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23#include <linux/module.h>
24#include <linux/skbuff.h>
25#include <linux/in.h>
26#include <linux/tcp.h>
27
28#include <net/netfilter/nf_conntrack.h>
29#include <net/netfilter/nf_conntrack_core.h>
30#include <net/netfilter/nf_conntrack_helper.h>
31#include <linux/netfilter/nf_conntrack_proto_gre.h>
32#include <linux/netfilter/nf_conntrack_pptp.h>
33
34#define NF_CT_PPTP_VERSION "3.1"
35
36MODULE_LICENSE("GPL");
37MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
38MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
39MODULE_ALIAS("ip_conntrack_pptp");
40
41static DEFINE_SPINLOCK(nf_pptp_lock);
42
43int
44(*nf_nat_pptp_hook_outbound)(struct sk_buff *skb,
45 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
46 struct PptpControlHeader *ctlh,
47 union pptp_ctrl_union *pptpReq) __read_mostly;
48EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound);
49
50int
51(*nf_nat_pptp_hook_inbound)(struct sk_buff *skb,
52 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
53 struct PptpControlHeader *ctlh,
54 union pptp_ctrl_union *pptpReq) __read_mostly;
55EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound);
56
57void
58(*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig,
59 struct nf_conntrack_expect *expect_reply)
60 __read_mostly;
61EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre);
62
63void
64(*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct,
65 struct nf_conntrack_expect *exp) __read_mostly;
66EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
67
68#ifdef DEBUG
69
70const char *pptp_msg_name[] = {
71 "UNKNOWN_MESSAGE",
72 "START_SESSION_REQUEST",
73 "START_SESSION_REPLY",
74 "STOP_SESSION_REQUEST",
75 "STOP_SESSION_REPLY",
76 "ECHO_REQUEST",
77 "ECHO_REPLY",
78 "OUT_CALL_REQUEST",
79 "OUT_CALL_REPLY",
80 "IN_CALL_REQUEST",
81 "IN_CALL_REPLY",
82 "IN_CALL_CONNECT",
83 "CALL_CLEAR_REQUEST",
84 "CALL_DISCONNECT_NOTIFY",
85 "WAN_ERROR_NOTIFY",
86 "SET_LINK_INFO"
87};
88EXPORT_SYMBOL(pptp_msg_name);
89#endif
90
91#define SECS *HZ
92#define MINS * 60 SECS
93#define HOURS * 60 MINS
94
95#define PPTP_GRE_TIMEOUT (10 MINS)
96#define PPTP_GRE_STREAM_TIMEOUT (5 HOURS)
97
98static void pptp_expectfn(struct nf_conn *ct,
99 struct nf_conntrack_expect *exp)
100{
101 typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn;
102 pr_debug("increasing timeouts\n");
103
104
105 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT;
106 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
107
108
109
110
111 rcu_read_lock();
112 nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn);
113 if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK)
114 nf_nat_pptp_expectfn(ct, exp);
115 else {
116 struct nf_conntrack_tuple inv_t;
117 struct nf_conntrack_expect *exp_other;
118
119
120 nf_ct_invert_tuplepr(&inv_t, &exp->tuple);
121 pr_debug("trying to unexpect other dir: ");
122 NF_CT_DUMP_TUPLE(&inv_t);
123
124 exp_other = nf_ct_expect_find_get(&inv_t);
125 if (exp_other) {
126
127 pr_debug("found\n");
128 nf_ct_unexpect_related(exp_other);
129 nf_ct_expect_put(exp_other);
130 } else {
131 pr_debug("not found\n");
132 }
133 }
134 rcu_read_unlock();
135}
136
137static int destroy_sibling_or_exp(const struct nf_conntrack_tuple *t)
138{
139 struct nf_conntrack_tuple_hash *h;
140 struct nf_conntrack_expect *exp;
141 struct nf_conn *sibling;
142
143 pr_debug("trying to timeout ct or exp for tuple ");
144 NF_CT_DUMP_TUPLE(t);
145
146 h = nf_conntrack_find_get(t);
147 if (h) {
148 sibling = nf_ct_tuplehash_to_ctrack(h);
149 pr_debug("setting timeout of conntrack %p to 0\n", sibling);
150 sibling->proto.gre.timeout = 0;
151 sibling->proto.gre.stream_timeout = 0;
152 if (del_timer(&sibling->timeout))
153 sibling->timeout.function((unsigned long)sibling);
154 nf_ct_put(sibling);
155 return 1;
156 } else {
157 exp = nf_ct_expect_find_get(t);
158 if (exp) {
159 pr_debug("unexpect_related of expect %p\n", exp);
160 nf_ct_unexpect_related(exp);
161 nf_ct_expect_put(exp);
162 return 1;
163 }
164 }
165 return 0;
166}
167
168
169static void pptp_destroy_siblings(struct nf_conn *ct)
170{
171 struct nf_conn_help *help = nfct_help(ct);
172 struct nf_conntrack_tuple t;
173
174 nf_ct_gre_keymap_destroy(ct);
175
176
177 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
178 t.dst.protonum = IPPROTO_GRE;
179 t.src.u.gre.key = help->help.ct_pptp_info.pns_call_id;
180 t.dst.u.gre.key = help->help.ct_pptp_info.pac_call_id;
181 if (!destroy_sibling_or_exp(&t))
182 pr_debug("failed to timeout original pns->pac ct/exp\n");
183
184
185 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
186 t.dst.protonum = IPPROTO_GRE;
187 t.src.u.gre.key = help->help.ct_pptp_info.pac_call_id;
188 t.dst.u.gre.key = help->help.ct_pptp_info.pns_call_id;
189 if (!destroy_sibling_or_exp(&t))
190 pr_debug("failed to timeout reply pac->pns ct/exp\n");
191}
192
193
194static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
195{
196 struct nf_conntrack_expect *exp_orig, *exp_reply;
197 enum ip_conntrack_dir dir;
198 int ret = 1;
199 typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre;
200
201 exp_orig = nf_ct_expect_alloc(ct);
202 if (exp_orig == NULL)
203 goto out;
204
205 exp_reply = nf_ct_expect_alloc(ct);
206 if (exp_reply == NULL)
207 goto out_put_orig;
208
209
210 dir = IP_CT_DIR_ORIGINAL;
211 nf_ct_expect_init(exp_orig, ct->tuplehash[dir].tuple.src.l3num,
212 &ct->tuplehash[dir].tuple.src.u3,
213 &ct->tuplehash[dir].tuple.dst.u3,
214 IPPROTO_GRE, &peer_callid, &callid);
215 exp_orig->expectfn = pptp_expectfn;
216
217
218 dir = IP_CT_DIR_REPLY;
219 nf_ct_expect_init(exp_reply, ct->tuplehash[dir].tuple.src.l3num,
220 &ct->tuplehash[dir].tuple.src.u3,
221 &ct->tuplehash[dir].tuple.dst.u3,
222 IPPROTO_GRE, &callid, &peer_callid);
223 exp_reply->expectfn = pptp_expectfn;
224
225 nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre);
226 if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK)
227 nf_nat_pptp_exp_gre(exp_orig, exp_reply);
228 if (nf_ct_expect_related(exp_orig) != 0)
229 goto out_put_both;
230 if (nf_ct_expect_related(exp_reply) != 0)
231 goto out_unexpect_orig;
232
233
234 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
235 goto out_unexpect_both;
236 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
237 nf_ct_gre_keymap_destroy(ct);
238 goto out_unexpect_both;
239 }
240 ret = 0;
241
242out_put_both:
243 nf_ct_expect_put(exp_reply);
244out_put_orig:
245 nf_ct_expect_put(exp_orig);
246out:
247 return ret;
248
249out_unexpect_both:
250 nf_ct_unexpect_related(exp_reply);
251out_unexpect_orig:
252 nf_ct_unexpect_related(exp_orig);
253 goto out_put_both;
254}
255
256static inline int
257pptp_inbound_pkt(struct sk_buff *skb,
258 struct PptpControlHeader *ctlh,
259 union pptp_ctrl_union *pptpReq,
260 unsigned int reqlen,
261 struct nf_conn *ct,
262 enum ip_conntrack_info ctinfo)
263{
264 struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
265 u_int16_t msg;
266 __be16 cid = 0, pcid = 0;
267 typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
268
269 msg = ntohs(ctlh->messageType);
270 pr_debug("inbound control message %s\n", pptp_msg_name[msg]);
271
272 switch (msg) {
273 case PPTP_START_SESSION_REPLY:
274
275 if (info->sstate < PPTP_SESSION_REQUESTED)
276 goto invalid;
277 if (pptpReq->srep.resultCode == PPTP_START_OK)
278 info->sstate = PPTP_SESSION_CONFIRMED;
279 else
280 info->sstate = PPTP_SESSION_ERROR;
281 break;
282
283 case PPTP_STOP_SESSION_REPLY:
284
285 if (info->sstate > PPTP_SESSION_STOPREQ)
286 goto invalid;
287 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
288 info->sstate = PPTP_SESSION_NONE;
289 else
290 info->sstate = PPTP_SESSION_ERROR;
291 break;
292
293 case PPTP_OUT_CALL_REPLY:
294
295 if (info->sstate != PPTP_SESSION_CONFIRMED)
296 goto invalid;
297 if (info->cstate != PPTP_CALL_OUT_REQ &&
298 info->cstate != PPTP_CALL_OUT_CONF)
299 goto invalid;
300
301 cid = pptpReq->ocack.callID;
302 pcid = pptpReq->ocack.peersCallID;
303 if (info->pns_call_id != pcid)
304 goto invalid;
305 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
306 ntohs(cid), ntohs(pcid));
307
308 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
309 info->cstate = PPTP_CALL_OUT_CONF;
310 info->pac_call_id = cid;
311 exp_gre(ct, cid, pcid);
312 } else
313 info->cstate = PPTP_CALL_NONE;
314 break;
315
316 case PPTP_IN_CALL_REQUEST:
317
318 if (info->sstate != PPTP_SESSION_CONFIRMED)
319 goto invalid;
320
321 cid = pptpReq->icreq.callID;
322 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
323 info->cstate = PPTP_CALL_IN_REQ;
324 info->pac_call_id = cid;
325 break;
326
327 case PPTP_IN_CALL_CONNECT:
328
329 if (info->sstate != PPTP_SESSION_CONFIRMED)
330 goto invalid;
331 if (info->cstate != PPTP_CALL_IN_REP &&
332 info->cstate != PPTP_CALL_IN_CONF)
333 goto invalid;
334
335 pcid = pptpReq->iccon.peersCallID;
336 cid = info->pac_call_id;
337
338 if (info->pns_call_id != pcid)
339 goto invalid;
340
341 pr_debug("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid));
342 info->cstate = PPTP_CALL_IN_CONF;
343
344
345 exp_gre(ct, cid, pcid);
346 break;
347
348 case PPTP_CALL_DISCONNECT_NOTIFY:
349
350 cid = pptpReq->disc.callID;
351 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
352 info->cstate = PPTP_CALL_NONE;
353
354
355 pptp_destroy_siblings(ct);
356 break;
357
358 case PPTP_WAN_ERROR_NOTIFY:
359 case PPTP_ECHO_REQUEST:
360 case PPTP_ECHO_REPLY:
361
362 break;
363
364 default:
365 goto invalid;
366 }
367
368 nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound);
369 if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK)
370 return nf_nat_pptp_inbound(skb, ct, ctinfo, ctlh, pptpReq);
371 return NF_ACCEPT;
372
373invalid:
374 pr_debug("invalid %s: type=%d cid=%u pcid=%u "
375 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
376 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
377 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate,
378 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
379 return NF_ACCEPT;
380}
381
382static inline int
383pptp_outbound_pkt(struct sk_buff *skb,
384 struct PptpControlHeader *ctlh,
385 union pptp_ctrl_union *pptpReq,
386 unsigned int reqlen,
387 struct nf_conn *ct,
388 enum ip_conntrack_info ctinfo)
389{
390 struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
391 u_int16_t msg;
392 __be16 cid = 0, pcid = 0;
393 typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
394
395 msg = ntohs(ctlh->messageType);
396 pr_debug("outbound control message %s\n", pptp_msg_name[msg]);
397
398 switch (msg) {
399 case PPTP_START_SESSION_REQUEST:
400
401 if (info->sstate != PPTP_SESSION_NONE)
402 goto invalid;
403 info->sstate = PPTP_SESSION_REQUESTED;
404 break;
405
406 case PPTP_STOP_SESSION_REQUEST:
407
408 info->sstate = PPTP_SESSION_STOPREQ;
409 break;
410
411 case PPTP_OUT_CALL_REQUEST:
412
413 if (info->sstate != PPTP_SESSION_CONFIRMED)
414 goto invalid;
415 info->cstate = PPTP_CALL_OUT_REQ;
416
417 cid = pptpReq->ocreq.callID;
418 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
419 info->pns_call_id = cid;
420 break;
421
422 case PPTP_IN_CALL_REPLY:
423
424 if (info->cstate != PPTP_CALL_IN_REQ &&
425 info->cstate != PPTP_CALL_IN_REP)
426 goto invalid;
427
428 cid = pptpReq->icack.callID;
429 pcid = pptpReq->icack.peersCallID;
430 if (info->pac_call_id != pcid)
431 goto invalid;
432 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg],
433 ntohs(cid), ntohs(pcid));
434
435 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
436
437 info->cstate = PPTP_CALL_IN_REP;
438 info->pns_call_id = cid;
439 } else
440 info->cstate = PPTP_CALL_NONE;
441 break;
442
443 case PPTP_CALL_CLEAR_REQUEST:
444
445 if (info->sstate != PPTP_SESSION_CONFIRMED)
446 goto invalid;
447
448
449
450 info->cstate = PPTP_CALL_CLEAR_REQ;
451 break;
452
453 case PPTP_SET_LINK_INFO:
454 case PPTP_ECHO_REQUEST:
455 case PPTP_ECHO_REPLY:
456
457 break;
458
459 default:
460 goto invalid;
461 }
462
463 nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound);
464 if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK)
465 return nf_nat_pptp_outbound(skb, ct, ctinfo, ctlh, pptpReq);
466 return NF_ACCEPT;
467
468invalid:
469 pr_debug("invalid %s: type=%d cid=%u pcid=%u "
470 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
471 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
472 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate,
473 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
474 return NF_ACCEPT;
475}
476
477static const unsigned int pptp_msg_size[] = {
478 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest),
479 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply),
480 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest),
481 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply),
482 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest),
483 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply),
484 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest),
485 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply),
486 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected),
487 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest),
488 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
489 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify),
490 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo),
491};
492
493
494static int
495conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
496 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
497
498{
499 int dir = CTINFO2DIR(ctinfo);
500 struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
501 struct tcphdr _tcph, *tcph;
502 struct pptp_pkt_hdr _pptph, *pptph;
503 struct PptpControlHeader _ctlh, *ctlh;
504 union pptp_ctrl_union _pptpReq, *pptpReq;
505 unsigned int tcplen = skb->len - protoff;
506 unsigned int datalen, reqlen, nexthdr_off;
507 int oldsstate, oldcstate;
508 int ret;
509 u_int16_t msg;
510
511
512 if (ctinfo != IP_CT_ESTABLISHED &&
513 ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY)
514 return NF_ACCEPT;
515
516 nexthdr_off = protoff;
517 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
518 BUG_ON(!tcph);
519 nexthdr_off += tcph->doff * 4;
520 datalen = tcplen - tcph->doff * 4;
521
522 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
523 if (!pptph) {
524 pr_debug("no full PPTP header, can't track\n");
525 return NF_ACCEPT;
526 }
527 nexthdr_off += sizeof(_pptph);
528 datalen -= sizeof(_pptph);
529
530
531 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
532 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
533 pr_debug("not a control packet\n");
534 return NF_ACCEPT;
535 }
536
537 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
538 if (!ctlh)
539 return NF_ACCEPT;
540 nexthdr_off += sizeof(_ctlh);
541 datalen -= sizeof(_ctlh);
542
543 reqlen = datalen;
544 msg = ntohs(ctlh->messageType);
545 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
546 return NF_ACCEPT;
547 if (reqlen > sizeof(*pptpReq))
548 reqlen = sizeof(*pptpReq);
549
550 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
551 if (!pptpReq)
552 return NF_ACCEPT;
553
554 oldsstate = info->sstate;
555 oldcstate = info->cstate;
556
557 spin_lock_bh(&nf_pptp_lock);
558
559
560
561 if (dir == IP_CT_DIR_ORIGINAL)
562
563 ret = pptp_outbound_pkt(skb, ctlh, pptpReq, reqlen, ct,
564 ctinfo);
565 else
566
567 ret = pptp_inbound_pkt(skb, ctlh, pptpReq, reqlen, ct,
568 ctinfo);
569 pr_debug("sstate: %d->%d, cstate: %d->%d\n",
570 oldsstate, info->sstate, oldcstate, info->cstate);
571 spin_unlock_bh(&nf_pptp_lock);
572
573 return ret;
574}
575
576
577static struct nf_conntrack_helper pptp __read_mostly = {
578 .name = "pptp",
579 .me = THIS_MODULE,
580 .max_expected = 2,
581 .timeout = 5 * 60,
582 .tuple.src.l3num = AF_INET,
583 .tuple.src.u.tcp.port = __constant_htons(PPTP_CONTROL_PORT),
584 .tuple.dst.protonum = IPPROTO_TCP,
585 .help = conntrack_pptp_help,
586 .destroy = pptp_destroy_siblings,
587};
588
589static int __init nf_conntrack_pptp_init(void)
590{
591 return nf_conntrack_helper_register(&pptp);
592}
593
594static void __exit nf_conntrack_pptp_fini(void)
595{
596 nf_conntrack_helper_unregister(&pptp);
597 nf_ct_gre_keymap_flush();
598}
599
600module_init(nf_conntrack_pptp_init);
601module_exit(nf_conntrack_pptp_fini);
602
