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 int
49 (*nf_nat_pptp_hook_outbound)(struct sk_buff *skb,
50 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
51 unsigned int protoff, struct PptpControlHeader *ctlh,
52 union pptp_ctrl_union *pptpReq) __read_mostly;
53 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound);
54
55 int
56 (*nf_nat_pptp_hook_inbound)(struct sk_buff *skb,
57 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
58 unsigned int protoff, struct PptpControlHeader *ctlh,
59 union pptp_ctrl_union *pptpReq) __read_mostly;
60 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound);
61
62 void
63 (*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig,
64 struct nf_conntrack_expect *expect_reply)
65 __read_mostly;
66 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre);
67
68 void
69 (*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct,
70 struct nf_conntrack_expect *exp) __read_mostly;
71 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
72
73 #if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
74 /* PptpControlMessageType names */
75 static const char *const pptp_msg_name_array[PPTP_MSG_MAX + 1] = {
76 [0] = "UNKNOWN_MESSAGE",
77 [PPTP_START_SESSION_REQUEST] = "START_SESSION_REQUEST",
78 [PPTP_START_SESSION_REPLY] = "START_SESSION_REPLY",
79 [PPTP_STOP_SESSION_REQUEST] = "STOP_SESSION_REQUEST",
80 [PPTP_STOP_SESSION_REPLY] = "STOP_SESSION_REPLY",
81 [PPTP_ECHO_REQUEST] = "ECHO_REQUEST",
82 [PPTP_ECHO_REPLY] = "ECHO_REPLY",
83 [PPTP_OUT_CALL_REQUEST] = "OUT_CALL_REQUEST",
84 [PPTP_OUT_CALL_REPLY] = "OUT_CALL_REPLY",
85 [PPTP_IN_CALL_REQUEST] = "IN_CALL_REQUEST",
86 [PPTP_IN_CALL_REPLY] = "IN_CALL_REPLY",
87 [PPTP_IN_CALL_CONNECT] = "IN_CALL_CONNECT",
88 [PPTP_CALL_CLEAR_REQUEST] = "CALL_CLEAR_REQUEST",
89 [PPTP_CALL_DISCONNECT_NOTIFY] = "CALL_DISCONNECT_NOTIFY",
90 [PPTP_WAN_ERROR_NOTIFY] = "WAN_ERROR_NOTIFY",
91 [PPTP_SET_LINK_INFO] = "SET_LINK_INFO"
92 };
93
pptp_msg_name(u_int16_t msg)94 const char *pptp_msg_name(u_int16_t msg)
95 {
96 if (msg > PPTP_MSG_MAX)
97 return pptp_msg_name_array[0];
98
99 return pptp_msg_name_array[msg];
100 }
101 EXPORT_SYMBOL(pptp_msg_name);
102 #endif
103
104 #define SECS *HZ
105 #define MINS * 60 SECS
106 #define HOURS * 60 MINS
107
108 #define PPTP_GRE_TIMEOUT (10 MINS)
109 #define PPTP_GRE_STREAM_TIMEOUT (5 HOURS)
110
pptp_expectfn(struct nf_conn * ct,struct nf_conntrack_expect * exp)111 static void pptp_expectfn(struct nf_conn *ct,
112 struct nf_conntrack_expect *exp)
113 {
114 struct net *net = nf_ct_net(ct);
115 typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn;
116 pr_debug("increasing timeouts\n");
117
118 /* increase timeout of GRE data channel conntrack entry */
119 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT;
120 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
121
122 /* Can you see how rusty this code is, compared with the pre-2.6.11
123 * one? That's what happened to my shiny newnat of 2002 ;( -HW */
124
125 nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn);
126 if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK)
127 nf_nat_pptp_expectfn(ct, exp);
128 else {
129 struct nf_conntrack_tuple inv_t;
130 struct nf_conntrack_expect *exp_other;
131
132 /* obviously this tuple inversion only works until you do NAT */
133 nf_ct_invert_tuple(&inv_t, &exp->tuple);
134 pr_debug("trying to unexpect other dir: ");
135 nf_ct_dump_tuple(&inv_t);
136
137 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t);
138 if (exp_other) {
139 /* delete other expectation. */
140 pr_debug("found\n");
141 nf_ct_unexpect_related(exp_other);
142 nf_ct_expect_put(exp_other);
143 } else {
144 pr_debug("not found\n");
145 }
146 }
147 }
148
destroy_sibling_or_exp(struct net * net,struct nf_conn * ct,const struct nf_conntrack_tuple * t)149 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct,
150 const struct nf_conntrack_tuple *t)
151 {
152 const struct nf_conntrack_tuple_hash *h;
153 const struct nf_conntrack_zone *zone;
154 struct nf_conntrack_expect *exp;
155 struct nf_conn *sibling;
156
157 pr_debug("trying to timeout ct or exp for tuple ");
158 nf_ct_dump_tuple(t);
159
160 zone = nf_ct_zone(ct);
161 h = nf_conntrack_find_get(net, zone, t);
162 if (h) {
163 sibling = nf_ct_tuplehash_to_ctrack(h);
164 pr_debug("setting timeout of conntrack %p to 0\n", sibling);
165 sibling->proto.gre.timeout = 0;
166 sibling->proto.gre.stream_timeout = 0;
167 nf_ct_kill(sibling);
168 nf_ct_put(sibling);
169 return 1;
170 } else {
171 exp = nf_ct_expect_find_get(net, zone, t);
172 if (exp) {
173 pr_debug("unexpect_related of expect %p\n", exp);
174 nf_ct_unexpect_related(exp);
175 nf_ct_expect_put(exp);
176 return 1;
177 }
178 }
179 return 0;
180 }
181
182 /* timeout GRE data connections */
pptp_destroy_siblings(struct nf_conn * ct)183 static void pptp_destroy_siblings(struct nf_conn *ct)
184 {
185 struct net *net = nf_ct_net(ct);
186 const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
187 struct nf_conntrack_tuple t;
188
189 nf_ct_gre_keymap_destroy(ct);
190
191 /* try original (pns->pac) tuple */
192 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
193 t.dst.protonum = IPPROTO_GRE;
194 t.src.u.gre.key = ct_pptp_info->pns_call_id;
195 t.dst.u.gre.key = ct_pptp_info->pac_call_id;
196 if (!destroy_sibling_or_exp(net, ct, &t))
197 pr_debug("failed to timeout original pns->pac ct/exp\n");
198
199 /* try reply (pac->pns) tuple */
200 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
201 t.dst.protonum = IPPROTO_GRE;
202 t.src.u.gre.key = ct_pptp_info->pac_call_id;
203 t.dst.u.gre.key = ct_pptp_info->pns_call_id;
204 if (!destroy_sibling_or_exp(net, ct, &t))
205 pr_debug("failed to timeout reply pac->pns ct/exp\n");
206 }
207
208 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
exp_gre(struct nf_conn * ct,__be16 callid,__be16 peer_callid)209 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
210 {
211 struct nf_conntrack_expect *exp_orig, *exp_reply;
212 enum ip_conntrack_dir dir;
213 int ret = 1;
214 typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre;
215
216 exp_orig = nf_ct_expect_alloc(ct);
217 if (exp_orig == NULL)
218 goto out;
219
220 exp_reply = nf_ct_expect_alloc(ct);
221 if (exp_reply == NULL)
222 goto out_put_orig;
223
224 /* original direction, PNS->PAC */
225 dir = IP_CT_DIR_ORIGINAL;
226 nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT,
227 nf_ct_l3num(ct),
228 &ct->tuplehash[dir].tuple.src.u3,
229 &ct->tuplehash[dir].tuple.dst.u3,
230 IPPROTO_GRE, &peer_callid, &callid);
231 exp_orig->expectfn = pptp_expectfn;
232
233 /* reply direction, PAC->PNS */
234 dir = IP_CT_DIR_REPLY;
235 nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT,
236 nf_ct_l3num(ct),
237 &ct->tuplehash[dir].tuple.src.u3,
238 &ct->tuplehash[dir].tuple.dst.u3,
239 IPPROTO_GRE, &callid, &peer_callid);
240 exp_reply->expectfn = pptp_expectfn;
241
242 nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre);
243 if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK)
244 nf_nat_pptp_exp_gre(exp_orig, exp_reply);
245 if (nf_ct_expect_related(exp_orig, 0) != 0)
246 goto out_put_both;
247 if (nf_ct_expect_related(exp_reply, 0) != 0)
248 goto out_unexpect_orig;
249
250 /* Add GRE keymap entries */
251 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
252 goto out_unexpect_both;
253 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
254 nf_ct_gre_keymap_destroy(ct);
255 goto out_unexpect_both;
256 }
257 ret = 0;
258
259 out_put_both:
260 nf_ct_expect_put(exp_reply);
261 out_put_orig:
262 nf_ct_expect_put(exp_orig);
263 out:
264 return ret;
265
266 out_unexpect_both:
267 nf_ct_unexpect_related(exp_reply);
268 out_unexpect_orig:
269 nf_ct_unexpect_related(exp_orig);
270 goto out_put_both;
271 }
272
273 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)274 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
275 struct PptpControlHeader *ctlh,
276 union pptp_ctrl_union *pptpReq,
277 unsigned int reqlen,
278 struct nf_conn *ct,
279 enum ip_conntrack_info ctinfo)
280 {
281 struct nf_ct_pptp_master *info = nfct_help_data(ct);
282 u_int16_t msg;
283 __be16 cid = 0, pcid = 0;
284 typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
285
286 msg = ntohs(ctlh->messageType);
287 pr_debug("inbound control message %s\n", pptp_msg_name(msg));
288
289 switch (msg) {
290 case PPTP_START_SESSION_REPLY:
291 /* server confirms new control session */
292 if (info->sstate < PPTP_SESSION_REQUESTED)
293 goto invalid;
294 if (pptpReq->srep.resultCode == PPTP_START_OK)
295 info->sstate = PPTP_SESSION_CONFIRMED;
296 else
297 info->sstate = PPTP_SESSION_ERROR;
298 break;
299
300 case PPTP_STOP_SESSION_REPLY:
301 /* server confirms end of control session */
302 if (info->sstate > PPTP_SESSION_STOPREQ)
303 goto invalid;
304 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
305 info->sstate = PPTP_SESSION_NONE;
306 else
307 info->sstate = PPTP_SESSION_ERROR;
308 break;
309
310 case PPTP_OUT_CALL_REPLY:
311 /* server accepted call, we now expect GRE frames */
312 if (info->sstate != PPTP_SESSION_CONFIRMED)
313 goto invalid;
314 if (info->cstate != PPTP_CALL_OUT_REQ &&
315 info->cstate != PPTP_CALL_OUT_CONF)
316 goto invalid;
317
318 cid = pptpReq->ocack.callID;
319 pcid = pptpReq->ocack.peersCallID;
320 if (info->pns_call_id != pcid)
321 goto invalid;
322 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name(msg),
323 ntohs(cid), ntohs(pcid));
324
325 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
326 info->cstate = PPTP_CALL_OUT_CONF;
327 info->pac_call_id = cid;
328 exp_gre(ct, cid, pcid);
329 } else
330 info->cstate = PPTP_CALL_NONE;
331 break;
332
333 case PPTP_IN_CALL_REQUEST:
334 /* server tells us about incoming call request */
335 if (info->sstate != PPTP_SESSION_CONFIRMED)
336 goto invalid;
337
338 cid = pptpReq->icreq.callID;
339 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
340 info->cstate = PPTP_CALL_IN_REQ;
341 info->pac_call_id = cid;
342 break;
343
344 case PPTP_IN_CALL_CONNECT:
345 /* server tells us about incoming call established */
346 if (info->sstate != PPTP_SESSION_CONFIRMED)
347 goto invalid;
348 if (info->cstate != PPTP_CALL_IN_REP &&
349 info->cstate != PPTP_CALL_IN_CONF)
350 goto invalid;
351
352 pcid = pptpReq->iccon.peersCallID;
353 cid = info->pac_call_id;
354
355 if (info->pns_call_id != pcid)
356 goto invalid;
357
358 pr_debug("%s, PCID=%X\n", pptp_msg_name(msg), ntohs(pcid));
359 info->cstate = PPTP_CALL_IN_CONF;
360
361 /* we expect a GRE connection from PAC to PNS */
362 exp_gre(ct, cid, pcid);
363 break;
364
365 case PPTP_CALL_DISCONNECT_NOTIFY:
366 /* server confirms disconnect */
367 cid = pptpReq->disc.callID;
368 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
369 info->cstate = PPTP_CALL_NONE;
370
371 /* untrack this call id, unexpect GRE packets */
372 pptp_destroy_siblings(ct);
373 break;
374
375 case PPTP_WAN_ERROR_NOTIFY:
376 case PPTP_SET_LINK_INFO:
377 case PPTP_ECHO_REQUEST:
378 case PPTP_ECHO_REPLY:
379 /* I don't have to explain these ;) */
380 break;
381
382 default:
383 goto invalid;
384 }
385
386 nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound);
387 if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK)
388 return nf_nat_pptp_inbound(skb, ct, ctinfo,
389 protoff, ctlh, pptpReq);
390 return NF_ACCEPT;
391
392 invalid:
393 pr_debug("invalid %s: type=%d cid=%u pcid=%u "
394 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
395 pptp_msg_name(msg),
396 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate,
397 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
398 return NF_ACCEPT;
399 }
400
401 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)402 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
403 struct PptpControlHeader *ctlh,
404 union pptp_ctrl_union *pptpReq,
405 unsigned int reqlen,
406 struct nf_conn *ct,
407 enum ip_conntrack_info ctinfo)
408 {
409 struct nf_ct_pptp_master *info = nfct_help_data(ct);
410 u_int16_t msg;
411 __be16 cid = 0, pcid = 0;
412 typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
413
414 msg = ntohs(ctlh->messageType);
415 pr_debug("outbound control message %s\n", pptp_msg_name(msg));
416
417 switch (msg) {
418 case PPTP_START_SESSION_REQUEST:
419 /* client requests for new control session */
420 if (info->sstate != PPTP_SESSION_NONE)
421 goto invalid;
422 info->sstate = PPTP_SESSION_REQUESTED;
423 break;
424
425 case PPTP_STOP_SESSION_REQUEST:
426 /* client requests end of control session */
427 info->sstate = PPTP_SESSION_STOPREQ;
428 break;
429
430 case PPTP_OUT_CALL_REQUEST:
431 /* client initiating connection to server */
432 if (info->sstate != PPTP_SESSION_CONFIRMED)
433 goto invalid;
434 info->cstate = PPTP_CALL_OUT_REQ;
435 /* track PNS call id */
436 cid = pptpReq->ocreq.callID;
437 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
438 info->pns_call_id = cid;
439 break;
440
441 case PPTP_IN_CALL_REPLY:
442 /* client answers incoming call */
443 if (info->cstate != PPTP_CALL_IN_REQ &&
444 info->cstate != PPTP_CALL_IN_REP)
445 goto invalid;
446
447 cid = pptpReq->icack.callID;
448 pcid = pptpReq->icack.peersCallID;
449 if (info->pac_call_id != pcid)
450 goto invalid;
451 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name(msg),
452 ntohs(cid), ntohs(pcid));
453
454 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
455 /* part two of the three-way handshake */
456 info->cstate = PPTP_CALL_IN_REP;
457 info->pns_call_id = cid;
458 } else
459 info->cstate = PPTP_CALL_NONE;
460 break;
461
462 case PPTP_CALL_CLEAR_REQUEST:
463 /* client requests hangup of call */
464 if (info->sstate != PPTP_SESSION_CONFIRMED)
465 goto invalid;
466 /* FUTURE: iterate over all calls and check if
467 * call ID is valid. We don't do this without newnat,
468 * because we only know about last call */
469 info->cstate = PPTP_CALL_CLEAR_REQ;
470 break;
471
472 case PPTP_SET_LINK_INFO:
473 case PPTP_ECHO_REQUEST:
474 case PPTP_ECHO_REPLY:
475 /* I don't have to explain these ;) */
476 break;
477
478 default:
479 goto invalid;
480 }
481
482 nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound);
483 if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK)
484 return nf_nat_pptp_outbound(skb, ct, ctinfo,
485 protoff, ctlh, pptpReq);
486 return NF_ACCEPT;
487
488 invalid:
489 pr_debug("invalid %s: type=%d cid=%u pcid=%u "
490 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
491 pptp_msg_name(msg),
492 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate,
493 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
494 return NF_ACCEPT;
495 }
496
497 static const unsigned int pptp_msg_size[] = {
498 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest),
499 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply),
500 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest),
501 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply),
502 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest),
503 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply),
504 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest),
505 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply),
506 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected),
507 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest),
508 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
509 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify),
510 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo),
511 };
512
513 /* track caller id inside control connection, call expect_related */
514 static int
conntrack_pptp_help(struct sk_buff * skb,unsigned int protoff,struct nf_conn * ct,enum ip_conntrack_info ctinfo)515 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
516 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
517
518 {
519 int dir = CTINFO2DIR(ctinfo);
520 const struct nf_ct_pptp_master *info = nfct_help_data(ct);
521 const struct tcphdr *tcph;
522 struct tcphdr _tcph;
523 const struct pptp_pkt_hdr *pptph;
524 struct pptp_pkt_hdr _pptph;
525 struct PptpControlHeader _ctlh, *ctlh;
526 union pptp_ctrl_union _pptpReq, *pptpReq;
527 unsigned int tcplen = skb->len - protoff;
528 unsigned int datalen, reqlen, nexthdr_off;
529 int oldsstate, oldcstate;
530 int ret;
531 u_int16_t msg;
532
533 #if IS_ENABLED(CONFIG_NF_NAT)
534 if (!nf_ct_is_confirmed(ct) && (ct->status & IPS_NAT_MASK)) {
535 struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT);
536
537 if (!nat && !nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC))
538 return NF_DROP;
539 }
540 #endif
541 /* don't do any tracking before tcp handshake complete */
542 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
543 return NF_ACCEPT;
544
545 nexthdr_off = protoff;
546 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
547 if (!tcph)
548 return NF_ACCEPT;
549
550 nexthdr_off += tcph->doff * 4;
551 datalen = tcplen - tcph->doff * 4;
552
553 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
554 if (!pptph) {
555 pr_debug("no full PPTP header, can't track\n");
556 return NF_ACCEPT;
557 }
558 nexthdr_off += sizeof(_pptph);
559 datalen -= sizeof(_pptph);
560
561 /* if it's not a control message we can't do anything with it */
562 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
563 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
564 pr_debug("not a control packet\n");
565 return NF_ACCEPT;
566 }
567
568 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
569 if (!ctlh)
570 return NF_ACCEPT;
571 nexthdr_off += sizeof(_ctlh);
572 datalen -= sizeof(_ctlh);
573
574 reqlen = datalen;
575 msg = ntohs(ctlh->messageType);
576 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
577 return NF_ACCEPT;
578 if (reqlen > sizeof(*pptpReq))
579 reqlen = sizeof(*pptpReq);
580
581 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
582 if (!pptpReq)
583 return NF_ACCEPT;
584
585 oldsstate = info->sstate;
586 oldcstate = info->cstate;
587
588 spin_lock_bh(&nf_pptp_lock);
589
590 /* FIXME: We just blindly assume that the control connection is always
591 * established from PNS->PAC. However, RFC makes no guarantee */
592 if (dir == IP_CT_DIR_ORIGINAL)
593 /* client -> server (PNS -> PAC) */
594 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
595 ctinfo);
596 else
597 /* server -> client (PAC -> PNS) */
598 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
599 ctinfo);
600 pr_debug("sstate: %d->%d, cstate: %d->%d\n",
601 oldsstate, info->sstate, oldcstate, info->cstate);
602 spin_unlock_bh(&nf_pptp_lock);
603
604 return ret;
605 }
606
607 static const struct nf_conntrack_expect_policy pptp_exp_policy = {
608 .max_expected = 2,
609 .timeout = 5 * 60,
610 };
611
612 /* control protocol helper */
613 static struct nf_conntrack_helper pptp __read_mostly = {
614 .name = "pptp",
615 .me = THIS_MODULE,
616 .tuple.src.l3num = AF_INET,
617 .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT),
618 .tuple.dst.protonum = IPPROTO_TCP,
619 .help = conntrack_pptp_help,
620 .destroy = pptp_destroy_siblings,
621 .expect_policy = &pptp_exp_policy,
622 };
623
nf_conntrack_pptp_init(void)624 static int __init nf_conntrack_pptp_init(void)
625 {
626 NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_pptp_master));
627
628 return nf_conntrack_helper_register(&pptp);
629 }
630
nf_conntrack_pptp_fini(void)631 static void __exit nf_conntrack_pptp_fini(void)
632 {
633 nf_conntrack_helper_unregister(&pptp);
634 }
635
636 module_init(nf_conntrack_pptp_init);
637 module_exit(nf_conntrack_pptp_fini);
638