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 | |
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 | |
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(inverse: &inv_t, orig: &exp->tuple); |
112 | pr_debug("trying to unexpect other dir: " ); |
113 | nf_ct_dump_tuple(t: &inv_t); |
114 | |
115 | exp_other = nf_ct_expect_find_get(net, zone: nf_ct_zone(ct), tuple: &inv_t); |
116 | if (exp_other) { |
117 | /* delete other expectation. */ |
118 | pr_debug("found\n" ); |
119 | nf_ct_unexpect_related(exp: exp_other); |
120 | nf_ct_expect_put(exp: exp_other); |
121 | } else { |
122 | pr_debug("not found\n" ); |
123 | } |
124 | } |
125 | } |
126 | |
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, tuple: t); |
140 | if (h) { |
141 | sibling = nf_ct_tuplehash_to_ctrack(hash: 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(ct: sibling); |
146 | nf_ct_put(ct: sibling); |
147 | return 1; |
148 | } else { |
149 | exp = nf_ct_expect_find_get(net, zone, tuple: 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 */ |
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: &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: &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) */ |
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(me: ct); |
195 | if (exp_orig == NULL) |
196 | goto out; |
197 | |
198 | exp_reply = nf_ct_expect_alloc(me: 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(expect: exp_orig, flags: 0) != 0) |
224 | goto out_put_both; |
225 | if (nf_ct_expect_related(expect: exp_reply, flags: 0) != 0) |
226 | goto out_unexpect_orig; |
227 | |
228 | /* Add GRE keymap entries */ |
229 | if (nf_ct_gre_keymap_add(ct, dir: IP_CT_DIR_ORIGINAL, t: &exp_orig->tuple) != 0) |
230 | goto out_unexpect_both; |
231 | if (nf_ct_gre_keymap_add(ct, dir: IP_CT_DIR_REPLY, t: &exp_reply->tuple) != 0) { |
232 | nf_ct_gre_keymap_destroy(ct); |
233 | goto out_unexpect_both; |
234 | } |
235 | ret = 0; |
236 | |
237 | out_put_both: |
238 | nf_ct_expect_put(exp: exp_reply); |
239 | out_put_orig: |
240 | nf_ct_expect_put(exp: exp_orig); |
241 | out: |
242 | return ret; |
243 | |
244 | out_unexpect_both: |
245 | nf_ct_unexpect_related(exp: exp_reply); |
246 | out_unexpect_orig: |
247 | nf_ct_unexpect_related(exp: exp_orig); |
248 | goto out_put_both; |
249 | } |
250 | |
251 | static int |
252 | pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff, |
253 | struct PptpControlHeader *ctlh, |
254 | union pptp_ctrl_union *pptpReq, |
255 | unsigned int reqlen, |
256 | struct nf_conn *ct, |
257 | enum ip_conntrack_info ctinfo) |
258 | { |
259 | struct nf_ct_pptp_master *info = nfct_help_data(ct); |
260 | const struct nf_nat_pptp_hook *hook; |
261 | u_int16_t msg; |
262 | __be16 cid = 0, pcid = 0; |
263 | |
264 | msg = ntohs(ctlh->messageType); |
265 | pr_debug("inbound control message %s\n" , pptp_msg_name(msg)); |
266 | |
267 | switch (msg) { |
268 | case PPTP_START_SESSION_REPLY: |
269 | /* server confirms new control session */ |
270 | if (info->sstate < PPTP_SESSION_REQUESTED) |
271 | goto invalid; |
272 | if (pptpReq->srep.resultCode == PPTP_START_OK) |
273 | info->sstate = PPTP_SESSION_CONFIRMED; |
274 | else |
275 | info->sstate = PPTP_SESSION_ERROR; |
276 | break; |
277 | |
278 | case PPTP_STOP_SESSION_REPLY: |
279 | /* server confirms end of control session */ |
280 | if (info->sstate > PPTP_SESSION_STOPREQ) |
281 | goto invalid; |
282 | if (pptpReq->strep.resultCode == PPTP_STOP_OK) |
283 | info->sstate = PPTP_SESSION_NONE; |
284 | else |
285 | info->sstate = PPTP_SESSION_ERROR; |
286 | break; |
287 | |
288 | case PPTP_OUT_CALL_REPLY: |
289 | /* server accepted call, we now expect GRE frames */ |
290 | if (info->sstate != PPTP_SESSION_CONFIRMED) |
291 | goto invalid; |
292 | if (info->cstate != PPTP_CALL_OUT_REQ && |
293 | info->cstate != PPTP_CALL_OUT_CONF) |
294 | goto invalid; |
295 | |
296 | cid = pptpReq->ocack.callID; |
297 | pcid = pptpReq->ocack.peersCallID; |
298 | if (info->pns_call_id != pcid) |
299 | goto invalid; |
300 | pr_debug("%s, CID=%X, PCID=%X\n" , pptp_msg_name(msg), |
301 | ntohs(cid), ntohs(pcid)); |
302 | |
303 | if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) { |
304 | info->cstate = PPTP_CALL_OUT_CONF; |
305 | info->pac_call_id = cid; |
306 | exp_gre(ct, callid: cid, peer_callid: pcid); |
307 | } else |
308 | info->cstate = PPTP_CALL_NONE; |
309 | break; |
310 | |
311 | case PPTP_IN_CALL_REQUEST: |
312 | /* server tells us about incoming call request */ |
313 | if (info->sstate != PPTP_SESSION_CONFIRMED) |
314 | goto invalid; |
315 | |
316 | cid = pptpReq->icreq.callID; |
317 | pr_debug("%s, CID=%X\n" , pptp_msg_name(msg), ntohs(cid)); |
318 | info->cstate = PPTP_CALL_IN_REQ; |
319 | info->pac_call_id = cid; |
320 | break; |
321 | |
322 | case PPTP_IN_CALL_CONNECT: |
323 | /* server tells us about incoming call established */ |
324 | if (info->sstate != PPTP_SESSION_CONFIRMED) |
325 | goto invalid; |
326 | if (info->cstate != PPTP_CALL_IN_REP && |
327 | info->cstate != PPTP_CALL_IN_CONF) |
328 | goto invalid; |
329 | |
330 | pcid = pptpReq->iccon.peersCallID; |
331 | cid = info->pac_call_id; |
332 | |
333 | if (info->pns_call_id != pcid) |
334 | goto invalid; |
335 | |
336 | pr_debug("%s, PCID=%X\n" , pptp_msg_name(msg), ntohs(pcid)); |
337 | info->cstate = PPTP_CALL_IN_CONF; |
338 | |
339 | /* we expect a GRE connection from PAC to PNS */ |
340 | exp_gre(ct, callid: cid, peer_callid: pcid); |
341 | break; |
342 | |
343 | case PPTP_CALL_DISCONNECT_NOTIFY: |
344 | /* server confirms disconnect */ |
345 | cid = pptpReq->disc.callID; |
346 | pr_debug("%s, CID=%X\n" , pptp_msg_name(msg), ntohs(cid)); |
347 | info->cstate = PPTP_CALL_NONE; |
348 | |
349 | /* untrack this call id, unexpect GRE packets */ |
350 | pptp_destroy_siblings(ct); |
351 | break; |
352 | |
353 | case PPTP_WAN_ERROR_NOTIFY: |
354 | case PPTP_SET_LINK_INFO: |
355 | case PPTP_ECHO_REQUEST: |
356 | case PPTP_ECHO_REPLY: |
357 | /* I don't have to explain these ;) */ |
358 | break; |
359 | |
360 | default: |
361 | goto invalid; |
362 | } |
363 | |
364 | hook = rcu_dereference(nf_nat_pptp_hook); |
365 | if (hook && ct->status & IPS_NAT_MASK) |
366 | return hook->inbound(skb, ct, ctinfo, protoff, ctlh, pptpReq); |
367 | return NF_ACCEPT; |
368 | |
369 | invalid: |
370 | pr_debug("invalid %s: type=%d cid=%u pcid=%u " |
371 | "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n" , |
372 | pptp_msg_name(msg), |
373 | msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, |
374 | ntohs(info->pns_call_id), ntohs(info->pac_call_id)); |
375 | return NF_ACCEPT; |
376 | } |
377 | |
378 | static int |
379 | pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff, |
380 | struct PptpControlHeader *ctlh, |
381 | union pptp_ctrl_union *pptpReq, |
382 | unsigned int reqlen, |
383 | struct nf_conn *ct, |
384 | enum ip_conntrack_info ctinfo) |
385 | { |
386 | struct nf_ct_pptp_master *info = nfct_help_data(ct); |
387 | const struct nf_nat_pptp_hook *hook; |
388 | u_int16_t msg; |
389 | __be16 cid = 0, pcid = 0; |
390 | |
391 | msg = ntohs(ctlh->messageType); |
392 | pr_debug("outbound control message %s\n" , pptp_msg_name(msg)); |
393 | |
394 | switch (msg) { |
395 | case PPTP_START_SESSION_REQUEST: |
396 | /* client requests for new control session */ |
397 | if (info->sstate != PPTP_SESSION_NONE) |
398 | goto invalid; |
399 | info->sstate = PPTP_SESSION_REQUESTED; |
400 | break; |
401 | |
402 | case PPTP_STOP_SESSION_REQUEST: |
403 | /* client requests end of control session */ |
404 | info->sstate = PPTP_SESSION_STOPREQ; |
405 | break; |
406 | |
407 | case PPTP_OUT_CALL_REQUEST: |
408 | /* client initiating connection to server */ |
409 | if (info->sstate != PPTP_SESSION_CONFIRMED) |
410 | goto invalid; |
411 | info->cstate = PPTP_CALL_OUT_REQ; |
412 | /* track PNS call id */ |
413 | cid = pptpReq->ocreq.callID; |
414 | pr_debug("%s, CID=%X\n" , pptp_msg_name(msg), ntohs(cid)); |
415 | info->pns_call_id = cid; |
416 | break; |
417 | |
418 | case PPTP_IN_CALL_REPLY: |
419 | /* client answers incoming call */ |
420 | if (info->cstate != PPTP_CALL_IN_REQ && |
421 | info->cstate != PPTP_CALL_IN_REP) |
422 | goto invalid; |
423 | |
424 | cid = pptpReq->icack.callID; |
425 | pcid = pptpReq->icack.peersCallID; |
426 | if (info->pac_call_id != pcid) |
427 | goto invalid; |
428 | pr_debug("%s, CID=%X PCID=%X\n" , pptp_msg_name(msg), |
429 | ntohs(cid), ntohs(pcid)); |
430 | |
431 | if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) { |
432 | /* part two of the three-way handshake */ |
433 | info->cstate = PPTP_CALL_IN_REP; |
434 | info->pns_call_id = cid; |
435 | } else |
436 | info->cstate = PPTP_CALL_NONE; |
437 | break; |
438 | |
439 | case PPTP_CALL_CLEAR_REQUEST: |
440 | /* client requests hangup of call */ |
441 | if (info->sstate != PPTP_SESSION_CONFIRMED) |
442 | goto invalid; |
443 | /* FUTURE: iterate over all calls and check if |
444 | * call ID is valid. We don't do this without newnat, |
445 | * because we only know about last call */ |
446 | info->cstate = PPTP_CALL_CLEAR_REQ; |
447 | break; |
448 | |
449 | case PPTP_SET_LINK_INFO: |
450 | case PPTP_ECHO_REQUEST: |
451 | case PPTP_ECHO_REPLY: |
452 | /* I don't have to explain these ;) */ |
453 | break; |
454 | |
455 | default: |
456 | goto invalid; |
457 | } |
458 | |
459 | hook = rcu_dereference(nf_nat_pptp_hook); |
460 | if (hook && ct->status & IPS_NAT_MASK) |
461 | return hook->outbound(skb, ct, ctinfo, protoff, ctlh, pptpReq); |
462 | return NF_ACCEPT; |
463 | |
464 | invalid: |
465 | pr_debug("invalid %s: type=%d cid=%u pcid=%u " |
466 | "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n" , |
467 | pptp_msg_name(msg), |
468 | msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, |
469 | ntohs(info->pns_call_id), ntohs(info->pac_call_id)); |
470 | return NF_ACCEPT; |
471 | } |
472 | |
473 | static const unsigned int pptp_msg_size[] = { |
474 | [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest), |
475 | [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply), |
476 | [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest), |
477 | [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply), |
478 | [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest), |
479 | [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply), |
480 | [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest), |
481 | [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply), |
482 | [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected), |
483 | [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest), |
484 | [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify), |
485 | [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify), |
486 | [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo), |
487 | }; |
488 | |
489 | /* track caller id inside control connection, call expect_related */ |
490 | static int |
491 | conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff, |
492 | struct nf_conn *ct, enum ip_conntrack_info ctinfo) |
493 | |
494 | { |
495 | int dir = CTINFO2DIR(ctinfo); |
496 | const struct nf_ct_pptp_master *info = nfct_help_data(ct); |
497 | const struct tcphdr *tcph; |
498 | struct tcphdr _tcph; |
499 | const struct pptp_pkt_hdr *pptph; |
500 | struct pptp_pkt_hdr _pptph; |
501 | struct PptpControlHeader _ctlh, *ctlh; |
502 | union pptp_ctrl_union _pptpReq, *pptpReq; |
503 | unsigned int tcplen = skb->len - protoff; |
504 | unsigned int datalen, reqlen, nexthdr_off; |
505 | int oldsstate, oldcstate; |
506 | int ret; |
507 | u_int16_t msg; |
508 | |
509 | #if IS_ENABLED(CONFIG_NF_NAT) |
510 | if (!nf_ct_is_confirmed(ct) && (ct->status & IPS_NAT_MASK)) { |
511 | struct nf_conn_nat *nat = nf_ct_ext_find(ct, id: NF_CT_EXT_NAT); |
512 | |
513 | if (!nat && !nf_ct_ext_add(ct, id: NF_CT_EXT_NAT, GFP_ATOMIC)) |
514 | return NF_DROP; |
515 | } |
516 | #endif |
517 | /* don't do any tracking before tcp handshake complete */ |
518 | if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) |
519 | return NF_ACCEPT; |
520 | |
521 | nexthdr_off = protoff; |
522 | tcph = skb_header_pointer(skb, offset: nexthdr_off, len: sizeof(_tcph), buffer: &_tcph); |
523 | if (!tcph) |
524 | return NF_ACCEPT; |
525 | |
526 | nexthdr_off += tcph->doff * 4; |
527 | datalen = tcplen - tcph->doff * 4; |
528 | |
529 | pptph = skb_header_pointer(skb, offset: nexthdr_off, len: sizeof(_pptph), buffer: &_pptph); |
530 | if (!pptph) { |
531 | pr_debug("no full PPTP header, can't track\n" ); |
532 | return NF_ACCEPT; |
533 | } |
534 | nexthdr_off += sizeof(_pptph); |
535 | datalen -= sizeof(_pptph); |
536 | |
537 | /* if it's not a control message we can't do anything with it */ |
538 | if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL || |
539 | ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) { |
540 | pr_debug("not a control packet\n" ); |
541 | return NF_ACCEPT; |
542 | } |
543 | |
544 | ctlh = skb_header_pointer(skb, offset: nexthdr_off, len: sizeof(_ctlh), buffer: &_ctlh); |
545 | if (!ctlh) |
546 | return NF_ACCEPT; |
547 | nexthdr_off += sizeof(_ctlh); |
548 | datalen -= sizeof(_ctlh); |
549 | |
550 | reqlen = datalen; |
551 | msg = ntohs(ctlh->messageType); |
552 | if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg]) |
553 | return NF_ACCEPT; |
554 | if (reqlen > sizeof(*pptpReq)) |
555 | reqlen = sizeof(*pptpReq); |
556 | |
557 | pptpReq = skb_header_pointer(skb, offset: nexthdr_off, len: reqlen, buffer: &_pptpReq); |
558 | if (!pptpReq) |
559 | return NF_ACCEPT; |
560 | |
561 | oldsstate = info->sstate; |
562 | oldcstate = info->cstate; |
563 | |
564 | spin_lock_bh(lock: &nf_pptp_lock); |
565 | |
566 | /* FIXME: We just blindly assume that the control connection is always |
567 | * established from PNS->PAC. However, RFC makes no guarantee */ |
568 | if (dir == IP_CT_DIR_ORIGINAL) |
569 | /* client -> server (PNS -> PAC) */ |
570 | ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, |
571 | ctinfo); |
572 | else |
573 | /* server -> client (PAC -> PNS) */ |
574 | ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, |
575 | ctinfo); |
576 | pr_debug("sstate: %d->%d, cstate: %d->%d\n" , |
577 | oldsstate, info->sstate, oldcstate, info->cstate); |
578 | spin_unlock_bh(lock: &nf_pptp_lock); |
579 | |
580 | return ret; |
581 | } |
582 | |
583 | static const struct nf_conntrack_expect_policy pptp_exp_policy = { |
584 | .max_expected = 2, |
585 | .timeout = 5 * 60, |
586 | }; |
587 | |
588 | /* control protocol helper */ |
589 | static struct nf_conntrack_helper pptp __read_mostly = { |
590 | .name = "pptp" , |
591 | .me = THIS_MODULE, |
592 | .tuple.src.l3num = AF_INET, |
593 | .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT), |
594 | .tuple.dst.protonum = IPPROTO_TCP, |
595 | .help = conntrack_pptp_help, |
596 | .destroy = pptp_destroy_siblings, |
597 | .expect_policy = &pptp_exp_policy, |
598 | }; |
599 | |
600 | static int __init nf_conntrack_pptp_init(void) |
601 | { |
602 | NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_pptp_master)); |
603 | |
604 | return nf_conntrack_helper_register(&pptp); |
605 | } |
606 | |
607 | static void __exit nf_conntrack_pptp_fini(void) |
608 | { |
609 | nf_conntrack_helper_unregister(&pptp); |
610 | } |
611 | |
612 | module_init(nf_conntrack_pptp_init); |
613 | module_exit(nf_conntrack_pptp_fini); |
614 | |