1 /* 2 * Connection tracking support for PPTP (Point to Point Tunneling Protocol). 3 * PPTP is a a protocol for creating virtual private networks. 4 * It is a specification defined by Microsoft and some vendors 5 * working with Microsoft. PPTP is built on top of a modified 6 * version of the Internet Generic Routing Encapsulation Protocol. 7 * GRE is defined in RFC 1701 and RFC 1702. Documentation of 8 * PPTP can be found in RFC 2637 9 * 10 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org> 11 * 12 * Development of this code funded by Astaro AG (http://www.astaro.com/) 13 * 14 * Limitations: 15 * - We blindly assume that control connections are always 16 * established in PNS->PAC direction. This is a violation 17 * of RFFC2673 18 * - We can only support one single call within each session 19 * TODO: 20 * - testing of incoming PPTP calls 21 */ 22 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 <net/netfilter/nf_conntrack_zones.h> 32 #include <linux/netfilter/nf_conntrack_proto_gre.h> 33 #include <linux/netfilter/nf_conntrack_pptp.h> 34 35 #define NF_CT_PPTP_VERSION "3.1" 36 37 MODULE_LICENSE("GPL"); 38 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>"); 39 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP"); 40 MODULE_ALIAS("ip_conntrack_pptp"); 41 MODULE_ALIAS_NFCT_HELPER("pptp"); 42 43 static DEFINE_SPINLOCK(nf_pptp_lock); 44 45 int 46 (*nf_nat_pptp_hook_outbound)(struct sk_buff *skb, 47 struct nf_conn *ct, enum ip_conntrack_info ctinfo, 48 struct PptpControlHeader *ctlh, 49 union pptp_ctrl_union *pptpReq) __read_mostly; 50 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound); 51 52 int 53 (*nf_nat_pptp_hook_inbound)(struct sk_buff *skb, 54 struct nf_conn *ct, enum ip_conntrack_info ctinfo, 55 struct PptpControlHeader *ctlh, 56 union pptp_ctrl_union *pptpReq) __read_mostly; 57 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound); 58 59 void 60 (*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig, 61 struct nf_conntrack_expect *expect_reply) 62 __read_mostly; 63 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre); 64 65 void 66 (*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct, 67 struct nf_conntrack_expect *exp) __read_mostly; 68 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn); 69 70 #if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG) 71 /* PptpControlMessageType names */ 72 const char *const pptp_msg_name[] = { 73 "UNKNOWN_MESSAGE", 74 "START_SESSION_REQUEST", 75 "START_SESSION_REPLY", 76 "STOP_SESSION_REQUEST", 77 "STOP_SESSION_REPLY", 78 "ECHO_REQUEST", 79 "ECHO_REPLY", 80 "OUT_CALL_REQUEST", 81 "OUT_CALL_REPLY", 82 "IN_CALL_REQUEST", 83 "IN_CALL_REPLY", 84 "IN_CALL_CONNECT", 85 "CALL_CLEAR_REQUEST", 86 "CALL_DISCONNECT_NOTIFY", 87 "WAN_ERROR_NOTIFY", 88 "SET_LINK_INFO" 89 }; 90 EXPORT_SYMBOL(pptp_msg_name); 91 #endif 92 93 #define SECS *HZ 94 #define MINS * 60 SECS 95 #define HOURS * 60 MINS 96 97 #define PPTP_GRE_TIMEOUT (10 MINS) 98 #define PPTP_GRE_STREAM_TIMEOUT (5 HOURS) 99 100 static void pptp_expectfn(struct nf_conn *ct, 101 struct nf_conntrack_expect *exp) 102 { 103 struct net *net = nf_ct_net(ct); 104 typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn; 105 pr_debug("increasing timeouts\n"); 106 107 /* increase timeout of GRE data channel conntrack entry */ 108 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT; 109 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT; 110 111 /* Can you see how rusty this code is, compared with the pre-2.6.11 112 * one? That's what happened to my shiny newnat of 2002 ;( -HW */ 113 114 rcu_read_lock(); 115 nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn); 116 if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK) 117 nf_nat_pptp_expectfn(ct, exp); 118 else { 119 struct nf_conntrack_tuple inv_t; 120 struct nf_conntrack_expect *exp_other; 121 122 /* obviously this tuple inversion only works until you do NAT */ 123 nf_ct_invert_tuplepr(&inv_t, &exp->tuple); 124 pr_debug("trying to unexpect other dir: "); 125 nf_ct_dump_tuple(&inv_t); 126 127 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t); 128 if (exp_other) { 129 /* delete other expectation. */ 130 pr_debug("found\n"); 131 nf_ct_unexpect_related(exp_other); 132 nf_ct_expect_put(exp_other); 133 } else { 134 pr_debug("not found\n"); 135 } 136 } 137 rcu_read_unlock(); 138 } 139 140 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct, 141 const struct nf_conntrack_tuple *t) 142 { 143 const struct nf_conntrack_tuple_hash *h; 144 struct nf_conntrack_expect *exp; 145 struct nf_conn *sibling; 146 u16 zone = nf_ct_zone(ct); 147 148 pr_debug("trying to timeout ct or exp for tuple "); 149 nf_ct_dump_tuple(t); 150 151 h = nf_conntrack_find_get(net, zone, t); 152 if (h) { 153 sibling = nf_ct_tuplehash_to_ctrack(h); 154 pr_debug("setting timeout of conntrack %p to 0\n", sibling); 155 sibling->proto.gre.timeout = 0; 156 sibling->proto.gre.stream_timeout = 0; 157 if (del_timer(&sibling->timeout)) 158 sibling->timeout.function((unsigned long)sibling); 159 nf_ct_put(sibling); 160 return 1; 161 } else { 162 exp = nf_ct_expect_find_get(net, zone, t); 163 if (exp) { 164 pr_debug("unexpect_related of expect %p\n", exp); 165 nf_ct_unexpect_related(exp); 166 nf_ct_expect_put(exp); 167 return 1; 168 } 169 } 170 return 0; 171 } 172 173 /* timeout GRE data connections */ 174 static void pptp_destroy_siblings(struct nf_conn *ct) 175 { 176 struct net *net = nf_ct_net(ct); 177 const struct nf_conn_help *help = nfct_help(ct); 178 struct nf_conntrack_tuple t; 179 180 nf_ct_gre_keymap_destroy(ct); 181 182 /* try original (pns->pac) tuple */ 183 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t)); 184 t.dst.protonum = IPPROTO_GRE; 185 t.src.u.gre.key = help->help.ct_pptp_info.pns_call_id; 186 t.dst.u.gre.key = help->help.ct_pptp_info.pac_call_id; 187 if (!destroy_sibling_or_exp(net, ct, &t)) 188 pr_debug("failed to timeout original pns->pac ct/exp\n"); 189 190 /* try reply (pac->pns) tuple */ 191 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t)); 192 t.dst.protonum = IPPROTO_GRE; 193 t.src.u.gre.key = help->help.ct_pptp_info.pac_call_id; 194 t.dst.u.gre.key = help->help.ct_pptp_info.pns_call_id; 195 if (!destroy_sibling_or_exp(net, ct, &t)) 196 pr_debug("failed to timeout reply pac->pns ct/exp\n"); 197 } 198 199 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */ 200 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid) 201 { 202 struct nf_conntrack_expect *exp_orig, *exp_reply; 203 enum ip_conntrack_dir dir; 204 int ret = 1; 205 typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre; 206 207 exp_orig = nf_ct_expect_alloc(ct); 208 if (exp_orig == NULL) 209 goto out; 210 211 exp_reply = nf_ct_expect_alloc(ct); 212 if (exp_reply == NULL) 213 goto out_put_orig; 214 215 /* original direction, PNS->PAC */ 216 dir = IP_CT_DIR_ORIGINAL; 217 nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT, 218 nf_ct_l3num(ct), 219 &ct->tuplehash[dir].tuple.src.u3, 220 &ct->tuplehash[dir].tuple.dst.u3, 221 IPPROTO_GRE, &peer_callid, &callid); 222 exp_orig->expectfn = pptp_expectfn; 223 224 /* reply direction, PAC->PNS */ 225 dir = IP_CT_DIR_REPLY; 226 nf_ct_expect_init(exp_reply, 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, &callid, &peer_callid); 231 exp_reply->expectfn = pptp_expectfn; 232 233 nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre); 234 if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK) 235 nf_nat_pptp_exp_gre(exp_orig, exp_reply); 236 if (nf_ct_expect_related(exp_orig) != 0) 237 goto out_put_both; 238 if (nf_ct_expect_related(exp_reply) != 0) 239 goto out_unexpect_orig; 240 241 /* Add GRE keymap entries */ 242 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0) 243 goto out_unexpect_both; 244 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) { 245 nf_ct_gre_keymap_destroy(ct); 246 goto out_unexpect_both; 247 } 248 ret = 0; 249 250 out_put_both: 251 nf_ct_expect_put(exp_reply); 252 out_put_orig: 253 nf_ct_expect_put(exp_orig); 254 out: 255 return ret; 256 257 out_unexpect_both: 258 nf_ct_unexpect_related(exp_reply); 259 out_unexpect_orig: 260 nf_ct_unexpect_related(exp_orig); 261 goto out_put_both; 262 } 263 264 static inline int 265 pptp_inbound_pkt(struct sk_buff *skb, 266 struct PptpControlHeader *ctlh, 267 union pptp_ctrl_union *pptpReq, 268 unsigned int reqlen, 269 struct nf_conn *ct, 270 enum ip_conntrack_info ctinfo) 271 { 272 struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info; 273 u_int16_t msg; 274 __be16 cid = 0, pcid = 0; 275 typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound; 276 277 msg = ntohs(ctlh->messageType); 278 pr_debug("inbound control message %s\n", pptp_msg_name[msg]); 279 280 switch (msg) { 281 case PPTP_START_SESSION_REPLY: 282 /* server confirms new control session */ 283 if (info->sstate < PPTP_SESSION_REQUESTED) 284 goto invalid; 285 if (pptpReq->srep.resultCode == PPTP_START_OK) 286 info->sstate = PPTP_SESSION_CONFIRMED; 287 else 288 info->sstate = PPTP_SESSION_ERROR; 289 break; 290 291 case PPTP_STOP_SESSION_REPLY: 292 /* server confirms end of control session */ 293 if (info->sstate > PPTP_SESSION_STOPREQ) 294 goto invalid; 295 if (pptpReq->strep.resultCode == PPTP_STOP_OK) 296 info->sstate = PPTP_SESSION_NONE; 297 else 298 info->sstate = PPTP_SESSION_ERROR; 299 break; 300 301 case PPTP_OUT_CALL_REPLY: 302 /* server accepted call, we now expect GRE frames */ 303 if (info->sstate != PPTP_SESSION_CONFIRMED) 304 goto invalid; 305 if (info->cstate != PPTP_CALL_OUT_REQ && 306 info->cstate != PPTP_CALL_OUT_CONF) 307 goto invalid; 308 309 cid = pptpReq->ocack.callID; 310 pcid = pptpReq->ocack.peersCallID; 311 if (info->pns_call_id != pcid) 312 goto invalid; 313 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg], 314 ntohs(cid), ntohs(pcid)); 315 316 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) { 317 info->cstate = PPTP_CALL_OUT_CONF; 318 info->pac_call_id = cid; 319 exp_gre(ct, cid, pcid); 320 } else 321 info->cstate = PPTP_CALL_NONE; 322 break; 323 324 case PPTP_IN_CALL_REQUEST: 325 /* server tells us about incoming call request */ 326 if (info->sstate != PPTP_SESSION_CONFIRMED) 327 goto invalid; 328 329 cid = pptpReq->icreq.callID; 330 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 331 info->cstate = PPTP_CALL_IN_REQ; 332 info->pac_call_id = cid; 333 break; 334 335 case PPTP_IN_CALL_CONNECT: 336 /* server tells us about incoming call established */ 337 if (info->sstate != PPTP_SESSION_CONFIRMED) 338 goto invalid; 339 if (info->cstate != PPTP_CALL_IN_REP && 340 info->cstate != PPTP_CALL_IN_CONF) 341 goto invalid; 342 343 pcid = pptpReq->iccon.peersCallID; 344 cid = info->pac_call_id; 345 346 if (info->pns_call_id != pcid) 347 goto invalid; 348 349 pr_debug("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid)); 350 info->cstate = PPTP_CALL_IN_CONF; 351 352 /* we expect a GRE connection from PAC to PNS */ 353 exp_gre(ct, cid, pcid); 354 break; 355 356 case PPTP_CALL_DISCONNECT_NOTIFY: 357 /* server confirms disconnect */ 358 cid = pptpReq->disc.callID; 359 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 360 info->cstate = PPTP_CALL_NONE; 361 362 /* untrack this call id, unexpect GRE packets */ 363 pptp_destroy_siblings(ct); 364 break; 365 366 case PPTP_WAN_ERROR_NOTIFY: 367 case PPTP_ECHO_REQUEST: 368 case PPTP_ECHO_REPLY: 369 /* I don't have to explain these ;) */ 370 break; 371 372 default: 373 goto invalid; 374 } 375 376 nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound); 377 if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK) 378 return nf_nat_pptp_inbound(skb, ct, ctinfo, ctlh, pptpReq); 379 return NF_ACCEPT; 380 381 invalid: 382 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 383 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 384 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0], 385 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 386 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 387 return NF_ACCEPT; 388 } 389 390 static inline int 391 pptp_outbound_pkt(struct sk_buff *skb, 392 struct PptpControlHeader *ctlh, 393 union pptp_ctrl_union *pptpReq, 394 unsigned int reqlen, 395 struct nf_conn *ct, 396 enum ip_conntrack_info ctinfo) 397 { 398 struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info; 399 u_int16_t msg; 400 __be16 cid = 0, pcid = 0; 401 typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound; 402 403 msg = ntohs(ctlh->messageType); 404 pr_debug("outbound control message %s\n", pptp_msg_name[msg]); 405 406 switch (msg) { 407 case PPTP_START_SESSION_REQUEST: 408 /* client requests for new control session */ 409 if (info->sstate != PPTP_SESSION_NONE) 410 goto invalid; 411 info->sstate = PPTP_SESSION_REQUESTED; 412 break; 413 414 case PPTP_STOP_SESSION_REQUEST: 415 /* client requests end of control session */ 416 info->sstate = PPTP_SESSION_STOPREQ; 417 break; 418 419 case PPTP_OUT_CALL_REQUEST: 420 /* client initiating connection to server */ 421 if (info->sstate != PPTP_SESSION_CONFIRMED) 422 goto invalid; 423 info->cstate = PPTP_CALL_OUT_REQ; 424 /* track PNS call id */ 425 cid = pptpReq->ocreq.callID; 426 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 427 info->pns_call_id = cid; 428 break; 429 430 case PPTP_IN_CALL_REPLY: 431 /* client answers incoming call */ 432 if (info->cstate != PPTP_CALL_IN_REQ && 433 info->cstate != PPTP_CALL_IN_REP) 434 goto invalid; 435 436 cid = pptpReq->icack.callID; 437 pcid = pptpReq->icack.peersCallID; 438 if (info->pac_call_id != pcid) 439 goto invalid; 440 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg], 441 ntohs(cid), ntohs(pcid)); 442 443 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) { 444 /* part two of the three-way handshake */ 445 info->cstate = PPTP_CALL_IN_REP; 446 info->pns_call_id = cid; 447 } else 448 info->cstate = PPTP_CALL_NONE; 449 break; 450 451 case PPTP_CALL_CLEAR_REQUEST: 452 /* client requests hangup of call */ 453 if (info->sstate != PPTP_SESSION_CONFIRMED) 454 goto invalid; 455 /* FUTURE: iterate over all calls and check if 456 * call ID is valid. We don't do this without newnat, 457 * because we only know about last call */ 458 info->cstate = PPTP_CALL_CLEAR_REQ; 459 break; 460 461 case PPTP_SET_LINK_INFO: 462 case PPTP_ECHO_REQUEST: 463 case PPTP_ECHO_REPLY: 464 /* I don't have to explain these ;) */ 465 break; 466 467 default: 468 goto invalid; 469 } 470 471 nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound); 472 if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK) 473 return nf_nat_pptp_outbound(skb, ct, ctinfo, ctlh, pptpReq); 474 return NF_ACCEPT; 475 476 invalid: 477 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 478 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 479 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0], 480 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 481 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 482 return NF_ACCEPT; 483 } 484 485 static const unsigned int pptp_msg_size[] = { 486 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest), 487 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply), 488 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest), 489 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply), 490 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest), 491 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply), 492 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest), 493 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply), 494 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected), 495 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest), 496 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify), 497 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify), 498 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo), 499 }; 500 501 /* track caller id inside control connection, call expect_related */ 502 static int 503 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff, 504 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 505 506 { 507 int dir = CTINFO2DIR(ctinfo); 508 const struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info; 509 const struct tcphdr *tcph; 510 struct tcphdr _tcph; 511 const struct pptp_pkt_hdr *pptph; 512 struct pptp_pkt_hdr _pptph; 513 struct PptpControlHeader _ctlh, *ctlh; 514 union pptp_ctrl_union _pptpReq, *pptpReq; 515 unsigned int tcplen = skb->len - protoff; 516 unsigned int datalen, reqlen, nexthdr_off; 517 int oldsstate, oldcstate; 518 int ret; 519 u_int16_t msg; 520 521 /* don't do any tracking before tcp handshake complete */ 522 if (ctinfo != IP_CT_ESTABLISHED && 523 ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) 524 return NF_ACCEPT; 525 526 nexthdr_off = protoff; 527 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph); 528 BUG_ON(!tcph); 529 nexthdr_off += tcph->doff * 4; 530 datalen = tcplen - tcph->doff * 4; 531 532 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph); 533 if (!pptph) { 534 pr_debug("no full PPTP header, can't track\n"); 535 return NF_ACCEPT; 536 } 537 nexthdr_off += sizeof(_pptph); 538 datalen -= sizeof(_pptph); 539 540 /* if it's not a control message we can't do anything with it */ 541 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL || 542 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) { 543 pr_debug("not a control packet\n"); 544 return NF_ACCEPT; 545 } 546 547 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh); 548 if (!ctlh) 549 return NF_ACCEPT; 550 nexthdr_off += sizeof(_ctlh); 551 datalen -= sizeof(_ctlh); 552 553 reqlen = datalen; 554 msg = ntohs(ctlh->messageType); 555 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg]) 556 return NF_ACCEPT; 557 if (reqlen > sizeof(*pptpReq)) 558 reqlen = sizeof(*pptpReq); 559 560 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq); 561 if (!pptpReq) 562 return NF_ACCEPT; 563 564 oldsstate = info->sstate; 565 oldcstate = info->cstate; 566 567 spin_lock_bh(&nf_pptp_lock); 568 569 /* FIXME: We just blindly assume that the control connection is always 570 * established from PNS->PAC. However, RFC makes no guarantee */ 571 if (dir == IP_CT_DIR_ORIGINAL) 572 /* client -> server (PNS -> PAC) */ 573 ret = pptp_outbound_pkt(skb, ctlh, pptpReq, reqlen, ct, 574 ctinfo); 575 else 576 /* server -> client (PAC -> PNS) */ 577 ret = pptp_inbound_pkt(skb, ctlh, pptpReq, reqlen, ct, 578 ctinfo); 579 pr_debug("sstate: %d->%d, cstate: %d->%d\n", 580 oldsstate, info->sstate, oldcstate, info->cstate); 581 spin_unlock_bh(&nf_pptp_lock); 582 583 return ret; 584 } 585 586 static const struct nf_conntrack_expect_policy pptp_exp_policy = { 587 .max_expected = 2, 588 .timeout = 5 * 60, 589 }; 590 591 /* control protocol helper */ 592 static struct nf_conntrack_helper pptp __read_mostly = { 593 .name = "pptp", 594 .me = THIS_MODULE, 595 .tuple.src.l3num = AF_INET, 596 .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT), 597 .tuple.dst.protonum = IPPROTO_TCP, 598 .help = conntrack_pptp_help, 599 .destroy = pptp_destroy_siblings, 600 .expect_policy = &pptp_exp_policy, 601 }; 602 603 static void nf_conntrack_pptp_net_exit(struct net *net) 604 { 605 nf_ct_gre_keymap_flush(net); 606 } 607 608 static struct pernet_operations nf_conntrack_pptp_net_ops = { 609 .exit = nf_conntrack_pptp_net_exit, 610 }; 611 612 static int __init nf_conntrack_pptp_init(void) 613 { 614 int rv; 615 616 rv = nf_conntrack_helper_register(&pptp); 617 if (rv < 0) 618 return rv; 619 rv = register_pernet_subsys(&nf_conntrack_pptp_net_ops); 620 if (rv < 0) 621 nf_conntrack_helper_unregister(&pptp); 622 return rv; 623 } 624 625 static void __exit nf_conntrack_pptp_fini(void) 626 { 627 nf_conntrack_helper_unregister(&pptp); 628 unregister_pernet_subsys(&nf_conntrack_pptp_net_ops); 629 } 630 631 module_init(nf_conntrack_pptp_init); 632 module_exit(nf_conntrack_pptp_fini); 633