECT :
480 pptps->pptps_state = PPTP_MTCTL_DISCONNECT;
481 break;
482 case PPTP_MTCTL_WANERROR :
483 pptps->pptps_state = PPTP_MTCTL_WANERROR;
484 break;
485 case PPTP_MTCTL_LINKINFO :
486 pptps->pptps_state = PPTP_MTCTL_LINKINFO;
487 break;
488 }
489
490 return (0);
491 }
492
493
494 /*
495 * For outgoing PPTP packets. refresh timeouts for NAT & state entries, if
496 * we can. If they have disappeared, recreate them.
497 */
498 int
ipf_p_pptp_inout(void * arg,fr_info_t * fin,ap_session_t * aps,nat_t * nat)499 ipf_p_pptp_inout(void *arg, fr_info_t *fin, ap_session_t *aps, nat_t *nat)
500 {
501 pptp_pxy_t *pptp;
502 tcphdr_t *tcp;
503 int rev;
504
505 if ((fin->fin_out == 1) && (nat->nat_dir == NAT_INBOUND))
506 rev = 1;
507 else if ((fin->fin_out == 0) && (nat->nat_dir == NAT_OUTBOUND))
508 rev = 1;
509 else
510 rev = 0;
511
512 tcp = (tcphdr_t *)fin->fin_dp;
513 if ((tcp_get_flags(tcp) & TH_OPENING) == TH_OPENING) {
514 pptp = (pptp_pxy_t *)aps->aps_data;
515 pptp->pptp_side[1 - rev].pptps_next = ntohl(tcp->th_ack);
516 pptp->pptp_side[1 - rev].pptps_nexthdr = ntohl(tcp->th_ack);
517 pptp->pptp_side[rev].pptps_next = ntohl(tcp->th_seq) + 1;
518 pptp->pptp_side[rev].pptps_nexthdr = ntohl(tcp->th_seq) + 1;
519 }
520 return (ipf_p_pptp_nextmessage(fin, nat, (pptp_pxy_t *)aps->aps_data,
521 rev));
522 }
523
524
525 /*
526 * clean up after ourselves.
527 */
528 void
ipf_p_pptp_del(ipf_main_softc_t * softc,ap_session_t * aps)529 ipf_p_pptp_del(ipf_main_softc_t *softc, ap_session_t *aps)
530 {
531 pptp_pxy_t *pptp;
532
533 pptp = aps->aps_data;
534
535 if (pptp != NULL) {
536 /*
537 * Don't bother changing any of the NAT structure details,
538 * *_del() is on a callback from aps_free(), from nat_delete()
539 */
540
541 READ_ENTER(&softc->ipf_state);
542 if (pptp->pptp_state != NULL) {
543 ipf_state_setpending(softc, pptp->pptp_state);
544 }
545 RWLOCK_EXIT(&softc->ipf_state);
546
547 if (pptp->pptp_nat != NULL)
548 ipf_nat_setpending(softc, pptp->pptp_nat);
549 pptp->pptp_rule->in_flags |= IPN_DELETE;
550 ipf_nat_rule_deref(softc, &pptp->pptp_rule);
551 }
552 }
553