ip_pptp_pxy.c revision 161351 
1/*
2 * Copyright (C) 2002-2003 by Darren Reed
3 *
4 * Simple PPTP transparent proxy for in-kernel use.  For use with the NAT
5 * code.
6 *
7 * $Id: ip_pptp_pxy.c,v 2.10.2.13 2006/03/17 10:40:05 darrenr Exp $
8 *
9 */
10#define	IPF_PPTP_PROXY
11
12typedef	struct pptp_hdr {
13	u_short	pptph_len;
14	u_short	pptph_type;
15	u_32_t	pptph_cookie;
16} pptp_hdr_t;
17
18#define	PPTP_MSGTYPE_CTL	1
19#define	PPTP_MTCTL_STARTREQ	1
20#define	PPTP_MTCTL_STARTREP	2
21#define	PPTP_MTCTL_STOPREQ	3
22#define	PPTP_MTCTL_STOPREP	4
23#define	PPTP_MTCTL_ECHOREQ	5
24#define	PPTP_MTCTL_ECHOREP	6
25#define	PPTP_MTCTL_OUTREQ	7
26#define	PPTP_MTCTL_OUTREP	8
27#define	PPTP_MTCTL_INREQ	9
28#define	PPTP_MTCTL_INREP	10
29#define	PPTP_MTCTL_INCONNECT	11
30#define	PPTP_MTCTL_CLEAR	12
31#define	PPTP_MTCTL_DISCONNECT	13
32#define	PPTP_MTCTL_WANERROR	14
33#define	PPTP_MTCTL_LINKINFO	15
34
35
36int ippr_pptp_init __P((void));
37void ippr_pptp_fini __P((void));
38int ippr_pptp_new __P((fr_info_t *, ap_session_t *, nat_t *));
39void ippr_pptp_del __P((ap_session_t *));
40int ippr_pptp_inout __P((fr_info_t *, ap_session_t *, nat_t *));
41void ippr_pptp_donatstate __P((fr_info_t *, nat_t *, pptp_pxy_t *));
42int ippr_pptp_message __P((fr_info_t *, nat_t *, pptp_pxy_t *, pptp_side_t *));
43int ippr_pptp_nextmessage __P((fr_info_t *, nat_t *, pptp_pxy_t *, int));
44int ippr_pptp_mctl __P((fr_info_t *, nat_t *, pptp_pxy_t *, pptp_side_t *));
45
46static	frentry_t	pptpfr;
47
48int	pptp_proxy_init = 0;
49int	ippr_pptp_debug = 0;
50int	ippr_pptp_gretimeout = IPF_TTLVAL(120);	/* 2 minutes */
51
52
53/*
54 * PPTP application proxy initialization.
55 */
56int ippr_pptp_init()
57{
58	bzero((char *)&pptpfr, sizeof(pptpfr));
59	pptpfr.fr_ref = 1;
60	pptpfr.fr_age[0] = ippr_pptp_gretimeout;
61	pptpfr.fr_age[1] = ippr_pptp_gretimeout;
62	pptpfr.fr_flags = FR_OUTQUE|FR_PASS|FR_QUICK|FR_KEEPSTATE;
63	MUTEX_INIT(&pptpfr.fr_lock, "PPTP proxy rule lock");
64	pptp_proxy_init = 1;
65
66	return 0;
67}
68
69
70void ippr_pptp_fini()
71{
72	if (pptp_proxy_init == 1) {
73		MUTEX_DESTROY(&pptpfr.fr_lock);
74		pptp_proxy_init = 0;
75	}
76}
77
78
79/*
80 * Setup for a new PPTP proxy.
81 */
82int ippr_pptp_new(fin, aps, nat)
83fr_info_t *fin;
84ap_session_t *aps;
85nat_t *nat;
86{
87	pptp_pxy_t *pptp;
88	ipnat_t *ipn;
89	ip_t *ip;
90
91	ip = fin->fin_ip;
92
93	if (nat_outlookup(fin, 0, IPPROTO_GRE, nat->nat_inip,
94			  ip->ip_dst) != NULL) {
95		if (ippr_pptp_debug > 0)
96			printf("ippr_pptp_new: GRE session %s\n",
97			       "already exists");
98		return -1;
99	}
100
101	aps->aps_psiz = sizeof(*pptp);
102	KMALLOCS(aps->aps_data, pptp_pxy_t *, sizeof(*pptp));
103	if (aps->aps_data == NULL) {
104		if (ippr_pptp_debug > 0)
105			printf("ippr_pptp_new: malloc for aps_data %s\n",
106			       "failed");
107		return -1;
108	}
109
110	/*
111	 * Create NAT rule against which the tunnel/transport mapping is
112	 * created.  This is required because the current NAT rule does not
113	 * describe GRE but TCP instead.
114	 */
115	pptp = aps->aps_data;
116	bzero((char *)pptp, sizeof(*pptp));
117	ipn = &pptp->pptp_rule;
118	ipn->in_ifps[0] = fin->fin_ifp;
119	ipn->in_apr = NULL;
120	ipn->in_use = 1;
121	ipn->in_hits = 1;
122	ipn->in_ippip = 1;
123	if (nat->nat_dir == NAT_OUTBOUND) {
124		ipn->in_nip = ntohl(nat->nat_outip.s_addr);
125		ipn->in_outip = fin->fin_saddr;
126		ipn->in_redir = NAT_MAP;
127	} else if (nat->nat_dir == NAT_INBOUND) {
128		ipn->in_nip = 0;
129		ipn->in_outip = nat->nat_outip.s_addr;
130		ipn->in_redir = NAT_REDIRECT;
131	}
132	ipn->in_inip = nat->nat_inip.s_addr;
133	ipn->in_inmsk = 0xffffffff;
134	ipn->in_outmsk = 0xffffffff;
135	ipn->in_srcip = fin->fin_saddr;
136	ipn->in_srcmsk = 0xffffffff;
137	bcopy(nat->nat_ptr->in_ifnames[0], ipn->in_ifnames[0],
138	      sizeof(ipn->in_ifnames[0]));
139	ipn->in_p = IPPROTO_GRE;
140
141	pptp->pptp_side[0].pptps_wptr = pptp->pptp_side[0].pptps_buffer;
142	pptp->pptp_side[1].pptps_wptr = pptp->pptp_side[1].pptps_buffer;
143	return 0;
144}
145
146
147void ippr_pptp_donatstate(fin, nat, pptp)
148fr_info_t *fin;
149nat_t *nat;
150pptp_pxy_t *pptp;
151{
152	fr_info_t fi;
153	grehdr_t gre;
154	nat_t *nat2;
155	u_char p;
156	ip_t *ip;
157
158	ip = fin->fin_ip;
159	p = ip->ip_p;
160
161	nat2 = pptp->pptp_nat;
162	if ((nat2 == NULL) || (pptp->pptp_state == NULL)) {
163		bcopy((char *)fin, (char *)&fi, sizeof(fi));
164		bzero((char *)&gre, sizeof(gre));
165		fi.fin_state = NULL;
166		fi.fin_nat = NULL;
167		fi.fin_fi.fi_p = IPPROTO_GRE;
168		fi.fin_fr = &pptpfr;
169		if ((nat->nat_dir == NAT_OUTBOUND && fin->fin_out) ||
170		    (nat->nat_dir == NAT_INBOUND && !fin->fin_out)) {
171			fi.fin_data[0] = pptp->pptp_call[0];
172			fi.fin_data[1] = pptp->pptp_call[1];
173		} else {
174			fi.fin_data[0] = pptp->pptp_call[1];
175			fi.fin_data[1] = pptp->pptp_call[0];
176		}
177		ip = fin->fin_ip;
178		ip->ip_p = IPPROTO_GRE;
179		fi.fin_flx &= ~(FI_TCPUDP|FI_STATE|FI_FRAG);
180		fi.fin_flx |= FI_IGNORE;
181		fi.fin_dp = &gre;
182		gre.gr_flags = htons(1 << 13);
183		if (fin->fin_out && nat->nat_dir == NAT_INBOUND) {
184			fi.fin_fi.fi_saddr = fin->fin_fi.fi_daddr;
185			fi.fin_fi.fi_daddr = nat->nat_outip.s_addr;
186		} else if (!fin->fin_out && nat->nat_dir == NAT_OUTBOUND) {
187			fi.fin_fi.fi_saddr = nat->nat_inip.s_addr;
188			fi.fin_fi.fi_daddr = fin->fin_fi.fi_saddr;
189		}
190	}
191
192	/*
193	 * Update NAT timeout/create NAT if missing.
194	 */
195	if (nat2 != NULL)
196		fr_queueback(&nat2->nat_tqe);
197	else {
198		nat2 = nat_new(&fi, &pptp->pptp_rule, &pptp->pptp_nat,
199			       NAT_SLAVE, nat->nat_dir);
200		pptp->pptp_nat = nat2;
201		if (nat2 != NULL) {
202			(void) nat_proto(&fi, nat2, 0);
203			nat_update(&fi, nat2, nat2->nat_ptr);
204		}
205	}
206
207	READ_ENTER(&ipf_state);
208	if (pptp->pptp_state != NULL) {
209		fr_queueback(&pptp->pptp_state->is_sti);
210		RWLOCK_EXIT(&ipf_state);
211	} else {
212		RWLOCK_EXIT(&ipf_state);
213		if (nat2 != NULL) {
214			if (nat->nat_dir == NAT_INBOUND)
215				fi.fin_fi.fi_daddr = nat2->nat_inip.s_addr;
216			else
217				fi.fin_fi.fi_saddr = nat2->nat_inip.s_addr;
218		}
219		fi.fin_ifp = NULL;
220		pptp->pptp_state = fr_addstate(&fi, &pptp->pptp_state,
221					       0);
222		if (fi.fin_state != NULL)
223			fr_statederef(&fi, (ipstate_t **)&fi.fin_state);
224	}
225	ip->ip_p = p;
226	return;
227}
228
229
230/*
231 * Try and build up the next PPTP message in the TCP stream and if we can
232 * build it up completely (fits in our buffer) then pass it off to the message
233 * parsing function.
234 */
235int ippr_pptp_nextmessage(fin, nat, pptp, rev)
236fr_info_t *fin;
237nat_t *nat;
238pptp_pxy_t *pptp;
239int rev;
240{
241	static const char *funcname = "ippr_pptp_nextmessage";
242	pptp_side_t *pptps;
243	u_32_t start, end;
244	pptp_hdr_t *hdr;
245	tcphdr_t *tcp;
246	int dlen, off;
247	u_short len;
248	char *msg;
249
250	tcp = fin->fin_dp;
251	dlen = fin->fin_dlen - (TCP_OFF(tcp) << 2);
252	start = ntohl(tcp->th_seq);
253	pptps = &pptp->pptp_side[rev];
254	off = (char *)tcp - (char *)fin->fin_ip + (TCP_OFF(tcp) << 2) +
255	      fin->fin_ipoff;
256
257	if (dlen <= 0)
258		return 0;
259	/*
260	 * If the complete data packet is before what we expect to see
261	 * "next", just ignore it as the chances are we've already seen it.
262	 * The next if statement following this one really just causes packets
263	 * ahead of what we've seen to be dropped, implying that something in
264	 * the middle went missing and we want to see that first.
265	 */
266	end = start + dlen;
267	if (pptps->pptps_next > end && pptps->pptps_next > start)
268		return 0;
269
270	if (pptps->pptps_next != start) {
271		if (ippr_pptp_debug > 5)
272			printf("%s: next (%x) != start (%x)\n", funcname,
273				pptps->pptps_next, start);
274		return -1;
275	}
276
277	msg = (char *)fin->fin_dp + (TCP_OFF(tcp) << 2);
278
279	while (dlen > 0) {
280		off += pptps->pptps_bytes;
281		if (pptps->pptps_gothdr == 0) {
282			/*
283			 * PPTP has an 8 byte header that inclues the cookie.
284			 * The start of every message should include one and
285			 * it should match 1a2b3c4d.  Byte order is ignored,
286			 * deliberately, when printing out the error.
287			 */
288			len = MIN(8 - pptps->pptps_bytes, dlen);
289			COPYDATA(fin->fin_m, off, len, pptps->pptps_wptr);
290			pptps->pptps_bytes += len;
291			pptps->pptps_wptr += len;
292			hdr = (pptp_hdr_t *)pptps->pptps_buffer;
293			if (pptps->pptps_bytes == 8) {
294				pptps->pptps_next += 8;
295				if (ntohl(hdr->pptph_cookie) != 0x1a2b3c4d) {
296					if (ippr_pptp_debug > 1)
297						printf("%s: bad cookie (%x)\n",
298						       funcname,
299						       hdr->pptph_cookie);
300					return -1;
301				}
302			}
303			dlen -= len;
304			msg += len;
305			off += len;
306
307			pptps->pptps_gothdr = 1;
308			len = ntohs(hdr->pptph_len);
309			pptps->pptps_len = len;
310			pptps->pptps_nexthdr += len;
311
312			/*
313			 * If a message is too big for the buffer, just set
314			 * the fields for the next message to come along.
315			 * The messages defined in RFC 2637 will not exceed
316			 * 512 bytes (in total length) so this is likely a
317			 * bad data packet, anyway.
318			 */
319			if (len > sizeof(pptps->pptps_buffer)) {
320				if (ippr_pptp_debug > 3)
321					printf("%s: message too big (%d)\n",
322					       funcname, len);
323				pptps->pptps_next = pptps->pptps_nexthdr;
324				pptps->pptps_wptr = pptps->pptps_buffer;
325				pptps->pptps_gothdr = 0;
326				pptps->pptps_bytes = 0;
327				pptps->pptps_len = 0;
328				break;
329			}
330		}
331
332		len = MIN(pptps->pptps_len - pptps->pptps_bytes, dlen);
333		COPYDATA(fin->fin_m, off, len, pptps->pptps_wptr);
334		pptps->pptps_bytes += len;
335		pptps->pptps_wptr += len;
336		pptps->pptps_next += len;
337
338		if (pptps->pptps_len > pptps->pptps_bytes)
339			break;
340
341		ippr_pptp_message(fin, nat, pptp, pptps);
342		pptps->pptps_wptr = pptps->pptps_buffer;
343		pptps->pptps_gothdr = 0;
344		pptps->pptps_bytes = 0;
345		pptps->pptps_len = 0;
346
347		start += len;
348		msg += len;
349		dlen -= len;
350	}
351
352	return 0;
353}
354
355
356/*
357 * handle a complete PPTP message
358 */
359int ippr_pptp_message(fin, nat, pptp, pptps)
360fr_info_t *fin;
361nat_t *nat;
362pptp_pxy_t *pptp;
363pptp_side_t *pptps;
364{
365	pptp_hdr_t *hdr = (pptp_hdr_t *)pptps->pptps_buffer;
366
367	switch (ntohs(hdr->pptph_type))
368	{
369	case PPTP_MSGTYPE_CTL :
370		ippr_pptp_mctl(fin, nat, pptp, pptps);
371		break;
372
373	default :
374		break;
375	}
376	return 0;
377}
378
379
380/*
381 * handle a complete PPTP control message
382 */
383int ippr_pptp_mctl(fin, nat, pptp, pptps)
384fr_info_t *fin;
385nat_t *nat;
386pptp_pxy_t *pptp;
387pptp_side_t *pptps;
388{
389	u_short *buffer = (u_short *)(pptps->pptps_buffer);
390	pptp_side_t *pptpo;
391
392	if (pptps == &pptp->pptp_side[0])
393		pptpo = &pptp->pptp_side[1];
394	else
395		pptpo = &pptp->pptp_side[0];
396
397	/*
398	 * Breakout to handle all the various messages.  Most are just state
399	 * transition.
400	 */
401	switch (ntohs(buffer[4]))
402	{
403	case PPTP_MTCTL_STARTREQ :
404		pptps->pptps_state = PPTP_MTCTL_STARTREQ;
405		break;
406	case PPTP_MTCTL_STARTREP :
407		if (pptpo->pptps_state == PPTP_MTCTL_STARTREQ)
408			pptps->pptps_state = PPTP_MTCTL_STARTREP;
409		break;
410	case PPTP_MTCTL_STOPREQ :
411		pptps->pptps_state = PPTP_MTCTL_STOPREQ;
412		break;
413	case PPTP_MTCTL_STOPREP :
414		if (pptpo->pptps_state == PPTP_MTCTL_STOPREQ)
415			pptps->pptps_state = PPTP_MTCTL_STOPREP;
416		break;
417	case PPTP_MTCTL_ECHOREQ :
418		pptps->pptps_state = PPTP_MTCTL_ECHOREQ;
419		break;
420	case PPTP_MTCTL_ECHOREP :
421		if (pptpo->pptps_state == PPTP_MTCTL_ECHOREQ)
422			pptps->pptps_state = PPTP_MTCTL_ECHOREP;
423		break;
424	case PPTP_MTCTL_OUTREQ :
425		pptps->pptps_state = PPTP_MTCTL_OUTREQ;
426		break;
427	case PPTP_MTCTL_OUTREP :
428		if (pptpo->pptps_state == PPTP_MTCTL_OUTREQ) {
429			pptps->pptps_state = PPTP_MTCTL_OUTREP;
430			pptp->pptp_call[0] = buffer[7];
431			pptp->pptp_call[1] = buffer[6];
432			ippr_pptp_donatstate(fin, nat, pptp);
433		}
434		break;
435	case PPTP_MTCTL_INREQ :
436		pptps->pptps_state = PPTP_MTCTL_INREQ;
437		break;
438	case PPTP_MTCTL_INREP :
439		if (pptpo->pptps_state == PPTP_MTCTL_INREQ) {
440			pptps->pptps_state = PPTP_MTCTL_INREP;
441			pptp->pptp_call[0] = buffer[7];
442			pptp->pptp_call[1] = buffer[6];
443			ippr_pptp_donatstate(fin, nat, pptp);
444		}
445		break;
446	case PPTP_MTCTL_INCONNECT :
447		pptps->pptps_state = PPTP_MTCTL_INCONNECT;
448		break;
449	case PPTP_MTCTL_CLEAR :
450		pptps->pptps_state = PPTP_MTCTL_CLEAR;
451		break;
452	case PPTP_MTCTL_DISCONNECT :
453		pptps->pptps_state = PPTP_MTCTL_DISCONNECT;
454		break;
455	case PPTP_MTCTL_WANERROR :
456		pptps->pptps_state = PPTP_MTCTL_WANERROR;
457		break;
458	case PPTP_MTCTL_LINKINFO :
459		pptps->pptps_state = PPTP_MTCTL_LINKINFO;
460		break;
461	}
462
463	return 0;
464}
465
466
467/*
468 * For outgoing PPTP packets.  refresh timeouts for NAT & state entries, if
469 * we can.  If they have disappeared, recreate them.
470 */
471int ippr_pptp_inout(fin, aps, nat)
472fr_info_t *fin;
473ap_session_t *aps;
474nat_t *nat;
475{
476	pptp_pxy_t *pptp;
477	tcphdr_t *tcp;
478	int rev;
479
480	if ((fin->fin_out == 1) && (nat->nat_dir == NAT_INBOUND))
481		rev = 1;
482	else if ((fin->fin_out == 0) && (nat->nat_dir == NAT_OUTBOUND))
483		rev = 1;
484	else
485		rev = 0;
486
487	tcp = (tcphdr_t *)fin->fin_dp;
488	if ((tcp->th_flags & TH_OPENING) == TH_OPENING) {
489		pptp = (pptp_pxy_t *)aps->aps_data;
490		pptp->pptp_side[1 - rev].pptps_next = ntohl(tcp->th_ack);
491		pptp->pptp_side[1 - rev].pptps_nexthdr = ntohl(tcp->th_ack);
492		pptp->pptp_side[rev].pptps_next = ntohl(tcp->th_seq) + 1;
493		pptp->pptp_side[rev].pptps_nexthdr = ntohl(tcp->th_seq) + 1;
494	}
495	return ippr_pptp_nextmessage(fin, nat, (pptp_pxy_t *)aps->aps_data,
496				     rev);
497}
498
499
500/*
501 * clean up after ourselves.
502 */
503void ippr_pptp_del(aps)
504ap_session_t *aps;
505{
506	pptp_pxy_t *pptp;
507
508	pptp = aps->aps_data;
509
510	if (pptp != NULL) {
511		/*
512		 * Don't bother changing any of the NAT structure details,
513		 * *_del() is on a callback from aps_free(), from nat_delete()
514		 */
515
516		READ_ENTER(&ipf_state);
517		if (pptp->pptp_state != NULL) {
518			pptp->pptp_state->is_die = fr_ticks + 1;
519			pptp->pptp_state->is_me = NULL;
520			fr_queuefront(&pptp->pptp_state->is_sti);
521		}
522		RWLOCK_EXIT(&ipf_state);
523
524		pptp->pptp_state = NULL;
525		pptp->pptp_nat = NULL;
526	}
527}
528