1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Connection tracking support for PPTP (Point to Point Tunneling Protocol).
4 * PPTP is a protocol for creating virtual private networks.
5 * It is a specification defined by Microsoft and some vendors
6 * working with Microsoft. PPTP is built on top of a modified
7 * version of the Internet Generic Routing Encapsulation Protocol.
8 * GRE is defined in RFC 1701 and RFC 1702. Documentation of
9 * PPTP can be found in RFC 2637
10 *
11 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
12 *
13 * Development of this code funded by Astaro AG (http://www.astaro.com/)
14 *
15 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
16 *
17 * Limitations:
18 * - We blindly assume that control connections are always
19 * established in PNS->PAC direction. This is a violation
20 * of RFC 2637
21 * - We can only support one single call within each session
22 * TODO:
23 * - testing of incoming PPTP calls
24 */
25
26 #include <linux/module.h>
27 #include <linux/skbuff.h>
28 #include <linux/in.h>
29 #include <linux/tcp.h>
30
31 #include <net/netfilter/nf_conntrack.h>
32 #include <net/netfilter/nf_conntrack_core.h>
33 #include <net/netfilter/nf_conntrack_helper.h>
34 #include <net/netfilter/nf_conntrack_zones.h>
35 #include <linux/netfilter/nf_conntrack_proto_gre.h>
36 #include <linux/netfilter/nf_conntrack_pptp.h>
37
38 #define NF_CT_PPTP_VERSION "3.1"
39
40 MODULE_LICENSE("GPL");
41 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
42 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
43 MODULE_ALIAS("ip_conntrack_pptp");
44 MODULE_ALIAS_NFCT_HELPER("pptp");
45
46 static DEFINE_SPINLOCK(nf_pptp_lock);
47
48 const struct nf_nat_pptp_hook __rcu *nf_nat_pptp_hook;
49 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook);
50
51 #if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
52 /* PptpControlMessageType names */
53 static const char *const pptp_msg_name_array[PPTP_MSG_MAX + 1] = {
54 [0] = "UNKNOWN_MESSAGE",
55 [PPTP_START_SESSION_REQUEST] = "START_SESSION_REQUEST",
56 [PPTP_START_SESSION_REPLY] = "START_SESSION_REPLY",
57 [PPTP_STOP_SESSION_REQUEST] = "STOP_SESSION_REQUEST",
58 [PPTP_STOP_SESSION_REPLY] = "STOP_SESSION_REPLY",
59 [PPTP_ECHO_REQUEST] = "ECHO_REQUEST",
60 [PPTP_ECHO_REPLY] = "ECHO_REPLY",
61 [PPTP_OUT_CALL_REQUEST] = "OUT_CALL_REQUEST",
62 [PPTP_OUT_CALL_REPLY] = "OUT_CALL_REPLY",
63 [PPTP_IN_CALL_REQUEST] = "IN_CALL_REQUEST",
64 [PPTP_IN_CALL_REPLY] = "IN_CALL_REPLY",
65 [PPTP_IN_CALL_CONNECT] = "IN_CALL_CONNECT",
66 [PPTP_CALL_CLEAR_REQUEST] = "CALL_CLEAR_REQUEST",
67 [PPTP_CALL_DISCONNECT_NOTIFY] = "CALL_DISCONNECT_NOTIFY",
68 [PPTP_WAN_ERROR_NOTIFY] = "WAN_ERROR_NOTIFY",
69 [PPTP_SET_LINK_INFO] = "SET_LINK_INFO"
70 };
71
pptp_msg_name(u_int16_t msg)72 const char *pptp_msg_name(u_int16_t msg)
73 {
74 if (msg > PPTP_MSG_MAX)
75 return pptp_msg_name_array[0];
76
77 return pptp_msg_name_array[msg];
78 }
79 EXPORT_SYMBOL(pptp_msg_name);
80 #endif
81
82 #define SECS *HZ
83 #define MINS * 60 SECS
84 #define HOURS * 60 MINS
85
86 #define PPTP_GRE_TIMEOUT (10 MINS)
87 #define PPTP_GRE_STREAM_TIMEOUT (5 HOURS)
88
pptp_expectfn(struct nf_conn * ct,struct nf_conntrack_expect * exp)89 static void pptp_expectfn(struct nf_conn *ct,
90 struct nf_conntrack_expect *exp)
91 {
92 const struct nf_nat_pptp_hook *hook;
93 struct net *net = nf_ct_net(ct);
94 pr_debug("increasing timeouts\n");
95
96 /* increase timeout of GRE data channel conntrack entry */
97 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT;
98 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
99
100 /* Can you see how rusty this code is, compared with the pre-2.6.11
101 * one? That's what happened to my shiny newnat of 2002 ;( -HW */
102
103 hook = rcu_dereference(nf_nat_pptp_hook);
104 if (hook && ct->master->status & IPS_NAT_MASK)
105 hook->expectfn(ct, exp);
106 else {
107 struct nf_conntrack_tuple inv_t;
108 struct nf_conntrack_expect *exp_other;
109
110 /* obviously this tuple inversion only works until you do NAT */
111 nf_ct_invert_tuple(&inv_t, &exp->tuple);
112 pr_debug("trying to unexpect other dir: ");
113 nf_ct_dump_tuple(&inv_t);
114
115 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t);
116 if (exp_other) {
117 /* delete other expectation. */
118 pr_debug("found\n");
119 nf_ct_unexpect_related(exp_other);
120 nf_ct_expect_put(exp_other);
121 } else {
122 pr_debug("not found\n");
123 }
124 }
125 }
126
destroy_sibling_or_exp(struct net * net,struct nf_conn * ct,const struct nf_conntrack_tuple * t)127 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct,
128 const struct nf_conntrack_tuple *t)
129 {
130 const struct nf_conntrack_tuple_hash *h;
131 const struct nf_conntrack_zone *zone;
132 struct nf_conntrack_expect *exp;
133 struct nf_conn *sibling;
134
135 pr_debug("trying to timeout ct or exp for tuple ");
136 nf_ct_dump_tuple(t);
137
138 zone = nf_ct_zone(ct);
139 h = nf_conntrack_find_get(net, zone, t);
140 if (h) {
141 sibling = nf_ct_tuplehash_to_ctrack(h);
142 pr_debug("setting timeout of conntrack %p to 0\n", sibling);
143 sibling->proto.gre.timeout = 0;
144 sibling->proto.gre.stream_timeout = 0;
145 nf_ct_kill(sibling);
146 nf_ct_put(sibling);
147 return 1;
148 } else {
149 exp = nf_ct_expect_find_get(net, zone, t);
150 if (exp) {
151 pr_debug("unexpect_related of expect %p\n", exp);
152 nf_ct_unexpect_related(exp);
153 nf_ct_expect_put(exp);
154 return 1;
155 }
156 }
157 return 0;
158 }
159
160 /* timeout GRE data connections */
pptp_destroy_siblings(struct nf_conn * ct)161 static void pptp_destroy_siblings(struct nf_conn *ct)
162 {
163 struct net *net = nf_ct_net(ct);
164 const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
165 struct nf_conntrack_tuple t;
166
167 nf_ct_gre_keymap_destroy(ct);
168
169 /* try original (pns->pac) tuple */
170 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
171 t.dst.protonum = IPPROTO_GRE;
172 t.src.u.gre.key = ct_pptp_info->pns_call_id;
173 t.dst.u.gre.key = ct_pptp_info->pac_call_id;
174 if (!destroy_sibling_or_exp(net, ct, &t))
175 pr_debug("failed to timeout original pns->pac ct/exp\n");
176
177 /* try reply (pac->pns) tuple */
178 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
179 t.dst.protonum = IPPROTO_GRE;
180 t.src.u.gre.key = ct_pptp_info->pac_call_id;
181 t.dst.u.gre.key = ct_pptp_info->pns_call_id;
182 if (!destroy_sibling_or_exp(net, ct, &t))
183 pr_debug("failed to timeout reply pac->pns ct/exp\n");
184 }
185
186 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
exp_gre(struct nf_conn * ct,__be16 callid,__be16 peer_callid)187 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
188 {
189 struct nf_conntrack_expect *exp_orig, *exp_reply;
190 const struct nf_nat_pptp_hook *hook;
191 enum ip_conntrack_dir dir;
192 int ret = 1;
193
194 exp_orig = nf_ct_expect_alloc(ct);
195 if (exp_orig == NULL)
196 goto out;
197
198 exp_reply = nf_ct_expect_alloc(ct);
199 if (exp_reply == NULL)
200 goto out_put_orig;
201
202 /* original direction, PNS->PAC */
203 dir = IP_CT_DIR_ORIGINAL;
204 nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT,
205 nf_ct_l3num(ct),
206 &ct->tuplehash[dir].tuple.src.u3,
207 &ct->tuplehash[dir].tuple.dst.u3,
208 IPPROTO_GRE, &peer_callid, &callid);
209 exp_orig->expectfn = pptp_expectfn;
210
211 /* reply direction, PAC->PNS */
212 dir = IP_CT_DIR_REPLY;
213 nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT,
214 nf_ct_l3num(ct),
215 &ct->tuplehash[dir].tuple.src.u3,
216 &ct->tuplehash[dir].tuple.dst.u3,
217 IPPROTO_GRE, &callid, &peer_callid);
218 exp_reply->expectfn = pptp_expectfn;
219
220 hook = rcu_dereference(nf_nat_pptp_hook);
221 if (hook && ct->status & IPS_NAT_MASK)
222 hook->exp_gre(exp_orig, exp_reply);
223 if (nf_ct_expect_related(exp_orig, 0) != 0)
224 goto out_put_both;
225 if (nf_ct_expect_related(exp_reply, 0) != 0)
226 goto out_unexpect_orig;
227
228 if (!nf_ct_gre_keymap_add(ct, &exp_orig->tuple,
229 &exp_reply->tuple))
230 goto out_unexpect_both;
231 ret = 0;
232
233 out_put_both:
234 nf_ct_expect_put(exp_reply);
235 out_put_orig:
236 nf_ct_expect_put(exp_orig);
237 out:
238 return ret;
239
240 out_unexpect_both:
241 nf_ct_unexpect_related(exp_reply);
242 out_unexpect_orig:
243 nf_ct_unexpect_related(exp_orig);
244 goto out_put_both;
245 }
246
247 static int
pptp_inbound_pkt(struct sk_buff * skb,unsigned int protoff,struct PptpControlHeader * ctlh,union pptp_ctrl_union * pptpReq,unsigned int reqlen,struct nf_conn * ct,enum ip_conntrack_info ctinfo)248 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
249 struct PptpControlHeader *ctlh,
250 union pptp_ctrl_union *pptpReq,
251 unsigned int reqlen,
252 struct nf_conn *ct,
253 enum ip_conntrack_info ctinfo)
254 {
255 struct nf_ct_pptp_master *info = nfct_help_data(ct);
256 const struct nf_nat_pptp_hook *hook;
257 u_int16_t msg;
258 __be16 cid = 0, pcid = 0;
259
260 msg = ntohs(ctlh->messageType);
261 pr_debug("inbound control message %s\n", pptp_msg_name(msg));
262
263 switch (msg) {
264 case PPTP_START_SESSION_REPLY:
265 /* server confirms new control session */
266 if (info->sstate < PPTP_SESSION_REQUESTED)
267 goto invalid;
268 if (pptpReq->srep.resultCode == PPTP_START_OK)
269 info->sstate = PPTP_SESSION_CONFIRMED;
270 else
271 info->sstate = PPTP_SESSION_ERROR;
272 break;
273
274 case PPTP_STOP_SESSION_REPLY:
275 /* server confirms end of control session */
276 if (info->sstate > PPTP_SESSION_STOPREQ)
277 goto invalid;
278 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
279 info->sstate = PPTP_SESSION_NONE;
280 else
281 info->sstate = PPTP_SESSION_ERROR;
282 break;
283
284 case PPTP_OUT_CALL_REPLY:
285 /* server accepted call, we now expect GRE frames */
286 if (info->sstate != PPTP_SESSION_CONFIRMED)
287 goto invalid;
288 if (info->cstate != PPTP_CALL_OUT_REQ &&
289 info->cstate != PPTP_CALL_OUT_CONF)
290 goto invalid;
291
292 cid = pptpReq->ocack.callID;
293 pcid = pptpReq->ocack.peersCallID;
294 if (info->pns_call_id != pcid)
295 goto invalid;
296 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name(msg),
297 ntohs(cid), ntohs(pcid));
298
299 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
300 info->cstate = PPTP_CALL_OUT_CONF;
301 info->pac_call_id = cid;
302 exp_gre(ct, cid, pcid);
303 } else
304 info->cstate = PPTP_CALL_NONE;
305 break;
306
307 case PPTP_IN_CALL_REQUEST:
308 /* server tells us about incoming call request */
309 if (info->sstate != PPTP_SESSION_CONFIRMED)
310 goto invalid;
311
312 cid = pptpReq->icreq.callID;
313 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
314 info->cstate = PPTP_CALL_IN_REQ;
315 info->pac_call_id = cid;
316 break;
317
318 case PPTP_IN_CALL_CONNECT:
319 /* server tells us about incoming call established */
320 if (info->sstate != PPTP_SESSION_CONFIRMED)
321 goto invalid;
322 if (info->cstate != PPTP_CALL_IN_REP &&
323 info->cstate != PPTP_CALL_IN_CONF)
324 goto invalid;
325
326 pcid = pptpReq->iccon.peersCallID;
327 cid = info->pac_call_id;
328
329 if (info->pns_call_id != pcid)
330 goto invalid;
331
332 pr_debug("%s, PCID=%X\n", pptp_msg_name(msg), ntohs(pcid));
333 info->cstate = PPTP_CALL_IN_CONF;
334
335 /* we expect a GRE connection from PAC to PNS */
336 exp_gre(ct, cid, pcid);
337 break;
338
339 case PPTP_CALL_DISCONNECT_NOTIFY:
340 /* server confirms disconnect */
341 cid = pptpReq->disc.callID;
342 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
343 info->cstate = PPTP_CALL_NONE;
344
345 /* untrack this call id, unexpect GRE packets */
346 pptp_destroy_siblings(ct);
347 break;
348
349 case PPTP_WAN_ERROR_NOTIFY:
350 case PPTP_SET_LINK_INFO:
351 case PPTP_ECHO_REQUEST:
352 case PPTP_ECHO_REPLY:
353 /* I don't have to explain these ;) */
354 break;
355
356 default:
357 goto invalid;
358 }
359
360 hook = rcu_dereference(nf_nat_pptp_hook);
361 if (hook && ct->status & IPS_NAT_MASK)
362 return hook->inbound(skb, ct, ctinfo, protoff, ctlh, pptpReq);
363 return NF_ACCEPT;
364
365 invalid:
366 pr_debug("invalid %s: type=%d cid=%u pcid=%u "
367 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
368 pptp_msg_name(msg),
369 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate,
370 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
371 return NF_ACCEPT;
372 }
373
374 static int
pptp_outbound_pkt(struct sk_buff * skb,unsigned int protoff,struct PptpControlHeader * ctlh,union pptp_ctrl_union * pptpReq,unsigned int reqlen,struct nf_conn * ct,enum ip_conntrack_info ctinfo)375 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
376 struct PptpControlHeader *ctlh,
377 union pptp_ctrl_union *pptpReq,
378 unsigned int reqlen,
379 struct nf_conn *ct,
380 enum ip_conntrack_info ctinfo)
381 {
382 struct nf_ct_pptp_master *info = nfct_help_data(ct);
383 const struct nf_nat_pptp_hook *hook;
384 u_int16_t msg;
385 __be16 cid = 0, pcid = 0;
386
387 msg = ntohs(ctlh->messageType);
388 pr_debug("outbound control message %s\n", pptp_msg_name(msg));
389
390 switch (msg) {
391 case PPTP_START_SESSION_REQUEST:
392 /* client requests for new control session */
393 if (info->sstate != PPTP_SESSION_NONE)
394 goto invalid;
395 info->sstate = PPTP_SESSION_REQUESTED;
396 break;
397
398 case PPTP_STOP_SESSION_REQUEST:
399 /* client requests end of control session */
400 info->sstate = PPTP_SESSION_STOPREQ;
401 break;
402
403 case PPTP_OUT_CALL_REQUEST:
404 /* client initiating connection to server */
405 if (info->sstate != PPTP_SESSION_CONFIRMED)
406 goto invalid;
407 info->cstate = PPTP_CALL_OUT_REQ;
408 /* track PNS call id */
409 cid = pptpReq->ocreq.callID;
410 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
411 info->pns_call_id = cid;
412 break;
413
414 case PPTP_IN_CALL_REPLY:
415 /* client answers incoming call */
416 if (info->cstate != PPTP_CALL_IN_REQ &&
417 info->cstate != PPTP_CALL_IN_REP)
418 goto invalid;
419
420 cid = pptpReq->icack.callID;
421 pcid = pptpReq->icack.peersCallID;
422 if (info->pac_call_id != pcid)
423 goto invalid;
424 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name(msg),
425 ntohs(cid), ntohs(pcid));
426
427 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
428 /* part two of the three-way handshake */
429 info->cstate = PPTP_CALL_IN_REP;
430 info->pns_call_id = cid;
431 } else
432 info->cstate = PPTP_CALL_NONE;
433 break;
434
435 case PPTP_CALL_CLEAR_REQUEST:
436 /* client requests hangup of call */
437 if (info->sstate != PPTP_SESSION_CONFIRMED)
438 goto invalid;
439 /* FUTURE: iterate over all calls and check if
440 * call ID is valid. We don't do this without newnat,
441 * because we only know about last call */
442 info->cstate = PPTP_CALL_CLEAR_REQ;
443 break;
444
445 case PPTP_SET_LINK_INFO:
446 case PPTP_ECHO_REQUEST:
447 case PPTP_ECHO_REPLY:
448 /* I don't have to explain these ;) */
449 break;
450
451 default:
452 goto invalid;
453 }
454
455 hook = rcu_dereference(nf_nat_pptp_hook);
456 if (hook && ct->status & IPS_NAT_MASK)
457 return hook->outbound(skb, ct, ctinfo, protoff, ctlh, pptpReq);
458 return NF_ACCEPT;
459
460 invalid:
461 pr_debug("invalid %s: type=%d cid=%u pcid=%u "
462 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
463 pptp_msg_name(msg),
464 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate,
465 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
466 return NF_ACCEPT;
467 }
468
469 static const unsigned int pptp_msg_size[] = {
470 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest),
471 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply),
472 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest),
473 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply),
474 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest),
475 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply),
476 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest),
477 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply),
478 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected),
479 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest),
480 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
481 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify),
482 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo),
483 };
484
485 /* track caller id inside control connection, call expect_related */
486 static int
conntrack_pptp_help(struct sk_buff * skb,unsigned int protoff,struct nf_conn * ct,enum ip_conntrack_info ctinfo)487 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
488 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
489
490 {
491 int dir = CTINFO2DIR(ctinfo);
492 const struct nf_ct_pptp_master *info = nfct_help_data(ct);
493 const struct tcphdr *tcph;
494 struct tcphdr _tcph;
495 const struct pptp_pkt_hdr *pptph;
496 struct pptp_pkt_hdr _pptph;
497 struct PptpControlHeader _ctlh, *ctlh;
498 union pptp_ctrl_union _pptpReq, *pptpReq;
499 unsigned int tcplen = skb->len - protoff;
500 unsigned int datalen, reqlen, nexthdr_off;
501 int oldsstate, oldcstate;
502 int ret;
503 u_int16_t msg;
504
505 #if IS_ENABLED(CONFIG_NF_NAT)
506 if (!nf_ct_is_confirmed(ct) && (ct->status & IPS_NAT_MASK)) {
507 struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT);
508
509 if (!nat && !nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC))
510 return NF_DROP;
511 }
512 #endif
513 /* don't do any tracking before tcp handshake complete */
514 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
515 return NF_ACCEPT;
516
517 nexthdr_off = protoff;
518 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
519 if (!tcph)
520 return NF_ACCEPT;
521
522 nexthdr_off += tcph->doff * 4;
523 datalen = tcplen - tcph->doff * 4;
524
525 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
526 if (!pptph) {
527 pr_debug("no full PPTP header, can't track\n");
528 return NF_ACCEPT;
529 }
530 nexthdr_off += sizeof(_pptph);
531 datalen -= sizeof(_pptph);
532
533 /* if it's not a control message we can't do anything with it */
534 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
535 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
536 pr_debug("not a control packet\n");
537 return NF_ACCEPT;
538 }
539
540 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
541 if (!ctlh)
542 return NF_ACCEPT;
543 nexthdr_off += sizeof(_ctlh);
544 datalen -= sizeof(_ctlh);
545
546 reqlen = datalen;
547 msg = ntohs(ctlh->messageType);
548 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
549 return NF_ACCEPT;
550 if (reqlen > sizeof(*pptpReq))
551 reqlen = sizeof(*pptpReq);
552
553 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
554 if (!pptpReq)
555 return NF_ACCEPT;
556
557 oldsstate = info->sstate;
558 oldcstate = info->cstate;
559
560 spin_lock_bh(&nf_pptp_lock);
561
562 /* FIXME: We just blindly assume that the control connection is always
563 * established from PNS->PAC. However, RFC makes no guarantee */
564 if (dir == IP_CT_DIR_ORIGINAL)
565 /* client -> server (PNS -> PAC) */
566 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
567 ctinfo);
568 else
569 /* server -> client (PAC -> PNS) */
570 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
571 ctinfo);
572 pr_debug("sstate: %d->%d, cstate: %d->%d\n",
573 oldsstate, info->sstate, oldcstate, info->cstate);
574 spin_unlock_bh(&nf_pptp_lock);
575
576 return ret;
577 }
578
579 static const struct nf_conntrack_expect_policy pptp_exp_policy = {
580 .max_expected = 2,
581 .timeout = 5 * 60,
582 };
583
584 /* control protocol helper */
585 static struct nf_conntrack_helper pptp __read_mostly = {
586 .name = "pptp",
587 .me = THIS_MODULE,
588 .tuple.src.l3num = AF_INET,
589 .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT),
590 .tuple.dst.protonum = IPPROTO_TCP,
591 .help = conntrack_pptp_help,
592 .destroy = pptp_destroy_siblings,
593 .expect_policy = &pptp_exp_policy,
594 };
595
nf_conntrack_pptp_init(void)596 static int __init nf_conntrack_pptp_init(void)
597 {
598 NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_pptp_master));
599
600 return nf_conntrack_helper_register(&pptp);
601 }
602
nf_conntrack_pptp_fini(void)603 static void __exit nf_conntrack_pptp_fini(void)
604 {
605 nf_conntrack_helper_unregister(&pptp);
606 }
607
608 module_init(nf_conntrack_pptp_init);
609 module_exit(nf_conntrack_pptp_fini);
610